Tropical rainforests cover most of the Congo basin in equatorial Africa.

The Congo River is at least 2,700 miles (4,350km) long. It is the second longest river in Africa.

Forests extend up on to the flanks of the mountains to the east and along the coast of the Gulf of Guinea to the northwest.

They are bounded by high mountain vegetation to the east.

Elsewhere in the lowlands, they gradually merge into seasonal tropical forests, open woodland and savannah.

In West Africa, a narrow coastal belt of humid climate gives way to progressively drier, more seasonal climates in the north. The vegetation also changes, from that typical of rainforest on the coast to that characteristic of desert in the Sahara.

Scientists believe that during the Ice Ages, Africa's climate was much drier, so the rainforests were much smaller.

The present southern Congo forests grow over the desert sands of the Kalahari, presumably having extended on to them in the current Interglacial period.

Today, the climate of the African rainforests is somewhat seasonal. The lowland rainforests with the least seasonal climates in Africa are comparable in structure and physiog¬nomy to the eastern, more seasonal parts of the Amazon and to the narrow, slightly seasonal fringe of the Asian rainforests.

Most of the African rainforests probably have fewer tree species per square mile than the rainforests of Asia and the least seasonal parts of the Americas, and have less varied composition over large areas.

The exceptions are Cameroon, Gabon, the corner of the Gulf of Guinea and the eastern fringe of the Congo. The rainforests in these places have many unique species of plants and animals.

Oil palm is the main world crop from African rainforests. African mahogany can be found in many of West Africa's rainforests.