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About UNEP
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United Nations Environment Programme
Division of Technology, Industry and Economics
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Cities As Sustainable Ecosystems (CASE)

Cities are pollution sources and sinks, and people living in them utilize resources and generate waste. Cities also import resources and export pollutants, although these activities have limits. Cities themselves have limited carrying capacities. The infrastructure of a city influences its carrying capacity. If the infrastructure of a city is eroded, it becomes increasingly difficult, if not impossible, to achieve sustainable environmental objectives. 

Ideally, a sustainable city must have adequate infrastructure and flexibility to support the needs of its population, particularly its poorest citizens, as well as those of the ecosystem as a whole. Sustainable cities should not use resources faster than they can be replenished or substituted for, nor generate pollution faster than it can be assimilated. Rather than devouring water, food, energy, and processed goods, and discharging the remains as pollutants, cities should align their consumption with realistic needs, produce more of their own food and energy, and put much more of their waste to use. 

Without new urban environmental management methods and approaches, there is a danger that past problems of environmental degradation and ecological impoverishment will continue. Given that these environmental problems have arisen primarily because of inappropriate management and a lack of understanding of the impact of management practices upon the environment, it is essential for new management methods to be researched, developed and implemented. Unless cities change their management practices, the resources they expend on protecting the environment will be wasted.

CASE: IETC Related Activities
Basic research and development in CASE is necessary to provide the objective understanding and support required for the integration of environmental considerations throughout the economy of the city. It is also a necessary prerequisite for the development and implementation of economically and environmentally efficient regulatory structures, currently a critical policy deficiency. Related activities include:

  • Planning and implementing a series of studies to understand and model stocks, flows, and logistics of material movements throughout city for all major materials, including both renewables and non-renewables, and wastes. Environmental impacts and human/ecosystem exposure data could be mapped onto these models, providing the basis for developing environmentally preferable processes, and helping the urban and civil sectors and labour markets adjust to an environmentally preferable world. Such knowledge is also critical to support the development of valid, efficient, risk- based environmental regulations. Indeed, it is difficult to see how environmental regulation can be effective in the long term without such data and models.
  • Developing an integrated approach using Environmental Risk Assessment (EnRA) and Environmental Technology Assessment (EnTA) models of energy production and use, water usage and conservation, waste production and disposal, and transportation systems. These models can be linked where feasible to technology, demographic and other systems, with risk assessment and technology option overlays. As above, this will facilitate the identification of optimal national and local strategies and programmes to produce environmentally and economically preferable (and, hopefully, eventually sustainable) energy, water, waste, transportation, and other EST systems.
  • Developing integrated models of urban communities, including small relatively self-contained cities, larger cities with surrounding suburbs, and large megalopolises with decayed centres and most business activity decentralized throughout the suburbs. Such models would include transportation, physical infrastructure, food, energy and other systems. This would facilitate identification of major sources of environmental impacts; patterns of activities, which give, rise to them, and potential environmentally preferable EST or mitigation options.
  • Developing integrated models of specific urban sectors of particular economic, environmental, or cultural importance - including, for example, agriculture, forestry, waste and water management - which could then be used to understand how they might be affected by an increasingly environmentally sensitive world. Such an approach could be particularly important in mitigating potential economic and employment shocks of discontinuous environmental, and/or related economic and regulatory, changes, and in supporting the continuous improvement in quality of life while reducing attendant environmental impacts.

One of the hypotheses of CASE is that rapid evolution of environmentally sound technological (EST) systems is a prerequisite for improvement of quality-of-life in an environmentally sensitive world. The fundamentals of technological evolution and diffusion throughout the economy are, however, poorly understood. Even less is known about the optimum, or maximum, rates of technological evolution, the associated economic and labour costs and benefits (and how they could be optimized), and how such variables differ by class of EST. (For example, it is apparent that moving to a solar-hydrogen based energy economy will be significantly more difficult, and a far more lengthy process, than substituting for CFC-based cleaning systems in electronics manufacture.) The CASE approach to such issues may well produce valuable insights into:

  • Investigating the interdependency of legal, economic, cultural, scientific and technological activities and policies as they affect environmental protection and the evolution of EST systems. 
  • Different regulatory tools and approaches in terms of how cities and citizens behave. 
  • Developing efficient public environmental management structures that support the adoption of appropriate EST systems.

CASE can provide information which can assist in the prioritization and reordering of environmental values, both among themselves (e.g., is ecotoxicity, human carcinogenicity, or global climate change more important?) and in the broader context of other social values (e.g., employment, private property rights). While it is doubtful that an unambiguous, uncontentious prioritization of values is possible, some broader consensus is necessary to provide support for further progress. How, for example, can an urban planner be expected to design a "green" residential area when what is environmentally preferable cannot be made clear? This is not a trivial task. It requires the development of comprehensive environmental risk assessment (EnRA) methodologies, which evaluate and balance risks and possible benefits on a systems-wide basis. 

Clearly, cities are able to develop on their own the overarching legal, regulatory and economic incentive structures, which will be necessary to support the integration of environment into all urban activity. They are also able to restructure existing regulatory systems - including environmental and other related regulatory regimes as consumer protection and government procurement - so that they avoid unnecessary interference with the achievement of environmental quality while still meeting their original objectives. Similarly, in a world where environmental perturbations are not restricted to political boundaries, it is obvious that the CASE programme, and others like it around the world, must be linked together in a collaborative international network. Existing international organizations, both quasi-governmental and private, must assume increased responsibility in this area and proactively support the integration of science, technology and environment in all urban activities. IETC is actively pursuing development of CASE is currently commencing activities with various partner organizations in this important area.

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