Geology Reference
In-Depth Information
per
m2•
Severe soil erosion and land degradaion
with loss of ferility and the failure of large-scale
rehabilitation schemes (e.g. Watson, 1972) led to
major pressures on forest. In 1963, poliicians
yielded to this pressure and 120
m2
of natural
forest reserve in the West Usambaras were
degazetted. Poor land management and increas-
ing culivaion on steep slopes have since caused
severe erosion of this virgin land in less than 20
years.
Brown (1981, and in Rodgers
&
Homewood,
1982a) described the agricultural pracices of the
small and well-watered East Usambara Moun-
tains as extremely poor and non-producive forms
of subsistence shifing culivaion. An IUCN/
CDC (1985) report on the area showed a 48%
populaion increase from 1967 to 1978 with vil-
lage populaion densiies as high as 421 people
per
m2•
Many people are immigrants whose agri-
cultural practices take little account of soil fra-
gility. This coninued agricultural epansion, now
over 50% of the area, together with high intensiy
logging on steep slopes (see below) is stated to be
leading to 'a great loss of forest, impaired catch-
ment regulatory efficiency, soil erosion and
seriously depleted gene pools'.
(Figures are in thousand cubic metres of imber. Note
that new inventories suggest the potenial supply is
below these figures).
In Tanzania there are no new major plantaions
planned within natural forests, but small-scale
plantations have been developed in the past ten
years. For example, Rau Forest near Moshi, the
only major localiy for the massive leguminous
tree,
Oystima msoo,
has small plantaions of
exoic and native imbers (Rodgers, 1983), Kim-
boza Forest in the Uluguru foothills has several
patches of Cedrella, now regeneraing freely
(Rodgers et al., 1983), and Ngezi Forest on
Pemba has many small (< 10 ha) patches of
several exoic species (Rodgers et al., 1986). In the
East Usambaras parts of Kwamkoro Forest
Reserve (one of the largest blocks of natural for-
est) have been underplanted with Cphalosphaera
(indigenous) and Maesopsis (an exoic, which is
reely regeneraing). Maesopsis encroachment is
now thought to be one of the major problems of
natural forest management in the Usambaras
(Hamilton
&
Bensted-Smith, 1990).
Proposals from CDC to plant 10 000 ha of teak
in Kilombero in southern Tanzania are thought to
benefit conservaion by reducing pressure on
natural forest hardwoods, as well as contribuing
to export eanings and local industry (IIED/IRA,
1992).
There is now increasing concen that the level
of afforestaion for fuelwood is totally inadequate
to meet growing demand. Struhsaker (1987)
predicts that current and planned reafforestaion
programme will supply less than 5% of fuelwood
needs in Uganda. Pohjonen
&
Pukkala (1990)
analyse fuelwood plantaions in Ethiopia. They
esimate that 1 million ha are needed to prevent
coninued loss of natural orests. Today there are
310 000 ha of varied plantaion. If populaions
reach 70 million by
AD
2000 and villagers are to
switch from cow dung fuel to wood (so improving
soils) then 3-4 million ha are needed!
Forest plantations
Whilst plantaions are rapidly expanding, policy
now is generally not to replace eising natural
forest but to plant on degraded and otherwise
unused lands. There are excepions, however,
and recently the Kenya Forest Deparment had
plans for plantaions in parts of Kakamega and
Arabuko-Sokoke natural forests, both areas of
excepional biological values and which had each
been recommended for UNESCO Biosphere
Reserve Status. The increasing demand for im-
ber and the reduced level of remaining resources
in natural forests will no doubt lead to increased
pressures to 'improve' natural forest in years to
come. A report on producion forestry in
Tanzania (Poyry, 1980) gave the following projec-
ions for peeler and saw-logs:
Loging
Year:
1985 1990 2000 20
IO
Demand: 685 805 1220 1750
Potenial natural forest supply: 455 415 360 350
Within Tanzania, natural forests have long been
termed as catchment or producion forests as a
Search WWH ::
Custom Search