Closely associated with the tropical wet-dry climate type which has a distinct dry season, located primarily in Africa and South America , covering a wide belt on either side of the equator. Soil moisture in dry season is not sufficient to support a full tree cover, hence this biome consists of trees widely spaced and much grassland in-between. Often described as having an open park-like appearance. The grasses are much longer here than in grasslands, growing up to 3 meters tall. Fire is very frequent here in the dry season, and limits tree growth.
Trees are very fire resistant with very thick bark.
Human use of fire is prevalent in many areas of the savanna biome, for livestock and agriculture purposes. Fire suppression is very damaging to savanna regions, resulting in huge conflagrations. In Africa, the thorntree-tall grass savanna rings the savanna woodland, with acacia the dominant tree species. The definition of a desert is a region with less than 25 cm of rainfall per year, and where potential evapotranspiration exceeds precipitation totals, i.e. , potential for outgoing moisture exceeds incoming moisture. In North America, it's found in the Great Basin and Colorado Plateau of the western US, but has expanded into steppe grasslands due to overgrazing by livestock.