Climate Change and the Management of Natural Systems in Cameroon

7. Climate Change and Management of Riverine Ecosystems

141 Chapter Seven Climate Change and Management of Riverine Ecosystems Summary Global warming has distorted rainfall and temperature patterns across the globe and this is equally being felt in Cameroon. It has been observed to reduce rainfall, increase the frequency of extreme events such as droughts and floods, and therefore surface and groundwater resources in the main watersheds of the country. This chapter uses a combination of field observations and secondary data to overview the underlying physical processes of freshwater systems in Cameroon that are most vulnerable to change and to determine how these changes might affect aquatic life. It concludes that aquatic life in river systems are sensitive not only to water temperature, volume and flow, but also to variability in these factors. The variety of changes to be displayed by rivers in response to global climate change are anticipated and data and strategies for designing and managing river systems that will allow them to withstand and to adapt to climate change are provided based on observed and predicted effects of global climate change. Finally, general suggestions are presented for designing and managing river fisheries to increase resistance and resilience to climate change. Keywords: Climate change, physical processes of freshwater systems, river fisheries, resistance, resilience, climate change impacts, management. Introduction Freshwater ecosystems have been critical to sustaining life and establishing civilizations throughout history. Man relies on them for drinking water, agriculture, transportation, energy production, industrial processes, waste disposal and extraction of fish and other products. Freshwater fishes account for over 25% of the living vertebrate species. (McAllister et al; 1997). Temperature and rainfall are the main conditions which sustain the growth and development of biodiversity. Because freshwater ecosystems are sensitive not only to water temperature, volume, and flow but to variability in these 142 factors, rivers, lakes and wetlands are expected to display a variety of changes in response to global climate change. This chapter uses a combination field observations and secondary data to overview the underlying physical processes of freshwater systems in Cameroon that are most vulnerable to change and to determine how these changes might affect aquatic life. The purpose is to provide data and strategies for the design and management of river systems in order to enable them to withstand and/or adapt to climate change. Ecological and Socio-Economic Setting Cameroon has a total land area of about 473,440km2 with a population of 17 million and a growth rate of 2 percent. Agriculture employs 70 per cent of labour force and contributes 44 percent to the Gross Domestic Product. The country has three climate regions (Figure 1). These are the humidwet equatorial region in the South, a montane equatorial climate in the West, and a dry semi-arid climate in the North. Rainfall decreases from South to North. Figure 1 presents the actual rainfall and temperature regimes. There are high year-round temperatures and the weather is controlled by equatorial and tropical air masses. It has two major seasons, a dry season and a wet season. Most of the rain occurs between April and October. Rainfall is variable and unreliable (Ngakfumbe, 2001) and floods and droughts occur frequently. The Southern part of the country has an average temperature of 250 C while the northern regions between 270 C and 340 C. The northern parts have seasonal rivers. These dry up during the dry season. The southern regions have abundant surface water resources. These drain into the Congo basin; Niger basin and the Gulf of Guinea while the northern rivers but for the Benue River drain into the Chad basin. The freshwater life is extremely varied. There are about 550 species of freshwater fish composed of over 47 families and 148 types. The most important are the Cyprinidae (50 species). The Circhlidae family is well represented by Tilapia spp. The Mormymidae include 50 different species. The Synodontae are composed of 30 species and present in almost all rivers. The Citharindae family is represented by 16 species. Table 1 presents an inventory of fish in the Manyu River and its tributaries. A case study was 143 made of the Manyu River basin (Figure 3) in order to obtain data on the ecological and socio-economic setting of the study. Fishing contributes to local diets and the trading economy of villages within and around riverine areas (du Feu, 2002). In the Manyu River, fish breeding and migration occur in the small tributaries during the dry...