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Definition: coral reef from Philip's Encyclopedia

Rock formation found in shallow tropical seas. Such reefs are formed from the calcium carbonate secreted by living coral organisms as protection against predators and wave action. The way in which the coral, and therefore the reef, grows is strongly influenced by the prevailing currents and the temperature of the surrounding sea water.

Summary Article: Coral Reefs
from Encyclopedia of Environment and Society

CORAL REEFS ARE massive and complex structures made of limestone that is deposited by living sea organisms. The reefs are mainly composed of the skeletons of tiny, fragile animals called coral. Although there are hundreds of different species of corals, they are generally classified as either “hard coral” or “soft coral.” Hard corals grow in colonies. Their skeletons are made out of calcium carbonate, which hardens and eventually becomes rock (i.e., coral reefs). Soft corals are nonreef building corals often resembling plants or trees.

Coral reefs are found in over 100 countries and cover an estimated total area of 109,700 square miles (284,300 square kilometers) worldwide. Most reefs are located in oceans between the Tropics of Cancer and Capricorn, but they are also found farther from the equator in places where warm currents flow out of the tropics (such as Florida and southern Japan). Corals prefer clear and shallow waters where sunlight filters through to their symbiotic algae. Other factors affecting their growth are salinity, turbulence, and the availability of food.

Most of the world’s coral reefs, while useful to humans in many ways, are in trouble mainly due to human impacts.

Coral reefs are one of the most spectacular, complex, highly productive, fragile, and biologically diverse ecosystems on the earth. They cover less than 1 percent of the ocean floor but support around 25 percent of all marine life, including over 4,000 species of fish, 700 species of coral, and thousands of other plants and animals. The reefs are useful to humans in several ways. The rich biological diversity of reefs is a natural treasure and a key part of the natural heritage of the world. The interlinked network of species supported by coral reefs has long been a significant source of food for millions of people living in tropical coastal areas and islands. Unique chemical compounds found in coral reef organisms have been used to produce several important drugs including AZT, a treatment for people with HIV infections. Coral reefs form natural breakwaters protecting the fertile coastal lands and human settlements of many island and continental nations from the pounding of ocean waves. The beauty of the coral reefs has long been a source of wonder to people. Many countries with coral reefs generate significant portions of their income through tourism. The reefs are also directly linked with traditional spiritual and cultural values of many people who live in reef areas.

Most of the world’s coral reefs are in trouble due mainly to direct human impacts, such as overfishing or destructive fishing, mining of coral and dredging of sand and gravel for construction and industrial use, soil erosion and use of pesticides for agriculture on lands draining into coastal coral reefs, intensive and ill-considered coastal development activities with hotels and infrastructure, discharge of sewage, collection of specimens by and for visitors, and international trade in ornamental corals and shells. It is estimated that around 20 percent of the reefs have been effectively destroyed beyond likelihood of recovery; 24 percent are under imminent risk of collapse; and a further 26 percent are under a longer-term threat. Long-term changes in the oceans and atmosphere, natural stresses of highly variable seasons, severe storms, earthquakes, volcanic eruptions, and increased incidence of coral diseases are other reported factors behind the reefs’ destruction. Many coral reefs (approximately 40 percent) that were seriously damaged in the 1998 El Niño/La Niña global coral bleaching event are either recovering well or have recovered, especially well-managed and remote reefs. Scientists, however, fear that this recovery could be reversed if the predicted increases in ocean temperatures occur as a result of increasing global climate change.

Scarcity of resources, poor awareness, poor enforcement, inadequate political will to tackle difficult environmental problems, and lack of coordination among countries that have reefs are some of the major barriers in effective conservation of coral reefs. Many coral reef countries lack trained personnel, equipment, and financial resources to effectively conserve coral reefs, establish marine protected areas, and enforce regulations. This lack of resources is often exacerbated by a poor awareness of the problems facing coral reefs and their significance in local economies and related ecosystems.

Most of the human activities causing loss or degradation of coral reefs are believed to be the result of ignorance rather than deliberate actions. A crucial approach toward conserving the coral reefs and improving their management, therefore, is to spread awareness among government and business officials as well as the general population of the importance of coral reefs and related ecosystems and to encourage communities, companies, and governments to take steps to protect them. Community leaders and decision makers should become familiar with the issues of coral reefs, marine environments, and resource protection so that these can be reflected in planning and policy. In particular, the issue of incorporating the full environmental and waste management costs of programs and developments should be recognized and addressed early in the policy planning process.

There have been some new initiatives toward the conservation of coral reefs in recent years. The World Summit on Sustainable Development (2002) called for a major international effort to reduce losses in biodiversity, including the biodiversity on coral reefs. Some international nongovernmental organizations (NGOs) are responding to this call by combining their expertise and resources to establish networks of marine protected areas and improve management capacity, particularly in high biodiversity regions of southeast Asia and western Pacific. Some of these NGOs have developed rapid assessment methods to select sites for urgent protection and also designed tools to assist resource managers protect reefs from global change stresses.

  • Biodiversity; Ecosystems; El-Niño–Southern Oscillation; Global Environmental Change; Habitat Protection; Sustainable Development.

  • A. Guilcher, Coral Reef Geomorphology (John Wiley & Sons, 1988).
  • International Coral Reef Information Network, “What Makes Coral Reefs So Special? (cited May 2006).
  • C. Wilkinson, ed., Status of Coral Reefs of the World: 2004, Vol. 1 (Australian Institute of Marine Science, 2004).
  • Ambika P. Gautam
    Asian Institute of Technology, Thailand
    Copyright © 2007 by SAGE Publications, inc.

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