Natural Resources and Environmental Conservation
S. W. Fetters
Nigeria is very conscious of the need to fully utilise her natural resources. Renewable resources such as soils, water and forests, are threatened. They have to be managed to ensure optimal use, to the greatest benefit of the citizenry and in perpetuity. Non-renewable resources particularly need to be managed so that they can be utilised for the longest time possible. Sustainability is, therefore, the essence of natural resources conservation (Mabogunje, 1988).
Nigeria's diverse natural resources endowment derives from the nation's three principal ecological zones, namely: the highly humid coastal zone in the south; the humid and sub-humid areas in the middle parts of the country; and the semiarid regions in the north. Although divisible into several ecosystems, this tripartite ecological subdivision is adequate for the present purpose, because it broadly corresponds (from south to north) with the tropical rain-forest, the savannah, and the Sudano-Sahelian regions of Nigeria.
SOILS AND LAND USE
As already shown in the section on biotic resources, Nigeria has a wide diversity of soils under different ecological conditions and with different levels of fertility. On these soils depend agriculture and related primary production activities. This makes soil resources a subject of importance in the drive towards natural resources conservation in the country. The traditional land tenure system and soils management practices involving shifting cultivation, slash-and-burn processes and traditional tillage method ensure the maintenance of soil physical properties and the sustainability of productivity.
However, bulldozing and mechanical tillage (ploughing) subject Nigerian soils to devastating processes such as erosion and the formation of hardpans. In the Sudano-Sahelian region, overgrazing poses a serious additional threat contributing to desertificalion and wind erosion. This came to a peak during the recent prolonged drought of about 10 years from (1970 to 1980) (Qadzama, 1991). Defores- tation, whether resulting from the demands of ani- mal husbandry, the cutting of wood or the incidence of bush burning, usually produces soil degradation and infertility.
Erosion poses the greatest threat to Nigerian soils, and affects over 80 per cent of the land (NEST, 1991). Wind, sheet, gully and beach erosion affect different parts of the country in varying intensities, but attention will focus here on erosion menace to agricultural land. While wind erosion is confined to the arid north, sheet erosion is ubiquitous throughout the country. Areas most prone to sheetwash are where farming has cleared the original vegetation, and the soils being impoverished, become scrubland. But gully erosion is by far the most alarming type of erosion in Nigeria, because it often threatens settlements and roads. Although it affects a small fraction (less than 0.1 per cent) of Nigeria's 924,000 sq. km of landmass, gully erosion claims large amounts of public funds annually for remedial action.
Gullying is particularly severe in the loose sandy terrain of southeastern Nigeria where torrential rains prevail. The usual causes of gully erosion, which need to be avoided, include bad farming practices such as improper tillage and monoculture; quarrying for sand and gravel; lack of road drainage; mischannelling of storm runoff; deforestation, especially of watersheds; incision of rural foot paths leading to stream water supply sources, and the lack of road maintenance. For anti-erosion measures to succeed, these environ- mental abuses must be discouraged, especially through public enlightenment. Soil and land conservation must, however, transcend the prevention of the above abuses, most of which arise from the innocent use of soils for peasant cultivation.
Mining and mineral processing are equally devastating to land and water supply. Open-cast tin mining on the Jos Plateau has produced pits and mine tailings which despoil the land- scape. Soil conservation, therefore, includes the reclamation of mined land and quarry sites. Coastal environmental protection is also a vital subset of land resources management, because Nigeria occupies 800 km of the Equatorial Atlantic sea-board. The Bar Beach on the Victoria Island ocean front is threatened by rapid beach erosion. Also, because of petroleum production, the Niger Delta has been most vulnerable to oil spillage.
Shoreline erosion and flooding constitute major coastal hazards that have threatened or destroyed settlements, harbour works, oil production facilities, and coastal agricultural and recreational land. Annually, some 13m to 30m of the Nigerian coast land is lost to beach erosion caused by both natural and human agents. Among the natural causes of beach erosion are large storm waves; destructive littoral currents; the low-lying microtidal and mesotidal nature of the coastline; the easily eroded nature of coastal sediments; strong tidal currents and global eustatic sea-level rise. Human actions that have exacerbated the destructive impact of nature along the shoreline include harbour protection structures (e.g. Victoria and Escravos Beaches).
While nourishing one segment of the shoreline, beach protection structures often starve other parts of the coast line of sediments, thus triggering erosion. The coastline is also affected by sand dredging, and the damming of rivers in the hinterland which hitherto had supplied enough sediments to the coast to replenish what is lost to the forces of nature.