The Eastern Arc Mountains
There exists a mosaic, from the border of Kenya
of Tanzania with Mozambique which includes the islands of Zanzibar
Mafia and Pemba and embraces the so called Eastern Arc Mountains
stretching for some 700 hundred miles from the Taita Hills in Kenya
north to south some of which are: the Taita Hills, North and South
Pare, East and West Usambara, North and South Nguru , Uluguru and
Mahenge.
The highest point is in the Ulugurus and the average peak is
around 8,000 feet. Geologically the mountains are formed mainly from
Pre-Cambrian rock uplifted about 100 million years ago. Their
proximity to the Indian Ocean ensures high rainfall, and the climatic
conditions have been stable for the past 30 million years although
variation from year to year can be considerable, a result of the El
Niño effect, leading to droughts or floods. This high rainfall and
long-term climatic stability along with the isolation of the separate
mountain ranges have resulted in a flora and fauna that are both
ancient and diverse.
The original forest cover on the Eastern Arc Mountains
estimated to have fallen by about four fifths in the last 2000
thousand years to the mid-1990s when records were last taken. While no
reliable information exists for the true extent of recent forest loss
it is more likely to have deteriorated than improved.
Although the main biodiversity values are concentrated in
the forests there are a significant number of endemics (especially
plants) in non-forested habitats. While there is some debate in terms
of plant biogeography between the Eastern Arc Forest
Forest Mosaic where approximately 60% - a considerable proportion of
species – are found in both regions.
More importantly however is the fact that both of these
forest types contain a great number of species strictly endemic to
their areas.
Jim Lovett,
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