WETLANDS OF THE HUMID TROPICS - UNESCOunesdoc.unesco.org/images/0011/001160/116084Eo.pdfspectacular wetlands of the humid tropics include the vast river floodplains and deltas of the

WATER-RELATED ISSUES AND PROBLEMS OF THE HUMID TROPICS

AND OTHER WARM HUMID REGIONS

IHP HUMID TROPICS PROGRAMME SERIES No 12

WETLANDS OF THE HUMID TROPICS

INTERNATIONAL HYDROLOGICAL

“... by the Year 2000, almost one-third of humanity will be living in the tropics”

Tmpc 0, cancer _ _-.-.-.-. .-.-. -.- -.-

I!

__ -.- - .-.- - -.-. __ -.-.-.

10’

30 0 30

0 ---- Coldest isotherm months (18O)

so 90 120 150 .I&

World map showing distribution of the three climatic subtypes of the humid tropics: humid, .subhumid and wet-dr?:. Also shown is the dry tropicul region (Source: Bone11 et al.. 1993).

Christine Coughanowr

0 UNESCO 1998

Cover photo Kakadu Nattonal Park, Northern Terntory. Australia 0 Enwonment Australia.

Contents

1. Introduction .................................................... 1

2 Thevalueofwetlands ............................................ 8

3. Unique aspects of wetlands in the humid tropics ........................ 13

4. Causesandconsequencesofwetlandsloss ........................... 19

5. A framework for management ...................................... 28

6. Conclusions .................................................... 42

References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 45

Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 47


INTRODUCTION

The humid tropics

The humid tropics encircle the Earth’s equator and extend over two thousand kilometres to the north and to the south, roughly paralleling the Tropics of Capricorn and Cancer. This region contains approximately 20% of the world’s land area and is characterized by warm temperatures, abundant rainfall and extreme weather conditions, including cyclones and monsoons. Although the average annual rainfall is high in most tropical regions, often exceeding several metres per year, its distribution in time and space can be highly variable. Madagascar, for example, has an annual average rainfall of 2-4 metres along the east coast, whereas the west coast frequently receives less than one metre. The combination of temperature, humidity and weather patterns - together with the underlying geology - determine to a large degree the unique landscapes, soils and ecosystems which are found in tropical regions.

Wetland ecosystems are an important and widely distributed feature of tropical landscapes in both coastal and inland regions. Examples of some of the more spectacular wetlands of the humid tropics include the vast river floodplains and deltas of the Amazon, Niger, Ganges- Brahmaputra and Mekong rivers, the immense inland swamps of the Brazilian Pantanal, the Congo and Sumatra, and the impenetrable mangrove forests which border most low-energy tropical coastlines.

These wetlands perform a number of vital ecological functions by regulating streamflow and ground-water recharge, maintaining water quality, stabilizing shorelines and providing habitat for innumerable species of fish, birds and other animals.

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Rapid wban growth degrades wetlands in many tropical cities.

In many parts of the world, wetlands have historically been reviled as disease-ridden wastelands and actively drained or otherwise ‘reclaimed’. As the consequences of widespread reclamation have become apparent, however, in the form of contaminated water supplies, increased flooding and erosion and dwindling natural resources, a new attitude towards wetlands has emerged. Over the past few decades, wetlands have increasingly been valued for the ‘goods and services’ they provide to human populations, as well as for their intrinsic ecological value.

The countries located in the humid tropics are among the poorest on Earth; over two-thirds of the world’s poorest countries (average per capita GNP of less than $250) are situated in this region (World Bank, 1991). As is frequently the case in economically depressed regions, population growth rates tend to be high, often exceeding 2% or even 3% per year - for example in C&e d’lvoire (3.8%), Nicaragua (3.4%) and the Solomon Islands (3.3%) (World Resources Institute, 1992). It is estimated that, by the year 2000, approximately one-third of the Earth’s population will live in the humid tropics, with this proportion increasing to about 44% by the year 2025. The problems caused by rapid population growth and poverty are compounded by abrupt social, economic and political changes endemic to many developing countries. These factors typically result in increasing pressures on wetlands and other natural areas.


What is a wetland?

Wetlands occupy the transitional zone between land and water, often exhibiting characteristics of both aquatic and terrestrial ecosystems and, in coastal areas, those of both freshwater and marine ecosystems. As such, the adoption of a single, universally accepted definition of wetlands is problematic. However, most wetland definitions include three main components:

1. Wetlands are characterized by the presence of water, either permanently or periodically;

2. Wetlands have unique, waterlogged soils;

3. Wetlands support vegetation specifically adapted to wet conditions and lack flood-intolerant vegetation.

One broadly accepted international definition of wetlands is that adopted by the International Ramsar Convention, which defines wetlands as: ‘areas of marsh, fen, peat/and or water, whether natural or artificial, permanent or temporary, with water that is static or flowing, fresh, brackish or salt, including areas of marine water the depth of which at low tide does not exceed six metres:

WETLAND WATER

Hydrological Regime

Dry -

Biochemical Role . Source -

Net Primary Productivity

- Lowto medium -

HIGH WATER

Fluctuating water level 1 LOW WATER

. Intermittently __ to Permanently flooded

Permanently flooded

l Source, sink - and transformer I

XL:.. : . . ?.

- Generally high - I

- Generally flow

Wetlnnds occupy the transitional zone between land and water (after Mitsch & Gosselink, 1986; adapted by permissim of John Wilex & Sons).

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There have been a number of attempts to classify wetlands into categories that reflect their structural and functional characteristics. The primary goal of classification is to place boundaries on natural ecosystems for the purposes of inventory, evaluation and management. Wetland classification systems typically use some combination of vegetation type, plant or animal species, hydraulic conditions and substrate to group together ecosystems which have similar characteristics.

Freshwater or inland wetlands include standing or flowing fresh-water bodies (lakes, ponds, rivers and streams), marshes and bogs, and wooded swamps. Freshwater wetlands may be permanent or seasonal, associated with perennial water bodies, areas of ground- water discharge or periodically flooded lowlands.

Marine or brackish wetlands include estuaries, mangroves, seagrasses and mudflats. These wetland ecosystems are variously adapted to cope not only with saturated soils, but also with elevated salinities, fluctuating tides. waves and coastal currents.

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- Sudd

30

20

10

0

Comparison of monthly menn flooded areaS (in 000s km’)for,four major African wetlands (after Blrllock. 1993).

Wetland hydrology

The presence of water is the unifying factor behind all wetland ecosystems, providing the conditions under which unique soils, vegetation and fauna have developed. Energy and nutrients are transported to and from wetlands by precipitation, surface runoff, ground water, tides and flooding rivers. Water depth, flow patterns and the duration and frequency of flooding influence the biochemistry of the soils and are major factors in the ultimate selection of wetland biota. In fact, hydrology is probably the single most important determinant for the establishment and maintenance of specific types of wetlands and wetland processes (Mitsch & Gosselink, 1986).

Wetlands can be extremely sensitive to changes in hydrology; a slight change in hydrologic conditions may result in large changes in species richness and ecosystem productivity. Nonetheless, wetland plants and animals are not purely passive elements within the system: many wetland plants actively regulate hydrology through a range of mechanisms such as transpiration, water-shading, and sediment-trapping. In some cases, animals may also influence wetland hydrology. For example, in the Florida Everglades, alligators dig ‘gator holes’ - deep, perennially flooded depressions - which provide essential habitat for fish, turtles and other aquatic animals during the dry season. The relationship between wetland hydrology and biota may take centuries to establish and is an important consideration in efforts to replace existing wetlands with man-made equivalents.

