Reefs at Risk

Less than one percent of the ocean

Coral reefs are the most biologically diverse marine habitats in the world, and host to an extraordinary diversity of plant and animals. Corals themselves are very simple organisms, found in all the world's oceans and at all depths; a large number of which have developed the ability to live in colonies and to build up a communal skeleton of calcium carbonate. These reef-building corals are almost entirely confined to areas of warm, shallow water. Thus, to a large extent, warm-water, shallow coral reefs are restricted to a latitudinal band between 30N and 30S, or where ocean currents have disrupted these simple patterns with warm currents that flow all year round. Even in ideal conditions, reef-building corals are slow growing, with rates varying with the species and conditions, from a few millimetres to 150 millimetres per year. The physical structure of coral reefs is built up and broken down over decadal time scales by both physical and biological actors supporting a complex diversity of inhabitants.
Despite this fact, it is estimated that shallow coral reefs worldwide occupy some 284,300 square kilometres; this is less than 1.2 percent of the world's continental shelf area and only 0.09 of the total area of the world's oceans. Indonesia possesses the largest amount of coral reef, followed by Australia and the Philippines. The most diverse region of the world for coral reefs is centered in the Philippines, Indonesia, Malaysia and Papua New Guinea, with between 500 and 600 species of coral in each of these countries. Yet coral reefs around the world are rapidly being degraded be human activities such as over-fishing, coastal development, and the introduction of sewage, fertilizer, and sediment. And because corals are highly sensitive to changes in water temperature, they are particularly vulnerable to climate change.
Assessments to late 2000 now indicate that 27% of the world's reefs have been effectively lost, with the largest single cause being the massive climate-related coral bleaching event of 1998. While there is a good chance that many of the 16% of damaged reefs will recover over time, some predict that half will never adequately recover. The latest global predictions suggest that a further 14% of the world's coral reefs will be lost by 2010, and another 18% in the 20 years following, without reductions in the current human-induced stresses on reef ecosystems from growing coastal populations and economies. This means that 59% of the world's reefs are under immediate threat of loss within several decades.