declines in populations of grizzly bears, antelope, and 

 mountain sheep in the West. But there also had been 

 substantial increases in populations of wildlife asso- 

 ciated with farming, such as mourning doves, bob- 

 white quail, cottontail rabbits, meadowlarks, and 

 crows. The regrowth of previously cutover forest 

 lands was accompanied by tremendous increases dur- 

 ing the thirties in the numbers of white-tailed deer in 

 the East and, a decade later, in black-tailed deer in 

 the West. Prairie grouse in the Lake States gave way 

 to ruffed grouse; beaver, coyotes, and black bears 

 became abundant. ^^ 



Man's activities tend to lead to "islands" of homo- 

 geneous vegetation. For example, on lands devoted 

 to commercial timber production, every effort is 

 made to speed the juvenile stage of growth so timber 

 can be harvested as early as possible. On range lands, 

 shrubs and forbs are removed and grasses encouraged 

 to provide as much forage as possible for livestock. 

 As a result of such activities, the range of habitats 

 available to wildhfe within an area is reduced and the 

 species remaining are the relatively few adapted to 

 this limited range (although the number of animals 

 within each species may increase). The borders 

 between homogeneous areas must provide the "edge" 

 that is essential for a wide variety of species. 



Natural succession also changes habitat conditions, 

 generally in the opposite direction of man's activities. 

 Abandoned agricultural lands tend to return to 

 forests. Openings in forests are filled in as new trees 

 grow. On prairie agricultural lands, annual plants are 

 replaced by combinations of perennial grasses, herbs, 

 and shrubs. To the extent that those interested in wild 

 animals favor the species associated with farm lands 

 or that require openings in forests, the manager has 

 the task of fighting nature to artificially maintain 

 approximately those conditions. 



Loss of Wetlands 



During the two centuries of the Nation's existence, 

 the area of wetlands in the contiguous States has been 

 reduced by nearly half, from 127 million to about 70 

 million acres. These areas provide key habitat for 

 waterfowl and many other wildlife species. The areas 

 currently most threatened by drainage, primarily for 

 agricultural purposes, and the most critical areas of 

 waterfowl habitat, are shown in fig. 4.8. Drainage of 

 wetlands in the prairie-pothole country of Minnesota 

 and the Dakotas and in the coastal zone of the south- 

 eastern United States poses a continuing threat to 

 wetland-associated wildlife populations. 



^2 Abstracted from Allen, D. L. Historical perspective. In Land 

 use and wildlife resources. National Academy of Sciences. 

 Washington, D.C. 128 p. 1970. 



The "edge" where two different vegetation types meet is an 

 essential habitat for many species of wildlife. 



Overall, perhaps 80 percent of all riparian habitats 

 found in wetlands adjacent to rivers, streams, and 

 other bodies of water has been lost. No ecosystems 

 are more essential to the survival of the Nation's fish 

 and wildlife. For example, western riparian eco- 

 systems contain approximately 42 percent of the 

 mammal species of North America, 38 percent of the 

 bird species, 30 percent of the reptiles, and 14 percent 

 of the amphibians. Seventy-seven percent of the 

 breeding bird species and 75 species of fish of the 

 Southwest depend on riparian ecosystems. Eastern 

 wildlife most severely affected by the loss of riparian 

 wetlands includes otter, muskrat, mink, beaver, rac- 

 coon, Canadian geese, and wood ducks." 



Endangered species are associated with at least 20 

 percent of all riparian lands. Nine riparian wetland 

 habitats are on the Critical Habitat List and 17 more 

 have been proposed. (A critical habitat is defined by 

 the Endangered Species Act as the area of land, air, 

 or water required for the normal needs and survival 

 of a species listed as endangered or threatened.) 

 Sixty-four species which are dependent upon riparian 

 ecosystems have been listed as endangered and 47 

 more have been proposed for listing. 



When wetlands are filled or drained, they are usu- 

 ally turned to other valuable but competing uses. 

 Indeed, one-quarter of all privately-owned agricul- 

 tural soils in the United States were originally 

 wetland. The recent high price of soybeans has stimu- 

 lated the clearing and draining of bottom land hard- 

 woods in the Lower Mississippi Valley and the south- 

 eastern coastal States. Similar activities in the prairie 



"Council on Environmental Quality. Environmental quality — 

 1978. Washington, D.C. p. 316. 1978. 



136 



