Nationally, the 57 sites selected for study include 485,000 ha of coastal wetlands. Under the 

 high scenario, about 73 percent (192,000 ha) of the sample wetlands would be lost by 2100. 

 However, formation of new wetlands reduced the loss to 56 percent of the 1975 wetland area. 

 Under the low scenario, about 40 percent of the 1975 wetlands would be inundated, but new 

 wetlands extended over 85,100 ha, leaving a net reduction by 2100 of 107,000 ha or 22 percent of 

 the 1975 wetlands. The apparent national pattern is dominated by the Gulf Coast, especially the 

 Mississippi Delta, and by the South Atlantic regions where the largest wetland areas are found. 



Wetland decline occurred at case study sites from all regions under high scenario conditions 

 except for the relatively small wetland areas considered in the Califomian and Columbian 

 provinces. However, in San Francisco Bay, which contains by far the largest area of wetlands, 

 both major losses and gains occurred, depending on local conditions and whether or not wet- 

 lands were allowed to migrate. Also, the complex shoreline of Puget Sound probably was not 

 adequately characterized by the selected case studies. 



Further east, relatively large wetland losses predominated everywhere under the high 

 scenario. New England and Mississippi Delta study areas lost much, or nearly all, of 1975 

 wetlands with no compensating gains of new wetlands. Elsewhere along the Atlantic and Gulf 

 Coasts, small-to-low landward gains fell well short of the 1975 wetland losses. Trends under the 

 low scenario were similar for most regions, showing substantial but smaller wetland losses. Clear 

 exceptions occurred, however, in the south Atlantic and in subtropical Florida. In both regions, 

 gains in certain study areas balance significant losses in other areas; thus, values averaged over 

 these regions impart little information. 



In summary, some areas may exhibit an increase in wetlands if lowlands are permitted to be 

 inundated by sea level rise; and in some areas existing wetlands may persist well into the next 

 century. Over extensive areas of the United States, however, virtually all wetlands may be lost by 

 2100 if adjacent lowlands are developed and protected, instead of being reserved for wetland 

 migration. 



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