OUR CHANGING ENVIRONMENT: Everglades, United States

South Florida, the southeastern tip of the United States, was once a 23 000 km² unbroken marshland of sawgrass and small tree islands. The Kissimmee-Okeechobee- Everglades region formed a system of rivers, lakes and wetlands that controlled water flow, mitigated seasonal flooding, filtered sediment, and provided habitats for hundreds of species.

In 1948, the federal government started draining the Everglades and building dikes and canals for agricultural uses. There was a large loss of biodiversity, with some 10 million alligators killed between 1960 and 1965. Populations of herons, egrets, storks and spoonbills had, by 1979, decreased by 90 per cent. By 1998, 68 species were endangered or threatened with extinction.

Agricultural intensification produced sugar cane, tropical fruit and winter vegetables. However, that benefit is now threatened by encroachment from urban areas. Since 1998, the US Army Corps of Engineers has been attempting to restore the natural function of the Everglades. The estimated cost is US$7.8 billion, which covers only the first stage of the restoration effort, which is expected to require more than three decades.

Landsat data: USGS/EROS Data Center Compilation: UNEP GRID Sioux Falls