Soil conservation efficiency assessment based on land use scenarios in the Nile River Basin

Soil conservation is one of the most important ecosystem services, as it has a positive impact on soil fertility and land productivity. Although soil conservation includes multiple facets, existing research on soil conservation has rarely considered the combination of soil erosion and sediment within its analysis. In this context, this paper uses the Revised Universal Soil Loss Equation (RUSLE) and the Sediment Delivery Ratio (SDR) module of Integrated Valuation of Ecosystem Services and Tradeoffs (InVEST) to develop a Soil Conservation Efficiency Index that accounts for both soil erosion conservation efficiency and river sediment transport conservation efficiency. A natural growth and reforestation scenario of land use change was applied and modelled with the Nile River Basin from 2010 to 2100. Three main results were obtained: (1) From 2000 to 2010, grassland increased by 4.34%, and the forest decreased by 4.91%. (2) From 2000 to 2100, soil conservation presents a declining tendency in the two scenarios, and the soil conservation amounts based on soil erosion and sediment were 1550.48 ± 177.12 and 100.93 ± 6.24 (t ha⁻¹ y⁻¹) in a natural growth scenario, respectively, and 1576.78 ± 63.21 and 104.41 ± 0.30 (t ha⁻¹ y⁻¹) in a reforestation scenario, respectively. (3) It was found that the reforestation scenario was the most effective. With soil erosion conservation efficiency being most effective in the first fifty years, and the river sediment transport conservation efficiency being more effective from 2010 to 2100. Overall, when reducing the conversion rate of forest land by 0.5 times and increasing the rate of conversion to forest by 0.5 times, the effect of land use changes to river sediment transport conservation efficiency has a longer-term effect than changes to soil erosion conservation efficiency.