An estimated 60 percent of the global population lives within roughly 100 kilometers of the shore. This means that about 3.4 billion people rely heavily on marine habitats and resources.

An estimated 60 percent of the global population lives within roughly 100 kilometers of the shore. This means that about 3.4 billion people rely heavily on marine habitats and resources for food, building materials, building sites, and agricultural and recreational areas and use coastal areas as a dumping ground for sewage, garbage, and toxic wastes [1]. Moreover, much of the remaining noncoastal population is concentrated along rivers and other waterways. Pollution and poor land use practices within these watersheds affect downstream marine habitats because sediments and pollutants are ultimately washed into coastal waters.

Pressures on marine ecosystems include coastal population density and continued population growth, which are accompanied by increased consumer demand for marine products, increased waste disposal, rapid alteration of coastal habitats, uncontrolled industrial pollution, inadequate institutional structures for managing marine resources, lack of property rights and management regimes within international waters, and lack of understanding and awareness of marine ecosystem processes and the effects of human actions on marine biodiversity.

Most of the world's marine ecosystems--particularly nearshore habitats--are stressed by a combination of these factors. The Black Sea, for example, is dying under the weight of pollution and overfishing. Land-based pollution in the form of industrial wastes, sewage, and runoff of pesticides and fertilizers, combined with oil and other wastes from ship traffic, have contaminated the entire basin. Eutrophication has left 90 percent of the Black Sea facing critically low oxygen levels [2]. The total fish catch within the region declined by 64 percent between 1986 and 1992 [3]. The cost of this damage is estimated at $500 million annually to the fishing and tourism industries alone [4].

The direct factors (pressures) leading to the loss of marine biodiversity can be broken into five categories:

• habitat loss,
• intense overexploitation,
• pollution and sedimentation,
• species introductions, and
• climate change.

References and notes

1. Thomas Goreau and Raymond Hayes, "Coral Bleaching and Ocean Hotspots," Ambio, Vol. 23, No. 3 (May 1994), pp. 176-177.

2. Anne Platt, "Dying Seas," World Watch Vol. 8, No. 1 (January/February 1995), pp. 11-12.

3. Food and Agriculture Organization of the United Nations (FAO), Review of the State of World Fishery Resources: Marine Fisheries, FAO Fisheries Circular No. 884 (FAO, Rome, 1995), p. 82.

4. Op. cit. 60, p. 12.

5. Op. cit. 13, p. 106.

6. Jeremy Cherfas, "The Fringe of the Ocean--Under Siege from Land," Science, Vol. 248, No. 4952 (April 13, 1990), p. 164.

• Habitat loss. Habitat conversion and degradation are generally thought to be the most significant threats to terrestrial life.