SEMINARIO INTERNACIONAL SOBRE EL USO,

TRATAMIENTO Y GESTION DEL VERDE URBANO INTERNATIONAL SEMINAR ON USE, HANDLING AND MANAGEMENT

OF URBAN GREEN AREAS

SEMINAIRE INTERNATIONAL SUR L'EMPLOI, TRAITEMENT

ET GESTION DU VERT URBAIN

UNESCO

Composición del Comité Español del Programa M A B (El hombre y la biosfera) de la U N E S C O (diciembre de 1988)

D . Tomás Azcárate y Bang Presidente

D . Luis Maestre Muftiz Vicepresidente primero

D . Francisco García Novo Vicepresidente encargado de Proyectos de Investigación

D . Ignaci Castelló i Vidal Vicepresidente para Reservas de Biosfera

D . Borja Cardelús Muñoz-Seca Vicepresidente para Educación, Información y Publicaciones

D . Javier Castroviejo Bolívar Vicepresidente para la Cooperación Internacional

D . Antonio López Lillo Secretario General

D . R a m ó n Floch i Guillen Secretario General

Dña . Cristina Herrero Molino Secretaria Ejecutiva

Vocales D . José Luis Aboal García Tufión D . Enrique Balcells Rocamora D . Josep María Camarasa Castillo D . Emilio Fernández-Galiano D . Fernando Fuentes Bodelón D . Jesús Garzón Heydt D . José María Gaseó Montes D . Fernando González Bernáldez D . José Miguel González Hernández D . Jaime Montaner Roselló D . Cosme Morillo Fernández D . José Manuel Naredo Pérez D . Angel Ramos Fernández D . Felipe Ruza Tarrío Dña . Concha Sáenz Lain D . Pedro Salvador Palomo D . Jaime Terradas Serra D . Manuel Valenzuela Rubio D . Arturo Valls Medina

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P R O L O G O

Dentro del Programa M A B , el campo de acción n ú m . 11, «Aspectos ecológicos de los sistemas urbanos», viene adquiriendo una gran relevancia. En esta línea, el Comité Español Programa M A B está apoyando un proyecto piloto de diseño y actividades de información, educación e investigación sobre el medio urbano de Barcelona, en cuyo Centro del Medio Urbano, perteneciente al Ayuntamiento de dicha ciudad, se está desarrollando una gran labor sobre el «Verde Urbano» en relación con la problemática de la vegetación ciudadana.

E n las sesiones del Comité de Coordinación del Programa M A B , celebradas en París del 3 al 8 de diciembre de 1984, se acordó, dentro de la temática de los sistemas urbanos, llamar la atención sobre los estudios relacionados con la gestión de los espacios verdes urbanos y con el análisis de las necesidades humanas en espacios verdes.

Ante esta coyuntura, no cabía ninguna duda de la oportunidad de establecer una reunión entre expertos en la materia para debatir esa problemática. El Comité Español del Programa M A B y el Centro del Medio Urbano decidieron organizar un Seminario Inter­nacional sobre «Uso, tratamiento y gestión del verde urbano», y ahora, la publicación que presentamos recoge todo lo tratado en dicho Seminario, así como las conclusiones que se establecieron por todos los asistentes, gran parte de ellos expertos nacionales y extranjeros en los temas de espacios verdes. \

Ante el éxito obtenido, el Secretariado Internacional del Programa M A B ha conside­rado este Seminario como punto de partida para seguir avanzando en el problema de los espacios verdes urbanos mediante otras reuniones específicas. El Comité Español del Pro­grama M A B puede servir de coordinador de los estudios internacionales que se llevan a cabo sobre el verde urbano y que presentan una gran importancia en las ciudades modernas.

EMILIO FERNANDEZ GALIANO Presidente del Comité Español del Programa M A B

21 de abril de 1986

PROGRAMA

21 de abril de 1986

10:00 horas Apertura a cargo del teniente de alcalde del Ayuntamiento de Barcelona y del presidente del Comité M A B España. Sesión I. El verde urbano: tratamiento y gestión (1).

14:30 Sesión II. Arbolado viario y zonas verdes urbanas (trabajo de campo).

22 de abril de 1986

9:30 horas Sesión III. El verde urbano: tratamiento y gestión (2).

14:30 horas Sesión IV. Parques y jardines urbanos (trabajo de campo).

23 de abril de 1986

9:30 horas Sesión V . Estrategia y filosofía de implantación del verde urbano.

24 de abril de 1986

9:30 horas Sesión VI. Comentarios a la exhibición de carteles y bibliografía.

11:00 Sesión VII. Conclusiones y propuestas.

12:15 horas Clausura a cargo del regidor de Sanidad y Medio Ambiente del Ayuntamiento de Barcelona.

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O R G A N I Z A C I Ó N

Presidencia

Prof. Dr. Emilio Fernández Galiano. Presidente del Comité Español del Programa M A B .

Coordinación

Dr. R a m ó n Folch. Coordinador de Publicaciones y Cooperación Internacional al C . E . del P . M A B .

Dr. John Celecia. Secretariado Internacional del Programa M A B .

Logística

D . José Carrillo. D . Pau Rodríguez. D . Ricard Alsina.

Servicio de Parques y Jardines y Centro del Medio Urbano. Ayuntamiento de Barcelona.

Relación de sesiones

Dr. Antonio López Lillo Secretario del Comité Español del Programa M A B . Jefe del Servicio del Medio Natu­ral de la Comunidad de Madrid.

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R E L A C I Ó N D E PARTICIPANTES

Ponentes

Dr. George Barker. Nature Conservancy Council., Peterbourgh PEÍ 1 U A (Gran Bretaña). Dra. Griselda Benítez. Instituto de Ecología, A . C . Delegación Miguel Hidalgo, 11.800-

México D . F . (México). Prof. Dr. Attila Borhidi. Institute of Ecology and Botany. Hungarian Academy of Scien­

ces H-2163. Vacratot (Hungría). Dr. José Carrillo. Servicio Municipal de Parques y Jardines, Ayuntamiento de Barcelona.

Avda. Marqués de Comillas, s/n. (Montjuich). 08004-Barcelona (España). Dr. Tjeerd Deelstra. Office of Research in Ecology and Planning. Delft University of

Technology. Berlageweg, 1. 2628CR-Delft (Países Bajos). Prof. Dr . Fernando González Bernáldez. Departamento de Ecología. Facultad de Cien­

cias, C - X V . Universidad Autónoma de Madrid. 28049-Madrid (España). Dra. Rosa Greña. Planejamentos e Projetos Ltda. A v . Brig. Luis Antonio, 2493. 01401-

Säo Paulo (Brasil). Dr. Claude Leroy. Laboratoire d'Eco-Ethologie Humaine. Institut National Marcel

Rivière. La Verrière, 78320-Le Mesnil-Saint-Denis (Francia). Dr. Zvi Miller. International Federation of Landscape Architects. 14, Haitishbi. Haifa-

34527 (Israel). D . Salvador Rueda. Unidad Operativa de Gestión Ambiental. Ayuntamiento de Barce­

lona. Passeig de la Circumvallació, 1. 08003-Barcelona (España). Prof. Hilda Selem. Via Cassia, 240. 08191-Roma (Italia). Dr. David Smith. Department of Planning. City of Dayton. 101 West Third Street. Day-

ton. Ohio-45401 (EE U U ) .

Invitados y observadores

D . Josep Antoni Acebillo. Servicio de Proyectos Urbanos. Ayuntamiento de Barcelona. 08003-Barcelona (España).

Dr. Francisco Amores. Servicio de Parques y Jardines. Ayuntamiento de Sevilla. Sevilla (España).

Dr. Rafael Barnola. Servicio de Parques y Jardines. Ayuntamiento de Zaragoza. Zaragoza (España).

Prof. Dr . Horacio Capel. Facultad de Geografía e Historia. Universidad de Barcelona. 08028-Barcelona (España).

D . José Elias. Servicio de Parques y Jardines. Ayuntamiento de Sevilla. Sevilla (España). D . Albert García. Servicio de Parques y Jardines. Ayuntamiento de Hospitalet. Hospitalet

de Llobregat (España). Prof. Dr . Lucio Grinover. Facultade de Arquitectura e Urbanismo. Universidade de Sao

Paulo. Cidade Universitaria Armando de Salles Oliveira. Caixa Postal, 3225. Sao Paulo (Brasil).

D . José Luis López. Servicio de Parques y Jardines. Ayuntamiento de Alicante. Alicante (España).

Prof. Dr. Josep Muntanyola. Escuela Técnica Superior de Arquitectura. Universidad Poli­técnica de Cataluña. 08028-Barcelona (España).

D . Pedro Palacios. Servicio de Ordenación y Mejoras. Consejería de Agricultura y Gana­dería. Comunidad de Madrid. 28020-Madrid (España).

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D . Elias Pino. Sección de Parques y Jardines. Consejería de Agricultura y Ganadería. Comunidad de Madrid. 28020-Madrid (España).

Dr. Antonio Pou. Departamento de Ecología. Facultad de Ciencias. Universidad Autó­n o m a de Madrid. 28049-Madrid (España).

D . Santiago Romero. Servicio de Parques y Jardines. Ayuntamiento de Madrid. 28004-Madrid (España).

Dr. Pedro Salvador. Gran Vía Fernando el Católico, 67. 46008-Valencia (España). Prof. Dr. Jaume Terradas. Departamento de Biología de Organismos y Sistemas. Facultad

de Ciencias. Universidad Autónoma de Barcelona. Bellaterra, Barcelona (España).

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R E S U M E N

21 de abril Mañana

El Seminario fue inaugurado por el teniente de alcalde del Ayuntamiento de Barcelona, señor Serra, quien en unas breves palabras dio la bienvenida a los asistentes, expresó su satisfacción por la celebración del Seminario y deseó los mayores éxitos en el desarrollo de las sesiones.

A continuación, el presidente del Comité Español del Programa M A B , don Emilio Fernández Galiano, agradeció las palabras del teniente de alcalde, expresando su gratitud por la colaboración prestada a este Seminario, tanto por parte del Ayuntamiento como del Secretariado Internacional del Programa M A B ( U N E S C O ) en París, e hizo unas conside­raciones sobre la labor que desarrolla el Comité Español del Programa M A B . Igualmente, dio las gracias por la presencia de los ponentes internacionales de gran prestigio en el tema de áreas verdes urbanas, así como por la asistencia de los responsables españoles más importantes en la materia. Finalizó expresando su esperanza en que el trabajo que se realice en el Seminario sea útil para mejorar el planeamiento, uso y gestión de las futuras zonas verdes urbanas.

E n la sesión interviene el doctor John Celecia, del Secretariado Internacional del Pro­grama M A B , indicando que este Seminario se encuadra dentro del proyecto M A B 11 y es el primero que se aborda dentro de esta temática; en su intervención destaca los siguientes aspectos:

— El pensamiento ecológico en el diseño de zonas verdes urbanas ya es una realidad. — La importancia de la integración del hombre en la problemática de las zonas verdes

urbanas, teniendo en cuenta la demanda de la sociedad y la integración de los actores involucrados.

— La necesidad de considerar un enfoque interdisciplinario en la planificación de las zonas verdes urbanas, armonizando los enfoques metodológicos con visión de fu­turo.

— El estudio de alternativas para hacer las ciudades más autosuficientes, disminu­yendo su dependencia del entorno.

— La necesidad de aprovechar las experiencias que en este campo desarrolla el pro­yecto M A B 11 y profundizar en temas de investigación sobre las áreas verdes ur­banas.

— La búsqueda de sistemas que sensibilicen al público, como el establecimiento de programas educativos continuos y no esporádicos que aseguren la participación activa del público o la confección de una cartografía temática adecuada. '

— La importancia de considerar la ciudad c o m o un sistema abierto, siendo necesario tener en cuenta su entorno y su relación con el mismo.

El doctor R a m ó n Folch expone las líneas maestras del desarrollo del Seminario e indica los objetivos del mismo, haciendo hincapié en los siguientes aspectos: intenciones y finali­dad del Seminario, sentido histórico y biológico del verde urbano, beneficios cívicos del verde urbano y problemas del manejo del verde urbano. Destaca: la importancia de consi­derar la vegetación autóctona, teniendo m u y en cuenta la elección de especies en relación con los lugares que van a ocupar, las funciones que deben cumplir y su persistencia en el transcurso del tiempo. El verde urbano debe contemplarse c o m o una suma de funcionali­dades: ornamentales, de calidad de vida, psicosomáticas, microclimáticas, biológicas, etc., debiéndose dar importancia al valor añadido cultural, histórico, tradicional, etc., de las zonas verdes.

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El doctor Tjeerd Deelstra, de la Universidad de Tecnología de Delft (Países Bajos), expone su ponencia sobre «Estrategias locales, regionales y nacionales para la implantación del verde urbano», destacando los siguientes puntos:

— La importancia de integrar las diversas escalas al planificar las zonas verdes urba­nas, desarrollando una urbanización ecológica.

— La participación de arquitectos, planificadores, ecologistas e investigadores en la temática de las zonas verdes.

— L a necesidad de disponer de un inventario exhaustivo del medio natural para plani­ficar las áreas verdes, así c o m o de una cartografía temática adecuada.

— El interés de realizar una concentración desconcentrada, que huya de establecer grandes ciudades y llevar a cabo un sistema disperso.

— La importancia de llevar una gerencia ecológica de los parques públicos, desta­cando la sensibilidad y participación del público en este sentido.

— La búsqueda de un desarrollo integrado de la ciudad, junto con las calidades poten­ciales del paisaje.

— La realización de estudios de percepción a posteriori que sirvan para futuras pla­nificaciones.

El doctor José Carrillo de Albornoz, jefe del Servicio de Parques y Jardines del Ayunta­miento de Barcelona, expone su ponencia «características, uso y tratamiento del verde urbano». Indica los problemas concretos que tiene Barcelona en relación con sus zonas verdes, de índole física, urbanística, sociológica y económica, destacando clima favorable, aunque con heladas extemporáneas, sequía, suelos poco favorables, agua deficiente, espa­cio escaso y m u y utilizado y presupuestos cortos.

Tarde

Visita a los parques y jardines de Montjuich, con parada en el Castillo, donde, ante la vista panorámica de la ciudad, el senos Carrillo expuso la problemática de las zonas verdes de la ciudad, pasando después a visitar los jardines de Mosen Cinto Verdaguer y Costa i Llo­vera, donde se contemplaron las magníficas colecciones de plantas exóticas, destacando especialmente la espléndida colección de plantas crasas y suculentas.

E n esta visita los asistentes al Seminario pudieron intercambiar ideas prácticas sobre las zonas verdes visitadas.

22 de abril

Mañana

La profesora Hilda Selem, del Comité Italiano del Programa M A B , expuso la ponencia «Problemas y programas sobre el uso de las áreas verdes y educación: el caso de R o m a » , destacando los siguientes puntos:

— L a importancia de encontrar enlace entre edificios y zonas verdes, considerando el verde c o m o el subsistema primordial en el sistema urbano.

— La importancia de la combinación de los valores del patrimonio histórico y del natural.

— El ser h u m a n o y el monumento histórico son los elementos principales del verde urbano.

— E n muchos casos, la evolución histórica del espacio es imprescindible para mante­ner adecuadamente las zonas verdes urbanas y los elementos preexistentes (tesoros arqueológicos).

— El verde debe ser una esperanza para diseñar ciudades aptas para los seres h u m a ­nos, ya que debe considerarse c o m o un derecho de los ciudadanos.

— El creciente movimiento de los ciudadanos, así c o m o su cambio de vida hacen nece­saria la existencia de más zonas verdes.

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— Es preciso establecer puntos de encuentro para poder proporcionar las áreas que demanda el ciudadano.

— Los habitantes de la ciudad deben ser actores y no espectadores; el espacio debe ser la expresión de los ciudadanos y se debe convencer a los políticos en este sentido.

— La necesidad de crear nuevas estructuras competentes, incluyendo las de orden jurí­dico, para desarrollar nuevas estrategias en la temáttica del verde urbano.

El doctor David Smith, del Departamento de Planeamiento de la ciudad de Dayton (EE U U ) , disertó sobre los «Efectos del verde urbano sobre el microclima: el caso de D a y ­ton», destacando los siguientes aspectos:

— L a importancia del clima urbano, debiéndose considerar las múltiples variables que inciden en la mejora de la calidad de vida.

— La necesidad de estudiar el clima de la ciudad, preferentemente la temperatura, para diseñar una adecuada implantación de árboles.

— La realización de la medición de la cobertura arbórea para disminuir el efecto de la lluvia (escorrentía) y lograr un efecto regulador contra la erosión.

— La importancia de llevar a cabo un estudio de vientos para poder regular el micro-clima de la ciudad.

— El aumento del arbolado en la ciudad, de acuerdo con las condiciones climáticas, reduce el impacto de la urbanización a la vez que aumenta la concienciación de los ciudadanos por las zonas verdes.

— La importancia del inventario del arbolado urbano c o m o ayuda a nuevas planta­ciones, buscando la participación ciudadana en estas plantaciones.

— La importancia de la cartografía temática y de los modelos temáticos que contem­plen y cuantifiquen los fenómenos para su regulación.

— L a importancia de conocer el proceso natural c o m o ayuda a una mejor gestión de las zonas verdes de la ciudad.

— L a selvicultura urbana racional permite una mejor conservación y regulación de la energía.

— La adecuada distribución de áreas arboladas puede modificar el clima urbano. — La conveniencia de utilizar imágenes de satélite y aerofotogrametría. — L a necesidad de establecer programas flexibles que permitan su aplicación a otros

lugares y que se adapten a los cambios en las políticas. — L a gran ayuda que suponen los colaboradores voluntarios con vistas a la ejecución

de los programas, tanto en la aportación de datos c o m o en la transmisión de la in­formación.

— La selección de especies vegetales para situarlas de acuerdo con las diferentes condi­ciones climáticas de la ciudad.

— L a necesidad de una buena información pública sobre la contaminación, con fines disuasorios sobre el transporte privado.

— L a búsqueda de sistemas que permitan no cortar árboles c o m o mayor garantía de su conservación.

— El interés de distribuir plantas en vertical o sobre terrazas, balcones, ventanas, teja­dos, etcétera.

— La necesidad de contar con datos cuantificables y no trabajar con meras intui­ciones.

— L a armonía de enfoques conceptuales y metodológicos en la planificación y gestión, así c o m o establecer estudios comparativos en situaciones análogas.

El doctor Zvi Miller, presidente de la Federación'de Arquitectos Paisajistas, disertó sobre «Diseño y concepción de los espacios verdes urbanos», destacando de su intervención los siguientes puntos:

— L a importancia de los arquitectos paisajistas o técnicos similares para la planifica­ción de las áreas verdes urbanas.

— L a necesidad de conservar los entornos naturales de las áreas urbanas, haciéndolos accesibles a la ciudad.

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— La preocupación por el desarrollo de proyectos a gran escala, sin considerar ade­cuadamente los impactos sobre el medio natural.

— La necesidad de hacer una planificación compatible con los valores naturales. — La importancia de establecer sistemas educativos que ayuden a mantener las áreas

naturales.

El señor Salvador Rueda, de la Unidad Operativa de Gestión Ambiental del Ayuntamiento de Barcelona, expuso los «Problemas ambientales en el verde urbano de Barcelona», destacando:

— El desarrollo concéntrico de Barcelona. — El Plan Cerda, que fue generoso con el verde urbano. — El desarrollo de planes poco equilibrados. — El establecimiento de criterios que no han tenido en cuenta el ecosistema urbano. — La gran densidad de población, con la consiguiente degradación del medio. — La necesidad de planificar teniendo en cuenta los condicionantes físicos de la ciu­

dad. — La importancia de establecer estudios sobre la influencia de la contaminación en las

plantas. — L a importancia del Centro del Medio Urbano de Barcelona, que permite: dar a

conocer la ciudad; conocer y comprender a los ciudadanos; lograr la percepción de la ciudad por los ciudadanos; educar y responsabilizar a todos; punto de participa­ción ciudadana c o m o ayuda a las tomas de decisiones; elaboración y transmisión de información sobre la ciudad.

Tarde

Visita a las zonas verdes del templo de la Sagrada Familia, el Parque Güell y el parque de la Ciudadela, así c o m o a los nuevos espacios verdes en el área de Sans, para contrastar conceptos en áreas verdes urbanas.

23 de abril

Mañana

El profesor Attila Borhidi, del Instituto de Ecología y Botánica de la Academia Húngara de Ciencias, expuso la ponencia «Verde urbano, clima, contaminación y bioindicadores: el caso de Budapest», destacando los siguientes puntos:

— La importancia de disponer de diagramas higroclimáticos y temperaturas de la ciu­dad.

— La utilización de bioindicadores como ayuda a la planificación y gestión. — El estudio de las tendencias bioclimáticas. — La utilización de bioclimodiagramas de la ciudad en la planificación de las áreas

verdes. — La consideración de la exigencia ecológica de los árboles y la tendencia microclimá-

tica de la ciudad. — La importancia y necesidad de utilizar las especies autóctonas, ya que no se las

presta la atención adecuada. — La selección de especies vegetales de regiones ecológicas análogas, teniendo en

cuenta las condiciones de la ciudad. — La atención a los problemas de salinidad y de contaminación.

El profesor Fernando González Bernáldez, catedrático de Ecología de la Universidad Autónoma de Madrid, disertó sobre «La percepción del verde urbano y periurbano», des­tacando los siguientes aspectos:

— Los ciudadanos demandan una variedad de zonas verdes.

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— Las zonas verdes ejercen una terapia sobre los ciudadanos. — Las zonas verdes ejercen un efecto de relajamiento sobre los habitantes de la urbe. — La importancia de desarrollar estudios de percepción de las zonas verdes urbanas. — La tendencia a planificar zonas verdes, ignorando las apetencias de los ciudadanos. — La necesidad de encontrar procedimientos para minimizar los conflictos entre técni­

cas que inciden sobre el verde urbano.

La doctora Rosa Greña, del Comité Brasileño del Comité M A B , disertó sobre la «Percep­ción de las zonas verdes urbanas por parte de la población: el caso de Sao Paulo», resal­tando los siguientes aspectos:

— El proyecto de Plan General de Sao Paulo. — La importancia de la diagnosis de la vegetación, su relación con el entorno urbano

y la población. — El estudio del proceso de la vegetación c o m o factor importante en la calidad del

medio ambiente de la ciudad. — La importancia de buscar sistemas que permitan a los ciudadanos conocer la vege­

tación y sus valores. — La necesidad de realizar encuestas entre los ciudadanos para entender adecuada­

mente la problemática de las zonas verdes urbanas. — La vegetación en la ciudad hace la vida más feliz. — La vegetación urbana debe tener una conservación natural.

El doctor George Barker, del Consejo de Conservación de la Naturaleza del Reino Unido, expuso la ponencia «Relaciones existentes entre la ecología, las acciones de las autoridades locales y las necesidades comunitarias en la planificación y gestión de la conservación de la naturaleza en las ciudades británicas», destacando los siguientes puntos:

— L a dificultad de enlace entre ecólogos y usuarios de las zonas verdes urbanas, así c o m o la ignorancia de las autoridades locales hacia ambos.

— La importancia de la conservación de la naturaleza en la ciudad. — Las ventajas de utilizar las organizaciones locales para lograr el enlace entre autori­

dades, ecólogos y usuarios. — La necesidad de contar con material ilustrativo e informativo hacia el público. — El establecimiento de un Patronato de Conservación de la Naturaleza a nivel nacio­

nal que también se ocupa de las áreas verdes urbanas. — La importancia de implicar a las sociedades locales en temas de conservación de la

naturaleza. — El cambio acaecido en la definición de conservación de la naturaleza: ahora se tiene

en cuenta el espacio verde de la ciudad. — L a necesidad de buscar estrategias de conservación de la naturaleza junto con las

autoridades locales, así c o m o implicar a los ciudadanos en la conservación. — La importancia de llevar a cabo planes de investigación adecuada sobre la percep­

ción de los usuarios de las áreas verdes urbanas.

El doctor Claude Leroy, del Laboratorio de Eco-Etología H u m a n a del Instituto Marcel Rivière de Francia, disertó sobre «Papel de las áreas verdes urbanas y periurbanas sobre la salud física y psicológica del hombre», resaltando los siguientes aspectos:

— La importancia de considerar los espacios verdes urbanos dentro de un sistema. — L a necesidad de llevar a cabo experiencias sobre los aspectos exógenos a las zonas

verdes que inciden sobre los ciudadanos (ruidos, contaminación, etc.). — La importancia de analizar el tiempo y la forma de utilizar los espacios verdes de la

urbe por parte de los ciudadanos. — El estudio del comportamiento de los habitantes de la ciudad en el entorno de las

áreas verdes. — La importancia de encuadrar las áreas verdes urbanas dentro de la naturaleza. — La necesidad de lograr que las áreas verdes urbanas y periurbanas disminuyan las

emigraciones de fin de semana de los ciudadanos.

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— La importancia de establecer indicadores cronobiológicos en las áreas verdes ur­banas.

— Las áreas verdes de la ciudad se deben considerar con su entorno natural. — L a necesidad de encontrar sistemas de participación de los ciudadanos en la temá­

tica de áreas verdes. — La importancia de establecer espacios especializados en las zonas verdes urbanas. — L a necesidad de establecer sistemas de vigilancia sanitaria en los espacios verdes

públicos. — La escasez de zonas verdes urbanas conduce a una pérdida del sentido de vida y a la

muerte de la ciudad. — Es preciso encontrar sistemas que reemplacen el césped e implanten árboles produc­

tivos, e incluso establecer lugares de cultivo. — H a y que resaltar el valor educativo que pueden presentar las zonas verdes urbanas. — El hombre es el centro de la naturaleza y es quien debe renaturalizar la ciudad.

La doctora Griselda Benítez, del Instituto de Ecología de México, disertó sobre «Los espa­cios verdes ante el fenómeno de la explosión urbana en la América Latina: el caso de la ciudad de México», llamando la atención sobre lo siguiente:

— L a relatividad de los problemas, cuando se trata de una ciudad superpoblada y masificada c o m o México.

— La degradación del medio natural que conlleva una gran ciudad. — Los problemas de una gran ciudad cuando las áreas verdes son consideradas en

último término. — La solución que se puede encontrar utilizando temporalmente zonas baldías priva­

das para esparcimiento y localización de áreas verdes públicas. — L a importancia de los sistemas de educación al público en la temática de las áreas

verdes urbanas.

U n a vez finalizadas las exposiciones de las ponencias y sus coloquios respectivos, se consti­tuyen tres grupos ad hoc:

— Grupo para diseñar futuras perspectivas para la investigación. Coordinadores: John Celencia y Antonio López Lillo.

— Grupo de planificación y gestión. Coordinador: Pedro Salvador. — Grupo de formación, información y sensibilización del público. Coordinador:

George Barker.

Tarde

Reunión de los grupos ad hoc que redactaron los documentos provisionales de conclusio­nes y recomendaciones, destacando la integración y participación de todos los asistentes al seminario en los diferentes grupos.

24 de abril

Mañana

— El doctor Antonio López Lillo lee las conclusiones y recomendaciones del grupo encargado de diseñar futuras perspectivas para la investigación.

— El doctor Pedro Salvador Palomo lee las conclusiones y recomendaciones del grupo de planificación y gestión.

— El doctor George Barker lee las conclusiones del grupo de formación, información y sensibilización del público.

Se establece un debate sobre las conclusiones y recomendaciones leídas, siendo acepta­das y por unanimidad y agregándose las siguientes sugerencias:

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— Incidir en la formación para que se incluyan no solamente estudios superiores. — Hacer mayor hincapié en la interdisciplinariedad y la utilización de criterios ecoló­

gicos en la planificación. — Agregar temas de biotecnología y reconsiderar la tecnología del transporte por su

incidencia en las zonas verdes. — Insistir en la investigación de los efectos de los plaguicidas sobre el medio urbano,

haciendo llegar estas inquietudes a los Centros de Investigación. — Resaltar la búsqueda de un vínculo de unión entre la investigación y planificación. — Aprovechar las redes que mantiene el proyecto M A B - 1 1 . — Ofrecimiento de colaboración de la Asociación Española de Parques y Jardines Pú­

blicos. — Considerar la creación y conservación de los espacios verdes urbanos c o m o un

medio para disminuir el paro, estableciendo porgramas ocupacionales ligados a la formación.

El doctor Antonio López Lillo pronunció unas palabras de clausura en nombre del Comité Español del Programa M A B , expresando el profundo agradecimiento del Comité del Ayuntamiento de Barcelona por su magnífica colaboración en el buen desarrollo del Seminario, y al Secretariado Internacional del Programa M A B , representado por John Celecia, por la labor desarrollada tanto en la puesta en marcha del Seminario c o m o en el trabajo llevado a cabo durante la celebración del mismo. Igualmente, agradeció a los m a g ­níficos ponentes, tanto extranjeros c o m o nacionales, su asistencia y las estupendas ponen­cias mantenidas durante el Seminario, así c o m o a los invitados españoles constituidos por los expertos más relevantes de la temática de zonas verdes urbanas, que prestaron su apoyo decidido al buen hacer del Seminario.

Tuvo unas palabras de agradecimiento para el equipo encabezado por el señor Folch, que ha permitido que el desarrollo del Seminario haya sido un éxito rozando la perfección. Indicó que se habían cumplido los objetivos del Seminario, demostrado por la altura de las condiciones y recomendaciones, que permitirán ir encontrando soluciones a la problemá­tica de las zonas verdes urbanas.

Expresó que en este Seminario se había abordado una temática amplia y diversa, pues estaba considerado c o m o un Seminario Base para tratar la gran problemática de las zonas verdes urbanas y, a la vista de los resultados, establecer en un futuro próximo seminarios específicos que permitan resolver los múltiples problemas que presentan y pueden presen­tar los espacios verdes urbanos.

Agradeció la oferta de la Asociación Española de Parques y Jardines Públicos para colaborar en el programa M A B y añadió que se mantendrían contactos para perfilar esta colaboración.

El doctor John Celecia, en nombre del Secretariado Internacional del Programa M A B , agradeció la participación y colaboración de todos, haciendo notar la importancia que se había dado a este Seminario dentro del Programa M A B - 1 1 , puesto que era el primero de este tipo que se celebraba. También indicó que haría llegar al Secretariado las conclusiones y recomendaciones, sobre todo las que permitirán diseñar futuras perspectivas para la investigación. Resaltó que estaba m u y satisfecho del desarrollo y resultados del Seminario, que, a su juicio, había superado con creces las expectativas que se habían creado al convo­carlo, y así lo transmitiría al Secretariado Internacional del Programa M A B en París.

Finalmente, el E x c m o . Sr. don Joan Clos, regidor de Sanidad y Medio Ambiente, clausuró el Seminario en nombre del Ayuntamiento de Barcelona, agradeció la participa­ción de todos en el buen desarrollo del seminario, así c o m o el éxito logrado, haciendo notar que Barcelona era una ciudad abierta que acogía con satisfacción todas aquellas reuniones y actividades que redundaran en la mejora de las técnicas y en el hermanamiento de los pueblos, y expresó su esperanza de que las conclusiones y recomendaciones del Seminario sirvieran a la ciudad de Barcelona para mejorar la planificación, gestión y uso del verde urbano, dentro del gran programa que en este sentido lleva a cabo el Ayunta­miento.

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PRESENTACIÓN GENERAL Y OBJETIVOS DEL SEMINARIO

Ramón Folch Coordinador de Publicaciones y Cooperación

Internacional del Comité Español del Programa M A B

Intenciones y finalidad del Seminario

La convocatoria de este Seminario Internacional sobre Tratamiento y Gestión de las Areas Verdes Urbanas reviste ciertas singularidades, ya premonizadas en el enunciado de su pro­pia denominación. El presente Seminario, en efecto, está consagrado a un tema evocadí-simo y sobre el que todo el m u n d o muestra un vago respeto genérico —el verde urbano—, pero pretende abordar la cuestión desde un ángulo científico-técnico, netamente más ope­rativo, y a la par más reflexivo, que el de las tan prodigadas manifestaciones de compla­cencia por los parques y jardines, siempre alabados por urbanistas, expertos y políticos, pero a veces no del todo bien concebidos por los primeros, desatendidos por los segundos y escamoteados por los terceros. El presente Seminario pretende, casi a puerta cerrada, sin preocupaciones escenográficas, propiciar una discusión tranquila, objetiva y competente entre expertos de primer orden, y por ello mismo —inequívoco síntoma de la solvencia científica— más interesados en escuchar que en ser escuchados.

El Comité Español del Programa M A B y el Ayuntamiento de Barcelona, bajo los auspicios del Secretariado Internacional del Programa, han aspirado, al organizar el Seminario, a propiciar el progreso en el conocimiento por la vía del intercambio de parece­res entre expertos, lo que equivale a decir que, deliberadamente, descartan toda posición apriorística conducente a homologar o a desautorizar actuaciones previas, y desaconsejan discusiones inútiles sobre temas triviales o sobre verdades ya establecidas sobre las que todo el m u n d o está previamente de acuerdo. Se trata de compulsar experiencias —es decir, éxitos y fracasos, todos igualmente aleccionadores— y de esforzarse por concluir directri­ces operativas de tratamiento y gestión, capaces de ayudar a terceros a solucionar proble­mas reales, problemas de vida cotidiana. Excusamos decir que la naturaleza y categorías de los ponentes así permite, desde luego, esperarlo, en el bien entendido que, en el con­texto mundial, lo que para unos es obvio, puede resultar novedoso para otros, y que el Programa M A B no se propone estimular el bizantinismo académico, sino forzar colabora­ciones entre estudiosos y usuarios a fin de que el conocimiento, sin dejar de ser fuente de gozo intelectual, resulte a la vez principio operativo de gobierno sensato.

Es en tal orden de cosas que parece oportuno proponer a los asistentes al Seminario unas consideraciones previas que, tal vez, puedan contribuir a encuadrar sus exposiciones de partida y, en consecuencia, puedan ayudar a contextualizar las discusiones. Se trata, en suma, de enumerar una serie de temas que, por lo menos desde la óptica del Comité Español del M A B , están reclamando comentarios y opiniones autorizadas, ejemplificacio-nes a través de casos concretos expuestos en las comunicaciones de los ponentes. Obvia­mente, tal relación temática es m u y perfectible —entre las consecuciones del seminario se prevé, precisamente, llegar a establecer una lista de temas de necesaria ulterior in­vestigación—, y por ello mismo la presente comunicación, más estratégica que técnica, no tiene otro objetivo que la provocación en el más noble sentido del término.

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Sobre el sentido histórico ; biológico del verde urbano

Basta pasear por una ciudad administrativo-residencial del m u n d o desarrollado (Washing­ton), por una ciudad noreuropea de sólida historia moderna (París), por alguna artificiosa capital ex colonial del m á s desheredado tercer m u n d o seco (N'Djamena) o húmedo (Ban­gui), por cualquier gran ciudad asiática tradicional (Kyoto) o por alguna de las pavorosa­mente abundantes y más bien caóticas aglomeraciones urbanas del m u n d o en fases distin­tas de subdesarrollo (Duala, Calcuta, Sao Paulo) para darse cuenta de que el verde urbano tiene sentido e historia diferentes según los lugares. Siempre es el resultado, sin embargo, de dos tipos de actuación: o de conservar los restos de vegetación espontánea del lugar, respetados por el proceso urbanizador, o de crear espacios vegetales de nueva plantación.

Partiendo de esta base, son temas de reflexión y análisis por lo menos los puntos siguientes:

1. Q u é porcentaje de superficie urbana con vegetación espontánea previa ofrecen las ciudades, qué relación tiene ello con el relieve y /o con la política social y urbanística seguida en cada caso, y qué transformaciones, manejo y uso se hace de esas superficies.

