The Earth’s land surface is categorized into eight major biogeographical realms, vast regions distinguished by their shared evolutionary history and the unique distribution patterns of their terrestrial life forms. One such realm, the Afrotropical, stands out as a significant area for understanding global biodiversity. It represents a large and ecologically diverse expanse, home to a wide array of species that have evolved within its distinct environmental conditions.
Defining the Afrotropical Realm
The Afrotropical realm encompasses a substantial portion of the Earth’s land, covering approximately 22 million square kilometers. Its geographical scope primarily includes all of sub-Saharan Africa, extending south from the Sahara Desert. This vast area also incorporates the southern Arabian Peninsula, the island of Madagascar, parts of southern Iran, and extreme southwestern Pakistan. Beyond the continental landmass, the realm extends to include numerous surrounding oceanic islands. These include the Cape Verde Archipelago, the Comoros, the Mascarene Islands, and the Seychelles.
Distinctive Environmental Features
The Afrotropical realm is shaped by a wide range of climate patterns, which directly influence its biodiversity and ecosystem distribution. Near the equator, a tropical climate prevails, characterized by consistently high temperatures and humidity throughout the year. Moving north and south from the equator, subtropical climates emerge, exhibiting more pronounced seasonal temperature variations.
The realm’s diverse climate types give rise to a variety of terrestrial biomes. Tropical rainforests are prevalent in the Congo Basin and coastal West Africa. Extensive savannas and grasslands cover large areas of East and Southern Africa. Arid and semi-arid conditions lead to deserts and xeric shrublands in regions like the Horn of Africa and parts of Southern Africa, including the Namib Desert and the Kalahari Desert. High-altitude areas, such as the Ethiopian Highlands and the Drakensberg mountains, feature montane grasslands and shrublands.
Remarkable Biodiversity
The Afrotropical realm is home to an extraordinary array of life, with many endemic species. The East African plains are renowned for their diversity of large mammals, including elephants, rhinoceroses, and various antelope species. Iconic species like the African buffalo are found across sub-Saharan Africa, though often confined to protected areas.
The realm also hosts four species of great apes endemic to Central Africa: both species of gorilla, the western gorilla and eastern gorilla, and both species of chimpanzee, the common chimpanzee and bonobo. Unique bird families such as ostriches, secretary birds, guineafowl, and mousebirds are found here. Africa possesses three endemic orders of mammals: aardvarks, tenrecs and golden moles, and elephant shrews.
Madagascar, a distinctive sub-region within the realm, showcases exceptionally high levels of endemism. The island is home to over 200,000 species, with half of them found nowhere else globally. The Great Lakes of East Africa, including Victoria, Malawi, and Tanganyika, are centers of freshwater fish diversity, particularly cichlids, harboring more than two-thirds of the estimated 2,000 species in this family.
Key Ecological Regions
The Afrotropical realm is composed of several distinct ecological regions, each with its unique characteristics. The Guineo-Congolian region encompasses the tropical rainforest belt of West and Central Africa, extending to the islands of the Gulf of Guinea. This area is home to species such as the eastern gorilla, the largest living primate.
East Africa is characterized by its vast savannas and grasslands, exemplified by the Serengeti, which hosts one of the world’s largest mammal migrations. The Somali-Masai region in northeastern Africa features semi-arid Acacia-Commiphora woodlands, savannas, and bushlands. The Zambezian region, stretching across a broad belt of the continent, includes woodlands, savannas, grasslands, and thickets, with characteristic plant communities like Miombo and Mopane woodlands.
The Cape Floristic Region, located at the southern tip of Africa, has a Mediterranean climate and is home to a significant number of endemic plant species, including proteas.
Madagascar and the surrounding Indian Ocean islands form a particularly unique sub-region. Madagascar, an ancient landmass that separated from Africa millions of years ago, boasts diverse habitats ranging from rainforests to deserts and is notable for its high biodiversity and endemism, including unique animals like lemurs.