The Great Barrier Reef is the world's largest coral reef system

The Great Barrier Reef is the world's largest coral reef system, ASUS F80S CPU Fan composed of roughly 3,000 individual reefs and 900 islands that stretch for 2,600 kilometres (1,616 mi) and cover an area of approximately 344,400 km².^[3][4] The reef is located in the Coral Sea, off the coast of Queensland in northeast Australia. A large part of the reef is protected by the Great Barrier Reef Marine Park. HP Pavilion dv5-1058eo CPU Fan The Great Barrier Reef's environmental pressures include lowered water quality from runoff including suspended sediment, excess nutrients, pesticides, and fluctuations in salinity. The effects of climate change, including increased temperatures, storms and coral bleaching. Cyclic outbreaks of the crown-of-thorns starfish, IBM 13N5182 CPU Fan overfishing which disrupts food chains, and shipping routes which can result in oil spills or improper ballast discharge also cause damage to the reef. Water quality was first identified as a threat to the Great Barrier Reef in 1989.^[5] Thirty "major rivers" and hundreds of small streams comprise the Great Barrier Reef catchment area, which covers 423,000 square kilometres (163,000 sq mi) of land.^[6] IBM Thinkpad T30 2366-AA3 CPU Fan Queensland has several major urban centres on the coast including Cairns, Townsville, Mackay, Rockhampton and the industrial city of Gladstone. Dredging in the Port of Gladstone is raising concern after dead and diseased fish where found in the harbour. Cairns and Townsville are the largest of the coastal cities, with populations of approximately 150,000 each.^[7] IBM Thinkpad T30 CPU Fan There are many major water quality variables affecting coral reef health including water temperature, salinity, nutrients,suspended sediment concentrations,^[8] and pesticides.^[6] The species in the Great Barrier Reef area are adapted to tolerable variations in water quality however when critical thresholds are exceeded they may be adversely impacted. HP 535438-001 CPU Fan River discharges are the single biggest source of nutrients,^[9] providing significant pollution of the Reef during tropical flood events with over 90% of this pollution being sourced from farms.^[8] Due to the range of human uses made of the water catchment area adjacent to the Great Barrier Reef, DELL Inspiron N3010 CPU Fan some 700 of the 3000 reefs^[10] are within a risk zone where water quality has declined owing to the naturally acidic sediment and chemical runofffrom farming, and to coastal development and the loss of coastal wetlands which are a natural filter.^[11] Industries in the water catchment area are cotton growing, comprising approximately 262 km²; HP Pavilion dv6-3070tx CPU Fan 340 dairy farms with an average area of 2 km² each, 158 km² cattle grazing, 288 km² horticulture including banana growing, sugarcane farming, and cropping of approximately 8,000 km² wheat, 1,200 km² barley, and 6,000 to 7000 km² sorghum and maize.^[12] Fertiliser use in the cotton, dairy, beef, horticulture and sugar industries is essential to ensure productivity and profitability. IBM 41W5269 CPU Fan However, fertiliser and byproducts from sugar cane harvesting methods form a component of surface runoff into the Great Barrier Reef lagoon.^[12][13] 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.^[13] ASUS A8H CPU Fan Copper, a common industrial pollutant in the waters of the Great Barrier Reef, has been shown to interfere with the development of coral polyps.^[14] Flood plumes are flooding events associated with higher levels of nitrogen and phosphorus.^[15] In February 2007, due to a monsoonal climate system, SONY UDQFRZH13CF0 CPU Fan plumes of sediment runoff have been observed reaching to the outmost regions of the reef.^[16] Runoff is especially concerning in the region south of Cairns, as it receives over 3000 mm of rain per year and the reefs are less than 30 kilometres (19 mi) away from the coastline.^[17] Farm run off is polluted as a result of overgrazing and excessive fertiliser and pesticide use. HP COMPAQ 2510P CPU Fan Mud pollution has increased by 800% and inorganic nitrogen pollution by 3,000% since the introduction of European farming practices on the Australian landscape. This pollution has been linked to a range of very significant risks to the reef system, including intensified outbreaks of the coral-eating Crown of Thorns Starfish which contributed to a loss of 66% of live coral cover on sampled reefs in 2000.^[18] APPLE 661-4951 CPU Fan It is thought that the mechanism behind excess nutrients affecting the reefs is due to increased light and oxygen competition from algae,^[9] but unless herbivory is unusually low, this will not create a phase shift from the Great Barrier Reef being primarily made up of coral to being primarily made up of algae.^[19] HP Pavilion dv6-3034ca CPU Fan It has been suggested that poor water quality due to excess nutrients encourages the spread of infectious diseases among corals.