Many millions more live within an easy day's travel of coastlines. The majority of the earth's 5.5 billion people live around the coastal fringes of the continents. Coastal environments, whether they are tropical mangrove swamps, tidal flats, marshes or estuaries are the biologically richest parts of the oceans. They are feeding and nursery grounds for more than ninety percent of fish, including fish which spend their adult lives in the open seas. Almost ninety-nine percent of commercially valuable fish are caught within 200 miles of a coastline.
Coastal environments are enormous sanctuaries for migratory birds.
They are catchment areas for river sediments which would be dispersed in the oceans if they were not trapped by marsh grasses and other plants. From the earliest times of known human settlements, coasts, marshes, and river deltas have been the locus of human settlement. Human settlement and its density has already taken a toll on our planet's coasts. Many of the world's large coastal cities don't have wastewater treatment, and spill raw sewage directly into the oceans. If they are going to keep on doing so, we will have to pay more attention to the oceans than we have in the past.