2. Q u é porcentaje de superficie urbana con vegetación forzada presentan las ciudades, en qué situación topográfica y estratégica se hallan las manchas verdes, qué dimensiones y características ofrecen (gran parque, pequeña plaza, alineamiento viario de árboles, simple parterre de ordenación circulatoria, etc.), y con qué criterios económicos, sociales, urbanís­ticos y ecológicos se establecen y manejan.

3. Q u é valor añadido, de tipo histórico y cultural, se concede a estas áreas verdes, qué respeto a la historia biológica del lugar se tiene y qué intención de culturización florística o estética se sigue con la selección e implantación de especies y /o micropaisajes exóticos.

4. Q u é intenciones existen de mantener o mejorar la productividad biológica de la ciudad con sus áreas verdes, sea a efectos puramente culturales de referencia ecológica para los urbanistas, sea a efectos higiénico-sanitarios, sea a efectos ciertamente económicos (como los pequeños huertos familiares, que tanto abundan en las urbes del tercer m u n d o tropical).

5. Q u é importancia se concede a la fauna vinculada al verde urbano, singularmente a la fauna ornítica, tanto a efectos estéticos, culturales y recreativos, c o m o a efectos de cohesión y estabilidad ecológica del propio verde (control de plagas, dispersión de semillas, etcétera).

La respuesta a éstas, y todavía a otras preguntas, debería ser la base estratégica de toda política de gestión del verde urbano. Por ello, debería ayudarse a los poderes públicos a estar al corriente de todo ello, a fin de abolir muchas actuales situaciones viciosas no necesariamente malintencionadas, que recuerdan las malas actuaciones arqueológicas o urbanísticas de décadas anteriores, hijas, en buena parte, de una falta de clarificación teórica previa.

Sobre los beneficios cívicos del verde urbano

El entusiasmo de la población por las áreas verdes es inversamente proporcional al grado de ruralización de su vida cotidiana, lo cual es lógico y esperable: los habitantes de las pequeñas aldeas de economía agrícola, forestal o ganadera viven rodeados de campos, bosques y prados, de m o d o que son excedentarios en aquello que son deficitarios —patológicamente deficitarios, a m e n u d o — los ciudadanos. Pero ese clamor urbano por las zonas verdes se manifiesta de manera profusa, confusa y difusa, c o m o ocurre siempre con las actitudes multitudinarias. Sin embargo, lejos de ser ello una causa de banalización del tema ante los ojos de los responsables públicos, debe presentarse c o m o un motivo de reflexión que lleve a clarificar y a jerarquizar las actuaciones.

Por otra parte, es un hecho que la dificultad en sostener las áreas verdes urbanas es directamente proporcional a la necesidad de poseerlas: a mayor congestión urbana que exige verde para los habitantes, mayores problemas económicos y urbanísticos para m a n ­tenerlo. Los respetuosos niños rubios y ricos que corren por amplios parques de ordenadas

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y espaciosas ciudades escandinavas crean pocos problemas a los cultos y competentes jar­dines nórdicos, mientras que la multitudinaria chiquillería desharrapada que se hacina en los bidonville puede arrasar en segundos un raquítico jardincillo hecho con más buena intención que acierto por algún agricultor desplazado que ejerce de jardinero, sin serlo, en un mal suburbio tercermundista. Y , sin embargo, son los segundos, rodeados de cemento o de adobe, fumigados a diario por automóviles o industrias, quienes más necesitan lo que no saben usar y conservar.

Al respecto se plantean varias cuestiones que, siguiendo con la numeración indicada en el punto anterior, pueden ser por lo menos las siguientes:

6. Hasta qué punto el verde urbano debe ser considerado en términos puramente ornamentales o debe verse en términos funcionales del sistema urbano y, por lo mismo, elevado sin reservas a una categoría de gestión comparable a la del alumbrado (que tam­bién es simplemente ornamental en algunos casos), o la de la pavimentación de las calles, o la del suministro de agua.

7. Cuál es el auténtico paso del verde urbano en aspectos de ecología urbana seria, como los balances gaseosos (oxigenación, regulación de C 0 2 en la atmósfera inmediata al suelo, precisamente la que envuelve a los urbanitas, seres de apenas un par de modestos metros de alto), la retención de partículas sólidas en el dosel constituido por los alinea­mientos viarios de árboles, el efecto de pantalla acústica de las masas verdes interpuestas entre focos ruidosos (vehículos, industrias) y núcleos de habitación, etc.

8. Qué criterios deben seguirse para hacer del verde urbano un lenitivo de los rigores climáticos en los países cálidos, y en concreto qué sabemos de la sombra arbórea en países m u y soleados y de sus beneficios sobre los viandantes o sobre el pavimento (el reblandeci­miento estival del asfalto es moneda corriente en el Mediterráneo, por ejemplo).

9. Q u é efectos tienen realmente las masas de vegetación urbana sobre el equilibrio psicosomático de los ciudadanos, en razón de sus insoslayables atavismos biológicos, inde­leblemente compendiados en su programación genética, c o m o cualquier otra de sus pautas instintivas de comportamiento.

10. Hasta qué punto la simple proliferación de espacios abiertos no verdes (plazas pavimentadas o duras, grandes avenidas), que al esponjar la trama urbana atenúan el agobio de la congestión demográfica, cubre las necesidades citadas, además de satisfacer otras necesidades cívicas.

Estos y otros puntos ponen de relieve una cuestión básica: el verde urbano no sirve únicamente para hacer bonito. Es preciso, por tanto recordarlo a los gestores públicos e informadores del papel funcional que desempeña en la ciudad.

Sobre los problemas de manejo del verde urbano

La articulación urbana se traduce en un medio progresivamente hostil para la vida vegetal (y probablemente también para la vida humana, pero éste es otro tema, o tal vez no, si consideramos que la presencia de verde atenúa retroactivamente la artificialización nociva y favorece, por lo mismo, la vida del hombre). Las plantas, en efecto, viven mal en la ciudad que tanto las necesita, por razones microclimáticas, edáficas y de polución. Incre­mentar los espacios verdes en superficie es, si bien se mira, la mejor manera de incremen­tarlos en calidad, puesto que a más verde, menos gris, o sea, mejor verde. Es decir, mejor hombre, c o m o acabamos de comentar.

El caso es que los gestores del verde urbano encuentran problemas crecientes, sin embargo, para su mantenimiento. Desde fenómenos físicos aparentemenrte banales, c o m o las áreas de sombra proyectadas por los grandes edificios que hacen de las relativamente estrechas calles o plazas inhóspitos valles profundos sin sol, hasta reconocidas agresiones químicas por contaminantes atmosféricos o ataques físicos por acciones incívicas de los ciudadanos, pasando por problemas de irrigación o de nutrientes edáfícos, todo contribuye a erosionar la vitalidad de los vegetales urbanos y a hacerlos presa de toda suerte de enfermedades carenciales o parasitarias. Por otra parte, las complicaciones burocrático-administrativas o la simple falta de recursos económicos constituyen también una sólida

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contrariedad de gestión que, a efectos del verde, y aunque de m u y singular etiología, vie­nen a ser agentes patógenos indesables.

A la vista de estas cuestiones, cabe interrogarse y esforzarse por encontrar respuesta a las siguientes preguntas:

11. Q u é especies y /o variedades deben escogerse para las zonas m á s duras de la ciu­dad (arbolado viario, pequeñas plazas, ordenaciones circulatorias) a fin de que, por una parte, resistan las previsibles agresiones que sufrirán, y de que, por otra, respondan a lo que de ellas se espera en materia de ornato, de pantalla acústica, de producción de sombra, etcétera.

12. Q u é especies y /o variedades deben escogerse en función no sólo del clima y del microclima ordinarios, sino también de los fenómenos climáticos de ciclo largo que, por aparecer una vez cada veinte o treinta años, tendemos a olvidar (las heladas de 1956 y de 1985, por ejemplo, dañaron m u y seriamente multitud de entrañables exotismos —pal­meras, suculentas, etc.— en Barcelona y poblaciones próximas).

13. Q u é criterios deben observarse al escoger caducifolios en función de sus respecti­vas ventajas (belleza, rapidez de crecimiento, sombra generosa) enfrentadas a sus inconve­nientes (hojarasca otoñal, exigencias hídricas, desolación invernal), o al hacer lo propio con los perennifolios ante sus ventajas (rusticidad, invariabilidad fenológica, sobriedad hídrica) y ante sus inconvenientes (escasa sombra, poca espectacularidad, lentitud de crecimiento).

14. Q u é política debe seguirse en cuanto al abonado y a la irrigación del verde urbano, en función de la estrategia municipal de tratamiento de aguas residuales (que a m e n u d o se pierden, una vez tratadas, mientras se usa agua blanca para el riego) o de eliminación de residuos domésticos (que podrían ser, por compostaje, la principal fuente de nutrientes gratuitos para el verde urbano y periurbano), serían ecológicamente lógicos (de hecho serían económicos precisamente por ser «eco-lógicos»).

15. C ó m o deben estar concebidos los tratamientos fitosanitarios para no perjudicar a terceros (pájaros, la propia población humana); c ó m o , cuándo y dónde deben efectuarse las podas, suponiendo que sea razonable hacerlas (recuérdese que se trata de una práctica agrícola para mejorar la producción, de un recurso jardinero para obtener formas capri­chosas, o de una solución traumática para eliminar ramas molestas a terceros, pero no de una necesidad biológica de las plantas).

16. Q u é actitud debe adoptarse ante el fenómeno inevitable del envejecimiento de las masas arbóreas coetáneas, a m e n u d o parte integrante de un paisaje urbano (los pinos de R o m a , los plátanos de las Ramblas de Barcelona, por ejemplo) condenado a desaparecer a fecha m á s o menos fija.

N o costaría alargar todavía m á s esta lista de consideraciones. Pero no hace falta, por­que sí que costaría, en cambio, encontrar solución a todas y a cada una de las cuestiones planteadas. Sin embargo, este Seminario puede contribuir poderosamente a avanzar solu­ciones. E n nombre de los organizadores, por tanto, les invito entusiásticamente a dedicarse a ello. Gracias.

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NATIONAL, REGIONAL AND LOCAL PLANNING STRATEGIES FOR URBAN GREEN AREAS IN THE NETHERLANDS.

AN ECOLOGICAL APPROACH Tjeerd Deelstra

Office of Research in Ecology and Planning. Delft University of Technology (Países Bajos)

Past history of towns and green spaces in the Netherlands

The historical relationship between town and landscape The structure of the old Dutch towns is largely determined by the landscape. The pattern of h u m a n settlements resulted from a long series of interaction between people, land and landscape.

In the West Netherlands, site of the modern «Randstad Holland» or «Ring City», the first settlements were formed on high-lying creek ridges and along rivers, in the middle of peat bogs, or on the leeward side of the dunes, directly behind the sea. The peat bogs have been cultivated ever since mediaeval times; first the strips of eutrophic woodland peat along the rivers, then the complexes of oligotrophic peat further away, and finally the mesotrophic marshland peat far inland. The hinterland and the rivers supplied the towns with building material (clay for bricks; wood) , fuel, drinking water and food (fish, game, cereals, meat, dairy products).

Deforestation, excavation and drainage caused the peaty hinterland to subside to an increasing degree and at an increasing rate, so that these areas eventually sank several metres lower than the original habitation centres by the rivers and dunes. The consistency of this land necessitated more sophisticated water management; systems of draughts, drain­age ditches and canals were dug, and series of increasingly advanced (wind) mills were built in order to p u m p the water out of the lower-lying hinterland into the rivers and the sea.

The structure of the old town Towns were traditionally laid out on what was theoretically a simple grid: canals for drai­nage, basically parallel or at right angles to the (excavated) river or inlet; on either side were streets lined with trees (attracting woodland birds); at right angles to these «water­ways» (a favourite venue for waterbirds and fish from the surrounding polders) were narrow alleys and roads which were mainly left unplanted, but with an exciting mural vegetation, depending on what kind of cement was used. M a n y of the blocks of houses or courtyards in between had large, peaceful gardens, some of which were used for growing vegetables, fruit and herbs. There were several green open spaces in the town which were used for cutting reeds, drying dyed fabrics and similar activities. Where the canal and street systems intersected there were larger squares with public buildings: the centrally situated churches with their green graveyards, the markets and spaces near the town (water) gates.

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The squares were usually lined or «roofed» with trees to provide shelter from the sun or wind and because people regarded this as attractive and in keeping with their conception of what was right and proper.

The towns near the dunes had a more wooded situation, the original forests lying just outside the town walls. The «Haarlemmerhout» is such a forest; designated for children's play in 1389, it is probably the oldest town park in the Netherlands.

The historical outskirts Later, when large-scale fortification works were built, the encircling moats were planted with vegetation, resulting in a solid green belt around the town for breaking the wind and providing an habitat for a variety of birds and m a m m a l s . M a n y of the «arcadias» published in the 16th and 17th centuries describe the pleasant «promenades» which could be enjoyed along these bastions; the arcadias were paeans to the glory of the town and surround­ing land.

Citizens w h o could afford to do so —and there were plenty w h o could in the prosperous Netherlands of the 16th and 17th centuries— built country houses with their o w n parks in the countryside by the rivers and in the dune areas outside the towns.

In the riverland regions this led to reforestation, in the dunes, though, to deforestation. Around the country houses a specific «mound» vegetation developed, consisting of bulbs imported from other countries.

Changes caused by explosive urban growth

Bastions, public parks and garden villages, and the urban desert The industrialization and intense population growth which started in the last century led to radical changes in the picture just described.

The open spaces within the town limits were filled unhygienically with buildings. The fortifications were demolished: some of them were m a d e into public parks.

W h e n buildings started to be put up in the outskirts, private initiative (like Sarphati's in Amsterdam, for instance) occasionally provided public parks. S o m e industrialists also built garden villages near their factories (the Agneta Park in Delft is a very good ex­ample).

Sometimes luxurious residential neighbourhoods were built near a park in order to attract well-heeled investors (one example being the houses in the streets around Amsterdam's Vondel Park, formerly the garden of a gentlemen's club which was opened to the public). For similar reasons parks were occasionally planned as central elements in a new neighbourhood.

The parks of former country houses n o w swallowed up by encroaching urbanization were often re-parcelled into villa suburbs (such as Velserbeek near Ymuiden, the suburbs of The Hague, and so forth). The «English landscape style» —as it is called in the Netherlands— set the tone for the new approach to these parks and districts.

A wide variety of exotic plants n o w appeared in the parks, leading in their turn to all kinds of horticultural activities.

In the meantime exploiters had been building several working-class neighbourhoods without any green spaces at all. The resulting «urban desert» was a favourite haunt of the small m a m m a l s , birds and the like which were at h o m e in the rocky deserts (such as mice, sparrows, pigeons, etc.).

Public housing and urban planning Towards the end of the 19th century, measures were adopted with a view to more hygienic building and the promotion of government supervision and intervention in the hitherto «uncontrolled» urbanization. These measures were embodied in the 1901 Housing Act, which henceforth empowered municipalities to establish «development plans» for housing. Municipal parks were also subject to these plans, the municipalities being entitled to expropriate land «in the interests of public health and recreation».

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Nature protection Around the turn of the century a number of private organizations were set up in the Netherlands to protect the countryside as a reaction to the depradations caused by housing construction and infrastructure, and also in order «to instill the masses with a love of nature». Leading figures in the nature movement such as Thijsse propagated the laying-out of natural and educational parks. «Thijsse's Hof» in Bloemendaal, near Haarlem, is a splendid example, and Thijsse's influence can also be seen in the «Amsterdamsche Bosch», a large municipal park which was part of the 1935 Amsterdam Development Plan.

A functionalistic approach to the town and green spaces The nineteen-twenties marked the formulation of the principles of «international style» architecture and town planning. The point of departure was to establish a physical separation between working, living and recreation; traffic was regarded as a separate planning category. Each activity required its o w n space. This «functionalism» involved a more systematic and scientifically underpinned provision of green spaces in town planning. A system of norms was applied henceforth: a town-dweller is entitled to a certain area of neighbourhood, district, suburban and urban vegetation (always within a certain distance from his or her dwelling). All new residential areas comply with these norms, and national and provincial authorities still apply similar norms to local building plans.

The Amsterdam Development Plan, which had a great influence both at h o m e and abroad, proposed a network of «green belts» linking parks in the various neighbourhoods, districts and suburbs and intended as recreational routes for the inhabitants. These belts are often combined with the road network. Adjacent to them are the residential areas with medium and high-rise building on an open-field system. The result is a great deal of vegetation in the residential areas: collective and (semi-)public «residential greenery» for children's playing areas, most of it, however, purely for the eye. M a n y fast-growing trees such as poplars were planted in order to m a k e the new districts attractive quickly. Sport facilities were provided in the parks, and allotment complexes for a host of gardening associations. Outside the town, green routes cross the countryside (for cyclists and walkers, for in 1935 the car was still exclusive). Functionalism also stimulated ideas about towns on a regional scale, and consequently the relation between urban recreation and landscape planning.

The relationship of land, water and climate The new urban development areas in the Ranstad had to be built in the polders close to the towns, the former cultivated peat bogs.

In order to build quickly and cheaply, the peat beds were covered with saline sand from the sea, or with sand from the depths of the prospective residential area. In the latter case the pit could later be m a d e into a recreational lake, thus making «work with work». Examples are the «Sloterplas» in Amsterdam and the «Kralingerhout» in Rotterdam.

Unselective raising of land, combined with high-rise building and uniform, fast-grown-ing vegetation, has grave consequences for nature in residential areas. The results are a lower groundwater level and faster rainwater drainage, dehydratation and higher urban temperatures and a more rugged physical climate.

The vegetation environment is not very varied. The sharp rise in motorized traffic since the fifties, which was alotted more ample space in residential estates built in this style later, has also had deleterious effects (more paved areas, harder soil, acid rain and polluted water, heavy metals, asbestos and the like in the water, soil and air).

D u e , however, to the profusion of vegetation, large numbers of birds and plants have spontaneously made their habitats in new districts, depending on methods of upkeep.

Urban expansion

Living in green zones The sixties heralded a new phase in the urbanization of the Netherlands. Reconstruction

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had originally been carried out according to prewar plans. A major part of the 1935 Amsterdam Development Plan, for example, was realized in the fifties. Cities started to expand. As a consequence of growing prosperity and insdustrialization, however, an increasing need for space m a d e itself felt. General motorization enabled people to live further away from town and work. This led to intensive suburbanization, the surround­ing countryside being crisscrossed by roads.

M a n y Dutchmen n o w had the means to live «in the country», in urbanized villages where the physical living environment was a great deal more agreeable than in the anonymous , somewhat uniform high-rise urban districts erected along functionalist lines.

Concentrated déconcentration in the urbanization pattern; green buffers and green stars In 1966 (in the middle of the urban expansion period), the Government Planning Office, set up in the forties, issued an important Report on Physical Planning. The report stated that town planning ought no longer to be in the hands of local municipal authorities. The Physical Planning Act passed after World W a r O n e n o w obliged the provincial authorities draw up regional plans, recreation being one of the items. In one province important to the Randstad, Zuid-Holland, incidentally, this led to the formation of a separate design department for recreation projects. The government report was based on the principle of physical separation of agricultural and nature areas on the one hand, and of urban and industrial areas on the other. The report proposed a model of «concentrated deconcen-tratrion» to cope with suburbanization.

Urban agglomerations were to be formed from districts of varying density and with prescribed internal (including «green») facilities. S o m e urban environments were divided by open green spaces.

The agglomerations were separated by green buffers and the green heart of «Randstad Holland»; the peat pasture-land in the centre of the Randstad, the former site of the large peat bogs, was to preserve its unbuilt and agricultural status.

A system or regional recreation parks was proposed, surrounding the cities and within easy motoring distance (indicated by «green stars»); a series of «white stars» was planned on the basis of prognoses in order to satisfy recreational requirements a little further away: large natural areas with a set capacity —which could be enlarged if necessary— for urban leisure-seekers.

This manner of coping with urban activity in green spaces was underpinned with primarily sociological research, traffic research and so on.

The morphology of the agglomeration expansion pattern itself was attuned to the ecological structure of the landscape. The said government report indicated large areas with specific landscape-ecological properties outside the towns, and the gradients in the landscape where dwelling nuclei were traditionally situated. In the gradient zones a particularly large number of different environmental conditions are of influence, there consequently being an extremely high degree of potential and actual differentation in natural communities.

The basis for this approach is a theory by the ecologist V a n Leeuwen about the relationship between pattern and process in eco-systems. This ecological determination of position in urbanization policy was followed in the years after the government report by a number of studies on h o w urban expansions might be developed in relation to gradient zones, and m a r k the start of urban ecology in the Netherlands.

Green buffers, green stars and an inviting living environment In relation to the aforementioned government report on physical planning, several regional recreation areas were installed round the cities. In m a n y of these projects the «work with work» principle was adopted. For instance, work was done with household waste, large amounts of which are usually produced, and with construction and demolition waste, creating hills in unexpected places in the flat Dutch landscape (at Rijswijk near The Hague , for example). The excavation of a creek in order to improve water facilities for agriculture and industry paralleled a recreation project for water sports (the Bernisse in Rijnmond).

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In the actual agglomerations attemps were m a d e to comply with the public's desires with regard to living which were becoming clearer as investigation and action progressed; the idea was to create what was called an «inviting living environment». Low-rise building in combination with a profusion of adventurous vegetation and water and safe «havens» were the point of departure; new environmental techniques were developed in relation to town planning. A n example is Tanthof, a new district in Delft, where the ground was raised in a selective manner, i.e. only beyond zones for parkland belts, and not on old creek ridges. The main structure of the district is determined by an old dyke with farmhouses which have acquired a new function in the residential estate. In another town, Breda, houses have been built around old parkland belonging to a country house. These and other examples of new housing are based on local environmental conditions. They are representative for the 1978 government urbanization report, which emphasized the search for a vegetation structure «as a countermould of urbanization» and for developing smooth transitions between town and country, and the timely planting of forest.

Another important policy item is the construction of towns along public transport routes and in a closer relationship to the former old town with a view to a less wasteful use of space and energy.

An urban nature movement In new housing districts, which are marked by modern technology, and in the older districts which had been neglected prior to the sixties, inhabitants have developed a number of initiatives for making their surroundings more natural. These initiatives have gradually been adopted by the authorities and have come to form the basis of policy, as demonstrated in the previous paragraph.

The work of the Amsterdam «provos» and «gnomes» is well known; in 1970, for instance, they drew up a «green report» containing several recommendations for improving the urban environment, managing ruderal terrain, banning chemical pesticides in vegetation upkeep, and so forth. This gave experts such as Kant, Vahl, Mostert, Landwerh, Zonderwijk, Le R o y and m a n y others more chances to put their ideas about natural gardening into practice; planners, architects, artists and landscape architects such as Smienk, Reh , Gonggrijp, Saariste, Deelstra, Polak, Feijen and m a n y others were able to launch their ideas too.

Three kinds of ecological parks A great deal of experience with natural gardens was obtained in the seventies. The basis was formed by Thijsse's ideas. Three kinds of natural gardens and parks can currently be distinguished in the Netherlands: «wild plant gardens», «nature or landscape gardens» and «Le R o y gardens».

1. Wild plant gardens or parks. The idea of a wild plant garden or park is to gather together as m a n y wild plants as possible which originate in the same area but have often disappeared or are in danger of extinction. The aim is to reconstruct the rich vegetation which has been lost, and thus to combat the impoverishment of flora and fauna. The original natural landscape is simulated in order to create an environment for the plants one would like to see there. Undesirable plants are discouraged (uprooted).

The significance of a wild garden or park lies primarily in the relaxed educational aspect. People can encounter and become acquainted with Dutch wild plants there, which m a y induce them to m a k e an effort to preserve areas in which such plants still occur. T o enhance the educational value, a field might be added where plants m a y be plucked, or a bed of medicinal and kitchen herbs, patches with nutritive crops such as corn, potatoes, rice, rye, wheat, etc., which in their turn stimulate the growth of m e a d o w weeds.

The most suitable terrain for wild gardens or paries are verges, sparse hayfields, marshy areas, sand-sprayed sites, hollows, claypits, quarries, dunes, sandhills, woodwalls, poor river sludge and old fortification walls. All of these have fairly meagre soil on which rich vegetation normally flourishes.

Soil can be enriched for plants requiring more nourishment. However, it takes a lot more effort to deplete the quality of rich soil. A n area with a stable water-level should be

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chosen. If the environment is favourable, as few changes as possible should be made . For the rest, the soil should be treated in accordance with the desired environment. If existing soil is to be used, it can be turned in order to suppress existing flora. Poorer soil can also be brought to the surface in this fashion. Various thicknesses of this poorer soil will produce different environments. The soil can be rendered more acid by the addition of calcium-deficient sand and a layer of peat. If more calcium is required, ground shells, marl or dolomite lime m a y be added. Paths should be inconspicuous, m a d e of close-clipped grass, w o o d shavings or something similar.

Trees are planted first, to be followed, once the right environment has been formed, by shrubs. Sensitive species should not be planted until the desired environment has been created.

Wild garden upkeep should emulate the manner in which the sought-after landscape was formed. Blue grassland requires moving and removel of the cuttings, woodwalls need to be thinned every five years. Every landscape thus requires a different management. External influences should be avoided as far as possible. Upkeep, too, should involve as little intervention as possible. A scythe is best for cutting grass; weeds should ve careful­ly uprooted, not dug out. Weeding has to be done in order to prevent robust plants such as the w o o d horsetail, various grasses, sheep's sorrel and the like from spreading before more delicate plants manage to establish themselves.

The advantages of laying out wild gardens and parks in this manner are: — Fast attractive results. — High educational value due to the presence of a large number of plants which are

not to be found elsewhere. — M a n y endangered species are given a chance to proliferate.

Disadvantages are: — A lot of effort is required. — The work can only be done by gardeners w h o are wellinformed about plants and their

natural environment. 2. Nature or landscape parks. Nature parks incorporate the different natural envi­

ronments to be encountered in the Netherlands. A wide variety of environments in the nature garden will automatically enssure a wide variety of vegetation.

Environmental variety m a y be obtained by having different levels above groundwater, differences in relief, different soils and varied afforestation. It is important not to have sudden changes from one soil to the next, but to have a gradual gradient, with the poorer or lime-deficient soil above the richer soil. This kind of gradient will produce the greatest variety of vegetation.

T h e required soil is best obtained from existing stocks or shifted from other places, preferably in the same region. Before the park can be laid out, the composition of its soil should be examined, and the thickness of the topsoil layer and the height of various spots in the park above groundwater level should be established. These data can be used to m a k e a plan for shifting and bringing soil. The location of a lake with gradually sloping banks and an adjacent marsh can also be decided on. A cavity wall m a y be built from old bricks with old-fashioned mortar so as to create an environment for wall-plants and birds that nest in hollows.

Care should be taken to lay paths at right angles to soil borders and /or contour lines. Various materials m a y be used to reinforce paths and to introduce more variation in the environment. Sowing each section with the plants one might except to encounter in that environment accelerates the development of the vegetation. Digging and sowing are best carried out in early October or between the first half of M a r c h and no later than mid-April. It is advisable to limit planting to trees and brushwood, but to plant more of these that are ultimately necessary. This is more likely to produce a woodland environment, which can always be thinned out later. The upkeep of a nature garden depends on the environments in it. W e e d m e a d o w s must be dug over every year and cereals sown. F a r m ­yard manured m a y occasionally be necessary. Grassland on poor soil must be cut once a year, grassland on richer soil twice. The cuttings should be removed. Dry heaths should be cut every five or ten years; it is better to cut sods from wet heaths.

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The upkeep of copses and brushwood consists of topping and pruning superfluous w o o d . Once the trees and shrubs have reached a size enabling them to provide sufficient shade, woodland plants m a y be sown. It is better to keep to lowgrowing vegetation in fairly small nature parks.

W o o d s and shrubs, as well as weed meadows , need areas of at least one and a quarter acres (half a hectare). These larger nature parks also attract large numbers of nesting birds. A nature park is not a static entity to be kept constantly in the same state, but a dynamic whole which continues to develop. At first intrusive plants will establish themselves, to be replaced as time passes by plants which have adjusted to a more stable environment. The nature park will thus never be dull, and the concept of «succession» will become clear to the users of the garden. The time-factor will teach people appreciate the value of long­standing nature areas, and realize that their formation takes a long time.

Advantages: — Local inhabitants obtain an area of nature in their direct surroundings, accessible to

all. — Because they are involved in layout and upkeep, they feel more of a commitment. — M e m b e r s of the public working in the nature garden learn the practical side of h o w

the natural environment is formed and h o w it can be affected by humans . — The nature garden fits in well with biology project in local primary and secondary

schools. Disadvantages: — A permanent nucleus of voluntary workers in needed for occasional upkeep and to

inform and recruit people for special nature projects. — Municipalities must provide expert supervision and the necessary material. 3. The Le R o y approach. The projects set up by Le R o y are based on the premiss that

town, people and nature should function as an entity. A town's vegetation should not be a separate item in communal living, kept apart from other activities or organized by the authorities, but ought to be planned and executed entirely by the inhabitants themselves. Spaces currently in use for public greenery and maintained by municipal gardeners ought, according to Le R o y , to be really public in the sense that they should be run by local inhabitants, either singly or in groups, w h o can put their o w n ideas into practice. This would avoid the waste of a lot of knowledge and creativity. In every local association there are people with bright ideas about improving green spaces but with insufficient opportu­nity to m a k e themselves heard. This kind of green space should not be static in the sense that once it is laid out it is maintained in that state. O n the contrary, there ought to be a dynamic process in which the vegetation grows together with the inhabitants. After all, population groups do not remain constant. People m o v e away, and others take their place; fashions change and with them people's expectations regarding vegetation. By putting people in charge, vegetation can adapt to these changing expectations. The public's contri­bution to this kind of green space is mainly in the form of design, the introduction of new kinds of plants and the construction of facilities such as sheds, beehives, playgrounds, paths, benches and so forth. Nature will take care of the rest. Plants are competitive, and the most adaptable will survive. The introduction of several new species will maintain a high degree of variety. N o plants should be removed by weeding, since this disturbs the soil. Dead branchesmay be chopped into pieces and spread on the ground (not all in the same place, or the soil will suffocate!). Different levels and the introduction of different kinds of stones and other material creates a wide range of micro-climates, encouraging a large variety of plants. A n y material introduced later must be in keeping with existing vegetation.

Various light and shade effects can be achieved by varied vertical structure. W e t sec­tions must remain in contact with the groundwater —not separated by a layer of concrete or plastic— and be wetter or dryer according to the season. It is important not to keep the groundwater at a constant level by artificial means such as drainage or the addition of water during dry spells. A low-lying path in s u m m e r will fill up with water in winter.

The introduction of new plants should not only depend on the beauty of the bloom but on the shape of the plant and the depths of the roots too. In places where a town is

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dominated by the straight lines of buildings, green spaces should provide contrast by means of winding paths and different levels.

In the direct vicinity of big cities any species that is able to grow at all is given a chance by the introduction of m a n y varieties —including exotics—. Such «flora forgery», which Le R o y feels should be avoided in truly natural areas, is not wrong according to this philosophy, the vegetation in this case already being fully determined by h u m a n activity.

In this form of green space, the contribution of the municipal park department is minimal, not really amounting to m u c h more than providing space and money. Public participation is high, in both installation and later modification. Little upkeep is required, the only tasks being to chop and distribute plant waste in order to accelerate decay, and the upkeep of any facilities.

Advantages: — This is an extremely cheap form of green space. — Inhabitants feel directly involved in the green space, resulting in less wanton des­

truction. — The green space is m u c h more in line with the inhabitants' needs. Disadvantages: — The approach works best when applied to an entire town. — The public must be kept constantly informed in order to maintain interest in this

form of green space.

Ecological studies in connection with physycal planning and environmental management A s a consequence of the influence of the environmentalists, and due to the solid foun­dation provided by the aforementioned government physical planning report of 1966, it became increasingly feasible in the seventies to involve ecology in physical planning.

O n a national scale and in all the Dutch provinces, a variety of methods were used to inventorize and evaluate integral environmental developments. Ecological models were also designed; on a national level, for instance, a comprehensive ecological model of the Netherlands typified the urban eco-system amidst a variety of other kinds of prevailing eco-systems. There were also ecological-economical models and models for ecology-related water management. Current studies are devoted to large-scale ecological infrastructure, linked, for instance, with bird migration or groundwater movement, or to bio-indicators for pollution, to biological measuring networks and to the environmental effects of urbani­zation; the last study is being carried out in the framework of tests for environmental impact reports.

There is no systematic ecological inventory of the Dutch inner cities. Nor is there an ecological plan for an existing urban area as a whole. There are however a few incidental inventories in the urban ecological field which have been drawn up at the initiatives of local clubs or nature-lovers, or/and universities (examples: Tilburg, Utrecht, Vianen, Middelburg).

S o m e municipal departments, often influenced by the personal ideas of a staff m e m b e r , are inclined to experiment or m a k e a construction or park plan for a small area on an ecological basis (Zwolle, The Hague and Delft, for instance). Theoretical studies and un­executed plans exist for urban developments with a sound ecological basis (for Dordrecht, for example, and for Hellevoetsluis). Although on a governmental and provincial level professional ecologists have joined the relevant departments, hardly any Dutch municipali­ties, not even the big cities, recruit ecologists. Nonacademic training institutes for munici­pal park department staff —which is not usually very large— have as yet paid scant atten­tion to ecology, nor very m u c h to the sociocultural aspects of municipal vegetation or design either. The accent is more on technique, maintenance and management, on aesthetic greenery and on open spaces for sport and recreation.

The planners w h o might be expected to come up with ideas are generally too engrossed in routine work and organizing public participation in building projects. Garden and landscape architects are only consulted for specific assignments: sports grounds, flower shows and suchlike.

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It is mainly up to active members of environmental associations and local groups to provide a platform for ideas about green spaces with a sound ecological basis.

A few years ago a major initiative was taken at a national level. A «nature in the city» project with a primarily educational approach publicizes the importance of an ecological local green space policy by means of publications, exhibitions and workshops.

The initiative looks like being adopted here and there at a municipal level, as demonstrated by investigations into the setting up of ecological urban plans. A s a follow-up to the national project, a «state of the art» report is currently being written, featuring not only basic educational material but also ideas for the further development of policy in this area.

The need for urban management and renewal

Urban decay In the wake of the economic recession of the seventies, Dutch towns have obviously dete­riorated, partly due to the circunstance that m a n y activities (living, working, recreation) had hitherto been spread out in spacious surroundings. Economical resilience was impair­ed. The urban environment was dirty and polluted. A n d the landscape outside the towns, despite the concentrated déconcentration policy for living and working areas, and despite all the ecological research, had lost m u c h of its quality.

Various urban models In the debate on the future of Dutch towns, diverse ideas have been launched about ways and means of urban renewal and regeneration. A number of urban «models» have been worked out or are being studied:

— The recreational city. — The compact city. — The efficient city. — The natural city. — The social city. — The meaningful city. The recreational city is based on the premiss that people should be able to enjoy street

bustle and the variedipalette of facilities the city has to offer. Furthermore, people should be able to unfold their o w n creative potential in their homes and local surroundings, in free activity too. Traffic nuisance must be minimized; suburbs should acquire urban quali­ties; outskirts should blend with the landscape and the area around the city should be made accessible with small-scale means.

The compact city embodies a philosophy of densification. The old functionalist style m a d e a mess of space, encouraging the economic malfunction and social désintégration of the cities. There are however numerous ways and means of rearranging the large-scale residential districts dating from the urban expansion age. The physical climate can be improved by filling useless open zones with buildings, etc. Enhancing mutual proximity can intensify social intercourse.

The efficient city stresses the need to reduce waste in the urban household of water, material and energy, and the improvement of waste flow management and infrastructure for transport and traffic. The air, water and soil of the efficient city are clean, and the city does not draw unnecessarily on natural resources.