^[20] In general, the Great Barrier Reef is considered to have low incidences of coral diseases.^[21] Skeletal Eroding Band, a disease of bony corals caused by the protozoan Halofolliculina corallasia, HP G56-126NR CPU Fan affects 31 species of corals from six families on the reef.^[22] 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.^[23] Compaq Presario C556CA CPU Fan Elevated nutrient concentrations result in a range of impacts on coral communities and under extreme conditions can result in a collapse. It also affects coral by promoting phytoplankton growth which increases the number of filter feeding organisms that compete for space. SONY Vaio VGN-NR360E CPU Fan Excessive inputs of sediment from land to coral can lead to reef destruction through burial, disruption of recruitment success or deleterious community shifts. Sediments affect coral by smothering them when particles settle out, reducing light availability and potentially reducing photosynthesis and growth. HP Pavilion dv5170us CPU Fan Coral reefs exist in seawater salinities from 25 to 42%. Salinity impacts to corals are increased by other flood-related stresses.^[9] The Australian and Queensland Governments have committed to act to protect the reef,^[24] and water quality monitoring programmes are in place.^[6] SONY Vaio VPC-EE3WFX/WI CPU Fan However, theWorld Wildlife Fund has criticised that progress against these commitments has been slow, saying that as many as 700 reefs are at risk from sediment runoff. Most 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, consisting chiefly of global warming and the El Niño effect.^[ HP G56-126NR CPU Fan and turn colourless, revealing their white calcium carbonate skeletons, under the stress of waters that remain too warm for too long. At this stage the coral is still alive, and if the water cools, the coral can regain its zooxanthellae.^[27] If the water does not cool within about a month, the coral will die of starvation. Australia experienced its warmest year on record in 2005. HP 3MLX8TATP20 CPU Fan Abnormally high sea temperatures during the summer of 2005-2006 have caused massive coral bleaching in the Keppel Islandgroup. Most scientists studying the issue believe that climate change poses a massive threat to the future of the Great Barrier Reef. SONY Vaio VGN-NW240F/S CPU Fan A draft report by the UN Intergovernmental Panel on Climate Change, the world's preeminent gathering of climate scientists, states that the Great Barrier Reef is at grave risk and will be "functionally extinct" by 2030, warning that coral bleaching will likely become an annual occurrence.^[28] SONY Vaio VPC-EB1Z0E/B CPU Fan However, a few scientists hold that coral bleaching may in some cases be less of a problem than the mainstream believes. Professor Ridd, from James Cook University in Townsville was quoted in The Australian (a conservative newspaper) as saying; "They are saying bleaching is the end of the world, but when you look into it, that is a highly dubious proposition".Compaq Presario CQ60-514NR CPU Fan Research by scientist Ray Berkelmans "... has documented astonishing levels of recovery on the Keppel outcrops devastated by bleaching in 2006." ^[29] A related article in The Australian newspaper goes on to explain that; "Those that expel their zooxanthellae have a narrow opening to recolonise with new, temperature-resistant algae before succumbing. Toshiba Satellite X205-S9800 CPU Fan In the Keppels in 2006, Berkelmans and his team noticed that the dominant strain of zooxanthellae changed from light and heat-sensitive type C2, to more robust types D and C1." ^[30] Nevertheless, most coral reef researchers anticipate severely negative effects from climate change already occurring, and potentially disastrous effects as climate change worsens. ASUS G2P CPU Fan The future of the Reef may well depend on how much the planet's climate changes, and thus, on how high atmospheric greenhouse gas concentration levels are allowed to rise. On 2 September 2009, a report by the Australian Great Barrier Reef Marine Park Authorityrevealed that if carbon dioxide levels reached 450 parts per million corals and reef habitats will be highly vulnerable. Compaq Presario CQ60-430SA CPU Fan If carbon dioxide levels are managed at or below 380 parts per million they will be only moderately vulnerable and the reefs will remain coral-dominated.^[31] 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, DELL BFB0505HA CPU Fan but reef systems are naturally resilient and recover from storm battering. Most people agree that an upward trend in temperature will cause much more coral bleaching;^[25][32] others suggest that while reefs may die in certain areas, other areas will become habitable for corals, and new reefs will form.^[33] HP Pavilion dv5-1272et CPU Fan However, the rate at which the mass bleaching events occur is estimated to be much faster than reefs can recover from, or adjust to.