Century-long spatiotemporal variation in cropland soil erosion and the roles of anthropogenic factors in the Tuojiang River Basin, China

Abstract

Evaluating the long-term soil erosion dynamics and their responses to anthropogenic forcing at the regional level is crucial for assessing the impacts of soil conservation efforts and informing future policy development. The soil erosion issue is particularly severe in southwestern China due to its large hilly areas and extensive human activities. However, due to the lack of long-term records, there has been insufficient evaluation of the historical variations in cropland erosion across the spatial scales of decades and centuries, which hinders a comprehensive understanding of the main drivers and their effects. By using the Revised Universal Soil Loss Equation model in combination with remote sensing-based multisource data, the spatial and temporal evolution of cropland soil erosion in the Tuojiang River Basin (TRB) in China from 1911 to 2017 is assessed in this study. We also employ geographically and temporally weighted regression (GTWR) to assess the spatial and temporal heterogeneity of the anthropogenic factors impacting cropland soil erosion in the TRB from 1911 to 2017. The study results indicate that (1) in the past century, an average of 77.70% of the TRB has exhibited a slight soil erosion level, with the upper stream experiencing a higher rate. (2) The amount of soil erosion increased slightly from 1911 to 1960, dramatically increased by 70.07% from 1960 to 1980, and then decreased by 34.75% from 1980 to 2017. Cropland soil erosion mainly occurred in the upper stream, but it has been expanding to the downstream region since 2000. The high rate of cropland cultivation in the densely populated upper reaches is the main cause of accelerated erosion. (3) The increase in cropland soil erosion has primarily been driven by population growth and cropland expansion with contrary effects, reflecting a complex interplay of diverse natural and anthropogenic mechanisms. Spatiotemporal differentiations in the influences of both factors became evident with the economic reform and implementation of ecological conservation policies that have been occurring since 1980. These results can provide valuable insights for decision-makers for better understanding the long-term evolution of cropland soil erosion and the implementation of targeted soil conservation measures.