The Invisible Flood: The Chemistry, Ecology, and Social Implications of Coastal Saltwater Intrusion

TLDR

Saltwater intrusion, the leading edge of sea‑level rise, is moving inland under climate change, creating novel biogeochemical, ecological, and human land‑use transitions that must be understood and managed to promote coastal resilience. The study investigates how saltwater intrusion drives biogeochemical, ecological, and socio‑economic changes and examines trade‑offs in land‑management decisions and public policy to guide climate adaptation in coastal ecosystems. The authors analyze trade‑offs among land‑management decisions and public‑policy options to shape socio‑ecological transitions in the coastal zone. Saltwater intrusion increases ionic strength, sulfidation, and alkalinization, leading to upland forest retreat, freshwater wetland conversion, nutrient mobilization, and reduced agricultural productivity.

Abstract

Abstract Saltwater intrusion is the leading edge of sea-level rise, preceding tidal inundation, but leaving its salty signature far inland. With climate change, saltwater is shifting landward into regions that previously have not experienced or adapted to salinity, leading to novel transitions in biogeochemistry, ecology, and human land uses. We explore these changes and their implications for climate adaptation in coastal ecosystems. Biogeochemical changes, including increases in ionic strength, sulfidation, and alkalinization, have cascading ecological consequences such as upland forest retreat, conversion of freshwater wetlands, nutrient mobilization, and declines in agricultural productivity. We explore the trade-offs among land management decisions in response to these changes and how public policy should shape socioecological transitions in the coastal zone. Understanding transitions resulting from saltwater intrusion—and how to manage them—is vital for promoting coastal resilience.