Conservation became part of U.S. government policy with the creation (1871) of a U.S. commissioner of fish and fisheries. The Forestry Bureau of the Dept. of Agriculture created the first national forest reserve in 1891. The Irrigation Division in the U.S. Geological Survey developed into the Bureau of Reclamation. The Geological Survey has cataloged and classified the resources of the public domain. In 1906 an act protected the Alaskan fisheries. Conservation as part of a total approach to the use of natural resources was first introduced by President Theodore Roosevelt and his chief forester, Gifford Pinchot. In 1907 President Roosevelt appointed the Inland Waterways Commission, which emphasized the connection between forests, water supply, and stream flow. In 1909 he appointed the National Conservation Commission, which published the first inventory of the country's natural resources. Roosevelt in 1907 began withdrawing large areas of western public land from sale and settlement so that their resources might be investigated, and setting apart forest reserves, following the example of President Cleveland. Approximately one fourth of all timberland is held by the government. The National Park Service was created in 1916 to preserve landscapes of important aesthetic value. In the 1930s the erosion of much arable land in the Midwest underscored the need for land reclamation and for conservation in general. The National Industrial Recovery Act of 1933 provided for conservation. The Civilian Conservation Corps, founded in 1933 to relieve unemployment, furnished the personnel for many conservation projects. The Tennessee Valley Authority, set up in 1933, was an outstanding attempt to apply principles of conservation, soil reclamation, and electrification to an entire area, although some critics claim that the extensive river damming and similar New Deal legislation did not, on the whole, have a positive effect on the environment. By 1960 the Soil Conservation Service, established in 1935, covered 95% of all farms and ranches in the United States. By the same year, under the Conservation Reserve Program, some 28 million acres of cropland had been returned to grass and forest cover. Throughout the 1950s attention was focused on the problem of conservation of water resources, particularly in the Southwest. In the 1960s pollution problems came to the fore in all industrialized countries. In the United States numerous laws were passed to protect the environment and its resources (see environmentalism).

The commitment of nations to conservation policies varies. Some nations, such as Iraq, Cambodia, and the republics of the former Soviet Union, have no protected areas, while 38% of Ecuador's land is protected and 44% of Luxembourg's is. (In the United States 7% of the land is protected.) Plants and animals have been protected through curtailment of whaling and the taking of porpoises in tuna seines and restrictions on logging. Endangered species have been protected by the Convention on International Trade in Endangered Species of Wild Fauna and Flora (CITES, 1979). In addition to CITES, United Nations Conference on Environment and Development (the Earth Summit, 1992) produced an agreement to protect the world's biological diversity. The World Wildlife Fund, Greenpeace, and other organizations also have been active in promoting conservation internationally.