Quarter of world's corals destroyed

More than a quarter of the world's coral reefs have now been destroyed, mostly in the past decade, and nearly three-quarters are likely to be gone within 50 years, a startling new international study says.

More than a quarter of the world's coral reefs have now been destroyed, mostly in the past decade, and nearly three-quarters are likely to be gone within 50 years, a startling new international study says.

The report, by the official Global Coral Reef Monitoring Network, is the most alarming yet on the fate of the richest and most beautiful celebrations of life in the seas. Although corals cover only one-fifth of 1 per cent of the area of the oceans, they are home to one-quarter of all their species.

The report documents how the reefs of 93 countries - living entities built over centuries by tiny creatures - are being destroyed by over-fishing, pollution, global warming and tourism.

The United Nations Environment Programme, one of the international bodies that established the monitoring network, has just set up a Coral Reef Unit to tackle the crisis. Professor Klaus Töpfer, its executive director, said: "Coral reefs may be the equivalent of the canaries in coal mines giving early warning that the world's ecosystems can no longer cope with growing human impact."

The report says that by 1992 10 per cent of the world's reefs had been lost, but this had shot up to 27 per cent by the end of last year. The worst-affected areas are the Indian Ocean, where 59 per cent of the reefs have been lost, the Middle East (35 per cent) and South-East and Eastern Asia (34). The healthiest ones are in the Pacific and off Australia.

The Caribbean, which has lost about a quarter of its reefs, has some of the longest-standing problems. Decades of over-fishing and pollution have severely undermined the reefs' health, making them prey to disease.

Sewage and fertiliser running off the land encourage the growth of algae which choke the living coral polyps and cut off their supplies of light and oxygen. Over-fishing makes this even worse because it takes away the fish that would otherwise eat the algae and keep them in check.

Building on the coasts - or even cutting down forests inland - causes soil to be washed into the sea, smothering the polyps. Garbage has the same effect. Chemical and oil pollution poisons them and so does cyanide often used by fishermen to stun their prey off the Philippines and other areas.

Reefs are mined and dynamited to provide construction materials and careless tourists can also damage them by dropping anchors from pleasure boats onto the reefs, or even walking on them.

The biggest threat of all, however, says the report, is global warming. When water temperatures get too high the polyps turn white and die. About 16 per cent of the world's reefs were destroyed by such "bleaching" in just nine months in 1998, when temperatures in parts of the tropics exceeded all records, particularly affecting the Indian Ocean, South-East Asia and the far-western Pacific. In many areas, 60 to 90 per cent of the reefs were lost. The Seychelles, Maldives, Philippines, Kenya and Taiwan were among the worst-affected areas, but Australia's Great Barrier Reef and most of the Pacific largely escaped.

Some of these reefs, the report says, may revive if the oceans cool again, but scientists fear that as global warming increases the crisis will go on getting worse. It predicts that if global warming and other damage continues, 40 per cent of all the world's reefs will be lost by the end of this decade, and 70 per cent by the middle of the century. The effects will damage economies: 20 countries have few sources of income other than fish caught on the reefs and the tourists the corals attract.