Potential impacts of agricultural development on freshwater biodiversity in the Lake Victoria basin

Abstract

Abstract The Lake Victoria basin (LVB) and its tributary rivers are a major biodiversity hot spot, containing at least 234 native fish species, 135 native aquatic plant species, and 50 native freshwater mollusc species. Lake Victoria itself is home to around 500 fish species, most of which are haplochromine cichlids. The LVB is increasingly under threat from unsustainable land conversion and the intensification of agriculture. High population growth is driving the expansion of agriculture, urbanization, and freshwater abstractions, which have a profound impact on freshwater biodiversity. In addition, increased demand for agricultural crops from domestic and international markets are likely to lead to larger agricultural operations, further threatening freshwater biodiversity. This study explores these potential future impacts on the biodiversity found in freshwater rivers in the LVB as a result of projected future changes in land use. A newly developed database of land‐use impacts on freshwater biodiversity is introduced, with a focus on ecological community composition data from freshwater habitats under human pressures. Impacts on freshwater biodiversity are then projected under four different scenarios of land‐use change. Results show that land use has a significant impact on freshwater biodiversity. Freshwater biodiversity is projected to be at most risk in sub‐basins in the Tanzanian, Rwandan, and Burundian part of the LVB, such as the Kagera and Magoga/Isonga sub‐basins. Local species richness levels are particularly affected in the Magoga/Isonga sub‐basin in Tanzania, with an average loss of 10.8% across all scenarios. Model results show the potential to identify broad spatial patterns of likely threats and pressures on freshwater ecosystems under different socio‐economic futures. The analysis of these patterns, where they are consistent and where they differ, can support the production of policy that strives to find the optimal balance between development and conservation in an uncertain future.