Widespread erosion of river islands in the Sichuan Basin revealed by satellite observations over the past decade

River islands are key indicators of fluvial geomorphic change, yet knowledge of their evolution is largely confined to single case studies. This study presents the first regional, long-term (2016–2024) quantitative assessment of river island dynamics. Using time-series Sentinel−2 and Landsat imagery and the Modified Normalized Difference Water Index (MNDWI), we monitored 15 typical islands in China’s intensely dammed Sichuan Basin. Our results reveal a dominant trend of erosion, a degradation coupled with a complex ecological response. Furthermore, our analysis confirms that erosion is highest downstream of dams, while island stability is enhanced by the backwater effects from dams further downstream. Our findings provide critical macroscopic evidence of cascade dam impacts and a scientific basis for predicting island stability in regulated basins.