Some time after the dinosaurs roamed on earth, the first grass species came into existence -- this was in the Miocene and Pliocene epochs when vast grasslands began to replace trees in many parts of the world. Today, almost half of Africa is covered by grasslands.
Grasslands in tropical regions are known as savannahs, while elsewhere in the world they are known as temperate grasslands. Temperate grasslands can be divided into prairies and steppes. The South African highveld is a temperate grassland while much of the grasslands in Botswana would be kalahari savannah.
Climate is an important deciding factor in the formation of a savannah, where between 50 and 130cm of rain must fall in a distinct seasonal pattern. Year-round rainfall produces tropical forests, whereas a dry season allows fires to burn and maintain the ecosystem as a grassland. Temperate grasslands also have distinct seasonal rainfall, but generally survive on less rain than savannahs.
Savannahs can also be created by shallow soils and the clearing of forested areas by both man and elephants. Many animal species find homes in savannahs, and the strong grazing pressure often causes one or a few grass species to thrive in different areas.
Deciduous trees and shrubs may also grow in savannahs, and in some places trees are only found on the richer soils of termite mounds. Grasses survive high grazing pressure because their growing points are close to the soil, and are not usually removed by grazing.
Grasslands are often endangered ecosystems, because many natural grasslands are often turned to agricultural use -- either to graze (and sometimes overgraze) domestic livestock, or are ploughed up to grow crops. Natural grasslands are often flat, and their lack of trees makes them an easy target for ploughing.
 Common Grasses of Southern African Countries
Southern African Grass Species Checklist : Poaceae : Gramineae
Interesting facts about the Grass Family
African Savannah Biome
Grassland Ecology Management in Southern Africa
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