112-716: The Great Barrier Reef Foundation is an Australian non-profit organisation established in 1999 to help protect and preserve the Great Barrier Reef . The foundation was formed in response to the first mass coral bleaching of the reef in 1998. Climate change is the number one threat to the Great Barrier Reef and coral reefs globally. The foundation is the lead charity for the Great Barrier Reef, funding more than 300 projects with over 400 partners bringing together science, traditional owners , community, citizen science, government, business and non-governmental organizations in
224-461: A bicarbonate ion ( HCO − 3 ) and a hydrogen ion ( H ). The presence of free hydrogen ions ( H ) lowers the pH of the ocean, increasing acidity (this does not mean that seawater is acidic yet; it is still alkaline , with a pH higher than 8). Marine calcifying organisms , such as mollusks and corals , are especially vulnerable because they rely on calcium carbonate to build shells and skeletons. A change in pH by 0.1 represents
336-472: A "long-term reorganisation of the reef ecosystem if the trend continues." The Great Barrier Reef Marine Park Act 1975 (section 54) stipulates an Outlook Report on the Reef's health, pressures, and future every five years. The last report was published in 2019. In March 2022, another mass bleaching event has been confirmed, which raised further concerns about the future of this reef system, especially when considering
448-449: A "shark control" program ( shark culling ) that deliberately kills sharks throughout Queensland, including in the Great Barrier Reef. Environmentalists and scientists say that this program harms the marine ecosystem ; they also say it is "outdated, cruel and ineffective". The Queensland "shark control" program uses shark nets and drum lines with baited hooks to kill sharks in the Great Barrier Reef – there are 173 lethal drum lines in
560-500: A 26% increase in hydrogen ion concentration in the world's oceans (the pH scale is logarithmic, so a change of one in pH units is equivalent to a tenfold change in hydrogen ion concentration). Sea-surface pH and carbonate saturation states vary depending on ocean depth and location. Colder and higher latitude waters are capable of absorbing more CO 2 . This can cause acidity to rise, lowering the pH and carbonate saturation levels in these areas. There are several other factors that influence
672-581: A depth of 150 metres (490 ft) due to their need for sunlight, and cannot grow above sea level. When Queensland edged into tropical waters 24 million years ago, some coral grew, but a sedimentation regime quickly developed with erosion of the Great Dividing Range ; creating river deltas , oozes and turbidites , unsuitable conditions for coral growth. 10 million years ago, the sea level significantly lowered, which further enabled sedimentation. The reef's substrate may have needed to build up from
784-506: A disease of bony corals caused by the protozoan Halofolliculina corallasia , affects 31 coral species. According to a 2012 study by the National Academy of Sciences , since 1985, the Great Barrier Reef has lost more than half of its corals with two-thirds of the loss occurring from 1998 due to the factors listed before. In 2022, the northern and central parts of the reef had the highest amount of coral cover since monitoring began, but
896-450: A doubling of the chlorophyll in the water leads to a tenfold increase in the crown-of-thorns starfish larvae's survival rate. Sediment runoff from farming carries chemicals into the reef environment also reduces the amount of light available to the corals decreasing their ability to extract energy from their environment. Pesticides used in farming are made up of heavy metals such as lead, mercury, arsenic and other toxins are released into
1008-499: A draft decision, expressing serious concern about the impact of coral bleaching on the Great Barrier Reef. The draft decision also warned Australia that it will not meet the targets of the Reef 2050 report without considerable work to improve water quality. Climate change has implications for other forms of reef life – some fish's preferred temperature range leads them to seek new habitat, thus increasing chick mortality in predatory seabirds. Climate change will also affect
1120-486: A lawsuit against the government of Queensland to stop shark culling in the Great Barrier Reef. In March 2015, the Australian and Queensland's governments formed a plan for the protection and preservation of the reef's universal heritage until 2050. This 35 years plan, titled "Reef 2050 Plan" is a document proposing possible measures for the long-term management of the pollution, climate change and other issues that threaten
1232-495: A quarter of total anthropogenic CO 2 emissions. The latest key findings about the observed changes and impacts from 2019 include: It is virtually certain that the global ocean has warmed unabated since 1970 and has taken up more than 90% of the excess heat in the climate system [...]. Since 1993, the rate of ocean warming has more than doubled [...]. Marine heatwaves have very likely doubled in frequency since 1982 and are increasing in intensity [...]. By absorbing more CO2,
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#17328443050841344-411: A rate of about 0.1 per decade this century. The acidic water breaks down the materials that coral and shell building creatures need to grow. Another key threat faced by the Great Barrier Reef is pollution and declining water quality . The rivers of north-eastern Australia pollute the Reef during tropical flood events. Over 90% of this pollution comes from farm runoff . 80% of the land adjacent to
