Since the beginning of the last century, biological resources in Western Africa have been rapidly degraded and lost through practices such as largescale clearing and burning of forest, overharvesting of plants and animals, indiscriminate use of persistent chemical pesticides, draining and filling of wetlands, destructive fishing practices, air pollution, and the conversion of protected lands to agricultural and urban development. These activities are the results of uncontrolled population growth and increasing poverty, as well as of economic policies and priorities. For example, economic pressures led to concessions being granted to foreign logging companies to exploit Western Africa's tropical moist forests and prices of cash crops, especially in the 1980s, resulted in clearing of large areas of natural habitat for agriculture. Benin, Côte d'Ivoire, Liberia, Mauritania, Niger, Nigeria, Sierra Leone, and Togo all have rates of deforestation of more than 2 per cent per year (FAO 2001). Remnants of forest vegetation are presently found in protected areas in coastal countries. The Upper Guinea forest extends over approximately 420 000 square kilometres, but estimates of existing forests suggest a loss of nearly 80 per cent of the original extent (Conservation International 1999). The remaining forest is highly fragmented and spread across national borders. The forest fragments that remain are under severe threat, mainly arising from slash-and-burn agriculture which accounts for much of the sub-region's subsistence food production.
Savannas are the dominant ecosystems in Western Africa after tropical forests. Like the forests, they also support extremely biologically diverse communities of animals and plants but persistent exploitation for food, fuelwood and other resources from the savanna has resulted in their widespread degradation. For example, the rich and extensive savanna vegetation found in the northern portions of the sub-region has been severely degraded with resultant loss of vegetation cover, fertile top soil and wild faunal species.
Political instability in Liberia, Sierra Leone, and Senegal, has created large numbers of refugees that add further pressure to the threatened forests through resettlement and subsistence agriculture. Political instability also creates economic distress indirectly in the sub-region, resulting in unsustainable resource use and lack of patrolling and enforcement of protection regulations.
Another major biodiversity issue in Western Africa is the loss and degradation of wetlands. Coastal and inland wetlands in Western Africa have been regarded as wastelands constituting habitats for pests and thus representing a threat to public health. As a result of this perception, wetlands in Western Africa have been under constant threat from development activities, especially agriculture and construction of harbours. Draining or in-filling of wetlands changes hydrological regimes so that they no longer provide suitable habitats for wildlife. Untreated effluents from domestic, commercial and industrial sources in nearby settlements have polluted coastal wetlands creating a toxicity risk for flora and fauna.
Rapid urbanization in coastal areas has created a number of very large cities in the sub-region, for example Lagos (Nigeria), Accra (Ghana) and Abidjan (Côte d'Ivoire). These cities surround major coastal wetlands some of which have been degraded by pollution and eutrophication to the extent that they have now become unsightly sources of odour and are biologically unproductive (IDRC 1996). Korle Lagoon in Accra is one such example. Degradation of wetland ecosystem in the sub-region has also been attributed to extraction of woody material for fuel and charcoal production for domestic use and for curing of fish for the market. In Senegal, Salvinia molesta molesta (an invasive waterweed) appeared in the Djoudj Park and delta in 1999 and has since spread to a number of man-made lakes. This is a serious threat to the delta, which is a vital habitat for many migratory species.
Habitat loss is not the only threat to wildlife in Western Africa. The demand for bushmeat is driving high rates of poaching and an international trade in endangered species and wildlife products is also flourishing. A series of surveys of endangered primates in the forest reserves of Eastern Cote D'Ivoire and southern Ghana from 1993 to 1999 document the first recorded extinction of a widely recognized primate taxon, Miss Waldron's red colobus (Procolobus badius waldroni). Hunting rather than habitat loss is considered to be the primary cause (McGraw, Monah & Abedi- Lartey 1998, Oates, Abedi-Lartey, McGraw, Struhsaker & Whitesides 2000).
Drills (Mandrillus leucophaeus) (see Central Africa) are also found in the Cross River area of Nigeria (Gadsby & Jenkins 1998). Like the critically endangered Cross River Gorilla (Gorilla gorilla diehli), this species is found in an area which straddles the international border between Nigeria and Cameroon, as well as the sub-regional border between Western and Central Africa (Oates 2001)
Rural people in Western Africa depend heavily on medicinal plants for their health needs. However, as a result of extensive agricultural practices and annual bush fires, many medicinal plants have been lost at a time when conscious efforts are being made in many countries to promote herbal and traditional medicine.
Other species are threatened by a few invasive species of animals and plants. The Nypa palm, for example, is threatening mangrove forests in coastal Western Africa, and the bracken fern is encroaching on savanna ecosystems. Invasive plants such as these use up available water and nutrient resources and thus deprive native species and reduce biodiversity. The threatened species in Western Africa are shown in Table 2b.15.
|Table 2b.15 Threatened species in Western Africa, 2000|
|Source: IUCN 2000a|