The Regional Impacts of Climate Change

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Approximately 35% of the world's continental water (freshwater) is found in Latin America. However, its distribution within and among countries is highly variable. Freshwater systems (i.e., rivers, lakes, reservoirs, nontidal wetlands) and their ecosystems are potentially very sensitive to climate change and vulnerable to short-term fluctuations in climate, such as those associated with the ENSO phenomenon.

In the humid tropics, extreme precipitation events would increase the number of reservoirs silting up well before their design lives have been reached. Other areas affected by the impact of climate change on water resources could be those that rely on freshwater ecosystems (i.e., lakes and inland wetlands and their biota), including commercial and subsistence fisheries. Climate change will interact strongly with anthropogenic changes in land use, waste disposal, and water extraction; regional water resources will become increasingly stressed by higher demands to meet the needs of growing populations and economies, as well as by temperature increases. Conflicts may arise among users and regions-and even among Latin American countries that share common river basins. The effects of climate change on agricultural demands for water, particularly for irrigation, will depend significantly on changes in agricultural potential, prices of agricultural produce, and water costs.

The vulnerability of Latin American countries to climate change strongly depends on the impacts of climate change on water availability, as shown by studies performed under the auspices of the U.S. Country Studies Program (USCSP) and the Global Environment Facility (GEF). Changes in precipitation rates have consequences for hydropower production in Costa Rica, Panama, and western Argentina. ENSO events during recent decades have led to a significant reduction in runoff and consequently to higher dependence on thermal energy production, especially in areas with few energy alternatives. Alterations in hydrological balance resulting from climate change could reduce already impaired water supply and distribution systems in major Latin American cities and rural areas. According to vulnerability studies carried out in Mexico and Peru, the combined impacts of global warming and population growth could result in major reductions in water availability in both countries in coming decades. Monitoring of the hydrological cycle, sensitivity studies, development planning, and improved water management practices are key elements in preparing for projected water shortages.

Studies of vulnerability to sea-level rise have suggested that countries of the Central American isthmus as well as Venezuela and Uruguay could suffer adverse impacts leading to losses of coastal land and biodiversity, saltwater intrusion, and infrastructure damage. Impacts likely would be multiple and complex, with major economic implications.

Agricultural lands (excluding pastures) represent approximately 19% of the land area of Latin America. Over the past 40 years, the contribution of agriculture to the gross domestic product (GDP) of Latin American countries has been on the order of 10%. Agriculture remains a key sector in the regional economy, however, because it occupies an important segment (30-40%) of the economically active population. It also is very important for the food security of the poorest sectors of the population. Studies in Brazil, Chile, Argentina, and Uruguay based on GCMs and crop models project decreased yields of a number of crops (e.g., barley, grapes, maize, potatoes, soybeans, wheat)-even when the direct effects of carbon dioxide (CO2) fertilization and the implementation of moderate adaptation measures at the farm level are considered. Global warming also could enhance the negative impacts of animal and plant diseases and pests, with further negative effects on production.

Large alterations in Latin American ecosystems resulting from climate change impacts would have the potential to endanger the livelihoods of subsistence farmers and pastoral peoples, who make up a large portion of the rural populations of the Andean plateaus and tropical and subtropical forest areas.

Projected changes in climate could increase the impacts of already serious chronic malnutrition and diseases affecting a large sector of the Latin American population. The geographical distribution of vector-borne diseases (e.g., malaria, dengue, Chagas') and infectious diseases (e.g., cholera) would expand southward and to higher elevations if temperature and precipitation increase. Increasing pollution and high concentrations of ground-level ozone, aggravated by increasing surface temperatures and higher solar radiation rates, could negatively affect human health and welfare, especially in urban areas.

Although climate change may bring benefits for certain regions in Latin America, increasing environmental deterioration resulting from the misuse of land might be aggravated by the impacts of climate change on water availability and agricultural lands, as a result of coastal inundation stemming from sea-level rise and riverine and flatland flooding. Socioeconomic and health problems could be exacerbated in critical areas, fostering massive migrations of rural and coastal populations and deepening national and international conflicts.

Additional efforts in monitoring, research, and sensitivity analyses are needed to allow decision makers and other stakeholders to understand the potential consequences of climate change and variability, take advantage of potential benefits, minimize negative impacts, and seek adequate adaptation options. Specific priorities include organization and/or updating of biogeophysical observation networks and monitoring systems, development of regional circulation models, performance of sensitivity analyses of key sectors-from ecosystems to infrastructure-that appear to be most vulnerable in each country or subregion, and development of suitable adaptation options. These efforts include the creation of new technologies and the adaptation of existing technologies generated within or outside the region. Promising options include horizontal cooperation initiatives among countries of this region and assistance from countries of other regions of the world-particularly Canada and the United States-as well as countries of the temperate Southern Hemisphere that already are integrated into the Valdivia Group.

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