An understanding of the basic hydrologic processes that control the formation, persistence, size, and functions of wetlands is necessary for determining appropriate protective measures for particular wetlands and for determining the success of those measures. The source and distribution of water is a major factor in the differences in wetland types and distribution across the country. Both a favorable geologic setting and an adequate and persistent supply of water are necessary for the existence of a wetland. The source of water largely determines its quality, which in turn is largely responsible for wetland vegetation. The wetland vegetation affects the value of the wetland to animals and people.
Wetlands provide many beneficial water-related functions.
One of the best known functions of wetlands is as habitat for birds. About one-third of the North American bird species use wetlands for water, food, shelter, or breeding. About 138 of the 1,900 bird species in the conterminous United States are wetland dependent. For wetland-dependent birds, habitat loss or degradation usually translates to population loss. Wetland Management And Research Many of the benefits that wetlands provide accrue primarily to the general public instead of the private landowners.