Social and natural sustainability are important for sustainable development of human settlements (Yoshino, 1994). Coping with flooding and drought; getting potable water, breathable air, and a stable environment; and so forth have been prime concerns of urban planners, engineers, governments, and citizenry for thousands of years (Priscoli, 1998). Climate change simply adds to the challenge. Some of the adaptations probably would take place autonomously, but some adaptations may be much improved by taking climate into account explicitly (Wood et al., 1997).

Questions such as �adapt to what?�, �who or what adapts?�, and �how does adaptation occur?� (Smit et al., 1998) are still difficult to answer in a strict sense. Management, adaptation, and vulnerabilities have been discussed for settlements in coastal (Fukuma, 1999/2000), arid, agrarian (Dougu�droit, 1997; Dougu�droit et al., 1997; Le Treut 1997), and urban regions (Maunder, 1995). To be successful, adaptations must be consistent with economic development, they must be environmentally and socially sustainable over time, and they must be equitable (that is, not have significantly deleterious effects on disadvantaged groups) (Munasinhge, 2000).

In most cases, human settlements have designed into them the ability to withstand most of the consequences of some environmental variability. In most regions, climate change would change the probability of certain weather conditions. The only effect for which average change would be important is sea-level rise, under which there could be increased risk of inundation of coastal settlements from average (higher) sea levels. Human settlements for the most part would have to adapt to more or less frequent or intense rain conditions or more or less frequent mild winters and hot summers, although individual days� weather may be well within the range of current weather variability and thus not require exceptionally costly adaptation measures. The larger, more costly impacts of climate change on human settlements would occur through increased (or decreased) probability of extreme weather events that overwhelm the designed resiliency of human systems.

Much of the management of urban centers as well as the governance structures that direct and oversee them are related to reducing environmental hazards, including those posed by extreme weather events and other natural hazards. Most regulations and management practices related to buildings, land use, waste management, and transportation have important environmental aspects. So too do most public and private investments in infrastructure. A significant part of health care and emergency services exists to limit the health impacts of environmental hazards. Local capacity to limit environmental hazards or their health consequences in any settlement generally implies local capacity to adapt to climate change, unless adaptation implies particularly expensive infrastructure investment.

An increasing number of urban centers are developing more comprehensive plans to manage the environmental implications of urban development. Many techniques can contribute to better environmental planning and management including: market-based tools for pollution control, demand management and waste reduction, mixed-use zoning and transport planning (with appropriate provision for pedestrians and cyclists), environmental impact assessments, capacity studies, strategic environmental plans, environmental audit procedures, and state-of-the-environment reports (Haughton, 1999). Many cities have used a combination of these techniques in developing �Local Agenda 21s.� Many Local Agenda 21s deal with a list of urban problems that could closely interact with climate change in the future. Examples of these problems include (WRI, 1996; Velasquez, 1998):

• Transport and road infrastructure systems that are inappropriate to the settlement�s topography (could be damaged by landslides or flooding with climate change)
• Dwellings that are located in high-risk locations for floods, landslides, air and water pollution, or disease (vulnerable to flood or landslides; disease vectors more likely)
• Industrial contamination of rivers, lakes, wetlands, or coastal zones (vulnerable to flooding)
• Degradation of landscape (interacts with climate change to produce flash floods or desertification)
• Shortage of green spaces and public recreation areas (enhanced heat island effects)
• Lack of education, training, or effective institutional cooperation in environmental management (lack of adaptive capacity).

The following generic lessons from Curitiba, Brazil�which come from the context of �sustainable cities� under existing conditions�may be applicable to future adaptation responses (Rabinovitch, 1998):

• Top priority should be given to public transportation rather than to automobiles and other light-duty vehicles, and to pedestrians and cyclists rather than to motorized vehicles. This reduces air pollution and some other forms of pollution. It was noted that some alternative fuels such as hydrogen are particularly attractive for reducing local air quality problems, as well as mitigating GHG emissions.
• There can be an action plan for each set of urban problems, but solutions within a city are connected, not isolated.
• Action plans must be participatory, with partnerships involving all responsible parties [government, private sector, nongovernmental organizations (NGOs), individuals].
• Creativity can substitute for financial resources (labor-intensive and creative ideas can substitute for capital).
• Even during rapid demographic growth, physical expansion can be guided by integrated road planning, investment in public transportation, and enforcement of appropriate land-use legislation.
• Technological solutions and standards for everything from public transit to recycling should be chosen on the basis of affordability (cost-effectiveness, combined with sensitivity to total cost).
• Public information and awareness are essential.

The most effective pathways for adaptation that result in sustainable development are likely to arise out of an informed evolution of existing institutions. Several authors emphasize the importance of the support and will of local public officials in developing successful environmental solutions (e.g., Gilbert et al., 1996: Foronda, 1998). Others emphasize the need in traditional societies to build from and integrate modern techniques into traditional management practices and kinship and community networks, to effectively collect and disseminate data needed for assessing impacts, to open public participation processes for formulating policy, and to provide a process for strengthening financial, legal, institutional, and technical elements (Huang, 1997).

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