10 , Senegal

Jan.


Wetland soils

Wetlands soils are water-saturated on a permanent or periodic basis. These waterlogged soils, also known as hydric soils, are typically low in oxygen or reduced, resulting in a number of characteristics including high organic content, mottled or gleyed colours and production of gasses such as hydrogen sulfide and methane.

Oxygen-poor soils limit plants’ ability to carry out normal aerobic root respiration and modify the availability of nutrients. They can also allow the concentrations of certain elements and compounds to reach toxic levels. To cope with these conditions, wetland plants and animals have developed a number of specific adaptations, as described below.

Wetland vegetation

Wetland plants are uniquely adapted to thrive under conditions of environmental stress which include waterlogged soils, floods interspersed with dry periods, extreme water temperatures and, in some cases, salt.

Plants have developed a number of structural and physiological adapt-ations to either tolerate or regulate these stresses. To avoid root anoxia, for example, many wetland plants have evolved air spaces in their stems and exposed roots, which allow for the diffusion of oxygen from the aerial portion of the plants. This results in the porous, honeycomb-type structure seen in many wetland plants, e.g. reeds. Woody tree species often produce adventitious roots above the anoxic zone, such as the prop roots and air roots characteristic of some mangroves. In salty environments, plants may be adapted to either limit the entry of salt or to actually excrete it, using specialized cells.

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Latin American caiman are entirely dependent on wetlands forfood, shelter and breeding sites.

Wetland fauna

Wetland ecosystems provide essential habitat for innumerable species of insects, amphibians, reptiles, fishes, birds, mammals and other fauna. Some of these animals depend on wetlands for food, shelter and/or breeding sites at some point in their life cycles; others are uniquely adapted to survive in specific types of wetland ecosystems.

A number of rare and endangered species are found exclusively in wetlands, including manatees, crocodiles, hippopotamus, cranes and many other species of birds. Other rare species may survive in relatively inaccessible wetlands, having been driven from upland regions by hunting or habitat loss (e.g. Royal Bengal tigers in the Sundarbans straddling India and Bangladesh, and jaguars in the Brazilian Pantanal).

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THE VALUE OF WETLANDS

Wetlands have somewhat belatedly been recognized as having a number of attributes which are essential for maintaining the health and integrity of the environment as a whole and which ultimately play an important role in safeguarding human health and welfare. These attributes include a wide range of ‘goods and services’, as well as other less tangible properties which are described in more detail below.

Wetland functions

Poised between land and water, wetlands function as buffers, filters and centres of biological productivity. Most wetlands perform some, or all, of the following functions:

l regulate the hydrologic cycle

By slowing flood waters, absorbing excess precipitation and releasing it gradually, wetlands play a key role in flood control and ground-water recharge, thus modulating some of the peaks and valleys of the seasonal water cycle. Ground-water aquifers recharged via wetlands are often important sources of drinking water and may also help to maintain baseflows in rivers and streams during the dry season.

l improve water quality

As water passes through wetlands, the combination of reduced current velocities and biochemical interactions with wetland soils and plants acts as a natural filter, removing or attenuating silt, nutrients, pathogens, metals, hydrocarbons and other pollutants. Numerous studies have documented significant improvements in water quality as a result of this biological filtration function. Wetlands treat municipal wastewater discharged from a number of tropical cities, including Calcutta and Kampala.

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l protect shorelines and control erosion

Dense wetland vegetation growing along river banks, estuaries and open coastlines protects unconsolidated soils from erosion. Wetland vegetation (particularly woody species) often effectively reduce current velocities, trapping sediment and functioning as wave breaks during storms. Root structures further reduce erosion by binding and stabilizing erodible sands, silts and muds.

l providefisheries habitat

Wetlands constitute essential habitat for many species of fish and crustaceans providing food, shelter, spawning grounds and nurseries for numerous marine, estuarine and freshwater species during part or all of their life cycles. Many economically important species, such as shrimp, are directly dependent on mangroves and other coastal wetlands.

Detmtion pond /wetland system I-onstructed to treat wastewater from a crocodile farm, North Queensland, Australia.

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l maintain biological diversity Wetlands support both significant numbers and a broad diversity of plants and animals. Some of these are confined to specific wetland habitats, others are opportunistic - seeking inaccessible wetlands as a last refuge -while others are migratory or seasonal residents. Wetlands also constitute an important genetic reservoir for certain plant species. For example, wild rice continues to be an important source of genetic material used in developing new strains of rice.

Wetland resources

In addition to the functions outlined above, many people rely on wetlands for a variety of goods and services, such as the harvesting of resources, livestock grazing and water supply.

&go palm is used for thatching roofs. Sepik River: Pqmcn New Guirwu

l forestry products

Many valuable forestry products are harvested from tropical wetlands. These include fuelwood (often used for making charcoal), timber, thatching, reeds, peat, bark, resins, honey and medicines. Mangroves are the main source of domestic fuelwood and timber in many coastal communities and are frequently harvested for commercial purposes as well. In Uganda, papyrus swamps are regularly burned and harvested for stems used in making screens and mats. Some wetland species such as the Dipterocarp trees of Indonesia’s swamp forests, yield valuable tropical timber.

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l wildlife products

Many wetlands contain abundant wildlife - mammals, birds and reptiles - which are hunted for meat, skins and eggs. Wild game, bird and turtle eggs constitute an important source of protein for many rural communities and are also valued as commercial products.

l forage resources

Many wetlands contain grasslands and trees that are grazed by livestock, serving as important oases of fodder particularly during the dry season. The Brazilian Pantanal, for example, is estimated to support over 5 million cattle. In many tropical regions, wetland vegetation (including mangrove foliage) is collected and sold as fodder or stored as dry-season cattle feed.

l fish products

Fish, molluscs and crustaceans are important harvested resources of both inland and coastal wetlands. It is estimated that two-thirds of the fish we eat depend on wetlands at some stage in their life cycle. In many countries of the humid tropics, fish provide the main source of animal protein. Fish products are also commercially valuable and provide an important source of foreign exchange. In Thailand, for example, fisheries exports (primarily shrimp) were valued at over two billion dollars in 1993 (Gujja & Finger-Stich, 1996).

Two-thirds of the jish we eat spend some part of their life-cycle in wetlands.

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l mineral resources

A number of mineral and energy resources are mined or otherwise extracted from wetlands. These include peat, sand and gravel, salt, coral and limestone, kaolin, heavy minerals, natural gas and petroleum. The extensive freshwater swamps and mangroves of the Niger Delta, for example, overlie the majority of Nigeria’s vast oil and gas reserves.

l water supply

Wetlands constitute an important source of water for human consumption, livestock, agriculture and industry. As such, wetlands often perform an important dual function, both storing essential water supplies and maintaining or improving water quality.

Naturally occuring mats of aquatic vegetation, which grow/accumulute at the water surface. Sepik Rivet Papua New Guinea.

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UNIQUE ASPECTS OF WETLANDS

IN THE HUMID TROPICS

Wetlands have similar functions and attributes at all latitudes; however, they may be particularly important in the humid tropics for several reasons. Firstly, because of the unique and frequently extreme meteorological conditions of this region, which include monsoons and cyclones, wetlands play a particularly important role in regulating the tropical hydrologic cycle, moderating river flows and buffering tropical coastlines from storm damage.

Secondly, wetlands of the humid tropics are highly diverse and unique ecosystems, supporting large and varied wildlife populations, including many rare and endangered species. Owing to their relative inaccessibility, some tropical wetlands constitute the few remaining ‘wild’ areas in otherwise densely populated regions (e.g. the Sundarbans in Bangladesh).

