Interior Wetlands of the United States. A Review of Wetland Status, General Ecology, Biodiversity, and Management.

Interior, freshwater wetlands of the United States include potholes, marshes, swamps, bogs, fens, and riparian wetlands. These wetlands are diverse in form and function and have unique properties that make them different from both terrestrial and aquatic ecosystems. The biological complexity and ecological functions of wetlands make these ecosystems among the most valuable and productive on earth Mitsch and Gosselink 198611. For example, wetlands are valued for functions such as surface-water storage, groundwater recharge, removal and transformation of nutrients, and soil stabilization Greeson, Clark, and Clark 1979 Smith et al., In Preparation. Wetlands also provide habitat for fish and wildlife, including a third of the nations threatened and endangered species National Research Council NRC 1992a265. Despite their ecological importance, wetlands have been lost and degraded at alarming rates. An estimated 53 percent of the original 89.4 million ha of wetlands in the lower 48 States were lost by the mid-1970s Dahl 1990, and losses continued at approximately 117,000 ha per year from the mid-1970s to the mid-1980s Dahl and Johnson 1991. The national policy has changed gradually over the past 20 years from encouraging the draining and filling of worthless swampland to recognizing the many benefits provided by wetlands and considering them a valuable national resource Ratti and Kadlec 19921.