^[27] However, Kleypas et al. in their 2006 report suggest that the trend towards ocean acidification indicates that as the sea's pH decreases, corals will become less able to secrete calcium carbonate.^[34] Toshiba AB7005HX-SB3 CPU Fan In 2009, a study showed that Porites corals, the most robust on the Great Barrier Reef, have slowed down their growth by 14.2% since 1990. It suggested that the cause was heat stress and a lower availability of dissolved calcium to the corals.^[35] Climate change and global warming are one of the greatest threats to the reef.^[25] Toshiba Satellite A500-18T CPU Fan A temperature rise of between two and three degrees Celsius would result in 97% of the Great Barrier Reef being bleached every year.^[36] Reef scientist Terry Done has predicted that a one-degree rise in global temperature would result in 82% of the reef bleached, two degrees resulting in 97% and three degrees resulting in "total devastation".^[37HP Pavilion dv5-2135dx CPU Fan ^] A predictive model based on the 1998 and 2002 bleaching events has concurred that a temperature rise of three degrees would result in total coral mortality.^[38] Climate change has implications for other forms of life on the Great Barrier Reef as well - some fish's preferred temperature range lead them to seek new areas to live, ASUS EEE PC 1201NL CPU Fan thus causing chick mortality in seabirds that prey on the fish. Also, in sea turtles, higher temperatures mean that the sex ratio of their populations will change, as the sex of sea turtles is determined by temperature. The habitat of sea turtles will also shrink. The Crown-of-Thorns Starfish is a coral reef predator which preys on coral polyps by climbing onto them, SONY Vaio VGN-NW240D/T CPU Fan extruding its stomach over them, and releasing digestive enzymes to absorb the liquified tissue. An individual adult of this species can eat up to six square metres of living reef in a single year.^[39] Geological evidence suggests that the Crown-of-Thorns Starfish has been part of the Great Barrier Reef's ecology for "at least several thousand years", Compaq Presario CQ60-418DX CPU Fan but there is no geological evidence for Crown-of-Thorns outbreaks.^[40] Large outbreaks of these starfish can devastate reefs. In 2000, an outbreak contributed to a loss of 66% of live coral cover on sampled reefs in a study by the CRC Reefs Research Centre.^[18] Although large outbreaks of these starfish are believed to occur in natural cycles, SONY Vaio VGN-NW240D CPU Fan 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.^[41] SONY VGN-BX197XP CPU Fan The CRC Reef Research Centre defines an outbreak as when there are more than 30 adult starfish in an area of one hectare. The unsustainable overfishing of keystone species, such as the Giant Triton and sharks, can cause disruption to food chains vital to life on the reef. Fishing also impacts the reef through increased pollution from boats, Toshiba Satellite L645D-S4056 CPU Fan by-catch of unwanted species (such as dolphins and turtles) and reef habitat destruction fromtrawling, anchors and nets.^[43] Overfishing of herbivore populations can cause algal growths on reefs. The Batfish Platax pinnatus has been observed to significantly reduce algal growths in studies simulating overfishing.^[44] Toshiba AB7805HX-GB3 CPU Fan Sharks are fished for their meat, and when they are part of bycatch, it is common to kill the shark and throw it overboard, as there is a belief that they interfere with fishing.^[45] As of 1 July 2004, approximately one-third of the Great Barrier Reef Marine Park is protected from species removal of any kind, including fishing, without written permission.^[46] However, illegal poaching is not unknown in these no-take zones. Toshiba Satellite L500-208 CPU Fan Shipping accidents continue to be perceived as a threat, as several commercial shipping routes pass through the Great Barrier Reef. The GBRMPA estimates that about 6000 vessels greater than 50 metres (164 ft) in length use the Great Barrier Reef as a route.^[47] From 1985 to 2001, 11 collisions and 20 groundings occurred along the Great Barrier Reef shipping route, HP 535441-001 CPU Fan with human error identified as the leading cause of shipping accidents.^[48] Reef pilots have stated that they consider the reef route safer than outside the reef in the event of mechanical failure, since a ship can sit safely while being repaired.^[49] The inner route is used by 75% of all ships that travel over the Great Barrier Reef.^[47] Toshiba Satellite P100-444 CPU Fan As of 2007, over 1,600 known shipwrecks have occurred in the Great Barrier Reef region.^[50] Waste and foreign species discharged from ships in ballast water (when purging procedures are not followed) are a biological hazard to the Great Barrier Reef.^[51] Tributyltin (TBT) compounds found in some antifouling paint on ship hulls leaches into seawater and is toxic to marine organisms and humans; as of 2002, efforts are underway to restrict its use.