Okefenokee National Wildlife Refuge - Geography

Geography

Okefenokee NWR has an approved acquisition boundary of 519,480 acres (2,102 km²), which is 123,480 acres (500 km²) larger than its current area. Approximately 371,000 acres (1,500 km²) of the Okefenokee Swamp wetlands are incorporated into the refuge. 353,981 acres (1,432 km²) within the swamp were designated as the Okefenokee Wilderness, a part of the National Wilderness Preservation System when the Okefenokee Wilderness Act was passed in 1974, making it the third largest wilderness east of the Mississippi River.

The Okefenokee Swamp is a vast bog inside a huge, saucer-shaped depression that was once part of the ocean floor. The swamp now lies 103 to 128 feet (39 m) above mean sea level. Peat deposits, up to 15 feet (4.6 m) thick, cover much of the swamp floor. These deposits are so unstable in spots that trees and surrounding bushes tremble by stomping the surface. Native Americans named the area "Okefenokee" meaning "Land of the Trembling Earth". Swamp habitats include open wet "prairies," cypress forests, scrub-shrub vegetation, upland islands, and open lakes.

The Okefenokee Swamp is one of the world's largest intact freshwater ecosystems. It has been designated a Wetland of International Importance by the United Nations under the Ramsar Convention of 1971. The swamp is compared through research to wetlands worldwide. It is world-renowned for its amphibian populations that are bio-indicators of global health. Water from the Suwannee River Sill area is used as a standard reference by scientists throughout the world.

The slow-moving waters of the Okefenokee are tea-colored due to the tannic acid released from decaying vegetation. The principal outlet of the swamp, the Suwannee River, originates in the heart of the Okefenokee and drains southwest into the Gulf of Mexico. The swamp’s southeastern drainage to the Atlantic Ocean is the St. Mary’s River, which forms the boundary between Georgia and Florida.

The swamp contains numerous islands and lakes, along with vast areas of non-forested habitat. Prairies cover about 60,000 acres (240 km²) of the swamp. Once forested, these expanses of marsh were created during periods of severe drought when fires burned out vegetation and the top layers of peat. The prairies harbor a variety of wading birds: herons, egrets, ibises, cranes, and bitterns.

Refuge staff manages 33,000 acres (130 km²) of uplands which are being restored to once-abundant Longleaf Pine and wiregrass habitat.

Refuge staff and volunteers work to preserve the natural qualities of the swamp, provide habitat for a variety of wildlife, and provide recreational opportunities for visitors. They also conduct prescribed burns in upland areas; thin forests, create wildlife openings, plant longleaf pines; and monitor, manage, and improve wildlife populations and habitat.

The Okefenokee is a rainfall-dependent system, and when periods of drought occur, the area becomes susceptible to wildfire. A 20/30 year cycle of drought and fire has allowed the Okefenokee to exist as the unique wetland it is. These periods cause changes in the abundance of certain plants (more grasses growing in exposed areas,) the nesting success of certain wading birds (failure in extreme drought), and the location of some species of wildlife (fish migrate into deeper lakes and channels and are followed by predators.)