Savanna is a grassland with widely scattered trees and shrubs. Most savannas are in the tropics and lie between deserts and rain forests. Certain grasslands in temperate areas are also sometimes called savannas. This article discusses tropical savannas. For information about other savannas.
Savannas cover more than two-fifths of Africa and large areas of Australia, India, and South America. They occur in regions that have both rainy and dry seasons.
Most savannas receive from 30 to 40 inches (76 to 100 centimeters) of rain annually. But some get as little as 10 inches (25 centimeters) of rain, and others get as much as 60 inches (150 centimeters). Grasses on the driest savannas, where trees are widely scattered, grow only a few inches high. On more humid savannas, grasses grow several feet tall, and trees are more abundant. Grasses on the wettest savannas may reach heights of 10 feet (3 meters) or more.
Most savanna grasses grow in clumps and do not form a continuous cover of sod. Other nonwoody plants, including members of the composite and legume families, grow among the grasses. Acacias, baobabs, and palms are some common savanna trees.
The growth of trees on savannas is limited by the dry season, which may last up to five months. When the dry season begins, grasses stop growing and turn brown, and most trees shed their leaves. Only the most drought-resistant trees can survive. During the dry season, frequent brush fires destroy many young trees. Grasses have extensive root systems that survive the fires and send up fresh shoots as soon as the rains return. On some savannas, poor drainage and other soil conditions also favor the growth of grasses instead of trees.
A wide variety of animals live on savannas. Large herds of antelope and zebras graze on the African savannas. Cheetahs, hyenas, lions, and other meat-eaters prey on these animals. Many rodents, birds, reptiles, and insects also inhabit savannas.