Grassland, an area in which the natural vegetation consists mainly of grasses. The word grassland is also used for a plant community, or biome, made up primarily of grasses and related plants. Excluding pastures and other grassy areas created by man, grasslands make up about a fifth of the world's total land area.
Grasslands occur under varying climatic conditions, both in the tropics and in the middle latitudes (areas 30 to 60 degrees north and south of the Equator). Annual precipitation varies from scant to moderate, usually 10 to 25 inches (250 to 630 mm) in the middle latitudes and up to 60 inches (1,520 mm) in the tropics. Distinct wet and dry seasons are characteristic of most grasslands; droughts are rather frequent. An extremely large range in temperature is typical of middle-latitude grasslands; temperatures are generally high in the tropical grasslands.Swarm of Locusts over a village in Kenya
Three kinds of grasslands are usually recognized—steppe, prairie, and savanna—each with distinct characteristics and many variations in appearance. All three occur most frequently in the interior of continents. The tundra, though considered to be a grassland by some authorities, is atypical and is not included in this article.
Steppes, characterized by short grasses, cover much of the semiarid areas of the middle latitudes and tropics. Annual precipitation is scant. Trees and shrubs are usually found only along stream banks and in lowlying areas. Among the most extensive steppes are those of the North American Great Plains; those of Eurasia extending through Ukraine, southern Russia, northern Kazakhstan, Mongolia, and northern China; and those fringing large deserts in Africa and Australia.
Steppes are usually areas of low agricultural productivity, though some are used successfully for the raising of wheat and the grazing of cattle. The steppe area of the Great Plains is an example. With irrigation, steppes can be made highly productive. In many parts of the world, steppes have traditionally been used for nomadic herding.
Prairies, characterized by tall grasses, occur in the middle latitudes, lying generally between steppes and humid forested land. Precipitation is more abundant than on the steppes, and soils are far richer and deeper. Extensive prairies occur in the eastern Great Plains and the adjacent part of the Corn Belt in the United States, in southwestern Russia, and in Argentina. The pampas of South America are largely prairies; on their drier margins, they gradually become steppes.
Virtually nothing remains of the original vegetation of the prairies because the land is so heavily used for farming. Production consists chiefly of grains and livestock.
Savannas are areas of tall, coarse grasses and scattered trees growing singly or in small stands. In the broadest sense the term savanna refers to any such area, but it is most commonly (and in this section) applied only to such areas occurring in tropical or subtropical regions.
Distinct wet and dry seasons are especially characteristic of this kind of grassland. In extent, savannas greatly exceed the prairies and probably exceed the steppes as well.
Savannas cover large areas of central Africa, the Amazon Basin and llanos of South America, and the interior of Australia. Savannas are widely used for the grazing of cattle, though they are not prime grazing lands. In Africa savannas are infested with tsetse flies, which transmit various diseases to humans and cattle. African savannas are also the habitat of most of the continent's large animals.