The natural environment of coastal areas, which includes wetlands, estuaries, mangroves and coral reefs, is being degraded by agricultural and urban development, industrial facilities, port and road construction, dredging and filling, tourism and aquaculture. Dam construction, even located far inland, can alter water flow patterns that support important fisheries, as well as cutting off the supply of sediment necessary to maintain deltas and coastlines.
The many people living in coastal zones, and even those located far inland, generate large quantities of wastes and other polluting substances that enter the seas directly or through coastal watersheds, rivers and precipitation from polluted air.
More than one-third of the world's population lives within 100 km of a seashore (Cohen and others 1997) - 50 per cent of the population in North America and 60 per cent in Latin America, where 60 of the largest 77 cities lie on the coast. By 2000, nearly 500 million people will be concentrated in urban conglomerations along the shores of Asia (WRI/UNEP/UNDP 1994).
Up to 38 per cent of the African coastline of 40 000 km is considered to be under a high degree of threat from developments which include cities, ports, road networks and pipelines, including 68 per cent of marine protected areas (WRI, UNEP, UNDP and WB 1996, and World Bank 1995a).