52 * Wetlands: Their Use and Regulation 



There is little published information on the fate of 

 pathogens in wetland systems (3). 



Fish and Wildlife Values 



Wetlands are important to many species of fish 

 and wildlife for food, habitat, and support of the 

 food chain. The importance of plant productivity 

 is reflected in the relatively high carrying capacity 

 of wetlands for certain species. Bottom land hard- 

 wood forests, for instance, have been found to sup- 

 port nearly twice as many whitetail deer per unit 

 area as do upland forests, owing, it is thought, to 

 the abundance of food. Wetland vegetation also 

 provides nesting material and sites for numerous 

 birds and mammals; some freshwater fish rely on 

 clumps of vegetation for depositing their eggs. 

 Finally, emergent wetland plants provide the cover 

 necessary for protection from predators or for stalk- 

 ing prey for species of birds as well as fish and 

 shellfish. Some species spend their entire life within 

 a particular wetland; others are residents only dur- 

 ing a particular lifecycle or time of year. 



Because of their value for food and habitat, wet- 

 lands often become a focal point for varied wildlife 

 populations within a particular region. The impor- 

 tance of wetlands is reflected by the relatively large 

 proportion of wetland in the National Wildlife Re- 

 fuge System. While only 5 percent of the Nation's 

 area (excluding Alaska) is wetland, nearly 40 per- 

 cent of the area protected under the refuge system 

 is wetland. In turn, these areas attract hunters, 

 birdwatchers, and many other wildlife enthusiasts. 

 Of the top 25 wildlife refuges most visited, 19 have 

 a significant wetland component. Refuges contain- 

 ing wetlands attracted nearly 14 million visitors in 

 1981 , approximately 50 percent of the number visit- 

 ing all of the national wildlife refuges (90). 



Because of their numbers, it is impossible to de- 

 scribe adequately all the different species that use 

 wetlands. This section focuses on recreational and 

 commercial species of prime importance to man and 

 on endangered species that depend to varying de- 

 grees on the food and habitat found uniquely in 

 wetlands. Some species, termed "wetland special- 

 ists," are heavily dependent on wetlands. They in- 

 clude migratory waterfowl, mammals, the alligator, 

 freshwater game fish, crayfish, and 35 endangered 



species. Because of the direct link between wetlands 

 and these species, wetland losses will cause signifi- 

 cant and adverse impacts on these indigenous pop- 

 ulations. 



This section also identifies other wildlife that 

 heavily use wetlands as well as other nonwetland 

 areas. Deer, for instance, browse in bottom land 

 hardwoods, but they are not limited to these areas. 

 Wetland resources may, however, be a critical or 

 limiting factor in their survival. Because these 

 animals are not linked as strongly to wetlands as 

 are wetland specialists, wetland losses would ad- 

 versely affect populations of nonspecialists to a lesser 

 extent. 



Finally, this section discusses the food chain val- 

 ues of wetlands. Many commercially and recrea- 

 tionally important species that do not directly use 

 wetlands for feeding, nesting, or protection may 

 feed on animals lower in the food chain that do rely 

 directly either on wetlands or on detritus that floats 

 from the wedand into adjacent bodies of water. The 

 most important example of this food chain effect 

 in terms of commercial and recreational value is 

 the link between coastal wetlands and estuarine- 

 dependent fish. 



Food and Habitat 



Migratory Waterfowl. — Wetlands are vital to 

 many species of the duck, geese, and swan family 

 of North America for nesting, food, and cover. 

 These birds primarily nest in Northern freshwater 

 wedands in the spring and summer, but use wet- 

 lands for feeding and cover in all parts of the coun- 

 try during migration and overwintering. The sur- 

 vival, return, and successful breeding of many 

 species, therefore, depend on a wide variety of wet- 

 land types distributed over a large geographic area 

 of the country (fig. 5). The major migratory routes, 

 breeding and nesting areas, and overwintering 

 areas roughly correspond with regions of greatest 

 wetland concentration (see fig. 1). 



The most important areas for ducks and geese 

 are the breeding areas of the North, like the prairie- 

 pothole region, Canada, and Alaska. For over- 

 wintering, the Chesapeake Bay, the gulf coast, the 

 central valley of California, and the Mississippi 

 River stand out (fig. 5). Also essentiad, but not in- 