1456-500: A reduction in nutrient supply. The reduction in ocean productivity is due to the "combined effects of warming, stratification, light, nutrients and predation". The full ecological consequences of the changes in calcification due to ocean acidification are complex but it appears likely that many calcifying species will be adversely affected by ocean acidification. Increasing ocean acidification makes it more difficult for shell-accreting organisms to access carbonate ions, essential for
1568-490: A result of ocean warming which both reduces water circulation and also reduces the oxygen content of that water, while the solubility of oxygen declines as the temperature rises. Overall ocean oxygen concentrations are estimated to have declined 2% over 50 years from the 1960s. The nature of the ocean circulation means that in general these low oxygen regions are more pronounced in the Pacific Ocean . Low oxygen represents
1680-779: A stress for almost all marine animals. Very low oxygen levels create regions with much reduced fauna . It is predicted that these low oxygen zones will expand in future due to climate change, and this represents a serious threat to marine life in these oxygen minimum zones. The second area of concern relates to coastal waters where increasing nutrient supply from rivers to coastal areas leads to increasing production and sinking organic matter which in some coastal regions leads to extreme oxygen depletion, sometimes referred to as dead zones . These dead zones are expanding driven particularly by increasing nutrient inputs, but also compounded by increasing ocean stratification driven by climate change. Satellite image analysis reveals that
1792-583: A wide diversity of life and was selected as a World Heritage Site in 1981. CNN labelled it one of the Seven Natural Wonders of the World in 1997. Australian World Heritage places included it in its list in 2007. The Queensland National Trust named it a state icon of Queensland in 2006. A large part of the reef is protected by the Great Barrier Reef Marine Park , which helps to limit
1904-721: Is coral bleaching on these reefs, because they are sensitive to even minor temperature changes. So a small increase in water temperature could have a significant impact in these environments. Another example is loss of sea ice habitats due to warming. This will have severe impacts on polar bears and other animals that rely on it. The effects of climate change on oceans put additional pressures on ocean ecosystems which are already under pressure by other impacts from human activities . Presently (2020), atmospheric carbon dioxide (CO 2 ) levels of more than 410 parts per million (ppm) are nearly 50% higher than preindustrial levels. These elevated levels and rapid growth rates are unprecedented in
2016-473: Is a distinct feature of the East Australian Cordillera division. It reaches from Torres Strait (between Bramble Cay , its northernmost island, and the south coast of Papua New Guinea ) in the north to the unnamed passage between Lady Elliot Island (its southernmost island) and Fraser Island in the south. Lady Elliot Island is located 1,915 km (1,190 mi) southeast of Bramble Cay as
2128-485: Is a very popular destination for tourists, especially in the Whitsunday Islands and Cairns regions. Tourism is an important economic activity for the region, generating over AUD$ 3 billion per year. In November 2014, Google launched Google Underwater Street View in 3D of the Great Barrier Reef. A March 2016 report stated that coral bleaching was more widespread than previously thought, seriously affecting
2240-459: Is an important part of the global carbon cycle . The photosynthesis in surface waters consumes nutrients (e.g. nitrogen and phosphorus) and transfers these nutrients to deep water as the organic matter produced by photosynthesis sinks upon the death of the organisms. Productivity in surface waters therefore depends in part on the transfer of nutrients from deep water back to the surface by ocean mixing and currents. The increasing stratification of
2352-623: Is an unavoidable result of the Earth's energy imbalance , which is primarily caused by rising levels of greenhouse gases. Between pre-industrial times and the 2011–2020 decade, the ocean's surface has heated between 0.68 and 1.01 °C. The majority of ocean heat gain occurs in the Southern Ocean . For example, between the 1950s and the 1980s, the temperature of the Antarctic Southern Ocean rose by 0.17 °C (0.31 °F), nearly twice
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#17328443050842464-510: Is becoming more intensified. Sea ice decline occurs more in the Arctic than in Antarctica , where it is more a matter of changing sea ice conditions. The process of photosynthesis in the surface ocean releases oxygen and consumes carbon dioxide. This photosynthesis in the ocean is dominated by phytoplankton – microscopic free-floating algae. After the plants grow, bacterial decomposition of
2576-508: Is crucial not just in the production of the Atlantic Meridional Overturning Circulation, which has worldwide weather and climate ramifications, but it is also significant because stratification controls the movement of nutrients from deep water to the surface. This increases ocean productivity and is associated with the compensatory downward flow of water that carries oxygen from the atmosphere and surface waters into
2688-528: Is different for the Antarctic Ocean (at 55°S), where the highest warming (0.3 °C per century) has been observed at a depth of 4500 m. Marine heatwaves also take their toll on marine life: For example, due to fall-out from the 2019-2021 Pacific Northwest marine heatwave, Bering Sea snow crab populations declined 84% between 2018 and 2022, a loss of 9.8 billion crabs. The ocean temperature varies from place to place. Temperatures are higher near