Thirdly, wetlands provide many essential goods and services to impoverished communities in the humid tropics which could not be duplicated or replaced in the current economic climate. These include essential services such as water quality improvement and storm protection, extractable resources (forest products, fish and game, minerals) and wetland-dependent activities, such as aquaculture and dry-season grazing.

Tropical wetland types and their distribution

Although wetlands are relatively common and widespread at many latitudes, the unique geographic and hydrologic features of the humid tropics have produced a number of distinctive types of tropical wetlands (e.g. Melaleuca swamp forests, papyrus marshes, mangroves) and a broader distribution of other wetland types, such as the enormous expanses of riparian wetlands which border tropical rivers like the Amazon.

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River floodplains and deltas

Some of the world’s largest rivers, including the Amazon, Orinoco, Ganges-Brahmaputra, Mekong, Niger and Congo, are located in the humid tropics. These rivers are notable for their strongly seasonal flows and their extensive floodplains and deltas. The wetlands associated with the floodplains and deltas of tropical rivers encompass virtually all wetland types and classes, and cover enormous expanses.

In many regions, floodplains predominate in coastal lowlands, evolving into estuarine deltas such as those of the Mekong, Ganges-Brahmaputra-Meghna and Niger, which are characterized by complex mosaics of marine, brackish and freshwater habitats. Alternatively, tropical rivers may seasonally flood low-lying areas far inland. These internal floodplains, often termed ‘inland deltas’, expand during the rainy season and may link millions of hectares of marshes, swamp forests, oxbow lakes and seasonally flooded grasslands. The Pantanal and Llanos wetlands of South America are among the largest of these tropical inland deltas, covering about 200,000 km* and 100,000 km* , respectively.

Floodplain of the White Volta Rive6 Ghana

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Swamp forests

Freshwater swamp forests are an important class of tropical wetlands growing in areas of still water which are flooded throughout most or all of the growing season (e.g. around lake margins, in oxbows and other permanently flooded parts of floodplains). Many tree species share adaptations such as buttresses, knees, prop roots and air roots, which allow them to ‘breathe’ in standing water.

Perhaps the world’s largest contiguous freshwater swamp forests are situated in the middle reaches of the Congo Basin, along the Ubangi and Congo rivers,

covering an area of more than 200,000 km*. These isolated and sparsely populated wetlands consist of swamp forest, interspersed with islands and peaty hummocks. The enormous Salonga National Park, 36,000 km* in size, has been established within this wetland system. An important wildlife reserve, this park is also home to several pygmy tribes, whose subsistence economy is based on the swamp forest resources.

Southeast Asia also contains vast expanses of freshwater and peat swamp forests. These are particularly abunclant in Sumatra, Borneo and lrian Jays/Papua New Guinea. Swamp forests cover an estimated 170,000 km* in Indonesia alone and show high biologic diversity, with records of over 100 tree species recorded on a single

0.1 ha plot in Sumatra. Swamp forests are often of great social and economic importance to nearby communities. Commercially valuable timber species, such as paper bark trees (Melaleuca spp.) and Dipterocarps, dominate many of these swamps and are extensively logged (Dugan, 1993).

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The Amazon Basin also contains large expanses of freshwater swampforests, particularly in the middle and lower basin, where 50,000-60,000 km2 are inundated by floodwaters for several months each year.

Freshwater marshes

Freshwater marshes are a diverse class of wetlands colonized by reeds, sedges, rushes and other grasses. Some larger marshes, dominated by papyrus, cattail and giant reed, contain standing water throughout most of the year and are sometimes referred to as swamps.

Freshwater marshes range in size from the small isolated dambos of southern Africa (frequently less than 1 ha in size) to the immense sawgrass mono-cultures of the Florida Everglades (7,000 km*) and the seemingly endless seasonal grasslands of the Venezuelan Llanos (over 100,000 km*). Freshwater and brackish marshes are also common in deltaic regions, including large areas of the Mekong, lrrawaddy and Red River deltas in Southeast Asia.

Situated in the upper Nile Basin, the Sudd is one of Africa’s largest wetlands, occupying an area of more than 30,000 km*. Approximately half of this area is permanently flooded and colonized by dense strands of papyrus, bulrushes and other emergents. The remaining areas consist of seasonally flooded grasslands, which are extensively grazed by the pastoralist tribes of the Dinka, Nuer and Shilluk.

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Mangroves

Mangroves are probably the most widespread coastal wetlands of the humid tropics and subtropics, thriving in the intertidal zones of estuaries and sheltered coastlines. There are about 70-80 different species of mangroves in total; however, mangrove plant communities vary widely from region to region. Mangroves are particularly dominant in the Indo-/West Pacific region, where they have the greatest species diversity.

Mangroves share a number of unique adaptations which allow them to survive the multiple stresses of high salinity, alternate periods of flooding and desiccation, anoxic soils and the occasional coastal storm. These include their ability to regulate internal salinity via salt exclusion and excretion, the development of prop roots and air roots to permit root resptration at low tide, and the production of viviparous, floating seedlings which facilitate efficient germination and dispersal.

Rhizophora rnangro~~ in Pohrtpei, Micronesia.

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The Sundarbans, which straddle the border between India and Bangladesh, are thought to contain the single largest mangrove forest in the world, covering a total area of about 6,000 km*. These mangroves constitute 45% of Bangladesh’s productive natural forest and are the nation’s primary source of wood and other forest products. Each year, the Sundarbans yield an estimated 68,000 m3 of timber, 183,000 m3 of pulpwood and 106,400 m3 of fuelwood. Despite this heavy use of the forest, the Sundarbans continue to support a diverse fauna of over 270 species of birds, 35 species of reptiles and 42 species of mammals, including the Royal Bengal tiger for which the Sundarbans is the last remaining stronghold (Dugan, 1993).

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CAUSES AND CONSElQUENCES OF

WETLAND LOSS

Wetland loss and degradation

There is little detailed information on the extent and rate of wetland loss throughout much of the humid tropics; however, the few statistics available suggest that the majority of losses have occurred in the past few decades and that entire ecosystems may now be under threat. In Peninsular Malaysia, for example, it is estimated that 90% of freshwater swamps have been drained for rice cultivation.

The accelerating loss and degradation of wetlands in the humid tropics can be attributed to a number of fundamental pressures: the demands of rapidly growing populations for land and other natural resources;

economic incentives for a quick profit; and, sometimes, concern for the health and safety of vulnerable human populations. In most cases, wetland loss occurs in a haphazard and piecemeal fashion; in others, the destruction has been systematic, sometimes supported by short-sighted development policies and financial

incentives.

Wetlands can be destroyed or degraded through many direct or indirect causes. Filling, clearing, excavation and dredging, for example, are all direct actions resulting in the immediate and deliberate destruction of wetland ecosystems. In many cases, however, wetland loss is more subtle and may go unperceived for a long time. Alterations to river hydrology, urban, industrial and marine pollution, and coastal construction or dredging can all ultimately result in the broad-scale loss of wetlands. Invasive species, such as the ubiquitous water hyacinth, may also cause severe degradation of wetlands.

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Agriculture

Rice and many varieties of cassava - the staple foods of many tropical cultures - are essentially wetland crops which require saturated soils during part of the growing season. Throughout history, wetlands have been directly cultivated, cleared or otherwise altered to obtain land suitable for the cultivation of these crops. With the advent of large water projects and irrigation schemes, however, the area of wetlands undergoing conversion has increased dramatically. In some cases, these projects have resulted in important increases in food production; however, far too often, large-scale intensive agriculture schemes have turned out to be inappropriate and expensive, sometimes accompanied by soil salinization, increased incidence of water-related diseases and other environmental and social problems.

