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-to-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). Wildlife and protected species With its varied habitats, the Okefenokee has become an area known for its abundance of plants and animals. There are 621 species of plants growing in the swamp, including the Longleaf Pine tree. Animals include 39 fish, 37 amphibian, 64 reptile, 234 bird, and 50 mammal species. The Okefenokee Swamp is world renowned for its amphibian populations that are bio-indicators of global health. Wildlife species include Florida raccoons, wading birds, ducks, American alligators and other reptiles, a variety of amphibians, North American river otters, Florida bobcats, raptors, Eastern American red foxes, wild boars, common minks, Virginia white-tailed deer, gray foxes, Florida skunks, Florida black bears, and songbirds. The swamp habitat also