2800-460: Is expected to become an annual occurrence. In 2020, a study found that the Great Barrier Reef has lost more than half of its corals since 1995 due to warmer seas driven by climate change. As global warming continues, corals will not be able to keep up with increasing ocean temperatures. Coral bleaching events lead to increased disease susceptibility, which causes detrimental ecological effects for reef communities. In July 2017 UNESCO published in
2912-565: Is how they've collected much of their data regarding threats to the Great Barrier Reef. In addition, the Reef 2050 Water Quality Improvement Plan was announced in 2018 in order to help transition local communities, agricultural organizations and industries to more sustainable practices. This plan will join the Queensland government and the Great Barrier Reef Marine Park Authority to manage the amounts of runoff that reach
3024-488: Is located in the Coral Sea , off the coast of Queensland , Australia , separated from the coast by a channel 160 kilometres (100 mi) wide in places and over 61 metres (200 ft) deep. The Great Barrier Reef can be seen from outer space and is the world's biggest single structure made by living organisms. This reef structure is composed of and built by billions of tiny organisms, known as coral polyps . It supports
3136-407: Is projected to continue. Ocean productivity under a very high emission scenario ( RCP8.5 ) is very likely to drop by 4-11% by 2100. The decline will show regional variations. For example, the tropical ocean NPP will decline more: by 7–16% for the same emissions scenario. Less organic matter will likely sink from the upper oceans into deeper ocean layers due to increased ocean stratification and
3248-453: Is responsible for bringing up cold, nutrient-rich water from the depths of the ocean, a process known as upwelling . Seawater consists of fresh water and salt, and the concentration of salt in seawater is called salinity. Salt does not evaporate, thus the precipitation and evaporation of freshwater influences salinity strongly. Changes in the water cycle are therefore strongly visible in surface salinity measurements, which has been known since
3360-535: Is the ongoing decrease in the pH of the Earth's ocean . Between 1950 and 2020, the average pH of the ocean surface fell from approximately 8.15 to 8.05. Carbon dioxide emissions from human activities are the primary cause of ocean acidification, with atmospheric carbon dioxide (CO 2 ) levels exceeding 422 ppm (as of 2024 ). CO 2 from the atmosphere is absorbed by the oceans. This chemical reaction produces carbonic acid ( H 2 CO 3 ) which dissociates into
3472-399: Is thought that the poor water quality is due to increased light and oxygen competition from algae . Farming fertiliser runoff release nitrogen , phosphorus , and potassium into the oceanic ecosystem, and these limiting nutrients cause massive algal growth which eventually leads to a reduction in oxygen available for other creatures in a process called eutrophication . This decreases
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3584-492: The Aboriginal Australian and Torres Strait Islander peoples, and is an important part of local groups' cultures and spirituality. The first European to sight the Great Barrier Reef was James Cook in 1770, who sailed and mapped the east coast of Australia. On 11 June 1770 Cook's ship, HMS Endeavour , ran aground on a shoal south of the present-day location of Cooktown , requiring seven weeks to repair. It
3696-720: The Coral Sea Basin formed, coral reefs began to grow in the Basin, but until about 25 million years ago, northern Queensland was still in temperate waters south of the tropics – too cool to support coral growth. The Great Barrier Reef's development history is complex; after Queensland drifted into tropical waters, it was largely influenced by reef growth and decline as sea level changed. Reefs can increase in diameter by 1 to 3 centimetres (0.39 to 1.18 in) per year, and grow vertically anywhere from 1 to 25 cm (0.39 to 9.84 in) per year; however, they grow only above
3808-522: The Great Barrier Reef Foundation in 2018. The announcement of the grant was subject to backlash as the grant had avoided proper tender and transparency processes. The Great Barrier Reef contributes to the overall wellbeing of the marine biome. Numerous species of aquatic plants, fish and megafauna use the reef for feeding, shelter and mating. Threats such as ocean acidification , pollution runoff and outbreaks of destructive species like
3920-437: The Great Dividing Range with some larger hills (most of which were themselves remnants of older reefs or, in rare cases, volcanoes ). The Reef Research Centre, a Cooperative Research Centre , has found coral 'skeleton' deposits that date back half a million years. The Great Barrier Reef Marine Park Authority (GBRMPA) considers the earliest evidence of complete reef structures to have been 600,000 years ago. According to
4032-581: The Ok Tedi Mine in Papua New Guinea are a potential pollution risk for the far northern Great Barrier Reef and Torres Strait regions. Some 67% of corals died in the reef's worst-hit northern section, the ARC Centre of Excellence for Coral Reef Studies report said. The runoff problem is exacerbated by the loss of coastal wetlands which act as a natural filter for toxins and help deposit sediment. It
4144-576: The crown-of-thorns starfish have brought about the decline of this ecosystem. These threats to the reef are not only a danger to the organisms inhabiting it, but also the economy of this region, a large part of which relies on revenue from ecotourism of the Great Barrier Reef. The Australian government has had the goal of protecting this World Heritage Site since 1972 when they created The Australian Institute of Marine Science. The Australian and Queensland governments have contributed about $ 142.5 million to their National Environmental Science Program which
