Fluctuating soil salinity across natural and managed landscapes of the coastal mid-Atlantic facing rapid sea-level rise.

The coastal mid-Atlantic region of the United States is increasingly vulnerable to soil salinization, primarily driven by sea-level rise and powerful coastal storms, posing a threat to farmland productivity, and ecological stability. However, the spatially heterogeneous nature of salinization across different land covers makes it challenging to monitor their interactions across large areas and longer time periods. To address this gap, we combined remote sensing-based land cover classification with modeled soil salinity data to assess landscape-scale dynamics across the Delmarva Peninsula from 2000 to 2016. Using a Random Forest classifier trained on Continuous Change Detection and Classification (CCDC)-derived synthetic Landsat surface reflectance, we generated gridded land cover datasets for five years (2000, 2002, 2005, 2009, and 2016) to match and compare with the existing Global Soil Salinity Maps. Overall, forests and other vegetation expanded, whereas farmland and bare soil declined. Salinization trend across these land covers is neither uniformly optimistic nor categorically alarming. Our results showed that over 75% of Delmarva remained in the non-saline category in those 5 years, increasing by 1,138 km², and extremely saline zones declined by 833 km². More than 83% of land cover transitions occurred without changing salinity categories, while 7-11% moved to a lower salinity category. Our findings based on these temporal snapshots reveal fluctuations in salinity across different land covers, underscoring the value of multi-temporal remote sensing for continuous monitoring of salinity-driven land changes.