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Great Barrier Reef

Research warned in March 2017 that Australia’s Great Barrier Reef can be saved only if urgent steps are taken to tackle climate change. The study, published in the journal Nature, said parts of the world’s largest coral system will never fully recover from repeated bleaching, caused by spikes in the water temperature. The Great Barrier Reef faces localized threats, such as the run-off of pesticides from farms and overfishing, but scientists believe its future depends on immediate efforts to reduce global warming.

The Great Barrier Reef is the largest object on Earth made by living things. In fact, it's so big that astronautscan see it from space. The Great Barrier Reef extends for 2,000 kilometers along the northeastern coast of Australia. It is not a single reef, but a vast maze of reefs, passages, and coral cays (islands that are part of the reef). The Great Barrier Reef is the largest coral system that has ever existed. It is made up of about 2,900 reefs, though only about six percent are coral reefs.

Coral reefs are made up of hundreds of thousands of tiny animals called corals. Each coral hasmicroscopic algae living inside it. These algae are what make coral reefs so colorful. The corals provide the algae with a home and nutrients, and in return, the algae produce food that the corals need to survive. Teaming with life, the region is home to a wide variety of marine animals including over 1500 species of fish, sea snakes, turtles, birds, mollusks, and dugongs.

The Great Barrier Reef extends up the north-eastern coast of the continent from the Tropic of Capricorn (at the Cumberland Islands and Swain Reef) for 2300 km to Torres Strait, where it merges with the reefs along southern Papua New Guinea. It includes thousands of individual reefs of a bewildering variety: patch reefs, linear or ribbon reefs, crescentic reefs, submerged shoals, lagoonal reefs, and planar reefs. All the modern reefs have evolved in the last 6000 years since sea level returned to its approximate present position, but they are only thin veneers of recent coral limestone, usually less than 10 m thick, over older reefs, mostly constructed during the last interglacial age and then modified by karst solution during the long exposure of low sea level during the last ice age.

The segment of the Great Barrier Reef near Cape Melville is typified by a ribbon reef (also called a wall reef or linear reef) at the outer edge of the continental shelf. Farther south, the barrier reef system consists of large patch reefs or horseshoe-shaped crescentic reefs on a wider continental shelf. North of 16°S latitude the continental shelf becomes narrower, and the edge of the shelf is delineated by narrow ribbon reefs on which the powerful southeastern swell breaks in violence. The reef margin is so dangerous that few accurate soundings have been made, but divers have reported a depth of 400 m at a point 300 m seaward of Hicks Reef. Depths of 1000 m are common within 1 km of the ribbon reefs, confirming that they define the edge of the continental shelf. Behind the ribbon reefs are a maze of submerged shoals, lagoonal reefs (those with a central atoll-like lagoon), and planar reefs (in which the central depression of a crescentic or lagoonal reef has been filled with coral debris to become a low-tide platform). The maximum depth among the shelf reefs is only 36 m. North of Cape Melville the ribbon reef approaches to within 25 km of the mainland, the narrowest part of the channel behind the entire Great Barrier Reef.

Captain James Cook's discovery of the Great Barrier Reef was a near tragedy. He had sailed north for 1400 km along the mainland coast for many weeks in early 1770, unaware of the great reef system that was closing in on him from the east. On June 11, he went aground on Endeavour Reef near the place now named Cooktown. After beaching and repairing the ship, he threaded his way through the shelf reefs to Lizard Island, a granitic island that rises 360 m above sea level in the eastern part of the image. From the summit of Lizard Island, he planned a course that took him through the outer ribbon reef at Cooks Passage, at the extreme east edge of this image. It is ironic that, although the crew cheered at their harrowing escape from the Great Barrier Reef, after sailing north for a time in terrible weather, Cook was forced to run inside the reef once again. The tidal current miraculously swept HMS Endeavour, without any rudder control, back inside the reef through a pass. From that time on, Cook was able to navigate safely through the Torres Strait and north to Dutch settlements in present Indonesia. The first written description of the Great Barrier Reef is also one of the epics of maritime history.

The Great Barrier Reef is internationally renowned as a place of great beauty and ecological significance and is protected as a Marine Park and a World Heritage Area. It is of immense social, economic and cultural value to the people of Australia. While the Great Barrier Reef is recognised as one of the best-managed coral reef systems in the world, climate-related events have already caused significant impacts. Coral bleaching affected over 50% of reefs in both 1998 and 2002, and seabird nesting failures were observed in 2002 and 2005. These are just the first of many anticipated impacts of climate change on the Reef. However, climate change is not the only threat to the Reef; rather, it's effects will interact with other pressures such as degraded water quality and unsustainable fishing.

Climate change is now acknowledged as one of the most serious threats to the long-term health of coral reefs. Already, in many places around the world such as the Maldives, Seychelles and Palau, coral bleaching has effectively destroyed over 50% of reefs. This loss of corals, triggered by unusually high sea temperatures, has far-reaching implications for reef ecosystems. Corals provide the ecological foundations that underpin enormous biodiversity and productivity, and provide food and income to hundreds of millions of people throughout the tropical world. There will also be a range of other effects of climate change on reef ecosystems, many of which may be equally destructive but are only just beginning to be understood.

Tourism has been identified as a critical issue in the management of the Great Barrier Reef Marine Park (GBRMP). About 1.6 million tourists visit the Great Barrier Reef (GBR) region each year, and generate an income of over $1 billion per year in direct value. A further estimated one million visitor nights per year are spent in accommodation on island resorts within the boundaries of the GBRMP. The rapid increase in numbers of tourists and development of tourism infrastructure development on the GBR which caused great concern in the 1980s has stabilised since 1995. Recreational use of the GBR region by coastal residents is also high, and in many circumstances, the impacts of recreational users can be impossible to separate from those of commercial tourism activities.

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Page last modified: 26-03-2017 19:18:46 ZULU