Correction: 15 February 2008

www.sciencemag.org/cgi/content/full/319/5864/756/DC1

Supporting Online Material for

Global Change and the Ecology of Cities

Nancy B. Grimm,* Stanley H. Faeth, Nancy E. Golubiewski, Charles L. Redman, Jianguo

Wu, Xuemei Bai, John M. Briggs

*To whom correspondence should be addressed. E-mail: nbgrimm@asu.edu

Published 8 February 2008, Science 319, 756 (2008) DOI: 10.1126/science.1150195

This PDF file includes:

SOM Text Figs. S1 to S6 Table S1 References

Correction: The revised supporting online material contains an updated fig. S4, which corrects typographical errors in the diagram and clarifies attribution of the research program and photographs.

Global Change and the Ecology of Cities: Supporting Online Material

Nancy B. Grimm, Stanley H. Faeth, Nancy E. Golubiewski, Charles L. Redman, Jianguo Wu, Xuemei Bai, and John M. Briggs

1) Further notes on origins and meaning of urban ecology In contrast to the apparent aversion of U.S. ecologists to the urban milieu, urban ecology

was an active pursuit in Europe and Australasia in the 1970’s–1990’s (S1, S2). Early work on urban metabolism in Hong Kong (S3) presaged the more recent extensions in the field of industrial ecology (S4-S7). European urban ecology set important groundwork for understanding the effects of urbanization on biodiversity and individual species’ responses to urban environmental change that continues today with conservation efforts (S1, S8-S10). In the U.S., urban sociologists of the 1920’s used the term “urban ecology” to describe their work, but their intent was to apply analogies from the ecology of the day to understanding human behavior and environment in cities (S11). This fruitful avenue for research continues today with very interesting approaches to human–environment interaction in the fields of political ecology, urban sociology, and urban geography. Some have maintained that a new urban ecology was ushered in with the establishment of the long-term ecological research urban program and other NSF-supported research (S12- S15), since these efforts focus on cities as ecosystems and address not only ecology in cities, but the ecology of cities (S14). Whether or not urban ecology is a new field, inarguably it has seen dramatic advances over the past decade. Urban ecology now not only has its own journal, but new programs have sprung up within the U.S. Forest Service, the Australian CSIRO Sustainable Ecosystems program, the International Human Dimensions Program on Global Environmental Change, and numerous other national and international entities. Furthermore, urban ecologists are collaborating with a host of other scientists and engineers working in the urban environment, so that the new discipline—if it is one—takes a hybrid approach from many different disciplines (S16).

2) On footprints, population density, and consumption behavior Urban geographers and planners ask whether compact or less dense distributions of

people have the greater environmental impact. Assuming equal population size, is it more environmentally sensible to have high-rise, tightly packed, urban environments or suburban ones? Is a rural lifestyle compatible with sustainability? The answer depends upon relative income and resource consumption by the residents in question. To illustrate this, consider per capita CO2 emissions. In many developing countries, a great disparity exists between the rural poor and relatively well-off urban populations. In these cases, the urban population often exhibits greater per capita consumption of heating or auto fuel, larger homes, and smaller households (S17). In wealthy nations, such as the U.S., suburbanization and exurbanization resulting in land change in the sparsely populated areas between cities is a major land-use trend (S18). In this case, the rural population may have the wherewithal to build large homes and commute long distances to workplaces, thus their impact in terms of CO2 emissions would be greater than the urban population with access to public transportation or shorter commuting distances (S19). Certainly, urban form can affect transportation and mobility patterns and more dispersed patterns can lead to higher energy consumption (Fig. S1, Table S1).

As a summary tool, ecological footprints assess a specified lifestyle (S20). Therefore, comparisons intended to reveal ecological implications of population density need to be made on

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the basis of the same lifestyle, such as how urban form influences the ecological footprint of a hypothetical urban person. So, to compare the city vs. rural dweller in this case would be to look at variance in footprints of the same urban population engaged in urban activities, depending on various consumption levels associated with living in the city, suburbs, or exurbs.

A second comparison of population density-- between the "city" dweller, engaged in the industrial/ information/ service economy, and the "rural" dweller, who may be involved in primary production activities (for local and/or foreign markets) or even subsistence farming, remains to be elucidated. Certainly, the ecological footprints of nations belonging to different income classes have been made (S21, S22), but specific analyses of density and affluence are not as readily available. In this case, comparing the effect of population density on ecological footprints would be describing different things (an “apples to oranges” comparison) since distinct populations are consuming in different ways for different ends. Resource requirements for different patterns of consumption or levels of affluence vary, of course (e.g., S23, S24) (Figure S2). When assessing issues of population density and settlement pattern across economic sectors, issues of consumption, affluence, and well-being also must be considered, and such analyses may require tools and frameworks other than the ecological footprint (S25, S26).

3) Human modifications of hydrologic systems Many cities have begun to embrace the concept of non-structural water management.

Examples are provided from Littleton, CO, USA (Fig. S3); Auckland, New Zealand (Fig. S4); and Melbourne, NSW, Australia (Fig. S5).

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basic s ubsistence low est requirement cultural

highest requirement cultural

Consumption pattern level

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tive

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in la

nd u

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Figure S1. Declining per capita fuel consumption with increasing urban density in cities throughout the world (S27).

