Climate Change and the Management of Natural Systems in Cameroon

12. Management of Observed and Anticipated Physical Effects of Climate Change on Lake Chad

263 Chapter Twelve Management of Observed and Anticipated Physical Effects of Climate Change on Lake Chad Summary Global climate change is likely to lead to increased water temperatures and evaporation in many lakes. This certainly will have physical and biological effects on lake ecosystems. The chapter appraises the guidelines established for the management of the Lake Chad basin with a focus on the observed and anticipated effects of climate change and anthropic activities on the physical resources of the basin. It presents an overview of the basin water resources and the management lacunae. The chapter finally concludes that current management strategies do not fully accommodate observed and anticipated effects of climatic change on the availability of water resources in the lake basin. It therefore designs a strategy for the basin that can buffer the adaptations to climate change effects. Key Words: Lake Basin, climate change, water resources, mitigation, integrated river basin management (IRBM), ecoregion conservation (ERC). Introduction Increased mean surface temperatures are likely to lead to increased water temperatures and evaporation in many lakes (Schindler, 2001; Zinyowera et al., 1998). If rainfall does not increase enough to compensate, this could lead to reductions in outflow and/or lake volume (Tyedmess and Ward, 2001). Severe climatic conditions have caused the gradual shrinkage of some lakes, for instance, Lake Ngami in South Africa. The African Great Lakes are particularly sensitive to climatic effects on outflow, as current outflow is small, that is, only 6% of water input to Lake Tanganyika leaves as riverine outflow, and even minor declines in rainfall of 10 to 20 % are expected to completely close these basins (Bootsma and Hecky, 1993). Increasing temperatures coupled with reducing rainfall and encroaching sands from the Sahara Desert are gradually reducing the size and depth of Lake Chad (Ngwa, 1979). The size of this lake may in future be reduced more quickly if the 264 process of river capture now taking place on the ridge separating the Mayo Kebi and River Logone is completed (Morin, 1982). Ssentogo (1979) observed that there is less ecosystem stability in temporary fluctuating lakes such as Lake Chad. It is a closed lake which is increasing shrinking because of much evaporation due to high temperatures. The increased salinity of the lake has resulted in more blue green algae production. The threat to lake Chad, which in effect is a threat to the economic life of the inhabitants of the basin is the grave concern of the countries sharing the lake, that is, Nigeria, Niger, Chad and Cameroon (Figure 1) Figure 1: Location of Lake Chad and the Lake Chad Basin. Dotted lines are lake basin limits. The paper reviews the Lake Chad basin water resources, assesses the anthropogenic threats to their sustainability under climate change conditions, the management guidelines established by member countries of the Lake Chad Basin Commission (LCBC) with a focus on the observed and 265 anticipated effects of climate change, and identifies the management models that can mitigate climate change impacts. Research Methods The principal data sources were secondary. Project documents of the Lake Chad Basin Commission and other related archival material constitute the basis of the review and appraisal. These were complemented by field observations which were limited to the Cameroon portion of the basin. Aerial photographs produced by the National Geographic Institute for the study area were also used to describe changes in water dependent land use patterns. Finally, informal interviews involving a two-way conversational method were used to obtain data from local resource users and development experts working in the Cameroon portion of the basin. A limitation of the study is the lack of up-to-date data on land use changes and hydrometeorology. The Study Area and Problem Background Climatic conditions all over Africa have varied considerably during the Quaternary period of the last million years (Kadomura, 1986; Diamond, 1980, Hamilton, 1982; Hamilton, 1976). These changes can be deciphered in the soils and drainage systems of the present day. Lake Chad, for example, which is less than 8 metres deep for the most part and has been reduced to a little more than a swamp, was about the size of the Caspian Sea, possibly as late as 5,000 or 10,000 years ago (Grove, 1970). The old shoreline can be traced across Bornu in Nigeria and far to the north-east (Figures 2 and 3). The lake must have been over 165metres deep, its waters overflowed...