The natural city points out the quality of the physical and biotic environment in the city for all kinds of organisms, plants and animals in their relation to city-dwellers. Atten­tion is also paid to the h u m a n ecology of various categories of inhabitants such as chil­dren, the handicapped, the aged, w o m e n , m e n , etc.

The social city is based on the need for new forms of cooperation in living, production, creativity and transportation; they can be sought among the m a n y innovative grassroot groups currently active in the cities. Abolishing the division between living, working and recreation casts a new light on the meaning of public (green) urban space.

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The menningful city's objective is to (re)model cities by improving the visual quality by means of desing methods aimed at recognizability, identity and a readable structure in the built environment. This urban concept is a critiscism of the spineless translation of an addition s u m of the public's programme of requirements (presented these days by way of public participation) by teams of experts without heeding a designer's personal point of view, as in the preurban expansion age.

The green open spaces in the various urban models Water, park and sport facilities feature prominently in the recreational city, there being a heightened interest in nature in and around the towns. In terms of space, current ideas about designing urban green spaces are developed: work with work (recreational lakes, for example), a host of recreational facilities (requiring quite an acreage) and lots of green space for play around dwellings, navigable canals and the like, in emulation of what has already been done in m a n y new districts.

In the compact city, ways and means of re-using old dockland and industrial areas are being sought. The concept is largely aimed at public and private housing.

The conception of the compact city has led at a national level to major reductions in the planned expansion volume of the cities, and in urban «overflow» in satellite towns often situated far away from the mother-city.

The compact city does not have a concept for green spaces; the proposition is that there is too m u c h useless aesthetic greenery in the cities. This occasionally elicits protests from suburb-dwellers, where —years after it was planted— vegetation has matured. The inhabi­tants are afraid of losing what to m a n y of them is the sole attractive quality of their surroundings.

The efficient city pledges itself to improve the city-nature relationship. In this concept the outskirts and surrounding areas of the city play an important part: as a water-extraction area, as a location for sewage-farms for urban waste water, and so on. In c o m ­bination with natural construction this urban concept can lead to a marked improvement in the vegetation structure.

The natural city concentrates on the possibilities of nature in and around the cities. A s well as providing the city with a system of green veins and articulation (routes for animals, improved climate), the concept points out the importance of urban biotopes, geomorpho-logy, air humidity, wind and water, soil and vegetation as necessary conditions for urban development and restructuring; it also advocates the sound ecological management of open spaces. Use is m a d e of experience gained from nature management, educational gardens and the like, and a call is m a d e for natural construction, of which the Netherlands has m u c h experience, acquired both a long time ago and more recently (especially in rural areas).

The concept of the social city is supported by a powerful awareness of the environment, ideas about the natural prerequisites for existence, re-use, etc. Since attention is paid to the specific socio-economical role of neighbourhood communities in a larger spatial context, this concept can m a k e an important contribution to improving the cities. The possibility of producing permanent green spaces is one of the major elements of this concept.

The meaningful city, finally, envisages the possibility of deriving the identity of urban structures visually, and/ or linking them with the structure of the landscape, and regards urban green space as an important visual element in rendering cities comprehensible: the inhabitants' utilizing and experiential possibilities are paramount in this approach, al­though previous experience, such as with nature construction, m a y also be resorted to.

Planning tools Various planning tools have been developed in the Netherlands for implementing concepts as described in the previous section.

In line with national policy for physical planning, regional and structural plans must and/or can be drawn up. These can enforce measures for a proper location pattern of activities in relation to traffic planning, the realization of a particular area for urban vege­tation, and so forth. M a n y urban renewal plans involving physical planning tools are n o w

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making provisions for green parks and routes. Larger parks are being created on the edges of cities.

Within the physical planning framework, the urbanization report of 1978 and other national structural outlines and schemes and the 1985 multi-year forestry plan have led to a plan for «Randstad vegetation structure». This distinguishes areas of consolidation, adaptation and restructuration. In collaboration with regional government, these areas are being worked out in detail. About forty projects of this kind are currently in operation.

The plan envisages the planting of forests in the windy restructurization areas on the edges of the cities of the West Netherlands, combined with building residential and work­ing areas. Together with, for instance, provincial and urban plans for cycling and horse-riding routes, nature spots accessible to all in urban areas can be ensured. In adaptation areas small recreation projects can be realized. At a national level an environmental plan and an environmental implementation plan are in preparation, to be issued in 1987. The plans constitute a coherent approach to environmental management. Environmental rene­wal is already being anticipated by the reduction of waste flows, overacidification and dehydration, by less intensive use of fertilizers, and the reduction of all kinds of other environmental risks, noise nuisance, etc. Regional environmental plans, which are n o w compulsory, will, once they are enforced, enable special demans pertaining to environmen­tal hygiene to be made for certain areas —cities, for instance—. The regional environmen­tal plans will also form a framework for better management of specific components of the environment, local water quality management, for example.

Local environmental implementation programmes (for which the state can provide a 50 por 100 subsidy) offer municipalities the opportunity to develop initiatives for improving the environmental health and ecological quality of the cities. It is not so m u c h the lack of legislative instruments as of initiative and/or expertise that leads to settlements which function less well in an ecological sense. However, the establishment of large public parks in the inner cities is unfortunately being held up by the current funding structure of the Randstad park plan.

A number of cities n o w have, or are preparing, a park structure plan for the entire urban area. Such plans can highlight management and costing issues (as in the Delft plan), utilization, combined or not with management, energy consumption and climate (as in The Hague plan), or focus on the experimential value and visual aspects of green spaces (as is the case in Amsterdam).

Comparative studies allowing the advantages and drawbacks of different planning methods to be examined more closely will in future show what approach is the most sen­sible. In all the methods, frankness, public participation and the right to have a say play an important part. There are special forms of publication in the Netherlands for this, includ­ing films and meetings and specially developed design methods.

Conclusion

The history of the Dutch city has left us with m u c h valuable open green space. The expan­sive growth of the cities in the last century has also given us numerous handsome gardens situated on the old bastions and pleasant public parks and garden villages.

Rapid urbanization has finally resulted in urban decay. For the past fifty years, city parks have been mainly regarded as recreational areas.

W a y s and means are currently being sought to renew the cities; within this scope other dimensions of urban vegetation which have lapsed into forgetfulness for a time in the Netherlands but which are fundamental, m a y be considered: resource management and quality of natural eco-systems, socio-cultural and visual aspects. Older natural m a n - m a d e green spaces can form an important element.

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PROBLEMS AND PROGRAMMES CONCERNING THE USE AND THE EDUCATION

ABOUT THE URBAN GREEN AREAS. THE CASE OF ROME

Hi lda S e l e m

The «case» of R o m e is about the case of several other European towns, where the prob­lem of the «green» as a whole, is the result of an historic process which, on a specific geo-morphologic framework, has seen the intervention of a «natural» or «artificial» vegeta­tion modified, destroyed substituted by m e n for his various needs. The general reference, therefore, is offered both by geo-morphologic and vegetal nature and by h u m a n interven­tion transforming it; namely by the history of the physical structure and of the transforma­tion of the town, including the «green» problem. ' Historic research is therefore the basic starting point for any culturally acceptable proposition, which has to be considered case by case, according to the identity and the value of pre-existing elements, which can consist of ruins or archaeological remains such as aqueducts, catacombs or of particular environmen­tal characters. Historic research, is furthermore the basic ground of propositions for green areas to be «requalified» according to their vocation, to be used in different ways or to be settled «ex-novo»; it is also the method of approaching and judging the different green areas such as parks —both urban and extra urban—, urban Villas —both historic and of any peculiar character—, neighbourhood green and all the green wich is part or the con­nective framework of the city.

It is obvious that the historic framework refers also to the environmental, social, eco­nomic, h u m a n framework, that is the systemic framework.

W h a t is peculiar of the «case» of R o m e is the fact that for more than hundred years there has not been an environmental education; there has not been relationship between h u m a n factors and environmental factors and m a n has not been considered as the top element of integration between nature and culture; in other words there has not been an environmental consciousness. This fact, together with the growth of the city of R o m e (200.000 inhabitants in 1870 provided to be 4.000.000 in 1990) and the lack of interest by politicians about green and environmental problems, speculation and short-sighted atti­tude by the power, produced as a result the destruction of huge extension of green areas —private villas inside the roman vails— and of an enormous amount of sq. meters of open-agricultural green-outside the walls. The whole skyline of R o m e has been altered and spoiled: the green framework of patrician villas inside the town and the «vigne» flourishing both inside and outside the walls, together with the rural character pointed by the rythm of the aqueducts of the «campagna romana» have disappeared.

In the last ten years, finally, there has been an increase of interest for the problem of green areas: a few figures are necessary to prove such a statement. In 1976 a research done by C N R stated that the amount of green in R o m e , including the historic Villas, was of 629 ha, that is 2,18 S q M pro capite for daily use for a town of 2.883.966 inhabitants; including the park of Castelfusano, squares and flower beds, one reached a total figure of 2.000 ha, that is 6,93 S q M pro capite. In 1986 one has reached the figure of 3.428 ha of green, that is totally 11,5 S q M pro capite. In other words, in ten years one has acquired

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38,50 % of green; a further increase of 622 ha, that is a further 16 % is provided for the next three years, which is still a very low figure compared with the one provided by the Planning Acts of 20.000 ha. The new balance between the built-in town and the non-built environment can be searched in the great territorial green systems both at metropoli­tan scale with a potentiality of about 10.000 ha and at urban scale with a potentiality of about 5.000 ha. O n e has to remember that 375 ha of the 3.128 above mentioned belong to the great historic villas (urban level) and 176 belong to the remains of XIX th century villas (sub-urban level). Such elements, besides their usable value of 1/6 of total green, represent an important m e m o r y from the historic-landscaping-architectural point of view and a consistent element of «inter-face» between the various built-in urban zones, therefore they

-play an important role in the overall town-balance. For the minor historic villas there are already four designs and the budget of 8 M L D has been assigned to such projects. Finally, for the better use and management of small green areas of 1.000 to 5.000 S q M there has been a national competition for 48 areas in different locations, from the historic centre to the periphery. The new architectural settlement, has the aim of providing new uses, new designs, new «signs» for the town, considering the green as a new framework, a new link, a new social space, «the new hope», after the failure of industrial era ideal or the town at h u m a n scale, for a town at environmental scale of post-industrial era.

It is quite obvious that, in order to reach such aims, one has to acquire political will, correct administration, technical capacity, h u m a n and economic sources. O n e has also to acquire the consciousness that «green» is a preliminary right for citizens to total environ­ment, to acquire the right for participation to the management of «green» and, first of all, contributed to its protection. Several programmes have been carried on such premises in order to involve, inform and educate the citizens, such as écologie campaigns in schools, competitions for blossomed balconies, «green finger» courses, old people involvement and finally, for the first time, the possibility for any adult subject, to become an agent respon­sible for direct keeping and preserving from vandalism the green areas. Besides this fact, again for the first time, Municipality and University are working together to produce de­signs to be carried out and to be realized on a budget already allowed.

At this point there are some general considerations to be kept in mind: 1. Demographic factor: birth decrease and moving of the remaining pressure towards

the surrounding municipalities. Such situation is provided to be increasing until 1995, when national demographic stability will be reached and population of big towns will decrease of about 10 % (according to the general census of 1981).

2. Completion of programmes for low-cost housing and of plans for primary infras­tructures: that will allow for considerable economic sources to be spent for the environ­ment, for the «green», for leasure, for sport equipments, for culture.

3. The change of the structure of the city: due to the factors above mentioned, the monocentric and concentrated city is become a policentric and wide-spread city, where the new linking texture will be provided by the green spaces, and there will be no more diffe­rence between town and country.2

4. The different social order with the increase of adults and aged persons: for such cathegories, it is necessary to provide facilities for relax, leasure and community life.

5. The increasing mass consciousness for the environment: due to the increase of level of life, the «standard» concept of the sixties has become obsolete: the m i n i m u m of «green» for each citizen provided by then, has to be adapted to more diverse and richer opportuni­ties and structures in order to improve the «quality» of services and of the environment, that is the «quality» of life.

6. The prevailing of the idea of an integrated system of «green» and of meeting points over the hierarchical schemes of the sixties («neighbourhood green»; «ward park»; «urban sector park» a.s.o.) when the green areas were cut off from the activities of the city, distributed according to a hierarchic pyramid having on its apex the great territorial park and on its base the «neighbourhood green». In the contemporary city people are moving daily about 10/20 k m to reach their working place and life environment sometimes over­comes the limits of the city itself. Differences of use between various social cathegories won't exist anymore in a levelled society.

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Wich are the strategies to be adopted in order to suit the needs of a more articulated city?

First of all the strategies of green areas have to be considered into an overall picture of requalification of the city, into a policy of breaking the existing dichotomy between central and peripheric areas in order to improve new, wide-spread, more complex and various interrelationships capable to qualify different environments. Particularly in central areas a net of «green axis» should connect the «green squares», integrating them to the system of historic parks. The historic villas should be considered as living museums to be used by the citizens. In border areas in the wide-spread city, one should proceed on an articulated strategy re-distributing activities such as «green», work, culture, leasure, shopping into a complex integrated network of nodal areas spread into the urban structure. In the «belt» of municipalities surrounding the City, one should re-distribute some central activities like trade, education, information, etc., performing a great natural system of re-balance inter­connected to the urban green structure.

The experiences which have been carried on up to n o w allow us for some hypothesis of prior intervention: protection of historic green; realization of sectorial parks of about 50 to 150 ha; settlement of green areas in new residential nucleus. Such areas consist of about 566 ha and the programmes provide a further increase of some more 190 ha. Finally one should operate with new juridical, planning performing instruments in order to achieve the 10.000 ha of territorial green designed to be reconnected to the 80.000 ha of agricultural land and the system of regional parks. It is quite obvious that to get deeper into the knowledge of environmental sources it is necessary to create a new structure of competen­cies dealing with the environment new technical and effective structures for a pluri-annual program considering the «green» as a basic element for the city of 2000, avoiding the uncontrolled power of private interests and of spontaneous growth.

At the end, I would like to say that w e should think of the inhabitants of the city of R o m e as real actors and not mere spectators of that «urban scene» which is the city, a city conceived as a system of communication and of cultural exchange in an unified perspective of «cultural good» in continuous transformation. The space w e are living in should become the expression of the society in its various aspects.

B I B L I O G R A F Í A

S E L E M , H . : «The system of roman for treeses as an urban structure of open spaces, services an archaeological remains». Urban ecology applied to the city of Rome. MAB-Italia Project II, R o m a , marzo de 1979.

TlBUZZi, M . : «Observations on the historical pattern of events in the roman parks». Urban ecology applied to the city of Rome. MAB-Italia Project II, R o m a , marzo de 1979.

S E L E M , H . : // sistema deiforti di R o m a nella lógica dell'ecosistema urbano per il riuso del costruito. R o m a , ed. Bulzoni, 1979.

S E L E M , H . : «The environmental, historical-architectural existing patrimony and its poten­tialities of re-use in the north-western area of R o m e » . Urban ecology applied to the city of Rome. MAB-Italia Project II, Progress Report n . s 2, R o m a , septiembre de 198 í.

L'insoddisfazione ambiéntale negli insediamenti umani. Seminario di R o m a , octubre de 1979.

Ecología. Actas del I Congresso Nazionale della Societá Italiana di Ecología. Salsomag-giore Terme, 21-24 de octubre de 1980.

Understanding the Museum environment: assurvey of seven museums in Rome. Julio de 1982.

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Aspetti vsocio-spaziali» della rappresentazione cognitiva del centro anadino. International Conference on Environmental Psychology, Guilford, Gran Bretaña, 1979.

L'immagine del «bene cultúrale» come aspetto del rapport o individuo-ambiente: uno stu­dio esplorativo. Rapporto técnico W . 298, 1981.

The Museum visit within and environmental psychology framework: a critical review of the littérature. Rapporto técnico 290, 1980.

Citizen involvement in the management of the urban vegetation as related to cultural heri­tage of the urban population. Estudio piloto: «Latin people and trees», abril de 1982.

Survey of citizen's views on trees and green areas management. Faculty of Forestry, Uni­versity of Toronto.

Public involvement as a key factor in nature preservation. Abril de 1982. Inquinamento da rumore. Octubre de 1979. Esperienze di pianificazione urbana e territoriale. Julio de 1979. Photo chemical oxidants in the Rome Metropolitan area. Diciembre de 1978. La citta come sistema. LVI riunione, Lecce, 11-14 de noviembre de 1981. Valutazione delle emissioni nel trattamento biochimico dei rifiuti solidi urbani. I quaderni

nella SLIA, 1980-1982. Programas en el sector de la cooperación. Nota informativa, junio de 1982. Modernas orientaciones sobre los problemas de planificación y administración de los

recursos hídricos. Quito, 14-18 de marzo de 1983. La foresta tropicale e l'uomo. Tavola rotonda, R o m a , 17 de septiembre de 1981. Rapporti dell 'azienda tranvie e autobus del comune di Roma. 1980. lómate di lavoro airo. 1978. Planta dei settori di chiusura del centro storico. R o m a , 26 de enero de 1977. // recupero degli insediamenti abusivi. U S P R Documenti I, marzo de 1981. Proposte organizzative della rete viaria primaria. U S P R Documenti II, marzo de 1981. II piano per l'edilizia econoomica e popolare. U S P R Documenti III, octubre de 1981. Urbanística per il verde pubblico. U S P R Documenti IV, enero de 1982. Indirizzi per l'attuazione di una política edilizia e urbanística. Actas del Convegno Nazio-

nale di Architettura: «II rinnovo urbano», R o m a , 1980. Proposte per una metodología di studio relativa agli intervenu su i centri storici. Actas del

X I V Congresso Nazionale di Storia dell' Architettura, R o m a , 1965. Le trasformazioni per il recupero del patrimonio edilizio esistente. Congresso Nazionale di

Architettura 1979, R o m a . GuiDUCCl, Roberto.: Un mondo senza tetto. Ed. Laterza, 1980. // rinnovo urbano e L'attuazione del sistema direzionale orientale di Roma. Actas del

Congresso Nazionale di Architettura, R o m a , 1981. S E L E M , H . , et. alii: Problemi di piano regolatore e sociali della periferia urbana. Atti del

Convegno di Lavoro, Hannover, 1981. «Attività della provincia di R o m a per il recupero dei beni architettonici». Dall'abandono al

riuso. Ed. Savelli, 1981. Roma e la sua area metropolitana. Actas de la II Conferenza Cittadina sui Problemi

Urbanistici, R o m a , 26-29 de marzo de 1981. Atti del Convegno Internazionale «Ville Storiche '85. Problemi e prospettive», R o m a , 22-

24 de abril de 1985. Atti del Convegno «Verde e Ambiente», R o m a , 18-24 de abril de 1985. A . U. Rivista dell' Arredo Urbano, n ú m . 15-16, 1985. Roma citta e piani. Ed. Urbanística, Turin, 1971. B E N E V O L O , L . : Roma da ieri a domani. Ed. Laterza, 1971. INSOLERA, I.: Roma moderna. Ed. Einaudi, 1971. Ville storiche '85. Atti preliminari del Convegno. 22-24 de abril de 1985. Forma. La città antica e il suo divenire. Ed. D e Luca, octubre-noviembre de 1985. Roma. Studio per la sistemazione dell'area archeologica centrale. Ed. D e Luca, 1985.

Lavori e studi di Archeologia pubblicati dalla Soprintendenza Archeologica di R o m a , a cura di L . Benevolo, A . Cagnardi, F . Castagnoli, V . Gregotti, I. Pizzetti, C . Podestà e G . Zambrini.

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NOTAS

1. It is important to observe that any research in R o m e has to be traced in the continuity of life of the different places, so that the historical m e m o r y keeps its original «form», which has to be considered as the matrix of any idea and of any proposition.

2. There is an increasing flow in R o m e towards the sea, towards south-East and North-West and towards the bordering boroughs. The centre of R o m e has lost in the last 10 years about 150.000 inhabitants, while the hinterland has grown of about 120.000 units: it is the matter of a discontinous development, at a low density, but at a high use of space. The result of this has been a process of redistribution of minor activities, such as shops, handicrafts workrooms, public services. Therefore the city of R o m e represent a very complex variety: a great urban area where urban spaces are getting more and more differentiated, needing of an overall design of diversified articulated strate­gies. At the contrary, there is a concentration process in central areas where all the institutional bodies, political and trade unions representative offices, information and credit agencies are increas­ing. Without a contemporary policy of re-distribution of such activities and of their integration with the green areas, there is very little to do in order to improve the urban quality of peripheric areas.

In other words, the centripetal and contemporarily the centrifugal impulsion and the increasing mobility of citizens ask for a deeper integration of urban activities, for a progressive diversification of the ways of living. There is in fact no more need for great uniform areas —great urban parks, great «centri direzionali»— which tend to provoque degrading phenomena of the urban quality in their surroundings, lack of relationship and exchange between the different activities; but there is instead the need of a wide-spread system of network of focal points and of green points of equal importance even if composed of mixed services and activities.

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AREAS VERDES EN LAS CIUDADES, EL EFECTO DE SU CONTAMINACIÓN, SU MONITOREO

Y BIOINDICACION. ESTUDIO DEL CASO DE BUDAPEST

Attila Borhidi G y u l a Biczók Edit Farkas Pal Klincsek

Instituto de Ecología y Botánica de la Academia de Ciencias de Hungría

Introducción

Budapest, la capital de Hungría, tiene 2.100.000 habitantes, en un territorio de 525 k m 2

de extensión, con una densidad de población de 4.200 habitantes/km2. Su altitud fluctúa entre 110 m a nivel del río Danubio y 525 m a nivel del mar. La particularidad geográfica de esta ciudad es que es la única metrópoli del continente europeo atravesada por un gran río, el Danubio, cuyo ancho varía a lo largo de su trayecto entre 350 m y 1 k m . Mientras la parte oriental de la metrópoli —la ciudad histórica de Pest— fue construida sobre un terreno llano aluvial del Danubio, la parte occidental —la ciudad histórica de Buda— emerge sobre un terreno ondulado formado por varias lomas y cordilleritas que permiten hermo­sas vistas panorámicas sobre la ciudad. La capital está rodeada por 44 pueblos de distinto tamaño, entre ellos cuatro ciudades más pequeñas, que forman un anillo de aglomeración con 350.000 habitantes.

Reseña histórica

La ciudad tiene una historia de dos mil años, ya que fue capital de la provincia de Panno-nia, perteneciente al Imperio R o m a n o , denominándose entonces Aquincum. Restos de muros de sus edificios, acueducto, anfiteatro, columnas y mosaicos finos de los patios se han conservado bastante bien. La capital actual se estructuró como dos ciudades indepen­dientes separadas por el Danubio hasta la segunda mitad del siglo pasado. Buda, por sus ventajas estratégicas, se convirtió en la sede de los reyes húngaros a partir de la segunda mitad del siglo XIII, desarrollándose de forma más dinámica que Pest, situada en la ribera izquierda del Danubio. La construcción en 1843 del Puente de Cadena —diseñado por A d a m Clark, el mismo ingeniero británico que diseñó posteriormente la famosa Tower Bridge de Londres— posibilitó la unión de las dos ciudades, realizada en 1875. La época del gran desarrollo de la capital tuvo lugar entre las décadas de 1880 y 1890 con vistas a la celebración del milenario de la fundación del Estado húngaro, en 1886. A partir de enton­ces se formó el sistema de las grandes avenidas y se construyeron cientos de palacios y edificios públicos y oficiales siguiendo diferentes estilos: neoclásico (Museo de Bellas Artes), neogótico (Parlamento), neorrenacentista (Academia, la Opera, Palacio Real),

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neobarroco (catedral del San Esteban) y ecléctico. Debido a esto, los edificios de Budapest presentan un aspecto m u y similar a los de otras grandes metrópolis europeas c o m o París, Viena, Madrid, etc. Durante la Segunda Guerra Mundial, Budapest fue seriamente afec­tada por los bombardeos: el 70 por 100 de las viviendas fue total o parcialmente destruido, y todos los puentes, destrozados. Tras la conflagración comenzó la reconstrucción de la ciudad, continuada después en una nueva etapa con la construcción de numerosos edificios modernos.

Bioclima

Budapest se encuentra, desde el punto de vista climático, en la confluencia de tres tipos de clima:

a) El clima de Europa central, lluvioso durante todo el año, y sin fluctuaciones ex­tremas de temperatura.

b) El clima submediterráneo, con inviernos suaves, veranos secos y lluvias en m a y o y octubre-noviembre.

c) El clima continental, caracterizado por una gran fluctuación de la temperatura, inviernos fríos y veranos y otoños m u y secos.

L a frecuencia de los años caracterizados por los distintos tipos climáticos fue la siguiente entre 1870 y 1950:

a) centroeuropeo 24% b) submediterráneo 38% c) continental 24% d) atípico 14%

El ambiente urbano ejerce varias influencias sobre el mesoclima del interior de la ciu­dad. L a calefacción utilizada durante la estación fría produce una contaminación térmica del aire, con lo que resulta un promedio anual de entre 1 ° C y 1,5 ° C más alto en el centro que fuera de la ciudad. Las diferencias m á s significativas entre el macroclima y el meso-clima urbano quedan claras en la comparación de los datos de dos estaciones de Budapest:

Macroclima

Observatorio Nacional (Budapest, Lórinc)

Mesoclima urbano

(Budapest, Madách tér)

Temp. prom, anual/ ^ C

10,5

11,6

Lluvia prom. anual / mm

537

570

Meses secos

3

3,5

Meses áridos

1

El balance hídrico del clima presenta una deficiencia de 120 m m anuales, mientras que en el centro de la ciudad la deficiencia es de 240 m m , aunque tenga 30 m m más de precipi­tación que la periferia de la ciudad.

Las tendencias de cambio del mesoclima urbano se manifiestan claramente si compa­ramos los elementos climáticos medidos en las mismas estaciones durante la época del desarrollo paulatino (1901-1950) y en el período de la explosión de la urbanización (1956-1970).

E n la tabla anterior se observa claramente que en los últimos años del desarrollo urbano, el mesoclima resultó más seco, incrementándose también la intensidad de la sequía y la duración de la estación seca incluso en aquellas áreas en las que aumentó la cantidad anual de lluvia. Esto significa que el ambiente urbano dio lugar a una reestructuración en la distribución estacional de las precipitaciones lo que, a su vez, influye en la vegetación

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natural; ésta responde m u y sensiblemente al cambio del mesoclima, debido a que la ciudad se encuentra en la frontera de dos zonas vegetales distintas. E n la llanura encontramos una selva esteparia en la que la vegetación está compuesta por un mosaico de robledales (Quer­em robur) y estepas secas pobladas por especies de Festuca, Stipa y tomillos. E n el área colino-montañosa dominan los robledales de Quercus petrae, Q. cerris y Q. pubescens, además de bosques mesófilos de roble (Quercus petrae) y carpe (Carpinus betulus). Se puede observar que durante los últimos treinta años la zona silvo-esteparia ha penetrado de forma importante en el área colino-montañosa, a consecuencia de la extensión de las áreas de construcciones y repartos nuevos establecidos en la zona de bosques. Actual­mente, la frontera de los bosques cerrados se encuentra 200 m más alta que en la situación anterior. C o m o consecuencia de este proceso, algunas áreas boscosas del interior de la ciudad han perdido de forma notable el efecto suavizante anteriormente experimentado sobre el mesoclima de la ciudad.

Contaminación del aire y su bioindicación

Los distritos de Budapest situados al norte, este, sureste y sur de la ciudad son los más industrializados, debido a lo cual el aire de estas zonas se encuentra más seriamente con­taminado por S 0 2 , C O y N O C o m o la mayoría de la contaminación atmosférica está originada por la calefacción, el aire de los distritos centrales está también bastante conta­minado, sobre todo por S 0 2 , porque el carbón utilizado para este fin tiene un alto conte­nido de sulfuro. E n el centro y la parte sur de la ciudad el contenido de S 0 2 del aire sobrepasaba el valor de 60 m g / 1 0 0 horas durante los meses del invierno, mientras que en verano los valores más altos variaban entre 20 y 30 m g / 1 0 0 horas (datos de la década de 1960). A partir de los años setenta el sistema antiguo de calefacción fue sustituido por otro de gas, con lo que la contaminación del aire disminuyó a la mitad.

Para la bioindicación de la contaminación del aire utilizamos varios métodos. Debido a que los liqúenes responden m u y sensiblemente a la concentración del S 0 2 del aire, se utilizan ampliamente para este fin: la ausencia de liqúenes indica siempre la extensión de las áreas más contaminadas de las ciudades. E n Budapest se confeccionó un m a p a de distribución de los liqúenes (Farkas y Verseghy 1984, Farkas et al. 1985), y se encontró que las áreas densamente edificadas carecen completamente de liqúenes. Esta área, considerada como desierto de liqúenes, abarca más de los dos tercios del territorio de la capital. Alre­dedor de éstas, se hallan dos zonas intermedias, consideradas c o m o zonas de lucha de los liqúenes, caracterizadas por una flora de liqúenes incompleta, con una a doce especies. E n la zona intermedia interior, que es la más contaminada (área de la Isla Margherita, L o m a San Gherardo) se encuentran los liqúenes Lecanora piniperda y L. hageni, mientras que en la zona exterior y menos contaminada, Lecanora sarcopis, L. subintricata y L. lucida fueron consideradas c o m o especies bioindicadoras. La cuarta zona, considerada c o m o normal, con una flora de liqúenes completa, se encuentra únicamente en la parte monta­ñosa del noroeste y oeste de la ciudad.

Los liqúenes, al poseer una gran superficie, son capaces de acumular muchos agentes contaminantes del aire. Debido a esto, algunas muestras de liqúenes han sido trasplanta­das a las áreas seriamente contaminadas, donde los liqúenes no pueden sobrevivir, utili­zándolas para medir la concentración de los contaminantes acumulados por ellas. C o m o área de control para estas investigaciones se utilizó el Jardín Botánico de la Academia de Ciencias en Vácrátót, situada a 37 k m de distancia, al norte de Budapest. Muestras tras­plantadas en cincuenta puntos de Budapest fueron analizadas para averiguar su contenido de plomo, cadmio, manganeso y cinc. La distribución de los valores altos (entre 100 y 271 ug/g) del plomo tiene una correlación estrecha con la red de las avenidas y calles de mayor tráfico. Los valores altos de cadmio (entre 3,0 y 5,2 ug/g) están correlacionados con las áreas industriales y depósitos de desecho. L a contaminación de magnesio tiene una distri­bución dispersa relacionada directamente con las localidades en las que se realizan repara­ciones del gaseoducto. Valores más altos (entre 50 y 111 ug/g) sólo fueron encontrados en Pest.

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Para estos estudios fueron utilizadas especies xerófilas de liqúenes c o m o Hypogymnia physodes y Cladonia convoluta, teniendo en cuenta el clima seco de Budapest. Prestamos atención al hecho de que las especies distintas tienen una eficiencia de acumulación dife­rente. E n el mismo lugar, los tallos de la Cladonia convoluta acumularon una cantidad de contaminantes tres veces mayor que las muestras de la Hypogymnia physodes.

Para cada una de las zonas climáticas y vegetales es necesario encontrar los organismos más adecuados a los fines de la bioindicación. E n las zonas secas, por ejemplo, las posibi­lidades de la bioindicación parecen m á s limitadas que en los países de clima h ú m e d o . Por esta causa, resultó infructuosa la bioindicación de la contaminación del aire mediante brió-fitos en Budapest. U n método para la bioindicación del aire mediante muestras trasplanta­das de Sphagnum es ampliamente utilizado en los países de Europa septentrional y occi­dental. Pero debido a que todas las especies del género Sphagnum son m u y raras y se encuentran estrictamente protegidas en Hungría, intentamos la utilización del Bryum argenteum, una especie ubicuista y xerotolerante. Los estudios preliminares (Pócs, Kis y Biczók 1985, inédito) revelaron que la actividad de acumulación de esta especie se encuen­tra más estrechamente relacionada con la calidad del sustrato que con el aire.

Bioindicación del ambiente urbano por árboles y arbustos

Los árboles y arbustos que crecen en los parques y por las calles también acumulan ele­mentos contaminantes del aire y del suelo, absorbiéndolos por sus frondes, junto con los elementos nutritivos que absorben por su sistema radical. Este tipo de acumulación da como resultado un espectro complejo de todos los contaminantes existentes en el medio ambiente urbano.

Los árboles y arbustos que acumulan macro, micro y ultramicro elementos en mayor cantidad resultaron ser los siguientes (after Kovács et al. in Borhidi et al. 1981):

Especies

Rosa rugosa Thuja occidentalis Aesculus hippocastanum Koelreuteria paniculata Sophora japónica Robinia pseudoacacia Morus alba Acer platanoides Celtis occidentalis Tilia tomentosa Platanus acerifolia Ailanthus glandulosa

Número de elementos acumulados en área urbana

53 52 50 47 45 45 44 43 43 43 40 39

del control

43 44 49 45 42 36 39 44 44 37 40 39

Las hojas de las especies arbóreas acumulan los elementos individuales en cantidad diferente, dependiendo de la concentración existente en el biotopo donde crecen. Por tener esta capacidad, ciertos árboles son aptos para detectar el aumento de los elementos conta­minantes e indicárnoslo. Los acumuladores m á s potentes con respecto a los contaminantes más frecuentes son las especies siguientes:

Pb: Sophora japónica, Celtis occidentalis, Tilia tomentosa, Ailanthus glandulosa. C u : Ailanthus glandulosa, Tilia tomentosa, Celtis occidentalis. Zn: Acer platanoides, Aesculus hippocastanum, Ailanthus glandulosa, Celtis

occidentalis, Robinia pseudoacacia. M n : Acer platanoides, Aesculus hippocastanum, Celtis occidentalis, Platanus

44

acerifolia, Robinia pseudoacacia, Sophora japónica, Syringa vulgaris, Tilia tomentosa.

Sr: Acer platanoides, Aesculus hippocastanum, Celtis occidentalis, Platanus acerifolia, Syringa vulgaris, Tilia tomentosa (véase: Kovács et al. in Borhidi et al, 1981).

Es fácil observar que un análisis de los elementos acumulados en las hojas o en la corteza de un árbol constituye una información válida en un momento determinado sobre la cantidad de los contaminantes. Para tener una idea sobre el dinamismo de los contami­nantes hay que conocer su migración y el flujo provocado por las lluvias —frecuentemente acidas— que disuelven una parte de estos materiales de la fronda y corteza de los árboles, y de los suelos. Es necesario conocer la «capacidad y memoria químicas» de la corteza y suelos, es decir, su capacidad acumulativa y el índice de retención con respecto a los con­taminantes. Experimentos de modelo revelaron (Biczók, 1985; inédito) que la corteza de la Robinia pseudoacacia pierde el 20-25 por 100 del contenido del plomo acumulado en forma diluida o suspendida por una lluvia acida después de diez minutos de tratamiento. Sin embargo, alrededor del 50 por 100 del plomo acumulado se queda fijado en la corteza, c o m o memoria química.

Los suelos analizados en Budapest —suelo arenoso y arena margosa, respectivamen­te— resultaron poseer una «memoria química» de dos a tres veces más duradera que la corteza de la Robinia. E n los suelos, la cantidad de los contaminantes perdidos es mucho menor y el proceso de la disolución misma es también mucho más lento.

Contaminación de los suelos urbanos

El proceso de contaminación de suelos urbanos más frecuente es la salinización y alcalina-ción provocadas por el vertido de sal —cloruro de sodio— realizado en invierno en los países fríos, o la causada por el riego insuficiente de los parques durante la sequía estival en los países calientes. A m b o s tratamientos crean biotopos desfavorables para el cultivo de numerosas especies de árboles y arbustos ornamentales, que no son capaces de tolerar el aumento de contenido en sal.

