Future vulnerability of near-global coastlines to saltwater intrusion

Coastal watersheds around the globe are facing perilous changes to their freshwater systems. Driven by climatic changes in recharge and sea level working in tandem, sea water is advancing into coastal aquifers in a process called saltwater intrusion (SWI). To assess the vulnerability of coastal watersheds to future SWI, we applied projections of future sea level and groundwater recharge to a global analytical modeling framework. Nearly 75% of the global coast are expected to undergo measurable SWI by the year 2100. Changes in recharge have a greater effect on the magnitude of SWI, whereas sea level rise has a greater effect on SWI in low-lying areas. Our results highlight the variable pressures of climate change on coastal aquifers and have implications for prioritizing management solutions.