The Regional Impacts of Climate Change

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6.3.3.2. Sea-Level Rise

Projections of sea-level rise reported by IPCC Working Group I (scenario IS92a) indicate that sea level could rise, on average, about 5 mm/yr, within a range of uncertainty of 2-9 mm/yr. An important point to bear in mind is that the current best estimates represent a rate of sea-level rise that is about two to five times the rate experienced over the past 100 years (1.0-2.5 mm/yr). Changes in sea level at regional and local levels will not necessarily be the same as the global average change because vertical land movements affect sea level and there are dynamic effects resulting from oceanic circulation, wind and pressure patterns, and ocean-water density that cause variations in the level of the sea surface with respect to the geoid (IPCC 1996, WG II, Section 9.4).

Biogeophysical effects of sea-level rise will vary greatly in different coastal zones around the world because coastal landforms and ecosystems are dynamic; they respond to and modify the variety of external and internal processes that affect them. For instance, flooding conditions in the Pampas, in the province of Buenos Aires, would be exacerbated by any level of sea-level rise because the effectiveness of the Salado river as the only drainage system for this flatland would be reduced by sea-level rise. Some coastal sectors in Central America and on the Atlantic coast of South America would be subject to inundation risk. Flat areas-such as the Amazon, Orinoco, and Paraná river deltas-and the mouths of other rivers, such as the Magdalena in Colombia, would be affected by sea-level rise (IPCC, 1990). Estuaries like the Rio de la Plata also would suffer increasingly from saltwater intrusion, creating problems in freshwater supply. These effects will depend on the amount of sea-level rise and the characteristics of atmospheric and oceanic circulation.

Actual land loss resulting from sea-level rise may represent a small fraction of national territories, but it may have major impacts in those areas where large human settlements, tourist resorts, and other activities and infrastructure are located. Synthesized results of country case studies are presented in Table 6-5, including the estimated impacts of a 1.0-m sea-level rise. Consideration of particular cases, such as that of Uruguay, shows that although the amount of land lost on the Uruguayan coast would be rather small, the capital risk is very important. The national tourist industry, which creates more than US$200 million per year in revenues and attracts more than one million people each summer, might be seriously affected. Protected coastal areas, such as Laguna de Tacarigua in Venezuela, could be altered dramatically (Perdomo et al., 1996). The only areas of Argentina that are vulnerable to sea-level rise are the coasts of the province of Buenos Aires and the Rio de la Plata estuary (Perillo and Picccolo, 1992). The coastal aquifers also would be affected by sea-level rise and would suffer from seawater intrusion, affecting the supply of freshwater on both margins of the Rio de la Plata, including the densely populated Buenos Aires metropolitan area.


Table 6-5: Synthesized results of country studies. Results are for existing development and a 1-m sea-level rise. People affected, capital value at loss, and wetland at loss assume no adaptive measures (i.e., no human response), whereas adaptation assumes protection except in areas with low population density. All costs have been adjusted to 1990 US$ (adapted from Nicholls, 1995).

 
People Affected
Capital Value at Loss
Land at Loss
Wetland at Loss
Adaptation/ Protection
Country
# People (1000s)
% Total
Million US$
% GNP
km2
% Total
km2
Million US$
% GNP

Argentina
>5,000 (1)
>5
3,400
0.1
1,100
>1,800
>0.02
Belize
70
35
1,900
8.4
Guyana
600
80
4,000
1,115
2,400
1.1
500
200
0.26
Uruguay
13 (2)
<1
1,700 (1)
26
96
0.1
23
>1,000
>0.12
Venezuela
56 (2)
<1
330
1
5,700
0.6
5,600
>1,600
>0.03
Venezuela
153 (3)
0.46
124
0.22

(1) Minimum estimates-capital value at loss does not include ports.
( 2) Minimum estimates-number reflects estimated people displaced.
(3) Including land and buildings.
Note: The two Venezuelan cases are based on different methodologies and refer to different places.

Source: IPCC 1996, WG II, Table 9-3.


Most global fish resources depend on near-shore or estuarine habitats at some point in their life cycles (IPCC, 1990; Chambers, 1991). Fish production would suffer if coastal wetlands and other habitats that serve as nurseries were lost as a consequence of sea-level rise (Costa et al., 1994). It also is apparent that mangrove communities starve in microtidal, sediment-poor environments-such as around the Caribbean, where the lack of strong tidal currents does not permit sediment distribution (Parkinson et al., 1994).

Coastal oceans already are under stress from a combination of factors, such as increased population pressure, habitat destruction, increased land-based pollution, and increased river inputs of nutrients and other pollutants (IPCC 1996, WG II, Section 9.2.2). Therefore, the effects of global climate change could represent a mixed, and probably synergistic, series of impacts on an already overstressed context. There also may be synergistic effects between climate change and overfishing. These combined stresses would reduce fish quality and stocks in Latin American seas, increasing the vulnerability of the fishing industry-particularly on regional seas plied by countries outside the region. In addition to the aforementioned coastal zone vulnerability, sea-level rise and increasing storm activity would have adverse consequences for offshore extraction activities, marine transportation, human health, recreation, and tourism. An additional impact of sea-level rise on Latin American countries, particularly those with low population densities, would stem from political and cultural stresses arising from the relocation of immigrants from other regions (e.g., as a result of the inundation of low coastal zones and small islands) (Canziani, 1993).

In Central America, impacts associated with sea-level rise would have their greatest effects on infrastructure, agriculture, and natural resources along the coastline, with immediate effects on socioeconomic conditions in the isthmus countries. Sea-level rise would exacerbate the processes of coastal erosion and salinization of aquifers and increase flooding risks and the impacts of severe storms along the coastline (Campos et al., 1997).



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