Figure S2. Relative land requirements for the basic and the subsistence level, and actual relative land requirements for the cultural level. The latter requirements are based on existing food consumption patterns. (Adapted from (S23).

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A B

Figure S3. In the early 1970s, the citizens of Littleton, Colorado (USA) campaigned for non-structural flood management along the South Platte River in response to Army Corps of Engineer plans to channelize the river. The resulting South Platte Park (A), which set legislative precedents, is a 878-acre natural area encompassing the South Platte River and its floodplain downstream from Chatfield Dam, the only non-channelized portion of the river in the Denver region (B, C). The park, comprising riparian woodlands, grasslands, and marsh wetlands, hosts over 300 species of vertebrates. The Carson Nature Center (A) serves as focal point for ecological restoration, public education, and recreation opportunities provided by the park. Map source: South Suburban Parks and Recreation, http://www.sspr.org/southsubnew/page_disp.asp?tl=5&p=SPPmap2.jpg. Photo-graphs by Arthur C. Golubiewski.

C

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A B C

D

KEY (panel D) Material Key properties Plants Oioi or jointed rush, Apodasmia similes (Leptocarpus) Nil Freeboard above soil to top of grated overflow upstand VCU mulch Long-fibre, non-floating, composted, 46% carbon, 38cmol+/kg

CEC Stones Erosion control apron around inflow T pipes Lawn mix Topsoil mixed with 30% pumice sand, 29% P retention, 2.4%

carbon, 18 cmol+/kg CEC Overburden Limestone qarry overburden, 87% P retention, 0.4% carbon,

18 cmol+/kg CEC Sand Sand bed and under-drain material were similar, 2% P

retention, 0.04% carbon, 3 cmol+/kg CEC Plastic liner Impermeable liner stops water getting in or out except by flow-

monitored pathways

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Figure S4. Low impact urban design and development (LIUDD) in New Zealand. In the greater metropolitan area of Auckland, New Zealand, low-impact systems, such as rain tanks, swales, and rain gardens, have been investigated by Landcare Research as a way to use natural systems to mitigate and prevent stormwater runoff and associated pollutants (S28). Not only can the load on urban infrastructure be reduced, but LIUDD systems also provide on-site sources of water for irrigating lawns and gardens, thereby reducing demand from the urban water supply. Photos depict various systems: (A) rain tank used to collect roof runoff for re-use in Auckland (S29); (B) raingardens at Waitakere Civic Centre; (C) swale (minimal ponding depth, shallow substrate) at Auckland Netball courts; and (D) raingardens treat road runoff and use New Zealand native plants in combination with engineered substrates (Paul Matthews Road, North Shore). Photographs (B-D) by Robyn Simcock, Landcare Research.

A B

C D

Figure S5. Based upon work of urban ecologist Chris Walsh and his colleagues (e.g., S30), the Melbourne (Australia) water department was convinced to experiment with new designs for handling stormwater on a neighborhood scale. Public education efforts (A), special roof gutters and swales for collecting roof runoff, redesigned curbs that funnel water into pervious grassy areas rather than down the street (B), a street design that features pavement sloping toward the center, where a gravel-filled chute is buried and planted with grasses (C), and a marsh (complete with walkways for recreation) at the base of the catchment (D) are among the “retrofitted” designs employed. After one year, total water runoff was reduced by 80% and nutrient discharges were also reduced. Photographs by N. B. Grimm.

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Figure S6. Modified conceptual view of reconciliation ecology (S31, S32), where human-modified habitats are designed and managed to maximize aspects of biodiversity (e.g., species richness and evenness, and food web structure) while providing socioeconomic benefits (e.g., aesthetic value, revenue-generation, (S32, S33) and ecosystem services (e.g., flood control, pollution abatement, (S34). The light area of the peak, where the three axes are maximized, is the ideal in terms of design and management of habitats. In reality, there are usually tradeoffs among the three axes (e.g., S34), especially between socioeconomic benefits and the other two.

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Growth rate Metropolitan rings 1986 1991 1996 1986-1996 Barcelona 0.01 0.014 0.017 0.72 First ring (A1) 0.015 0.022 0.026 0.70 Second ring (A2) 0.022 0.033 0.041 0.87 Satellite cities 0.014 0.022 0.029 1.02 Satellite city commuting area 0.030 0.044 0.057 0.91 Metropolitan corridors 0.028 0.041 0.056 0.99 Total Barcelona

Metropolitan region 0.015 0.023 0.030 0.94

Table S1. Evolution of the per capita ecological footprint of commuting (ha/capita) 1986-1996 (adapted from S35). A study of the effects upon transportation footprints of suburbanization in Barcelona between 1986 and 1996 found the total and per capita ecological footprints doubled, average trip distances increased 45% (from 4.6 km to 6.7 km), and the proportion of trips made by car increased by 62% (from 22% to 35%) (S35). Measures of urban form, such as population density and accessibility, explained municipal footprints more than municipal family income and job ratio, and urban form itself affected the transportation footprint.

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S28. Landcare Research. LIUDD Stormwater Treatment (http://www.landcareresearch.co.nz/research/built/liudd/stormwater.asp).

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