Rice paddies, Indonesia

Aquaculture

In a number of countries of the humid tropics, some form of aquaculture has been traditionally practised in wetlands, as in the case of the coastal fish ponds, or ‘barachois”, of Mauritius or the domestic fish ponds commonly dug in the floodplain of the Ganges- Brahmaputra. In recent years, however, there has been a rapid expansion in aquaculture production, often at the

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expense of mangroves and other coastal wetlands. These operations can provide an important source of food, employment and foreign exchange earnings; however, in many cases, the concomitant destruction of wetlands has resulted in increased pollution, coastal erosion, reduced wild fish stocks and other adverse effects.

Fish pond, Angkor War, Cambodia.

Land reclamation

In many areas, particularly near cities where open, level land is in short supply, large areas of wetlands are ‘reclaimed’ for use as building sites, roads, airports and harbours. Many of the airports serving major tropical cities, for example, are constructed on former wetlands. Small islands are often particularly short of level, vacant land and new urban development is frequently concentrated in wetlands and shallow marine waters (e.g. Seychelles and Tahiti). Reclamation of urban wetlands is often justified on the grounds of demographic growth, progress and public health; however, the loss of important wetland functions, such as pollution control and storm protection, can be particularly debilitating in urban areas.

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MARICULTURE AND MANGROVE LOSS

Marine aquaculture (mariculture) has experienced dramatic growth in recent years due to rising demands, dwindling wild stocks, adoption of intensive production methods and subsidies at national and international levels. Marine shrimp, in particular, has become an important export product and hard currency earner for many tropical countries, especially in South Asia and South America. Although the economic benefits are initially high, there is growing concern over the environmental and social consequences of intensive mariculture and the long-term sustainability of these operations.

Environmental effects of mariculture include broad-scale destruction of mangroves and other coastal wetlands, water pollution from fish wastes, shoreline erosion and declining wild fish stocks. Furthemore, poorly planned mariculture operations may rapidly become inoperable owing to poor site selection and preparation, contaminated water and lack of availability of fry. Rehabilitation of abandoned mariculture sites can be complicated, as many of the conditions which originally fostered mangrove growth will have been altered.

l In the Philippines, it is estimated that between 176,000 ha and 210,500 ha of mangroves (44-90% of the country’s mangrove area) have been converted to fish ponds. In response to increasing awareness of the value of mangroves and concern at the rapid rate of loss, the government has taken a number of steps to minimize further mangrove loss. These include: conducting mangrove inventory programmes and classifying mangroves for more appropriate land uses; a ban on mangrove cutting; revisions to fish pond lease agreements; establishing mangrove buffer zones along rivers, shorelines and fish ponds; and initiating mangrove restoration projects (Siddal et a/., 1985; Villacorta & Van Wetten, 1993).

l Between 1961 and 1989, Thailand lost about 50% of its total mangrove area (175,000 ha), with conversion to aquacutture identified as the single largest contributor to this loss. Since 1987, there has been a major intensification of shrimp production, achieved through the expansion of the cultivated area and the adoption of intensive production methods. In addition to mangrove loss, shrimp mariculture has had a number of other environmental and social consequences, including marine and ground- water pollution, declining wild fish stocks and a dwindling coastal resource base (Flaherty 81 Karnjanakesorn, 1995).

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Altered hydrology

The direct destruction of wetlands through clearing, filling and excavation operations can be a labour-intensive, time-consuming process. Far greater areas of wetlands have been lost or degraded as a result of hydrological alterations, including dams, levees, dykes and various drainage works for agriculture, forestry and mosquito control. The construction of a single dam, for example, results in the drowning of all wetlands situated within the upstream reservoir area. More significantly, however, dam construction often causes the loss of seasonal riparian wetlands for tens to hundreds of kilometres downstream. Despite the large potential impact on fisheries, human health and welfare, and riverine ecology, these downstream effects are rarely fully evaluated in most environmental assessment procedures. Dredging and channelization of rivers, estuaries and coastal waters can also affect wetland hydrology by reducing overbank flooding and altering tidal exchange.

Lake Doviumbu, Papua New Guirtea

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WETLANDS AND DISEASE

A number of serious diseases are associated with wetlands, lakes and waterways of the humid tropics, although not necessarily specific to them. These include malaria, yellow fever, dengue, filariasis, shistosomiasis, encephalitis, dracunculiasis (Guinea worm), African trypanosomiasis (sleeping sickness) and onchocerciasis (river blindness). The threat of these and other diseases long kept people out of wetlands and helped preserve their integrity (UNESCOIIHP, 1992).

Through much of the recent past, eradication of disease has been one of the principle arguments advanced in defence of the drainage of wetlands. The history of drainage in Europe, where malaria was prevalent over wide areas in the early 19th century, is often cited as an example of how drainage can contribute to the eradication of disease. However, while the eradication of malaria coincided with better drainage, it is difficult in retrospect to separate the effects of drainage from those of improved sanitation and housing. What is clear is that many drainage efforts, while effectively destroying wetlands, have done little to eradicate the Anopheles mosquito, the carrier of the disease. This species still occurs in southern Europe, although malaria is now essentially absent. In the USA, ditching efforts of the 1930s and 1940s were unsuccessful because they barely affected the shallow depressions in the marshes where mosquitos laid their eggs (Maltby, 1986).

In contrast, some interventions in wetlands can significantly increase the numbers of disease vectors. In Guyana, for example, construction of sea defenses favoured breeding of mosquitos by preventing flooding by sea water. As a consequence, rates of malarial infection, which were generally less than 5% among children in areas without sea defenses, rose to as much as 75% along protected coasts. Similarly, in Java, the incidence of malaria rose rapidly after heavy clearing of mangroves resulted in the expansion of the sun-loving mosquito Anopheles sudiacus. The construction of reservoirs and irrigation schemes are also increasingly criticized for favouring malaria and schistosomiasis by providing year-round breeding areas for the mosquitos and snails which carry these diseases (Dugan, 1990).

The message conveyed by these examples is that, while wetlands certainly harbour disease, neither drainage nor conventional forms of intensive development necessarily provide healthy alternatives. Improved health is closely linked to improved socio- economic standards. By contributing to the latter, environmentally sound management of natural wetlands may, in many instances, be a more effective means of combatting disease than wetland destruction.

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Resource over-exploitation

Resource harvesting on both a small and large scale may affect and ultimately destroy wetlands. Growing domestic demands for forest products, fish and game have resulted in the depletion of these resources in many wetlands. Man- grove forests in the vicinities of large towns and cities, for example, may be rapidly denuded by the intense demand for fuelwood and timber.

Commercial exploitation of wetland resources for domestic and international markets is particularly difficult to control, both because of the efficiency of many commercial operations and the large profits to be made. Large-scale fishing, logging and mineral extraction operations have been known to devastate large tracts of wetlands and deplete resources in a matter of years.

Shells are havested from coastal lagoons and sold to \vholesalers i,z the curio trade, Zmt:ihat:

Pollution

Wetlands can be damaged or altered by a variety of pollutants, including silt, nutrients, oil and other toxic materials. Different plant and animal species show varying degrees of sensitivity to pollution. Bogs, for example, tend to be highly sensitive to small increases in nutrients, whereas cattails and reeds are so robust that they are frequently used for the treatment of wastewater. Mangroves are generally tolerant of some pollutants (e.g. silt), and highly sensitive to others (e.g. oil).

