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Chapter 2: Regional Perspectives

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Latin America and the Caribbean

Major Environmental Concerns

[ Land | Forest | Biodiversity | Water | Marine and Coastal Environments | Urban and Industrial Environments ]

The Latin America and Caribbean (LAC) region encompasses countries with great economic, social, and environmental diversity. It is not easy to summarize concerns that are common to large and multi-ecosystem nations such as Brazil, the Andean States, and the Caribbean Island States. Yet the region also has a number of common environmental characteristics that distinguish it from other regions of the world. These include immense hydrological systems, such as the Amazon, Orinoco, and Rio de la Plata; a global importance as a carbon sink, particularly in the Amazon Basin; and unique and vast biological diversity and ecosystem heterogeneity.

In addition, the region has other features common to many of its countries. These include high proportions of urban populations, high ethnic diversity coupled with the existence of native indigenous populations, rapidly expanding agricultural frontiers, national economies that are being or have been subjected to structural adjustment programmes, a changing role for the State and its functions, an emerging active civil society, and increasing inequality and poverty. The common and overlapping environmental concerns in the LAC region have been grouped and summarized by the Commission on Development and Environment for LAC (LAC CDE, 1992) under the following themes:

  • land use,
  • forest resources,
  • ecosystems and biological patrimony,
  • water resources,
  • sea and shoreline resources,
  • the environment in human settlements,
  • energy,
  • non-energy mineral resources, and
  • industry.

Land

The LAC region includes 23 per cent of the world's potential arable land, 12 per cent of current cropland, and 17 per cent of all pastures (Gallopin et al., 1991). In contrast with other regions, LAC still maintains a high percentage of natural ecosystems that have been little disturbed by human activities, particularly in the Amazon region and the southern tip of South America. These ecosystems are currently being degraded at a high rate, however, particularly at their margins.

Some 306 million hectares (72.7 per cent) of the agriculturally used drylands in South America (that is, irrigated lands, rainfed cropland, and range-lands) suffer from moderate to extreme degradation (UNEP, 1991). (See Figure 2.15.) And some 47 per cent of the soils in grazing lands have lost their fertility (LAC CDE, 1992). This land degradation includes erosion and soil degradation in hillsides and mountain areas and in tropical pasturelands, desertification brought on by overgrazing, and salinization and alkalization of irrigated soils.

The acceleration of the erosion process in LAC is mainly due to the expansion of the agricultural frontier and the overuse or unsustainable use of land for cultivation or grazing and deforestation. Some of the best land is also being lost through urban expansion. Much of the unsustainable use of the land, particularly the overgrazing, is due to mismanagement. The expansion of the agricultural frontier, especially in the Andean highlands, has led to the use of fields whose altitude and gradient render them particularly fragile. In other areas, the overuse of land, especially in the form of single-crop farming, has damaged the soil structure and left land vulnerable during periods when it lacks plant cover (Gligo, 1995).

In the Argentine Patagonia, for example, the introduction of unsustainable numbers of sheep along with inappropriate management policies has resulted in changes in pastureland composition and desertification. This is causing the loss of approximately 1,000 square kilometres a year (LAC CDE, 1992), with 35 per cent of pastureland having been transformed into desert (Winograd, 1995). Other arid and semi-arid zones in the region also suffer from desertification, including Mexico, where water erosion alone affects 85 per cent of the territory (Gligo, 1995).

For the region to maintain its current food self-sufficiency and expand export crops to earn badly needed foreign exchange, countries will need to farm more intensively and increase the land under agriculture. Intensification will lead to increasing inputs in agriculture, which will in turn have important environmental implications (pollution, use of pesticides and fertilizer, and so on). The potential consequence of the expansion of agricultural land is that forests in the region will diminish and more of the marginal lands will become degraded.

Forests

The LAC region has both the world's largest unfragmented tropical forests (in Amazonia) and some of the most fragmented and most endangered tropical forests (such as the Mata Atlantica). At the end of 1990, some 28 per cent of the world's total forested area and 52 per cent of its tropical forest were in Latin America and the Caribbean. In 1990, these forests covered 968 million hectares, or 48 per cent of the land in the region (FAO, 1993).

The accelerated transformation of tropical and other forests into permanent pasture and other forms of land use constitutes a critical environmental problem for the region. Not only is the extent of the land involved immense, but also effects on ecosystems are practically irreversible (Winograd, 1995).

