Coral Reefs: The Forgotten Rain Forests of the Sea

Coral Reefs: The Forgotten Rain Forests of the Sea
▪ 1998
by Clive R. Wilkinson
      Because they harbour great concentrations of biodiversity, coral reefs have been called the rain forests of the sea. With hundreds of species of corals and fishes frequently found on a single reef, metre for metre these undersea ecosystems may even exceed tropical rain forests as the most species-rich places on Earth. Ironically, however, reefs have been far less studied—until now. In 1992 scientists at the seventh International Coral Reef Symposium in Guam raised a global alarm. They estimated that 10% of the world's coral reefs were effectively lost, an additional 30% were under immediate threat, and another 30% could be destroyed by 2050. To focus the world's attention on the plight of coral reefs, governments, organizations, and individuals around the world have recognized 1997 as the International Year of the Reef (IYOR).

 Even the most concerned researchers agree that coral reefs are remarkably resilient, having withstood such massive forces as periodic temperature fluctuations, ice ages, volcanic eruptions, tropical storms, and flooding for about 35 million years. Recent evidence, however, suggests that while reefs have survived the assaults of nature, they may be succumbing to an unrelenting barrage of human-induced stresses. Steady increases in sediment runoff onto reefs; excessive mining of coral sand and rock for building; increases in pollution, particularly from agriculture and domestic sewage; and chronic overexploitation of reef resources have resulted in widespread reef damage and, in some cases, ecological collapse. The most endangered reefs are located along some of the world's most heavily populated coastlines—Asia, East Africa, and the Caribbean, including the Florida Keys (see Map—> ).

      Among the most alarming threats to reefs is the increase in destructive fishing practices. The poison cyanide, for example, was being used routinely in the capture of fish for the live fish trade, a billion-dollar business that supplies seafood to Chinese restaurants in Hong Kong and nearby regions, as well as to Taiwan and Singapore. Fishermen liberally douse the reefs with cyanide in concentrations that temporarily stun large fish but indiscriminately kill smaller animals, including the corals themselves. The use of toxins, however, accounts for only part of the damage. With the help of compressed air, fishermen now can dive as deep as 40 m (130 ft), where they are able to flush dazed escapees from reef crevices by demolishing the fishes' refuges with crowbars.

      Even more devastating is the wholesale harvesting of fish during critical spawning periods. Particularly targeted are coral trout and other groupers (family Serranidae) and the spectacular humphead wrasse (Chelinus undulatus). Once or twice each year, fish from all parts of the reef congregate at a single location, usually a place swept by ocean currents so that their larvae are washed away from the reef's plankton eaters, including the corals, into the relative safety of the open ocean. Intent on spawning and therefore less cautious than normal, the fish are vulnerable to unscrupulous fishermen, who can wipe out all the breeding species on a reef within hours.

      Studies conducted on reefs off the coasts of places as far apart as Jamaica, southern Japan, and Kenya have shown that eliminating these large fish can have disastrous consequences. Large fish serve as beneficial grazers, helping to check the growth of algae that threatens to smother the corals. In addition, without a diverse army of fish predators, populations of other marine organisms explode, including sea urchins that wreak havoc by grazing everything in their path, even juvenile corals, and the rampaging crown-of-thorns starfish (Acanthaster planci), the scourge of coral colonies throughout the Indo-Pacific.

      Coral reefs also may be suffering from less-direct, but no-less-damaging, forces. Many scientists suspect that rising ocean temperatures due to global warming are compounding the extent and severity of coral bleaching. Increases in temperature of only one or two degrees can stress corals, causing them to expel the symbiotic algae known as zooxanthellae that they harbour in their stomach cells. The algae not only give corals their brilliant colours (without them corals appear white or "bleached") but also supply them with the surplus energy and nutrients they need to build reefs. Satellite images, especially of the Caribbean and parts of the Pacific, show distinct correlations between large areas of bleaching and increased sea-surface temperatures. In time and under optimal conditions, reefs can recover. Scientists, however, have documented an alarming reef mortality.

      Some researchers suspect that these rising temperatures and other stresses such as pollution may be causing corals to lose their resistance to once-minor ailments. In the last decade alone, scientists have documented about eight new diseases of corals. Even very large, century-old corals appear to be succumbing to these previously unknown maladies.

      In 1993 concerned scientists realized that it would be necessary to involve the public, particularly communities dependent on reef resources, in rescuing the reefs. In 1994 small-island nations met in Barbados to discuss their concerns about reef destruction and rising sea levels. Many of these countries have few resources other than coral reefs; some are built on coral islands only a few metres above the surrounding reefs. Together they formed the International Coral Reef Initiative, a global effort that has drawn the world's attention to the plight of coral reefs and spawned numerous other monitoring and management initiatives, including the Global Coral Reef Monitoring Network. In one of the projects sponsored by the network, leading coral-reef scientists train personnel in government natural-resource agencies and universities in the basic methods of assessing the health of corals and reef-fish populations.

      To highlight reef issues and challenges further, Robert Ginsburg of the University of Miami, Fla., proposed that 1997 be designated the International Year of the Reef. Among the hands-on projects launched under IYOR auspices was Reef Check, coordinated by Gregor Hodgson of the Hong Kong University of Science and Technology. Between June and August hundreds of scientists and recreational divers measured indicators of human activities on 300 reefs in 30 countries. This first global survey of the human impact on coral reefs provided valuable data on reef damage due to blast or cyanide fishing, overharvesting of marine organisms, and boat and anchor collisions.

      Preliminary results from the Reef Check reconnaissance were announced at a press conference in Hong Kong on October 16. The report confirmed what recreational divers had been reporting for several years—coral reefs were being abused by people throughout the world. The data showed that although some pristine reefs were found, few were in excellent condition. Even the most remote reefs had been heavily fished for sharks, lobsters, giant clams, and, most troubling, large predator fish such as grouper and snapper. In many of the reefs surveyed in Southeast Asia, these marketable species were completely absent.

      IYOR also targeted children by means of interactive educational activities. Coral reef scientists, for example, prepared teaching kits for primary and secondary schools. Children learned about coral reef values and problems through painting, writing, song, and dance competitions. Even a new computer game entitled Murder Under the Microscope was developed, in which players solved problems of reef degradation by enlisting the input of stakeholders in decision making and management of reef resources.

      The World Bank helped promote coral reef education and awareness by producing and distributing an award-winning hour-long video, The Fragile Ring of Life. The documentary explored reef problems through the eyes of some of the millions of people whose livelihoods depend on ecologically healthy marine environments. Finding solutions will not be easy, but as Charles Birkeland of the University of Guam's Marine Laboratory observed, people "need to develop a new paradigm for the exploitation of coral reefs, a new perspective that might also be a framework for our management of the Earth as a whole."

Clive R. Wilkinson is coordinator of the Global Coral Reef Monitoring Network at the Australian Institute of Marine Science, Townsville, Queen., Australia.

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Universalium. 2010.

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