The millions of acres of publicly owned lands managed by the U.S. government produce valuable resources, such as timber, minerals, oil and gas. Mainly located in Western states, these scenic and historic lands also are prized recreation areas where each year millions of visitors hunt, camp, hike and explore. Some conservatives want to restrict the government's authority to protect public lands from private development. Environmentalists say these lands need more protection, not less, and that mining and grazing on public lands have been underpriced for decades, encouraging waste and abuse. President Obama signed a law in 2009 setting aside 2.1 million federal acres as wilderness, but he also advocates allowing renewable-energy production on public lands, which some conservationists oppose. Meanwhile, climate change threatens many of the benefits derived from public lands, such as clean drinking water, safe habitats for endangered wildlife and pristine wild places for recreation.