A savanna or savannah is a tropical or subtropical woodland ecosystem characterized by the trees being sufficiently small or widely spaced so that the canopy does not close, above a continuous tall grass … A savanna or savannah is a mixed woodland - grassland (i. e. Grassy woodland) biome and ecosystem characterised by the trees being sufficiently widely spaced so that the canopy does not close.

Not enough rain falls on a savanna to support forests.