Seawater Intrusion and Soil Salinization in Coastal Agriculture: Global Hotspots, Remote-Sensing Evidence, and Mitigation Pathways

Coastal agriculture is increasingly affected by salinization as sea-level rise, subsidence, river regulation, and water withdrawals combine with more frequent drought and heat extremes. In recent years, a key advance has been the ability to link seawater intrusion (SWI) to crop impacts by integrating satellite observations with targeted field measurements.

At the global scale, cropland distribution and low-elevation coastal metrics reveal a clear mismatch between where impacts are reported and where exposure is likely. Documented hotspots include the Mediterranean, South and South-East Asia, and the Bohai Sea region, while extensive low-lying coastal croplands remain weakly monitored. A screening based on coastal proximity and elevation indicates ~87 Mha of cropland potentially vulnerable to SWI-related salinization (Ghirardelli et al. 2025). This estimate is useful to guide monitoring and prioritization. The global synthesis also highlights recurring combinations of drivers—drought and low flows, pumping, subsidence, and saline surface-water incursions—that promote salt accumulation in soils.

At the regional scale, results from the Po River Delta (Italy) illustrate how drought can trigger rapid salinity increases and measurable crop impacts (Luo et al. 2024). Sentinel-2 time series of vegetation greenness and salinization-sensitive spectral information, interpreted alongside measurements of soil electrical conductivity and moisture, provide spatially explicit identification of vulnerable areas and seasons. This approach supports early warning during extreme dry summers and provides benchmarks to evaluate management actions.

Mitigation is moving from single measures to combined strategies. Current evidence supports integrated portfolios that couple nature-based buffers (e.g., wetlands/mangroves that limit saline intrusion while sustaining ecosystem services) with water and soil management (rainwater harvesting and storage, efficient irrigation including precision and subsurface drip systems, and drainage improvement) and, where needed, salt-tolerant crops enabled by breeding and bioengineering (Tarolli et al. 2024).

Remaining challenges include: (1) AI-enabled prediction for short-term forecasting and early warning, especially during drought and low-discharge periods; (2) process-coupled models that translate seawater intrusion into root-zone salinity, including irrigation water quality, evaporaton-driven salt concentration, capillary rise, and drainage; (3) stronger monitoring with denser networks and higher-frequency data, integrating in situ salinity/EC measurements with remote sensing; (4) a practical management protocol for coastal agriculture linking observations to irrigation, drainage, and water allocation decisions; and (5) progress in salt-tolerant crops (breeding and bioengineering), tested and deployed together with soil–water management under real coastal conditions.

References

• Ghirardelli et. al. (2025). Environmental Research Letters, doi:10.1088/1748-9326/ad9bcd.
• Luo et al. (2024). International Soil and Water Conservation Research, doi:10.1016/j.iswcr.2023.09.009.
• Tarolli et al. (2024). iScience, doi:10.1016/j.isci.2024.108830.