Quantifying the impacts of gully erosion on farmers' livelihoods in the Shafe catchment, southern main Ethiopian Rift: a multi-method approach

Abstract

Like many areas along the border of the main Ethiopian Rift, the Shafe catchment is severely affected by gully erosion. Many earlier studies hypothesized that this can lead to important crop yield losses and, by extent, other socio-economic impacts. Nonetheless, as in other regions, these effects remain poorly quantified and understood. This research aims to quantify and understand these impacts, a critical step for designing effective and targeted mitigation measures. Given the challenges of accurately quantifying these impacts, a multi-method approach was employed. Household interviews were conducted with 171 randomly selected farmers, each having at least one gully-affected plot, to gather insights on perceived impacts, the allocation of uncropped buffer zones near gullies, and crop desiccation effects. Drone mapping of 85 gully-affected plots was carried out to quantify land losses due to gullies. Daily soil moisture measurements were recorded at varying distances from the gully edge (1m, 5m, 10m, 20m, 25m, and 40m). To quantify crop yield reduction, sorghum, wheat, and haricot bean samples were collected from gully-affected plots over two different seasons, with grain and biomass yields measured. Composite soil samples were also collected and analyzed to determine whether crop yield differences may be linked to soil nutrient contents. The preliminary results indicate that farmers experience direct losses of cropland, reduced crop yields due to a combination of factors, and the need for buffers around gullies as the most significant impacts of gully erosion. Soil moisture analysis indicate significant variations across depth and distance from the gully, with relatively higher moisture levels recorded at 40 m compared to closer distances, highlighting reduced moisture availability near the gully. Such variation in soil moisture corresponds to the observed crop yield trends, which increase with distance from the gully. Among the crop samples collected, sorghum showed the highest sensitivity to desiccation (from 0.1 kg/m² at 1 m to 0.47 kg/m² at 40 m). These preliminary results underline the significant impacts that gully erosion can have but also enhance our understanding for the development of more feasible, site-specific mitigation strategies.