RANGELAND

also called Range, any extensive area of land that is occupied by native herbaceous or shrubby vegetation which is grazed by domestic or wild herbivores. The vegetation of ranges may include tallgrass prairies, steppes (shortgrass prairies), desert shrublands, shrub woodlands, savannas, chaparrals, and tundras. Temperate and tropical forests that are used for grazing as well as timber production can also be considered rangeland. Rangelands thus occupy about 4050 percent of the land area of the Earth. Rangelands are distinguished from pastureland by the presence on them of native vegetation, rather than of plants established by human societies, and by their management principally through the control of the number of animals grazing on them, as opposed to the more intensive agricultural practices of seeding, irrigation, and the use of fertilizers. The tallgrass prairies of the North American Great Plains, the Ukraine, and parts of Argentina and Hungary formerly made ideal rangelands but were too well-suited to cultivated crops to be left for grazing purposes. Rangelands are thus more generally confined to areas of marginal or submarginal agricultural land or to areas that are entirely unsuited to permanent cultivation. Fire is an important regulator of range vegetation, whether set by humans or arising from lightning. Fires tend to burn or kill off trees, shrubs, and brush and to permit the more quickly recovering grasses to flourish without excessive competition from the former. The artificial elimination of periodic fires from desert shrublands, savannas, or woodlands frequently invites the dominance of trees and shrubs to the near exclusion of the grass. Range management is a professional field whose aim is to ensure a sustained yield of rangeland products while protecting and improving the basic range resources of soil, water, and plant and animal life. Besides producing forage for domestic and wild animals, a range can provide timber, minerals, natural beauty, and recreational opportunities. Modern range management utilizes the concept of multiple use, which requires that all the resources of a rangeland be managed simultaneously, using constant monitoring and adjustments to provide a mix of material products and intangible assets that best satisfy the needs of both landowners and the general public. Range management depends for its effectiveness on range science, which is a body of knowledge drawn from the botanical and zoological sciences as well as from ecology, climatology, pedology (soil science), hydrology, and so on. The responses of rangeland to grazing and other uses are predicted from range science's accumulated knowledge of the functioning of rangeland ecosystems, which in turn has been aided by computer-simulated mathematical models. In concrete terms, range-management practices centre on the regulation of the number of animals allowed to graze on a given range, along with the duration and season of their grazing. The stocking of a range must be carefully regulated so that the existing grasses are not depleted or exhausted from overgrazing. Indeed, the most pernicious and chronic problem in the management of ranges is overgrazing. Overgrazing of the vegetation reduces the production of forage; exposes the soil to sealing, baking, and erosion; reduces the infiltration of water into the soil; increases water runoff and flooding; and induces unfavourable changes in the botanical composition of the vegetation. Overgrazing has practically denuded vast areas of rangeland in nearly every continent, and in the Sahel region of sub-Saharan Africa, for instance, overgrazing has led directly to the southward expansion of the Sahara (Desert) over distances of many miles. The degeneration of range condition has become one of the most serious problems in the agriculture of many developing countries. See also grassland.