Coral reef in the Coral Sea off the NE coast of Australia, part of the Coral Sea Islands Territory; 50150 km/3090 mi offshore and 2000 km/1200 mi long; the largest accumulation of coral known, yielding trepang, pearl-shell, and sponges to divers; the surf is violent and dangerous, but the intervening channel, clustered with atolls, forms a safe, shallow passage connected by several navigable channels with the deeps of the Coral Sea; major tourist area; world heritage site.
The Great Barrier Reef is the world's largest coral reef system, composed of roughly 3,000 individual reefs and 900 islands, that stretch for 2,600 kilometres (1,616 mi), covering an area of approximately 344 400 km The reef is located in the Coral Sea, off the coast of Queensland in north-east Australia. A large part of the reef is protected by the Great Barrier Reef Marine Park.
The Great Barrier Reef can be seen from outer space and is sometimes referred to as the single largest organism in the world. The Great Barrier Reef was also selected as a World Heritage Site in 1981.
Geology and Geography
According to the Great Barrier Reef Marine Park Authority, the current, living reef structure is believed to have begun growing on an older platform about 18,000 years ago, but the oldest dated coral on the reef now is a species of Porites known as boulder coral, which is only about 1,000 years old (it grows about 1 centimetre per year).
The research outcomes funded by the CRC Reef Research Centre estimates the age of the present, living reef structure at 6,000 to 8,000 years old, formed upon coral 'skeletons' dating back half
a million years. The remains of an ancient barrier reef similar to the Great Barrier Reef can be found in The Kimberley, a northern region of Western Australia.
Species of the Great Barrier Reef
30 species of whales, dolphins, or porpoises have been recorded in the Great Barrier Reef, including the Dwarf Minke Whale, Indo-Pacific Humpback Dolphin and the Humpback Whale. Over 200 species of birds (including 40 species of waterbirds) live on the Great Barrier Reef, including the White-bellied Sea Eagle and Roseate Tern. 5000 species of mollusc have been recorded on the Great Barrier Reef including the Giant Clam and various nudibranches and cone snails. 14 species of sea snake live on the Great Barrier Reef. Unlike most reef environments worldwide, the Great Barrier Reef is the only one where the water catchment area is home to industrialised urban areas and where extensive areas of coastal lands and rangelands have been used for agricultural and pastoral purposes.
Due to the range of human uses made of the water catchment area adjacent to the Great Barrier Reef some 400 of the 3000 reefs are within a risk zone where water quality has declined owing to sediment and chemical runoff from farming, and to loss of coastal wetlands which are a natural filter.
It is thought that the mechanism behind poor water quality affecting the reefs is due to increased light and oxygen competition from algae, but it has also been suggested that poor water quality encourages the spread of infectious diseases among corals. The long-term monitoring program has found an increase in incidences of coral disease in the period 1999-2002, although they dispute the claim that on the Great Barrier Reef, coral diseases are caused by anthropogenic pollution.
Copper, a common industrial pollutant found in the waters of the Great Barrier Reef, has been shown to interfere with the development of coral polyps.
Climate change
Some people believe that the most significant threat to the status of the Great Barrier Reef and of the planet's other tropical reef ecosystems is climate change - comprising of global warming and the El Niño effect. Many of the corals of the Great Barrier Reef are currently living at the upper edge of their temperature tolerance, as demonstrated in the coral bleaching events of the summers of 1998, 2002 and most recently 2006. While some believe that an upward trend in temperature will cause much more coral bleaching, others suggest that while reefs may die in certain areas, other areas will become habitable for corals, and form coral reefs.
Reef scientist Terry Done has predicted a 1 degree rise in global temperature would result in 82 percent of the reef bleached, 2 degrees resulting in 97 percent and 3 degrees resulting in 'total devastation'.
Crown-of-thorns starfish
The crown-of-thorns starfish is a coral reef predator that preys on coral polyps by climbing onto them, extruding the stomach over them, and releasing digestive enzymes to then absorb the liquified tissue.
Although large outbreaks of these starfish are believed to occur in natural cycles, human activity in and around the Great Barrier Reef can worsen the effects. Fishing also impacts the reef through increased pollution from boats, by-catch of unwanted species (such as dolphins and turtles) and reef habitat destruction from trawling, anchors and nets. As of the middle of 2004, approximately one-third of the Great Barrier Reef Marine Park is protected from species removal of any kind, including fishing, without written permission.
Shipping
Shipping accidents are also a real concern, as several commercial shipping routes pass through the Great Barrier Reef. From 1985-2001, there were 11 collisions and 20 groundings on the inner Great Barrier Reef shipping route. The leading cause of shipping accidents in the Great Barrier Reef is human error.
Although the route through the Reef is not easy, reef pilots consider it safer than outside the Reef in the event of mechanical failure since a ship can sit safely while being repaired. On the outside, wind and swell will push a ship towards the reef and the water is deep right up to the Reef so anchoring is impossible.
Oil
It is suspected that the Great Barrier Reef is the cap to an oil trap. In 1970, two Royal Commissions were ordered "into exploratory and production drilling for petroleum in the area of the Great Barrier Reef". Oil drilling is not permitted on the Great Barrier Reef, yet oil spills are still considered "one of the biggest threats to the reef", with a total of 282 oil spills between 1987-2002.
Human use of the Great Barrier Reef
The Great Barrier Reef has long been known to and utilised by Indigenous Australian people, whose occupation of the continent is thought to extend back 40,000 to 60,000 years or more.
Management
After the Royal Commissions' findings, in 1975, the Government of Australia created the Great Barrier Reef Marine Park and defined what activities were prohibited on the Great Barrier Reef. The park is managed, in partnership with the Government of Queensland, through the Great Barrier Reef Marine Park Authority to ensure that it is widely understood and used in a sustainable manner. A combination of zoning, management plans, permits, education and incentives (such as eco-tourism certification) are used in the effort to conserve the Great Barrier Reef.
In 2006, a review was undertaken of the Great Barrier Reef Marine Park Act 1975. Some recomendations of the review are that there should be no further zoning plan changes until 2013, and that every five years, a peer-reviewed Outlook Report should be published, examining the health of the Great Barrier Reef, the management of the Reef, and environmental pressures.
Tourism
As the largest commercial activity in the region, it has been estimated in 2003 that tourism in the Great Barrier Reef generates over AU$4 billion annually. (A 2005 estimate puts the figure at AU$5.1 billion.) There are approximately two million visitors to the Great Barrier Reef each year. But by far, the most popular tourist activities on the Great Barrier Reef are snorkelling and diving. The outer part of the Great Barrier Reef is favoured for such activities, due to water quality.
Management of tourism in the Great Barrier Reef is geared towards making tourism ecologically sustainable. A daily fee is levied that goes towards research of the Great Barrier Reef. Policies on cruise ships, bareboat charters, and anchorages limit the traffic on the Great Barrier Reef. The 2003 Pixar film, Finding Nemo, featured the Great Barrier Reef as a setting.
Fishing
The fishing industry in the Great Barrier Reef, controlled by the Queensland Government, is worth AU$1 billion annually. It employs approximately 2000 people, and fishing in the Great Barrier Reef is pursued commercially, for recreation, and as a traditional means for feeding one's family.
Gallery
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Clownfish on the Great Barrier Reef |
Satellite image of the northernmost part of the Great Barrier Reef |
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