E n Budapest, la temperatura en invierno oscila diariamente alrededor de 0 Q C , cau­sando la descongelación parcial de la nieve durante el día y la congelación masiva por la noche, efectos que convierten las calles en auténticas pistas de patinaje sumamente peligro­sas para el tráfico de los vehículos. La sal obstaculiza la congelación de la precipitación, pero la solución salada producida por este tratamiento penetra en el suelo, donde la sal se acumula. El componente más agresivo de la sal es el ion de cloruro, que, absorbido por las hojas de las plantas, paraliza la fotosíntesis, provoca la actividad respiratoria de las célu­las y causa una deficiencia de oxígeno gravísima en ellas hasta la desintegración completa de los procesos metabólicos (Biczók, 1985, inédito).

Ensayamos la tolerancia de sal en el caso de más de cincuenta especies de árboles y arbustos mediante experimentos de terreno y gabinete recíprocos (Török in Berczik et Borhidi, 1979, Klincsek 1986 a, b). Se encontró que la estrategia de la absorción y acumu­lación del ion de cloruro es completamente diferente en los árboles tolerantes y no toleran­tes a la sal, respectivamente. Las especies tolerantes a la sal son capaces de controlar automáticamente la absorción del ion de cloruro, y absorben una cantidad despreciable, mientras que las especies sensibles a la sal no pueden limitar la absorción del cloruro.

El efecto del cloruro resultó menos perjudicial cuando utilizamos cloruro de potasio o cloruro de magnesio en lugar de cloruro de sodio. Para aliviar el efecto perjudicial de la sal resultó bastante eficaz el uso de una mezcla de cloruro de sodio y sulfato de calcio, efec­tuando un riego abundante de los parques y las calles al principio de la primavera, antes del brote de los árboles (Biczók in Borhidi, 1985).

Experimentamos también que el efecto de los gases contaminantes del aire (S0 2 y H F ) reforzaron el efecto de la sal, causando daños más violentos y masivos de manera acele­rada en las hojas de los árboles sensibles (Klincsek, 1986 6).

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Según la tolerancia del cloruro, las especies arbóreas estudiadas pueden ser clasificadas en los grupos siguientes:

a) Géneros con especies de tolerancia alta: Ailanthus, Betula, Celíis, Crataegus, Elaeagnus, Gledisia, Robinia, Sophora, Taxus, Tamarix; especies ulteriores m u y toleran­tes: Pinus contorta var. murrayana, Fraxinus angustifolia, Quercus robur, Q. palustris.

b) Géneros con especies moderadamente tolerantes: Buxus, Catalpa, Cotoneaster, Eucommia, Koelreuteria y Prunus avium, Pupulus alba, Ulmus minor, c o m o especies concretas.

c) Géneros y especies ornamentales no tolerantes a la sal: Acer, Aesculus, Corylus, Ginkgo, Juglans Lonicera, Phellodendron, Picea, Populus (sección Aigeros), Populus bal­sama, P. nigra y sus híbridos, Tilia (Klincsek, 1986, a, b).

Recomendaciones

1. Se recomienda iniciar un proyecto internacional para determinar los parámetros ecológicos más significativos del ambiente urbano, con vistas a la reforestación de las ciudades.

2. Se recomienda iniciar los requerimientos ecológicos y factores limitantes de las especies arbóreas utilizables en las ciudades de distintas zonas climáticas y vegetales.

3. Hay que tener en consideración la exigencia ecológica y la tolerancia de los árbo­les, y las tendencias micro y mesoclimáticas urbanas en la reforestación de las ciudades.

B I B L I O G R A F Í A

B E R C Z I K , A . , y BORHIDI, A . : Problemas ambientales y proyecto de investigaciones ecológi­cas de la Aglomeración de Budapest. M T A Biol. Tud. Oszt. Közl., 22:367-390. 1979. (En húngaro.)

BlCZÓK, Gy. : Problemas de la detección y modelaje del flujo de elementos potencial y actualmente tóxicos en los sistemas planta-suelo de la Aglomeración de Budapest. Talaj-kórnyezetvédelmi Szimp. Elóad. 1-6. Verócemaros, 1984. (En húngaro.)

BlCZÓK, Gy.: Respuestas fisiológicas de las células de la «Robinia pseudoacacia» al trata­miento del cloruro. Informe final del Instituto de Ecología y Botánica, Acad. Cien. Hung, sobre las investigaciones ecológicas efectuadas en el proyecto Aglomeración de Budapest (en Borhidi, A . , ed.), 1-44 Vácrátót. (En húngaro.)

BORHIDI, A . : El clima de Budapest y su cambio durante el desarrollo de la ciudad. Informe anual del Instituto de Ecología y Botánica sobre las investigaciones ecológicas efectua­das en el proyecto Aglomeración de Budapest (Borhidi, A . , ed.), 1-27. Vácrátót, 1984.

B O R H I D I , A . ; F E K E T E , G . ; K A T O N A , S.; K O V Á C S , M . , y V Á R K O N Y I , T . : «Qualification of the Urban Environment and some aspects of air pollution in the Budapest Agglomeration». In Stefanovits-Berczik-Fekete-Seidl: Man and the Biosphere; 10 years activity in Hun­gary. Budapest, 353-413, 1981.

F A R K A S , E . ; L Ó K O S , L . , y VERSEGHY, K . : Lichens as indicators of air pollution in the Budapest Agglometation. I. Air pollution map based on floristic data and heavy metal concentration measurements. Acta Bot. Hung . 31:45-68, 1985.

K L I N C S E K , P.: Cl-ion Gehalt und ihre Verbreitung in verschiedenen Stadt-Gehölzen. Acta Bot. Hung . 32, 1986. : Efectos de la contaminación de cloruro y S02 sobre las plantas arbóreas de los

distritos urbanos cargados de tráfico intenso. Tesis doctoral. Budapest, 1-10, 1968. (En húngaro.)

47

KovÁCS, M . ; O P A U S Z K Y , I.; PODANI, J.; K L I N C S E K , P. ; D I N K A , M . , y T O R O K , K . : «Element accumulation in urban trees and shrubs; bio-indicators of heavy metal pollution in the industrial-urban environment». En: Borhidi et al: Qualification of the urban environ­ment and some aspects of air pollution in the Budapest Agglomeration. 1981.

P R O B Á L D , F.: Budapest városklimája. The urban climate of Budapest. Akadémiai Kiadó, Budapest, 1-127, 1974. (En húngaro.)

V E R S E G H Y , K . , y F A R K A S , E . : Untersuchungen der Luftverunreinigung im Gebiet von Budapest mit Hilfe der Flechtenkarlierung als Indikatoren. Annal. Univ. Eötvös L . , Budapest, sect. biol. 24-26:163-184, 1984.

48

EVALUATING URBAN FOREST STRUCTURE FOR MODIFYING MICROCLIMATE: THE DAYTON CLIMATE PROJECT

Rowan A. Rowntree Ralph A. Sanders Jack C. Stevens

US Forest Service, Syracuse, New York

In 1978, the city manager of Dayton, Ohio, invited the United States Forest Service's Northeastern Forest Experiment Station to use his city as a field laboratory to better understand h o w the urban forest system operates to modify the physical environment. The purpose of this joint effort was to develop scientific principles that could be applied to the management of urban forests in cities throughout the United States. Although the results oh the research will have application nationwide, the city of aayton had specific the pro­blems for which it wanted solutions: 1) s u m m e r air temperatures in the City Center signifi­cantly exceeded those in the surrounding rural areas, placing a burden on power supply; 2) the U S Environmental Protection Agency was looking closely at Dayton's air quality pro­blem and threatening to place strict constraints on metropolitan expansion and industrial operations; 3) surface runoff from rainstorms created problems for sewer systems and sewage treatment plants in addition to erosion and the washing of pollutants into the M i a m i River. These problems were individual thorns in the side of a Northern «snow belt» city trying hard to maintain itself as an attractive place to live and work.

A highly professional approach to Dayton's urban natural resource system was consis­tent with the pride they placed on their place in history as the location of the first full-time city manager, w h o planned for and ran the city on principles developed from a rational understanding of h o w the urban system worked and h o w it could be guided toward speci­fic goals. In 1978, Dayton representatives attended the First National Urban Forestry C o n ­ference in Washington, D C and learned that a new science was emerging —the rational management of the urban environment through an understanding of the structure and function of vegetation systems.

In most cities and communities vegetation is a dominant and renewable part of the environmental system. It is the one component of the urban system truly susceptible to management and that affects all other components of the system —micro and meso cli­mate, wildlife, soils, surface and ground water hydrology, low altitude air pollution, noise levels— to n a m e only a handful of over thirty aspects of urban operation influenced by the kind, amount, and distribution of urban vegetation.

The Forest Service responded to Dayton's invitation and designated the Northeastern Station's research unit on the campus of the State University of N e w York College O f Environmental Science of Forestry at Syracuse, N e w York, as the lead group in the Forest Service portion of the study. The broader aspects of the Dayton climate project, which involved the participation and cooperation of other Federal, State, and local agencies, including the University of Dayton, Wright State University, Wright-Patterson Air Force Base, the M e a d Corporation, Harvard University, Massachusetts Institute of Technology, and Antioch College.

49

The Forest Service research program focused on these questions: 1. W h a t is the structure of the urban forest system? 2. H o w does that structure influence micro and meso climate, especially surface

runoff and the urban heat island? 3. C a n modification of existing forest structure reduce problems of surface runoff and

heat island efforts? O u r intent was to generate principles that could be applied to other cities in the United

States. With the hope that results derived from our work in Dayton would be applicable elsewhere, it was important to have some idea of the range of conditions existing in A m e ­rican urban areas.

W e k n o w that cities are not all alike. Each city has its o w n personality. T o test for differences in urban vegetation structure, w e examined data for three cities in very diffe­rent environments, relying on a classification of metropolitan areas derived from regional ecological characteristics (Sanders and Rowntree, 1983): Dayton (in the «Eastern Deci­duous Forest Province»); Syracuse, N e w York (in the «Laurentian Mixed Forest Pro­vince»); and Sioux Falls, South Dakota (in the «Tall Grass Prairie Province»). For those cities, w e compared tree density (canopy coverage or crown density), which is an important dimension of urban vegetation structure. The results showed that average canopy coverage for the cities is very similar: Dayton, 22 percent; Syracuse, 24 percent; and Sioux Falls, 23 percent. This gave us hope that urban forest structures around the nation were at least similar enough to have a basis for generalization.

However, there are important differences, from one city to another, in the configura­tion of herbaceous and woody vegetation, and in the geographical distribution of land uses. T o illustrate h o w different cities can be —even cities that are thought to be quite similar— w e studied two places located in the same geographic area, having a similar natural setting, and sharing a c o m m o n history of development and evolution: Syracuse and Rochester, N e w York. A n analysis of these cities reveals that the pattern of vegetation —what w e have called the «structure» of the urban forest system— is explained largely by the history of land use development in any city. A n d , the historical pattern of land use in these cities follows closely the development of transportation facilities. The historical geo­graphy of these two cities reveals successive impacts of the Erie Canal era, overlain by a period of railroad development, then intraurban trains and buses and, finally, of course, the heavy-handed imprint of the automobile. W e found that these two similar cities have marked differences in vegetative structure.

For any city, the structure of the urban forest will be closely associated with the distri­bution of land uses and will display a configuration that reflects the history of interaction between two types of forces: those that tended to locate land uses in concentric rings and those that tended to locate land uses in radiating spokes out from the Central Business District ( C B D ) . A detailed analysis of the structure of Syracuse's urban forest shows this interaction manifesting itself as a fractured set of wedges and concentric bands.

Not that w e k n o w there are both fundamental similarities and important differences in urban forest structure a m o n g American cities, w e will present a series of steps that can be used to understand the present configuration of land use and cover types that m a k e up the structure of an urban forest system. R e m e m b e r that our objective is to descrive the present structure of an urban forest system and the extent to which it can be changed for the purpose of enhancing the h u m a n environment.

Step One: Divide the City or Community Into Subunits Units should be particularly suited to analysis, to management, or both. For example, census tracts offer an abundance of data that can be used to find relationships between measured vegetation characteristics and attributes of the population. But census tracts m a y not be useful as management units. In Dayton w e used «neighborhood units» (which are about the same size as census tracts) that contained m u c h of the socioeconomic informa­tion of census tracts but were already used by the city for planning and management purposes. The seventy-nine neighborhoods have political representation through seven «priority boards» which represent about ten neighborhoods each. These units were satisfac-

50

tory for analysis and management and allowed implementation of policies emerging from this research.

Step Two: Acquire Air Photography If the resolution is good, if they are color, and if they are in stereo, a scale of between 1:12,000 and 1:24,000 will be adequate. If any of these criteria are not met, the scale should be 1:10,000 or larger.

W e are experimenting with photographs taken at different times of the year.Wright-Patterson Air Force Base flew the photo mission over Dayton for us during the s u m m e r , when trees were in full leaf. This spring, w e flew a mission over Cincinnati to test a method of interpretation that uses bare-tree images. After interpreting about two thirds of Cincin­nati, w e feel that stereo bare-tree photos can be accurately interpreted for canopy density and land use to give a full picture of the urban forest structure.

Step Three: Map Land Use Polygons Within Each Subunit Establish the boundaries of conventional land use classes by using mylar over the aerial photos. If a community has a land use m a p , this can be the base for transferring «poly­gons» —which are spatial units of homogenous land use— to the overlays of the photos. Several useful publications are available to aid in identifying and bounding land uses in the absence of an established land use m a p (Avery, 1977; Pownal, 1950). Polygons should be confirmed by ground identification if land use mapping is being done for the first time.

Step Four: Identify Cover Types For Each Land Use Polygon A «cover type» is simply the material seen on the air photo. O u r procedure employs four covertypes that are easily identified: 1) woody vegetation (trees and shrubs); 2) herbaceous vegetation (in the city, lawns are the dominant form in this category); 3) artificial surfaces (roads, sidewalks, parking lots, rooftops); 4) unvegetated bare soil (occurring in construc­tion areas, quarried, heavily used grasslands).

Step Five: Estimate The Area Each Cover Type Contributes To The Land Use Polygon Begin by estimating the percent coverage by trees, a value referred to as «canopy coverage» or «crown density». The c o m m o n forestry scale employed in most air photo estimates of crown density can be used (Moessner, 1977). It allows the interpreter to compare the area on the photograph with aggregations of dots at different densities, beginning with a class of less that five percent and increasing at ten percent intervals. If the polygon appears to have, say, twenty percent of its seen area covered by trees, that is the canopy density value. The remainder of the area will be divided a m o n g the other cover types.

Step Six: Calculate Stocking Levels For Each Land Use Polygon and Sum Them for Each Stocking level represents the percent of an area available for tree growth that is actually occupied by trees. It is calculated by first adding the percentages for tree cover, herbaceous cover, and bare soil, which, together, constitute the total area available for trees. T o express stocking level as a percentage, divide the tree cover percentage value by the s u m of the percentages for trees, grass and soil. Stocking level quantifies the flexibility an urban forest manager has for increasing canopy cover. The stocking level average over the city of Dayton is thirty-seven percent. That means that sixty-three percent of the space that could right n o w contain trees, does not. T o refine this figure, one can estimate the proportion of the artificial surface cover type that can reasonably be planted with trees (for example, sidewalks and parking lots). This increases the denominator (or divisor) and decreases the quotient, or percent stocking level.

If this had been done for Dayton, it would drop the stocking level value from thirty-seven percent to something well below thirty percent.

Step Seven: Construct Summary Tables For Each Subunit A simple table with land use classes and cover types is an adequate summary for each subunit. Stocking levels can be inserted next to canopy cover values.

51

Step Eight: Develop Bar Graphs That Describe The Structure of The Urban Forest System This step makes the tabular data more visual and, at the same time, provides and overview of the whole system. For each land use, a simple bar graph with the number of subunits on the vertical axis and percent canopy cover on the horizontal axis can be constructed to show average canopy cover values. Bar graphs of several cities can be compared to show the similarities in values within land use classes.

Step Nine: Calculate Surface Runoff For Each Subunit At this point, w e begin to learn what a particular configuration of vegetation and land use is doing to the physical environment; in this instance, to the disposition of rainfall. N o published method exists for accurately calculating h o w m u c h and h o w fast rainfall will run off from areas having the characteristics we've been measuring in the previous steps. So , we've developed a mathematical model that does, using only conservative assumptions about the ability of woody and herbaceous vegetation (and unvegetated soil) to intercept and store precipitation (Sanders, 1982a).

A s an example, w e took a storm event that had a probability of occurring about once a year (1.8 inches of rain in six hours) and let it fall on the distribution of cover types around Dayton which w e had measured using the preceding steps. For this storm event, w e calcu­lated that the present urban forest reduces runoff by seven percent under what it would be if ther were no trees in Dayton. In more c o m m o n and less intense rainfall events, the role of trees increases geometrically. Therefore, you can be sure that the urban forest —that is, just the trees— is responsible for reducing surface runoff by ten percent or more.

Step Ten: Calculate Changes In Runoff With Changes In Subunit Vegetation Structure N o w that w e k n o w that the existence of trees reduces runoff by at least ten percent, it is important to calculate h o w that figure would change if one selectively increased the amount of urban tree canopy. Again taking the conservative approach and using the one year, 1.8-inch, six-hour storm, we increased stocking levels of trees in each land use in each neighborhood to thirty-seven percent the current city-wide average. This brings the reduc­tion in runoff to twelve percent less than what it would be if there were no trees in the city. That is, the current forest structure reduces runoff by seven percent, and the slightly recon­figured forest structure reduces it by twelve percent. While w e have not yet calculated what effects higher stocking levels have on runoff reduction, we are confident that for less intense (more c o m m o n ) storms, it will be shown that stocking levels between 40 and 50 percent will reduce runoff significantly.

Step Eleven: Calculate Air Temperatures For Each Subunit Air temperatures measured at eyeball height (rounghly two meters) are determined by two things: the temperature and moisture of the regional air mass and the ability of the underly­ing surface —whether pavement, grass or trees— to add or subtract heat energy from that two-meter high layer of air. H o w the ability of underlying surfaces to influence low-layer air temperatures is a complex interaction of a number of dynamic variables. Since w e were primarily concerned, in the Dayton study, with the difference in temperature between the city and the country (i.e., the urban heat island phenomenon), we can simplify the problem for our discussion.

Generally, the subunits with a high proportion of artificial surfaces will create high temperatures than those with a high proportion of grass and trees. Trees raise the level of heat exchange to somewhere above the two-meter point. They also use a part of the sun's energy for évapotranspiration, energy that would otherwise go the heat the air. So, under stable air conditions, there is no doubt that vegetation, especially trees, maintains lower temperatures in the two-meter layer closest to the ground. W e k n o w there is about a seven to ten degree Celsius increase in air temperatures at the city center over that of the surrounding countryside. O n a m a p , ther urban heat island is not perfectly round and m a y have little satellite islands sitting over areas with high proportions of artificial surface material. The main island will also shift downwind slightly from the city center in the

52

direction of prevailing winds when wind velocities approach five miles per hour and will dissipate at higer speeds. The magnitude of the heat island is roughly proportional to the logarithm of the population. You can predict what the heat island will be by multiplying the log of your city's population by three, then subtracting six. Using measurements to­gether with a mathematical model, we confirmed in Dayton that the temperature profile of the heat island is similar to what other researchers have found: a shape like the top of M t . St. Helens (Sanders, 1982b). A stylized profile of air temperature at an elevation of two meters shows peaks in the Central Business Districts ( C B D ) . The C B D should be thought of as having two parts: a high-rise center surrounded by a broad zone of lower commercial and industrial buildings, with a large portion of this zone devoted to parking lots, truck-servicing facilities, and roads. It is in the doughnut around the high-rise where heat builds up and the challenge for urban forestry is the greatest.

Step Twelve: Calculate Changes In Air Temperature With Changes In Subunit Vegetation Structure T o make changes in air temperature through reconfiguration of the city's urban forest, use these two guideposts: 1) look at the subunit stocking levels to find opportunities to increase canopy cover, and 2) loo, for groups of subunits with similar land uses and low stocking levels. W e mention the grouping because it is in these parts of the city where major hot spots will develop. With breezes, the parcels of air heated over one subunit migrate horizontally and get heated even more over an adjacent subunit. This is the situa­tion in the zone around Dayton's C B D . This zone is a prime candidate for afforestation for climate control, because it has very low stocking levels (around 15 percent), and with similar land uses, the urban forest manager can appeal to owners and users of the land trough business and commercial groups such as the chamber of commerce or the down­town improvement committee.

Thus, the parking lots of the C B D became the focus of the Dayton Climate Project. A n experimental, hollow concrete brick was used to surface one parking lot so that soil and grass were exposed to the lower air. O n still, hot, summer days ther air temperatures and infrared radiation loads over the «green parking lot» were significantly lower than those over conventional asphalt lots.

Our model for predicting air temperatures from underlying cover types suggests that the urban heat island in most cities can be reduced by 25 to 50 percent by employing woody and herbaceous vegetation in the C B D .

Conclusion

Forestry is the management of a system of trees. Urban forest structure can be described and managed for citywide effects of significant magnitudes. Without a systematic approach, urban foresters will be hindered by a piecemeal comprehension of the total resource, and the effects of trees in the city will not be realized.

B I B L I O G R A F Í A

A V E R Y , T . E . : Interpretation of Aerial Photographs. Minneapolis, Minnesota, Burgess Publishing Company , 1977.

MOESSNER, K . E . : «A crown density scale for photo interpreters». Jour, of For. 45: 434-36, 1947.

P O W N A L L , L . L . : «Photo interpretation of urban land use». Photogramm. Eng. 16(3): 414-426, 1950.

S A N D E R S , R . A . : «Urban vegetation impacts on the hydrology of Dayton, Ohio». Unpublished office report. U S D A For. Serv., Northeast. For. Exp. Stn., Res. W o r k Unit FS-NE-1952, Syracuse, N e w York. 33 pp., 1982a.

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, «Urban air temperature model for urban forestry». Unpublished office report. U S D A For. Serv., Northeast. For. Exp. Stn., Res. W o r k Unit FS-NE-1952, Syracuse, N e w York. 11 pp., 1982b.

S A N D E R S , R . A . , y R O W N T R E E , R . A . : «Classification of American metropolitan areas by ecoregion and potential natural vegetation». Res. Pap. NE-516. Broomall, Pennsylva­nia: U S D A For. Serv., Northeast. For. Exp. Stn. 15 pp., 1983.

54

URBAN EXAMPLES FOR BASIC SERVICES

DEVELOPMENT IN CITIES Urban Resource Systems, San Francisco

Urban agriculture: meeting basic food needs for the urban poor

In recent years, programmes to increase the level of urban food production have been organized in a number of cities. M a n y of these programmes are designed to help improve food supplies and nutrition for the urban poor. Others seek to increase income-generating opportunities for low-income residents or to reduce the dependence on imported food.

Urban agriculture programmes have been organized by governments, community groups, some with the support of international agencies. They have worked to improve and expand city food production in h o m e yards, on vacant city lands, along roadsides and railway rights-of-way, at schools and community centres, and on open areas at city peripheries.

The programmes reviewed here show seven examples of urban agriculture actions in cities of varying sizes and in different regions: two are in Africa, two in Asia, two in Latin America and one in the South Pacific.

These examples are organized so that you can read the basic facts about each project in one minute. The summary is followed by a two or three page review of project details. The concluding paragraph identifies where additional information can be obtained. This book­let was prepared for Unicef by urban resource systems, San Francisco.

Community garden programme in a squatter settlement in Manila, Philippines

1. City: Manila, Philippines. Population: 5,6 million (metropolitan area, 1980). 2. Target population: 2.400 residents of Barrio Matalahib, a squatter community in

Quezon city, a part of the Manila metropolitan area. 3. Time frame: Plans for the programme were developed in april 1980. Actual site

preparation began in m a y of that year. The programme operated until July 1982. 4. Organizers/operators: The garden programme was conceived and designed by two

Quezon city policemen. It was developed by Matalahib residents and members of the police force, with technical assistance from the University of the Philippines and the Earthmen Society, a private non-governmental organization.

5. Objectives: a) T o improve the nutrition of the low-income residents of the c o m m u ­nity, b) T o make productive use of a rubble-strewn area that had become a site of criminal activity.

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6. Costs: All materials for the programme —seeds, water, land, fertilizers and fenc­ing— were donated or were otherwise obtained without cost. N o exact figures are available but the total garden costs were very low.

Technical assistance for the programme was provided by a variety of sources.

Background In 1980 Barrio Matalahib in Quezon city contained two desolate squatter communities that were the h o m e of approximately 400 families. Housing in the barrio was substandard. Its only water supply was one over-used public faucet. The area was plagued by high incidences of unemployment and malnutrition. Another problem was considerable fighting between the two squatter groups, with nightly battles on a rubble-strewn «no-man's land» between the two housing communities.

Programme organization and structure In april 1980 two Quezon city policemen whose jurisdiction included Barrio Matalahib decided to organize a community food garden on the area's «no-man's land». They hoped that this would reduce the level of violence in the community, give the residents an oppor­tunity to improve nutrition, and provide a project that both communities could work on together.

The programme was organized by a local police captain w h o became its director. H e assigned a policeman to work with each family that expressed interest in having a plot in the garden.

The site for the programe was owned by the government's National Housing Adminis­tration, which gave permission to use the land for community gardening.

Programme activities In june 1980 the police brought bulldozers to the site and helped Matalahib's residents clear the land —a process that took two weeks and produced numerous truck loads of masonry and debris.

After the site was cleared, the land (1-1/2 hectares) was divided by the police into one by ten meter family plots. Originally seeds were obtained from a government storage facil­ity. W h e n those failed to grow, gifts of better quality seeds were solicited from private companies. G o o d seeds were also collected from discarded vegetables at nearby markets. The police used fire department trucks to bring water to the site each afternoon for a number of weeks until the rainy season began.

The garden's first crops of pechay, mustard, sweet potato greens, kangkong, and beans came up in July. Production soon exceeded the residents needs. A lively trade in fresh garden vegetables, selling at half ther normal market prices, began on the street fronting the garden.

The second planting of crops included eggplants, sitap, okra and more nutritious leafy crops. In addition, jeep loads of giant ipil-ipil (Leucaena, sp.) tree seedlings were brought in and planted at the garden's perimeter to maintain soil quality and to provide future wood supplies.

In november, a typhoon swept through Metro Manila covering Matalahib Gardens with two feet of standing water. After the waters receded, the gardens were redesigned under the direction of D r . Jose Deanon, an internationally-known horticulturalist from the University of the Philippines, Los Banos. Dr . Deanon was assisted in this task by the Earthmen Society, a private non-governmental organization in Manila.

D r . Deanon had observed Matalahib's initial success before the typhoon and had been amazed by the residents' diligence and hard work. At that time he had seen that they were doing m a n y things incorrectly, but he had refrained from interfering, choosing only to offer suggestions. The destruction caused by the typhoon gave D r . Deanon the ocasión to show residents h o w to design their gardens more efficiently.

For the third major planting of Matalahib, D r . Deanon brought a small tractor from the university. The National Food and Agriculture Council provided new seeds. The police arranged new water hook-ups for the garden site. N e w methods involved the dense plan-

56

ting of small areas which both reduced water loss in the hot tropical climate and alleviated weed problems. Staggered plantings, another of Dr . Deanon's suggestions, produced crops that matured at different times instead of all at once, allowing for an extended harvest.

Programme results The nex planting methods and the enthusiasm of the residents produced additional abun­dant crops throughout 1981. By that time, the garden's 1-1/2 hectares produced 80% of the fresh vegetables needed by the 400 families of Barrio Matalahib. In addition, residents continued to sell some crops to earn income.

By mid-1981, newspaper articles began to feature stories describing Matalahib's successful efforts produce its o w n food. Vegetable buyers and curious visitors came from all over Metro Manila to see the squatters w h o were growing food in the city. In late 1981, however, the government sold the land occupied by the Matalahib Gardens to a private developer. By mid-1982 the gardens had been abandoned and the area was cordoned off by a 3-meter high concrete wall.

Although the loss of the land prematurely terminated Matalahib's urban agriculture programme, residents had learned valuable food production skills during the garden's two years of operation. In addition, the squatter families learned that by organizing, they could begin to change their living conditions. Unfortunately, the destruction of their efforts also served to reaffirm the vulnerability of squatters to government and private intrusion in the absence of land tenure. *

Programme attributes Matalahib Gardens raised community nutritional levels and accomplished a number of social goals primarily as a result of three factors:

1. The initial involvement of the police and later assistance from agricultural experts eased the solution of a number of large problems —site clearing and water shortages in particular—. Without the connections and the «know how» of the leadership groups, the Matalahib residents would have been hard-pressed to overcome such major obstacles.

2. The tremendous interest of Barrio Matalahib residents in the garden programme resulted in the hard work and tenacity necessary to develop the garden and withstand a number of potentially disastrous setbacks.

3. The leadership several Matalahib residents provided to the programme produced links between outsiders and residents that were needed to m a k e the garden truly a c o m m u ­nity endeavor. Four other garden programmes in Quezon city that were started by the municipal government following Matalahib's success did not achieve similarly high levels of production, due mostly to the lack of residents' leadership and initiative.

Programme problems 1. Despite the efforts of the local police, university officials, and the residents to con­

vince them of its worthiness, the city government never fully supported the project. This precluded any progress on obtaining a lease for the site from the National Housing A d m i ­nistration and eventually resulted in the garden's demise. Badly needed picks, spades, shov­els and other tools that had been promised to the project early in 1981 were also never provided.

2. The lack of adequate water supply in the squatter settlement limited the garden's productivity during the dry season.

3. The government donated seeds for the initial planting with the best of intentions. Those seeds, however, were so old that they failed to germinate.

Sources J A M I R , N a p C : The short happy life of Matalahib. Paper presented at the Urban Agricul­ture Workshop, Singapore, 1983 (sponsored by the International Development Research Centre). Research conducted in Manila in 1981 by Urban Resource Systems staff members. Correspondence with Mario Chanco, Earthmen Society, Manila, Philippines, 1982-1984.

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H o m e garden promotion programme in a large low-income suburb of Panama city, Panama

1. City: Panama city, Panama. Population: 685.000 (metropolitan area, 1980). 2. Target population: 200.000 residents of San Miguelito, a rapidly growing suburb of

Panama city. 3. Time frame: The programme was designed in 1981, started in 1982, and continues in

operation today. 4. Organizers/operators: The programme was organized by the Panama Ministries of

Health and Agriculture, with U N I C E F support, as part of the Proyecto de Producción de Alimentos y Mejoramiento Nutricional ( P A M E N ) .

The programme is operated by the P A M E N staff and a system of volunteer neigh­bourhood co-ordinators.

5. Objectives: The goal of the programme is to improve the nutritional status of the San Miguelito residents by producing vegetables and fruit in home gardens.

6. Costs: The programme is financed by U N I C E F , and by the Ministries of Health and Agriculture which also provide personnel and support services. Programme costs include staff training, production classes, programme direction and supervision, and resource procurement.

Background San Miguelito, a suburb of Panama city, grew very rapidly in the 1970's. During that decade it burgeoned from a sparsely populated area on the edge of the city into a busy community of nearly 200.000 people. Most of the area's residents are recent immigrants from Panama's rural areas or Panama city's core districts.

Unemployment and underemployment, poor housing conditions, and other problems c o m m o n in fast-growing low-income urban communities plague San Miguelito.

Malnutrition, although not severe, is a serious problem. A survey of Panama city resi­dents taken in 1980 revealed that overall, 61% of them consumed less than the recommended daily allowance ( R D A ) of total calories. Of that 61%, more than a third consumed less than 70% of thexaloric R D A . Vitamin A deficiencies are widespread, as nearly half of the population consumes less than 50% of the R D A of that important vitamin. In addition 40% of the population consumed less than 70% of the R D A of calcium and 26% consumed less than 70% of the R D A of iron. Because incomes in San Miguelito are lower than the average in Panama city, it is fair to assume that dietary deficiencies there are more severe than the survey would suggest.

Programme organization and structure The San Miguelito h o m e garden programme was organized in 1981 by the Panamanian Ministries of Health and Agriculture as part of the Proyecto de Producción de Alimentos y Mejoramiento Nutricional ( P A M E N ) .

The director of the programme is an agriculture ministry official w h o has undergone a five-month training programme in small-scale food production at the Asian Vegetable Research and Development Center on Taiwan.

The basis of the programme is a series of classes in simple, low-cost gardening techni­ques. The classes, taught by the programme director, serve to train volunteer neighbour­hood leaders.

After attending the garden how-to classes, the volunteer leaders work with their neigh­bours in turn to establish home gardens and to educate residents about the nutritional benefits of small gardens.

Programme activities The classes in food production and basic nutrition for neighbourhood leaders began in 1982. During the same year the leaders and the programe staff began working with families in their yard spaces. Their efforts included site leveling and/ or terracing, procurement of topsoil (when necessary), the addition of soil amendments, construction of raised beds, fence construction, planting, tending and harvesting. The programme staff also conducts

58

talks and discussions on home gardening at schools, clinics and other institutions. The talks explain the dietary improvement that produce from small food gardens can bring and provide practical demonstrations of gardening techniques.

In order to maximize their appeal and feasibility to San Miguelito's low-income resi­dents, the h o m e gardens are designed to be low-cost and use mainly local materials.

Programme results Over 100 neighbourhood leaders were trained in the food production classes during 1982. Of these leaders, more than 50% were w o m e n .

During the rainy season of 1982, the San Miguelito programme started more than 250 h o m e gardens. A wide variety of crops were planted including tomatoes, squash, beans, yucca, cucumbers and various green leafy crops. The gardens serve over 1.350 people, among them 600 children and over 100 nursing or pregnant mothers.

The average garden is small (3-1/2 meters by 4 meters) and is located in a yard adjacent to the gardener's h o m e . The gardens use raised beds, trellises, and other techniques of intensive cultivation. During the dry season gardens are irrigated from h o m e and central water taps.

N o detailed assessment was made of the nutritional benefits of the home gardens during the programme's first year. Certainly the gardens increased the amount of food available to the families that developed them, and assuming proper crop selection, have probably alleviated certain vitamin and mineral deficiencies.2

Programme attributes Four important factors contribute to the success of the San Miguelito home gardening programme:

1. The gardening techniques taught are simple, inexpensive, and highly productive. The programme director's expertise in this type of food production is the Key to the programme's initial success.

2. The programme staff is extremely energetic. They are dedicated to the promotion of better nutrition through home food production, and their enthusiasm has convinced a number of residents to join the programme.

3. Because the Ministry of Health is already well-known as a «helping agency» in San Miguelito, by reason of its clinics its involvement in the garden programme is valuable.

4. Government support and financial assistance from U N I C E F provide the underpin­ning necessary for a programme addressing the needs of such a large area of a city.

Programme problems 1. The soil in the hilly areas of San Miguelito is below average. 2. The large area covered by the programme and the limited transportation available

to the staff make administration and co-ordination of the programme somewhat difficult.

Sources «Tabulación, análisis e interpretación de la ingesta de calorías y nutrientes a nivel familiar en la República de Panamá.» Encuesta Nacional de Nutrición, 1980. This research had been conducted in Panama city in 1983 by Urban Resource Systems staff members.

Comprehensive city-wide food and fuel self-reliance programme in Lae, Papua N e w Guinea

1. City: Lae, Papua N e w Guinea. Population: 52.000 (metropolitan area, 1980). 2. Target population: Low-income residents of Lae. 3. Time frame: The programme was designed and implemented in the period 1977-79.

