Coastal aquifer vulnerability to salinization under sea-level rise and groundwater abstraction pressure in a Mediterranean karst system

Sea-level rise and groundwater abstraction are reshaping coastal systems in karst environments, particularly in low-gradient coastal plains where groundwater-dependent ecosystems are strongly coupled to aquifer dynamics. However, most coastal assessments remain based on topographic inundation and shoreline retreat, neglecting groundwater processes that influence the inland propagation of marine influence. This study presents a GIS-based hydro-coastal vulnerability screening framework designed to identify areas potentially influenced by the combined effects of sea-level rise and groundwater stress. The approach integrates (i) DEM-based potential marine inundation, (ii) hydrogeological signals of piezometric decline and salinization derived from monitoring data, and (iii) a multi-criteria hydro-coastal vulnerability index incorporating ecological sensitivity, hydrogeological susceptibility, anthropogenic pressure, and system resilience. Direct potential marine inundation alone affects between 9.24 and 43.76 km 2 (0.25–1.20% of the island) across sea level rise scenarios but underestimates the inland extent of coastal influence. Including groundwater indicators identifies a broader scenario-based coastal influence zone and increases ecosystem exposure, with up to 97% of wetland area potentially exposed within the integrated coastal-influence zone under high-end scenarios. Vulnerability is concentrated in low-lying coastal plains, particularly in s’Albufera, Campos–Es Trenc, and Albufereta, where strong aquifer–sea connectivity and anthropogenic pressure converge. These findings suggest that coastal evolution in Mediterranean karst settings emerges from the interaction between surface and groundwater processes and highlight that hydrogeologically informed regional screening approaches may identify coastal areas extending beyond static representations of the MTPD, thereby informing future coastal-domain management rather than redefining regulatory boundaries.