4256-439: The equator and lower at the poles . As a result, changes in total ocean heat content best illustrate ocean warming. When compared to 1969–1993, heat uptake has increased between 1993 and 2017. Ocean heat content (OHC) or ocean heat uptake (OHU) is the energy absorbed and stored by oceans . To calculate the ocean heat content, it is necessary to measure ocean temperature at many different locations and depths. Integrating
4368-426: The geological record's 55 million years. The source for this excess CO 2 is clearly established as human-driven, reflecting a mix of fossil fuel burning, industrial, and land-use/land-change emissions . The idea that the ocean serves as a major sink for anthropogenic CO 2 has been discussed in scientific literature since at least the late 1950s. Several pieces of evidence point to the ocean absorbing roughly
4480-428: The olive ridley . The green sea turtles on the Great Barrier Reef have two genetically distinct populations , one in the northern part of the reef and the other in the southern part. Fifteen species of seagrass in beds attract the dugongs and turtles, and provide fish habitat. The most common genera of seagrasses are Halophila and Halodule . Saltwater crocodiles live in mangrove and salt marshes on
4592-492: The 1930s. The long term observation records show a clear trend: the global salinity patterns are amplifying in this period. This means that the high saline regions have become more saline, and regions of low salinity have become less saline. The regions of high salinity are dominated by evaporation, and the increase in salinity shows that evaporation is increasing even more. The same goes for regions of low salinity that are becoming less saline, which indicates that precipitation
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4704-492: The 1980s. This is the result of human induced factors such as increased nutrient inputs ( nutrient pollution ) and climate change (in particular the warming of water temperatures). The parameters that affect the formation of HABs are ocean warming, marine heatwaves, oxygen loss , eutrophication and water pollution . These increases in HABs are of concern because of the impact of their occurrence on local food security, tourism and
4816-528: The AMOC deep ocean circulation is slow (it takes hundreds to thousands of years to circulate the entire ocean), it is slow to respond to climate change. Changes in ocean stratification are significant because they can influence productivity and oxygen levels. The separation of water into layers based on density is known as stratification. Stratification by layers occurs in all ocean basins. The stratified layers limit how much vertical water mixing takes place, reducing
4928-537: The AMOC is very likely to weaken over the course of the 21st century. A weakening of this magnitude could have a significant impact on global climate, with the North Atlantic being particularly vulnerable. Any changes in ocean currents affect the ocean's ability to absorb carbon dioxide (which is affected by water temperature) as well as ocean productivity because the currents transport nutrients (see Impacts on phytoplankton and net primary production ). Because
5040-555: The GBRMPA, the current, living reef structure is believed to have begun growing on the older platform about 20,000 years ago. The Australian Institute of Marine Science agrees, placing the beginning of the growth of the current reef at the time of the Last Glacial Maximum . At around that time, sea level was 120 metres (390 ft) lower than it is today. From 20,000 years ago until 6,000 years ago, sea level rose steadily around
5152-419: The Great Barrier Reef as well as mitigating crown-of-thorns starfish population flare-ups. Effects of global warming on oceans There are many effects of climate change on oceans . One of the most important is an increase in ocean temperatures . More frequent marine heatwaves are linked to this. The rising temperature contributes to a rise in sea levels due to the expansion of water as it warms and
5264-482: The Great Barrier Reef can be found in The Kimberley , Western Australia. The Great Barrier Reef World Heritage Area has been divided into 70 bioregions , of which 30 are reef bioregions. In the northern part of the Great Barrier Reef, ribbon reefs and deltaic reefs have formed; these structures are not found in the rest of the reef system. A previously undiscovered reef, 500 metres tall and 1.5 km wide at
5376-490: The Great Barrier Reef in warm waters up to 50 metres (160 ft) deep and are more common in the southern than in the northern section. None found in the Great Barrier Reef World Heritage Area are endemic, nor are any endangered. Six species of sea turtles come to the reef to breed: the green sea turtle , leatherback sea turtle , hawksbill turtle , loggerhead sea turtle , flatback turtle , and
5488-403: The Great Barrier Reef is the rising levels of ocean acidification in the ocean. Ocean acidification occurs when excess atmospheric carbon dioxide gets absorbed into the ocean. This causes a decrease in the pH and this alters the chemistry of the ocean's water. This reduces the amount of aragonite, a key mineral for coral to grow, in the water. The Great Barrier Reef is predicted to lose aragonite at
5600-690: The Great Barrier Reef is used for farming including intensive cropping of sugar cane, and major beef cattle grazing. Farming practices damage the reef due to overgrazing , increased run-off of agricultural sediments, nutrients and chemicals including fertilisers , herbicides and pesticides representing a major health risk for the coral and biodiversity of the reefs. According to a 2016 report, while higher regulation contributes to less overall pollution from "other land uses, such as industrial, mining, port development, dredging and urban development", these can still be locally significant. Sediments containing high levels of copper and other heavy metals sourced from
