Environmental Engineering Reference
In-Depth Information
Methods
plantation agriculture is, but it is most frequently referred to
as a large scale, usually foreign-owned and specialised high-
input/high-output farming system that is export oriented
(Courtenay
1980
). The plantations owned both on large-
scale investors and by smallholders are key sources of
income for many farmers and countries in the tropics.
Several studies carried out have shown that deforestation
due to agricultural activities often leads to severe transfor-
mations and degradation of the coastal aquatic ecosystems,
especially through water quality changes. Metals tend to be
assimilated in sediment with organic matter, Fe/Mn oxides,
sulphides and clay thus forming several reactive components
which are harmful to the environment (Wang and Chen
2000
; Praveena et al.
2010
). Hence, sediment is always
regarded as the potential reservoir for metals and plays an
important role in adsorption of dissolved heavy metals
(Wang and Chen
2000
; Praveena et al.
2010
). Under dif-
ferent physical and chemical conditions, metals in sediment
may leach out into the water column as free ions. In turn,
contaminated sediments also act as sources of heavy metals
when released into the river water. Metals concentration in
river water can be regarded as a good indicator of the river
contamination. Metal ions can be either an essential nutrient
or toxic to living organisms (Salomons and Förstner
1984
).
When the metals concentration exceeds standard permissible
limits, it would have toxic effects on living organisms and
cause negative impact on lower life forms. When these
metals enter into the food chain through phytoplankton and
are biomagnified in aquatic organisms, they would pose
potential risk to human health (Alkarkhi et al.
2009
).
Moreover, deforestation and degradation following
plantation establishment are also important factors of cli-
mate change contributing up to 30 % of greenhouse gases
especially carbon dioxide (CO
2
) that is known to cause
global warming with consequent implications on the rise in
sea level (Mitchell et al.
2007
) especially as forests are
carbon dioxide 'sinks' informing many of the current
international efforts at mitigating climate change with cur-
rent initiatives such as reducing emissions from deforesta-
tion and degradation (REDD+). The UN- REDD+ works to
benefit the climate by preserving the tropical forest eco-
systems to enhance the continuous delivery of environ-
mental goods and services to ameliorate climate change
impacts. Therefore, effective management of coastal agro-
forests as well as plantations will enhance the prospect of
deriving environmental benefits of forests from them. This
study aims at analysing changes in the areal extent of
plantations within the coastal Atlantic estuarine forest
complex area of Cameroon between the periods 1986, 2000
and 2011 to ascertain the extent of deforestation due to
plantation agriculture as a basis of searching for ways to
enhancing sustainability of the plantation ecosystem.
Site Description
The south-west region of Cameroon is located approxi-
mately between latitude 4
o
and 6
o
and longitude 8
o
and
9
o
45
0
east of the equator, covering an area of approximately
24,571 km
2
. It is bordered to the north by the Federal
Republic of Nigeria, to the east by the north-west region, to
the west by the Atlantic Ocean and to the south by the
Littoral Region (See map, Fig.
1
). The area is characterised
by a humid equatorial climatic type with high rainfall. Due
to the orientation of the slopes of Mount Cameroon, it
receives the monsoon winds at right angle. As a result of
this, the moisture transported by the monsoon from the
ocean is deposited in the form of heavy rainfall. The Limbe
area has an annual rainfall average of 4,050 mm (Neba
1987
). Rainfall reaches a peak of about 7,000 mm in July
and August. Debuncha that is the wettest place in West and
Central Africa has an annual rainfall of 10,000 mm which is
the highest in the region. The relative humidity of the area is
strongly influenced by its maritime location and is at
75-80 %. The maximum annual temperature of the area is
25 C, while the minimum is 24.7 C suggesting a rela-
tively high constant temperature with a low range. Neba
(
1987
) puts the annual temperature at 24 C. The vegetation
of the area is characterised by the equatorial rainforest type.
It forms the discontinuity of the swampy vegetation which
is dominant along the Cameroon coastline (Neba
1987
). The
luxuriant evergreen forest is comprised of a variety of tree
species such as Lophira alata, Sacoglottis gabonensis and
Erythrophleum ivorensis. The largest National Park—
Korup National Park—with many rare and endangered
species and the Limbe Botanic garden among others are
found in this region. As a result of man's intervention, the
climax vegetation has been cut down for human activities
such as agriculture, communication, transportation and
urbanisation. The secondary vegetation is now widespread
with the luxuriant vegetation occupying peripheral positions
mostly at high altitudes (Neba
1987
). One conspicuous
feature of human intervention is the domination of the
vegetation by Cameroon Development Cooperation (CDC)
plantations at the foot of Mount Cameroon (Fig.
2
).
Mount Cameroon (4,100 m), the highest physical feature
in West Africa and an active volcanic mountain which lastly
erupted in May 2000, is found in this region (Neba
1987
).
The area is well drained and is an important watershed as
most of the streams take their sources from Mount Cam-
eroon and flow across the west slopes cutting V-shaped and
U-shaped valleys before draining into the sea. The Wouri
estuary lies to the east of Mount Cameroon and empties into
the Bight of Biafra (Fig.
3
). It is fed by the Mungo, Wouri
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