Population densities in coastal urban centres in Central African countries are increasing under the dual pressure of population growth and migration. Major coastal cities include Douala in Cameroon (population 1.6 million in 2000) (UNCHS 2001), and Libreville in Gabon (population approximately 400 000 in 1993, around 50 per cent of the total population of Gabon) (World Bank 1997). Migration to the coast is prompted by opportunities for agriculture (fertile soils and favourable climate) and employment (large number of industries based on the coast). The resulting conversion of natural habitat to urban settlements and agricultural plantations, together with poor resource management practices inland, has accelerated rates of coastal erosion and this is now a significant problem in Central Africa. The rate of coastal erosion in Gabon, for example, is reported as having reached around 10 m per year as a result of clearance of mangrove forests (ESA-ESRIN 1996). Erosion is accelerated by construction of dams upstream of the coastal zone. Dams reduce the sediment load in rivers reaching the coastal areas and control their flow patterns, thereby increasing their erosive potential.
Development of coastal infrastructure and poor design and management of coastal cities lead to clearance of natural, stabilizing vegetation and increased exposure to wind and water erosion, thus contributing to destabilization of the sands and soils in the coastal zone. Mining of dunes also destabilizes the coastal zone and enhances the potential for erosion by changing patterns of erosion and deposition. Eroded material is washed out to sea where it settles out along shipping routes which then have to be dredged to prevent grounding of ships, particularly oil tankers (ESAESRIN 1996).
In oil producing states, the development of canals for oil transportation is an additional modification to the coastline that has contributed to altered patterns of erosion and accretion of material.
Coastal erosion also renders Central Africa's coastal settlements and economic activities more vulnerable to sea level rise resulting from global climate change. Impacts include intrusion and contamination of freshwater sources by seawater, flooding, damage to infrastructure and displacement of populations. Cameroon and Gabon have low-lying lagoonal coasts which support large and growing populations, as well as some unique habitats for fisheries and waterfowl habitat. Sea level rise would aggravate existing problems of coastal erosion and increase the risk of saltwater intrusion into surface and groundwater resources (IPCC 1998).
Cameroon has signed the Declaration for Environmentally Sustainable Development of the Large Marine Ecosystem of the Gulf of Guinea (Accra Declaration), pledging political commitment to environmentally sustainable development in the Gulf of Guinea. One means of enhancing environmental conditions in the Gulf is to establish ICZM plans and institutions to implement policy at national level. Another is to increase existing efforts to prevent and mitigate the effects of coastal erosion and sea level rise, funded by international donor agencies and to be implemented within the framework of the Gulf of Guinea Large Marine Ecosystem Programme (see 'Enhancing coastal and marine environmental quality in Western Africa' and Box 2c.5). The Accra Declaration calls for improved sharing of information and coordination of activities between member countries (Cameroon, and the Western African States of Benin, Côte d'Ivoire, Ghana, Nigeria and Togo). The Declaration was signed in 1998, but is not legally binding and progress has been slow. Three MPAs have been established along the Central African coast with the aim of protecting areas of natural habitat from modification, overharvesting, and pollution (WCMC 1999). As elsewhere in Africa, lack of resources and weak institutional structures contribute to frequent infringement of MPAs by commercial and artisanal operations.
|Box 2c.5 Enhancing environmental quality in the Gulf of Guinea|
|Source: UNIDO 2000|