Great Barrier Reef

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Satellite image of a part of the Great Barrier Reef. Photo courtesy of NASA.

The Great Barrier Reef is the world's largest coral reef. The reef is located in the Coral Sea, off the coast of Queensland in north-east Australia. It stretches over 2000 kilometres in length and can be seen from space.

The Great Barrier Reef is a large system of about 900 islands and over 3000 coral reefs, which mostly lie some distance from the mainland coastline. Due to its vast biodiversity, warm clear waters and its accessibility from the floating guest facilities called 'live aboards', the reef is a very popular destination for tourists, especially scuba divers. Many cities along the Queensland coast offer boat trips to the reef on a daily basis. Several continental islands have been turned into resorts.

The Great Barrier Reef is sometimes referred to as the single largest organism in the world. In reality it is made up of many millions of tiny organisms, as are all coral formations.

A large part of the reef is protected by the Great Barrier Reef Marine Park.

Geology and Geography

Age

The Great Barrier Reef first became known to Europeans when the explorer Captain James Cook ran [[wiktionary:aground|aground]] there, on June 11, 1770. The Great Barrier Reef however was known to Indigenous Australians whose occupation of the Australian continent is thought to extend back 40,000 to 60,000 years or more.

According to the authority administering the reef, (PDF) the current reef structure is believed to have begun growing on an older platform about 18,000 years ago, but the oldest datable 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 present reef structure at 6,000 to 8,000 years old, formed upon coral dating back half a billion years. Reefs fluctuate (grow and recede) as the sea level changes. The remains of an ancient barrier reef similar to the Great Barrier Reef can be found in The Kimberley.

Species of the Great Barrier Reef

Giant Clam on 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. Also, large populations of dugongs live there. Six species of sea turtle come to the reef to breed - Green Sea Turtle, Leatherback Sea Turtle, Hawksbill turtle, Loggerhead Sea Turtle, Flatback Turtle, and Olive Ridley. Over 200 species of birds (including 40 species of waterbirds) live on the Great Barrier Reef, including the White-breasted sea eagle and Roseate tern. 5000 species of mollusc have been recorded on the Great Barrier Reef including the Giant clam and the Cone snail. 14 species of sea snake live on the Great Barrier Reef. More than 1500 species of fish live on the reef, including the Clownfish, Red Bass, Red-Throat Emperor, and several species of Snapper and Coral Trout. 400 species of corals, both hard corals and soft corals are found on the Reef. There are 15 species of seagrass near the Reef that attract the dugongs and sea turtles. 500 species of marine algae or seaweed live on the Reef. The irukandji jellyfish also lives on the Reef.

Environmental threats

Runoff and coastal development

Cairns and Townsville are the largest of these coastal cities with populations of approximately 150,000 each. 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. Principal agricultural activity is sugar cane farming in the wet tropics and cattle grazing in the dry tropics regions. Both are considered significant factors affecting water quality.

Global warming and coral bleaching

Bioerosion (coral damage) such as this may be caused by coral bleaching.[link]

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 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.

As demonstrated in 1998, 2002 and 2006, corals expel their photosynthesising zooxanthellae and turn colourless, revealing their white calcium carbonate skeletons, under the stress of waters that remain too warm for too long. If the water does not cool within about a month the coral will die. Australia experienced its warmest year on record in 2005. Abnormally high sea temperatures during the summer of 2005/2006 have caused massive coral bleaching in the Keppel Island group.

Global warming may have triggered the collapse of reef ecosystems throughout the tropics. Increased global temperatures are thought by some to bring more violent tropical storms, but reef systems are naturally resilient and recover from storm battering. While some believe that an upward trend in temperature will cause much more coral bleaching, others point to data that suggests that the global temperature has never changed by more than a degree for a very long time. (See Global warming controversy).

Crown-of-Thorns starfish

Crown-of-Thorns starfish

Crown-of-Thorns starfish are thought to be natural predators of corals. The exact origin of this species is unknown, and it is only speculated that they are native to Australia. They have a life cycle with many eggs released annually, that enables this species to boom-and-bust like locusts in a desert. The cycles are thought to be enhanced by a decline in water quality such as excess nutrients from farm runoff. Since scientists and other users of the reef have been able to observe crown-of-thorns outbreaks, about one third of the entire system has been affected since the 1960s. The link to an animation of Crown-of-Thorns starfish outbreaks illustrates, using data collected from the Australian Institute of Marine Science Long Term Monitoring Program, the occurrence of Crown-of-Thorns starfish outbreaks. In addition, the Giant Triton, a natural predator of the Crown-of-Thorns starfish, is often overfished as its shell is prized by collectors.

Fishing

Effects of Fishing

Up until mid-2004, only 4.6% of the Great Barrier Reef World Heritage area was protected from fishing. (It is now one third).

The main impacts from fishing are:

• Overfishing of keystone species (eg. Giant Triton)
• Pollution from boats
• Bycatch (species that they’re not looking for, e.g. crabs, dolphins, turtles, dugongs)
• Reef damage (anchors, nets)
• Habitat destruction from trawling

Shipping and oil

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.Reef Dreams: Working The Reef TV documenary, Australian Broadcasting Commission, broadcast 6 July 2006 [link] Captain Cook in the Endeavour nearly came to grief that way, being utterly becalmed and pushed towards the reef by the swell. Right up to within 80 metres of it the water was so deep that no ground (to anchor against) could be felt with 220 metres of line.[Free eBook: Captain Cook's Journal During the First Voyage Round the World] at Project Gutenberg, for 15 August 1770

Ships also have been known to discharge waste and foreign species in their ballast water and the antifouling paint on the hulls is toxic. Also, it is suspected that the Reef is the cap to an oil trap, as it is calcium carbonate. Before it was World Heritage listed, there was some speculation about drilling for oil and gas there. Although there is no oil drilling on the reef, oil spills are still a frequent occurrence there.

Human use of the Great Barrier Reef

Traditional

Many Indigenous Australian and Torres Strait Islander clan groups have been associated with the Great Barrier Reef. For those groups, the Reef is an important part of their Dreamtime. In the Wulguru language, the Great Barrier Reef is known as "Mulgur".ReefED (unknown date). reefED - GBR Traditional Owners [online]. Available: http://www.reefed.edu.au/explorer/traditional_owners/index.html [Access date: 28 May 2006]

Contemporary

Management

In 1975, the Government of Australia enacted the [Great Barrier Reef Marine Park Act 1975], which created the Great Barrier Reef Marine Park Authority, and defined what acts were prohibited on the Reef. The Government of Australia manages the reef through the Great Barrier Reef Marine Park Authority and in partnership with the Government of Queensland, 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.

The Great Barrier Reef was selected as a World Heritage Site in 1981.UNEP World Conservation Monitoring Centre (1980). World Heritage Sites - Great Barrier Reef World Heritage Area [online]. Available: http://sea.unep-wcmc.org/sites/wh/gbrmp.html [Access date: 10 June 2006]

Tourism

Gallery

References

External links

• [Official site of the Great Barrier Reef Marine Park]
• [Scientific research centre for the Great Barrier Reef]
• [Biological monitoring of coral reefs of the GBR]
• [Photos of the Great Barrier Reef - Terra Galleria]
• [Australia Underwater] - All about diving in Australia - includes photo gallery from all around Australia.
• [Great Barrier Reef (World Wildlife Fund)]
• [Dive into the Great Barrier Reef] from National Geographic
• [Protecting The Great Barrier Reef World Heritage Area] (Comprehensive pamphlet from the GBRMPA)

World Heritage Sites in Australia

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