CRS-37 



types. In many coastal areas different types of wetlands are found In close 

 proximity, exchanging materials and chemicals, and increasing the overall 

 ecological diversity and natural productivity of the composite wetland and 

 water system. 



Condition (the degree to which a wetland has been altered by human 

 activity) is an important variable for assessing the functional potential 

 of wetlands. The most productive wetlands, that is areas that support large 

 and diverse populations, are usually associated with minimal human modifica- 

 tion. Wetlands are dynamic and transitory systems that respond easily and 

 rapidly to external changes. Wetlands can also be manipulated to provide 

 more of a desired function, but often at the expense of the diversity of the 

 system's productivity. For example, the U.S. Fish and Wildlife Service has 

 been mandated by Congress to establish wildlife refuges that provide habitat 

 for waterfowl. In some locations this habitat has been enhanced by construc- 

 ting low dams and establishing permanent shallow water areas for nesting and 

 feeding. This change in habitat may be an improvement for the waterfowl, 

 but it may reduce the overall wetland ecosystem's productivity. 



Different types of wetlands are being altered at different rates, largely 

 in response to local economic activities rather than determinations that wet- 

 land losses will not be significant. For example, with the accelerated demand 

 for farmland, the prairie potholes in the Northern Plains have been drained 

 at a fast rate in recent years. In south Louisiana, the increased pressure 

 to locate and develop domestic sources of oil and gas has intensified efforts 

 to modify coastal wetlands. 



Given the wide variation in size, location, and condition, many distinct 

 wetland types can be identified. A layman's list might include marshes, 

 swamps, and potholes. Similar wetlands may have different names in various 



