CRS-35 



DEFINING WETLANDS 



General Characteristics 



Swamps, tidal marshes, fens, freshwater marshes, bogs, prairie potholes — 

 these are but a few of the many names that describe wetland areas. No single 

 generally-accepted definition of the term wetland exists — a fact that makes 

 public controversy more difficult to resolve. Some are sandy, intertidal 

 areas with little vegetation, others have high water tables and grasses or 

 shrubs, while still others are dominated by tall trees and little water is 

 apparent from a cursory glance. But all wetlands have important unifying 

 characteristics that distinguish them from other landscape features. 



First, wetland areas are distinguished by the degree of exposure to 

 water. Plant communities and animal populations found in wetlands are dif- 

 ferent from surrounding areas because the ground is wetter, often saturated 

 or inundated, and the specialized plant and animal communities that succeed 

 in wet conditions are found in this habitat. Yet wetlands vary greatly, 

 depending in part on the pattern of wetness at individual sites. Different 

 plant species tolerate water at different depths; some wetland plants are 

 found where there is no visible standing water during a portion of the year. 

 Coastal wetlands maybe inundated by tides each day. Other wetland areas may 

 be wet seasonally. Other characteristics of water, or the hydrologic regime, 

 that influence the nature of wetlands include temperature, water depth, and 

 water chemistry. 



Second, wetland areas lie on the margin that separates water areas from 

 upland areas. Runoff from upland areas flows into wetlands, carrying sedi- 

 ments and pollutants. When adjacent water bodies flood, water elevations in 

 wetlands are raised and the wetland community is stressed. But even in nor- 

 mal conditions, wetlands are influenced by inputs from both environments. 



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