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Soil erosion and subsequent siltation can be a particular problem in the humid tropics, due to a combination of highly erodible soils, intense rainfall, steep slopes and poor land use practices. High silt loads in lakes, rivers and coastal waters may destroy or degrade wetlands, either by physical burial or by blocking light needed by submerged aquatic vegetation.

High levels of nutrients, derived from sewage, industrial discharges and agricultural run-off, have resulted in the eutrophication of many lakes and estuaries throughout the humid tropics.

Consequences of wetlands loss

The consequences of wetlands loss include the forfeiture of many valuable goods and services formerly provided free of charge. In the developed world, these losses have been countered to some degree by higher living costs, including investments in infrastructure such as flood barriers, seawalls, and water and sewage treatment plants.

In the predominantly poor countries of the humid tropics, however, the rural economy and human well-being are often closely dependent on wetland resources. National and household economies are rarely strong enough to replace goods and services formerly provided free of charge by wetlands. Thus, the consequences of wetland losses are fundamentally more severe, leading not only to increased taxes, but also to flood damage, contaminated drinking water, suffering and death. Similarly, in societies that rely on wetlands for animal protein, pasture, agricultural products or timber, any reduction in productivity is acutely felt. At best, an increased proportion of the household budget must be spent on subsistence, which, in many cases, means a lower-quality diet. In more extreme cases, wetland losses or degradation can lead to rising mortality rates, political unrest and emigration (Dugan, 1990).

26


c1 / THE NIGER RIVER DELTA I

The Niger River Delta is one of the world largest wetlands, occupying an area of 20,000 km* in southeastern Nigeria. This delta consists predominantly of freshwater swamp forests (11,700 km2) and mangroves (6000 km*), along with smaller areas of lowland rainforests and coastal barrier islands. The delta provides an important habitat for a variety of fauna and flora and shelters many rare and endangered species, possibly including the extinct pygmy hippopotamus. The delta is the result of thousands of years of sediment deposition from the Niger River, one of the largest in Africa. Over the past 30 years, however, 14 dams have been constructed on this river, reducing sediment transport by an estimated 70%.

The Niger River Delta is home to 6.7 million people, 70% of whom live in rural 1 communities characterized by extreme poverty, rapid population growth, lack of development, stagnant agricultural productivity and tenuous property rights. The delta also contains 75% of Nigeria’s petroleum reserves, providing over half of all government revenues as well as the majority of total exports.

Despite the tremendous natural and human resource bases, the region’s potential for sustainable development remains unfulfilled and its future is threatened by a variety of environmental problems. These include degradation of agricultural lands, erosion and flooding, fisheries depletion, deforestation, invasion by exotic species and environmental pollution.

Given the breadth and severity of environmental problems in the region, pollution by oil is a relatively minor source of environmental degradation; in fact, other oil-related activities such as road and canal construction actually cause far more damage. Nonetheless, oil production has been the source of severe conflicts in the region since the early 1970s. These conflicts have been described as expressions of long-term frustration at what inhabitants feel is inequitable distribution of oil income, while local communities shoulder the environmental and social costs of oil exploration and development (Moffat & Linden, 1995).

L I

27

A FRAMEWORK FOR MANAGEMENT

The unrestrained pursuit of multiple activities in wetlands generally leads to competition for finite resources, loss of essential free services, environmental degradation and, too often, to human hardship and conflict. Furthermore, development practices which ignore the dynamics of wetland ecosystems can be damaging, as illustrated by the unanticipated impacts of many large dams built in the humid tropics over the past few decades. If wetlands are to maintain their productivity and natural functions, there must be major improvements in the way we plan and manage development. Effective wetland management must be carried out according to sustainable development principles: based on a solid scientific foundation and taking into account the carrying capacity of the system, while balancing and integrating the demands of the various sectors which depend on these systems for their livelihoods.

Given their infinite variety, however, it should come as no surprise that there is no single ‘right’ way of managing wetlands. Solutions must be tailored to reflect the unique natural, socio-economic and political characteristics of each situation. To date, few of the developing countries of the humid tropics have engaged in comprehensive reviews of wetland conservation issues and needs. Uganda is perhaps to the forefront in this regard, while Kenya, Tanzania, Zambia, Bangladesh, the Philippines, Vietnam, Colombia, Peru and Venezuela have all held national workshops designed to lay the basis for long-term wise use of wetlands (Davis, 1993).

A fundamental requirement for successful resource management is a strong commitment on the part of governments and individuals. Difficult choices must be made between conflicting uses. Pragmatism, compromise

28


and the setting of priorities is of vital importance, especially where pressures and conflicts are high. The importance of involving local communities at an early stage cannot be overstated for, without their support, the most carefully constructed plan will almost certainly fail. Where peoples’ livelihoods are at stake, particularly in subsistence communities, restrictions should be balanced by new opportunities whenever possible.

Plarzting mangrows during afield trip, Cameroon.

Building awareness and support

One of the keystones of successful wetland management is building awareness about the value of wetlands and support for wise use among the general public, resource users and decision makers. Until people understand why they should safeguard wetland ecosystems and species, and are aware of the actions required to do so, many of the changes required to conserve these ecosystems will not take place. The value of the many direct and indirect benefits that wetlands provide, and the social and economic consequences of wetland degradation and loss, need to be documented and communicated to the widest possible audience (Dugan, 1993).

29


A number of approaches have been used to convey this message, such as media coverage, film document- aries, educational materials for schools, posters and pamphlets, special workshops for professionals, nature centres and pilot or demonstration projects. Ultimately, however, abstract approaches rarely change behaviour; awareness will come about most rapidly through practical demonstrations of wetland values. In many cases, local knowledge and traditional approaches to natural resource management can provide invaluable guidance in developing appropriate local management plans.

Understanding complex systems

Typically one of the first steps in a wetland management programme is the development of a national wetland inventory and wetland classification system. Inventories produce information in the form of maps, checklists and reports, and may range from the highly sophisticated to the rudimentary. Remote sensing and aerial photography are particularly useful tools for mapping wetlands, given the inaccessibility of many

wetland systems and the variable extent of interseasonal flooding.

I WETLAND MAP I

I- ! Flood hazard maps

30


Once wetlands have been mapped and classified, further information is needed on essentially all aspects of the natural and human environment, for example, hydrology, soils and biota, as well as socio-economic and cultural aspects of surrounding communities. Often, much of this data is already available in existing reports and maps. Collection of baseline information allows for routine monitoring, broadening the managers understanding of the system and making possible the systematic evaluation and adjustment of management actions,

Identify the problem/issue -.

Define objective

v

Establish hypothesis -a

0

Assess methods and choose variables - v

Assess feasibility and cost-effectiveness

v

Conduct pi/or study

*

Confirm sampling regime

v

Collect samples v

Analyse samples

0

Interpret data and report results d

v

Implement management actions B.

An important and often overlooked aspect of wetland classification is the ability to quantify, in economic terms, the functions and attributes of individual wetlands. A number of valuation methods are being devised to fill this need (see James, 1991 ab), and some work specific

31


to tropical wetlands is underway, notably in Central America where a manual for the economic assessment of tropical wetlands is being developed.

Many classes of tropical wetlands are poorly

understood, particularly forested and intermittently

flooded ecosystems. Fundamental research and the wide distribution of the results to wetland managers is essential to better understand how these ecosystems

function and how they may respond to various

pressures.

Making informed choices

The wide variety of activities focused on wetlands and the increasing intensity of these activities implies that, in most places, we will ultimately have to choose between competing uses and set limits, if we are to avoid escalating conflicts and resource degradation.

The planning process for sustainable resource management is based on the weighing of priorities, the translation of these priorities into accepted policies and, lastly, the definition of goals which form the basis of the management plan. A management plan should define the steps required to achieve the stated goals, identify the entities responsible for each action and establish a time frame for action and review.

