A high proportion of the world's population resides in coastal areas, and many more derive benefit from marine resources such as food, employment, or tradable commodities. Marine coastal ecosystems and the accompanying biodiversity are particularly vulnerable to land-based sources of contamination.

An estimated one third of the world's coastal regions are at high risk of degradation, with the greatest threat apparent in Europe. Asia and the Pacific, the wider Caribbean, and West Asia also face problems related to land-based sources of urban waste discharge and industrial pollution. Shipping traffic and oil spills represent a particular threat in West Asia and the Caribbean. Threats to the coastal and marine resources in Latin America and the Caribbean rise considerably with tourism, infrastructure development, and the discharge of sediment, waste, and industrial contaminants. Coastal erosion is a growing problem in a number of African countries where local communities are adversely affected by changing sedimentation patterns due to upstream dam construction or increased erosion in degraded catchments. Eutrophication in the Baltic, Black, and North seas is also a problem-and a severe one in localities bordering the Mediterranean and Caspian seas.

The overexploitation of marine fisheries and the economic impact of such practices cause widespread concern in parts of Asia and the Pacific, North America, Europe, and West Asia. In addition, small island states and coastal communities of South-East Asia, the Pacific, the Caribbean, and low-lying areas of Europe have special concerns over the future impacts of climate change on sea level, especially as the precise local effects cannot yet be determined. Climate change may also affect ocean mixing and circulation patterns, with significant repercussions on the productivity of marine ecosystems and the location of fisheries.