The conservation of the forest resources of eastern Africa: past influences, present practices and future needs - Biogeography and Ecology of the Rain Forests of Eastern Africa - page 303

et al. (1973) show the importance of forest cover
and the magnitude of the problems where cover is
reduced. More recent studies such as those of
Dunne (1979) in Kenya, and Lundgren & Lund-
gren (1979) in Tanzania, emphasise the role of
forests in maintaining soil and water processes.
These studies compare forest and agriculture; few
studies compare forest types. L. Lundgren (1980)
stressed that different forest communiies have
different soil and water flow parameters. B.
Lundgren (1978) suggested that natural forest
was superior to plantaion forest in this respect.
Pocs (1980) documented the hydrological import-
ance of the dense bryophyte biomass in mist-
prone wet montane forest, a characterisic of old
growth natural forest. In general, however, the
effect of forest operaions (silvicultural tending,
thinning, felling, exracion) on catchment
properies has been little studied, although
general guidelines for improving hydrological
parameters are given by FAO (1976). Bruen
(1990) and Mbwana (1988) have looked at
hydrological characterisics of the Sigi River
catchment in the East Usambaras, attemping to
relate water flow regimes to past excessive log-
ging. Incomplete and inadequate data sets did not
permit a firm conclusion. Local comment,
however, is that climate is warmer; there is less
mist and fewer rainy days. People remark on
springs drying up, larger peak floods and heavy
water siltaion. These observaions on reduced
number of rainy days, hence less cloud cover,
more radiaion input and worsening evaporaion:
precipitaion raios (E/P) have been documented
elsewhere, e.g. Meher-Homji (1988) in India.
More and more local communiies are relaing
decreased forest cover to reduced spring flow.
Deorestaion is a result ofless care of past strictly
controlled village catchment ree cover, such as in
the Pare Mountains (Archaeology Deparment,
University of Dar es Salaam, personal communi-
caion, 1989). With excessive canopy opening,
runoff and sediment yield increase dramaically;
this is obvious. But quesions remain unanswered,
such as: 'What degree of eploitaion is permiss-
ible before catchment abiliy declines? Is dense
secondary regrowth as good as primary forest?
How can imber be extracted in a way which will

which eploitaion elsewhere can be measured.
It is known that huning and disturbance fac-
tors have caused local exincions from small for-
ests: Howell (1981) lists several vertebrate species
from Pugu Forest, and Rodgers (1981) menions
exincion of Colobus angolnsis from coastal forest
patches. The same must be true for more pre-
ferred meat sources such as duiker, suni, bush-
buck and bushpig. Buffalo are now absent from
Kigogo FR in the West Uzungwa Mountains.
Traps, pits and snares are commonplace in East
African forests.

he bioloical basis or orest
conservaion

Literature discussing the scieniic background to
forest conservaion, has greatly prolierated in the
past decade (UNESCO/UNEP/FAO, 1978 to,
for example, Saunders et al., 1987), although it
has not yet been synthesised in a format relevant
to the East African situaion. Literature deals
either with a single resource, such as water (e.g.
Pereira, 1973), or a complex, such as geneic
resources (e.g. Roche & Dourojeanni, 1984), or
theoreical aspects, such as the maintenance of
species numbers in reserves of varied size and
shape. This last concept stems from island bio-
geography theory and has recently been sum-
marised for the USA by Harris (1984).
This secion briefly reviews concepts of import-
ance in planning forest conservaion in easten
Africa. Topics are treated under the broad head-
ings of watersheds and hydrology, protected area
design, and sustainable uilisaion of resources.

Watesheds and hydroloy

Scienists and conservaionists have long known
of the link between dry season water flow and
forest cover in easten Africa. The maintenance
of a closed canopy to reduce erosivity of raindrop
impact, and maintenance of surface ground cover
to slow surface runoff, have been major tenets of
land use planning theory. The watershed experi-
ments in different catchments in East Africa sum-
marised by Pereira (1973) and the empirical data
from ield situaions in easten Tanzania in Rapp