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The Afrotropical realm is one of the Earth's eight biogeographic realms. It includes Sub-Saharan Africa, the southern Arabian Peninsula, the island of Madagascar, and the islands of the western Indian Ocean.[1] It was formerly known as the Ethiopian Zone or Ethiopian Region.
Major ecological regions
Most of the Afrotropical realm, except for Africa's southern tip, has a tropical climate. A broad belt of deserts, including the Atlantic and Sahara deserts of northern Africa and the Arabian Desert of the Arabian Peninsula, separate the Afrotropic from the Palearctic realm, which includes northern Africa and temperate Eurasia.
Sahel and Sudan
South of the Sahara, two belts of tropical grassland and savanna run east and west across the continent, from the Atlantic Ocean to the Ethiopian Highlands. Immediately south of the Sahara lies the Sahel belt, a transitional zone of semi-arid short grassland and vachellia savanna. Rainfall increases further south in the Sudanian Savanna, also known simply as the Sudan region, a belt of taller grasslands and savannas. The Sudanian Savanna is home to two great flooded grasslands: the Sudd wetland in South Sudan, and the Niger Inland Delta in Mali. The forest-savanna mosaic is a transitional zone between the grasslands and the belt of tropical moist broadleaf forests near the equator.
Southern Arabian woodlands
South Arabia, which includes Yemen and parts of western Oman and southwestern Saudi Arabia, has few permanent forests. Some of the notable ones are Jabal Bura, Jabal Raymah, and Jabal Badaj in the Yemeni highland escarpment and the seasonal forests in eastern Yemen and the Dhofar region of Oman. Other woodlands that scatter the land are small, predominantly Juniperus or Vachellia forests.
Forest zone
The forest zone, a belt of lowland tropical moist broadleaf forests, runs across most of equatorial Africa's intertropical convergence zone. The Upper Guinean forests of West Africa extend along the coast from Guinea to Togo. The Dahomey Gap, a zone of forest-savanna mosaic that reaches to the coast, separates the Upper Guinean forests from the Lower Guinean forests, which extend along the Gulf of Guinea from eastern Benin through Cameroon and Gabon to the western Democratic Republic of the Congo. The largest tropical forest zone in Africa is the Congolian forests of the Congo Basin in Central Africa.
A belt of tropical moist broadleaf forest also runs along the Indian Ocean coast, from southern Somalia to South Africa.
Somali–Masai region
In northeastern Africa, semi-arid Acacia-Commiphora woodlands, savannas, and bushlands are the dominant plant communities. This region is called the Somali-Masai center of endemism or Somali-Masai region. It extends from central Tanzania northwards through the Horn of Africa and covers portions of Tanzania, Kenya, Ethiopia, Somalia, Djibouti, and Eritrea. Thorny, dry-season deciduous species of Vachellia and Senegalia (formerly Acacia) and Commiphora are the dominant trees, growing in open-canopied woodlands, open savannas, dense bushlands, and thickets. This region includes the Serengeti ecosystem, which is renowned for its wildlife.[2]
Eastern Africa's highlands
The Afromontane region extends from the Ethiopian Highlands to the Drakensberg Mountains of South Africa, including the East African Rift. This region is home to distinctive flora, including Podocarpus and Afrocarpus, as well as giant Lobelias and Senecios.
- Ethiopian Highlands
- Albertine rift montane forests
- East African montane forests and Eastern Arc forests
Zambezian region
The Zambezian region includes woodlands, savannas, grasslands, and thickets. Characteristic plant communities include Miombo woodlands, drier mopane and Baikiaea woodlands, and higher-elevation Bushveld. It extends from east to west in a broad belt across the continent, south of the rainforests of the Guineo-Congolian region, and north of the deserts of southeastern Africa, the countries are Malawi, Angola, Botswana, Mozambique, Zambia, and Zimbabwe, and the subtropical.[3]
Deserts of Southern Africa
Southern Africa contains several deserts. The Namib Desert is one of the oldest deserts in the world and extends for over 2,000 kilometers along the Atlantic coasts of Angola, Namibia, and South Africa. It is characterized by towering dunes and a diversity of endemic wildlife. Further inland concerning the Namib Desert, the Kalahari Desert is a semi-arid savanna spanning Botswana, Namibia, and South Africa. The Kalahari is known for its diversity of mineral resources, particularly diamonds, as well as a variety of flora. South of the Namib and Kalahari deserts is the Karoo. A semi-desert natural region, the Karoo desert spans across parts of the Western and Eastern Cape in South Africa and contains vast open spaces and unique vegetation, such as certain species of Asteraceae flowering plants. Within the boundaries of the larger Karoo, the Tankwa Karoo is a more arid sub-region known for harsher conditions and starker landscapes. Further to the west, the Richtersveld, a mountainous desert in the northwestern corner of South Africa, presents a rugged landscape. It is celebrated as a UNESCO World Heritage Site for its unique biodiversity and cultural significance to the local Nama people.
