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coasts and oceans > factfile > coral reefs

Coral reefs

Posted: 12 Oct 2004

Coral reefs are natural living structures and coral itself is half plant and half animal. Coral reefs are actually living apartment houses, built by transparent polyps, which secrete calcium carbonate (the main ingredient of limestone) and erect their architectural masterpieces upon the remains of their predecessors.

Corals vary enormously in size, shape and color - from the delicate filigree of the sea fan and the branching antlers of the staghorn coral to the large bulging brain coral. There are button corals, fire corals, lace corals, bead corals, organ-pipe corals and vase corals, all of which resemble their namesakes. Countries containing the greatest diveristy of coral include the Philippines, Indonesia, Malaysia and Papua New Guinea, with between 500 and 600 species of coral in each of these countries.

<br>Gorgonian soft coral on sea fan, Red Sea.
Gorgonian soft corals on sea fan, Brothers Islands, Red Sea, Egypt.
© Mary Lou Frost/ICRIN

Nothing in the sea rivals the biodiversity of coral reefs. Often described as "rainforests of the sea", scientists estimate that these rich ecosystems host an extraordinary variety of marine plants and animals, perhaps up to two million, including one quarter of all marine fish species. So far It has been estimated that so far only about 10 per cent of these species have been described by scientists. Moreover, the tremendous variety found on coral reefs is crammed into roughly 284,300 square kilometres - an area just half the size of France1.

For more about corals, see this page of the International Coral Reef Information Network.

Coral crisis

In the early 1990s marine scientists estimated that 10 per cent of the world's reefs had already been degraded beyond recognition. Another 30 per cent were in critical condition and would be lost within 30 years if concerted action were not taken to safeguard remaining resources.

In 1998, the World Resources Institute reported that close to 60 per cent of the world's reefs were threatened by human activity. The most degraded reefs are found in Southeast Asia and the Caribbean. In Southeast Asia, 88 per cent of all reefs are at risk. In the Caribbean, two-thirds are in danger.

According to a report by leading marine scientists in Science (February 15, 2002), the top ten coral reef hotspots, ranked according to the degree of threat are:

1) Philippines
2) Gulf of Guinea Islands
3) Sunda Islands (Indonesia)
4) Southern Mascarene Islands (near Madagascar)
5) Eastern South Africa
6) Northern Indian Ocean
7) Southern Japan, Taiwan and southern China
8) Cape Verde Islands
9) Western Caribbean
10) Red Sea and Gulf of Aden

These hotspots contain just 24 per cent of the world's coral reefs, or 0.017 percent of the oceans, but are home to 34 per cent of the all species within limited ranges (see: Scientists name top ten coral hotspots

Threats to reefs

According to the World Atlas of Coral Reefs published by the UN Environment Programme World Conservation Monitoring Centre, some 58 per cent of the world�s coral reefs are under assault from human activities as never before. They are beset by fishers using dynamite, poisons and fine mesh nets to capture reef dwelling fish and shellfish, destroying their own resource base in the process.

In Indonesia, 82 per cent of its reefs are "at risk", threatened by the illegal practice of blast fishing. This is the most destructive fishing method on reefs. Explosives are typically thrown towards the reef and explode on the water surface. The shock wave from the blast kills the majority of fish species on the reef and causes severe damage to its structure.

Worldwide coral reefs are also smothered by increasing loads of pollution and sediment washed off the land into shallow coastal waters.

Reefs are also being killed off by rising sea temperatures, a result of global climate change brought on by the use of fossil fuels which emit climate-changing gases, such as carbon dioxide. The El Ni�o event in 1998 itself caused the loss of 90 per cent of the corals in some parts of the Indian Ocean, representing 5 per cent of the world�s reef area. For comparison, this is equivalent to loosing 90 per cent of the trees in Europe in the space of a few months.

While the developed world is responsible for three quarters of the green house gases in the atmosphere, the world�s poor will be worst affected by coral bleaching: 100 million people, most of which live in developing countries, depend on coral reefs for their survival. 40 per cent of the world�s poor live in South Asia, and most of them rely on natural resources such as coral reef fish for their livelihoods.

In November 2006, the World Conservation Union (IUCN) said that the bleaching of corals due to climate change may result in global economic losses of up to US$ 104.8 billion over the next 50 years, or 0.23 per cent of current global GDP.

Reporting to the UN conference on climate change, IUCN said these losses will occur in coral reef dependent industries and in services such as tourism and fisheries as well as shoreline protection and medicinal plants.

For more information on the threats to corals, see this page of the International Coral Reef Information Network.

Human benefits

Coral reefs are an important source of food for hundreds of millions of people, many of whom have no other source of animal protein. They also provide income and employment through tourism, and marine recreation, and export fisheries, and for many coastal villages, and some entire nations are the only source of this income and employment. Furthermore, they offer countless other benefits to humans, including supplying compounds for medicines. AZT, a treatment for people with HIV infections is based on chemicals extracted from a Caribbean reef sponge and more than half of all new cancer drug research focuses on marine organisms.

An independent report funded by WWF, the conservation organization (published February 2003), warns that degradation of coral reefs threatens the nearly US$30 billion in net benefits that these ecosystems provide each year in goods and services to world economies, including tourism, fisheries, and coastal protection. The report The Economics of Worldwide Coral Reef Degradation indicates that coral reef systems are worth a global asset value of nearly US$800 billion. However, the report notes that "less than 1 per cent of the ocean's surface is currently protected, and it is not even known what the level of coral reef protection is globally."

Reefs provide a vital service as a buffer to coastal erosion, protecting inshore areas from the pounding of ocean waves. Without coral reefs, many beaches and buildings would become vulnerable to wave action and storm damage. In one instance, when coral and sand were mined away in the Maldives, it cost US$10 million per kilometre to build a wall to protect the coastline2.

For more on how we benefit by coral reefs, see this page of the International Coral Reef Infromation Network.

Coral conservation

Reefs can be saved by concerted efforts at educating coastal communities about the importance of healthy coral reefs, the use of non-destructive fishing techniques and the development of alternative livelihoods.

Coral reefs can also be protected by conservation programmes and the creation of marine parks. About six per cent of the world's land is in parks. But at sea, less than one-half of one per cent is in any kind of protected area.

The World Atlas on Coral Reefs maps 660 marine protected areas worldwide that incorporate coral reefs. The Great Barrier Reef Marine Park is the largest marine park in the world, covering 345,000 sq km of reefs and surrounding waters. At the other extreme are the many small marine reserves that are managed by local communities.

Marine protected areas are often zoned or divided up to benefit different users. One area may be closed to fishing so that commercial species can breed in peace. Another area may be set aside for snorkellers and divers. Others may be for general purposes.

Marine parks cannot prevent pollution entering from outside, but they play a critical role in controlling human activities on those reefs that are of particular scientific and economic importance.

1. The World Atlas of Coral Reefs, United Nations Environment Programme World Conservation Monitoring Centre (UNEP-WCMC), 2001.

2. Coral Reefs, Mangroves and Seagrasses: A sourcebook for Managers, F. Talbot and C. Wilkinson, 2001.

Related links:

Scientists name top ten coral hotspots

World Atlas of Coral Reefs

Coral Reef Alliance

International Coral Reef Information Network

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