serikali ya mapinduzi zanzibar care tanzania and department

6.0 EVALUATION OF BIOLOGICAL RESOURCES AND THEIR
CONSERVATION VALUE
Although in terms of biodiversity Pemba and Zanzibar may not be as rich as the
coastal forests (Frontier, 1995) and Eastern arc mountains on the mainland most of the
species in Pemba are isolated from the mainland populations. Some are endemic or
near endemic and others are races of their congeners on the mainland. Others are
threatened or endangered. All these species need to be protected and some of them
may need special attention and conservation programmes.
Apart from maintaining biological diveristy, plant resources at species and community
level are important in many respects ranging from life support systems, climate
control, ecological processes and as wildlife habitats.
A number of animal species are, like the plants, endemic or near endemic and there
are also species which are threatened or endangered. Animal resources contribute to
the biological diversity and also help to boost tourism. Most of the species are
threatened by exploitation, habitat loss, fragmentation and pollution. Species
designated endemic or near endemic and threatened need appropriate conservation
programmes.
Apart from their aesthetic value, the lepidopterans (Butterflies and Moths) and
Odonata (Dragonflies and Damselflies) are important as they form a large section of
the natural ecosystem in terms of number of individuals and species richness. They
are also important in maintaining the health of the ecosystem by controlling
vegetation through their herbivory and pollination activities (lepidopterans), and by
checking the population growth of other invertebrates through predation (Odonata). In
addition to the above, the two groups are useful as indicators of the health of the
ecosystem. They also form an important part of the food chain as a source of food to
many species of other animals.
7.0 POTENTIAL THREATS TO BIODIVERSITY
Nahonyo et al., (2002) reported that 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,
over-exploitation of species, and the introduction of exotic species (Newmark, 2002).
The situation in Ngezi - Vumawimbi is similar to that found in the Eastern Arc
Mountains on the mainland. From the observations done in the field, interviews and
documented literature the following were identified as threats to Ngezi - Vumawimbi
forest reserves biological diversity:
i. Human population pressure
Humans are a major cause of biodiversity loss in coastal ecosystems (Martens, 1992).
Pemba is experiencing a fast growing population (annual population growth rate r =
0.03). Ngezi - Vumawimbi forests are important source of fuelwood, charcoal,
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