All parts of the programme are currently operational. 4. Organizers/operators: The programme was organized by the Lae City Council and

the Papua N e w Guinea national government. Technical assistance w a n provided by the

59

U N E S C O / U N E P programme « M a n and the biosphere project 11», the Australian Nation­al University, and other international agencies.

5. Objectives: a) T o improve the nutrition of Lae residents, b) T o reduce the city's depen­dence upon imported foods and fuel, c) T o increase supplies of firewood, d) T o rehabili­tate and restore to productivity the farm and forest land inmediately surrounding the city. e) T o increase the opportunities to earn income from the sale of food and firewood./) T o reduce solid waste problems in the city.

6. Costs: Programme design costs were paid by the government of Papua N e w Guinea, the Lae City Council, U N E S C O / U N E P , and other agencies.

The programme's operating costs are paid by the Lae City Council and the Papua N e w Guinea National Government.

Background During the 1960's and 1970's Lae, the major industrial city of Papua N e w Guinea, under­went tremendously rapid growth. In the period between 1966 and 1971, the city grew by 16% per year. In recent years, the growth rate has been slower but is still a relatively high 5% a year.

By the mid-70's rapid growth had contributed to a number of serious problems, including:

1. high unemployment and underemployment; 2. the destruction of m u c h of the heavily forested area surrounding the city by resi­

dents desperate for firewood and land for subsistence gardening; 3. a dependence on imported food supplies for over 25% of total food consumption; 4. a buildup of solid wastes resulting in land and water pollution; 5. malnutrition, particularly a m o n g children.

Programme organization and structure In 1977 the Lae City Council, with the assistance of national government agencies and international groups, formulated a comprehensive plan to increase food and fuel produc­tion within the city and in the Atzera Hills region just outside the city proper.

The overall goal of the plan was to m a k e Lae more self-reliant in food and fuel. This was to be accomplished through the implementation of a variety of programmes run by the City Council and staffed by residents of the city.

The plan included the rehabilitation of farmlands and forests surrounding the city, the construction of city food garden «allotments», an extensive fruit and nut tree planting project, projects to improve the nutrition of school children, and a city-operated compost­ing facility.

Programme activities and results Community gardens. Allotment food gardens are being constructed on city lands and assign­ed to low-income residents by the city government. The crops are fertilized with locally-produced compost. The city horticultural staff provide plot holders the technical assistance on intensive planting techniques, the selection of nutritious crop varieties, and other garden-related matters.

The Council set up 1.500 allotment gardens measuring 10 by 20 meters in low-income settlement areas of Lae in the first three years of the programme.

Atzera Hills Project. In 1977 a six-year programme to both restore and cultivate the hills at the southern edge of the city began under the direction of the city council. The programme was designed by the Council with the assistance of outside agencies. The Atzera Hills region had been extensively stripped of vegetation as a result of the indiscri­minate production of food and collection of firewood that took place during Lae's period of greatest population growth.

The project formulated a comprehensive plan that divides the hills into ecological rehabilitation and conservation zones, fuel wood cropping zones and subsistence agro-forestry zones.

The plan designates and prohibits specific practices for each area.

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The programme aims to increase Lae's food supplies, bolster the production of cash crops, increase firewood sales, fuelwood supplies, preserve the Atzera Hills and prevent erosion.

In the agroforestry zones, small plots averaging one-tenth of a hectare are laid out. Their use combines subsistence food production and the growing use permits for the plots are granted by the city council. This important step guarantees plot holders land security and so encourages the use of cultivation techniques that provide for long-term productivity rather than simply short-term rewards.

In the first years of the programme, there has been m u c h work to rehabilitate eroded hillsides and stream banks. Trees appropriate for erosion control and for future firewood supplies are being, planted.

A large number of agroforestry plots have been planted with fast growing tree species such as Leucaena and compatible vegetable crops.

Fruit and nut tree programme. The city council has established a nursery where fruit and nut tree seedlings are planted in public areas in Lae and distributed free to city residents for planting in their yards.

The nursery's research programme tests the appropriateness of different tree varieties to different purposes.

School nutrition programme. The city council staff has developed «nutri-pies», a highly nutritious lunch supplement, to help alleviate malnutrition a m o n g school children. The main ingredients of the pies, vitamin and mineral-rich vegetables, are grown in the Lae city gardens or in the school gardens. The appetizing pies, which were taste-tested in the schools, are manufactured by a local company and sold at low cost in the schools. Costs that are not covered by the income from sales are paid for by the city council.

Compost production. The city has begun to compost organic wastes at its landfill site. Glass, metal, and other non-biodegradeable objects are removed from wastes produced by homes, schools, factories, and other institutions. The organic matter remaining is combin­ed with manures and composted.

During the first two years of the programme, 1.500 tons of compost were produced. This amount was sufficient to fertilize all of the city gardens and parks in Lae and to provide a surplus for sale to commercial farmers outside the city. The programme plans for the eventual production of 11.000 tons of compost per year. This will result in a 10% reduction in the amount of waste disposed of in landfills.

Programme attributes Lae has developed one of the most comprehensive and extensive urban food and fuel production plans in the world primarily because:

1. The Lae city council is strongly in favor of the city developing the greatest possible degree of self-reliance in food and fuel supplies.

2. There is significant interest a m o n g Lae residents in food production. This stems from the fact that m a n y are unemployed and most have recently lived in rural areas where subsistence food production is a basic part of daily life.

3. The manufacture of compost by the city makes intensive food production possible on land that loses fertility easily due to heavy rainfall. Large amounts of compost are essential to the success of the Lae programme. Commercial fertilizers are too expensive for subsistence food producers.

4. The Lae City Council has solicited and received technical assistance from the nation­al government and international organizations. The aid provided by these groups has hel­ped to m a k e the Council's plan workable.

5. The Lae programme takes an integrated approach to food, fuel and environmental problems. Projects developed within the programme address economic, social, and envi­ronmental problems as parts of a whole.

Programme problems D u e to problems with equipment and organization, the compost production programme has not been implemented on as large a scale as originally planned.3

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Sources N E W C O M B E , Ken: Creating urban agro-ecosystems, an essential part of a renewable energy

future. Department of Minerals and Energy, Papua N e w Guinea, 1979. N E W C O M B E , Ken, and P O H A I , Timothy: «An ecological approach to third world urbaniza­

tion within the framework of M A B 11». Ambio, Journal of the Royal Swedish Aca­demy of Sciences, 1979. .

SIKI, Beka F.: Atzera Hills Management Programme in Brief. Unpublished paper prepared by the author for the city of Lae, Papua N e w Guinea, 1981.

HARRIS, J. A . : Ecological Management of the Atzera Range Adjoining Lae, Papua New Guinea. Centre for Resource and Environment Studies, Australian National University.

Newspaper articles from Lae and Port Moresby, Papua N e w Guinea, 1978-1981. Research conducted in Lae in 1981 by Urban Resource Systems staff members.

Multi-sector urban a agriculture programme in the self-help townships of Lusaka, Zambia

1. City: Lusaka, Zambia. Population: 576.000 (1980). 2. Target population: 160.000 residents of Lusaka's three major low-income townships,

as well as additional low-income residents in other areas of the city. 3. Time frame: Official programmes were initiated in 1977, one programme continues

today. 4. Organizers/operators: Programmes have been organized and operated jointly by the

Lusaka city Council, the Zambian national government, the American Friends Service Committee (AFSC) , and U N I C E F .

5. Objectives: a) T o improve the nutrition of low-income families, b) To provide opportunities for income generation from the sale of crops.

6. Costs: Operating costs have been paid by the American Friends Service Committee, U N I C E F and Zambian Government agencies.

Background Urban agriculture has been an important part of city life in Lusaka for nearly two decades. In recent years, the amount of cultivation has risen considerably. The increase is in res­ponse to the severe economic problems that began in Zambia in the mid-1970's. While wages remained constant and unemployment grew between 1973 and 1976, consumer pri­ces rose by 60%. During a five month period in 1977-78, in one low-income township the cost of the cheapest nutritionally adequate diet rose by over 20%. This escalation imposed a severe hardship on people w h o were already spending a large proportion of their income on food.

Faced with rising costs, the urban poor in Lusaka intensified and expanded their food production. By 1977 43% of the residents of C h a w a m a , one of the city's three large low-income townships, were cultivating home gardens. In addition, 57% of the households in C h a w a m a were growing food in one more «distant» gardens on vacant lands away from their homes.

Surveys showed that such gardens were saving residents 10-15% on food costs.

Programme organization and activities Government agencies and international organizations began taking action to help Lusaka's residents improve and expand their food production efforts in the mid-1970's. All the approaches recognized the extent of urban agriculture activities already under way and attempted to assist and encourage these efforts. The official assistance programmes under­taken can be divided into four categories:

Patriotic appeals. In October 1977 Dr. Kenneth Kaunda, the President of Zambia, appealed to Lusaka's residents to help ease the country's economic crisis by growing more of their o w n food. In a speech made to the National Assembly, Kaunda urged greater urban food production in order to permit the export of rurally grown crops. Such export would earn badly-needed foreign exchange for Zambia. President Kaunda's message to the

62

capital's residents was that «they should no longer rely on farmers in Chisamba or M a z a -buka... Lusaka residents must get on with the job of working the land».

Modifying land-use law enforcement. In the late 1970's the Lusaka City Council, under pressure from low-income residents, decided to waive enforcement of laws forbidding the cultivation of food grown on vacant city land. The non-cultivation laws had frequently been used to justify the destruction of corn crops on land not belonging to the cultivator. The rationale for these laws was that such crop production created a «health hazard» because of the breeding of mosquitoes and the possible spread of malaria. The decision not to enforce the non-cultivation laws greatly increased the amount of food production throughout the city.

Organized food production programmes. During the late 1970's two programmes were developed by the American Friends Service Committee, U N I C E F and Lusaka community leaders in two townships. The first programme was organized in the township of C h a w a m a in 1977. It was supported by U N I C E F which provided an agricultural expert, and by A F S C which provided the support for two Zambian nutritionists. These experts were to work with C h a w a m a residents to improve and expand both their h o m e gardens and the «distant gardens». The support team provided technical assistance and sold supplies such as seed and fertilizers at low cost. In addition, the programme staff established a demons­tration garden where experiments in crop selection, soil preparation, and gardening tech­niques were carried out. The staff also helped set up community gardens in the township at two community centres.

Despite an inital period of success, by late 1978 the C h a w a m a garden programme had dissolved. Furthermore, the extensive plans for implementing an «Urban Agriculture and Nutrition Service» in C h a w a m a and other townships had not materialized.

In Jack Extension, another township, a second, more successful effort was begun by the A F S C in 1978-80. Here, the approach focused on assistance to residents in the prepa­ration and cultivation of family plots. Low-cost seed and fertilizers were also provided. A 20-hectare plot next to the township's housing area, was secured. Programme staff m e m ­bers helped residents to develop this area for food production. The programme's nutrition­ists also lectured on and discussed the subjects of food and nutrition with groups of m e n and w o m e n in the community. In 1980 the programme was expanded to include a fruit tree planting programme.

Up grading squatter housing. In 1975 a major project, funded by Zambia and the World Bank, was initiated to improve Lusaka's three major squatter areas that together housed 160.000 people. A central feature was the granting of land tenure and the provision of basic city services to the areas. Providing access to water for all of the homes in the project enabled m a n y h o m e gardeners to produce food year round, rather than just during the five-month rainy season. Securing land tenure further encouraged production, resi­dents were no longer in constant fear of being evicted and could plan gardens for long-term use.

Programme results —~ Because there were no comprehensive surveys of urban agriculture in Lusaka before and after the organized programmes were initiated, the effect of the programmes cannot be quantified. However, each can reasonably be assumed to have directly or indirectly helped the urban poor to grow more of their o w n food.

The appeal in land-use law enforcement significantly encouraged the cultivation of vacant areas throughout Lusaka.

The organized urban agriculture programmes have helped a number of low-income residents in two communities to begin food production and haver provided needed infor­mation about nutrition. Understanding the problems that led to the disbanding of the first organized effort in C h a w a m a township helped the groups involved in Jack Extension and other townships avoid mistakes in the new projects.

Provision of land tenure and access to piped water improved food production in the squatter housin development project. M o r e indirectly, participating in the community development and self-help aspects of the upgrading project served to increase the skills and

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confidence of many residents, contributing to the initiation of oher activities such as food production.4

Programme problems 1. The first organized programme in C h a w a m a Township failed primarily because the

agencies involved did not develop a clear mutual agreement about the importance of the project. W h e n A F S C moved on to work in other townships as planned, local government agencies did not lend sufficient suppor to maintain the programme.

2. Theft problems in the dry season plagued some efforts to develop irrigated gardens. During the rainy season, there are minor theft problems in all of Lusaka's gardens. The significantly fewer number of irrigated gardens during the dry season made them obvious targets for theft.

3. Soil erosion problems developed in some areas where «distant gardens» had been cultivated improperly.

Sources H O E K - S M I T , Marja: Community participation in squatter upgrading in Zambia. American

Friends Service Committee, 1982. JAEGER, Dirk: Lusaka, garden city: The agricultural activities of city residents. Royal Tro­

pical Institute. Amsterdam, 1983. L E D O G A R , Robert J.: «Food and survival in Lusaka's self-help townships». Carnets de

l'enfance, vol. n.° 43, 1978. Interview with M r . Bish Sanyal, University of California at Los Angeles, Department of

African Studies, 1983.

Market garden programme in a low-income district of Kisangani, Zaire

1. City: Kisangani, Zaire. Population: 335.000 (metropolitan area, 1980). 2. Target population: Mátete, a low-income community of 140.000 located on the

fringe of Kisangani. 3. Time frame: The programme was organized and developed in 1978 and has conti­

nued since that time. 4. Organizers/operators: The programme was planned by community members with

the assistance of a group of Zambian academics interested in community development. The programme is operated by the gardener-participants with technical assistance from

a Kisangani-based agriculture expert. 5. Objectives: a) T o produce income for Mátete residents through the sale of communi­

ty-grown vegetables to Kisangani markets, b) T o improve the nutrition of the gardeners and their families by producing vegetable crops for h o m e consumption, c) T o develop the community-organizing and problem-solving skills of local residents.

6. Costs: The programme is designed to keep costs at a min imum and eventually to become self-sustaining.

There are no land costs in the programme since the participants use their o w n home plots for the market gardens and they are allowed the free use of a large, vacant area for the communal garden. Seeds are either purchased with the income earned from crop sales or they are obtained from the gardens. Compost and other fertilizers are collected by the gardeners at no or very low cost.

Background Mátete is a suburban district of the rapidly growing city of Kisangani in northern Zaire. The city grew by over 100.000 new residents between 1970 and 1980, a 43% increase in population. It is growing at a similary fast rate in the 1980's.

Housing in Mátete is poor in quality, lacking electricity and running water. Residents of Mátete face problems of low income, high unemployment, malnutrition and high infant mortality.

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Programme organization and structure The idea for a market garden programme originated at a series of meetings held in 1977 between Mátete residents, their chief and a group of local academics. (The academicians were in Mátete to assist with district development projects and to observe h o w the c o m ­munity functioned.)

In the community meetings, residents listed problems with the cultivation of food crops as their primary concern. Their subsistence and market gardens were losing fertility and no one knew h o w to correct the situation. Rural farming practices, such as periodically allow­ing some land to lie fallow, were not appropiate given the limited availability of land in the cramped spaces of Kisangani.

The academic group, which knew little about food production, agreed to help residents organize a programme that would improve and expand their food gardens. Control of the programme would rest with the residents, the academics would simply assist by making suggestions, giving encouragement, and by advancing organizational ideas.

The group first decided to seek, in Kisangani, an agricultural expert w h o could instruct them in urban food production. A m a n with F A O project experience was found w h o knew both of the local languages. H e consented to teach two-hour sessions on gardening techni­ques twice weedly to all interested Mátete residents.

The group sought instruction in five areas: 1. techniques of garden site preparation; 2. the use of «fertility builders» such as organic waste, dung and compost, and the

practice of crop rotation; 3. plant cultivation and other gardening skills; 4. collection of seed; 5. bookeeping and basic sales skills. For the take of simplicity it was decided that each participant would use the land

available in or around his h o m e plot. Accordingly the gardeners chose to m a k e use only of tools they already possessed.

Programme activities The programme began in february 1978 with food production classes conducted on the local chief's plot. The aim of the sesions was not only to inform but also to encourage individual initiative by communicating that all group members were an important part of the programme. In addition to the group classes, the instructor m a d e periodic visits to individuals' plots to correct mistakes and recognize success.

N e w , protein-rich vegetable varieties have been introduced into the programme by the agricultural instructor. Instruction on the cultivation and use of these crops has been included in the twice weekly classes.

Sales of the vegetables are handled mostly by the individual gardeners themselves. A n attempt at creating a c o m m o n fund through the levy of a 10% tax on all sales failed.

Programme results During the first two years of the programme the sales of produce nearly doubled the average annual income of the participants. Crops included both native and european vege­tables. Over ten hectares of land both within and between the housing plots was put into production.

Most importantly, residents were able to increase their food production without further depleting the soil. The use of compost, dung and other «wastes» permitted low-cost, high-yield gardening and the maintenance and improvement of soil fertility. Using these prac­tices, Mátete residents m a d e the important change from rural to urban-style gardening by learning to cultivate small plots efficiently over a sustained period of time.

The initial success of the Mátete market gardens sparked another important change. In the programme's second year, participants decided to begin a two-hectare c o m m u n a l plot to grow vegetables strictly for their o w n consumption and for seed collection. This second stage became possible as a result of the participants' use of improved gardening methods and their increased confidence.

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In addition, the success of the programme developed the self-worth of the participants, critically needed in a situation where lack of opportunity, jobs, and education had been the cause of m u c h personal despair.

Programme attributes Four important factors that have contributed to the success of the Mátete market garden programme are:

1. the organization of the programme to meet specific community needs and interests; 2. the availability of a good teacher; 3. the utilization of only inexpensive, locally-available resources; 4. the adequate supply of land available for food production.

Programme problems In Mátete most of the labor of food production is done by w o m e n and children. However, due to the local practice of segregating meetings by sex, and also to the fact that w o m e n lack the time for such activities, w o m e n are almost entirely unable to participate in the meetings and classes. As a result, the instruction provided to the m e n in the gardening classes must be transmited by them to their wives and children. 5

Sources NUGB'USIM, M . N . , and S T R E I F F E L E R , F . : «Productive work for low-income families in an

urban environment: an experience in Zaire». Ideas and action.

Centrally-planned system of suburban food production in Shanghai, China

1. City: Shanghai, China. Population: 14.250.000 (metropolitan area, 1980). 2. Target population: 14 million residents of the Shanghai munipalicity. 3. Time frame: The system was organized in the 1950's. 4. Organizers/operators: The programme was organized and is operated by the Shan­

ghai municipal government in conjunction with other government agencies. 5. Objectives: a) T o produce most of the vegetables, grains and other food required by

Shanghai's residents, b) T o minimize food transportation and storage costs, c) T o cut the use of fossil fuel by reducing the need of urban areas to «import» and convey food from rural areas.

Background Prior to the revolution in China in 1949, a significant amount of food was produced on the land around Shanghai, the country's largest city. The combination of good soil, abundant water, plentiful fertilizers, a mild climate, and markets nearby in the city made suburban farming a worthwhile endeavor.

Programme organization After the revolution the production, distribution and marketing of food in the Shanghai area where placed under the control of the Shanghai municipal government, an authority '.hat controlled not only the city proper, but the ten rural and suburban counties surroun­ding it as well.

in the municipal system, agricultural decision-making became a complex process involv­ing central government officials, a number of bureaus and offices, county governments, and the newly-collectivized farms. All growing and marketing of food followed centrally-planned policies for the area. This meant that for the first time Shanghai's food supplies were no longer dependent on the diverse, individual decisions of many rural and provincial authorities, but on the workings of a unified, co-ordinated regional food system.

During the ensuing years, the structure of the Shanghai food system has undergone a continual process of revision and reform. Changes in government priorities and the succes­ses and failures of various parts of the agricultural network all have shaped it.

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Today, the Shanghai municipality's food programme is an intricate combination of centralized control and localized decision-making. The structure of the Shanghai munici­pality's food system is dynamic, continually evolving through a process of centralized planning geared to integrating the aims and capacities of the various types and orders of food producers the system comprises. Decisions m a d e in the planning process result in policies that address the food needs of the entire municipality with m a x i m u m efficiency.

Programme activities The current food-related policies of the Shanghai municipal government are designed to meet the following five objectives:

1. The division of the region into different agricultural sectors according to the charac­teristics of the land and other resources, in order to m a k e the most appropriate use of these be it by farming, forestry, or animal husbandry.

2. The development of an integrated system of educational and scientific resources to be utilized for the purpose of intensifying agricultural production.

3. The design of an urban food policy specific to the Shanghai region and its unique agricultural features.

4. The development of programmes to narrow the economic gap between the popula­tion of cities and towns and that of industrial and agricultural areas.

5. The integration of the economic and managerial aspects of agricultural production. Today, Baoshan, Jiading, Shanghai, Nianhu and Chuansha, the five innermost countes

of the Shanghai municipality, concentrate on vegetable propagation. The areas of these counties nearest the city proper are devoted to the continuous and exclusive production of vegetables. Outlying lands are utilized to produce an array of other crops and grains as well as vegetables. Growing vegetables close by the city insures their freshness and, impor­tantly, minimizes the cost of food transport. Regionally produced vegetables appear in Shanghai markets within 10-15 hours, or less, of being harvested.

Lands in the five other counties of the municipality are used for grain production (two crops of rice and one crop of winter wheat a year), animal husbandry (pig farms have been expanded in recent years), and the growing of other more minor crops.

Food produced in the municipality is transported to the city by government agencies such as the Supply and Marketing Co-operatives and by the production communes them­selves. Direct transportation of vetegable crops from farm to market is usual. Most vege­tables are produced within 10 kilometres of their point of sale.

In addition to producing food for Shanghai residents, the municipality's communes and agencies grow grain for export and operate a variety of food processing plants.

Programme results The Shanghai municipality has m a d e steady progress in improving the food situation in the city in the last 35 years. Since 1949 there have been no severe food shortages in Shang­hai. This is a significant achievement given the fact that the city is one of the largest and most densely-populated urban areas in the world.

Today the municipality's c o m m u n e s supply most of the food for a metropolitan popu­lation of 14 million people, including 100% of the fresh vegetables, most of the grains, and significant quantities of pork, poultry and other foods.

In addition to producing great quantities of food, the Shanghai system has worked to maintain stable, affordable prices for food, particularly staple products. This is an impor­tant factor in a city where most residents spend close to 50% of their incomes on food.

With centralized planning and 35 years of hard work, the Shanghai food producers have turned their region into one of the most productive in China. In recent years the municipality has not only fed its o w n huge population but also has often exported surplus grains and vegetables to other cities and provinces.

Programme attributes The Shanghai system has m a d e important progress in improving the city's food supplies for a number of reasons, including:

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1. Central planning for the entire municipality has provided needed co-ordination for a massive agricultural system.

2. Flexibility in planning and operating the system has allowed for much re-organiza­tion of the production efforts as planners have learned more about h o w a large urban food system works.

3. Efforts to control the expansion of the city's residential and industrial areas have slowed the take-over of close-in vegetable lands.

4. Suburban farming has taken full advantage of the proximity of plentiful supplies of cheap fertilizers from the area's pig farms and from the city's human waste systems, hold­ing d o w n the need for expensive chemical fertilizers.

Programme problems 1. Striking a fair balance between the needs of urban and rural residents continues to

be a difficult problem. For example, efforts to maintain affordable prices for food in city markets have also served to depress the income levels of the suburban communes . In 1977 the government yielded to pressure from farmers and c o m m u n e officials and raised the purchase price for non-staple agricultural products. This caused a dramatic increase in urban food prices.

2. M a n y suburban communes are still striving for self-sufficiency. This is somewhat incompatible with the new plans to divide the Shanghai region into different specialized agricultural sectors based on local resources.

There have been minor problems in some years with maintaining a steady supply of fresh vegetables during the periods of adverse weather conditions.6

Sources S K I N N E R , G . W . : «Vegetable supply and marketing in chinise cities». China Quarterly, 1977. H A W K I N S , J. N . : «Shanghai food system». Research in various chínese cities in 1979 and 1981 by Urban Resource Systems staff

members.

Multi-faceted government programme to improve food supplies for the urban poor in Managua, Nicaragua

1. City: Managua, Nicaragua. Population: 684.000 (metropolitan area, 1980). 2. Target population: Low-income residents of Managua. 3. Time frame: The programme was organized in 1982 and has been operational since

that time. 4. Organizers/ operators: The programme was organized by the national government as

part of P A N —Programa Alimentario Nicaragüense—. The programme is operated by government employees and residents of Managua.

5. Objectives: a) T o increase the supplies off affordable, staple foods available to low-income residents of Managua, b) T o employ city residents and create opportunities for income-generation, c) T o reduce the use of fossil fuels by reducing the necessity of trans­porting food from rural areas to the city, d) T o make productive use of large plots of vacant land within the city.

6. Costs: The costs include government staff time for programme design and develop­ment, employee wages, and the purchase of seeds, fertilizers and pesticides. All costs are paid by the government.

Background Three determining factors spurred the development of an urban agriculture programme designed to increase supplies of staple foods for the residents of Managua.

First, the population of the city is growing rapidly. F rom 1970-80 there was a 65% increase. The population of the capital is expected to hit the one million mark by 1990. One out of every four Nicaraguans n o w lives in Managua.

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Second, despite recent increases in rural food production, government officials were concerned that food supplies for the urban poor in M a n a g u a had not significantly improv­ed. Inadequate urban food supplies have largely resulted from problems with the transpor­tation of food from rural to urban markets and with food storage. Costs to middlemen have also exacerbated the city's high food prices.

Third, there are large areas of fertile land that can be used for food production lying vacant within the city. The destruction caused by the 1972 earthquake was one reason for the vacancy. The land policies of the government prior to the 1979 revolution also led to an irregular development pattern in the city and further contributed to the amount of open space found within the city.

Programme organization and structure In 1982, as a part of the Programa Alimentario Nicaragüense, a national programme to improve the country's food situation, government officials developed a strategy to increase Managua's supplies of staple foods. Programmes to promote large uban market gardens, h o m e gardens, suburban farming co-operatives, and other approaches to city food produc­tion were planned as a part of the strategy to increase the quantity os staple foods produ­ced in the city and its environs.

The large market gardens were directly organizes by the government on state-owned land. The government paid all costs and all workers earned wages.

The h o m e garden programme was organized by the government in conjunction with a city women's organization, Asociación de Mujeres Nicaragüenses «Luisa A m a n d a Espi-noza». The government and the women's group developed a campaign to promote h o m e gardening in various M a n a g u a neighbourhoods.

The suburban farming co-operative programme was organized by government officials and by the co-operatives themselves.

Programme activities In early 1982 two large market gardens were designed and developed. O n e garden lay in the centre of the city on a large tract of vacant land, and the other at Ciudad Sandino, on the western edge of Managua . Each is approximately 25 hectares in size.

A n overhead sprinkling system was constructed at the city center site to allow garden­ing during the six-month dry season. The Ciudad Sandino garden is limited to rainy sea­son production.

The gardens are planted with the staple foods that are in high demand including corn, tomatoes, squash, onions and melons.

Over 200 workers are employed in the gardens. They plant, tend, harvest, and transport the crops. The food produced is sold directly to the main wholesale market in Managua .

A n agricultural assistance programme has been organized to aid the development of small farming co-operatives at the edge of the city. The government subsidizes the cost of water and rent, and provides credit for the purchase of seeds, fertilizers, and other resources.

The h o m e garden promotion campaign has been postponed until a later date.

Programme results G o o d quality crops have been harvested from both of the 25 hectare market gardens during the first two years of operation. The crops are sold in Managua's markets at prices lower than those for similar food grown in rural areas. Corn is the main crop being grown in the market gardens.

Programme attributes Three important factors are contributing to the successful development of the M a n a g u a programme.

1. The national government is committed to improving food supplies for the city. F r o m this commitment has come a considerable expenditure of both time and funs to begin large-scale food production in Managua .

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2. Government ownership of large areas of land in and around the city has facilitated the development of the urban food programme.

3. The government's ability to place urban food production in a broad perspective has helped the programme gain m o m e n t u m . The stated purpose of the urban food plan is not only to improve nutrition but also to show that transport fuels can be conserved and the drain of food supplies from rural to urban areas can be reached.

Programme problems 1. Eventual limits to the government's ability to finance the costs of seeds, fertilizers,

and water pumping could jeopardize the programme's future. 2. Because Nicaragua's agricultural schools have focussed largely on the training of

experts in the production of export crops, such as cotton and coffee, there is a lack of expertise relevant to the production of foods for domestic consumption such as vegetables. This emphasis is changing n o w , but the current shortage of qualified technical assistance people presents a problem.7

Sources Research in Managua in 1983 conducted by Urban Resource Systems staff members. Correspondence with Gerard Barbeau, Ministerio de Desarrollo Agropecuario y Reforma

Agraria, 1983-84.

N O T A S

1. For any additional help or informatir information and photographs write to Urban Resource Systems, ction P D P D , U N I C E F , New York. For furthe783 Buena Vista West, San Francisco, C A 94117, U S A .

2. For detailed information write to U N I C E F Representative, Guatemala City, Guatemala. For any further help or information write to the Urban Section P D P D , U N I C E F , N e w York, or to Urban Resource Systems, 783 Buena Vista West, San Francisco, C A 94117, U S A . For additional help or information write to the Urban Section P D P D , U N I C E F , New York. For further information write to Urban Resource Systems, 783 Buena Vista West, San Francisco, C A 94117, U S A .

4. For additional information and photographs write to Urban Resource Systems, 783 Buena Vista West, San Francisco, C A 94117, U S A .

5. For additional help or information write to the Urban Section P D P D , U N I C E F , New York. For any further information write to Urban Resource Systems, 783 Buena Vista West, San Francisco, C A 94117, U S A .

6. For additional help or information write to the Urban Section P D P D , U N I C E F , New York. For any further information write to Urban Resource Systems, 783 Buena Vista West, San Francisco, C A 94117, U S A .

7. For additional help or information write to the Urban Section P D P D , U N I C E F , N e w York. For any further information write to Urban Resource Systems, 783 Buena Vista West, San Francisco, C A 94117, U S A .

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DESIGN AND CREATION OF URBAN GREEN SPACES

Zvi Miller President IFLA

Ladies and Gentlemen, W h e n some years ago I came for a short visit to South Korea, I was enormously

surprised by the following, rather phenomenal development. Concerned about the envisio­ned impact of large-scale projects of industrialisation, highways, harbors, dams, etc., on the natural environment of this country, the head of State, former President Park, had appointed a U S trained Landscape Architect as his personal Secretary, with the special mission to establish the profession of Landscape Architecture in Korea. The results n o w , after 15 years are: 23 full university programmes in Landscape Architecture, more than 2.000 government-licensed Landscape Architects and nearly 100 Landscape Architecture firms, engaged in a large variety of design and construction projects, also in other coun­tries.

I a m very pleased and thankful to our friend Dr . Celesia for his initiative, enabling m e as representative of the professional Landscape Architects from 52 countries around the globe to be with you here and to throw some light on the tasks and responsibilities of the qualified Landscape Architect. In spite of the most famous contibutions of this country to the art of gardens and gardening, signified by Alhambra and the Generalife in Granada, Spain is unfortunately one of the very few countries in Europe, where Landscape Architec­ture as an independent profession does not yet exist. I a m sure that you k n o w the reasons for this.

Obviously w e are not only concerned about the enormous threats to our natural envi­ronment, caused to a large extent by «development» and industrialization, often financed by international aid programmes.

L o w living standards in population congestions of m a n y major urban centres around the globe, completely lacking adequate open space systems, playgrounds, sports and mass recreation facilities, have created alarming, dangerous situations. In m a n y areas urban sprawl has totally grown out of control. Pressure on the land and increasing crime rates are new realities to be faced. A s responsible planners Landscape Architects must construct­ively contribute to solving these problems.

The traditional garden artist, experienced in the lay-out of private and public gardens, in beautifying city squares and cemeteries or housing estates, is by no means trained to cope with pressing environmental problems of m u c h larger scale and impact.

It is the qualified Landscape Architect, educated in full academic programmes in Landscape Architecture in more than 150 universities in 40 countries, w h o by his special understanding of the interrelationships and interactions of the natural environment, will be able to influence and to guide politicians and the decision making processes of administra­tions and planning authorities at local, regional and national levels. H e is the only compe­tent and qualified professional for the optimal planning and design of public open spaces or urban green areas.

Strongly impressed by the high standard of design and maintenance of Osaka's urban green areas, I asked in a guided tour during IFLA's recent World Congress in Japan, h o w

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m a n y Landscape Architects were employed by the city; the answer was 128! W e were indeed overwhelmed by the progressive and consequent application of farsighted policies for the creation of adequate green spaces for the wellbeing of the fast growing megalopolis concentrations. The open competition between major cities like Tokyo , K o b e , Osaka, etc., concerning sizes and standards of design of their public open spaces, have created some of the finest, attractive and nature-oriented city environments of the present time.

Unfortunately, though these represent the exception rather than the rule. T o o m a n y major metropolitan areas in all parts of the world are totally lacking public green spaces, not to speak of logical green network systems, serving the population with shade trees on their streets, urban forests, green belts and corridors, providing physical and visual green contact with the urban fringe and the open landscape, allowing the penetration and flow of fresh air. The basic needs of the pedestrian, children and youth, mothers and babies and the elderly people to safely walk and play, are too often forgotten, when even existing urban green is sacrified and used for mitigation of pressing traffic problems.

It is not you, Ladies and Gentlemen, w h o m I must convince of the needs for safeguar­ding and conserving of natural environments within the city scenery, like urban river fronts and seashores, mountains and canyons and making them accessible for the enjoyment of the public and its requirements for sports and recreation.

It is during the early stages of masterplanning, when basic design concepts are born and approved, when land use policies are applied, when green areas are designated as such, their sizes, locations and qualities fixed, that the indispensable input of the Landscape Architect is needed, if it is not for the beautification and make-up of flower beds in traffic islands and similar tasks, when his service is wanted.

I shall n o w try within the very limited time, to show you some projects of urban Landscape Architecture which, I a m sure, are not considered by you to be typical projects for Landscape Architects.

Before ending, Ladies and Gentlemen, I would like to draw your attention to the important fact that Landscape Architecture is an established, internationally recognized profession in its o w n right. The International Labor Office in Geneva in its «International Classification of Occupations» lists under the heading «Architects and T o w n Planners» —three professionals, The Building Architect, The T o w n Planner and The Landscape Architect, defining clearly their particular fields of activities.

The International Federation of Landscape Architects is n o w making strong efforts to introduce this important profession into m a n y more countries. I F L A supported Regional Training Centres in Landscape Architecture are being established in South East Asia, Africa and Latin America.

I a m glad to report that serious efforts to establish an academic programme in Land­scape Architecture at one of Madrid's Universities are n o w m a d e and are practically sup­ported by I F L A in the hope that it will be in operation in the near future.

Thank you!

72

LA PERCEPCIÓN DEL VERDE URBANO Y PERIURBANO

F e r n a n d o Gonzá lez Bernáldez Departamento de Ecología. Universidad Autónoma de Madrid

El fenómeno del «verde urbano» en sus variadas manifestaciones (árboles callejeros, par­ques, jardines, patios, céspedes, setos, macetas, plantas de interior, etc.) plantea numerosos interrogantes. ¿Qué causas tienen esas persistentes costumbres ciudadanas? ¿Qué impulsos mueven a los habitantes de las ciudades a defender y conservar los engorrosos y caros espacios verdes frente a tantas dificultades? ¿Qué fuerza misteriosa impulsa a miles de personas a abandonar las aglomeraciones los fines de semana rumbo a los espacios naturales?

