In Latin America, the region with the largest urbanization rate, a large spectrum of urban settlements has been established at different elevations (from sea level to mountain ranges exceeding 3,000 m). These locations have a wide variety of geographic and topographic characteristics (see Figure 6-1). Because weather and climate events already are affecting environmental conditions, climate change may be expected to have a host of direct and indirect effects on human settlements, even where urban migration is not a factor. However, such migration is significant in some countries of the region. In fact, large groups of people migrate internally and regionally from rural, drought-prone areas (Ezcurra, 1990) or poverty stricken communities (Canziani, 1996) to modern, well-developed cities. Unemployment rates indicate that this tendency will continue, particularly because cities and urban/industrial/commercial nuclei in Latin America offer better opportunities for employment than do those in other regions. Such cities may become the kernels of Latin American megalopolises, attracting people from less-developed neighboring countries as well as from within. Population displacements are likely to have serious socioeconomic and cultural as well as health implications (also see Section 6.3.5). More than one poverty belt, such as those in the metropolitan areas of some Latin American cities, may arise around a single city.
Latin American cities already suffer from the impacts of sea-level rise, adverse weather, and extreme climate conditions (e.g., floods, flash floods, windstorms, landslides, and cold and heat outbreaks). They also suffer from indirect effects through impacts on other sectors, such as water supply, energy distribution, transportation, agriculture, and sanitation services. Thresholds beyond which impacts escalate quickly are unique to local situations and tend to depend on the degree of preparedness for adaptive response (e.g., warning and alert systems and procedures; traffic rerouting procedures; flexible welfare systems) (IPCC 1996, WG II, Section 12.2).
Global warming can be expected to further affect the availability of water resources and biomass (for charcoal and fuel production), both of which are important energy sources in many Latin American countries. Water and biomass resources already are under stress in many of these areas as a result of rising demand, which will increase because of the urban migration trend. The increasing urban population in the region also has generated difficulties in providing water of adequate quality to urban residents. In most cities, piped drinking water and sewage services are not available to everyone. In the Buenos Aires metropolitan area, about 55% of the population obtains its drinking water from underground sources-some of which have serious levels of contamination from industrial waste dumps, agrochemicals, and, particularly, precarious sewage systems consisting of pozos negros (excreta and fecal holes) (Gonz�lez, 1990; De Filippi et al., 1994).
In mountain regions, hundreds of thousands of people live in precarious settlements on potentially unstable hillsides that are especially vulnerable to climatic impacts. In recent decades, hundreds of people have been killed or seriously injured and thousands left homeless by landslides in Rio de Janeiro, Guatemala City, Medell�n, Mendoza, Mexico City, Santos, and Sao Paulo (WHO Commission on Human Health and Environment, 1992; Aguilar and Sanchez, 1993), as well as Caracas (Hardoy et al., 1992). Shantytowns (barriadas, favelas, or villas miseria) surrounding large cities in the region sometimes are established in the drainage valleys of rivers and streams-where flooding frequency already is increasing as a result of climatic variability (Canziani, 1996) and might be exacerbated as a result of global warming. Flooding and landslides have adverse effects on the welfare and health conditions of poorer communities.
Nonclimatic effects may be more important than climate change. Local environmental and socioeconomic situations are changing rapidly; the living standards of millions of people in Latin America are lower now than they were in the early 1970s. Poverty has become an increasingly urban phenomenon in recent decades. Migrants tend to live in informal, peri-urban settlements with serious infrastructure problems-ranging from unhealthy environments and water supplies and lack of sewage systems to difficult access to energy, transportation, communications, and even decent shelter. Some informal settlements around large Latin American cities, especially around the capital cities, are homes for many hundreds of thousands of people, leading to impacts on human health (see Section 6.3.5).
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