Method-dependent assessment of long-term soil erosion on the Loess Plateau

Differences between classification-based and quantitative approaches may affect interpretations of regional soil erosion patterns and long-term changes. Using Google Earth Engine, we compared the classification-based approach derived from the Standards for Classification and Gradation of Soil Erosion (SL 190-2007) with the Chinese Soil Loss Equation (CSLE) across the Loess Plateau, China, from 2000 to 2025. The comparison covered erosion intensity, spatial distribution, differences among land-use types, rainfall erosivity ranges, slope classes and fractional vegetation cover (FVC) classes, and erosion-grade transitions. Annual paired comparisons accounted for temporal autocorrelation and multiple comparisons. Soil erosion intensity showed marked spatial heterogeneity, with higher erosion grades concentrated in Qinghai, eastern Gansu, central Shaanxi, and along the Shaanxi–Shanxi border. Both approaches indicated an overall decline in erosion intensity but differed substantially in the areas assigned to individual erosion grades. Compared with SL 190-2007, CSLE mapped larger areas in the lowest and highest erosion grades, with differences of 8.57 × 10 4 and 2.33 × 10 4 km 2 , respectively. Grassland and cropland were the dominant land use types on the Loess Plateau, and intermethod differences in erosion-grade area proportions were greatest for grassland. Across all slope and FVC classes, CSLE estimated significantly lower proportions of area affected by mild or more severe erosion (Holm-adjusted p < 0.001). Despite broadly similar patterns of erosion mitigation during 2000-2010, CSLE identified increases in erosion grade across 11.56% of the assessed area, mainly in northern Ningxia, southern Inner Mongolia, and the Loess Hilly-Gully Region. During 2010-2025, erosion intensity declined overall, but CSLE identified increases in erosion grade across 9.01% of the assessed area, mainly in eastern Inner Mongolia, Ningxia, and northern Shaanxi. Assessment-method choice can influence erosion-grade mapping and the identification of areas requiring conservation attention, even when regional erosion trends are consistent. SL 190-2007 supports rapid regional screening and assessment of long-term changes in erosion grades with fewer input variables, whereas CSLE provides quantitative soil-loss estimates for assessing spatial and temporal variation and informing conservation planning when sufficient input data are available.