32


Local participation is crucial if a management plan is to be appropriate to the needs of the existing population and, thus, accepted and complied with. At the national and sub-national level, informed support is also important, as the government will ultimately control the adoption of legislation, the appointment of key personnel and the provision of funding. In many countries, the central government plays an important role in initiating and supporting wetland management and in ensuring consistency between different states or regions.

The greatest challenge in resource management is the transition from planning to action. There are far too many comprehensive management plans gathering dust on shelves, while resource overexploitation and environmental degradation continue unabated. Bridging this transition successfully requires a combination of government commitment, popular support, competent and committed managers, and adequate funding.

Taking effective action

A variety of techniques are used in wetland management, which can be broadly grouped into regulatory and non-regulatory approaches. Regulatory approaches are founded on legislation and typically involve the setting of standards, issuance of permits and setting of penalties for non-compliance. Regulations form the basis of many successful management programmes; however, their effectiveness is largely dependent on surveillance, enforcement and public acceptance and support. As such, the regulatory approach can be time-consuming to set in place and requires relatively intensive administration.

Non-regulatory management approaches include such techniques as the provision of incentives and alternatives, acquisition of critical areas, infrastructural improvements, restoration of degraded habitat and public education. For certain issues, non-regulatory approaches may be more effective and efficient than traditional land- planning techniques.

33


In many countries. there are few restrictions on thejilling of wet1and.r for industry, infrastructure or other large-scale development.

Legislution

The legal basis for wetland conservation and management

lies in the establishment of wetland policies backed up by

relevant legislation. Wetland legislation, which may be

promulgated at the national or sub-national level, typically

defines wetland areas, identifies activities which are

permitted, restricted, or prohibited in wetlands and sets forth

the necessary administrative and regulatory framework.

In most countries of the humid tropics, a complex

assortment of local, regional and national agencies have

administrative responsibilities for wetlands and, more

often than not, their mandates overlap or conflict. Ideally,

management planning initiatives should be broadened to

include wetland management, for example in integrated

catchment management and coastal zone management

programmes. A few countries, like Uganda, have enacted

national policies and legislation specifically addressing

wetland management; more often, wetland issues are

addressed through environmental protection or water

resources management legislation. In many cases,

wetland conservation and management is overlooked

altogether.

34


Administration

A key factor in effective wetland management is the designation or establishment of a lead agency to take responsibility for wetland issues. This agency may have a variety of responsibilities, such as planning and policy development, research and data management, coordination, establishing standards, developing regulations, issuing licenses and permits, surveillance and enforcement. Responsibilities may be restricted to a centralized national agency or shared between national, regional and local administrative bodies. In situations where responsibilities for wetland resource management are fragmented, a coordinating board consisting of representatives from different ministries and other agencies may be required.

To operate successfully, agencies must be adequately funded and staffed by trained personnel. A frequently cited cause of failure in the implementation of many management plans is the lack of trained staff, particularly enforcement staff and technical staff, such as wetland ecologists, hydrologists and planners.

Regulations

Regulations are used to set limits on the types and intensity of activities occurring in or affecting wetland areas. Typically, certain activities are prohibited out- right (e.g. discharge of toxic wastes, blast fishing or clearing of mangroves), while others are controlled through the issuance of permits and licenses. To be effective, regulations must be backed up by surveillance and the consistent enforcement of penalties, such as fines, loss of licenses, confiscation of equipment and imprisonment.

Incentives and Alternatives

Offering incentives to promote sustainable use of resources can be an effective management approach, particularly where lack of surveillance and enforcement capabilities renders regulatory approaches untenable. Several examples of incentives include the following:

l Control of resources by communities or individuals through long-term leases or grants - By limiting competition and, in effect, granting ownership,

35


the incentive for careful husbandry of the resource base increases dramatically;

l Technical and financial assistance to improve the efficiency and profitability of existing activities without increasing adverse impacts - Extension services, for example, can be used to increase productivity and reduce impacts from existing mariculture operations. Fisheries cooperatives (particularly those which incorporate processing and distribution) can also significantly increase the profit margin for fishermen, thus reducing pressures on the resource base;

l Tax and otherfinancial incentives - These can be used to reward sustainable resource practices and to focus development activities on less sensitive areas.

Seaweed culture, Zanzibar:

36


r-

WETLANDS AND WASTEWATER TREATMENT

Wetlands are increasingly being used to treat contaminated wastewater from urban, agricultural and industrial developments. These aquatic ecosytems can be highly effective in removing silt, nutrients and other contaminants, due to a variety of physical, biological and chemical processes. Although both natural and man-made wetlands have been used for wastewater treatment, caution is advised in using natural wetlands, as some wetland types are highly sensitive to changes in hydrology or water quality. Wetland treatment projects range in size from small, vegetated detention ponds and buffer strips to extensive, highly complex systems like those described below.

Wetland treatment systems can be particularly effective in tropical climates, which lack the problem of annual die-off, but their design must take extreme rainfall conditions into account. These systems, with their relatively low-tech designs and minimal infrastructure, offer a promising approach to wastewater treatment in developing countries. However, the care needed in construction, operation, maintenance and monitoring cannot be overemphasized.

l Wetlands situated to the east of Calcutta, India, sustain one of the world’s largest and oldest integrated resource recovery systems, in which wastewater-derived nutrients are used for both aquaculture and agriculture. Two lakes covering an estimated 2,500 ha are filled with sewage and water. After an initial bloom of algae, carp and tilapia are introduced and the system is sustained by additional inputs of sewage fed into the lakes on a monthly basis. It is estimated that up to one-third of the city’s sewage is ultimately treated in this manner, yielding 7,000 to 8,000 tonnes of fish/year. Wastewater is also used to irrigate market gardens that provide the city with an average 150 tonnes of fresh vegetables each day (Ghosh, 1993; Edwards, 1985).

l In Florida, USA, a wetland measuring approximately 1,500 ha has been constructed to remove nutrients from agricultural run-off before it enters the Everglades National Park. This wetland, completed in 1993 at a cost of 13.9 million US dollars, is a demonstration project to be incorporated into the much larger Everglades Restoration Programme, which will ultimately include the construction and operation of six man-made wetlands covering a total area of approximately 16,400 ha. (Guard0 et a/., 1995).

A design for phosphorus removal

The Everglades Nutrient removal Project is a 3600-acre prototype for six wetlands designed to remove

phosphorus from agricultural nunoff entering the Everglades. As water flows through cattails and saw-

grass, phosphorus concentrations are

expected to cdecline from 170 ppb to

50 ppb at outflow. Sediment buildup

from decaying plants is heaviest at

the inlet because the excess nutrient

load spurs plant growth. Outflow

concentrations during the first year of

operation were reported to be between

20 and 40 ppb.

&dirnant buildup

I

37

c


Environmental impact assessments

Large development projects, such as dams and reservoirs, are usually accompanied by detailed environmental impact assessments at the national level and are routinely evaluated at the international level. In many cases, however, impacts on wetlands continue to be overlooked or underestimated with devastating results, particularly in areas outside the immediate project area. The causes of this situation are varied: poorly-trained or insufficient staff, manuals and guidelines which are sector- rather than ecosystem-based, failure to consult local communities and lack of follow-up monitoring.

The recently published Manual of Guidelines for Scoping EIA in Tropical Wetlands (Howe et al., 1992) provides some guidance in this respect.

Large drum mcry result in the loss of seasonal riparian wetlands for tens to hundreds of kilometres dowmtream.

38


Ibis colony island.

