Spatiotemporal Analysis of Soil Salinity‐Induced Land Degradation Using Remote Sensing Techniques

ABSTRACT Soil salinization is a major form of land degradation threatening agricultural sustainability in tropical and subtropical coastal regions. In the current study, a remote sensing (RS) based approach was employed to quantify and monitor soil salinity‐induced land degradation across Haikou, Hainan Province, China, using multi‐temporal Sentinel‐2 MSI imagery combined with field‐measured soil electrical conductivity (EC) data. The analysis integrated several salinity indices to estimate their performance in mapping soil salinity and identifying degradation hotspots. The spatial EC map indicated values ranging from 0.015 to 6.3 dS/m, with elevated salinity concentrated in coastal zones and lower EC values in the central part of the study area. Among all indices, the Normalized Difference Salinity Index (NDSI) exhibited the strongest correlation with soil EC ( R 2 = 0.629, r = 0.793), followed by the Soil‐Adjusted Ratio Salinity (SRSI) ( R 2 = 0.402), while SI1, the Soil‐Adjusted Vegetation Index (SAVI), and SI3 showed moderate‐to‐low relationships ( R 2 = 0.35, 0.30, and 0.25, respectively). The increasing salinity from 2017 to 2024 and the spatial coincidence of high‐EC zones with degraded cropland highlight the accelerating land degradation processes driven by salinization. Furthermore, the temporal analysis of the NDSI from 2017 to 2024 revealed a pronounced increase in surface soil salinity, with mean NDSI values rising from 0.486 in 2017 to 0.591 in 2024, while maximum values increased from 0.691 to 0.998 over the same period. This consistent upward trend indicates progressive salinity intensification, highlighting a growing risk of land degradation in the study area. Overall, the integration of RS indices with ground EC validation proved effective for detecting, quantifying, and visualizing salinity‐induced degradation at the landscape scale. These findings emphasize the importance of continuous satellite monitoring, soil reclamation, and sustainable irrigation management to mitigate salinity expansion in coastal agricultural regions.