As with land degradation, deforestation is mainly due to the expansion of the agricultural frontier, which is in turn the outcome of a number of factors. Among these are the displacement of peasant farmers from traditional farming areas, large-scale settlement programmes such as in Rondônia in Brazil, and the use of tax exemptions to promote the expansion of livestock raising activities in the Amazon. In addition, commercial logging, collection of firewood for household use, and road construction have all led to the unsustainable exploitation of the region's forests (Gligo, 1995).

Forest cover in the region declined from 992 million hectares in 1980 to 918 million hectares in 1990, yielding an annual deforestation rate of 0.8 per cent over this period. Average annual deforestation rose from 5.4 million hectares in 1970 to 7.4 million hectares in 1990 (FAO, 1993). (See Figure 2.16.)

Tropical deforestation was also quite rapid. Its rate increased from 5.6 per cent over the period 1960-70 to 7.4 per cent for the period 1980-90 (FAO, 1993). The tropical forests of the Pacific coast of Central America once covered 550,000 square kilometres, but now less than 2 per cent is intact. However, some countries, such as Costa Rica, have preserved and protected some of their forests under national park or reserve status. Similarly, the Atlantic forest of Brazil (also marginally present in Paraguay and Argentina) only maintains 4 per cent of its original 1 million square kilometres as pristine forests, and an additional 6 per cent as secondary forests (UNEP, 1995b). The rapid loss of highly diverse native forests is of particular concern, because they are often replaced by induced pastures or by monocultures of exotic timber species. Most of the endangered tropical plants in Brazil (65 per cent) are found in this highly endangered tropical forest ecosystem (CDEA, 1992).

Most of the primeval forests of the Caribbean were stripped in the early colonial period. Since then, an increasing problem has been the introduction of exotic species into successional forests and scrubs. This is a problem of both forestry management and biodiversity conservation.

While deforestation figures are disputed by many national Governments, studies indicate that the annual increase in deforestation in the Amazon Basin countries increased until the late 1980s; the most serious loss was in Rondônia, where the rate increased 128 per cent between 1980 and 1984 and 51 per cent in 1985 alone (LAC CDE, 1992). The situation in Rondônia has improved considerably in the recent years since Brazil abolished the subsidies, tax incentives, and special credits that encouraged deforestation. The private project of Precious Woods in the Brazilian Amazon as well as other initiatives in the region are also helping address the situation. Nevertheless, deforestation in the region continues as the agricultural frontier expands, albeit at a lower rate.

Biodiversity

Latin America and the Caribbean are characterized by their high species and ecosystem diversity. Five of the 10 richest countries in the world in terms of terrestrial plant and animal species, the so-called ecological megadiversity countries, are in Latin America: Brazil, Colombia, Ecuador, Mexico, and Peru (LAC CDE, 1992). The region contains 40 per cent of the plant and animal species of the world's tropical forests and 36 per cent of the main food and industrial cultivated species (LAC CDE, 1992). Colombia alone, with 0.77 per cent of the world's area, contains 10 per cent of the world's animal and plant species (McNeely et al., 1990).

The region's biota, in addition to being enormously diversified, provide important opportunities for economic development. This heritage, which has medicinal, industrial, and food potential, can generate sustainable benefits for the local population now and into the future (LAC CDE, 1992). In the Amazon, about 1,000 known plant species have economic potential, and at least 300 species have forestry potential (LAC CDE, 1992). This does not even scratch the surface of the potential of unknown and uncatalogued flora and fauna. In 1960, the discovery of two varieties of tomato in Peru provided economic benefits to the industry estimated at US$5 million a year due to improvement in pigment and final product (LAC CDE, 1992). The potential of the region in terms of biodiversity and genetic resources is enormous not only for agriculture, but also for the ever-expanding pharmaceutical industry.

This vital biological reserve, which is of major importance both to the region and the world, is highly threatened. (See Figure 2.17 a, b.) In LAC, as elsewhere in the world, habitat loss is the biggest threat to biodiversity. Many of the threatened species and habitats are located in areas such as high-mountain habitats, tropical drylands, desert ecosystems, and cloud forests as well as tropical moist forests. Not only has Latin America lost more than 7 per cent of its tropical forests during the 1980s, but its savannah-grasslands are also under continuous threat (FAO, 1993).

