Assessment of soil loss dynamics in a wet tropical ecosystem: the case of the Sanaga basin at Nachtigal, Cameroon

Abstract

Soil erosion threatens the planet, compromising natural resources and sustainable development, with irreversible consequences on fertility loss, water pollution, and biodiversity depletion. In Cameroon, the Sanaga basin at Nachtigal harbors strategic resources for the country’s development (drinking water, hydroelectric dam), which suffer the harmful effects of erosion; hindering the country’s socio-economic progress. This study aimed to evaluate the spatial and temporal dynamics of soil loss in the Sanaga basin at Nachtigal from 1980 to 2023. The method employed is based on the Revised Universal Soil Loss Equation (RUSLE). The results show that between 1980 and 2023, forests decreased by 15% among the five land use types, giving way to urbanized areas, cultivated lands, and bare soils. The analysis of soil loss reveals a significant increase in erosion rates, ranging from 0 t/ha/year in non-eroded areas to 1989.82 t/ha/year in the most affected. The average soil loss rate increased by 173.8%, rising from 25.17 t/ha/year in 1980 to 68.97 t/ha/year in 2023. Notably, more than 33% of the basin’s area has experienced intolerable soil loss rates exceeding 10 t/ha/year. Steep slope areas, areas with unsustainable agricultural practices, and areas with high rainfall erosivity represent the majority of the basin’s area affected by intolerable soil loss. The AUC (Area Under the Curve) method confirms the high accuracy of the erosion susceptibility maps, with a score ranging from 0.81 to 0.85. The maps generated from the study results are valuable tools for the implementation of soil and water conservation strategies in this region.