Protected areas

The acquisition of particularly productive, vulnerable or scenic areas for conservation purposes is a key element in many management programmes. The preservation of these areas in perpetuity constitutes an important insurance policy against over-development. Apart from their intrinsic value in maintaining critical habitats and species, conservation areas often play a valuable role in sustaining adjacent fisheries, and maintaining water quality, and are an important draw for tourism and recreation.

Wetland conservation areas can be acquired through governmental and non-governmental initiatives. Where funding for conservation purposes is in short supply, several creative approaches have been devised to raise it. These include debt-for-nature exchanges, taxes on tourism revenues and park user fees.

Establishing a conservation area is relatively straightforward; maintaining it as such can be vastly complicated. There are far too rnany nominally protected areas where business transpires as usual - farmers farm, hunters hunt, miners mine and the official ‘Conservation Area’ looks no different than the adjacent unprotected lands. To be successful, protected areas require on-going maintenance and monitoring. Most try to incorporate the needs of local communities within their management framework.

39


Wetland restoration and creation

In some cases, wetland restoration may be effective in recreating or restoring degraded wetlands. However, this is usually recommended only as a last resort, as restoration is generally difficult, expensive and the results are notoriously unpredictable. Artificial wetlands are rarely able to replace or mimic adequately the ecological functions of natural wetlands and are rarely considered to be suitable substitutes for undisturbed systems. Where restoration of degraded ecosystems is envisaged, manipulation of wetland hydrology is often the key to success, accompanied by long-term monitoring and maintenance.

The Everglades: Wetlands restoring wetlands

A key component of the $685 milion Everglades restoration project is a series of six constructed wetlands to be used as ‘storm water treatment areas’ (STAs) to remove excess nutrients from the Everglades Agri- cultural Area runoff. Treated water from the six STAs will flow into the Everglades Projection Area (arrows). A prototype of these treatment areas, the Everglades Nutrient Removal Project (ENR), is in operation.

40


WETLAND REFORESTATION

l In the Philippines, mangrove reforestation has been initiated as part of the Central Visayas Regional Project, jointly funded by the World Bank and the government. Mangrove species bear viviparous seeds (propagules) which are easy to collect, transport and plant, and 70-95% of planted propagules survive. Planting seeds 1 m2 apart (10,000 seeds/ha) required a labour input per person of 5 days/ha. Subsequent maintenance, such as removing barnacles from infested stems, has sometimes been necessary. Different mangrove species are planted according to site-specific conditions.

Within two to three years, fishermen reported increasing yields of fish, shrimp and shellfish in the vicinity of the young plantations. Coastal erosion was reduced soon after planting and, by the end of the third year, large root systems covered the soil and formed a dense mat, breaking the impact of strong waves and water currents. Sediments accumulated at a rate of about 5 cm/year. Newly planted mangroves reached a height of 4.5 m after was years and helped to lessen the effects of typhoons. The cost of planting is about US$416/ha, including labour costs; US$lOO/ha excluding labour (Villacorta & Van Wetten, 1993).

l Restoration of the Melaleuca forests in the floodplain of the Mekong Delta, Vietnam, has been attempted for almost two decades with some success. Forests are established by sowing seed by hand and this has achieved reasonably uniform stocking in most areas with densities in the range of 30,000 to 50,000 trees per ha. However, in the absence of thinning, intense competition between young trees results in a very limited diameter growth in most trees. Support from local communities is being enlisted by granting farmers long-term leases of 10 ha plots, which will surround a core forest reserve. Each farmer will be required to plant 7.5 ha with Melaleuca, with the remaining area to be used for agriculture and housing. The government plans to eventually reafforest 70,000 ha in this manner (Due, 1993).

l In Bangladesh, approximately 120,000 ha of mangrove plantations were planted from 1966 to 1991. Some of these were established with assistance from the World Bank, which has supported three coastal forestry projects valued at US$35 million since 1980. Bangladesh’s mangrove plantations have multiple uses, including protection from cyclones, stabilization of newly accreted coastal land, harvesting of forestry products for domestic and commercial uses, and wildlife conservation (Katebi, 1992.).

41

CONCLUSIONS

Tropical wetlands flourish at the interface of land and water, producing ecosystems of astonishing beauty, diversity and productivity. These wetlands provide habitat for countless birds, mammals, fish, reptiles and other creatures, as well as essential free goods and services upon which many rural communities depend. The loss of tropical wetlands stems from many causes, particularly conversion to agriculture and aquaculture; construction of dams and other hydrologic schemes and urban land reclamation. In the humid tropics, the extent and rate of wetland loss are not well-documented, but appear to be

severe in many areas. What is clear, however, is that many poor communities cannot afford the loss of goods and services provided by these ecosystems.

The sustainable use of natural resources, including wetlands, is a universally applauded goal, although the specific mechanisms for effective management are still elusive. Certainly, there is no universal recipe for success: wetland management must evolve according to the unique physical conditions, human needs and resources available to each country. However, a number of fundamental lessons have emerged from management efforts around the world. These include:

l the need to build awareness about the value of wetlands and support for management amongst the general public, users, and decision-makers;

l the importance of an integrated approach. Wetlands are an essential component of both coastal and freshwater systems and should thus be incorporated in both coastal zone management and catchment management

planning.

42


l stronger institutions and better coordination are required at all levels between organizations administering wetland areas, managing wetland resources, or whose activities may have an impact upon these areas and resources;

l an improvement in the collection and communication of information about wetlands and their resources.

The e.rtent and rote of tropicnl wetland loss is not well documented.

At the international level, much has been done to promote awareness of wetland values, to encourage information exchange and technology transfer, and to develop management plans for specific wetland systems and/or species. The Ramsar Convention provides the single most important framework for intergovernmental cooperation on wetland issues. However, a number of other international governmental and non-governmental organizations have programmes related to tropical wetlands and/or hydrology. These include the World Conservation Union (IUCN), International Waterfowl and Wetlands Research Bureau (IWRB), World Wildlife Fund for Nature (WWF), UNESCO and UNEP, as well as regional organizations such as the Asian Wetlands Bureau (AWB) and Wetlands for the Americas (WA).

43


Multilateral and bilateral development agencies also play an important and sometimes contradictory role in wetlands management. Development projects funded by these agencies have sometimes resulted in the destruction or degradation of large areas of wetlands, As the value of wetlands has become more widely recognized, however, some development agencies are now including wetland issues within their environmental assessment procedures and, in some cases, are directly funding tropical wetland conservation projects.

44


REFERENCES /

FURTHER READING

Bonell, M.; Hufschmidt, M.; Gladwell, J. S. (1993) Hydrology and Wafer Management in the Humid Tropics. Hydrology Research Issues and Strategies for Water Management. UNESCO, Paris; Cambridge University Press, Cambridge.

Bullock, A. (1993) Perspectives on the hydrology and water resource management of natural freshwater wetlands and lakes in the humid tropics. In: (M. Bonell era/., ed) Hydrology and Water /Wanagemenf in the Humid Tropics. Hydrology Research Issues and Strategies for Water Management UNESCO, Paris; Cambridge University Press, Cambridge.

Davis, T. J. (1993) Towards the Wise Use of Wetlands. Report of the Ramsar Wise Use Project. Ramsar Convention Bureau, Gland, Switzerland.

Davis, T J. (1994) The Ramsar Convention A&m.& Ramsar Convention Bureau, Gland, Switzerfand.

Due, L. D. (1993) Rehabilitation of the Metaleuca floodplain forests in the Mekong Delta, Vietnam. In: (T. J. Davis, ed.) Towards the wise Use of We&ands. Ramsar Convention Bureau, Gland, Switzerland.

