Chain of coral reefs and islands about 2,000 km/1,250 mi long, in the Coral Sea,
off the east coast of Queensland, Australia, about 16–241 km/10–150 mi offshore. The Great Barrier Reef is made up of 3,000 individual reefs, and is believed to be the world's largest living organism. Only ten navigable channels break through the reef. The most valuable products of the reef are pearls, pearl shells, trepangs (edible sea slugs), and sponges. The reef is popular with tourists. In 1976 it became a Marine Park and in 1981 it was declared a World Heritage Site by UNESCO.
Annually, a few nights after the full moon in November, 135 species of hard coral release their eggs and sperm for fertilization and the sea turns pink. The phenomenon, one of the wonders of the natural world, was discovered in 1983, and is triggered by a mechanism dependent on the moon, the tides, and water temperatures.
Features The Great Barrier Reef follows the curve of Australia's east coast, from New Guinea in the north to Lady Elliot Island, off the coast of Bundaberg, in the south. The reef is nearest the land at its north end, where in some places it is only 15 km/10 mi offshore. It can be seen at low tide, and is broken up by many deep channels, the chief of which are the Bligh entrance, the Olinda entrance, the Raime entrance, and Flinders passage. The reef is an immense natural breakwater, the coral rock forming a structure larger than all artificially-made structures on Earth combined. The channel between the reef and the coast is a valuable route of communication owing to the calmness of the sea, but careful navigation is necessary, especially at night, when the reef can scarcely be discerned. In addition to over 300 species of coral and anemones and sponges, around 1,500 species of tropical fish have been identified in the area, together with other animals such as turtles, sharks, dolphins, and clams. The main islands include Heron Island, Lady Musgrave Island, Wilson Island, Lady Elliot's Island, Great Keppel Island, and Brampton Island.
Formation The Great Barrier Reef is not a single reef, but thousands of individual reefs, shoals, atolls, coral cogs, and larger islands. It was constructed by coral polyps (an animal) of which around 350 species have been identified. These creatures are only able to flourish in warm waters where average sea temperatures are above 21°C/70°F. It is the combination of the skeletons of these polyps, their associated coral algae, hydrocorals, and other plant and animal waste matter which have gradually formed the reef over the past 25 million years, that is since the Miocene geological period, as the continental shelf has gradually subsided.
Tourism Centres on the east coast of Australia for tourism to the Great Barrier Reef are Townsville, Cairns, Port Douglas, Cook Town, and Mackay. The number of tourists visiting the reef rose from 900,000 in 1985 to 1.7 million in 1996.
Environmental issues and marine research Environmental issues became a serious concern in the 1960s when oil exploration was halted by strike action. In 1967 an application for a calcium carbonate mine was rejected. Between 1970 and 1972 a Royal Commission, set up by the state of Queensland and the Federal Government, resulted in the establishment of the Great Barrier Reef Marine Park Authority in 1976. The park was expanded in 1979 and again in 1982. The Australian Museum set up a marine research station on Lizard Island in the 1970s and the Australian Institute of Marine Science was established in Townsville in 1973.
In early 1996 there was an outbreak of the coral-eating starfish, the crown-of-thorns; a similar outbreak in the late 1970s caused damage to 500 reefs, and 150 were totally stripped of coral. Such outbreaks occur naturally every decade, but a report by the Reefwatch organization concluded that they now occur every three to five years, giving the coral no time to recover. In August 2001, the Australians backed moves to eradicate the starfish from parts of the reef.
Since World War II the tourist industry related to the reef has become increasingly important, and research has focused on the long-term effects of heavy tourism on the corals, marine life of the reef, and the natural environment of the reef's tropical islands. A report by the World Wide Fund for Nature (WWF) in June 2001 found that many areas of the reef are endangered by the combined effects of pollution and global warming. Parts of the reef have been subject to periods of bleaching, when unusually warm sea water causes corals that make up the reef to expel their algae; the corals then turn white. An increase in the rate of bleaching events is linked to global warming. The report found that the recovery of bleached coral is endangered by unnaturally high amounts of sediments flowing from rivers onto the reef. The mud and other contaminants reduce the amount of sunlight available to the corals, slowing their recovery. Most of the high sediment flow is due to agricultural practices on land adjacent to the reef.
A report commissioned by Greenpeace in 1999 says that much of the Great Barrier Reef will die within about 40 years unless action is taken to stop global warming, as corals in southern and central parts of the Great Barrier Reef are likely to be severely affected by increases in sea temperatures.
Great Barrier Reef Marine Park Authority
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