Eastern Arc Montane Forests - A Global Ecoregion

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Sanje waterfall, Udzungwe National Park. Tanzania.
© WWF-Canon / Peter DENTON

About the Area

The Eastern Arc Mountains consist of a complex of ranges and peaks that are among the oldest in Africa, as are the forest communities of the region. This ecoregion has experienced relatively moist conditions for a very long time because of its close proximity to the Indian Ocean, even as periodic drying trends affected much of Africa.

As is true with most mountainous regions in Africa, this forest system is isolated from other similar areas by great expanses of lowland habitats. Isolation has produced a high level of endemism with many local species of plants and animals restricted to single mountain ranges.

Altitude, age, soils, rainfall, and distance from the coast all contribute to the unique environment. The current climate of these mountains is much wetter than the surrounding lands, with perhumid (rain every month) conditions and rainfall up to 3,000 mm per year recorded in the eastern Uluguru Mountains.

Many locally endemic species of plants and animals are restricted to single mountain ranges, for e.g. the Usambara Mountains of northeast Tanzania alone have some 50 endemic tree species.
Size:
24,000 sq. km (9,000 sq. miles) 

Habitat type:
Tropical and Subtropical Moist Broadleaf Forests

Geographic Location:
Eastern Africa: Central Tanzania, extending into Kenya

Conservation Status:
Critical/Endangered

Local Species

Species include numerous birds such as Taita thrush (Turdus helleri), Usambara akalat (Sheppardia sharpei), Usambara eagle-owl (Bubo vosseleri), and the banded sunbird (Anthreptes rubritorques).

It has been estimated that there are over 2000 plant species in 800 genera in these montane and surrounding forests. At least 800 of these species are believed endemic to this ecoregion The forests are the centres of global endemism for the African violet (Saintpaulia) and Busy Lizzies (Impatiens), also are supported populations of the spectacular Usambara violet (Saintpaulia ionantha), Msambo tree (Allanblackia stuhlmanni), and a large Wild nutmeg (Cephalosphaera usambarensis).

These forests are also home to mammal species, including the endemic Abbot's duiker (Cephalophus spadix), Angolan black-and-white colobus (Colobus angolensis), forest-dwelling populations of the African buffalo (Syncerus caffer), and Harvey's duiker (Cephalophus harveyi).

Also found here are bizarre amblypygids, which live in dark hollows and look more like the monster in "Alien" rather than relatives of the common house spider! The strictly endemic reptiles include 10 species of chameleons (seven Chamaeleo and 3 Rhampholeon), 3 species of worm snakes (Typhlops), and 6 species of colubrid snakes in 4 genera.

Featured Species

Amblypygid (Damon diadema) is also known as tailless whip scorpions. The term“amblypygid" means "blunt rump", a reference to a lack of the telson ("tail") carried by related species. They are found in tropical and subtropical regions worldwide. Some species are subterranean; many are nocturnal.

During the day, they may hide under logs, bark, stones, or leaves and prefer a humid environment. Amblypygids may range from 5 to 40 mm. Their bodies are broad and highly flattened. Their very thin modified legs can extend several times the length of body. They have no silk glands or poisonous fangs, but can have prominent pincer-like pedipalps.

Amblypygids often move about sideways on their 6 walking legs, with one "whip" pointed in the direction of travel while the other probes on either side of them. Prey are located with these "whips", captured with pedipalps, and then torn to pieces with chelicerae.

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Threats

Few of the mountains have protected status, the rest threatened by agricultural expansion on lower slopes, firewood collection, and grazing. In some cases, there is significant commercial logging (mainly using pit-sawing techniques), and in other areas there is encroachment for farm plots and for the collection of other wood products for firewood and poles.

WWF’s work

WWF has been actively involved in conservation work in eastern Africa since 1962, beginning with the purchase of land in Nakuru, Kenya. The WWF Eastern Africa Regional Programme Office (WWF-EARPO) itself was founded 24 years later in 1986. It was established in Nairobi Kenya under the WWF Africa & Madagascar Programme (AMP). The office oversees WWF's work in Kenya, Tanzania, Uganda, Ethiopia, Rwanda, and Burundi.

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