Climate Change and the Management of Natural Systems in Cameroon

6. Climate Change and Management of Coastal Zone and Marine Ecosystem

115 Chapter Six Climate Change and Management of Coastal Zone and Marine Ecosystem Summary Tropical marine ecosystems are rich in biodiversity and provide a valuable source of protein that supports local economies. They include mangroves, sea grass, vast pelagic systems and coral reefs. Despite the goods and ecosystem services they provide, the coastal zones and marine ecosystems are under human-related stresses, climate change-related stresses and anthropogenic climate change threats. The chapter reviews the marine ecological circumstances at the Gulf of Guinea, available pelagic stocks, fishery potentials of Cameroon and the anthropogenic stresses on the coastal zone and marine ecosystems. It further assesses the anticipated effects of climate change impacts on the systems and makes an overview of the appropriate types of strategies necessary for building resistance and resilience. Finally, the chapter concludes that in addition to designing strategies for building resistance and resilience, it will also be necessary to limit the rate and extent of anthropogenic climate change. Key Words: Climate change, coastal zone, marine ecosystem, resilience, resistance, anthropogenic stress, climate change related stresses. Introduction Cameroon possesses a portion of the Atlantic Ocean. The country is situated at the Gulf of Guinea and has a narrow coastal plain which hardly exceeds 150km in width. The Gulf of Guinea is rich in biodiversity and provides productivity to support human populations. They include mangrove ecosystems and pelagic systems. This marine ecosystem supports local subsistence fishing (craft fishing) as well as international commercial fisheries. The mangrove swamps in the estuarine creek systems act as a filtration system for the estuarine and freshwater. Mangroves offer protection from coastal erosion and trap sediments from terrestrial runoff. These 116 habitats also serve as nurseries for many invertebrates and fish. The complex ecology of mangroves is well appreciated but not well understood. Efforts towards a greater understanding are constantly being challenged as these systems are altered by local anthropogenic stresses and global climate change. The resistance (ability to withstand change) and resilience (ability to recover from change) of an ecosystem determine how well it can deal with stresses. Proper management can enhance resistance and resilience to climate change by alleviating the overall pressures on the system, giving it more flexibility to mobilize its natural defences (Noss, 2001). This chapter reviews the marine ecological circumstances at the Gulf of Guinea, the coastal and marine ecological potentials of the area and Cameroon in particular and the human-related stresses on marine ecosystems. It further assesses the effects of climate change on the systems and makes an overview of the types of strategies that might be adopted to increase their resistance and resilience to climate change. Regional Setting of the Gulf of Guinea and the Study Area The Gulf of Guinea is unique since it displays a zonal coastline just 50 off the equator and this strongly influences the distribution of currents. The distribution of water masses is further modified by large amounts of fresh water from rivers and rainfall while the only sources of high salinity are the Equatorial Undercurrent and the weak South Equatorial Countercurrent. The latter flows across the Atlantic Ocean at about 40 S, bends southward between 100 W and 150 W, and when it finally reaches the African coast at about 150 S its salinity is well below 36% and does not differ much from the waters above (Mazeika, 1968). The Equatorial Undercurrent flows eastward until it encounters Sao Tomé Island where its main part bends southward and reaches the shelf near 20 S off Cape Lopez (Gabon). Its salinity there is still in excess of 36.2% (Rinkel et al., 1966) in contrast to the surface waters which have salinities below 33% off Sao Tomé and well below 30% further inshore. The extent of the areas of low salinities is shown in Figure 1. Off the Congo, salinities of less than 20% extend in a tongue-shaped plume some 50-120 km into the ocean, depending on river outflow. Minimum salinities in the inner Gulf of Guinea vary between less than 25% in winter and 28% in summer. Little is known about the reduction of salinity off Liberia and Ivory Coast but it is likely to be about the same level (Berrit, 1969). 117 Water from the Gulf of Guinea can be traced along the coast by its low salinity and has been shown to reach as far as 170 N, i.e. 200 km north of Cape Verde, during...