5712-449: The Great Barrier Reef. In Queensland, sharks found alive on the baited hooks are shot. Queensland's "shark control" program killed about 50,000 sharks from 1962 to 2018. Also, Queensland's "shark control" program has also killed many other animals (such as dolphins and turtles ) – the program killed 84,000 marine animals from 1962 to 2015, including in the Great Barrier Reef. In 2018, Humane Society International filed
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#17328443050845824-824: The Mermaid, Francis Price Blackwood in HMS Fly , Owen Stanley in the Rattlesnake, and Henry Mangles Denham in the Herald led to considerable navigational improvements, as they outlined the contrasting advantages and perils of the Inner Route (between Australia's east coast and the western edge of the reefs) and the Outer Route, in the open sea. The Great Barrier Reef supports an extraordinary diversity of life, including many vulnerable or endangered species , some of which may be endemic to
5936-563: The Reef Research Centre (RRC). Outbreaks are believed to occur in natural cycles, worsened by poor water quality and overfishing of the starfish's predators. The unsustainable overfishing of keystone species , such as the giant Triton , can disrupt food chains vital to reef life. Fishing also impacts the reef through increased water pollution from boats, by-catch of unwanted species (such as dolphins and turtles) and habitat destruction from trawling , anchors and nets. As of
6048-466: The areal density of a change in enthalpic energy over an ocean basin or entire ocean gives the total ocean heat uptake. Between 1971 and 2018, the rise in ocean heat content accounted for over 90% of Earth's excess energy from global heating . The main driver of this increase was caused by humans via their rising greenhouse gas emissions . By 2020, about one third of the added energy had propagated to depths below 700 meters. Ocean acidification
6160-426: The atmosphere and land. One result is an increase in the amount of energy available for tropical cyclones and other storms. Another result is a decrease in nutrients for fish in the upper ocean layers. These changes also reduce the ocean's capacity to store carbon . At the same time, contrasts in salinity are increasing. Salty areas are becoming saltier and fresher areas less salty. Warmer water cannot contain
6272-402: The atmosphere-ocean CO 2 exchange, and thus local ocean acidification. These include ocean currents and upwelling zones, proximity to large continental rivers, sea ice coverage, and atmospheric exchange with nitrogen and sulfur from fossil fuel burning and agriculture . Many ocean-related elements of the climate system respond slowly to warming. For instance, acidification of
6384-403: The base, was found in the northern area in 2020. There are no atolls in the system, and reefs attached to the mainland are rare. Fringing reefs are distributed widely, but are most common towards the southern part of the Great Barrier Reef, attached to high islands, for example, the Whitsunday Islands . Lagoonal reefs are found in the southern Great Barrier Reef, and further north, off
6496-402: The biodiversity in the affected areas, altering the species composition . A study by Katharina Fabricius and Glen Death of Australian Institute of Marine Science found that hard corals numbers were almost double on reefs that were far from agricultural areas. Fertilizers also increase the amount of phytoplankton available for the crown-of-thorns starfish larvae to consume. A study showed that
6608-416: The bottom of the ocean. This temperature stratification will increase as the ocean surface warms due to rising air temperatures. Connected to this is a decline in mixing of the ocean layers, so that warm water stabilises near the surface. A reduction of cold, deep water circulation follows. The reduced vertical mixing makes it harder for the ocean to absorb heat. So a larger share of future warming goes into
6720-544: The coast near the reef. Nesting has not been reported, and the salt water crocodile population in the GBRWHA is wide-ranging but low density. Around 125 species of shark , stingray , skates or chimaera live on the reef. Close to 5,000 species of mollusc have been recorded on the reef, including the giant clam and various nudibranchs and cone snails . Forty-nine species of pipefish and nine species of seahorse have been recorded. At least seven species of frog inhabit
6832-569: The coast of Princess Charlotte Bay . Crescentic reefs are the most common shape of reef in the middle of the system, for example the reefs surrounding Lizard Island . Crescentic reefs are also found in the far north of the Great Barrier Reef Marine Park, and in the Swain Reefs ( 20 – 22 degrees south ). Planar reefs are found in the northern and southern parts, near Cape York Peninsula , Princess Charlotte Bay, and Cairns. Most of
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#17328443050846944-459: The coming decades and beyond. Local subsidence , which may be natural but can be increased by human activity, can exacerbate coastal flooding. Coastal flooding will threaten hundreds of millions of people by 2050, particularly in Southeast Asia . Ocean currents are caused by temperature variations caused by sunlight and air temperatures at various latitudes, as well as prevailing winds and
