Biogeography: Lakes—African Great Lakes

Abstract The African Great Lakes (AGL) are among the most ecologically and economically important aquatic biomes of the world. They are sources of nutritious fish in a region where malnutrition and poverty levels are high, provide employment to fisher communities, and are sources of water for domestic and urban use, hydropower generation, irrigation and wastewater disposal. Some of the lakes have the highest diversity of endemic freshwater fishes and other organisms on earth. The original biogeography of AGL was molded by geological events. Here we examine how the biogeography of AGL has been altered by activities of a rapidly increasing human population whose growth rate is among the fastest in the world through land use change, fishery exploitation, and climate variability and change. Fisheries exploitation was the first to manifest resulting into a decline and in some cases total disappearance especially of some large inshore fish species which, in some lakes led to enhancement of fish production through introduction of new fish species and cage aquaculture. The impacts of conversion of land to agriculture, deforestation, wetland degradation, urban and hydropower developments were cumulative since the turn of the 20th century and their effects on aquatic ecosystems manifested at different rates through changes in physical and chemical conditions, shifts in algal and invertebrate communities and fish stocks, and proliferation of invasive weeds. Some of the lakes with terrestrial game reserves around them were partly shielded from these changes. Climate variability and change, which intensified after the 1970s, triggered further environmental changes, algal communities shifted from large diatoms to smaller diatoms, green algae, and blue green algae, invertebrates from larger to smaller sized groups, and fish stocks became dominated by small pelagic species. These changes have been more severe in shallower lakes or shallow near-shore areas of deep lakes with high human population growth rates and densities. The changes are expected to continue and should be monitored and managed to avoid reaching catastrophic levels. The countries sharing the lakes should network within and between lakes, nationally, regionally, continentally and globally to mobilize and harmonize information and data, and update it regularly to guide management of lakes.