|Working Group II: Impacts, Adaptation and Vulnerability|
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7.2. State of Knowledge Regarding Climate Change Impacts on Human Populations
The TAR differs from the two previous assessments in that the literature has begun to quantify several of the climate-related risks to human settlements that previously were identified only in qualitative terms. Additional attention and research has been devoted to adaptation mechanisms that provide resistance to climate-related impacts and ability to recover from them. Several economic and social trends that are specific to development and change in human settlements will interact with the effects of climate change in the future and may exacerbate or mitigate the effects of climate change alone.7.2.1. Nonclimate Trends Affecting Vulnerability to Climate
Population growth: Except for parts of Europe and the Russian Federation, most regions are expected to experience population growth. Although Special Report on Emission Scenarios (SRES) marker scenarios in Chapter 3 do not span the entire realm of possibilities and have not been assigned probabilities, they do show that under plausible conditions, future regional population growth rates will range from modest (Europe and North America, where projected rates are just above or below replacement) to 3% or more (portions of Latin America and especially Africa).
Urbanization (proportion of population living in urban areas) is expected to continue, especially in the developing world. Close to half of the world’s population now lives in urban areas, and the likely trend toward a more urban world means that the impacts of climate change on human settlements, if they occur, increasingly will affect urban populations. The most rapid urban growth rates are occurring in the developing world, where urban populations are estimated to be growing at 2.7% yr-1, compared to 0.5% yr-1 in more developed regions (UN, 2000). There also is a growing concentration of population in cities with more than 1 million inhabitants. The number of such cities worldwide grew from 80 in 1950 to more than 300 by 1990 and is expected to exceed 500 by 2010 (UNCHS, 1996; UN, 2000). Most cities with more than 1 million inhabitants are now in the developing world, although—as in more developed regions—they are heavily concentrated in its largest economies (UNCHS, 1996). Cities also are reaching unprecedented sizes. However, the future world may be less dominated by “megacities” (cities of more than 10 million population) than previously predicted. Megacities are likely to be smaller than previously predicted and still contain a small proportion of the world’s population—less than 4% in 1990, the last date for which there is census data for most nations (UNCHS, 1996; UN, 2000). Most of the world’s urban population live in the 40,000–50,000 urban centers with fewer than 1 million inhabitants (UNCHS, 1996). In 1990, cities with more than 1 million inhabitants had just more than one-third of the world’s urban population and just more than one-seventh of its total population (UN, 2000). Urban population increases were particularly sharp in the second half of the 20th century in some regions where urbanization had been held down by policy, such as China (Institute of Land Development and Regional Economy, State Planning Committee, 1998). Trends toward urbanization mean that the impacts of climate change on human settlements in most countries, if they occur, increasingly will affect urban populations, not rural or traditional settlements.
Poverty is becoming increasingly urbanized, as a growing proportion of the population suffering from absolute poverty lives in urban areas. In more developed regions and in much of Latin America (e.g., 36% in Latin America—ECLAC, 2000), poverty is concentrated in urban areas. In other regions, the number of rural poor still exceeds the number of urban poor, although the proportion of absolute poor living in urban areas is growing. In addition, the scale and depth of urban poverty frequently is underestimated, in part because official income-based poverty lines are set too low in relation to the cost of living (or the income needed to avoid deprivation) in most urban centers and in part because no provision is made to include housing conditions, access to services, assets, and aspects of social exclusion within most government poverty definitions (Satterthwaite 1997). Where it occurs, urban poverty reduces the capacity of urban populations to take action to adapt to climate change; poverty also may exacerbate many of its effects.
Market systems and privatization increasingly are being used to provide new infrastructure and maintain older systems (World Bank, 1994), giving government a smaller direct role in providing infrastructure for energy, environmental residuals, communications, and other key urban services. Governments that are trying to adapt settlements to climate change increasingly may have to work indirectly through markets and regulation of private providers to adapt buildings and infrastructure to climate change.
Energy systems are changing in some places, helping to determine which mechanisms are salient in human settlements impacts (Schipper and Meyers, 1992; Hall et al., 1993; World Energy Council, 1993a):
Transportation activity and associated energy consumption are growing very rapidly in nearly every region. Except for economies in transition, the amount of goods traveling by road increased between 1990 and 1996. The increases were 50% or more, and total paved roadways worldwide rose from 39 to 46% of the total (World Bank, 1999). In all Organisation for Economic Cooperation and Development (OECD) countries, car ownership continues to rise steadily, but much of the growth in vehicle ownership is expected in developing countries and transition economies—especially in east Asia and the Pacific, and especially in urban areas (World Resources Institute, 1996). This trend contributes to local air pollution (which can be exacerbated by warm weather episodes) and to greenhouse gas (GHG) emissions.
A poleward intensification of agricultural, forestry, and mining activities is occurring, resulting in increased population and intensified settlement patterns in Canada’s mid-north, for example, and even in arctic areas. Climate change could profoundly affect settlements in these regions, if climate change is greater toward the poles (Cohen, 1997). For example, some arctic and subarctic activities such as mining depend on snow roads, which would have to be replaced with more conventional transport.
Impact of urban wealth: Many of the worst city-level problems—such as sanitation and water supply—have been addressed in high-income cities such as those in Europe and North America, but not in many developing world cities (WHO, 1992; Hardoy et al., 2000; McGranahan and Satterthwaite, 2000). A wealthy city can more easily afford the public finance and administration required to regulate more perceptible forms of pollution than a poor one. However, although the ambient environment of high-income cities may be more benign in terms of health impacts of pollution, these cities exert a far greater toll on the regional and global environment (UNCHS, 1996).
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