Natural resources are classified as renewable or nonrenewable. Renewable resources include wildlife and natural vegetation, and nonrenewable resources are those that cannot be replaced, such as fossil fuels, ores, and minerals. Although the conservation of natural resources has been recognized as desirable since ancient times, land use has frequently been poor, with disastrous results, such as silting of rivers, flooding of lowlands, uncontrolled livestock grazing, and excessive cutting of woody plants for fuel. Increasing industrialization continues to present severe conservation problems, although international efforts have been made in certain areas, such as the protection of some endangered species. In the United States, conservation developed gradually with the realization of the need to conserve natural resources, which in pioneer times seemed unlimited.
Conservation falls into categories that include forests, grazing lands, wildlife, and soil.
Grazing ranges are conserved by using only a portion of each range in order to maintain healthy plant growth and reproduction. Each range is stocked only with the number of animals that can be nourished properly on the land. Although these range protection principles are well established, hundreds of thousands of acres of public lands are still overgrazed. Wildlife can be maintained through careful management and controlled hunting, which allows for the killing of many species without affecting population levels. Soil conservation includes the zoning of land for the most suitable use, the use of soil-building plants in crop rotations, special methods for erosion control, and the maintenance of soil fertility through the use of chemical fertilizers.