Cape floristic region
The Cape floristic region at Africa's southern tip is a Mediterranean climate region that is home to a significant number of endemic taxa, as well as to plant families like the proteas (Proteaceae) that are also found in the Australasian realm.
Madagascar and the Indian Ocean islands
Madagascar and neighboring islands form a distinctive sub-region of the realm, with numerous endemic taxa, such as lemurs. Madagascar and the Granitic Seychelles are old pieces of the ancient supercontinent of Gondwana, and broke away from Africa millions of years ago. Other Indian Ocean islands, like the Comoros and Mascarene Islands, are volcanic islands that formed more recently. Madagascar contains various plant habitats, from rainforests to mountains and deserts, as its biodiversity and ratio of endemism are extremely high.
Endemic plants and animals
Plants
The Afrotropical realm is home to several endemic plant families. Madagascar and the Indian Ocean Islands are home to ten endemic families of flowering plants; eight are endemic to Madagascar (Asteropeiaceae, Didymelaceae, Didiereaceae, Kaliphoraceae, Melanophyllaceae, Physenaceae, Sarcolaenaceae, and Sphaerosepalaceae), one to Seychelles (Mesdusagynaceae), and one to the Mascarene Islands (Psiloxylaceae). Twelve plant families are endemic or nearly endemic to South Africa (including Curtisiaceae, Heteropyxidaceae, Penaeaceae, Psiloxylaceae, and Rhynchocalycaceae) of which five are endemic to the Cape floristic province (including Grubbiaceae). Other endemic Afrotropic families include Barbeyaceae, Dirachmaceae, Montiniaceae, Myrothamnaceae, and Oliniaceae.
Animals
The East African Great Lakes (Victoria, Malawi, and Tanganyika) are the center of biodiversity of many freshwater fishes, especially cichlids (they harbor more than two-thirds of the estimated 2,000 species in the family).[3] The West African coastal rivers region covers only a fraction of West Africa, but harbors 322 of West Africa's fish species, with 247 restricted to this area and 129 restricted even to smaller ranges. The central rivers fauna comprise 194 fish species, with 119 endemics and only 33 restricted to small areas.[4]
The Afrotropic has various endemic bird families, including ostriches (Struthionidae), the secretary bird (Sagittariidae), guineafowl (Numididae), and mousebirds (Coliidae). Several families of passerines are limited to the Afrotropics, including rock-jumpers (Chaetopidae) and rockfowl (Picathartidae).
Africa has three endemic orders of mammals, the Tubulidentata (aardvarks), Afrosoricida (tenrecs and golden moles), and Macroscelidea (elephant shrews). The East-African plains are well known for their diversity of large mammals.
Four species of great apes (Hominidae) are endemic to Central Africa: both species of gorilla (western gorilla, Gorilla gorilla, and eastern gorilla, Gorilla beringei) and both species of chimpanzee (common chimpanzee, Pan troglodytes, and bonobo, Pan paniscus). Humans and their ancestors originated in Africa.
Afrotropical terrestrial ecoregions
Cape Verde Islands dry forests | Cape Verde |
Madagascar dry deciduous forests | Madagascar |
Zambezian Cryptosepalum dry forests | Zambia, Angola |
Albany thickets | South Africa |
Lowland fynbos and renosterveld | South Africa |
Montane fynbos and renosterveld | South Africa |