Despite the importance of habitat loss other than in forests, most research on biodiversity loss still concentrates on forest ecosystems. General estimates indicate that at current rates, the conversion and deforestation of tropical forests and dry forests may wipe out 100,000-450,000 species within the next 40 years (Winograd, 1995). Of these, some 5,000-20,000 species are estimated to be plants and some 1,000-5,000 vertebrate species according to calculations based on recent studies (May, 1989; Western and Pearl, 1989). Most of the species that are becoming extinct have not been inventoried or described adequately.

In addition to habitat loss, habitat fragmentation is also a major concern. The annual rate of habitat fragmentation in the Brazilian Amazonia, for example, is thought to be 2.5 times higher than the rate of deforestation. The effects of this loss on plant and animal species diversity is of critical concern to the region because habitat fragmentation has not been accompanied by adequate concern for the planning and conservation of biological corridors.

Biodiversity conservation in the densely populated islands of the Caribbean is a special problem because of the extremely small area of some local habitats, the high incidence of endemism throughout the islands, and the high regional vulnerability to natural disasters such as hurricanes, tsunamis, volcanoes, and earthquakes. The highly diverse marine ecosystems of the wider Caribbean and the rich biodiversity housed within these ecosystems are also under considerable stress. (See Box 2.3and Marine and Coastal Environments below.)

Water

Some 13 per cent of the world's continental waters are found in Latin America and the Caribbean, but the distribution within the region is highly variable. (See Table 2.8.) Many areas have great difficulties meeting their water needs, including northern Mexico, north-eastern Brazil, and southern Chile. Two thirds of the territory of the LAC region is arid or semi-arid including large portions of Argentina, Chile, Bolivia, Peru, north-eastern Brazil, Ecuador, Colombia, and central and northern Mexico. Approximately 334 million hectares in South America are classified as semi-arid, arid, or hyper-arid (UNEP, 1992; SEDESOL, 1993).

Furthermore, many areas that are classified as subhumid present a marked water deficit during the seasonally dry periods. In other areas, the hydrological cycle is so variable that it generates a ruinous sequence of prolonged droughts and destructive floods that make agriculture impractical (LAC CDE, 1992).

Water quality problems that are common to the whole region include toxic contamination from industry, waste disposal, and eutrophication from human sewage. Bacterial pollution of water supplies in the region is a continuing problem with adverse effects on human health. The major concerns caused by high bacterial and organic loads range from poor-quality drinking water, eutrophication, and disappearance of aquatic life to food contamination and the prevalence of waterborne diseases (UNEP, 1991).

Forest cutting also has a negative effect on the production and regulation of water flows, while the ensuing soil erosion increases the amount of suspended sediments, which affects the quality of the water resources and the functioning of dams and reservoirs.

The rivers of this region are being polluted by a number of different sources, but the most important ones are industrial and urban wastewaters from large industrial cities, wastewater from mining industries, and agricultural runoff. As a result, many of the region's water resources are today chemically and biologically contaminated. Several rivers in Colombia-among them, the Medellín and the Bogotá-are as good as biologically dead (totally lacking dissolved oxygen). Waters in the Sogamosa Valley and in the Magdalena, Dagua, and Nechi rivers have been contaminated by industry and mining.

Large quantities of agricultural contaminants are disposed of in streams flowing into the Caribbean Sea, where there is clear evidence of elevated levels of phosphorous, nitrates, potassium, pesticides such as DDT, and highly organic effluents (LAC CDE, 1992). These elevated levels of pollutant concentrations are caused by the indiscriminate discharge of highly pollutant-loaded effluents into the region's water bodies. Finally, the transformation of coca leaves into basic cocaine paste is heavily polluting some small tributaries of the Marañon and Amazon rivers in Bolivia, Colombia, and Peru.

In the wider Caribbean, many coastal aquifers are contaminated by pollutants or salt-water intrusions due to overextraction of ground-water reserves. In Venezuela, for example, the overuse of aquifers has already resulted in widespread salt-water intrusion (UNEP/SCOPE, 1993). This limits future uses of ground water for development and also affects extensive areas of near-shore habitats where fresh water springs emerging from these ground-water reserves have previously nourished reef areas.

