Spatio-temporal variation of soil erosion and its influencing factors based on RUSLE modelA case study of Guangdong-Hong Kong-Macao Greater Bay Area

Background Soil erosion causes a serious threat to agricultural production and ecosystems. As one of China’s fastest growing urban agglomerations, the Guangdong-Hong Kong-Macao Greater Bay Area (the GBA) has experienced serious soil erosion and significant reduction in land resources in recent years with the expansion of urban land. A deep understanding of the spatial and temporal variation of regional soil erosion may provide theoretical support for the rational development of ecological protection, and soil and water conservation.

Methods Supported by normalized difference vegetation index (NDVI), precipitation data, land cover products and digital elevation model (DEM), the soil erosion modulus in the GBA in 2010 and 2020 were calculated based on the Revised Universal Soil Loss Equation (RUSLE) model. Localization and modification of the calculation method for each factor have been conducted to obtain accurate soil erosion results in 2010 and 2020. Spatio-temporal variation of soil erosion were analyzed by layer overlay and change matrix, and the relationship between soil erosion and elevation, slope gradient, land use type were explored by statistical analysis.

Results 1) The soil erosion modulus of the GBA in 2010 and 2020 were 13.24 and 8.74 t/(hm²·a), respectively, showing a notably decreasing trend with a percentage of 34% in recent 10 years. The soil erosion intensity in 2020 showed a continuous increasing trend in slight and light erosion, and soil erosion showed an improving trend. 2) Soil erosion in the GBA demonstrated spatial characteristics of low erosion intensity in the central region, and severe erosion in the surrounding areas. From 2010 to 2020, the soil erosion intensity in the GBA was relatively stable, with 88.2% of the areas showing no changes in erosion intensity. The areas with worse soil erosion were mainly concentrated in the northern, southwestern and eastern coastal areas of the GBA. 3) Soil erosion modulus firstly decreased and then increased with the increase of elevation, and the most severe soil erosion occurred in areas with altitudes greater than 1000 m. The steeper the slope, the greater the erosion intensity. Grass land and cultivated land were severely eroded land use types, with soil erosion modulus of 13.96 and 13.43 t/(hm²·a), respectively.

Conclusions Long-term control measures to soil erosion in the GBA have been effective in the past decade, and further attention needs to be paid to the soil erosion prevention and control in areas with steep slope, high elevation, grass land and cultivated land.