wetlands, low-lying ecosystem where the water table is always at or near the surface. It is divided into estuarine and freshwater systems, which may be further subdivided by soil type and plant life into bogs, swamps, and marshes. Because wetlands have poor drainage, the area is characterized by sluggish or standing water that can create an open-water habitat for wildlife. Wetlands help to regulate the water cycle, filter the water supply, prevent soil erosion, and absorb floodwaters. More significantly, however, wetlands serve as spawning and feeding grounds for nearly one third of the endangered animal and plant species in the United States, and their ecological value in most other countries is comparable.
Many wetlands were destroyed by urban growth and farming before their value was recognized. More than half of U.S. wetlands in the lower 48 states have been lost since colonial times. Federal wetlands policy today is based on the wetlands provisions (1987) of the Clean Water Act. The working concept is that of "no net loss," a concept that has been interpreted in various ways by each federal administration. Although the U.S. Fish and Wildlife Service has estimated that more than one million acres (about 400,000 hectares) of wetlands were lost in the decade from 1985 to 1995, this assessment was down from nearly 3 million acres (1.2 million hectares) lost in the previous decade, before the wetlands preservation policy was in force. As part of the "no net loss" policy, developers who fill wetlands may create new ones, but a 2001 National Academy of Sciences report found that new wetlands were not always created and when they were they were often of lesser value, both to the environment and to people, than the wetlands they replaced. The report recommended that replacement wetlands be designed to recreate the function of the developed wetlands.
Because of the restrictions wetlands protection can place on development and agriculture, it has become a political battleground between property rights activists and environmentalists. In 2001 the Supreme Court ruled that the Clean Water Act did not authorize federal regulation of so-called isolated wetlands (wetlands that do not abut navigable waters or their tributaries); as much as a fifth of the nation's wetlands are potentially affected by the ruling.
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