Natural grasslands occur in areas with erratic or inconsistent rainfall, whereas semi-deserts in extreme environments.
Such conditions develop on continents, far from seas and oceans, where water-rich clouds are scarce. Grasslands can be classified according to the biomeA biome is a vast community of plants and animals (including soil organisms) with similar environmental characteristics they belong to:
- Tropical grasslands (bordered by tropical rainforests and deserts): savanna in Africa and India, cerrado and llanos in South America (flooded temporarily, but dry in the hot season).
- Temperate grasslands: prairies in North America, pampas (campos in Brasil) in South America, veld in South Africa and steppe in Europe and Asia.
Other factors besides the climate (which has a crucial role in the distribution of grasslands) are wildfires, grazing by large herds of herbivores, floods and man-made landscape management. That is why grassland cover nowadays is much larger than it was before the evolution of modern humans.