The main problems and their causes
It is perhaps ironic that the problems of the coastal zone and ocean in
Sub-Saharan Africa derive from their usefulness and in particular from the
settlement of humans on or near the coast.
The open ocean, however, seems as yet to be largely unaffected by either the
environmental degradation wrought by humans or the overexploitation of its
natural resources. For living resources in the open ocean, the only danger
signal comes not from the activities of coastal states but from foreign fleets
(from Japan, South Korea, Taiwan, and the former USSR, among others), which
"poach" fish from these waters. For example, tuna in the western
Indian Ocean (eastern Africa) is heavily exploited by these foreign fleets and
recent indications are that yellow and southern blue fin tuna and bill fish are
overexploited and that bigeye tuna and albacore are fully exploited (Ardill
1984). Bryceson et al. (1990) stated that this fishing pressure with highly
sophisticated gear has an adverse impact on smaller-scale operations conducted
by the fishing fleets of the region, and that artisanal fishermen have noticed
marked decreases in catches of large pelagic migratory species.
On the Atlantic coast of Africa, similar pressures exerted by foreign fishing
fleets have produced similar consequences (e.g. depletion of deep water
prawn/shrimp resources) for the local fishing industry (Ajayi, personal
Besides the operations of foreign fishing fleets, which are sometimes
illegal, many of the fisheries of the region are artisanal and based mainly in
the coastal zone. Here population pressures have increased consumption and
demands and led to the use of destructive fishing methods.
In the coastal zone of eastern Africa, the most environmentally destructive
method of fishing is dynamite blasting, mostly associated with coral reef
habitats. Bryceson (1978a) reported that repeated blasting over a long period of
time has meant the destruction of extensive areas of coral reef and the decline
of their fisheries' productivity. The livelihood of artisanal fishermen who
employ more traditional methods is threatened. Bryceson (1978a) also reported
that spear-fishing had been banned in most countries of the region owing to its
damaging effects on reefs and on populations of particularly vulnerable species.
For the same region, Kayambo (1988) points out that depletion of the mollusc
population as a result of its intensive collection for export and sale to
tourists has been a cause for concern.
In the coastal zone of western Africa, in response to increasing demands for
fish and fish products, trawling now prevails in areas formerly dominated by
traditional fishermen. However, these operations are largely unregulated (or do
not conform to regulations where they exist), with incorrect mesh sizes
resulting in destructive fishing, including the catching of undersized fish
(Ajayi, personal communication).
It is, perhaps, pertinent to mention that on the eastern and western coasts
of Sub-Saharan Africa, the potential for aquaculture development is great and
people are being urged to take it up as a way of increasing overall fish
production. However, experience from its limited practice shows that the
potential for environmental degradation (e.g. associated with clearing
mangroves) is also great.
Mining of sand (siliceous and calcareous), gravel, and other construction
materials (e.g. Iimestone) from estuaries, beaches, or the nearshore continental
shelf is common (Ibe 1982, 1987a,b; lbe and Quelennec 1989) in the coastal
states and islands of Sub-Saharan Africa. The mining of sand and gravel from
coastal rivers and particularly from estuaries tends to diminish the amount of
fluvial sediment input to the coastline, thereby accelerating shoreline retreat.
Sand extraction directly from beaches seriously depletes the sediment pool
available, and beach retreat is either induced or accelerated. Dredging of sand
from the inner continental shelf is an obvious cause of beach erosion in Africa.
This is because the beaches along these coasts exist in dynamic equilibrium with
the nearshore continental shelf. Therefore, dredging of sand/gravel for
replenishment, land reclamation, or other civil engineering construction from
the shore area or, for that matter, anywhere else within the dynamic system
inevitably disrupts this equilibrium and enhances shoreline retreat. Countries
where this problem has been documented include Liberia, Sierra Leone, Cote
d'Ivoire, Nigeria, Mauritius, Tanzania, Kenya, the Seychelles, and Mozambique
(Ibe et al. 1983; Ibe 1986c; Ibe and Quelennec 1989; Bryceson et al. 1990).
Besides the increased threat of erosion, the mining of construction materials
from the coastal zone has a tendency to disrupt fragile ecosystems such as coral
reefs and mangroves and affect their productivity (Ibe 1982; Ibe et al. 1985).