Dugan, I? J. (1996) Wetland Conservation: a Review of Curpenf &W&Z sod Required Action. IUCN (World Conservation Union), Gland, Switzerland.

Dugan, P. J. (1993) Wetlands in Dangler. A Worfd Conservation Atfas, Oxford University Press, New York.

Edwar@, P (1965) Aquaculture: a cwnponent of Low Cost SaniiraMon Tectmolclgy World Bank, Washington, D.C.

Fintayaon, M. (1996) Des/gning a ARonitorsns Prommme. Ramsar New&et&r No. 22. Ramsar Convention Bureau; Gland, Switzerland. - -

Ftntayson, M. ; Moser, M. (199391) k%?&nds. Facts on Fife, New Yorkllondon,

Flaherty, M.; Karnjanakeeorn, C. (1995) Marine Shrtrnp Aquaculture and Natural Resource Degradation in Thailand. Environ~er& #artage#e#t. Vot.19: 1,

_,_( Ghosh, D. (1993) Towards sustafnabte development of,the Calcutta wetfands. In: (7. J. Davis, ed.f i Towards the wise Use d Was, Ramsar Conventin Bureau, Gland, Switzerfand.

1, Guardo M.; Fink, L.; Fontaine, T. D.; Newman, S.; Chimney, M.; Bearzotti, Ft.; Goforth, G. (1996) j

i :I‘ large-scale Constructed Wetiends for Nutrient Removal from Stormwater Runoff: an Everglades

i ‘Restoration Project. mti~m~f3rd Management. Vol.19: 6* :;j.-: 0 :&#& B.; Finger-Stfch, A, (1996) Whet priceprawn? shrimp aquaculture’s impact in A&a. Envilzmmenr.

I, Vol. 38: 7.

! Wamifton, L. S.: Snedaker, S. C. (1964) Handbook for Mangrove Area &&magefner?t fUCN (World Conservation i Union), Gland, Switzerland; UNESCO, Paris: East-West Centre, Hawaii, USA. ,, *‘, Howe, C. P.; Ctaddge, C. F.; Hughes, Ft.; Zuwendra (1992) Manual of GukWnes for Scoping EIA in liopkz~al

‘. ~_ W&&r&~~Asian Wetlands Bureau, Kuala Lumpur. ; .)

,: l~~,~o~ Conservation Union], in press. Manual on the Management of Topical Pearlands. ..,’

~~~~~~~ Conseffation Unfon),‘ in press. Handbook on the Managerncwtt ol’ froplcal Tidal Wetlands.

~~~‘~~,~~~ Programme Newsletter. IUCN (World Conservation Union), @and, Switzerland. _ .:i: il : , _

45


Katebi, M. N. A. (1992) Mangrove wetlands and forest management in Bangladesh. In: Towards the wise Use of ’ Wetlands (T. J. Davis, ed.) Ramsar Convention Bureau, Gland, Switzerland.

Maltby, E. (1986) Waterlogged Wealth: Why Waste the World’s Wet Places. Earthscan, London.

Hughes, R. H.; Hughes, J. (1992) A Directory of African Wetlands. IUCN (World Conservation Union), Gland, Switzerland.

Mitsch, W. J.; Gosselink, J. G. (1986) Wetlands. John Wiley & Sons, N.Y.

Moffat D.; Linden, 0. (1995) Perception and Reality: Assessing Priorities for Sustahabie Development in the Niger River Delta. Ambio. Vol. 24.

Naiman R. J. & Descamps, H. (1990) The Ecology and Management of Aquatic and Terrestrial Ecofones. MAB/UNESCO, Paris.

Ramear Newsletter, Ramsar Convention Bureau, Gland, Switzerland.

Scott, 6. A (1993) A Directory of Wetlands in Oceania. Asian Wetlands Bureau, Kuala Lumpur. Malaysia.

Scott, D. A.; Carbonell, M. (1986) A Directory of Neotropical Webnds. tWRB Slimbridge and, Cambridge, UK.

Scott, D. A. (ed.) (1989) A Directory of Asian Wetlands. IUCN (World Conservation Union), Gland, Switzerland

Scott, D. A.: Poole, C. A. (1989) A Status Overt&w of Asian tl&@?c&. Asian Wetlands Bureau, Kuala Lumpur, Malaysia.

!?&f&t ‘At&rue; Murray (1985) In; (Qark, ed.) Coastal &reo~

U~~~C#~~P (@92) Water and I-/e&&. IHP Humid Trap”& ‘, ; wreve and marine resources in is @cl.) Towards the wise Use of Wetlands.

en&y Press, New York.

., ,~ ._

raphs are by the author & ~f~llo~~~ excep&ns: . .

d Environ&mf Aust ra& P. Bally,@ World W&fe@fe Federation for Nature. L Kriwokert@ Unive@y of Tasmania.

. . se--^ -7. se--^ -7. : : “,I z z I? Duaan/@IUCN. ‘( R,Dugan/@ IUCN. ‘( Ft. JaenschR Wet@+& International. .

Un&et-sity of Tasmania. Wet&ids International. Environment Australia.

lands International.

iversity of Tasmania. lands International.

‘-,

al Territory Parks z&d Wildlife,Service. . _

46


ACKNOWLEDGEMENTS

The author acknowledges with thanks the reviews and comments provided by Bruce Davis (University of Tasmania), Allison Shepherd (Australian Nature Conservation Agency) and John Gladwell (HYDRO TECH International, Canada).

Grateful thanks go also to the American Chemical Society for permission to reproduce the two figures on pages 37 and 40, and to all other copyright holders cited in the present publication for their kind permission.

Text and basic design by Dr Christine Coughanowr Brinsmead Road, Hobart, Tasmania (7005 - Australia)

Detailed layout by Yvonne Mehl

47

Scientific understanding of interactions between land, vegetation, oceans, atmosphere and human actions is one of the IHP’s priorities in the humid tropics. By definition, the problems are multidisciplinary and the IHP encourages an integrated approach to studying the various links and linkages that make up the world’s water cycle. This is accomplished through globally and regionally coordinated cooperative efforts by networks of experts and organizations, facilitated by the establishment of regional administrative centres - “centres of centres”.

In the long run, of course, IHP wants to see the application of hydrological research results to integrated water management strategies. These include: improving agricultural productivity, providing water for irrigation and people, controlling urban water problems and developing land-use practices that meet these needs while, at the same time, reducing flood damage and the degradation of soils and water. It is expected that good water management in the humid tropics will also bring benefits to areas outside the region. Sustainable development and management is the key to long-term survival.

The Humid Tropics Programhe, September 1991.

IHP HUMID TROPICS PROGRAMME SERIES

For further information, contact:

No. 1: No. 2: No. 3: No 4: No 5: No 6: No 7: No 6: No 9: No 10:

No 11:

The Disappearing Tropical Forests Small Tropical Islands Water and Health Tropical Cities: Managing their Water Integrated Water Resource Management Women in the Humid Tropics Environmental Impacts of Logging Moist Tropical Forests Ground Water Not allocated Environmental Impacts of Converting Moist Tropical Forest to Agriculture and Plantations Helping Children in the Humid Tropics: Water Education

UNESCO Division of Water Sciences International Hydrological Programme 7, place de Fontenoy 75700 Paris - France (Tel.: (33 1) 45 68 40 02) (Fax: (33 1) 45 67 58 69)

Documents

WETLANDS OF THE HUMID TROPICS - UNESCOunesdoc.unesco.org/images/0011/001160/116084Eo.pdfspectacular wetlands of the humid tropics include the vast river floodplains and deltas of the