Land Degradation Dynamics Under Land Use Land Cover and Climate Change Projection Towards the Appraisal of Potential Soil and Water Conservation Practices in the Gidabo Watershed, Ethiopian Rift Valley Lakes Basin

Abstract

The intricate relationship between land use, climate dynamics, and land degradation profoundly impacts the sustainability of ecosystems and human well-being in Ethiopia. This study, conducted in the Gidabo Watershed (GW) within the Ethiopian Rift Valley Lakes Basin (ERVLB), aimed to assess the long-term land use land cover (LULC), evaluate regional climate models (RCMs), assess land degradation indicators, and propose management alternatives. To address these objectives, multidisciplinary approach integrating, remote sensing, geospatial analysis, statistical metrics and hydrological modeling were used. The study identified nine major LULC classes i.e., water body, grass land, forest, agriculture, bare/barren land, built-up, agroforestry, shrub and marsh land. The watershed experienced significant LULC changes between 1985 and 2021, predominantly driven by agricultural expansion at the expense of forest, shrub, and grasslands. Future (2035 and 2050) projections using a hybrid Multi-Layer Perceptron (MLP) and Cellular Automata-Markov chain (CA-MC) model indicated further agricultural expansion, accompanied by declines in forest and grasslands. Furthermore, the study evaluated 11 CORDEX-Africa RCMs and their mean ensemble performance, revealing varied accuracies in reproducing rainfall and temperature patterns over GW from 1991 to 2005. The observed climate trends indicated a significant declining rainfall (-13.38 mm/year) and warming temperatures, with future projections (RCP4.5 and RCP8.5) showing consistent temperature increases. Additionally, the study investigated the impact of LULC and climate change on surface runoff and sediment yield using SWAT model. The results revealed notable increases in surface runoff and sediment yield attributed to LULC changes. Whereas, climate change alone exhibited a diverse influence, with both increases and decreases in surface runoff and sediment yield. Similarly, the combined effects of LULC and climate change demonstrated that certain scenarios led to the increases in surface runoff and sediment yield, while others reduced these processes. This might be attributed to the offset of runoff and sediment reduction by climate change. Soil erosion rates were found to be high, particularly most of the southern and eastern parts of the watershed will generate the highest amount of surface runoff and sediment yield in to the future. Addressing these concerns, soil/stone bund, terracing, contour farming, and reforestation practice can significantly reduce the annual sediment yield in the future. The land degradation neutrality (LDN) assessment from 1985–2003 to 2003–2021 revealed land productivity decline, land cover degradation, SOC loss, and the expansion of land degradation trajectories by 26%. Overall, the findings provide valuable information for stakeholders.