7056-436: The context of each fishery . Climate change is modifying fish distributions and the productivity of marine and freshwater species. Climate change is expected to lead to significant changes in the availability and trade of fish products . The geopolitical and economic consequences will be significant, especially for the countries most dependent on the sector. The biggest decreases in maximum catch potential can be expected in
7168-422: The cover in the southern part had decreased and bleaching events occurred more frequently. The Great Barrier Reef Marine Park Authority considers the greatest threat to the Great Barrier Reef to be climate change, causing ocean warming which increases coral bleaching . Mass coral bleaching events due to marine heatwaves occurred in the summers of 1998, 2002, 2006, 2016, 2017 and 2020, and coral bleaching
7280-586: The crow flies . It includes the smaller Murray Islands . The plate tectonic theory indicates Australia has moved northwards at a rate of 7 cm (2.8 in) per year, starting during the Cenozoic . Eastern Australia experienced a period of tectonic uplift , which moved the drainage divide in Queensland 400 km (250 mi) inland. Also during this time, Queensland experienced volcanic eruptions leading to central and shield volcanoes and basalt flows. Some of these became volcanic islands . After
7392-426: The deep ocean will continue for millennia, and the same is true for the increase in ocean heat content . Similarly, sea level rise will continue for centuries or even millennia even if greenhouse gas emissions are brought to zero, due to the slow response of ice sheets to warming and the continued uptake of heat by the oceans, which expand when warmed. Many coastal cities will experience coastal flooding in
7504-432: The deep sea. Climate change has an impact on ocean oxygen, both in coastal areas and in the open ocean. The open ocean naturally has some areas of low oxygen, known as oxygen minimum zones . These areas are isolated from the atmospheric oxygen by sluggish ocean circulation. At the same time, oxygen is consumed when sinking organic matter from surface waters is broken down. These low oxygen ocean areas are expanding as
7616-452: The different densities of salt and fresh water. Warm air rises near the equator . Later, as it moves toward the poles, it cools again. Cool air sinks near the poles, but warms and rises again as it moves toward the equator. This produces Hadley cells , which are large-scale wind patterns, with similar effects driving a mid-latitude cell in each hemisphere. Wind patterns associated with these circulation cells drive surface currents which push
7728-732: The economy. It is however also possible that the perceived increase in HABs globally is simply due to more severe bloom impacts and better monitoring and not due to climate change. While some mobile marine species can migrate in response to climate change, others such as corals find this much more difficult. A coral reef is an underwater ecosystem characterised by reef-building corals. Reefs are formed by colonies of coral polyps held together by calcium carbonate . Coral reefs are important centres of biodiversity and vital to millions of people who rely on them for coastal protection, food and for sustaining tourism in many regions. Warm water corals are clearly in decline, with losses of 50% over
7840-622: The exchange of heat, carbon, oxygen and particles between the upper ocean and the interior. Since 1970, there has been an increase in stratification in the upper ocean due to global warming and, in some areas, salinity changes. The salinity changes are caused by evaporation in tropical waters, which results in higher salinity and density levels. Meanwhile, melting ice can cause a decrease in salinity at higher latitudes. Temperature, salinity and pressure all influence water density . As surface waters are often warmer than deep waters, they are less dense, resulting in stratification. This stratification
7952-414: The frequency and severity of mass coral bleaching events have increased sharply worldwide". Marine heatwaves have caused coral reef mass mortality. It is expected that many coral reefs will suffer irreversible changes and loss due to marine heatwaves with global temperatures increasing by more than 1.5 °C. Coral bleaching occurs when thermal stress from a warming ocean results in the expulsion of
8064-576: The frequency of very intense storms and a poleward extension of where the cyclones reach maximum intensity are among the consequences of human-induced climate change. Tropical cyclones use warm, moist air as their source of energy or fuel . As climate change is warming ocean temperatures , there is potentially more of this fuel available. Due to global warming and increased glacier melt, thermohaline circulation patterns may be altered by increasing amounts of freshwater released into oceans and, therefore, changing ocean salinity. Thermohaline circulation
8176-578: The impact of human use, such as fishing and tourism. Other environmental pressures on the reef and its ecosystem include runoff of humanmade pollutants, climate change accompanied by mass coral bleaching , dumping of dredging sludge and cyclic population outbreaks of the crown-of-thorns starfish . According to a study published in October 2012 by the Proceedings of the National Academy of Sciences ,
8288-405: The islands on the reef are found on planar reefs. Wonky holes can have localised impact on the reef, providing upwellings of fresh water, sometimes rich in nutrients contributing to eutrophication . Navigation through and around the reefs is a major challenge. More than 20 ships were recorded lost in the region between 1791 and 1850, Surveys between 1815 and 1860 by Phillip Parker King in
