Many local communities depend on coastal wetlands for survival; they use a wide range of natural products from the swamps and their surrounding waters (Field, 1997; RAMSAR, 1999). As Section 6.5.4 points out, in some coastal societies, cultural values are of equalor even greatersignificance than economic values. This is particularly true in Ecuador and Colombia on the Pacific coast, as well as the most northern part of Venezuela and Brazil on the Atlantic coast, where shrimp farming and timber exploitation represent the most common uses (Schaeffer-Novelli and Cintron, 1993; Sebastiani et al., 1996; Trujillo, 1998). Girot (1991) identifies the landscape and the aesthetics and spirituality of local people as important social and cultural impacts in the Central American region. An increase in sea level could affect monuments and historic sites of Central America.
Patterns of human development and social organization in a community are important factors in determining the vulnerability of people and social institutions to sea-level rise and other coastal hazards. The most common problems in local subsistence economies in Latin America coastal zones relate to firewood, isolation from enforcement, shrimp ponds, cattle, clearing for village expansion, coconut plantation, and sewage and garbage disposal (Sebastiani et al., 1996; Ellison and Fanrsworth, 1997).
Water resources for domestic, industrial, and agricultural use, averaged per capita among Latin American countries, vary from 28,739 m3 in Argentina (whose population is 34,587,000) to more than 472,813 m3 in Suriname (whose population is 423,000) (see Appendix D of IPCC, 1998). These averages hide the enormous disparity in many areas, such as poor rural areas, which are ill-supplied. In some Latin American regionsespecially in areas where it is possible that the combined effect of less rainfall and more evaporation could take place, leading to less runoffglobal warming will substantially change the availability of freshwater. Watersheds in arid or semi-arid regions are especially sensitive because annual runoff already is highly variable (Medeiros, 1994). Watersheds in the southern hemisphere where snowmelt is an important source of runoff also can be severely affected (Basso, 1997). Vulnerability of oases between 29°S and 36°S to drier conditions in the high Andes can be observed (Canziani et al., 1997)
Few specific water resources impact studies using climate change scenarios have been conducted in Latin America: Riebsame et al. (1995) studied the Uruguay River basin. In the study, all scenarios used indicated a shift of seasonality and a decrease in runoff during low-flow periods. For the Choqueyapu River (La Paz, Bolivia) under a UKMO-89 climate scenario, these studies projected an increase of discharge in the low-water period and in the months of December and January. For some other watersheds (Caire, Mamoré, Guadalquivir, and Miguillas), the magnitude and tendency of the results varies, depending on the scenario used (PNCC, 1997). For the Pirai River, located in a humid area and flowing through urban areas (Santa Cruz City), runoff increases under an increased precipitation scenario (PNCC, 2000). Estimates of water availability in Mexico and Central America (Izmailova and Moiseenko, 1998) indicate that about 70% of the population in those countries will live in regions with low water supply as soon as the first quarter of the 21st century. A study using climate scenarios from GFDL, GISS, and NCAR models, combined with incremental scenarios of 1-2°C temperature rise and 10% precipitation increase, found that decreasing precipitation in Mexico and El Salvador can cause a change in runoff by 5-7% but that in the winter runoff changes by only by 0.2-0.7%.
Potential changes in temperature and precipitation might have a dramatic impact on the pattern and magnitude of runoff, soil moisture, and evaporation, as well as the aridity level of some hydrological zones in Mexico (Mendoza et al., 1997). A vulnerability study performed in conjunction with the National GHG Inventory in Argentina foresees a reduction in water availability as a result of changes in snowmelt in the high Andes. Similar studies in Peru show that warming has created several environmental hazards, such as avalanches in Peruvian Andean valleys, with a foreseen critical reduction of water resources for human and industrial consumption (Morales-Arnao, 1999).
Water use in Latin America is mainly for agricultural activities, averaging nearly 60% of total water use. It ranges from approximately 40% in Colombia and Venezuela to more than 75% in Argentina, Bolivia, Costa Rica, El Salvador, Ecuador, Guatemala, Honduras, Mexico, Panama, Paraguay, Suriname, and Uruguay (Canziani et al., 1998). Even with a potential increase in water availability in some parts of northern Mexico (Mundo and Martínez-Austria, 1993; Magaña and Conde, 1998), demand for water from agricultural, urban, and industrial sectors has shown a much faster growth because of the rapid expansion of these sectors in recent decades.
Some hydrological scenarios for Cuba (Planos and Barros, 1999) show that a significant limitation of potential water resources will occur within the next century as a result of increments in evapotranspiration and changes in precipitation.
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