The United States government has direct ownership of almost 650 million acres of land (2.63 million square kilometers) – nearly 30% of its total territory. These federal lands, which are mainly used as military bases or testing grounds, nature parks and reserves and indian reservations, are managed by different administrations, such as the Bureau of Land Management, the US Forest Service, the US Fish and Wildlife Service, the National Park Service, the Bureau of Indian Affairs, the US Department of Defense, the US Army Corps of Engineers, the US Bureau of Reclamation or the Tennessee Valley Authority.