La respuesta parece residir en el valor terapéutico de la frecuentación de esos espacios o de la contemplación de esos objetos. Aunque existen relativamente pocas publicaciones sobre estos aspectos de la interacción hombre-naturaleza (ejemplos: Danilova, 1971; Tie-der, 1975; Ulrich, 1979, 1981), hay cierto acuerdo sobre la utilidad restauradora o reequili-bradora de esos hábitos urbanos. Sin embargo, las formas en que la gente utiliza las zonas verdes son m u y variadas. M a r k (1984), por ejemplo, ha estudiado las diferencias de actitu­des, motivaciones y personalidad de los usuarios de huertos (community gardens) y par­ques públicos (public parks). En ese tipo de huertos los usuarios pueden trabajar la tierra e interaccionan más con el entorno. La investigación refleja notables diferencias entre ambos, como es también el caso para distintos tipos de usuarios de las zonas periurbanas ( I C O N A , 1975). En éstas las diferencias se establecen entre el grado de urbanización y equipamiento admitido y la densidad de frecuentación humana que los visitantes toleran.

Entre los numerosos aspectos de las zonas verdes, los visuales o estéticos son proba­blemente los peor conocidos. Por su universalidad e importancia merecen una mención especial al introducir el problema de la percepción de los espacios verdes.

En relación con los efectos «terapéuticos» del medio visual deben mencionarse fenóme­nos psicofísicos como el efecto Ulrich (Ulrich, 1975, 1981), producido por la contempla­ción de la vegetación y del agua. Consiste en la disminución del stress y la inducción de un estado de relajación lúcida o de disponibilidad, reflejado en la mayor emplitud de las ondas alfa del electroencefalograma. Esos fenómenos concuerdan con el carácter reposante y restaurador que las civilizaciones urbanas han atribuido a la «naturaleza» y —proba­blemente— tienen que ver con las virtudes salutíferas que todas las culturas otorgan a las plantas.

Pero esos aspectos de contenido, de materia prima, que el agua y sobre todo la vegeta­ción poseen van acompañados en el espacio urbano de aspectos formales: modos de pre­sentación y configuraciones diversas. Los experimentos de percepción y preferencia (Gon­zález Bernáldez et al, 1973; Shafer y Brush, 1977; González Bernáldez y Parra, 1979; Kaplan y Kaplan, 1982; González Bernáldez, 1985, etc.) permiten concluir que el agrado producido por una zona verde es una respuesta a combinaciones de características de ambos tipos. D e forma resumida, los ingredientes de la estética de la zona verde se siste­matizan en el cuadro (Abelló, Gallardo, González Bernáldez y Ruiz, 1986).

A la vista de las características expuestas en el cuadro puede atisbarse que la estética del espacio verde posee la significación etológica de manifestación de un sistema efectivo que guía y aconseja la exploración del entorno.

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Desde fecha temprana, el hombre aprendió a suscitar esos sentimientos manipulando el ambiente construido. Así, podemos considerar la jardinería, el paisajismo y gran parte del diseño arquitectónico y ambiental c o m o formas no verbales de comunicación que utilizan combinaciones de los mencionados ingredientes para inducir determinados estados de ánimo. Los experimentos permiten observar los efectos de la adición de esos componentes. Por ejemplo, un efecto importante de ciertas combinaciones con las connotaciones «securi-zantes, tranquilizantes versus estimulantes, inquietantes», que pueden dar a la escena y que tienen que ver con la producción de distintos tipos de tensión o arousal (por ejemplo, mediante el mayor o menor predominio de la simetría, de la estructuración, de la repeti­ción previsible o, por el contrario, del misterio, del desorden, de la imprevisibilidad, etc.). Algunas de estas combinaciones estereotipadas han constituido «estilos».

Desde nuestro punto de vista nos interesa especialmente que las combinaciones refleja­das en los distintos estilos o versiones de la zona verde actúen de manera diversa sobre los espectadores según su edad, características socioculturales, intenciones, etc. (Maciá, 1979, 1980; Abelló y Bernáldez, 1986). Esas diferencias recuerdan algo las relaciones observadas en el caso de la pintura artística (Frances, 1979).

Existen notables diferencias según edad y cultura. Por ejemplo, los niños prefieren entornos cognitivamente más sencillos que los adultos. Los niños de menos de trece años rechazan los efectos de sombra y misterio en la escena, prefiriendo situaciones bien y uniformemente iluminadas, m á s informativas, aunque sean m á s triviales. Los agricultores manifiestan preferencias por espacios verdes m á s ordenados y previsibles que los universi­tarios. Las personas que puntúan bajo en las escalas de «control» o «estabilidad emocio­nal» prefieren escenas estructuradas y con ritmos o pautas (pattern) reiterativas, etc.

Podríamos concluir que las preferencias ambientales, y concretamente las referentes a las zonas verdes, son manifestaciones de estrategias personales más generales. N o son sólo estilos de la forma de «gustar», sino también, con frecuencia, de la «forma de ser», mere­ciendo por ello atención y respeto.

El estudio de la percepción ambiental sirve para reforzar los argumentos a favor de un diseño menos tecnocrático y m á s atento a las percepciones y demandas de los ciudadanos. Junto a los factores de carácter botánico, biofísico, tecnológico y económico, el diseño y la gestión de los espacios verdes urbanos deben incorporar aspectos socioculturales, funda­mentalmente del c a m p o de la percepción y educación ambientales. L a planificación y di­seño de esos espacios debe tener en cuenta la percepción ambiental de los ciudadanos; por ejemplo, crear posibilidades variadas para distintos tipos de percepción y facilitar la parti­cipación. La educación es también un requisito de la gestión. C o n la ayuda del conoci­miento de la percepción puede evitar m á s fácilmente la manipulación y la aculturización. L a educación ambiental debe prestar atención a aspectos etológicos y psicológicos de la relación hombre-entorno. Puede así propiciar la participación y enriquecer y potenciar las capacidades de uso y disfrute de los recursos urbanos.

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C o m p o n e n t e s formales y de contenido en la estética de las zonas verdes*

a) Aspectos de contenido (Cualidades intrínsecas de los componentes de la escena.) Sus efectos dependen en parte del significado

que les atribuyen los espectadores según su experiencia, edad y características socioculturales: — Vegetación sana y vigorosa. — Agua limpia. — Formas agresivas, relieves abruptos, etc.

b) Obstáculos o facilitaciones del proceso cognitivo relacionados con la producción de tensión (arou­sal) que tiene efectos hedónicos: INSPECCIÓN

Papel de información abstracta: — Diversidad, número de elementos, etc. (función de Shanon). — Pattern, ritmicidad, simetría, simplicidad de forma (funciones de pattern). — Contraste, estructuración, segmentación, etc.

IDENTIFICACIÓN. RECTIFICACIÓN Papel de la información semántica o reica. — Misterio. Conciencia de información conspicuamente oculta. Barreras visuales, niebla, oscuri­

dad, etc. Transparencia de primeros planos. — Separación del fondo, individualización versus marañas, legibilidad estructural. — Incongruencia, sorpresa (falta de redundancia semántica).

* Según Abelló. Gallardo, González Bernáldez y Ruiz, 1986.

BIBLIOGRAFÍA

A B E L L Ó , R . P. , y G O N Z Á L E Z B E R N Á L D E Z , F.: «Landscape Preference and Personality». Landscape Planning, 13, 19-28, 1986.

A B E L L Ó , R . P.; G A L L A R D O , L . ; G O N Z Á L E Z B E R N Á L D E Z , F., y Ruiz, J. P.: «La teoría de la información y la estética de las zonas verdes». (Presentado en la sesión de posters de este Seminario.) 1986.

D A N I L O V A , N . A . : Priroda i nashe zdorov'e (Naturaleza y Salud). Izdatiel'stvo Mysl. Moscú, 1971.

FRANCES, R . : Psychologie de l'art et de l'Esthétique. P U F , Paris, 1979. G O N Z Á L E Z B E R N Á L D E Z , F.: Invitación a la ecología humana. La adaptación afectiva al

entorno. Tecnos, Madrid, 1985. G O N Z Á L E Z B E R N Á L D E Z , F., y P A R R A , F.: Dimensions of Landscape Preferences from

Pairwise Comparisons. Proceedings of the Nat. Conference on Applied Techniques for Analysis of the Visual Resource. U S D A . Forest Service. Incline Village, Navada, 1979.

G O N Z Á L E Z B E R N Á L D E Z , F. ; S A N C H O R O Y O , F., y G A R C I A N O V O , F.: «Analyse des Rections au Paysage Naturel». Options Mediten amenes, 17, 66-81, 1973.

I C O N A : «Ordenación integrada de los montes de Cercedilla y Navacerrada». ICONA Monografías, 1. Ministerio de Agricultura, 1975.

M A C I Á , A . : Visual perception of Landscape. Nat. Conference on Applied Techniques for Analysis & Management of the Visual Resource. U S D A Forest Service. Incline Village, Nevada, 1979.

M A C I Á , A . : «Paisaje y personalidad». Estudios de Psicología, 1:31-38, 1980. M A R K , F.: A comparison of different meanings attached by users to a public park and

community garden. 8th Internat. Conference on Environment and H u m a n Action IAPS. Internat. Assoc, for the Study of People and their Phisical Surroundings. IAPS, Berlin, 1984.

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S H A F E R , E . L . Jr., y B R U S H , R . D . : « H O W to measure preferences for photographs of natural landscapes». Landscape Planning, 4, 237-256, 1977.

TlEDER, K h . 0 . : Lies i otdykh (El bosque y el descanso). Izdatiel'stvo «Liesnaya Promysn-lienost'», Moscú, 1975.

U L R I C H , R . S.: «Visual landscape and physiological wellbeing». Landscape Research, 4, 17-23, 1979.

U L R I C H , R . S.: «Natural versus urban scenes. Some psychophysical effects». Environment and Behavior, 13, n u m . 5, 523-556. 1981.

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LA TEORÍA DE LA INFORMACIÓN Y LA ESTÉTICA DE LAS ZONAS VERDES

Rosa P. Abelló Fernando G . Bernáldez

Dolores Gallardo Juan P. Ruiz

Departamento de Ecología de la Universidad Autónoma de Madrid y Facultad de Bellas Artes de la Universidad de La Laguna

Este texto corresponde al contenido del poster presentado por los autores en el Seminario Internacional sobre Uso, Tratamiento y Gestión del Verde Urbano, organizado por el Programa M A B ( U N E S C O ) y el Ayuntamiento de Barcelona en esta ciudad del 21 al 24 del mes de abril de 1986. D a d a la dificultad de reproducción de las imágenes que lo ilus­traban (veintiún pares de figuras con fenómenos contrapuestos y once imágenes individua­les) se ha optado por la transcripción directa intentando precisar, en lo posible, los ejem­plos con comentarios adicionales.

Introducción

Varios experimentos, desde la época de Moles (1957) y Berlyne (1965) hasta la actualidad, pasando por las contribuciones de Francés (1968), Wohlwill (1976), Kaplan y Kaplan (1982) y de los autores de este trabajo (Bernáldez, 1985; Abelló y Bernáldez, 1986), han mostrado la influencia de los factores cognitivos en la valoración estética. Aquí se han sistematizado los factores cognitivos que, c o m o se ha comprobado experimentalmente, intervienen en la valoración estética de paisajes y zonas verdes, relacionándolos con la teoría de la información (ver tabla).

La estética de las zonas verdes está determinada en gran parte por las reacciones afecti­vas que guían la exploración y el reconocimiento de entornos naturales. L a regularidad más importante encontrada consiste en que el óptimo de preferencia estética aparece en zonas intermedias de una polaridad, «seguridad, predecibilidad, certidumbre versus estí­mulo, desafío, misterio».

L a posición exacta del máx imo en el gradiente depende en forma coherente de caracte­rísticas socioculturales del sujeto: edad, sexo, personalidad psicológica (factores de «con­trol» y estabilidad emocional, por ejemplo), actividad profesional y nivel cultural.

La combinación de ambos tipos de actitudes extremas tiene un importante carácter adaptativo en sentido darwiniano. Este fenómeno está vinculado con el comportamiento exploratorio que los individuos manifiestan hacia el entorno.

Inspección

Se refiere exclusivamente a la información abstracta contenida en la escena. Resulta afec­tada por la complejidad de ésta. Podemos distinguir dos tipos dç procesos:

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Sistematización de los principales factores cognitivos identificados experimentalmente

Producción de un mayor o menor grado de alerta, tensión («arousal»), etcétera, dependiendo de retardos y obstáculos o, por el contrario, de factores que facilitan el proceso cog-nitivo

Evaluación de cualidades intrínse­cas de los objetos identificados se­gún su significación para el sujeto.

Información abstracta contenida en la escena (intrafigural) 1. INSPECCIÓN

Comparación con memorias del su­jeto (información semántica o reica)

Evaluación con la ayuda de «me­morias» (adquiridas o innatas) con­dicionada por: — expectativas, intenciones — capacidades personales

2, IDENTIFICACIÓN

3. Evaluación de SIGNIFICADOS

Catalogación (evaluación de diversidad) de los elementos de la escena. Depende de la complejidad calculada mediante la fórmula de Shannon. Por tanto, influyen en ella:

— el número de elementos (por ejemplo, abundancia de árboles en una escena de u n parque;

— las frecuencias relativas de los diferentes elementos presentes (especies o formas de árboles, tipos de relieves, etc.);

— el contraste entre tonos, bordes netos, etc., que se podría considerar c o m o u n caso especial del proceso de catalogación.

Localización (ubicación) espacial de los elementos. Resulta afectada por pautas espa­ciales que pueden expresarse mediante las ecuaciones de detección de pattern. Son importantes:

— el pattern textural del conjunto de la escena determinando bandas y zonas m á s o menos bien diferenciadas entre sí (tipos de manchas de bosque...);

— el pattern rítmico con la presencia de estructuras repetitivas en configuraciones regulares (en troncos de árboles, hierbas, construcciones humanas , etc.);

— el mayor o m e n o r grado de simetría en la disposición de los elementos individuales (característico de algunos tipos de jardinería frente a los estilos m á s informales);

— la simplicidad de formas (expresable, en principio, por el grado de la función matemática que las pueda describir).

¡Identificación

Se refiere a la identificación de entidades presentes en la escena utilizando memorias adquiridas. Ei empleo de éstas refleja u n modelo de «redes» o enjambres de características asociadas que guían ia búsqueda automática de información latente (características débil-lïicïïie expresadas) o invitan a la búsqueda de información ausente. Resulta afectada por:

— 'mayor o m e n o r expresión de las características críticas o su interferencia con el ¡onao (ruido): cnpsis, camuflaje de objetos, etc.;

— grado de individualización de elementos concretos (por ejemplo, árboles diferencia­dos versus marañas);

— facilidad de comprensión de la organización estructural (árboles con ramas patentes que proporcionan mayor legibilidad frente a masas intrincadas donde no se hace patente la estructura interna);

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— la incongruencia o asociación incongruente de características (que contradiga las asociaciones memorizadas) o falta de redundancia semántica, sorpresa, novedad, etc.; por ejemplo, en combinaciones absurdas o raras de elementos o la presencia de un objeto extraño en una serie (como una señal de tráfico en un contexto exclusivamente silvestre);

— identificación de lagunas de información o de barreras (obstáculos a la adquisición de información) con producción de misterio o intriga por la conciencia de información no asequible inmediatamente.

El efecto «misterio« se puede inducir por la presencia de barreras visuales con vías de penetración (caminos en un bosque, cuevas...) o por obstáculos para la información c o m o la presencia de nieblas, oscuridad, etc. Es tratable por expresiones del tipo:

Información inmediatamente asequible

Información potencial (conspicuamente escondida)

Significado

N o tiene que ver con aspectos formales, sino de contenido. Se refiere a la evaluación afectiva (respuesta hedónica) de las cualidades de los objetos identificados, mediante c o m ­paración con memorias innatas o adquiridas.

E n la determinación de preferencias, estas memorias tienen un papel importante en los comportamientos individuales a través de:

— vivencias, aprendizaje, familiaridad con los temas; — intenciones y expectativas; — capacidades. A continuación se citan varios ejemplos de cualidades primarias de gran importancia

en la percepción ambiental: — la presencia de vegetación y el vigor y exuberancia aparentes de la biomasa vegetal

frente a formas desmedradas de árboles y arbustos; — la aparición de masas de agua limpia en el paisaje; — los signos de humanización, c o m o construcciones humanas, cultivos, jardines m u y

controlados, etc.; — la facilidad para la penetrabilidad en la escena a través de corredores visuales y la

presencia de elementos que sugieren posibilidades de refugio; — las formas vulnerantes y agresivas, por ejemplo, las ramas de árboles desprovistos

de hojas o plantas punzantes; — el relieve abrupto; — signos de frío por la apariencia de la vegetación, nubosidad, rasgos de paisaje de

montaña.

Combinación de características visuales

Los distintos factores mencionados se han usado empíricamente c o m o «ingredientes» en jardinería (diferentes estilos) y arquitectura paisajística para crear diferentes ambientes con connotaciones diversas. Los experimentos muestran que los factores mencionados se c o m ­binan entre si de acuerdo con determinadas reglas para producir respuestas afectivas (potenciándose o neutralizándose). Por ejemplo:

Pattern regular (INSPECCIÓN) + visibilidad de la escena sin obstáculos ( I D E N T I F I C A C I Ó N ) + signos de actividad h u m a n a ( S I G N I F I C A D O ) —*• Se refuerzan subrayando la polaridad «seguridad, certeza versus estímulo, desafío».

Los obstáculos o retardos en el proceso cognitivo (Inspección + Identificación) contri­buyen a la determinación del carácter estimulante, insecurizante del gradiente «seguridad versus estímulo» mencionado.

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BIBLIOGRAFÍA

A B E L L Ó , R . P. , y B E R N Á L D E Z , F. G . : «Landscape Preference and Personality». Landscape and Urban Planning, 13: 19-28, 1986.

B E R L Y N E , D . E . : «Medidas de preferencia estética». En J. Hogg (ed.), Psicología y Artes Visuales. Gustavo Gilí, Barcelona, 1965.

B E R N Á L D E Z , F. G . : Invitación a la ecología humana. Tecnos, Madrid, 1985. F R A N C É S , R . : Psychologie de l'esthétique. P U F , París, 1968. K A P L A N , S., y K A P L A N , R . : Cognition and Environment. Praeger, Nueva York, 1982. M O L E S , A . : Théorie de l'information et perception esthétique. Flammarion, París, 1957. W O H L W I L L , J. F.: «Environmental aesthetics: The environment as a source of affect». En I.

Altman and J. F. Wohlwill (eds.), Human Behavior and Environment, volumen 1, Nueva York, Plennun Press, 1976.

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EXPLORATORY SURVEY ON THE PERCEPTION OF VEGETATION IN SAO MIGUEL,

CITY OF SAO PAULO R o s a G r e n a Kliass

A n a Lucia A n c o n a d o A m a r a l (collaborator)

Introduction illustrated by the video

From the peak of the Jaragua mountains and the Cantareira hills, we have a view of the entire city of Sâo Paulo with its 1.500 sq k m , inhabited by 10 million people.

The site is composed of very diversified landscape components: — Floodplains: 720 m above sea level. — Hills: Of medium slope and are above 840 m above sea level. — In the North, the Cantareira hills are the natural limit for urban expansion. There

they reach 1.200 m above sea level. — The floodplain of the Tieté River is an average of 2 k m in width. It's landscape

potential is extremely compromised from the channelization of the river, by the heavily used freeways on its banks, and by producers of heavy pollution. The other important river, Pinheiros, has also been channelized and restricted by the freeways. Its floodplains however still have, in some areas, a more adequate land use for the site. Other areas have been intensely developed with skyscrapers that reach up to the banks.

— The ridge of the central hill is Avenida Paulista. This is the most expensive land in Säo Paulo.

The forests of the Cantareira hills cover 56 sq k m . All the water resources of this rich area are being used for the water supply of 40 % of the city's population. In spite of the steep slopes and the inadequate qualities of the site, it is under pressure from urban use.

In the South are two large reservoirs, Billings and Guarapiranga, followed by a sea of steep hills which give way to an immediate 700 m descent to sea level. The water resources in this region have tremendous potential for the entire metropolitan region, despite the fact that currently, the Billings reservoir in highly polluted by sewage. In addition to its water resource value, its landscape and recreation potential is extremely important for Säo Paulo.

This m a p indicates the land use of the metropolitan area: black: intense high-rise zone purple: industry purple with lines: areas used predominately for industry orange: garden neighborhoods red: emense areas of low rise development green: green areas

The central ridge, where urbanization began, is not only the geographical center of the metropolis but also its core. It's almost completely occupied by a dense mass of skyscra­pers, 30 m average height. It is both the financial and business district and the center of services distribution for the country.

O n the Southwest slope of the principle hill and on the Pinheiros floodplain are the main green neighborhoods of Säo Paulo. They are characterized by a very high pattern of

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Vegetation. In these areas are also some of the most important parks of the city, such as Ibirapuera and M o r u m b i .

This section of the city is inhabited by the majority of the high income-class people. It includes the best examples of architecture, urban layout, and quality of life of Sào Paulo. The pattern extends throughout the neighborhoods near the reservoirs to the South.

The reservoir region to the South is under extremely restrictive land use legislation. Nevertheless, because of its location and its easy accesibility by transportation, this region is being more densely used than the fixed limits. There is only one small public parking in this area, but m a n y private clubs.

The north-northeast slope is limited by the rivers Tieté and Tamanduatei. In the valley of the later is located an emense industrial park developed for the entire metropolitan region. It extends continuously m a n y k m to the southwest, far beyond city limits. The southwest direction of the valley coincides with the direction of the predominant winds, which carry industrial pollutants to the center of the city. The river has been completely channalized and covered by pavement. In its floodplains, near the industries, residential areas for the workers have existed historically, creating total impermeabilization and ari­dity of the landscape.

The East zone is the point of initiation of the entire drainage system for the Metropoli­tan area. It is highly compromised however because of its high soil impermeabilization. It represents the most important potential of urban expansion for the entire metropolitan region.

The industries in the Tieté valley are the heaviest polluters of the river. The sequence of hills and valleys in this region are densely occupied by low rise resi­

dences, creating an extremely monotonous pattern of horizontal landscape. This part of the perifery of the metropolis does not have the typical urban characteris­

tics of cities. There is no significant pattern of an hierarchy of streets, and no developed commercial center. This region is like a big camp , a dormitory city. O n e of the few centers is the center of San Miguel Paulista. Historically the oldest center of the region, it began in the 17th century as an Indian Village, around a plaza and the Jesuit chapel, n o w preserved as an historical m o n u m e n t . This plaza is the only commercial center and urban transporta­tion terminal for the region. It is a reference point of great importance. Only near this center is a reasonable urban pattern with paved streets, sidewalks, public lighting and a few street trees. The streets with very little traffic are intensely used by pedestrians.

The floodplains in this region are not yet completely developed. Besides providing good drainage conditions, they also provide green area reserves that are intensely used for recreation by the population. The community is organized in the traditional «floodplain clubs» for the practice of sports, mainly the popular soccer, which requires flat huge areas.

Cutting the entire region are streams which interrupt the continuity of the urban circu­lation. The very small and extremely precarious bridges are good examples of the entire picture of the lack of urban facilities. This region has no sewage, no pavement, few public transportation facilities, etc.

The characteristics of the streams are very diversified. S o m e of them are absolutely compromised from intense development. Others still have some potential for urban design, mainly those whose flood areas are still occupied by the traditional vegetable gardens. Unfortunately these areas are little by little disappearing because of the invasion of a low-rent class of population.

The housing demand has been traditionally satisfied by the population itself through self-construction m a n y times organized and supported by the community.

Nevertheless, some state programs are being developed, a m o n g which the most impor­tant is the Housing National Bank ( B N A ) for huge housing developments. In the East zone, a Corbusierlike pattern was created, completely inconsiderate of all physical limita­tions. It was an aggresive intruder on the landscape, resulting in erosion, deforestation, siltation of the rivers, and the creation of a landscape/environmental quality of very low quality. Entire cities were created on the perifery of the urban area without considering the lack of transportation and utilities. This solution has since been m u c h discussed, with the final consensus recognizing the inadequacies of this solution.

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The population of the East zone is constructed partly of inhabitants native to the region and partly.by immigrants from other parts of the country, mostrly from the North­east. They have very low buying power, and as a result create very unique characteristics of life in their activities and environment.

The few commercial streets are the only areas in which one can feel the intensity of urban life, and they are the only links with the metropolis.

The survey

As w e can see from the general characteristics of the city of Slo Paulo, the environmental quality of urban life is highly concerned with vegetation, more specifically, with the lack of vegetation.

It was for this reason that w e introduced vegetation as our first subject in The Program of Environmental Quality Patterns of the Secretary of Planning, beginning with an inven­tory of the significant vegetation in the entire city. Another was proposed to be developed and presented as a «Diagnosis of Vegetation as a Factor of Environmental Quality», which will include studies of:

— Vegetation by itself. — Vegetation and its relation with the Urban Environment. — Vegetation and the Relation of the Population towards it. W e are conscious that any action towards transforming this project into reality will

only be possible with community participation. For this reason, w e prepared and exploratory survey on the Perception of Vegetation

by the Population, in a limited area selected to be representative of the eastern region. The goal of this survey is to have more consistent hypothesis to be evaluated in the major study «Diagnosis of Vegetation as a Factor of Environmental Quality», testing techniques for further adaptations of future surveys.

The hypothesis that were considered elaborating this survey are as follows: 1. L o w level of knowledge and perception of vegetation by the population. 2. Effective relation between the level of perception and the following factors:

— rural or urban origin — social, economical and cultural level — level of knowledge of vegetation

3. L o w level of evaluation of the aspects relative to vegetation by the population. 4. Different approach of people towards the location of vegetation, i.e. in a public

space or in a private lot. Finally, w e wanted to evaluate h o w the population's expectations were to the follo­

wing: vegetable gardens, street trees, green areas, and vegetation in private lots. W e chose the Plaza of Sao Miguel as the point of focus for the survey, which consisted

of 96 interviews with dwellers distributed throughout three sections: — 100 m from the plaza — 100 m to 500 m from the plaza — 500 m to 1.000 m from the plaza This sample consisted 50 % of w o m e n and 50 % of m e n , all homogeneously distributed

by age group: 14-20, 20-30, 30-50, more than 50. One third of the interviews were m a d e on week days and two thirds on Sundays for a

more representative sample of the population —the majority work out of the region during the week.

The questionares were organized into six themes concerning the following aspects: 1. Characterization of the people interviewed. 2. Perception of Vegetation. 3. Relation with the Plaza. 4. Relation with vegetation. 5. Knowledge of vegetation. 6. Expectations towards vegetation in the Urban Environment.

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1. Characterization of the people interviewed: sex, education, profession, income level, and origin.

2. Perception of Vegetation: — Description of the usual itinerary made by foot emphasizing the trees. — Choose from two pictures and justify one of the houses that he would prefer

to live in (one had vegetation and the other one did not). 3. Relation with the plaza:

— H o w frequently does he go to the Plaza. — Description of the Plaza to someone w h o had never gone there. — If he likes it and why .

4. Relation with vegetation: — If he takes care of, had ever taken care of, or would like to take care of a plant,

tree, or vegetable garden and why. 5. Knowledge:

— H o w is a plant born and what does it need for its life. — M a k e a design of a tree and describe it verbally. — W h a t are plants useful for in your life. — Quote some names of trees. — Identify the trees presented in four pictures.

6. Expectation: — Eight pictures were presented of different spaces where he would think that

there should be put (more) trees, with priorities. — Where he generally would like to have more trees planted.

Conclusions and recomendations

In spite of being an exploratory survey with a relatively small sample, the results were surprisingly satisfactory, and in m a n y ways overlapped the initial expectations.

The results have internal coherence in relation to the most important aspects. Vegetation was recognized by everyone despite origin, economic level, or age as a struc­

tural component of the urban landscape, and was considered an important element to be introduced.

There is full conscience of the environmental benefits that vegetation brings to the city and the principal functions of vegetation quoted were its capacity of improving air quality and its aesthetic qualities.

In spite of the elementary level of the questions, the people inerviewed presented a very low level of knowledge of vegetation, knowing very little about the trees commonly used in our city.

The population as a whole is sensitized towards vegetation. The hypothesis that people of rural origin would present a rejectionist attitude as a result of the negative aspects of country life was proven false.

M o r e w o m e n take care of plants as well as w o m e n and m e n of more than 50 years old. The group of 14-20 years old was the one that presented the highest level of perception The image the people interviewed presented of trees is strongly linked with their ori­

gins, as expressed by the characteristics of the native vegetation of their regions seen in their drawings.

The people interviewed expressed themselves generally with evident enthusiasm and involvement, using expressions as: «vegetation makes life happier», «it gives more life», «gives peace and tranquility», «embellishes life», «helps to pass the time», «keeps one c o m ­pany and makes one cheerful», «gives oxygen and you can see the life», «if it was not for the vegetation the world would be in black and white», «if there were more trees people would be calmer», «in plants there is such wonder», «the smell of the green»...

W e observed a lack of balance between the great interest demonstrated by the popula­tion toward vegetation and the low level of knowledge. Therefore, w e see a very good opportunity to develop environmental education programs.

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W e recommend two different kinds of programs: Educational: in schools and through the mass media as well as a special program to

promote the vegetation of Sao Paulo with the more c o m m o n trees, their characteristics and their potential as conditioners of environmental quality. There is also an opportunity for a program to develop vegetable gardens in the schools for children.

The second category is to implement urban vegetation combining the introduction of trees and vegetable gardens with natural soil conservation for private lots, as well as for community land.

In this kind of program, w e think that the communities should also be asked to partici­pate in the planting and maintenance of street trees, plazas, institutional areas, and public spaces.

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THE LINKS BETWEEN ECOLOGICAL SCIENCE, LOCAL AUTHORITY ACTION AND COMMUNITY

INVOLVEMENT IN PLANNING AND LAND MANAGEMENT FOR NATURE CONSERVATION

IN BRITISH CITIES G . M . A . Barker

Nature Conservancy Council (Great Britain)

In any project designed to provide green space within a city or to manage existing green space in new ways there is a practical difficulty in making the link between, on the one hand, research ecologists and other environmental scientists, and, on the other, the local residents w h o will be directly affected by the project. That this link is needed is illustrated by schemes devised by local residents which have failed because basic ecological principles have been overlooked and others devised by ecologists which have failed because the needs of residents have not been taken into account. T o compound the situation, the local autho­rities which usually play a major part in any scheme have often been ignorant of —or have ignored— the advice and aspirations both of ecologists and of residents with the result that schemes satisfy the hopes and needs of neither. Although schemes can be found in most countries where all the interested parties have come together to give satisfactory end-products, it is true to say that nowhere is the system even consistently good —let alone perfect. Each country will have elements which m a y help others to improve their o w n systems and it is in this spirit that the way in which the problem is approached in England is described. It is by no means entirely satisfactory but it does contain useful pointers towards a system which is.

It is accepted that in most circunstances it is the local authorities which are the key organisations. They control the planning of cities, they are responsible for development controls, for a great deal of direct management of land, for the reclamation of derelict land, for social services, education and housing and for a wide range of other services. They are in a strong position to co-ordinate activities at local level. However, recent stu­dies have shown a wide range in the importance placed on nature conservation by local authorities in England. Interestingly, it is often the urban authorities which place the great­est emphasis on it (Tyldersley 1986). The first step in England has therefore been to ensure that some link is made between ecologists and the local authorities.

In 1949 the Nature Conservancy Council (from 1949-1973 k n o w n as the Nature C o n ­servancy) was brought into being as an agency of central government with the job, amongst others, of informing local authorities of sites of special natural interest in their areas and of advising local authorities of the effects which their policies and actions might have c *he fauna and flora of the area. It has been possible to build on this foundation over tli. past 37 years for a number of important reasons. First, the Nature Conservancy Council was largely the product of concern expressed by university scientists over the accellerating loss of wildlife habitat. F r o m the earliest days there have been strong links between the research scientists and the Nature Conservancy Council. Although the degree of contact has ebbed and flowed over the years it has been increasing recently over urban

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ecology. Secondly there have been similar close contacts between the strong voluntary natural history societies and nature conservation trusts and the Nature Conservancy Council. In fact these close links with the voluntary sector are remarkable in a central government agency. Thirdly, some of the advice given by the Nature Conservancy Council to the local authorities is statutory advice —the Nature Conservancy Council must by law give the advice and the local authorities must by law take it into account in reaching decisions (National Parks and Access to the Countryside Act 1949; Wildlife and Country­side Act 1981; T o w n and Country Planning Act 1971; General Development Orders 1983). The compulsory links have, of course, meant that opportunities exist for wider consulta­tion and discussion. Fourthly, the way in which the Nature Conservancy Council has built up its operations is based on a network of local officers w h o have general responsibility for the area allocated to them; whose job it is to k n o w and to talk to all relevant people and organisations in their area; and whose work in more akin to that of a parish priest than to that of a bureaucratic centralised government department. It is hard to over-emphasize the importance of this close personal relationship, where a Chief Planning Officer, instead of getting an official letter beginning «Dear Sir, re your Structure Plan proposals, the view of the Department is...» is more likely to get a phone call along the lines «Look Jack, I'm not too happy about bits of your Draft Plan. C a n w e meet for lunch to have a chat about it». Or where a voluntary organisation with a grievance or a problem can inmediately contact someone they k n o w n well to come to discuss it with them.

The Nature Conservancy Council has two other important functions in relation to local authorities and ones which it has not really come to terms with. First, to help to give the local authorities the right political climate in which to promote nature conservation in urban areas and to ensure that the statutory backing is there for them. Secondly, to encou­rage an holistic approach in which local authority departmental boundaries are breached. The Nature Conservancy Council's main links have been with planners. It is n o w essential that encouragement is given to other operational sections within local government.

It should be emphasized that the Nature Conservancy Council's role is primarily as adviser and stimulus to local authorities. The executive action is largely the function of the local authority itself.

The Nature Conservancy Council therefore gives a valuable link between scientists, the planning system, land managers and the voluntary organisations. It is the voluntary orga­nisations which begin to m a k e up the next strand in the connection between scientists and local residents. While it has been traditional in Britain, certainly since the last part of the 18th century, that natural history societies have flourished, it was not until the 1960s that a widespread system of voluntary organisations interested in nature conservation was esta­blished. This has been in effect a voluntary equivalent of the Nature Conservancy Council with close links to the Nature Conservancy Council, with m a n y of the same range of contact organisations, with a policy of the safeguard of rare species and sites of special natural interest and with a membership drawn largely from the well educated middle clas­ses. The Trusts for Nature Conservation have been effective in their chosen role and, by involving local people, have helped to generate a degree of political awareness which the Nature Conservancy Council as a government agency cannot hope to do. However, the Trusts as originally conceived had little involvement in the major urban areas. Since 1980 there has developed a parallel voluntary movement in urban areas; sometimes originating from existing Trust groups, sometimes arising a m o n g groups of concerned professionals —landscape architects, university staff, naturalists involved professionally in planning or land management— and sometimes as popular movements which tap the concern for the local environment felt by m a n y people and often generated by some kind of local crisis. These Urban Wildlife Groups tend to involve young people, are vigorous and constructive pressure groups, have few aspirations to o w n land, operate largely through publicity gain­ed through the Press, radio and T V , help to co-ordinate small scale local initiatives and so on. They aim at involving local people in improving their o w n environments and seek to link ecological objectives with social objectives. Their activities have done a great deal to bring nature conservation and its social and economic benefits very directly to the atten­tion of local politicans and have been of great value in so doing. Of all the organisations

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directly involved in nature conservation they are closest to the people w h o live in our cities and are the most likely to involve inner city residents, the poor, needy and disaffected in direct action to improve their environments. They can help the local authorities substan­tially in this respect. Conversely, they can bring a high degree of ecological and practical expertise to bear on local problems and are able to tap into the Nature Conservancy Council and local authority networks more effectively than isolated groups of local resi­dents can.