8400-558: The islands. 215 species of birds (including 22 species of seabirds and 32 species of shorebirds) visit the reef or nest or roost on the islands, including the white-bellied sea eagle and roseate tern . Most nesting sites are on islands in the northern and southern regions of the Great Barrier Reef, with 1.4 to 1.7 million birds using the sites to breed. The islands of the Great Barrier Reef also support 2,195 known plant species; three of these are endemic. The northern islands have 300–350 plant species which tend to be woody, whereas
8512-400: The last 30–50 years due to multiple threats from ocean warming, ocean acidification, pollution and physical damage from activities such as fishing. These pressures are expected to intensify. The warming ocean surface waters can lead to bleaching of the corals which can cause serious damage and/or coral death. The IPCC Sixth Assessment Report in 2022 found that: "Since the early 1980s,
8624-497: The life span and value of this global heritage. The plan contains all the elements for measurement and improvements, including; long-term sustainability plan, water quality improvement plan and the investment plan for the protection and preservation of The Reef until 2050. However, whereas the 2050 plan aims to incorporate protective measures such as improving water quality, reef restoration, killing of predatory starfish, it does not incorporate additional measures to address what may be
8736-458: The material to the environment and to develop a management plan to eliminate this potential hazard; however, GBRMPA does not have legislative control over how the Yabulu tailings dam is managed". The crown-of-thorns starfish preys on coral polyps. 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
8848-641: The melting ice sheets on land. Other effects on oceans include sea ice decline , reducing pH values and oxygen levels , as well as increased ocean stratification . All this can lead to changes of ocean currents , for example a weakening of the Atlantic meridional overturning circulation (AMOC). The main cause of these changes are the emissions of greenhouse gases from human activities, mainly burning of fossil fuels and deforestation . Carbon dioxide and methane are examples of greenhouse gases. The additional greenhouse effect leads to ocean warming because
8960-405: 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 accidents are a pressing concern, as several commercial shipping routes pass through the Great Barrier Reef. Although the route through the Great Barrier Reef is not easy, reef pilots consider it safer than outside
9072-596: The mission to save the Reef and all its living diversity for future generations. During the International Year of the Reef in 2018 the Turnbull government announced a AUD$ 443 million grant to the foundation. The purpose of the grant is to achieve significant, measurable improvement in the health of the Great Barrier Reef World Heritage Area in accordance with the Reef 2050 framework and underpinned by innovation, science and community engagement: Projects enabled through
9184-400: The northern parts of the reef as a result of warming ocean temperatures . In October 2016, Outside published an obituary for the reef; the article was criticised for being premature and hindering efforts to bolster the resilience of the reef. In March 2017, the journal Nature published a paper showing that huge sections of an 800-kilometre (500 mi) stretch in the northern part of
9296-460: The ocean has undergone increasing surface acidification [...]. A loss of oxygen has occurred from the surface to 1000 m [...]. It is clear that the ocean is warming as a result of climate change, and this rate of warming is increasing. The global ocean was the warmest it had ever been recorded by humans in 2022. This is determined by the ocean heat content , which exceeded the previous 2021 maximum in 2022. The steady rise in ocean temperatures
9408-409: The ocean takes up most of the additional heat in the climate system . The ocean also absorbs some of the extra carbon dioxide that is in the atmosphere . This causes the pH value of the seawater to drop . Scientists estimate that the ocean absorbs about 25% of all human-caused CO 2 emissions. The various layers of the oceans have different temperatures. For example, the water is colder towards
9520-468: The oceans due to climate change therefore acts generally to reduce ocean productivity. However, in some areas, such as previously ice covered regions, productivity may increase. This trend is already observable and is projected to continue under current projected climate change. In the Indian Ocean for example, productivity is estimated to have declined over the past sixty years due to climate warming and
9632-643: The oceans have been gradually turning green from blue as climate breakdown continues. The color change has been detected for a majority of the word's ocean surfaces and may be due to changing plankton populations caused by climate change. Climate change and the associated warming of the ocean will lead to widespread changes to the Earth's climate and weather system including increased tropical cyclone and monsoon intensities and weather extremes with some areas becoming wetter and others drier. Changing wind patterns are predicted to increase wave heights in some areas. Human-induced climate change "continues to warm
9744-466: The oceans which provide the memory of past accumulated effects". The result is a higher ocean heat content and higher sea surface temperatures. In turn, this "invigorates tropical cyclones to make them more intense, bigger, longer lasting and greatly increases their flooding rains". One example is Hurricane Harvey in 2017. Climate change affects tropical cyclones in a variety of ways: an intensification of rainfall and wind speed, an increase in
