Where Animals Roam Wild
The climate and vegetation reflect the position of the continent astride the equator. A sequence of ecological zones extends north and south of the equator: the equatorial forest, the savanna grasslands, the desert, and the area of mild, Mediterranean-type climate. Where highlands occur within these zones, conditions are cooler and wetter. The rainfall of these zones is associated with the movement of air masses, caused by the seasonal warming and cooling of different parts of the Earth as it rotates around the sun. In the Northern Hemisphere, or north of the equator, rain falls from April to September.
In the Southern Hemisphere, it rains from October to March. The exceptions are the equatorial regions, which have year-round rainfall; the extreme north and south of the continent, which have only winter rainfall (Mediterranean climate); and parts of West and East Africa, where the climate is affected by the seasonal monsoon winds. The heaviest rainfall occurs in the equatorial regions. The savanna areas receive moderate rainfall. In the deserts rainfall is uncommon, but when it does occur it usually comes in the form of heavy downpours. In the savanna and desert areas rain falls mainly in the summer months; winters are almost completely dry.
Because of the differences in rainfall between one part of the continent and another, the vegetation is also widely varied. In the areas around the equator, where it rains the year around, are dense rain forests that may contain as many as 3,000 different tree and plant species per square mile. The forest usually forms three layers: a ground cover of shrubs and ferns between 2 and 3 metres high; a woody layer of trees and climbers reaching about 18 metres; and a canopy of broad-leafed evergreen trees growing as high as 46 metres.
Between the equatorial rain forests and the great deserts to the north and south are the savanna areas. These are open grasslands scattered with trees such as acacias and baobabs. Farmers and herders live in the savanna. In the eastern and southern regions of Africa, certain savanna areas contain large numbers of wild animals.
A serious problem for the people of the savanna is that the vegetation is being used up, leaving the land bare. The population in these areas has grown rapidly since the 1950s, creating a rising demand for pasture and for wood used as fuel and for construction. There is concern among conservationists that the removal of vegetation may cause the savanna to become more desert-like.
Another problem is that the summer rains are unpredictable in amount, duration, and distribution. Occasionally the monsoons fail and drought results. Between 1970 and 1974 a drought occurred over much of the African savanna. It was particularly severe in West Africa, where it is estimated that 250,000 people and 6 million head of livestock died.
Beyond the savanna, where the annual rainfall is less than 16 inches (40 centimetres), are the Sahara, the Namib, and the Kalahari deserts. The deserts cannot support large populations. In the Sahara there are a few nomadic herders, such as the Tuareg and the Gabbra. A number of countries extract minerals, notably petroleum in Algeria and Libya.
While the rain forest, savanna, and deserts cover most of the continent, there are smaller areas of mountain and Mediterranean environments. The mountain environments are found in such highland areas as the Atlas Mountains and the Ethiopian Highlands. The Mediterranean climatic zones are restricted to two narrow bands, one in Morocco, Algeria, and Tunisia and one in South Africa.