^[52] HP Pavilion dv7-3114eo CPU Fan In April 2010, the bulk coal carrier Shen Neng 1 ran aground on the Great Barrier Reef, causing the largest grounding scar to date. The spill caused damage to a 400,000sqm section of the Great Barrier Reef and the use of oil dispersant resulted in oil spreading to reef islands 25 km away. HP Mini 110-1125SA CPU Fan It was suspected that the Great Barrier Reef is the cap to an oil trap, after a 1923 paper suggested that it had the right rock formation to support "oilfields of great magnitude". After the Commonwealth Petroleum Search Subsidies Act of 1957, exploration activities increased in Queensland, including a well drilled atWreck Island in the southern Great Barrier Reef in 1959.^[54] HP KSB06105HA CPU Fan In the 1960s, drilling for oil and gas was investigated throughout the Great Barrier Reef,^[55][56] by seismic and magnetic methods in the Torres Strait, along "the eastern seaboard of Cape York to Princess Charlotte Bay" and along the coast from Cooktown toFraser Island. Compaq Presario CQ60-210eo CPU Fan In the late 1960s, more exploratory wells were drilled near Wreck Island in the Capricorn Channel, and near Darnley Island in the Torres Strait, but "all results were dry".^[54] In 1970, responding to concern about oil spills such as the Torrey Canyon, two Royal Commissions were ordered "into exploratory and production drilling for petroleum in the area of the Great Barrier Reef".HP Pavilion dv7-2250sf CPU Fan After the Royal Commissions, the federal and state governments ceased allowing petroleum drilling on the Great Barrier Reef.^[4][57] A study in 1990 concluded that the reef is too young to contain oil reserves.^[58] Oil drilling remains prohibited on the Great Barrier Reef, yet oil spills due to shipping routes are still a threat to the reef system, HP 434678-001 CPU Fan with a total of 282 oil spills between 1987-2002. Tropical cyclones are a cause of ecological disturbance to the Great Barrier Reef. The types of damage caused by tropical cyclones to the Great Barrier Reef is varied, including fragmentation, sediment plumes, and decreasing salinity following heavy rains (Tropical Cyclone Joy). HP G60-230us CPU Fan The patterns of reef damage are similarly 'patchy'. From 1910–1999, 170 cyclones' paths came near or through the Great Barrier Reef. Most cyclones pass through the Great Barrier Reef within a day.^[59] In general, compact corals such as Porites fare better than branching corals under cyclone conditions. HP Pavilion dv6365us CPU Fan The major damage caused by Tropical Cyclone Larry was to underlying reef structures, and breakage and displacement of corals, which is overall consistent with previous tropical cyclone events.^[60] Severe tropical cyclones hit the Queensland coast every 200 to 300 years;^[21] however, HP 535439-001 CPU Fan during the period 1969–1999 most cyclones in the region were very weak – category one or two on the Australian Bureau of Meteorology scale.^[59] On 2 February 2011, Severe Tropical Cyclone Yasi struck northern Queensland and caused severe damage to a stretch of hundreds of kilometres within the Great Barrier Reef. COMPAQ 6910c CPU Fan The corals could take a decade to recover fully. Cyclone Yasi had wind speeds of 290 kilometers per hour. HP G62-110SO CPU Fan On the second day of the 2013 round of the biennial training exercise 'Talisman Saber', in which 28,000 US and Australian military personnel conduct joint activities over a three-week period,four unarmed bombs were dropped into the Great Barrier Reef by two US AV-8B Harrier jets that were unable to land with the weight of the weapons. IBM Lenovo IdeaPad G510 CPU Fan To minimize potential harm to the reef, the four bombs, weighing a total 1.8 metric tons (4,000 pounds), were dropped into more than 50 meters (164 ft) of water away from the reef's coral structures. The bomb drop was originally planned to occur at the Townshend Island bombing range, DELL Precision M6400 CPU Fan but after controllers reported that the area was not clear of hazards, the emergency jettison occurred. Australian senator Larissa Waters responded to the news by asking, "Have we gone completely mad? Is this how we look after our World Heritage area now? Letting a foreign power drop bombs on it?" SONY Vaio VPC-EB290X CPU Fan Human impact on coral reefs is significant. Coral reefs are dying around the world.^[1] In particular, coral mining, pollution (organic and non-organic), overfishing, blast fishing and the digging of canals and access into islands and bays are serious threats to these ecosystems. HP Envy 17-1090eo CPU Fan Coral reefs also face high dangers from pollution, diseases, destructive fishing practices and warming oceans.