A savanna is a region where grasses grow naturally. They are found throughout the world, but tropical grasslands grow only in Africa, South America, Australia, and Asia. Grasslands that are outside of tropic areas are called temperate grasslands, not savannas. Grasslands grow where there is not enough water throughout the year to support many trees.
Some trees do grow on the savanna, but they are sparsely scattered.
The grasses are well adapted to the dry climate and have roots deep in the soil. Grasslands are important because they provide a home for many animals and insects. They also prevent erosion by wind and water because of their valuable topsoil. The largest savanna in the world is in Africa. In fact, nearly half of the continent is covered by savannas.