Grasslands, including shrublands, savannas, and tundra cover 40 percent of the earth's surface and are home to almost a billion people. Grasslands provide goods and services to support flora, fauna, as well as human populations worldwide. For instance, all of the major foodgrains -- corn, wheat, oats, rice, barley, millet, rye, and sorghum -- originate in grasslands and wild strains of grasses can provide genetic material to improve food crops and to help keep cultivated varieties resistant to disease. Grasslands produce forage for domestic livestock, provide habitat for breeding, migrating, and wintering birds, maintain ideal conditions for many soil fauna, and provide rangelands for wild herbivores. Some of the world's major animal migratory routes are dependent on grasslands, such as the migration of large herds of wildebeest in Africa, caribou in North America, and Tibetan antelope in Asia. Unfortunately, agriculture and urbanization have transformed grasslands worldwide. For some North American prairies, for example, conversion is already nearly 100 percent. Road-building and human-induced fires also are changing the extent, composition, and structure of grasslands around the globe.

Examination of grasslands according to watershed boundaries can facilitate integrated resource management. Within watersheds, grasslands absorb rainfall, recharge aquifers, stabilize soils, and moderate runoff. Many physical and biological features of grasslands can be managed effectively in the context of watersheds.

This map shows the percentage of each basin that is covered by grassland, shrubland, or savanna. For the purpose of this map areas covered by tundra have been excluded. Those basins with the largest percentage of grassland include the Burdekin-Belyando basin in Australia; the Orange, Okavango, Cuanza, Cunene, Rufiji, Volta, Jubba, Shaballe, Mangoky and Mania basins in Africa; Lake Titicaca and Salar de Uyuni in South America; and the Rio Grande basin in North and Central America.