Spatio-temporal evolution of sloping farmland and identification of its erosion risk management and control zones in the Three Gorges Reservoir Area, China

Abstract

Sloping farmland in the Three Gorges Reservoir Area (TGRA) is crucial for national food and ecological security. In this study, methods such as terrain gradient classification, kernel density estimation, and erosion risk identification model were used to analyze the spatio-temporal evolution and influencing factors of sloping farmland in the TGRA during 1990–2020, and its erosion risk control areas were identified. The sloping farmland in the TGRA exhibited spatial distribution characteristics of more in the central and western regions, less in the eastern region, with a high degree of fragmentation. It was concentrated in areas with slopes of 8–25° and altitudes of 200–1000 m, accounting for approximately 63% and 80% of sloping farmland, respectively. In the last 30 years, the distribution of sloping farmland with slopes $>$15° and altitudes $>$1000 m has gradually decreased and shifted to areas of 8–15° and 400–800 m, respectively. The sloping farmland has decreased by 343.93 km², mainly converted into forest land, grassland, paddy field, and construction land. Slope and altitude were the main natural factors affecting the spatio-temporal evolution of sloping farmland, while the urbanization rate and disposable income of rural residents were the key human influence factors. Sloping farmland above the high-risk level of erosion was mainly distributed in counties such as Wuxi, Kaizhou, Wushan, Fengjie, Yunyang, and Wanzhou, concentrated in the terrain gradient area with slopes of 10–35° and altitudes of 200–1000 m, with the most distribution at 15–25° and 200–400 m. For these high erosion risk areas, prioritized regulation should be carried out for sloping farmland. These findings can optimize the use of sloping farmland resources, strengthening the prevention and control of erosion risks, and promoting the sustainable agricultural development.