Reefs at Risk

1. A world-wide threat of ecological collapse

A coral reef in the Maldives. We have barely tapped the knowledge to be gained from the rich diversity of reef life.

Photo: WWF / B ‘ C Lang

For once, the popular mythology contains some truth. Coral reefs can be likened to tropical forests in certain important ways. Both reefs and jungles are biologically diverse in comparison with other ecosystems. Reefs are an essential supplier of protein to subsistence communities; a valuable currency earner for low-income countries through exploitation of their resources and through tourism; a protector of land; and a naturalist's paradise.

Unfortunately, the analogy is equally apt with respect to the dark side of the picture: though we have barely tapped coral reefs for the knowledge to be gained or the natural products of interest to society, reefs are coming under increasing threat, almost exclusively because of human activities.

Around the world coral reefs have suffered a dramatic decline in recent years. About 10% may already have been degraded beyond recovery. Another 30% are likely to decline seriously within the next 20 years. It has been predicted that more than two-thirds of the world's coral reefs may collapse ecologically within the lifetime of our grandchildren, unless we implement effective management of these resources as an urgent priority.

The reefs identified as being at greatest risk are in South and Southeast Asia, East Africa, and the Caribbean. An IUCN survey during 1984-1989 found that people had significantly damaged or destroyed reefs in 93 countries.

Effective management is essential and urgent if we are to prevent the collapse of two-thirds of the world's coral reefs.

Coral reefs and biodiversity

Coral forms range from compact brain corals found in areas of high wave energy, through heavy branching and plate corals in deeper water, off the reef edge, to smaller finely branched corals found behind the reef crest and in the lagoon.

Coral reefs are generally divided into four main types: atolls, barrier reefs, platform reefs, and fringing reefs. Atolls, where reefs form a ring around a lagoon, are mainly found in the Indian and Pacific Oceans. In the Pacific they are grouped into long island chains such as those of Micronesia and Central Polynesia. Barrier reefs are separated from the mainland by a deep channel or lagoon, in which are found platform reefs. Fringing reefs are directly attached to land or separated only by a shallow lagoon.

On an individual reef, the total count of fish species and smaller marine organisms may exceed several thousand, but the number of individual coral species is much lower.

The Indo-Pacific has some 700 reef-building coral species, many times more than the tropical Atlantic (with some 35). In general, reefs in the Indo-Pacific differ from those of the Atlantic by having many more coral species, and by supporting much richer animal communities on their intertidal reef fiats. The centre of coral diversity is the Southeast Asia region of the Indo-Pacific, and over 400 species of hard coral are believed to occur in Philippine waters.

Moving away from this region, coral diversity declines. Nevertheless, over 200 coral species are recorded from the northern and central Red Sea, about 200 from Madagascar and Chagos. The east coast of the Malaysian peninsula has 174 identified species, south-east India about 117, the Gulf of Thailand some 601 and the Persian Gulf 57.

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March 30, 2010