The forests extend in a narrow band along the coast of the
Indian Ocean, from southern
Somalia in the north, through coastal
Kenya and
Tanzania to the mouth of the
Limpopo River in southern
Mozambique. The forest belt is 50 to 200 km wide, and extends further west along river valleys. They are bounded on the west by drier grasslands and savannas. Pockets of coastal forest grow on the windward eastern slopes of mountains further inland, including the
Eastern Arc Mountains of Tanzania and Kenya and some
inselbergs in northern Mozambique, where rainfall and dry-season humidity are higher than the adjacent lowlands.[1]
Rainfall averages from 800 and 1200 mm per year in most of the coastal belt, with a well-defined dry season. Rainfall is similar to the interior savannas, but humidity in the coastal belt is higher during the dry season. A few places have higher rainfall, including the islands of islands of
Unguja (Zanzibar) and
Pemba and the eastern slopes of the
East Usambara Mountains, and are home to rain forests.[1]
Flora
Forest was once the primary
climax vegetation across most of the region. Most primary forest has been replaced by secondary wooded grassland, agriculture, and forest plantations. Frank White (1983) identified ten characteristic plant communities:[1][2]
Zanzibar-Inhambane lowland rain forest It found mostly in Tanzania, on the windward (east-facing) slopes of the
Uluguru,
Nguru, and
Usambara Mountains, and in parts of
Ulanga and
Iringa districts. Trees form a closed evergreen canopy up to 20 meters tall, with emergent trees up to 40 meters tall. It is now reduced to small remnant patches.[1]
Transitional rain forest grows at middle elevations (above 800 meters) in the Usambara and other nearby mountains. It is a transition between lowland and montane forests, and includes a mix of lowland and
Afromontane species, along with many endemic species. The
Amani Forest in Tanzania's Usambara mountains is the most intact remnant of this forest type.[1]
Zanzibar-Inhambane undifferentiated forest varies in form and species composition based on rainfall and soils. In moister areas, trees form a canopy 15-20 meters high, with emergents of 30 or 35 meters. Many trees are evergreen, while others are briefly deciduous.[1]
Zanzibar-Inhambane scrub forest. In Somalia and Kenya, scrub forest grows in a band between coastal forests and the drier bushlands of the interior.[1] It is also found near the coast in Kenya and Tanzania, often on
coral rag.[1][3]
Swamp forest grows in limited areas in the coastal lowlands, often inland from coastal mangroves and exending along the lower reaches of rivers. Barringtonia racemosa is the predominant tree. Swamp forests of
Raffia palm grow in low-lying areas of
Pemba Island.[1]
Zanzibar-Inhambane transition woodland
Zanzibar-Inhambane woodland and scrub woodland
Zanzibar-Inhambane evergreen and semi-evergreen bushland and thicket
Zanzibar-Inhambane edaphic grassland
Zanzibar-Inhambane secondary grassland and wooded grassland
White (1983) estimated 3000 plant species were native to the region, of which several hundred are endemic. Of 192 native forest trees recorded by White, 90, or nearly half, are endemic.[1]
^
abcdefghijWhite, F.; Unesco; Association pour l'étude taxonomique de la flore d'Afrique tropicale; United Nations Sudano-Sahelian Office (1983). Vegetation of Africa : a descriptive memoir to accompany the Unesco/AETFAT/UNSO vegetation map of Africa. Paris: Unesco.
ISBN92-3-101955-4.
OCLC10387142.
^Kindt R, van Breugel P, Orwa C, Lillesø JPB, Jamnadass R and Graudal L (2015) Useful tree species for Eastern Africa: a species selection tool based on the VECEA map. Version 2.0. World Agroforestry Centre (ICRAF) and Forest & Landscape Denmark. //vegetationmap4africa.org
^Kindt, R., van Breugel, P., Lillesø, J-P. B., Bingham, M., Demissew, S., Dudley, C., ... Graudal, L. O. V. (2011). Potential natural vegetation of Eastern Africa (Ethiopia, Kenya, Malawi, Rwanda, Tanzania, Uganda and Zambia): Volume 2: description and tree species composition for forest potential natural vegetation types. Forest & Landscape, University of Copenhagen. Forest & Landscape Working Papers, No. 62/2011