Contribution by farmers' survival strategies to soil erosion in the Linthipe River Catchment: implications for biodiversity conservation in Lake Malawi/Nyasa

Sediment discharge into Lake Malawi is threatening its ecological importance, thereby inflicting serious socio-economic consequences upon people dependent on this ecosystem. The discharge is attributed to high rates of erosion in the Lake's catchment, principally occurring on agricultural land. This study examines how survival strategies, such as expansion of cultivated farmland and use of low fertilizer application rates, enhance the likelihood of erosion in the Linthipe River Catchment - one of the Lake's important river catchments. As such, it shows that the magnitude of erosion is significantly correlated to the amount of farmland cultivated by estate farmers and smallholders (r = 0.18, P = 0.03, and r = 0.19, P = 0.003 respectively). The low correlation coefficients uphold the long-established fact that physical variables such as soil erodibility (vulnerability of soil to erosion), rainfall erosivity (the potential of rainfall to cause erosion), and topography, also play major roles in erosion processes. Nonetheless they do show that area of cultivated land contributes to erosion. Additionally, the study shows that yields of important crops such as maize and tobacco are low because of insufficient use of fertilizers. To compensate for the low yields, farmers rely on extending sizes of land that they cultivate thereby exposing more land to erosive forces of rainfall. The study, therefore, concludes that Lake Malawi's biodiversity is under threat. In order to sustain the biodiversity, it is necessary to eliminate the need to increase farmland by means of agricultural intensification that incorporates appropriate soil-conservation measures.