Jozani biodiversity inventory report 2002 - Coastal Forests of Kenya ...

6.0 POTENTIAL THREATS TO BIODIVERSITY
In the past traditional systems of land and resource use caused some damage to habitat and
biodiversity but probably regeneration occurred as long as population levels were low.
Human activities placed relatively little pressure on the available land resources. Also certain
cultural norms helped to ensure sustainable use of resources. Rapidly growing human
populations and associated socio-economic and political issues, and probably climatic
changes associated with greenhouse effects all together or individually have contributed
towards ecological instability. In the Eastern Arc Mountains the immediate threats to
biodiversity were identified as deforestation, forest fragmentation, forest degradation, overexploitation
of species, and the introduction of exotic species (Newmark, 2002). The situation
in Jozani is similar to that found in the Eastern Arc Mountains on the mainland. The
following were identified as threats to Jozani-Chwaka Bay proposed National Park biological
diversity:
1. Human population pressure
Humans are a major cause of biodiversity loss in coastal ecosystems (Martens, 1995).
Zanzibar is experiencing a fast growing population (annual population growth rate r = 0.03)
Jozani forest and the surrounding areas are important source of fuelwood, charcoal, building
poles (Plates 25, 26, 28), medicines, food and fodder (Appendix V). Over-use of the resources
is one major threat to the forest and loss of species. Increased population puts pressure on
land for farming and crops involve land clearance and thus a loss of habitats (Plates 2, 8, 9).
The introduced trees in Jozani area include coconut palm (Cocos nucifera), mangoes
(Mangifera indica), tamarind (Tamarindus indica), guavas (Psidium guajava), banana (Musa
spp.) (Plate 22) all of which are widespread in what was once natural vegetation area.
Humans are also responsible for over utilisation of animal resources from both terrestrial and
marine ecosystems through hunting, fishing and invertebrates collection (sea cucumbers,
bivalves).
2. Grazing impact
A number of people in Jozani and surrounding areas keep livestock including cattle, goats and
a few donkeys. Fodder plants include trees shrubs, forbs and grasses. Some species have
exceptionally high nutritive values and are preferred by domestic stock. Baobab (Adansonia
digitata) for instance contains about 16.9% crude protein and is so palatable that its seedlings
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