Coastal Wetland Loss

Coastal wetland loss is the decline in area or health of salt marshes, mangroves, and tidal flats from drowning, erosion, sediment starvation, and human reclamation. The dominant driver is the inability of marsh and mangrove surfaces to accrete vertically as fast as relative sea level rises, so the platform drowns where sediment supply or migration space is short. Coastal squeeze, hard defenses blocking landward retreat, accelerates the loss. Wetlands attenuate waves and storm surge, store blue carbon, and nurse fisheries, so their loss raises flood risk on the coasts behind them. It is quantified from repeated mapping against a tidal datum.