Savannahs are tropical or subtropical grasslands with scattered, widely spaced trees and shrubs. They are characterised by a continuous grass layer and an open tree canopy (covering 10–30% of the ground). Savannahs experience distinct wet and dry seasons. They cover ~20% of Earth's land surface and are found in Africa (Serengeti), South America (Cerrado), and Australia. They differ from tropical rainforests (closed canopy, high rainfall) and temperate grasslands (no trees).