This is the basic system operating n o w in England. There is one major flaw in it to which w e will return. However, it will be useful to examine first the trends in policy which this system has generated and h o w policies and projects are operated.

A s with the system, so with the policies. The view prevalent at the end of the 1940s that the rigorous protection of sites of especially high interest from development in the form of industry, housing, road building, mineral extraction and so on, should be the basis for nature conservation was founden on the illusion —soon to be rudely shattered— that agriculture and forestry would continue to provide the matrix of high quality wildlife habitat that they had done. Policies for nature conservation based on the safeguard of the rare, the fragile, and the integrity of the larger fragments of seminatural habitats remaining in Britain ignored the cities because here no rare, fragile or large fragments of the classical habitats remained (Ratcliffe 1977). While cities continued to interest a few eccentric natu­ralists they were not seen as particularly relevant to nature conservation and certainly not as high priority areas.

In spite of the great inroads m a d e by modern agriculture and forestry on the country­side which have m a d e cities m u c h more important in relative terms as resources for wildlife than they were 40 years ago and in spite of the greater appreciation which ecologist have of the intrinsic value of urban habitat types, it is fair to say that cities are still of little account in the terms defined for nature conservation in the late 1940s or by Ratcliffe. W h a t has changer significantly is the definition of nature conservation itself —or rather w e have rediscovered and reemphasized the h u m a n social elements of the earlier definition which became submerged in the practicalities of nature conservation programmes in the 1950s-1970s ( C o m m a n d 7122, 1947). For programmes of nature conservation in cities, although the identification and protection of sites of particular value for their wildlife and habitat types is an important facet of work, of perhaps greater importance is the realisation that greenspace improves environmental quality in a number of ways, that informal greenspace with spontaneous vegetation and associated wild fauna has some economic benefits, and that people enjoy seeing nature around them and value this contact highly. This has led to a redefinition of what the purpose of nature conservation is in the context of cities. It is to protect sites of high intrinsic importance. It is also to give residents ready access to a rich and varied fauna and flora so that they can enjoy it, and to provide a pleasant and easy to maintain setting for housing and industry. Having accepted that people want and need ready contact with wildlife, it follows that where parts of cities are deficient in accessible wildspace steps must be taken to provide it (West Midlands County Council 1984). It also follows that the management of land held on behalf of the community should be reassessed to take the needs of wildlife and the demands of people both of it and for it, into account.

There is a risk that the development of the philosophy and the groups referred to above together with increased public interest and political awareness will lead to frenetic activity with inadequate planning and consideration for long-term maintenance of projects, dupli­cation of effort, conflict between different interests and waste of energy. These risks are redoubled w h e n nature conservation programmes are seen as contributing to the structural and social regeneration of inner cities and as such are given considerable capital resources at short notice.

For these reasons the Nature Conservancy Council has been pressing for the develop­ment by the local authorities of strategies for nature conservation which will give a frame­work into which individual projects can be fitted and which will give clear policy guidance to those concerned with development as well as to those concerned which nature conserva­tion. With the publication of the West Midlands County Council's Strategy for Nature Conservation 1984 a considerable number of local authorities in England have seen the

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benefits and possibilities of similar non-statutory planning documents. The voluntary organisations welcome this approach too since it not only gives a structure to their work and opens up constructive dialogue at m a n y levels, but also, based as it is on systematic survey and analysis of data, it gives a body of information which can be built on and used for monitoring the effect of policies. A strategic plan helps to define roles more clearly and identifies key linkages between the various organisations concerned. For local politicans it identifies the main areas where action is need and makes the connection between the rather abstract concept in political terms that «nature conservation» represents, and the m u c h less abstract matterns of provision for informal recreation, improved prospects of attracting new industry, reduction of expenditure, and other matters of concern to their constituents. The realisation that rather than asking politicians to choose between flowers and providing jobs, nature conservation is saying that without flowers there are less likely to be jobs is slow to achieve but is well worth achieving. Nature conservation can also give a fresh impetus to community regeneration by mobilising people to care for their o w n environ­ment.

It is valuable to see whole city strategies for nature conservation as one level in a hierarchy of plans which extend in the case of England from the World Conservation Strategy, through the Nature Conservation Strategy for Great Britain, whole city strategies, district strategies and neighbourhood plans, to individual site management plans.

So far as the traditional aspects of nature conservation are concerned there are well tried and tested systems for habitat classification and mapping and for the evaluation of sites (Nature Conservancy Council 1986). While these are always open to improvement they are familiar tools of the trade and are adaptable to all levels of survey (Rieley and Page 1985). The use of remote sensing techniques for detailed survey as well as for the survey of large areas is being developed, but simply provides a different way of obtaining the same data which ground survey does. It does not materially affect the system of classi­fication or evaluation. These systems lack the sophistication of others which are currently being used on the continent of Europe and this is a substantial disadvantage when such surveys are used for purely ecological studies. Here this is not our concern and it is the case that even the simplified system is frequently seen as too detailed for strategic planning purposes —although appropriate for site management planning purposes. Indeed it is the case that for whole city planning scales Landsat 5 imagery with its 3 0 m pixel is quite adequate assuming that there are adequate ground controls. W o r k done in St Louis, Mis­souri, would tend to support this view. (Missouri Dept of Conservation 1985.)

T o the ecological survey data must be added a long list of planning information ran­ging from proximity of features to schools, to existing planning consents for development. O f these planning considerations those relating to provision for informal recreation are probably the most significant, since provision for such recreation and provision for nature conservation are closely linked in urban areas. The Recreation Plan for Cape T o w n , S A , (City Engineer, Cape T o w n 1982) and the Nature Conservation Strategy for Tyne and W e a r , U K , (Tyne and W e a r County Council 1986) illustrate this.

However, what is generally lacking from all these plans and also from the programme planning of most, if not all, of the organisations involved is any adequate investigation of the perceptions, needs and hopes of the people at w h o m the whole operation is aimed. Without thorough knowledge of these there is a risk that a paternalistic approach will be taken at best, and that, at worst, something totally against the wishes of local people will be imposed upon them. Importantly such investigations illustrate very clearly where educa­tional, promotional and publicity programmes need to be targetted. The gap in understand­ing between ecologists and planners is small compared with the conceptual chasm between either of these groups and the public in our inner cities.

It is vital that the links are m a d e and understanding is reached. People are certainly not apathetic towards nature conservation. Surveys in the U S A and in Canada have shown that between 40 % and 60 % of the population m a k e direct use of wildlife for quiet enjoy­ment —observing it, photographing it, feeding it, studying it (US Dept. of the Interior 1982; Filion et al. 1983). It is illustrative of the problem referred to that no comparable figures are available for the U K , but it is probable that these trans-Atlantic ones apply.

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However, the limited experience w e have in sounding out public attitudes shows first, that different groupings of the public have very different values when it comes to nature con­servation and, secondly, these groupings have very different perceived needs of their immediate environment, which apply as m u c h to the long term and stable elements as they do to the ephemeral fads, for example in the play of young people.

It is beyond the scope of this paper to look at the methods which can be used for this kind of survey. Suffice to say that it is m y opinion that the traditional questionnaire sur­vey, while useful in playing political and statistical games, can be both dangerous and inadequate for these purposes when used in isolation. Group discussions give a better in-depth view, but are costly, not amenable to statistical treatment, timeconsuming and, in inexpert hands, potentially damaging to participating individuals. It is likely that a combi­nation of questionnaire survey and group discussion, with feedback loops, is the most profitable approach, particularly when this can be supplemented by observations in the field. It is extremely important to accept that any studies of this .kind will give no answers to planners, land-managers or ecologists. They are very useful politically, especially if extended into the realms to economic return and if they are large-scale-as are the U S A and Canadian examples quoted. However their real value must lie simply in giving important clues to what the answers w e are all seeking m a y be and so to give direction to program­mes and policies. They also have a value in giving some very salutory shocks to those of us w h o have been in the business long enough to think that w e k n o w all the answers-but not long enough to have realised that w e do not!

A s has been said, little such work has been done in England for urban areas. This is the serious deficiency in the system referred to earlier in the paper.

T o carry the English programme forward the following matters are seen as important: 1. Investigations of the perceptions different groupings of urban residents have of

nature conservation and of the uses made of wildspace. 2. A higher level of promotion and publicity for nature conservation in urban areas. 3. Development by local authorities of nature conservation strategies for their areas. 4. Added support (financial and technical) for the voluntary organisations. 5. Development of programmes of survey and monitoring at all levels. 6. Ensuring that the professional training of planners, land-managers and other key

groups within local authorities includes training in ecological principles. 7. Provision of adequate technical, promotional and educational literature. 8. Review of research in urban ecology and commissioning of research to fill obvious

gaps. Together with some internal adjustments relating to staffing levels and section respon­

sibilities these eight points are the basis for the Nature Conservancy Councils o w n pro­gramme for the next five years.

In conclusion I would add one further comment . This field of work is one which invol­ves many nations. The problems w e all face, whether they be ecological, political, ones of practical land management, city planning or social regeneration, m a y differ in detail but are broadly similar world-wide. Not only can w e learn a great deal from one another but w e can by co-ordinating our efforts arrive more speedily and at less cost at workable solutions. In hepling to develop the programme for nature conservation in urban areas in England I have been greatly assisted by work being done in other countries. Conversely, w e in England have a lot to offer to other countries and I would urge people to visit us to see at first hand what w e are doing. Although a taste of what is going on can be gained from our quarterly news-sheet «Urban Wildlife News» which is available'at no cost to interested people overseas, it is best to see the projects for yourselves.

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B I B L I O G R A F Í A

City Enginelers's Department, Cape T o w n 1982. Greening the City: Open Space and Recreation Plan for Cape Town. Report num. 214/1982.

FlLlON, F. L . , el al: The Importance of Wildlife to Canadians. Canadian Wildlife Service, 1983.

H M S O : Conservation of Nature in England and Wales: Report of the Wildlife Conserva­tion Special Committee. C o m m a n d 7122, 1947.

H M S O : National Parks and Access to the Countryside Act, 1949. H M S O : Town and Country Planning Act, 1971. H M S O : Wildlife and Countryside Act, 1981. H M S O : Town and Country Planning Act [General Development] Orders, 1983-85. Missouri Department of Conservation: Personal communication from David Tylka,

Urban Biologist M D C , 1221, South Brentwood Road, St Louis, Missouri 63 117. Use of Landsat 5 imagery for open space mapping in St Louis, 1985.

Nature Conservancy Council: Habitat Mapping Manual (Phase 1), 1986. R A T C L I F F E , D . A . (ed): A Nature Conservation Review. Cambridge University Press,

1977. RlELEY, J. 0 . , and P A G E , S. E . (eds.): Botanical and Vegetation Survey of the City of

Nottingham. James Davies and Partners, Beeston, Nottingham, 1985. TYLDERSLEY, D . : Gaming Momentum: an analysis of the role and performance of local

authorities in nature conservation. Pisces Publications, 1986. Tyne and Wear County Council. Draft Nature Conservation Strategy for Tyne and Wear,

1986. U S Department of the Interior, Fish and Wildlife Service and U S Department of C o m ­

merce, Bureau of the Census, 1982: 7950 National Survey of Fishing, Hunting and Wildlife-associated Recreation. U S Govt. Printing Office.

West Midlands County Council: The Nature Conservation Strategy for the County of West Midlands, 1984.

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ROLE DES ESPACES VERTS URBAINS ET PERI-URBAINS DANS LE MAINTIEN

DE LA SANTE ET DE LTDENTITE DE L'HOMME Claude Leroy

Coordinnateur du projet MAB-11 (France)

L ' h o m m e : nature et culture

E n règle générale, les espaces verts urbains sont conçus par les urbanistes c o m m e la garni­ture autour du rôti, le persil dans les narines de la tête de veau. Les espaces verts et ouverts ne sont là que pour mettre en évidence le «plein» de l'urbanisme, le fond sur lequel se greffe la figure urbaine. Coneu ainsi, c'est un élément secondaire du paysage urbain. A la rigueur (et ce n'est pas négligeable) c'est un écran contre les bruits ou pour cacher les autoroutes.

E n fait, pour que l'effet anti-bruit soit efficace, il faut plusieurs dizaines de mètres de plantations denses.

Il ne faut pas traiter les espaces verts de fapon disjointe de l'urbanisme. Voici un exem­ple d'analyse de système sur le bruit para rapport à la promiscuité dans les grands ensem­bles et leur relation aux espaces verts.

Ailleurs, autour des Villes Nouvelles, ils vont constituer un facteur attractif modifiant le turn-over de la population, facilitant le mitage péri-urbain et empêchant l'appartenance au groupe au centre de la ville (Ville Nouvelle du Val de Reuil).

Je voudrais montrer que les fonctions des espaces verts telles qu'elles résultent de l'usage et de la représentation chez l 'homme sont beaucoup plus importantes.

L ' h o m m e est «nature et culture» et sa santé au sens positif de l ' O M S en dépend. J'ai montré ailleurs que «Santé» et «Identité» constituent le m ê m e concept et que la

notion de territorialité y est attachée. Mais, il n'y a pas que l'espace, l'espace vert pour les habitants est le lieu du temps non

contraint, donc en relation avec les désirs et motivations, les loisirs (et leur augmentation actuelle). Pour analyser les espaces verts, il faut alors faire des études de budget-temps d'autant plus importantes qu'elles vont déboucher sur la civilisation post-industrielle de l'an 2000 où le temps non contraint augmente.

Cette réorganisation du temps apparaît, c o m m e par hasard, au m o m e n t où l'on se préoccupe davantage des espaces verts. Ce n'est pas une coïncidence fortuite.

Fonctions des espaces verts non spécialisés ou faiblement aménagés

Elles vont répondre aux demandes des citoyens pour le corps et l'esprit dans son temps non contraint.

Le jeu est la fonction la plus importante du m o n d e . C'est à travers lui (chez l ' homme c o m m e chez le chien ou le chat) que vont se former les apprentissages de la réalité que devra affronter l'adulte que ne doit pas non plus être privé de jeux pour pouvoir imagni-ner, créer, progresser. L'enfant va utiliser les bacs à sable, les bassins d'eau de faible pro­fondeur, les petits aménagements du mobilier urbain. Mais, c o m m e l'a bien montré M . J. Chombart de Lauwe, quelle que soit la qualité des équipements proposés, l'enfant trans­gressera toujours pour manifester son identité.

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Le jeune enfant vit dans un espace ouvert où le Dedans et le Dehors se mélangent. Sa référence spatiale est sa mère et les distances d'exploration dangereuse et de proximité sécurisante vont se modifier avec agrandissement petit à petit de l'espace d'exploration par rapport à la mère. C'est dans l'espace vert, avec les oiseaux et d'autres animaux qu'il va prendre contact avec la nature et commencer ses premiers pas vers l'autonomie et la cons­truction de son identité. Les surfaces d'eau, les jeux avec l'eau l'attirent particulièrement. Les bacs à sable sont un autre élément important.

Les aménagements ne sont pas négligeables, mais en fait, ils répondent peu, en dehors de l'action de grimper, sauter, aux demandes de l'enfant qui doit plus s'exercer à la créati­vité qu'à la consommation.

Chez l'adulte, le sport est aussi essentiel pour maintenir le corps en état. La vogue du jogging le montre bien (avec tous ses excès pour la santé que fait des

nombreux troubles cardiovasculaires et particulièrement des infarctus par excès de sport chez les personnes âgées non entraînées). Mais l'analogie entre le souffle vital, la respira­tion et la vie, est connue depuis toujours. La simple promenade est déjà un fait important et les trajets sont utiles à analyser: ils mettent en évidence que l ' homme navigue a l'estime (les bateaux évidemment font de m ê m e ) ; la singalétique naturelle est essentielle autant que la perception des obstacles. L'analyse des trajets sur l'herbe est ainsi un des premiers enseignements qu'on peut en tirer en éco-éthologie urbaine. L ' h o m m e vit dans un espace topologique et non géométrique.

D e plus, cette pratique va amener une organisation des représentations de l'espace que nous verrons plus loin.

La relation parents/enfants

Elle est différente dans la nature et dans l'espace clos de l'appartement. C'est aussi là, que vont se créer les relations de groupes en équipes sportives (boules, basket, football, etc.) ou avec les pairs de l'enfant, en complément de l'école ou de l'entreprise ou des jeux plus intellectuels de la ville. Mais, certains jeux à l'inverse peuvent s'exercer dans la nature: jeux de cartes voire d'échecs. A Munich, il existe des tables d'échecs en béton dans les parcs urbains avec des pièces en bois utilisées par qui le désire.

L'éducation de la nature

C'est une autre fonction essentielle pour situer la nature par rapport à la ville. Actuelle­ment, on observe une idéologie manichéenne du type: «la ville est mauvaise (promiscuité, recherche de narcissisme), la nature est bonne». U n groupe de formation de G O sportifs du Club Méditerranée m ' a ainsi montré les limites de ce système et j'ai été amené à leur proposer de devenir des éducateurs de la nature car ils m'avaient appris que les G M ne supportaient pas de mettre le pied sur un oursin dans les lagons et qu'ils en rendaient responsables les organisateurs.

O n peut regretter que trop peu d'enseignants soient formés à ce rôle éducatif de la nature. D e plus, les gardiens des espaces verts, qui devraient aussi avoir ce rôle de forma­tion, ne le remplissent pas alors que cela les revaloriserait.

Quand on pense qu'on est obligé de faire des fermes expérimentales pour apprendre à de jeunes enfants que le lait n'est pas à l'origine dans du carton, mais dans le pis de la vache, et que les oeufs sont pondus para la poule, on s'interroge sur le type de connaissan­ces des enfants des villes.

Les parcs urbains devraient aussi être habités par des animaux à quatre pattes en plus des oiseaux: tels des cobayes, lapins, renards, etc., une sorte de micro-zoo chaque fois que cela est possible et dans des conditions aussi «naturelles» qu'il est souhaitable.

L'opposition ville-campagne se traduit par les migrations alternantes du week-end rui­neuses tant pour l'individu que pour la société. Réhabiliter les espaces verts urbains, c'est se donner le moyen de diminuer les migrations de week-end.

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Sur le plan cognitif, l'orientation para rapport au référentiel corporel va faciliter l'inté­gration de l'image du corps.

Chronobiologie

La relation avec les donneurs de temps naturel (température, soleil, saisons) aidera au «calage» chronobiologique des individus, dimension essentielle au maintien de la santé.

La nature c'est d'abord la vie et la mort. La sexualité est fortement liée aux espaces verts (comme le disent les chansons). L a rançon en est évidemment le nombre de voyeurs que l'on peut encontrer dans ces

espaces (c'est ainsi qu'au Parc de Saint Cloud, un de mes amis m ' a raconté qu'en se pro­menant avec une amie, à un endroit quelconque, s'il criait: «je t'ai vu», in entendait quel­qu'un détaler).

Le Bois de Boulogne à Paris est paradoxalement la plus grande maison close du monde . Le fonctionnement de nuit de cet espace est très différent de celui du jour.

Maladies mentales

Enfin, signalons une fonction assez spécifique des espaces verts péri-urbains: le camping pour petits groupes de malades mentaux qui se pratique dans les forêts d'Ile de France avec les malades de notre hôpital et quelques soignants. Il s'agit d'un m o d e de soins très particulier, extra-institutionnel, qui s'est toujours montré très efficace, en particulier pour les sujets très désadaptés par un trop long séjour hospitalier.

Localisation

La répartition des espaces verts intra-urbains est essentielle. Loring, aux Etats Unis, estime à 5 m n à pied le temps de parcours m a x i m u m pour que les gens utilisent les espaces verts. Leur taille conditionne aussi le type de fonctions possibles. L a stratégie de répartition des espaces verts dans la ville, selon leurs fonctions, devrait être un des axes de l'urbanisation. Les caractéristiques des espaces verts péri-urbains sont bien analysées par F . González-Bernáldez. L à encore, il faut affirmer que la ville ne peut être étudiée en soi en dehors de son environnement et que l'étude des villes doit se faire avec un «zoom» de taille variable, selon les variables examinées.

Espaces verts spécialisés

Le plus ancien est le cimetière. Beaucoup de cimetières sont utilisés c o m m e lieux de pro­menade. C'est aussi un lieu de rencontre des chats et des personnes qui les nourrissent, en plus de la méditation sur la mort ou de la rencontre avec les ancêtres.

L a fonction promenade dans les cimetières est très importante (toujours dans la rela­tion de la vie et de la mort) et incite à l'expansion des cimetières paysagers. Mais c o m m e les morts «sont beaucoup plus nombreux que les vivants» (Ionesco), il faut favoriser la crémation pour éviter leur extension indéfinie aux dépens des vivants.

U n autre espace vert utilisé (vert?) depuis longtemps quand il est péri-urbain est la plage.

Interface entre la côte et la mer, la plage a été le prétexte de nombreux aménagements et d'une urbanisation sauvage.

L'étude fait à Dunkerque para M . Poinsot, d'une plage spontanée, a bien mis en évi­dence que les gens utilisaient préférentiellement des espaces non aménagés, plutôt que la plage «légale» bien que celle-là se trouve en face d'une aciérie crachant de la fumée. Les idées repues en la matière sont probablement à réviser. C e que recherchent les gens, c'est

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finalement un espace non aménagé qui s'oppose à la ville. C e n'est pas le cas des villes côtières qui bénéficient du tourisme et où on finit par ne plus savoir où est la ville et où est la plage.

Mais dans tous les cas, les plantations, para exemple pour retenir les dunes, ou pour modifier le paysage, doivent être analysées aussi en fonction de leur rôle de limitation de l'ensoleillement et/ ou de l'isolement des individus les uns des autres.

Espaces privés et semi-publics

O n ne saurait non plus passer sous silence les espaces privés: les jardins qui attirent les gens dans les Villes Nouvelles (Saint Quentin en Yvelines: «la ville à la campagne» ou Melun Senart) et semi-privés ou semi-publics: jardins des administrations, des mairies, des servi­ces, des écoles, des hôpitaux, etc. Ils contribuent à l'identification des bâtiments par les gens, l'espace qui les entoure valorise leur image de marque mais aussi la construction. Tous ces espaces vont participer à la formation de la territorialité individuelle ou collec­tive.

Jadis, dans certains hôpitaux psychiatriques, les jardins étaient un alibi car les malades mentaux n'avaient pas les droit de les utiliser: ils servaient à cacher la misère des maladies mentales. C e véritable maquillage tend à disparaître.

Enfin, la production de biomasse dans les jardins privés n'est pas négligeable, m ê m e en Europe occidentale où elle donne de la valeur aux trois fruits que l'on ramasse. Elle a m é ­liore aussi le repeuplement d'oiseaux c o m m e l'ont bien montré les premiers, les Anglais dans leurs Villes Nouvelles. Cette production de biomase va aussi jouer un rôle majeur dans l'organisation du processus de territorialité.

Les monuments anciens ou modernes dans les espaces verts vont moduler cette relation entre la nature et la culture, en marquant toujours l'anthropisation de la nature par l'homme.

Les espaces spécialisés Les jardins botaniques, les zoos, les centres aérés, les piscines, les terrains d'aventure cons­tituent des espaces plus ou moins spécialisés avec une ou plusieurs fonctions prévalentes. Ils posent certains problèmes spécifiques sur lesquels nous n'avons pas le temps de nous étendre ici.

Les terrains vagues Para contre, les terrains vagues ont tous la m ê m e caractéristique: ce sont des trous dans le processus d'urbanisation plus ou moins provisoires ou plus ou moins définitifs.

C e provisoire qui dure devient un terrain de non droit «Res Nullius» c o m m e la mer. C o m m e tels, ils deviennent le support de rejets divers, de pollution, envahis qu'ils sont par des herbes sauvages.

Le plus souvent, défoncés, sales, ils détruisent l'image de la ville. Mais en m ê m e temps, ils sont le support des potentialités futures de celle-ci, que chacun voudrait squatter.

Les appétits des groupes de pression s'expriment sur ces zones, parfois semées de fri­ches industrielles et utilisées para des marginaux et les enfants, mais soumis aussi à une urbanisation sauvage.

O n peut limiter les dégâts en les transformant en terrains d'aventure pour les enfants.

Les petits aménagements des espaces verts non spécialisés Les chemins piétonniers, pistes cyclables ou pistes de patins à roulettes, terrains de foot­ball, terrains de boules, tennis, bancs, etc., ne doivent être utilisés que de manière limitée sous peine de transformer l'espace vert en espace urbain total. Il faut préférer les chaises mobiles aux sièges trop fixes pour permettre une animation avec choix du sujet dans l'orientation de son regard.

Les aménagements transitoires tels que théâtres, fêtes, foires, sont plus intéressants mais amènent déchets et dégradations. L a remise en état peut être coûteuse et leur multi-

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plication, destructive de l'espace jusqu'à ce que, c o m m e le fait toute institution, on finisse par faire une dalle de béton ou de goudron.

Les lieux de restauration doivent être minuscules par rapport à l'espace vert pour la m ê m e raison et de préférence périphériques par rappor à lui pour éviter une densification humaine centrale.

La surveillance sanitaire des espaces verts Le plus évident est que l'espace vert devient la cause de plus en plus nette de traumatismes divers et qu'il faut éviter les zones trop dangereuses que l'on repérera par les statistiques d'accidents qui s'y produisent.

Mais si les fractures, entorses et luxations sont importantes, du côté des utilisateurs, il faut aussi penser au manque d'entraînement sportif et prévenir les gens qu'ils doivent d'au­tant plus s'entraîner qu'ils font du sport plus rarement. O n peut essayer de promouvoir la gymnastique matinale pendant 15 m n à domicile.

Sur le plan infectieux, le tétanos a beaucoup diminué grâce à la vaccination mais le fumier est toujours porteur de germes.

Les bacs à sable des enfants contiennent de nombreux germes et surtout des champig­nons. U n e analyse régulière des bactéries et champignons des bacs à sable et des plages est aussi nécessaire que le dénombrage des colibacilles dans l'eau des mares (et aussi des levu­res, champignons, etc.). Les mycoses sont en effet fréquentes. Il est évident que les chiens ne doivent pas divaguer dans les bacs à sable des enfants.

Il ne faut pas oublier que les grands espaces verts c o m m e le Bois de Boulogne à Paris sont d'abord des aspirateurs de poussière avant d'être de fapon infime des producteurs d'oxygène.

Les déchets tels les boîtes de conserves vides doivent être éliminées: on sait bien qu'ils constituent le principal réservoir des larves de moustiques pouvant répandre le paludisme et que c'est, dans les zones dégradées, que va maintenant se réfugier le paludisme qui devient ainsi urbain c o m m e le montrent les parasitologistes de Montpellier.

Il faut soigneusement éliminer dès qu'il y en a un ou deux les déchets m ê m e discrets de papiers divers car le comportement grégaire du plublic va rapidement les multiplier en augmentant leur taille. Il faut aussi multiplier les actions pour obtenir des emballages biodégradables.

U n mal bénin peut être signalé: le rhume des foins et autres maladies allergiques liés au pollen des arbres et des fleurs à certaines saisons; ce n'est pas un risque bien grave mais on peut étudier les plantes les plus courantes à l'origine de ces allergies et tenter d'en diminuer le nombre.

Dans les terrains d'aventure, des accidents graves ont été observés parce qu'on était passé de la contrainte au laxisme. C'est toujours entre ces deux dangers que doit passer l'éducation de l'enfant.

Il n'y a pas que la santé de l ' homme et la Phytopathologie en partie lié aux pollutions doit être prise en compte pour éviter de trop fréquents changements de plantation. Le spectacle d'un espace vert mort va à rencontre de ce qui est recherché et n'est intéressant que c o m m e indicateur de la pollution qui atteint aussi les h o m m e s . A ce titre, on peut entretenir dans un petit espace spécifique des espèces sensibles à diverses pollutions pour indiquer aux h o m m e s que les seuils de pollution sont dangereux et qu'il faut les abaisser. C'est un moyen d'éducation intéressant.

L'attitude des populations vis-à-vis des arbres vieillis qui doivent être abattus et rem­placés montre à l'évidence que l ' homme urbain tend à perdre la notion du cycle normal de la vie et de mort.

T e m p s , espace et aspects symboliques

G . Ricou a proposé que l'on remplace les gazons par des pelouses plus faciles à entretenir et moins chères et que l'on plante aussi des arbres et arbustes portant des fruits pour éviter le côté gratuit purement visuel de la végétation afin de faire comprendre à l'enfant qui va

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manger en passant une cerise, que c'est un support productif utile qu'il faut respecter. L a meilleure preuve en est que les buissons de ronces porteurs de mûres de long des routes sont très peu dégradés.

L a culture d'une époque a toujours une relation avec la végétation. Les forêts en France se sont étendues et réduites en fonction de leur utilisation humaine.

Dans les villes modernes, on a fait des micro-espaces verts tellement petits et fragiles qu'il a fallu les hyperprotéger mais qu'ils ont du mal à résister aux pressions de l'environ­nement. Et pourtant, l'organisme que a construit le quartier de la Défense à Paris a décoré son espace de quelques pots de fleurs et d'arbres et a présenté un film sur le m o d e triom­phaliste: «Ils (les oiseaux) reviennent.» E n vérité, il faut bien les chercher dans le béton.

Les études faites par certains de nos étudiants sur la Place des Vosges, le jardin du Luxembourg à Paris, le Bois de Boulogne, montrent que c'est à partir des comportements non verbaux, des acteurs des différentes classes d'âge et de motivations diverses, qu'il faut aménager les espaces verts plutôt que de le faire a priori ou m ê m e que de demander aux gens leur avis.

L'étude des jeux de boules à Sarcelles, les circulations sur la place C a m b r o n n e mettent en évidence c o m m e n t les h o m m e s compensent ou non les erreurs d'aménagement.

Les dessing d'enfants sont une mine de renseignements sur la fapon dont ils voient leur ville avec les voitures que escaladent les immeubles alors qu'ils vont mettre des végétaux partout dans leur m o n d e car ils mélangent le dedans et le dehors.

Chez l'adulte, les cartes subjectives (mental maps) cosntituent l'outil de choix pour étudier les déplacements, les signaux repérables. Elles complètent les renseignements sur les communications non verbales et les comportements fournis para la vidéo.

Les plans d'eau, par exemple, constituent le signal le plus puissant dans ces repérages. A travers les représentations mentales des différents acteurs de la ville, utilisateurs de

l'espace vert, on peut analyser le langage c o m m u n et les conflits d'utilisation du temps et de l'espace dans ces lieux.

Les conflits normaux entre l'espace bâti/ non bâti, le temps contraint/ non contraint, les appétits des différents groupes méritent une analyse plus élaborée que ce qui est fait en général. Les résultats doivent être renvoyés à la population.

Tout ceci tourne autour des rapports Nature/Culture/Argent/Désirs. O n ne peut réduire sans caricaturer une telle complexité de motivations.

Certains ont proposé de choisir pour hauteur m a x i m a des immeubles celle du plus grand arbre de la région.

Cette relation inextricable entre la nature et l'action humaine se voit dans la plus banale fleur qu'on met dans un verre dans son appartement.

L'enchevêtrement hiérarchique entre la nature, la ville, l'appartement et l 'homme revient à la relation de la partie et du tout telle que D . Hofstadter l'envisage à partir du théorème de Gódel.

O n ne peut donner à l'un ou à l'autre la prééminence absolue. D'ailleurs, la qualité du paysage vu de la fenêtre va se traduire en termes bassement économiques para la valeur du m 2 de l'appartement.

Toutes les cultures ont organisé différemment la nature: jardin de l'Alhambra, Parc de Versailles, Ville d'Esté, Central Park, jardin japonais, etc.

Ainsi l 'homme est-il le centre de cette double tendance vers la nature et la culture qui a abouti à anthropiser de plus en plus la nature pour en venir maintenant à démécaniser et «renaturer» la ville (R. Klaine).

Mais il a gardé la crainte ancestrale des mythes de la nature et s'il ne se situe plus, en Europe occidentale, l'esprit de ses ancêtres dans les chênes, il garde une certaine peur des grandes forêts. O n sait que les gens demandent à habiter près des forêts mais que, seules les classes supérieures, vont au-delà de 500 mètres de leurs bordures.

Les autres restent au bord, pique-niquent le long des routes. O n saisit bien dans cette ambivalence, la vieille crainte du paysan qui avait peur d'une

nature mauvaise. Est-elle alors bonne ou mauvaise? C'est une question vaine. L a Nature est. L ' h o m m e en

construit toutes sortes de représentations et il a besoin, maintenant, pour sa santé physique

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(corps) et mentale (esprit) de rétablir cette liaison avec la nature que a eu tendance à se perdre au cours des derniers siècles.

Une tentative de réappropiation par l'image (images de la nature, corps bronzés, nudité, etc.), a échoué car elle n'était pas de l'ordre du faire mais du voir. C'était un spectacle.

C'est dans la mesure où la nature redeviendra un lieu pour le geste et l'action qu'elle reprendra sa valeur et que, simultanément, la santé de l'homme sera meilleure tout en lui rappelant sans cesse qu'il est fragile et mortel c o m m e elle.

B I B L I O G R A F Í A

L E R O Y , C : «Santé et identité». Colloque international Production et affirmation de l'iden­tité, Toulouse, 3-7 sept., 1979. Privat édit. (sous la direction de Pierre Tap), pages 301-304.

C H O M B A R T D E L A U W E , M . J.; B O N N I N , Ph.; M A Y E U R , M . , et coll.: «Enfant en-jeu». Rap­port Contrat de recherche pour la Caisse d'Alloc. Nov., 1974, 1 vol., 424 pages.

«Espaces d'enfants». Rapport Ministère Qualité de la Vie, Secrétariat Général Haut Comité de l'Environnement. Juin, 1976, 1 vol., 253 pages.

S I V A D O N , P. ; L E R O Y , C , et B E D O S , F . (avec la participation de plusieurs auteurs): Espace et comportement. Film 16 m m , couleur, son optique, 35'; réalisation Eric Duvivier; Co-production Labaz-Sciencefilm.

L A G R A N G E , Th. , et L E R O Y , C : «La représentation de l'espace: un indicateur d'évaluation de l'environnement». Symposium sur l'évaluation de l'environnement: Congrès A I P A , Munich, 1978, 30/7 - 5/8/78.

Groupe de travail: «L 'homme malade du temps». Rapport des Premières Rencontres Européennes du Cadre de Vie, Paris, 5-7 déc, 1977. U N E S C O , Ministère de la Culture et de l'Environnement: Résumés pages 2/19 - 2/21 et page 2/32, et Résumé in Rev. Jeunesse au Plein Air, janv. 78, n u m . 212, page 10.

L E R O Y , C : «A propos du parcours en forêt et des sentiers». Colloque international sur l'environnement forestier des grandes agglomérations, Versailles, 23-25 sept., 1974.

LORING, W . C : Actes du Congrès International Conference on Environmental Health, Primo'sten, Yougoslavie, 23-26 oct., 1973.

H I N K L E , L . E . , et L O R I N G , W . C : «The Effect of the Man-made Environment on Health Behavior». Publication D H E W , n u m . ( C D C ) 77-8318 - Report of the Inter-University Board of Collaborators U S P H S Contract C P E - R - 69 - 30 - U S Department of Health, Education and Welfare, Atlanta, Georgia 30333 (315 pages), 1977.

G O N Z Á L E Z B E R N Á L D E Z , F.: «Use of Environmental Perception in the Management of Marginal Land». Environmental Perception: Regional Seminar for Latin America and the Caribbean, pages 22-23. Montevideo (Uruguay), 23-27 avril, 1984. Edité par U N E S C O - M A B , 1985.