In the LAC region, continental waters are crucially important for agricultural production. The arid conditions and seasonal water deficiencies that characterize large parts of the region have led to the development of large irrigated agricultural areas that generate a high proportion of the region's agricultural product in artificially transformed ecosystems. The irrigated areas have grave environmental problems, including soil salinization, alkalization, and water pollution from organic and chemical sources. Organic pollution in the region originates mostly from urban and agro-industrial wastewater that is used for irrigation. The chemical pollution is the result of using pesticides with a long residual life, as well as industrial and mining wastewater.

The great hydroelectric dams in the region, while important for electricity generation, have transformed large fluvial systems into chained lakes, such as the upper and middle Paraná system in Brazil, Paraguay, and Argentina. These large waterworks have generated a number of substantial environmental disruptions, including the erection of often unsurpassable obstacles for fish, the explosive growth of floating aquatic plants, and the eutrophication of dam reservoirs. The large development projects that connect watersheds and improve continental navigation networks, such as the Hidrovia Project in the Paraná-Paraguay fluvial system, also affect some of the most important wetlands of the region, like the Pantanal.

Marine and Coastal Environments

Twenty-five per cent of the people in the region live in coastal areas (and nearly 100 per cent in the smaller islands of the Caribbean), and marine and coastal resources are seen as an important part of the development pattern of numerous countries (Winograd, 1995). The total population of coastal dwellers in the wider Caribbean is estimated at 50 million, which is expected to increase to some 60 million by the year 2000 (UNEP, 1994).

According to some estimates, 26 per cent of the LAC coastlines are under high potential threat of degradation, and a further 24 per cent are under moderate potential threat due to coastal development (including tourism and infrastructure works); discharge of sediments, wastes, and contaminants from urban and industrial areas; sewage; industrial pollution; and oil spills (WRI/UNEP/UNDP/WB, 1996). (See Figure 2.18.) Coastal habitats within the Caribbean region, an area with a high level of biodiversity, are also under stress from development, pollution, sedimentation, and dredging. (See Box 2.3.)

Box 2.3.

Coastal Pollution and Biodiversity in the Wider Caribbean Region

The unique, diverse, and threatened environment of the Caribbean region warrants special attention. This is particularly so given the vulnerability of the region s ecosystem to climate change and sea level changes, as well as natural disasters. The prominent tourist industry depends heavily on maintaining this unique environment and its rich biodiversity. There is an urgent need to address the threatened marine and coastal areas of the region in a comprehensive and multisectoral manner, dealing with complete watershed and coastal areas.

Marine and Coastal Environments

Marine and coastal erosion and pollution in the wider Caribbean region are reaching a critical state. Industrial waste, mining runoff, domestic sewage, heavy river sediment loads, and tourism are all increasing stress on marine and coastal environments. The impacts include deterioration of the region s biodiversity, declining fish stocks, and polluted beaches.

The major source of coastal and marine pollution is the discharge of untreated waste and sewage from human settlements, agricultural runoff, and industrial activities, especially the oil and tourist industries. According to the Pan American Health Organisation (PAHO), only 10 per cent of the sewage generated in Central America and the Caribbean Island countries was properly treated in the early 1980s (Archer, 1984). A more recent study by PAHO showed that in the 11 Caribbean Common Market (CARICOM) countries, the percentage of the population served by sewage systems varied between 2 and 16 per cent (Vulgman, 1992). With the population of coastal dwellers in the wider Caribbean region estimated to reach 60-65 million by 2000 (UNEP, 1994), pollution impacts are likely to increase.

Mining operations are an important source of particulate materials entering the coastal areas of the wider Caribbean region. The mining of bauxite is particularly significant for the economies of Jamaica, Suriname, and Guyana, and to a lesser extent for the Dominican Republic and Haiti. Ore mining for the production of nickel oxide in Cuba and the Dominican Republic is another source of contaminants. Few of these operations have treatment and recycling facilities. Much of the waste from mining ends up in the marine and coastal environments of the region, either directly or through rivers.

The oil industry is the largest industrial polluter in the wider Caribbean region. Oil refineries contribute approximately 70 per cent of the total biological oxygen demand load and more than 80 per cent of the total oil and grease discharged from industrial point sources in the region. Other industries that produce large pollutant loads in the region are sugar factories and distilleries, food processing plants, beverage manufacturers, pulp and paper plants, and chemical plants.

The considerable number of tourists visiting resort areas of the wider Caribbean region year-round also has implications for the region s environment. Between 1983 and 1993, the insular Caribbean alone attracted an average of 11 million visitors a year. In addition, daily visitors from cruise vessels in the region numbered some 8 million in 1991-92. (Simmons et al., 1994).