Lead-silver ores were quarried in Kinangoni, Kenya, and were a cause for
concern as regards metal pollution, so that the quarries had to be closed
The exploration, exploitation, refining, and transportation of oil and gas in
Sub-Saharan Africa, although contributing to economic development, bring
worrying problems because these activities routinely contribute a variety of
pollutants to the coastal zone and oceans. These include hydrocarbons from
occasional spills but, perhaps more importantly, from chronic low-level releases
associated with leaking valves, corroded pipelines, ballast water discharges,
and production water effluents. Drilling fluids contain diesel and some toxic
chemicals that cause pollution. Heavy metals, particularly vanadium and nickel,
are introduced through oil-field operations and are known to affect life forms.
Another impact of oil production is the initiation or exacerbation of
subsidence in the fragile coastal zone. The main effect of fluid extraction is
the reduction of fluid pressure in the reservoir, thus leading directly to an
increase in the "effective stress" (or grain to grain stress) in the
system. Compaction results and the sedimentary basin subsides (Cooke and
Doornkamp 1974). The subsequent progressive inundation of the coastline results
in accentuated erosion. Ibe et al. have documented this phenomenon in Nigeria's
oilproducing Niger delta (Ibe et al. 1985; Ibe 1988b).
In oil-producing coastal states, a network of canals for hydrocarbon
exploitation and transportation, on or near the coast, constitutes a visible
structural modification of the coastal zone that has adverse effects on
As stated elsewhere, perhaps the greatest problem in the coastal zone arises
from development activities linked with coastal settlements. Coastal towns are
by far the most developed in Sub-Saharan Africa and, by implication, the
location of residential, industrial, commercial (including harbour and port
construction), agricultural, educational, and military facilities in the coastal
zone is high (Ibe 1988a, 1989). The increasing awareness of the
revenue-generating potential of tourism has also led to increased construction
of tourist facilities on beaches along the coast. Construction activities in the
coastal zone loosen the sediment binding by removing the surface revetments and
increasing rainwater runoff. Thus soil erosion is enhanced. On the other hand,
structures constructed on the coast, by strengthening the soil, may lead to
decreased sediment supply to the shoreline. The opposite problems of increased
siltation and sediment starvation along the coast result, depending on the local
The pollution caused by these settlements and the accompanying development
activities threatens to make nonsense of the concept of sustainable development.
The pollution results primarily from raw or insufficiently treated domestic
sewage and from untreated toxic and deleterious wastes from industries, which
generally discharge directly into rivers, estuaries, and the nearshore ocean.
Preliminary results from pollution-monitoring projects instituted by United
Nations agencies, including the Intergovernmental Oceanographic Commission of
UNESCO in Eastern and Western Africa, show that pollution by pathogenic
organisms, pesticides, chemical fertilizers, and petroleum hydrocarbons is
widespread, while metal pollution occurs as hot spots close to industrial sites.
Solid matter (litter) from industries, households, shipping, and the tourist
trade poses a problem of an unsightly and irritating nature, but it also has
serious public health implications.
The construction of ports, harbours, and piers for national and international
trade has a direct negative impact on the environment. This is because, for the
most part, these structures lie perpendicular, or nearly so, to the littoral
zone, thereby causing acute down-drift erosion. This problem has been documented
in Benin, Togo, Nigeria, Liberia, Ghana, Cote d'Ivoire, South Africa, Tanzania,
and Somalia, among others. In most of these cases, attempts at solving the
harbour-induced erosion have further exacerbated the problem (Ibe 1986a,b).
Increased clearing of coastal vegetation at construction and mining locations
or for the establishment of agricultural farms or the expansion of settlements
leads to increased surface runoff and makes the exposed area extremely
vulnerable to mass movement and to erosion by winds, currents, and water. Large
areas of mangroves have been cleared in Kenya, Tanzania, Ghana, and Mozambique
for the production of salt by evaporation (Ibe 1987a; Semesi 1988). In
Mauritania, Guinea, Sierra Leone, Liberia, Togo, and Angola, open peat mining in
littoral zones also contributes to the destruction of vegetation and the
acceleration of coastal erosion. The clearance of mangroves is particularly
serious because mangroves, in addition to serving as windbreaks, provide
excellent spawning and nursery grounds for a variety of coastal organisms,
including fish, crustaceans, and molluscs. The loss of mangroves therefore has
serious implications for the productivity of coastal ecosystems.
An additional possible problem in coastal areas relates to the expected
effects of global warming on shallow ocean and coastal zones, in particular the
impact of the associated rise in sealevel. The negative implications of global
warming, if they occur, will be considerable for natural and man-made
ecosystems, human and animal health, and the spatial and temporal
characteristics of natural and human resources (Ibe 1989; Ibe and Ojo 1993; Ojo
1992; Tobor and Ibe