Other Environmental Themes

Wetlands: Guardians of Biodiversity

For most of this country's history, the federal government actively promoted the drainage of swamps, bogs, marshes and prairie potholes, regarding them as nuisances in general and mosquito breeding grounds in particular. Under the Swamp Land Acts, starting in the mid-1800s, the federal government gave the states nearly 65 million wetland acres for "reclamation" and conversion to other uses. The practice of filling in wetlands began to reverse later in this century with the passage of the Clean Water Act and other policies that recognized the value of these soggy zones in sustaining wildlife, safeguarding water supplies and controlling floods. That realization has come none to soon, as more than half of this country's original wetlands have been wiped out by human activities. Similar degradation has occurred elsewhere. In the Aral Sea basin in Central Asia, for example, wetlands have shrunk by 85 percent, dramatically reducing waterfowl populations.

Wetlands are, in fact, biodiversity havens, providing breeding grounds and habitat for a broad array of birds, fish, and other wildlife. In the United States, they offer refuge to one half of the fish, one third of the bird and one sixth of the mammal species considered threatened or endangered.

Wetlands also serve as natural filters, removing pollution from waters flowing through them and recharging aquifers below. Water is cleansed as the wetland soils and vegetation trap sediments, heavy metals, and pathogenic microbes. Wetlands sift out nutrients such as nitrogen and phosphorus that cause eutrophication-the increased production of organic matter that can degrade water quality and impair fisheries. The economic value of this natural filtering is immense, reducing the need for costly water purification plants.

Flood control is yet another important service provided by wetlands, which act as reservoirs for rainfall and runoff, sopping up water from overflowing rivers and retarding the flow of floodwaters. Wetlands can, conversely, mitigate droughts by storing water during the wettest times of the year and slowly releasing it during drier periods.

An ambitious program announced in 1998 called for increasing the nation's wetlands by 100,000 acres per year, largely through restoration projects such as the $8 billion effort to bring back a more natural flow of water to the Florida Everglades. We still don't know the extent to which human engineering can revive the remarkable plumbing systems and biodiversity sanctuaries that nature once provided. Even though the effectiveness of mitigation efforts will undoubtedly improve over time, protecting existing wetlands should remain our top priority.