Surrounding the rainforests of Central Africa is a diversity of savannah and woodland ecosystems, which transition to progressively drier ecoregions to the north and the south. To the north of the Congo basin and forest savannah mosaic is the Sahel Acacia Savanna, while to the south are the Miombo forest savannah woodlands. West of the Congo basin are the fragmented forests of the Guinea lowlands of West Africa; to the east lie the highlands of the Albertine Rift, also known as the Afromontane forests, and beyond this, the Acacia-Commiphora bushlands of Tanzania and Kenya.
Sahel – Sudanian Savannah
North of the Congolian forest savannah is the Sudanian savannah and the expansive Sahel acacia savannah ecoregions. Southern portions of the Sudanian ecoregions receive 1000 mm of annual rainfall, decreasing to 600 mm at the border with the Sahel, and 200 mm at the northern border with the Sahara desert. Rainfall is seasonal, falling primarily from May to September. In Arabic, Sahel means shore, referring to the transition between desert and forest. The southern region is dominated by Combretum and Terminalia shrubs and trees, as well as tall elephant grass (Cenchrus purpureum). In the drier Sahel, various species of Acacia trees intersperse wide spans of grassland. The savannah region is much lower in species richness than the humid forests of the Congo Basin, but still plays home to the large migrations of mammals- antelope, gazelle, elephant, and several species of cat predators. This region has been subjected to severe over-hunting and habitat loss from agriculture, as well as climatic threats from desertification.
South of the Congo Basin lay the Miombo woodlands, which stretch across southern Africa from Angola to Zambia and Tanzania. Similar to the forest – savannah ecoregions, most of this area is plateau of 200 – 800 meters elevation, and annual rainfall of 800-1200 mm. Common trees of this region include the Brachystegia (usually referred to as the Miombo tree), Julbernardia, and Isoberlinia genera, as well as African blackwood (Dalbergia melanoxylon), all of the legume family. Much of this area is sparsely inhabited, partially due to the presence of the harmful tsetse fly, which affects humans and livestock. Further south of the Miombo woodlands in Botswana and Namibia are the even drier Kalahari Acacia-Baikiaea woodland ecoregions and the Zamezian and Mopane woodlands. These dry woodland landscapes are dominated by acacias and the mopane tree (Colophospermum mopane), also a legume, as well as the unmistakable baoboab tree (Adansonia digitata).
The Guinean lowlands are a global biodiversity hotspot, with only approximately 10-20% of the native forest habitat remaining. Centuries of logging, as well as greater development and population pressure as compared to the Congo Basin have resulted in significant habitat loss throughout West Africa. The Guinean forest is comprised of the tropical forests of west and east Guinean lowland forests, the Nigerian lowland forests, and some coastal forest reaching from Nigeria into Cameroon. Biodiversity in this region is enhanced by the altitudinal gradient of the Cameroon highlands, which reach to 4,095 meters.
The Guinean forest region is wet, with several areas receiving more than 3,000 mm of annual rainfall. Forests are mostly evergreen, with a canopy of 30 meters and emergent trees of 50-60 meters. Common trees include Dacroydes klaineana, Strombosia glaucescens, Allanblackia floribunda, Coula edulis and Diospyros sanza-minika. Rare mammals in the Guinean forests include pygmy hippopotamus, several species of duiker, and western chimpanzees.
Albertine Mountains – Eastern Afromontane
The eastern boundary of the Congo Basin is formed by the Albertine Mountains, a mountain chain running from Uganda in the north, through Rwanda and Burundi, eastern DRC, and along Lake Tanganyika in the south. This ecoregion extends from the lowland forests of approximately 800 meters elevation, up to the juniper – heath moorland forests of the highest parts of the mountains, above 3,500 meters. Precipitation ranges from 1,200 mm to 2,200 mm annually. The montane forests are home to populations of the critically endangered mountain gorillas. The forests of the Albertine Mountains are critically endangered and highly fragmented due to the high human population and hunting and poaching.