great barrier reef

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).^[1] 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. In reality, it is made up of many millions of tiny organisms, known as coral polyps. The Great Barrier Reef was also selected as a World Heritage Site in 1981.^[2] CNN has labelled it one of the seven natural wonders of the world.^[3]

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.

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 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).^[4]

The research outcomes funded by the CRC Reef Research Centre estimates the present, living reef structure at 6,000 to 8,000 years old, formed upon coral 'skeletons' dating back half a million years.^[5] 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, a northern region of Western Australia.^[6]

Species of the Great Barrier Reef

33 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-bellied 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. ^[7]

Environmental threats

Runoff and coastal development

The coastline of north eastern Australia has no major rivers, (except during tropical flood events caused by tropical cyclones). It also has several major urban centres including Cairns, Townsville, Mackay, Rockhampton and the industrial city of Gladstone.

Cairns and Townsville are the largest of these coastal cities with populations of approximately 150,000 each.^[8] 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.^[9]

It was thought that the mechanism behind poor water quality affecting the reefs was 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. ^[10]

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. ^[11]

Global warming and coral bleaching

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.^[12]

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,^[13], others suggest that while reefs may die in certain areas, other areas will become habitable for corals, and form coral reefs. ^[14]

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'.^[15]

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. An individual adult of this species can wipe out up to 6 square metres of living reef in a single year.^[16]

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. Reduction of water quality associated with agriculture can cause the crown-of-thorns starfish larvae to thrive. Overfishing of its natural predators, such as the Giant Triton, is also considered to contribute to an increase in the number of crown-of-thorns starfish.^[17]

Overfishing

The unsustainable overfishing of keystone species, such as the Giant Triton, can cause disruption to food chains vital to life on the reef. 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.^[18] 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.^[19]

Shipping and oil

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.^[20]

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.^[21] 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.^[22]

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. ^{citation needed]} Although there is no oil drilling on the reef, oil spills are still a frequent occurrence there.

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.^[23] For these 70 or so clan groups, the Reef is also an important part of their Dreamtime.

The Reef first became known to Europeans when the HM Bark Endeavour, captained by explorer James Cook, ran aground there on June 11, 1770 and sustained considerable damage. It was finally saved after lightening the ship as much as possible and re-floating it during an incoming tide. One of the most famous wrecks was that of the HMS Pandora, which sank on August 29, 1791 killing 35. The Queensland Museum has been leading archaeological digs to the Pandora since 1983. ^[24]

Management

Main article: Great Barrier Reef Marine Park

In 1975, the Government of Australia created the Great Barrier Reef Marine Park and defined what activities were prohibited on the Reef.^[25] 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. Australia has also developed a comprehensive Biodiversity Action Plan, of which a key element is protection of the Great Barrier Reef.^[26]

In July 2004, a new zoning plan was brought into effect for the entire Marine Park, and has been widely acclaimed as a new global benchmark for the conservation of marine ecosystems.^[27] While protection across the Marine Park was improved, the highly protected zones increased from 4.5% to over 33% (ie. greater than 115,000km²) within the world’s largest network of highly protected areas.^{citation needed]}

Tourism

As the largest commercial activity in the region, it has been estimated that tourism in the Great Barrier Reef generates over AU$4000 million annually.^[28] There are approximately two million visitors to the Great Barrier Reef each year.^[29] Although most of these visits are managed in partnership with the marine tourism industry, there are some very popular areas near shore (such as Green Island) that have suffered damage due to overfishing and land based run off. Any impacts from tourist activity merely exacerbate the more pronounced effects of land based run-off and overfishing.^{citation needed]} The 2003 Pixar film, Finding Nemo, featured the Great Barrier Reef as a setting.

Fishing

The fishing industry in the GBR, controlled by the Queensland Government, is worth AU$1000 million annually.^[30] It employs approximately 2000 people, and fishing in the Reef is pursued commercially, for recreation, and as a traditional means for feeding one's family. Wonky holes in the reef provide particularly productive fishing areas.

Gallery

References

External links

• Great Barrier Reef Marine Park Authority
• CRC Reef Research Centre
• 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)