To respond to the increasing influx of tourists, hotels and recreational facilities are still being built throughout the region, often in locations lacking municipal sewage systems. Because much of the current and projected income of the Caribbean comes from tourism, the maintenance of a unique environment is of paramount importance for the sustained economic development and growth of the region.

The transport of eroded soils to the sea by rivers has led to the increased turbidity of coastal waters, placing an increasing amount of stress on coastal ecosystems such as coral reefs, particularly along the Caribbean coast of Panama, Costa Rica, and Nicaragua (UNEP, 1994). Most of the suspended and dissolved materials carried by these rivers are derived from natural geochemical processes. However, human activities significantly contribute to this load through the erosion of river basin watersheds caused by deforestation, urbanization, agriculture, industry, and the discharge of a variety of pollutants into these waters.

Biodiversity

The Caribbean region contains a rich variety of complex ecosystems with many endemic species. Along the coast of Belize, for example, lies the second largest coral reef in the world and the longest in the northern hemisphere, stretching some 220 kilometres. In many parts of the region, however, coral reefs are severely damaged or are in danger of being lost. For example, the coral cover on the reefs along the north coast of Jamaica has declined from 52 percent to 3 percent over the period from the late 1970s to early 1990s (Hughes, 1994). The Caribbean Sea itself is being subjected to severe environmental stresses, from increased opacity from suspended sediments to marine debris and overharvesting of key commercial species such as lobster, shrimp, grouper, conch, and gamefish.

Habitat destruction due to aggressive coastal zone development, particularly to serve the expanding tourist industry, seems to be the main cause of pressure on the region s biodiversity. Overexploitation and harvesting of species, coral reef and seagrass degradation, and mangrove deforestation (for large-scale land reclamation schemes, in particular) also contribute to the pressure, as do various sources of pollution.

The decades-long efforts to preserve, protect, and restore the five species of endangered and threatened sea turtles in the Caribbean illustrate the difficulty and complexity of the region's environmental problems. The remaining sea turtle populations are being put under enormous stress by the destruction of nesting beaches during coastal development; the destruction of eggs and nests by harvesting; hunting of adults and high mortality as by-catch of fishing nets and trawlers; poisoning by toxic chemicals; ingestion and entanglement in plastic debris in the open ocean; and the destruction of feeding areas by trawling, dredging, and coastal pollution.

Despite ongoing efforts, sea turtle populations are declining throughout most of the region. In some areas, the trends are dramatic and are likely to be irreversible during our lifetimes. According to IUCN-the World Conservation Union-persistent overexploitation, especially of adult females on nesting beaches, and the widespread collection of eggs has resulted in five turtle species in the region being classified as "endangered" and a sixth classified as "vulnerable" (IUCN, 1993).

References

Archer, A.B. 1984. Land Based Sources of Pollution in Coastal, Marine and Land Areas of the CARICOM States. UNEP/CARICOM/PAHO Project for the Protection of the Coastal and Marine Environment of the Caribbean Islands.

Hughes, T.P. 1994. Catastrophes, phase shifts and large scale degradation of a Caribbean coral reef. Science 265:1547-1551.

IUCN. 1993. IUCN Red List of Threatened Animals. B. Groombridge (ed). World Conservation Union (IUCN), Gland, Switzerland, and World Conservation Monitoring Centre, Cambridge, UK.

Simmons and Associates. 1994. The impact of tourism on the marine environment of the Caribbean; with special reference to cruise and other types of marine based tourism. Prepared for the Caribbean Tourism Organisation, Barbados.

UNEP. 1994. Regional Overview of Land Based Sources of Pollution in the Wider Caribbean Region. CEP Technical Report No. 33, UNEP Caribbean Environment Programme. Kingston.

Vulgman, A.A. 1992. CEHI/PAHO Assessment of Operational Status of Wastewater Treatment Plants in the Caribbean.

The discharge is concentrated in zones with high economic activity, such as Cartagena, Coatza Coalcos, Havana, and Kingston, where the volume of the discharge exceeds the ecosystem's absorptive capacity. This damage has had an adverse impact on beaches, coral reefs, and seagrass beds. Few Latin American cities have effective waste and sewage treatment facilities or water treatment plants (Gligo, 1995). Industrial and hazardous wastes from the region as a whole flow straight into the ocean, while the river basins act as catchment areas for agricultural wastes, which then drain into the sea.