G O N Z Á L E Z B E R N Á L D E Z , F.: «The Use of Public Perception of Landscape in the Planning Process: The Spanish M A B experience». International Experts Meeting on Ecological Approaches to Urban Planning, Suzdal, 24-30 sept., 1984. Progr. M A B - U N E S C O .

P O I N S O T , Ch. : «Perspectives de l'écologie humaine dans une politique de l'environnement littoral: l'exemple de la région dunkerquoise». Metropolis, pages 66-69.

L E R O Y , C : «Les communications dans le processus d'organisation de la territorialité». Santé Mentale, num. 1, pages 3-7, 1981.

L E R O Y , C : «Psychopathologie liée aux milieux urbains». Encyclopédie médico-chirurgicale. Traité de Psychiatrie «Psychiatrie et environnment», fascicules 37881, A 10, 10, 1981.

H O F S T A D T E R , D . R . : G'ôdel, Escher, Bach. Vintage Books, 1980. Basic Books, N e w York, 777 pages.

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K L A I N E , R . : «Rénaturer et réenchanter la ville (les fondements biologiques et culturels du besoin de nature en milieu urbain)». Inst. Européen d'écologie. Rapport de contrat pour la Mission des Etudes et de la Recherche du Ministère de l'Environnement, juillet, 1981.

B A L L I O N , R . : «Relation entre statut socio-culturel et fréquentation de la forêt». Rapport Laboratoire d'Econométrie, déc, 1973, n u m . A 102 - 1273.

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AREAS VERDES EN UNA CIUDAD EN EXPLOSION: EL CASO DE LA CIUDAD DE MEXICO

Griselda Benitez Badillo Instituto de Ecología

Introducción

La ciudad de México se encuentra localizada en la parte baja de lo que fue una cuenca hidrográfica endorreica, mejor conocida c o m o el Valle de México. Esta cuenca, debido a diversas obras de ingeniería realizadas en distintas épocas, es ahora una cuenca drenada. Está situada en la porción central del país. Su altitud fluctúa alrededor de los 2.230 m sobre el nivel del mar.

Problemas de la Ciudad de México

Desde sus orígenes, la Ciudad de México ha experimentado una continua expansión y ha sido el primer centro económico, político y cultural del país. La Ciudad de México se construyó sobre las ruinas de la Gran Tenochtitlán, capital del pueblo azteca; ejerció igual función para la Nueva España durante la colonia y ha sido la capital de México desde su independencia política. Sin embargo, no es sino hasta ya avanzado este siglo, a partir de 1940, al cobrar auge el proceso de industrialización, cuando se configura y acelera la expansión metropolitana. Por un lado, el elevado crecimiento de la población de las ciu­dades y regiones de mayor desarrollo, a través de las consiguientes migraciones del campo y de la propia natalidad de sus habitantes. C o m o dato ilustrativo tenemos que entre 1950 y 1970 la migración interna en el país ascendió a 4,5 millones de habitantes y que en 1974, de cada cien personas que incrementaron la población rural, cincuenta y siete emigraron a la Ciudad.

E n la actualidad, con 18 millones de habitantes, es el asentamiento humano más grande que jamás haya existido; en sólo cuarenta y cinco años su crecimiento ha sobrepasado al de todas las grandes ciudades. Se extiende en una superficie promedio de mil kilómetros cuadrados.

Vivienda

Entre los problemas más agudos están el de la vivienda, que por su magnitud y naturaleza prioritaria desplaza al de las áreas verdes. Se calcula que existió un déficit de más de 800.000 viviendas en el período 1978 a 1982 y, en la actualidad, es de un millón, sin considerar las pérdidas provocadas por el seísmo, que ascienden a 30.000 viviendas perdi­das y 60.000 dañadas ( C E P A L , 1985); en 1970, el 30 por 100 de las viviendas censadas contaba únicamente con un cuarto y daba alojamiento al 27 por 100 de la población. E n promedio, cada cuarto alojaba 5,2 personas. Tan sólo las 800.000 unidades demandarían una superficie de 3.420 ha.

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Contaminación

E n la década de los sesenta, la Ciudad de México era considerada como una de las urbes m á s contaminadas del planeta. Contaminación generada tanto por la alta densidad d e m o ­gráfica c o m o por la elevada concentración industrial; la situación es agravada por la situa­ción geográfica, pues al estar rodeada por montañas y debido a su altitud, se dificulta el drenaje atmosférico. Las fuentes contaminantes principales son, en orden de importancia: los cerca de tres millones de vehículos que circulan diariamente (y que aumentan a una tasa del 12 por 100 anual), las 130.000 industrias y las tolvaneras que año a año se presen­tan durante el invierno y la primavera. Los datos existentes para 1981 muestran que las emisiones industriales alcanzan la cifra de 966.000 toneladas.

E n las regiones norte y noroeste se ubica la mayor concentración fabril, constituida por productores de plásticos, insecticidas, solventes, fertilizantes, termoeléctricas, huleras, etc.; de entre ellas hay que destacar a la refinería Dieciocho de Marzo ( P E M E X ) , en Azcapo-zalco; además de su importante contribución en volumen a la contaminación atmosférica, su ubicación provoca la amplificación del problema, pues los vientos se encargan de trans­portarla hacia el interior de la ciudad, afectando incluso la parte sur. Las fuentes de polvo provienen principalmente de la zona este (el ex lago de Texcoco). E n la zona centro es donde circula el mayor número de vehículos diariamente.

Ambiente

El crecimiento demográfico ha causado constantes modificaciones en el medio. H o y día tenemos que las superficies agrícolas prácticamente han desaparecido; el 71 por 100 de los suelos está degradado, el 73 por 100 de sus bosques se ha perdido y el 99 por 100 de sus lagos se ha desecado (Duayhe y García, 1982). E n consecuencia, las áreas verdes en la Ciudad han reducido su extensión; asimismo, se ha ocasionado la extinción de flora y fauna, una alarmante erosión del suelo, la escasez de recursos naturales, problemas de salud y pérdida de valores estéticos. La magnitud y diversidad de los problemas en la Ciudad de México en lo referente a la dotación de servicios públicos tales como vivienda, transporte, recogida de basura, suministro de agua, electricidad y alimentos, han adquirido proporciones tales que la creación y manejo de áreas verdes es relegada a un segundo término. N o siempre se reflexiona sobre las consecuencias que trae consigo el deterioro creciente de la vegetación. El mayor riesgo consiste en colocarse por encima de los límites de seguridad aceptables para la vida humana.

Areas verdes: antecedentes históricos

La afición por coleccionar vegetales y formar jardines con ellos fue un rasgo característico de los antiguos mexicanos. Durante la época prehispánica se practicó activamente el cul­tivo de jardines. E n la colonia, los jardines públicos se ubicaron hacia la periferia de las ciudades, ya que las plazas principales se mantenían libres de vegetación por la costumbre del saludo militar diario. E n la época independiente se vislumbraba la problemática que establecía la gran escasez de áreas verdes en la Ciudad de México, que no alcanzaban a cubrir ni el 2 por 100 de lo urbanizado. Se inició en 1901 una campaña tendente a incre­mentar la extensión de las áreas verdes; sin embargo, no se puso particular empeño en lograr este objetivo. El ayuntamiento argumentaba que resultaba m u y costoso crear y mantener tantos jardines como se necesitaban (Quevedo, 1942).

Cantidad de áreas verdes en la Ciudad de México

Existen varios trabajos que cuantifican la extensión de las áreas verdes en la Ciudad de México, pero muestran discrepancias que hacen difícil dar una cifra exacta.

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En la actualidad, las normas internacionales sugieren que debe haber un promedio de 9 m2/habitante; la Ciudad de México, según la estimación de Calvillo Ortega (1976), que es en general la más aceptada, cuenta con tan sólo 2,4 m2/habitante. Además de esta defi­ciencia en áreas verdes por habitante, su distribución no es uniforme en el territorio urbano, sino que hay zonas extensas en las que se acumulan, mientras que en otras faltan por completo.

Para claridad de la exposición se dividió el territorio de la Ciudad de México en tres porciones: norte, centro y sur.

L a zona norte presenta grandes zonas deforestadas y la carencia casi total de zonas verdes; el caso extremo es el de la Delegación Azcapozalco, que apenas alcanza 0,24 m2/habitante. Esta zona es marcadamente árida y los niveles que alcanza la contaminación atmosférica (los más altos del Distrito Federal) hacen que el ambiente sea hostil, situación que se agrava por la falta de vegetación.

La zona centro: en ella hay escasez de áreas verdes, sobre todo en las delegaciones Iztacalco e Iztapalapa, comprendidas en el grupo que cuenta con apenas 0,27 m2/habitante de promedio. También se ha deforestado gran parte de las arboledas que existen a los lados de las avenidas.

La zona sur establece el contacto más marcado entre la mancha urbana y el medio rural. H a sufrido la pérdida de extensas áreas verdes, sobre todo en las últimas dos déca­das, aunque es la zona que cuenta con la mayor superficie de áreas verdes.

Las áreas verdes más importantes en el interior de la Ciudad de México

Son pocas las áreas verdes más importantes de la Ciudad de México, atendiendo a su extensión y a la cantidad de visitantes que reciben; entre ellas se pueden citar el bosque de Chapultepec, el bosque de Tlalpan, el bosque de San Juan de Aragón y la Alameda Central.

El jardín más importante de la actual Ciudad de México es el bosque de Chapultepec (Cerro del Chapulín). Es el sitio de recreo más socorrido para los habitantes de la Ciudad (lo visitan alrededor de 1.500.000 personas cada fin de semana), y a la vez es el área verde más extensa (ocupa 643 ha) que existe en el interior de la urbe. Además de ser uno de los sitios de mayor arraigo tradicional entre los habitantes de la Ciudad.

El bosque de Tlalpan es la segunda área dentro de la Ciudad de México. Tiene una extensión aproximada de 304 ha, de las cuales 179 están abiertas al público, 80 son de reserva para el desarrollo del propio parque y 45 se entregaron en concesión al parque privado de diversiones Reino Aventura, que cubrió con asfalto varias hectáreas de encina­res del Pedregal de San Angel. La vegetación predominante en este parque es de comuni­dades naturales, además de especies introducidas.

El bosque de San Juan de Aragón cuenta con 275 ha y comprende un lago artificial (el más grande de la metrópoli) y un parque zoológico. Es producto de la reforestación, prin­cipalmente con Eucaliptus spp.

Bosques y viveros

Al igual que con los parques y jardines, su distribución dentro del territorio urbano es m u y heterogénea.

Para la protección de la flora y de la fauna se establecieron ocho parques nacionales entre 1936 y 1939.

Desde su creación todos han tenido escaso mantenimiento y conservación, sin que se hayan respetado sus finalidades ni su superficie. Ejemplo de ello son los lugares de Lomas de Padierna, Molinos de Belén e Histórico de Coyoacán, que han sido urbanizados en su totalidad; en el Parque Miguel Hidalgo se construyó el Centro de Energía Nuclear Salazar. Además, las actividades turísticas y la mala administración han ocasionado la degradación de estas zonas.

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C o m o ejemplo del manejo que se hace en un parque nacional mostraremos lo que sucede en el Cerro de la Estrella. D e 1.100 ha con que fue decretado, sólo 100 se adminis­tran con fines recreativos; de las mil restantes, aproximadamente el 60 por 100 es ya zona urbana, mientras que el 40 por 100 restante es terreno agrícola.

A pesar de la reforestación, el índice de supervivencia es m u y bajo, ya que de cada cien árboles que se plantan sólo cinco sobreviven, debido principalmente a la falta de agua, a la pobreza del suelo y a las quemas con objeto de labores agrícolas; se calcula que, debido al crecimiento de la Ciudad, es m u y factible que dentro de diez años desaparezca.

Los lotes baldíos de la Ciudad pueden tener importancia como áreas verdes. D e acuerdo con Rapoport et fl/.(1984), en ellos crecen algunas gramíneas y latifoliadas, que no sólo benefician estéticamente sino que también proveen de una cubierta verde que, entre alguna de sus funciones, protege de la erosión, por lo que disminuye la cantidad de agua en la Ciudad. E n este caso la situación del oeste de la Ciudad es interesante, en donde, de acuerdo con Villalobos (1981), se podría pugnar por abrir los lotes baldíos al uso comuni­tario c o m o áreas verdes, pues es altamente contradictorio que mientras la superficie ocu­pada por las áreas verdes es del 4,8 por 100 del área urbana, los lotes baldíos sumen el 6,6 por 100. El caso extremo de esta situación es la delegación Gustavo A . Madero, que cuenta con tan sóolo el 0,3 por 100 del territorio con parques y jardines, mientras que los terrenos baldíos ocupan el 22,7 por 100. Además de los baldíos hay que agregar la contri­bución de los jardines privados que, aunque no se han cuantificado, cubren una impor­tante superficie. Estos jardines contribuyen a mejorar las condiciones generales del ambiente de la Ciudad, aunque su accesibilidad para brindar recreación y esparcimiento es m u y limitada.

Además de las escasas áreas verdes en la zona metropolitana y de su mala distribución, una extensión considerable de ellas no cumple realmente con funciones de espacios útiles y recreativos. Por ejemplo, el 60 por 100 del área boscosa se encuentra localizada en el Desierto de los Leones, el cual es utilizado en ciertos días por la población que cuenta con vehículo particular. E n relación con las áreas verdes del interior de la Ciudad, el 65 por 100 está en camellones, glorietas y tréboles de tráfico, que las hacen virtualmente inutili-zables para fines recreativos, lo que ocasiona que disminuya su eficiencia c o m o área de recreación (Halffter et al, 1977). Es importante señalar, con relación a su distribución, que para el grueso de la población implica grandes desplazamientos y tiempo de recorrido, lo que viene en deterioro de su persona.

Vegetación natural

La Ciudad de México se encuentra en una zona privilegiada desde el punto de vista ecoló­gico, pues su posición geográfica, su altitud y su topografía se combinan para producir un rico mosaico de condiciones ambientales que da cabida a una m u y variada flora. Se la considera c o m o una de las regiones más ricas del m u n d o en cuanto al número de las especies vegetales que posee; tan sólo de plantas fanerógamas se calcula que existen apro­ximadamente dos mil especies, y en general posee una diversa conformación de comunida­des vegetales, entre las que se cuentan bosques de coniferas y encinas, matorrales xerófilos, pastizales, vegetación halófila, vegetación acuática y malezas.

U n ejemplo de la pérdida de la cubierta vegetal es lo que ha ocurrido en el sur de la Ciudad de México; Benítez et al señalan que la mancha urbana se extendió casi un 500 por 100 entre los años 1959 y 1977, cubriendo matorrales xerófilos de palo loco (Senecio praecox), bosques de encina y las extensiones agrícolas colindantes. Sin embargo, estas últimas, a pesar de haberse estrechado originalmente por la urbanización, han aumentado de superficie al demontarse los bosques de pino y oyamel. Los pastizales originados por el disturbio son la única comunidad natural que ha ganado terreno al ocupar sitios agrícolas abandonados o los espacios que dejan los bosques destruidos por la tala, los incendios, el sobrepastoreo y las plagas.

Cada día, el habitante de la Ciudad de México encuentra regiones naturales que han cedido su lugar a un fraccionamiento, a una zona industrial o a la erosión. L a pérdida o

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alteración de los habitats necesarios para el desarrollo de los organismos trae c o m o conse­cuencia su extinción. Rzedowski (1979) da una lista de más de 150 especies que han des­aparecido o que están amenazadas de serlo.

Las actividades de reforestación en general se han efectuado con especies introducidas que tienen c o m o característica un rápido crecimiento.

La reforestación ha sido hasta ahora un plan de producción sin una optimización del mismo en cuanto a especies residentes. C o m o ejemplo de esto tenemos que en 1985 se plantaron 30.000 árboles en el bosque de Chapultepec, que fueron destruidos casi en su totalidad.

Areas agrícolas

El proceso de expansión urbana ha crecido fundamentalmente en detrimento de las zonas de cultivo, principalmente hacia el norte y, en la actualidad, hacia el sur de la cuenca, sobre terrenos planos, de buen drenaje y con abastecimiento de agua. La explicación de esto radica, c o m o lo indican Halffter et al. (1977), en que: «El criterio que ha prevalecido en este hecho es el de que una hectárea de área urbana vale más que una hectárea de maíz o de alfalfa».

La expansión urbana cubre las zonas agrícolas y al mismo tiempo se abren nuevas tierras al cultivo en terrenos generalmente impropios, c o m o son las laderas de los cerros (Benítez el al, en prensa).

Es importante señalar que, además de perderse vastas extensiones de terrenos agrícolas, también se está perdiendo la tecnología tradicional del cultivo de «chinampas», de origen prehispánico, que tal vez sea el más importante legado de la cultura lacustre de nuestros antepasados.

E n la actualidad, en lugar de aumentar, disminuye la extensión de las áreas verdes por diferentes circunstancias, c o m o la remodelación de la Ciudad. U n ejemplo de ello es la construcción de los ejes viales en 1983, destinada a mejorar la circulación de los vehículos; además de la disminución de las áreas verdes, se afectaron 7.166 viviendas, con lo cual la demanda de áreas para casa habitación se incrementó. N o puede dejar de señalarse que hubo políticas para evitar su pérdida, c o m o lo fue el establecimiento de áreas con jardín en las banquetas con una extensión de un tercio del ancho total de las mismas. Esto se llevó a cabo cuando la zona de peatones tenía un ancho de 1,6 m . E n caso contrario se redujo el ancho del área con jardín y se procuró conservar como dimensión mínima 0,30 m . Además , se propuso el traslado de los árboles de las zonas afectadas, en la mayoría de los casos sin éxito. La sustitución de diversas glorietas y numerosos camellones, y con ello viejos árbo­les y motivos ornamentales, por asfalto con setos y muebles urbanos uniformes con arboli-llos, realmente no compensan los árboles centenarios de grandes copas removidos en la mayoría de las nuevas vías. A esto habría que agregar que en la mayor parte de estas zonas hay un mantenimiento escaso.

Otro ejemplo del poco interés que existe por las áreas verdes es la tala de aproximada­mente 350 árboles en la ampliación de 5 k m de asfalto del velódromo Ricardo Rodríguez en la Ciudad Deportiva, llevada a cabo en diciembre de 1985 c o m o preparativo para el gran premio Fórmula I en México. U n efecto similar tuvieron las obras de acondiciona­miento urbano para el Mundial de Fútbol 1986. E n la Calzada de Tlalpan se han derri­bado varios centenares de árboles corpulentos con el objeto de alojar un «tren ligero».

Conclusiones

La falta de zonificación y a veces de reglamentación para controlar la acción de las c o m ­pañías urbanizadoras, las que especulan con el suelo urbano, además de la ausencia de programas en las obras públicas, han devenido en un uso irracional del suelo en las diver­sas partes que integran la Ciudad de México. Nos encontramos con que se mezclan áreas de habitación con áreas industriales, comerciales o de oficinas, combinadas a veces caóti-

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camente; además de una distribución poco uniforme, se da el caso de que amplias zonas habitacionales no cuentan con equipo y servicios adecuados y mucho menos con áreas verdes y de recreo, en tanto que otras están m u y sobradas de estos elementos. E n relación con la vivienda, el suelo ha sido condicionado por los intereses especulativos y por la composición socioeconómica de la población.

Cabe destacar que se han promulgado leyes destinadas a promover la conservación del ambiente en la Ciudad de México, entre ellas, la creación de parques nacionales c o m o áreas protegidas, el primero de ellos en 1917.

Asimismo, existen leyes relativas al control de la contaminación ambiental, tales c o m o la Ley Federal para Prevenir y Controlar la Contaminación Ambiental, promulgada en 1971.

E n 1979 se decretó que por arriba de la cota de los 2.350 m s n m no se permitiría la construcción en las sierras del suroeste de la Ciudad de México; dicha disposición no ha sido respetada, incluso por las mismas autoridades. Ejemplo de esto es la construcción del Nuevo Colegio Militar (Ecoplan del D . F.).

E n relación con los fraccionamientos, en diversas ocasiones se ha señalado en los dia­rios que no se permitirá uno más; sin embargo, los fuertes intereses económicos hacen que en la práctica no se trate del otorgamiento de «permisos» o la aplicación de «programas de desarrollo urbano», sino que se tienen que resolver los problemas planteados por hechos consumados ante los que las autoridades no pueden ejercer ninguna medida efectiva.

E n los últimos años se elaboró el Plan de Desarrollo Urbano del Distrito Federal. Entre las políticas generales está la de la conservación, que exige:

1. Preservar y aprovechar los espacios abiertos de uso público de nivel urbano y metropolitano en el Distrito Federal.

2. Preservar y reforestar los bosques del Distrito Federal. 3. Mantener y aprovechar las áreas para explotación agropecuaria intensiva. 4. Establecer y mantener una zona de transición entre el área susceptible de desarrollo

urbano y las zonas no urbanas del Distrito Federal. Después de los seísmos de septiembre de 1985, las autoridades determinaron que se

dedicaran los espacios dejados por los edificios caídos a jardines de uso público. Sin embargo, esta disposición no se llevó a la práctica completamente, pues establecía una contradicción con el elevado déficit de vivienda que padece la Ciudad.

D e seguir las tendencias que han definido la problemática de la zona metropolitana de la Ciudad de México, se tendrían resultados c o m o los siguientes para el año 2000:

1. El número de habitantes ascenderá a 36 millones. 2. La expansión de la mancha urbana llegará a 2.800 k m 2 , con una densidad de 127

hab/ha. C o n base en lo expuesto, se infiere que para el año 2000 se tendrá el equivalente a otra

ciudad de la misma extensión que la actual. Halfter et al. (1977) también señalan que la mayoría de los problemas ecológicos pro­

vocados por el explosivo crecimiento urbano no requiere un estudio ecológico especial, sino una solución política.

U n a de las medidas m á s importantes es la educación del público, que, al igual que en otras áreas de la conservación, es uno de los elementos más importantes y seguros en las estrategias para garantizar el mantenimiento de los recursos, sobre todo si ésta va unida a decisiones políticas que fomenten eficazmente la descentralización y planteamiento.

N o debe sorprender el panorama presente de las áreas verdes de la Ciudad de México, ya que se trata de un problema que hunde sus raíces en una larga historia de descuidos y esfuerzos no continuados. Y todo ello, a pesar de que desde hace mucho tiempo se tienen identificados los problemas que puede acarrear su deficiencia y se conocen las condiciones mínimas en que deben encontrarse en las ciudades.

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CONCLUSIONES

U n a vez finalizadas las exposiciones de las ponencias y de sus coloquios respectivos, se constituyeron tres grupos de trabajo: grupo de investigación (coordinado por John Celecia y Antonio López Lillo), grupo de planificación y gestión (coordinado por Pedro Salvador) y grupo de formación, información y sensibilización del público (coordinado por George Barker). Su labor sería la de estructurar las necesarias sugerencias y recomendaciones de proyección futura para el uso, tratamiento y gestión del verde urbano.

Grupo de trabajo de investigación

Dentro de lo que pueden ser recomendaciones y apertura de líneas de investigación para cubrir las necesidades de uso, tratamiento y gestión del verde urbano, habría dos grandes grupos o campos de interés interdependientes: el ecológico y el humano .

Procedimientos — Establecer el estudio sistemático, comparativo y periódico de los factores ecológi­

cos, en áreas diferenciadas de la ciudad, con vistas a la utilización de las especies vegetales más aptas a las condiciones ecológicas determinadas por el medio a m ­biente urbano.

— Estudio de los factores limitativos (bióticos, abióticos y antropogénicos) y selección de las spp mediante métodos cuantitativos de simulación que sean transferibles a los diferentes ambientes adversos en la ciudad.

— Estudio de la optimización de los tratamientos adecuados para el buen desarrollo de las comunidades vegetales en el medio urbano.

Resultados esperados a) Banco de datos sobre el ambiente urbano y sobre las especies vegetales susceptibles

de ser utilizadas. b) Elaboración de un modelo operativo para seleccionar especies adecuadas a condi­

ciones ambientales concretas. c) Producción de documentos y /o manuales o programas con líneas y recomendacio­

nes de uso para proyectistas y planificadores de áreas verdes urbanas. d) Seguimiento de las tendencias ecológicas de las áreas verdes urbanas para pronos­

ticar el proceso y elaborar alternativas y, donde corresponda, el uso de bioindicadores. e) Producción de documentos que permitan a los gestores realizar adecuadamente

una selvicultura urbana.

Recomendaciones — Hay que utilizar árboles ecológicamente correspondientes a la exigencia microcli-

mática especial de las ciudades respectivas en su reforestación. — Hay que priorizar la utilización de los árboles y arbustos de la flora nativa de cada

región, para tener poblaciones más resistentes a las plagas y a las condiciones ur­banas.

— Hay que seleccionar poblaciones de las especies nativas de las regiones ecológica­mente más afines a las condiciones especiales de cada ciudad.

— Investigaciones para desarrollar programas de selección y manejo de bioindicadores (vegetales y animales) y metodología correspondientes a las distintas zonas climáti­cas y edafológicas en el área urbana.

— Investigaciones sobre la relación entre el espacio verde urbano, su extensión y dis-

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tribución y el clima urbano a diferentes escalas (macro-meso-micro) orientado a disminuir el impacto de condiciones extremas y para optimizar el flujo de energía y del agua

— Investigación sobre el uso del espacio construido (estructuras construidas) c o m o espacios verdes en áreas urbanas densas.

— El potencial de espacios verdes en techos y balcones, pasajes sobre calles urbanas, de paredes y otras estructuras está bien reconocido.

— La base y asesoramiento técnicos para desarrollar un programa de reverdecimiento urbano dependerá de una investigación práctica sobre las influencias ecológicas y microclimáticas que distintos tipos de construcción tengan sobre el crecimiento ve­getal.

— Investigación para determinar la eficiencia y la ventaja en términos económicos de los espacios verdes sobre las estructuras diseñadas y construidas por el hombre en relación a diversas funciones, c o m o : captación de agua (la ciudad c o m o cuenca hidrográfica), conservación del suelo urbano, disminución y control de contamina­ción urbana y del suelo, prevención de catástrofes naturales (inundaciones, etc.).

— Investigación sobre los aspectos de plaguicidas sobre el medio urbano. — Investigación sobre programas de reciclaje de agua y desechos en el medio urbano

para manejo (gestión) de áreas verdes, incluyendo uso de aguas tratadas para rie­gos, elaboración de compost, mejora de las condiciones físicas y químicas del suelo urbano para su mayor productividad.

— Desarrollar unidades de conservación de la naturaleza en el medio urbano y pro­gramas de investigación para asegurar la supervivencia de poblaciones de plantas y animales por medio de un manejo integral de espacios verdes, su relación entre sí y con el entorno de la ciudad.

— Promover estudios fenológicos locales para completar observaciones de la red meteorológica y contribuir a establecer las bases para el diseño racional de zonas verdes. (Experimentar participación del público a través de grupos vecinales, clubes jardineros, proyectos estudiantiles de prácticas, etc.).

Dentro de este intento de abordar de una manera racional el «verde urbano», es necesa­rio contemplar c o m o parte fundamental al hombre, c o m o habitante y usuario de ese posi­ble espacio a construir y distribuir. Y m á s que nunca, desde un planteamiento interdisci-plinar que recoja los aspectos psicosociológicos que conforman al individuo, ya que éste no es un sujeto aislado, sino que vive inmerso en un sistema cultural que determina accio­nes, necesidades, significados.

L a investigación de modelos de percepción y su relación con el comportamiento indivi­dual y social respecto del medio ambiente, es un campo de interés científico nuevo que, por su valor integrator y selectivo nos puede permitir, aplicando las metodologías apropiadas, adaptadas a las características locales, captar las valoraciones y conflictos de los distintos sectores de la población y atender a sus necesidades. Para ello sería útil ahondar en las motivaciones que han producido resultados, ya obtenidos en investigaciones anteriores, tales c o m o la constatación del papel positivo que juegan las zonas verdes en la forma en que los individuos y grupos utilizan su tiempo libre, en las expectativas de reposo, des­canso y la función de estos espacios en la salud física y mental, de tal forma que se obten­gan orientaciones para su diseño y enfoque global de cara a planificadores con posibilidad de llegar a establecer leyes, estadísticas, corregir disfuncionalidades (aislamiento), construir mapas mentales y elaborar propuestas en el sector servicios.

Grupo de trabajo sobre planificación y gestión

1. Parece necesario, por claridad metodológica, llegar a homogeneizar una descrip­ción conceptual sistemática de los distintos elementos tipológicos de los espacios verdes de una ciudad; en todo caso, la aspiración debe ser la elaboración de una trama integrada y conexa de áreas verdes.

2. Se debería exigir la intervención, en los equipos planificadores y proyectistas de las

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ciudades, de los responsables de la gestión y uso de los jardines, teniendo en cuenta no sólo los conceptos urbanísticos y artísticos, sino su integración en el medio y las necesidades del hombre, resaltando el carácter interdisciplinario y la utilización de criterios ecológicos en la planificación.

3. Es importante tratar de acercarse a la valoración (incluso económica) de los bene­ficios de una zona verde para la calidad de vida de la población. Estos beneficios (ventaja climática que ahorra energía de calefacción o refrigeración, ventaja social del grado de ocupación y uso de los jardines) pueden ser de ciclo largo, pero aprehensibles. Conviene incidir en aspectos de biotecnología.

4. A la hora de juzgar un proyecto, sería exigible mayor rigor en la justificación del diseño y de los objetivos y beneficios para la población, ello a través de un mejor control profesional y de una honda justificación del empleo de fondos públicos, buscando una coordinación entre investigación y planificación y estableciendo programas ocupacionales de la población.

5. Deberá regularse por ley el empleo de las zonas libres de la ciudad sin ocupación, mediante una legislación actualizada que asegure el futuro, eliminando la especulación. Por ejemplo, uno de los instrumentos serían los Planes Generales de Ordenación.

6. Igualmente, las administraciones locales deberán regular los espacios verdes pri­vados que tengan una incidencia o repercusión sobre el resto de la ciudad, su paisaje o su medio, y establecer acuerdos con los propietarios para facilitar su conservación y favorecer su conocimiento por el público.

7. Se deberían suprimir del recuento de superficies verdes los espacios públicos que tienen sólo un carácter de área verde óptica, no pisables y, por tanto, de poco interés y provecho real.

8. Debería recomendarse el esfuerzo conjunto de los países del Mediterráneo para profundizar en el estudio de una jardinería mediterránea con soluciones actuales a los problemas y situaciones de partida de la región.

9. Es importante que se establezcan, en los países donde no existan, los estudios formales de paisajismo, a fin de que se proyecte y gestione desde una plataforma de cono­cimiento especializada.

10. El espacio verde urbano deberá tender a la consecución conjunta de la función y la belleza, inseparables.

Deberán expresarse los datos y resultados de uso de los jardines no c o m o manteni­miento, sino c o m o gestión, que es un concepto más amplio, integral y activo.

Grupo de trabajo sobre la formación e información

L a interdependencia de la ciudad y su entorno no solamente presenta un aspecto econó­mico, sino que tiene necesidades sociales entre la ciudad y los habitantes rurales. Forman parte de un sistema continuo. Se plantea un gran inconveniente al considerar la ciudad de forma aislada, y es contraproducente.

— Expresamos que se presta una atención insuficiente a la influencia de las alteracio­nes del medio ambiente sobre los modelos de comportamiento social. Cualquier influencia de la gente sobre el medio natural nos conviene a todos y nos lleva a que los expertos evalúen los efectos de los demás al medio.

Existe una gran separación entre los aspectos tecnológicos y artísticos de la educación. Se da gran énfasis a los logros tecnológicos y se minimizan los aspectos artísticos. Es necesario lograr un «hombre completo» al educar a los jóvenes para imbuir una gran sensibilidad por el medio.

— Recomendamos que expertos y prácticos en educación pasen revista a los sistemas de enseñanza para equilibrar la balanza.

Es esencial seguir los cambios logrados por los programas de educación ambiental. Esto se debe aplicar a todos los programas y no solamente dentro de la escuela. Es necesa­rio evaluar la efectividad de los resultados con los logros realizados. Desgraciadamente no siempre los responsables de los programas de educación tiene claras las metas a conseguir.

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— R e c o m e n d a m o s que los resultados del seguimiento de estudios se revisen y sirvan de guía a los educadores para cumplir sus objetivos y poder adecuar satisfactoriamente sus programas.

Parece que el insuficiente conocimiento de opciones por parte de los tomadores de decisión y de los planificadores del territorio es un factor importante para la conservación de las áreas verdes, así c o m o en su ordenación y planificación. Es necesario que ecologistas y ordenadores del territorio colaboren para establecer todas las opciones que puedan informar y guiar a los tomadores de decisión para elegir las soluciones adecuadas a las necesidades de la comunidad, de acuerdo con las condiciones ambientales de la localidad, así c o m o de las exigencias de la economía local.

— R e c o m e n d a m o s la cooperación internacional para lograr lo expuesto, reconociendo la existencia de considerables diferencias medioambientales en las diversas áreas geográfi­cas, por lo que se podrían establecer subgrupos de colaboración regional m á s que de cooperación global.

E n muchas ciudades el espacio disponible para establecer zonas verdes es m u y limi­tado. Incluso el medio ambiente está m u y perturbado por la contaminación, lo que impide un normal desarrollo de la vegetación y, en particular, las verduras y árboles frutales. Para nosotros, los tejados de las casas pueden ser unos espacios aptos para establecer jardines. Existen muchos ejemplos en los que se han obtenido con gran éxito jardines sobre tejados. Actualmente, la tecnología permite extender estos ejemplares aislados a esquemas m á s generales. Junto al concepto jardines-tejado se puede generalizar el uso de edificios c o m o infraestructuras para establecer zonas verdes.

— R e c o m e n d a m o s establecer los pasos que revisen los ejemplos aconsejables y la lite­ratura técnica, así c o m o las informaciones relevantes que permitan conducir la imagina­ción de planificadores políticos y arquitectos paisajistas, así c o m o al público con el fin de que conozcan adecuadamente la vegetación conveniente. Sin prisas se debe investigar sobre la literatura similar, así c o m o publicar los sistemas existentes y extender las opciones mediante la conjugación de la tecnología moderna con los procesos naturales.

Es m á s fácil aprender mediante la experiencia personal. E n el c a m p o en el que la cooperación internacional es particularmente valiosa, urgimos que cada oportunidad sea estudiada y se establezcan intercambios a corto y medio plazo de expertos entre agencias y organizaciones ligadas con el medio ambiente. Esto se puede aplicar con eficacia entre diferentes organizaciones y departamentos de distintos países.

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INDICE

Composición del Comité Español del Programa M A B (El hombre y la biosfera) de la U N E S C O 4

Prólogo 5 Programa 7 Organización 8 Relación de participantes 9 Resumen 11

Ponencias Presentación general y objetivos del Seminario 19 National, regional and local planning strategies for urban green areas in the Nether­

lands. A n ecological approach 23 Problems and programmes concerning the use and the education about the urban

green areas. The case of R o m e 35 Areas verdes en las ciudades, el efecto de su contaminación, su monitoreo y bioin-

dicación. Estudio del caso de Budapest 41 Evaluating urban forest structure for modifying microclimate: the Dayton climate

project 49 Urban examples for basic services development in cities , 55 Design and creation of urban green spaces 71 La percepción del verde urbano y periurbano 73 La teoría de la información y la estética de las zonas verdes 77 Exploratory survey on the perception of vegetation in Säo Miguel, city of Säo

Paulo 81 The links between ecological science, local authority action and community invol­

vement in planning and land management for nature conservation in british cities 87

Rôle des espaces verts urbains et péri-urbains dans le maintien de la santé et de l'identité de l 'homme 93

Areas verdes en una ciudad en explosión: el caso de la ciudad de México . . . 101 Conclusiones 107