Potential Impact of Global Change to Wetlands

Sea-level rise is one of the more certain consequences of increased global temperature. During the past 100 years sea level has risen at a global average rate of about 1-2 mm year (Gornitz, 

A projected two- to fivefold accelerafion of global average sea-level rise during fhe nexf 100 years (IPCC, 1996) would inundate low-lying coastal wetland habitats that cannot transgress inland or vertically accrete at a rate that equals or exceeds sea-level rise. 

Increased mean global temperatnre of 1-3.5°C over the next century (IPCC, 1998) in combination with either stable, or rednced, or even slightly increased total precipitation wonld serionsly impact freshwater wetlands. Relatively small changes in precipitation, evaporation, or transpiration that alter surface and gronndwater level by only a few centimeters will be enongh to rednce or expand many wetlands in size, convert some wetlands to dry land, or shift one wetland type to another (Bnrkett and Knsler, 2000). 

Vast expansions of tnndra, marshes, and wet meadows nnderlain by permafrost (ground material below freezing) may be altered by changes in temperatnre and hydrology. A warming of 

Reductions in wetland area and distribution can be expected with increases in temperature or reduced precipitation in prairie pothole regions, which provide habitat for about half of the nation s waterfowl (Poiani et al., 1995). Virtually all wetlands provide storage of carbon in trees, shrubs, grasses, organic debris, and soils. Due to anaerobic conditions, carbon is stored in wetlands for much longer periods than in most upland systems (see Chapter 5). 

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