Ochieng' Ogodo
10 March 2003
Nairobi — The allocation and destruction of forest lands has had serious impact on useful plants and animals, says Michael Gacanja of the Kenya Forest Working Group.
The pressure on useful plants will increase due to reduced habitat. Continued over-collection of medicinal plants will eventually end in the loss of those plants and affect the health of people who are not able to purchase modern medicines.
Forest loss in water catchment areas contribute to reduced water flow in rivers. In Mt. Kenya Forest, low water levels for downstream users following water abstraction by upstream users last year also raised tension between the two users. During the 1999/2000 drought that was compounded by deforestation in the country, Gachanja says, the Maasai community took their livestock for grazing and watering to Mt. Kenya Forest and neighbouring ranches in Laikipia District. Many conflicts on access and user rights was reported.
The destruction of forests has also led to serious impact on biodiversity. A large percentage of the country's biodiversity occurs in forests. Gachanja says closed canopy forest harbour 40 per cent of large mammals (of over 500g), thirty per cent of the birds and about 35 per cent of the butterflies occur in forest habitat.
There are three times as many threatened large species in forests as in Savanna. In the case of threatened birds, around 50 per cent occur in forests. Threatened species are known to occur in over 60 inland and 65 Coastal forests. Indeed, half of Kenya's threatened woody plants occur in Coastal forests. These Coastal forests combined with Taita Hills complex and the mountains east of the Rift Valley, account for almost all the rare forest biodiversity in Kenya, with a few other rare species scattered across the large blocks of mountain forests.
Overall, of the forest-dependent and nationally threatened species in Kenya's forests, about 50 per cent of the plants, 60 per cent of the birds and 65 per cent of the mammals are found in the Coastal forests despite its relatively small forest cover. Deforestation is known to have impacts on viable population of species within forests. Gachanja submits that some trees of special commercial importance may be so reduced in numbers that their populations may no longer be viable.
For example, milicia excelsa (Mvule) has been exploited for timber from the coastal forests for decades, and Vitex keniensis (Meru oak) and Olea capensis (Cape olive) are in a similar state of decline in the mountain forests.
The densities of forest-specialist birds in Mau and Kakamega have been shown to decline as a result of logging. Extreme destruction of forests through charcoal burning has driven animals out of forests. Elephants in Rumuruti forest are moving out to surrounding farms, causing human-wildlife conflicts. Logging that has been rampant in Kenyan forests removes part of the population of some species and at the same time alters a forest structure and therefore its micro climate, humidity and light regimes. The structure is changed to a more broken canopy formation, often with a much heavier liana load on the remaining tall trees.
The plant species composition shifts in favour of colonisers that proliferate in forest openings. Pole cutting can cause declines in biodiversity under extreme over-use because the young trees recover and produce coppice shoots. Similarly, the collection of dead wood for fuel may have some negative effects on the recycling of nutrients within the forest ecosystem.
In some parts of Kakamega, states Gachanja, hole-nesting forest birds have declined because dead branches in which they make nest-holes have been removed, and one part of Kakamega showed no signs of wood-eating termites because there was no deadwood on the ground .
Forests play a critical role in water catchment for the country. For example, Kenya's five main "water towers", the Mt. Kenya, the Aberdare, the Cherangani the Mau complex and the Mt. Elgon forests provide most of the nation's water.
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