Degradation pathways in mediterranean coastal groundwater dependent ecosystems: A process based review toward an integrated conceptual framework

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Study region: The Mediterranean Basin hosts a diverse array of coastal groundwater dependent ecosystems, here defined as coastal environments that rely on groundwater to sustain hydrological regimes and associated biogeochemical processes. These systems include lagoons, coastal lakes, marshes, river delta wetlands, sabkhas, and artificial wetlands distributed along approximately 46,000 km of coastline. Located within a recognized climate change hotspot, Mediterranean coastal groundwater dependent ecosystems are exposed to intensifying climatic seasonality, chronic water scarcity, and long-standing anthropogenic pressures, making their functioning particularly sensitive to alterations in groundwater recharge, storage, and subsurface connectivity. Study focus: This review examines 267 peer-reviewed studies (2000–present) on Mediterranean coastal groundwater dependent ecosystems through a site-based bibliographic approach that combines satellite-derived site identification with targeted literature searches. The studies were classified according to spatial, temporal, and conceptual dimensions, with particular emphasis on dominant degradation processes and on the extent to which groundwater is incorporated into interpretative frameworks. New hydrological insights:: Lagoon systems account for the majority of the reviewed literature (183 studies), reflecting both their widespread occurrence and the existence of well-established research traditions. Research is geographically concentrated in Italy, Spain, and France, whereas North Africa and the eastern Mediterranean remain comparatively underrepresented. Groundwater is most commonly conceptualized as an implicit component (147 studies) or a mediating factor (83 studies), and only rarely as a primary driver (37 studies). Salinization, nutrient enrichment, hydrological alteration, and contaminant accumulation emerge as the principal degradation pathways, governed by nonlinear interactions between climatic and anthropogenic pressures. A five-phase process-based framework is proposed to integrate hydrogeological, biogeochemical, and ecological analyses, providing a transferable basis for diagnosing degradation mechanisms and supporting adaptive management strategies across diverse coastal groundwater dependent ecosystems settings.