^[2] In order to find answers for these problems, researchers study the various factors that impact reefs. The list of factors is long, including the ocean's role as a carbon dioxide sink, Toshiba Satellite A210-1CF CPU Fan atmospheric changes, ultraviolet light, ocean acidification, biological virus, impacts of dust storms carrying agents to far flung reefs, pollutants, algal blooms and others. Reefs are threatened well beyond coastal areas. In 2008 estimates assembled from coral reef specialists from around the world indicated that 19% of the existing area of coral reefs has been already been lost, Dell Vostro 3450 CPU Fan and that a further 15% are likely to be lost over the subsequent 10–20 years.^[3] Only 46% of the world’s reefs could be currently regarded as in good health.^[3] About 60% of the world's reefs may be at risk due to destructive, human-related activities. The threat to the health of reefs is particularly strong in Southeast Asia, Toshiba Satellite A10-103 CPU Fan where 80% of reefs are endangered. By the 2030s, 90% of reefs are expected to be at risk from both human activities and climate change; by 2050, all coral reefs will be in danger. In the Caribbean Sea and tropical Pacific, direct contact between coral and 40–70% of common seaweeds cause bleaching and death of coral tissue viaallelopathic competition. Compaq Presario A900 CTO CPU Fan The lipid-soluble extracts of seaweeds that harmed coral tissues also produced rapid bleaching. At these sites bleaching and mortality was limited to areas of direct contact with seaweeds or their extracts. The seaweed ten expanded to occupy the dead coral's habitat.^[6] However, as of 2009, only 4% of coral reefs worldwide had more than 50% algal coverage. ACER Aspire 4736ZG CPU Fan Further, there is no recent global trend towards algal dominance.^[2] Competitive seaweed and other algae thrive in nutrient-rich waters in the absence of sufficient herbivorous predators. Herbivores include fish such asparrotfish, surgeonfish, tangs and unicornfish. Over fishing, particularly selective over fishing, can unbalance coToshiba Satellite A10-103 CPU Fan ral ecosystems by encouraging the excessive growth of coral predators. Predators that eat living coral, such as the crown-of-thorns starfish, are called corallivores. Coral reefs are built from stony coral, which evolved with large amounts of the waxcetyl palmitate in their tissues. SONY MCF-519PAM05 CPU Fan Most predators find this wax indigestible.^[7] The crown-of-thorns starfish is a large (up to one meter) starfish protected by long, venomous spines. Its enzyme system dissolves the wax in stony corals, and allows the starfish to feed on the living animal. Starfish face predators of their own, such as the giant triton sea snail. SONY Vaio VPC-EB290X CPU Fan However, the giant triton is valued for its shell and has been over fished. As a result, crown-of-thorns starfish populations can periodically grow unchecked, devastating reefs. Although some aquarium fish species can reproduce in aquaria (such as Pomacentridae), most (95%) are collected from coral reefs.^[ HP Pavilion dv7-2043cl CPU Fan Intense harvesting, especially in South-East Asia (including Indonesia and the Philippines), damages the reefs. This is aggravated by destructive fishing practices, such as cyanide and blast fishing. Most (80–90%) aquarium fish from the Philippines are captured with sodium cyanide. HP Pavilion dv7-2130ev CPU Fan This toxic chemical is dissolved in sea water and released into areas where fish shelter. It narcotizes the fish, which are then easily captured. However, most fish collected with cyanide die a few months later from liver damage.^[ Moreover, many non-marketable specimens die in the process.HP 608772-001 CPU Fan It is estimated that 4,000 or more Filipino fish collectors have used over 1,000,000 kilograms (2,200,000 lb) of cyanide on Philippine reefs alone, about 150,000 kg per year.^[12] A major catalyst of cyanide fishing is poverty within fishing communities. In countries like the Philippines that regularly employ cyanide, more than thirty percent of the population lives below the poverty line.^[13] Toshiba Satellite A100-194 CPU Fan Dynamite fishing is another destructive method for gathering fish. Sticks of dynamite, grenades, or home-made explosives are detonated in the water. This method of fishing kills the fish within the main blast area, along with many unwanted reef animals. The blast also kills the corals in the area, eliminating the reef's structure, HP Pavilion tx1205/ CT CPU Fan destroying habitat for the remaining fish and other animals important for reef health.^[12] Muroami is the destructive practice of covering reefs with nets and dropping large stones onto the reef to produce a flight response among the fish. The stones break and kill the coral. Muroami was generally outlawed in the 1980s.^[12] HP Pavilion dv6640ep CPU Fan Fishing gear damages reefs via direct physical contact with the reef structure and substrate. Gill nets, fish traps, and anchors break branching coral and cause coral death through entanglement. When fishermen drop lines by coral reefs, the lines entangle the coral. The fisher cuts the line and abandons it, leaving it attached to the reef. COMPAQ Presario CQ42-401TU CPU Fan