The coastal marine environment is affected by the modification and destruction of habitats, over-fishing and pollution. Many of these impacts can be traced back to land-based human activities located far from the sea. However, two of the largest problems of recent years result from rising sea levels: coastal erosion and increase in the frequency of coastal flooding events.
The loss of coastal wetland habitats plays a key role in the life cycle of certain economically important marine species.
Reclamation and construction of industrial complexes add a pollution dimension to the conversion of marine habitats and thus threaten the viability of coastal aquaculture areas and future coastal and off-shore fisheries.
Coastal habitats (mangroves, seagrass systems, coral reefs and lagoons, and estuaries) provide habitat for about 90 percent of the world's fish production, at all or some stages in the lives of the fish. In particular, salt marshes, seagrass beds, and mud flats have enormous biological productivity and are important as nursery grounds for coastal and oceanic marine fish as well as for endemic and migratory birds. Even species not confined to wetlands are dependent on the shelter offered by inaccessible wetlands.
Only about 16% of the world’s coastal regions are in relatively good condition (2020) and many are so degraded they can’t be restored to their original state.
The deterioration of the marine environment in the Florida Keys is no longer a matter of debate. There is a decline of healthy corals, an invasion of algae into seagrass beds and reefs, a decline in certain fisheries, and an increase of coral diseases and coral bleaching. In Florida Bay, reduced freshwater flow has resulted in an increase in plankton blooms, sponge and seagrass die-offs, and fish kills.