Nature Gallery (Global Trends)

Marine Pollution and Overfishing

Polluting the Oceans
Seventy per cent of the world’s population lives in coastal areas, and although coastal waters account for only about 0.5 per cent of all ocean water by volume, they provide habitat for half the world’s fish catch. As the number of people in coastal areas continues to rise, the potential for harming this habitat also grows.

The causes of coastal habitat damage include deforestation, industrial chemical emissions, pesticide and fertilizer run-off, oil spills, sewage effluent, and overfishing. Half the world’s coastal mangrove forests, which provide critical spawning grounds for fish and help prevent erosion, have been cleared for firewood or artificial shrimp ponds. Coral reefs off the coastlines of numerous countries are in decline due to soil erosion from deforestation, sewage discharge, and industrial and agricultural chemical pollution.
Many nations dump industrial waste products into coastal waters, both intentionally and as a by-product of routine practices. In fact, only 12 per cent of the oil that spills into the ocean results from tanker accidents. The rest comes from land run-off, natural sources, and “normal” spillage associated with loading oil into tankers and cleaning out storage tanks while at sea. The Mediterranean Sea alone suffers the equivalent of 17 Exxon Valdez oil spills each year. The Valdez is the tanker ship that ran aground in Alaska’s Prince William Sound in 1989, spilling more than 39 million litres (10 million gallons) of oil into the water and on the shoreline.

In the winter of 1987–1988, when 700 dead bottlenose dolphins washed up on East Coast beaches in the United States, they were so heavily contaminated with PCBs (polychlorinated biphenyls) that under federal government guidelines they constituted toxic-waste hazards. In an example from another region of the world, Russia admitted in 1993 that the government of the former Union of Soviet Socialist Republics (USSR) had dumped 18 nuclear reactors into the Kara Sea, emitting 2.5 million curies of radioactivity.

Sewage dumping also poses a widespread threat to coastal waters. More than 2,600 beaches in the United States were closed in 1992 due to sewage pollution. Athens, the capital city of Greece, with a population of 3,693,000 (1995) people, is just one of many cities worldwide that dumps untreated municipal sewage into the sea. Sewage does its damage by “fertilizing” water, causing huge algae blooms that deplete the water’s oxygen, killing most marine life. Red tide, a toxic plankton that thrives in such rich environments, regularly kills fish, marine mammals, and, occasionally, people who eat toxin-contaminated seafood. Between 1985 and 1990, Massachusetts lost half its clam harvest to sewage-related pollution.

Overfishing
Fisheries around the globe are also showing signs of crisis. Internationally, overfishing has greatly depleted stocks of commercial fish species, and in the United States, catches for 85 per cent of commercial species, including cod, haddock, flounder, and wall-eye, are on the decline. Anchovy fisheries off Chile and Peru are virtually unusable, and in some ecosystems, such as the Georges Bank off New England, native fish will never return to former levels because other species have taken over.

Both individually and in group efforts, countries around the world are working to slow the damage to coastal marine habitat. Most cities in the United States, for example, have stopped throwing municipal wastes into the sea. And fishing nations have tentatively agreed to establish a polar whale sanctuary around Antarctica, a permanent refuge for a marine mammal that has been particularly hard hit by water pollution.