In the wider Caribbean, oil is a significant marine contaminant, damaging the important tourist industry. The specific threats include loading, unloading, and transporting petroleum products; the cleaning of tanks; and the accidents, spills, and fires that often accompany these activities (LAC CDE, 1992). Many beaches in the Caribbean now have average tar levels 10 times higher than that estimated to adversely affect the use of beaches by tourists-levels at which beaches become virtually unusable for recreation (GESAMP, 1990).

More than 50 per cent of the mangroves in the region have been degraded by pollution and infrastructure services or have been altered by forestry activities and the conversion to agriculture or aquaculture; this is of particular concern to most of the Caribbean region (WRI/UNEP/UNDP/WB, 1996). Mangroves provide a variety of habitats that serve as nurseries for great numbers of reef and coastal species, and as critical reserves for migratory birds under increasing stress at both ends of their migration routes. As a combined result of these stresses as well as overfishing, the catch of commercial species such as shrimp, grouper, Caribbean lobster, and bass in semi-tropical areas is diminishing (Winograd, 1995).

Atmosphere

Although Latin America and the Caribbean produce only 14.8 per cent of the world's greenhouse gas emissions and a similarly low proportion of chlorofluorocarbons (Winograd, 1995), the region will bear a disproportionate portion of the consequences of climatic and atmospheric change.

The southern latitudes of South America are the areas closest to the seasonal ozone hole that opens up over Antarctica each spring and summer. As a result, Argentina, Brazil, Chile, Paraguay, and Uruguay experience the effects of increased ultraviolet-B radiation due to ozone depletion more acutely than any other inhabited region on earth (UNEP, 1995c).

At the same time, sea level rise will affect the Caribbean countries as well as low-lying coastal regions of LAC. Because of regional differences in regimes of storm surges, the increase of flooding risk due to sea level rise is greater than average for the coasts of the Caribbean and other small island States (IPCC, 1994).

In addition, the effect of natural hazards such as flooding, drought, and hurricanes could be magnified by global climatic change. A potential change in the frequency of occurrence of natural, large-scale anomalies in atmospheric circulation, such as tropical hurricanes and El Niño events, is of particular relevance in a region that is already naturally subject to these contingencies. These changes are likely to affect the small island States of the Caribbean disproportionately.

Urban and Industrial Environments

Cities in Latin America, which are home to 78 per cent of the region's population (UN, 1995a), are particularly vulnerable to environmental problems such as urban air pollution, water pollution, disposal of solid and liquid wastes, and industrial contamination. Domestic and industrial discharges in urban areas contaminate air, land, and water with nutrients and toxins. In turn, degraded air, land, and water harm flora and fauna and pose health risks to city dwellers. Although most of the megacities are affected in similar ways, data on urban environmental conditions are available mainly from a few large cities such as Mexico City, São Paulo, and Santiago. Much of this pollution stems from economic growth and industrialization, which have been highly concentrated in the large cities of the region, rather than from urbanization itself.

In the last decades, rural abandonment and poverty have accelerated the growth of urban areas. (See Figure 2.19.) Many of the cities in LAC were not conceived or planned for the current demographic densities. As a result, the sprawling megacities have generated peripheral belts of fragile human settlements, usually located in environmentally unsuitable areas such as hill slopes or floodable grounds. People living in these areas are particularly vulnerable to disasters and health hazards. Additionally, some of the larger cities, such as Mexico City and Santiago, are located in valleys and surrounded by mountain ranges, which exacerbate their urban pollution problems and make them inappropriate for further industrialization and urban expansion.

Air pollution is a constant fact of life for 81 million urban residents of Latin America, leading to an estimated 2.3 million cases of chronic respiratory illness every year among children, to 105,000 cases of chronic bronchitis among the elderly, and to nearly 65 million lost workdays (LAC CDE, 1992). Mexico City, São Paulo, and Santiago all have very high pollution indexes. Buenos Aires, Bogotá, Rio de Janeiro, and Caracas are not free of this problem either, although due to their geographical locations and climatic conditions they are less seriously affected (ECLAC, 1993a).

