The Eastern Afromontane Hotspot encompasses several widely scattered, but biogeographically similar mountain ranges in eastern Africa, from Saudi Arabia and Yemen in the north to Zimbabwe in the south. The main part of the hotspot's more than one million km² is made up of three ancient massifs: the Eastern Arc Mountains and Southern Rift, stretch from south-eastern Kenya to southern Tanzania and Malawi, with small outliers in eastern Zimbabwe and western Mozambique; the Albertine Rift includes portions of Rwanda, Burundi, Uganda, Tanzania and the Democratic Republic of Congo; and the Ethiopian Highlands covers much of Ethiopia, as well as small parts of Eritrea and Sudan, and is bisected by the Great Rift Valley. In addition to these three main massifs, a number of outlying mountains are part of this hotspot, including the neogene volcanics of the Kenyan and Tanzanian Highlands (e.g., Mt. Kilimanjaro, Mt. Meru, Mt. Kenya, Mt. Elgon, Aberdares Range, and other peaks), the Asir Mountains of southwest Saudi Arabia, the highlands of Yemen, and the Chimanimani Highlands of eastern Zimbabwe.
Many of these massifs are volcanic in origin, and indeed the Albertine Rift includes the still-active Virunga Volcanoes. This volcanic and seismic activity was caused by the separation of the African and Arabian tectonic plates about 35 million years ago. This resulted in the formation of the Great Rift Valley system that runs from Syria to Zimbabwe and Mozambique. The geological turmoil that created the mountains of this hotspot has also resulted in some of the world's most remarkable lakes, including Lake Tanganyika (the world's second-deepest lake at 1,471 meters deep), Lake Albert, Lake Tana, and Lake Malawi (Nyasa).
The flora of the Eastern Afromontane Hotspot shows much uniformity and continuity, its composition changing with increasing altitude. The lower altitudinal limit is usually taken as between 1,500 and 2,000 meters, although this is lower away from the equator, while the Knysna Forests in the Cape, which are considered to be the southernmost reaches of the Afromontane habitat (though not included here), are at 300 meters. The most widespread tree genus is Podocarpus, although Juniperus is found in drier forests of northeastern and eastern Africa. A zone of bamboo is often found between 2,000 and 3,000 meters, above which there is often a Hagenia forest zone up to 3,600 meters. Many species common in montane forest, such as trees of the genera Podocarpus and Juniperus, have economic importance, while several crops including coffee (Coffea arabica) and tef (Eragrostis tef) from the Ethiopian Highlands have been domesticated.
At the highest elevations, such as the Rwenzori Mountains, Aberdares, Mt. Elgon, Mt. Kilimanjaro, Mt. Kenya, and the Bale and Simien Mountains, Afroalpine vegetation typically occurs above 3,400 meters. Afroalpine vegetation is characterized by the presence of giant senecios (Dendrosenecio spp.), giant lobelias (Lobelia spp.), and Helichrysum scrub.
In the Eastern Arc Mountains, vegetation types include upper montane, montane, submontane and lowland forests, with Afromontane grassland and heathland plant communities at higher altitudes. Grasslands are the primary habitats of the Southern Rift, while forests are found in sheltered valleys and along mountain ridges.
The main vegetation type on the mountains of the Albertine Rift is montane forest. Glaciers and rock occur at the highest altitudes, below which is alpine moorland with giant Senecio, giant lobelia and bogs, followed by zones of giant heather, bamboo, montane forest, mid-altitude forest, lowland forest, woodland, and savanna. The Albertine Rift also has papyrus and Carex wetlands, as well as hot springs and a peculiar type of sclerophytic vegetation that colonizes old lava flows in the Virunga National Park in eastern Democratic Republic of Congo.
In the Ethiopian Highlands, the foothills support woodland vegetation, while forests at slightly higher elevations are dominated by conifers. Above 3,000 meters, the Afroalpine ecosystem consists of grassland and moorland, with an abundant herb layer, while the heathland scrub above this is dominated by heathers.