Mexico City has probably experienced one of the worst air pollution problems in the world. The weather and topography greatly hamper dispersal of the enormous volumes of pollutants that are emitted into the air, especially during the dry season (Gligo, 1995). World Health Organization guidelines for sulphur dioxide, suspended particulate matter, and carbon monoxide were all regularly exceeded in the city during the 1970s and 1980s (UNEP and WHO, 1992), although there has been a marked improvement over the past five years. According to estimates in 1992, suspended particulate matter in Mexico City from vehicles and other sources increased mortality rates about 0.038 per cent, and thus contributed to 6,400 deaths (Margulis, 1992). In addition, it was estimated that elevated ozone concentration contributed to the loss of around 6.4 million workdays a year, and that 29 per cent of children had unhealthy blood lead levels (Margulis, 1992). Similar patterns have been observed in many other cities of the region.

Two main factors are causing an increase in urban air pollution in the region: the mounting number of motor vehicles in use, and the expansion of industrial activity. Mexico City alone has more than 4.2 million motor vehicles (Cevalos, 1996), while in Santiago, the number of motor vehicles has tripled over the past 15 years (ECLAC, 1991). The use of motor vehicles produces more air pollution than any other single human activity, with an estimated 80-90 per cent of lead in ambient air coming from the combustion of leaded gasoline, despite the fact that unleaded gasoline has been introduced in most Latin American countries (WRI/UNEP/UNDP/WB, 1996). The growth of industrial activity has been especially marked in the larger countries and major cities. Following the slowdown in the 1980s due to economic stagnation, industrial activities are once again picking up (ECLAC, 1996), and with them, environmental pollution is increasing.

Although few countries aside from the smaller ones in the Caribbean face water supply problems on a national scale, many must deal with such problems in urban areas. Local water shortages are particularly acute in the region's megacities. The supply of drinking water is also a major environmental, technological, and financial challenge in many of the smaller cities.

Lima, Peru, for example, is located in an area where not enough water is available, which has forced the costly extraction of water from distant watersheds. In other large urban centres, water supply is based on the unsustainable exploitation of underground aquifers. In Buenos Aires, some 55 per cent of the population obtains its drinking water from underground sources, some of which have serious levels of pollution. In Mexico City, around two thirds of the water used in the city is obtained from aquifers at a rate of extraction more than double the recharge rate (Gligo, 1995).

The concentration and increases in urban population in the region have also generated difficulties in the supply of water of adequate quality. In most cities, piped drinking water is not available to everyone. The mounting demand for drinking water has outstripped its supply, causing serious problems (ECLAC, 1992). Access to safe water in the region is highly variable, ranging from 100 per cent for the urban dwellers of Cuba and Chile to 63 per cent for those in the urban areas of Ecuador (UNICEF, 1994). Some 10 per cent of urban households in Bolivia, 25 per cent in Ecuador, 30 per cent in Guatemala, and 13 per cent in Honduras are without access to piped water-inside or outside (UN, 1995a).

The absence of sewage treatment, especially in rapidly expanding urban areas, creates problems. Approximately 80 per cent of the urban population in the region has access to adequate sanitation and sewerage services (collection, but not treatment), although there is great variation among the countries-from 100 per cent in Chile and 97 per cent in Venezuela to 40 per cent in Bolivia and 56 per cent in Ecuador (UNICEF, 1994). This relatively high percentage of sewage collection coupled with the low share receiving any treatment before discharge into rivers, lakes, and seas has resulted in water quality problems not only in cities, but also on downstream areas, coastal areas, and beaches.

Many of the megacities, such as Mexico City and São Paulo-Santos, contain large concentrations of industry with correspondingly high levels of contamination. Such cities are often highly polluted and lack adequate social and sanitation infrastructure and proper policies for the treatment of hazardous industrial waste. At the same time, land pressures and urban poverty mean that communities are often built near industrial plants that dump their wastes into the rivers, the seas, or onto the nearby land, and that pollute the air. The inhabitants of these low-income neighbourhoods are consequently exposed to hazardous waste and face health risks.

In addition, increasingly stringent environmental standards in the industrial world, particularly in North America, have driven industries to transfer some of their most polluting technologies to developing countries such as Mexico (LAC CDE, 1992). The need to develop a local industry has forced many LAC countries to accept polluting technologies and, in some cases, also the transboundary traffic of hazardous wastes. The largest proportion of hazardous wastes coming into the region does so under the terms of agreements between the United States and Mexico. As of 1988, Mexico had accepted 30,000 tons of such waste for industrial recycling (ECLAC, 1993b).

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