9856-404: The organic matter formed by photosynthesis in the ocean consumes oxygen and releases carbon dioxide. The sinking and bacterial decomposition of some organic matter in deep ocean water, at depths where the waters are out of contact with the atmosphere, leads to a reduction in oxygen concentrations and increase in carbon dioxide, carbonate and bicarbonate . This cycling of carbon dioxide in oceans
9968-671: The partnership between the Australian Government's Reef Trust and the foundation have six areas of focus: water quality, crown-of-thorns starfish control, reef restoration and adaptation science, traditional owner reef protection, community Reef protection and integrated monitoring and reporting. Great Barrier Reef The Great Barrier Reef is the world's largest coral reef system, composed of over 2,900 individual reefs and 900 islands stretching for over 2,300 kilometres (1,400 mi) over an area of approximately 344,400 square kilometres (133,000 sq mi). The reef
10080-414: The possible effects of El Niño weather phenomenon. The Australian Institute of Marine Science conducts annual surveys of the Great Barrier Reef's status, and the 2022 report showed the greatest recovery in 36 years. It is mainly due to the regrowth of two-thirds of the reef by the fast-growing Acropora coral, which is the dominant coral there. The Great Barrier Reef has long been known to and used by
10192-414: The production of their hard exoskeletal shell. Oceanic calcifying organism span the food chain from autotrophs to heterotrophs and include organisms such as coccolithophores , corals , foraminifera , echinoderms , crustaceans and molluscs . Although the drivers of harmful algal blooms (HABs) are poorly understood, they appear to have increased in range and frequency in coastal areas since
10304-400: The rate of the global ocean. The warming rate varies with depth. The upper ocean (above 700 m) is warming the fastest. At an ocean depth of a thousand metres the warming occurs at a rate of nearly 0.4 °C per century (data from 1981 to 2019). In deeper zones of the ocean (globally speaking), at 2000 metres depth, the warming has been around 0.1 °C per century. The warming pattern
10416-847: The reducing pH value in oceans is also a problem for coral reefs because ocean acidification reduces coralline algal biodiversity . The physiology of coralline algal calcification determines how the algae will respond to ocean acidification. Warm water corals are clearly in decline, with losses of 50% over the last 30–50 years due to multiple threats from ocean warming, ocean acidification, pollution and physical damage from activities such as fishing, and these pressures are expected to intensify. Fisheries are affected by climate change in many ways: marine aquatic ecosystems are being affected by rising ocean temperatures , ocean acidification and ocean deoxygenation , while freshwater ecosystems are being impacted by changes in water temperature, water flow, and fish habitat loss. These effects vary in
10528-509: The reef had died in the course of 2016 of high water temperatures, an event that the authors put down to the effects of global climate change. The percentage of baby corals being born on the Great Barrier Reef dropped drastically in 2018 and scientists are describing it as the early stage of a "huge natural selection event unfolding". Many of the mature breeding adults died in the bleaching events of 2016–17, leading to low coral birth rates. The types of corals that reproduced also changed, leading to
10640-466: The reef has lost more than half its coral cover since 1985, a finding reaffirmed by a 2020 study which found over half of the reef's coral cover to have been lost between 1995 and 2017, with the effects of a widespread 2020 bleaching event not yet quantified. The Great Barrier Reef has long been known to and used by the Aboriginal Australian and Torres Strait Islander peoples, and is an important part of local groups' cultures and spirituality. The reef
10752-404: The reef in the event of mechanical failure, since a ship can sit safely while being repaired. There have been over 1,600 known shipwrecks in the Great Barrier Reef region. On 3 April 2010, the bulk coal carrier Shen Neng 1 ran aground on Douglas Shoals, spilling up to four tonnes of oil into the water and causing extensive damage to the reef. The government of Queensland has
10864-536: The reef system. Thirty species of cetaceans have been recorded in the Great Barrier Reef, including the dwarf minke whale , Indo-Pacific humpback dolphin , and the humpback whale . Large populations of dugongs live there. More than 1,500 fish species live on the reef, including the clownfish , red bass , red-throat emperor, and several species of snapper and coral trout . Forty-nine species mass spawn , while eighty-four other species spawn elsewhere in their range. Seventeen species of sea snake live on
10976-457: The reef, including thirteen species of genus Halimeda , which deposit calcareous mounds up to 100 metres (110 yd) wide, creating mini-ecosystems on their surface which have been compared to rainforest cover. Climate change , pollution, crown-of-thorns starfish and fishing are the primary threats to the health of this reef system. Other threats include shipping accidents, oil spills , and tropical cyclones. Skeletal Eroding Band ,
11088-495: The reef. The majority of these spawn gametes , breeding in mass spawning events that are triggered by the rising sea temperatures of spring and summer, the lunar cycle, and the diurnal cycle. Reefs in the inner Great Barrier Reef spawn during the week after the full moon in October, while the outer reefs spawn in November and December. Its common soft corals belong to 36 genera. Five hundred species of marine algae or seaweed live on
11200-406: The root cause the problem – climate change, which is caused by greenhouse gas emissions. As such, experts doubted whether it would be enough to save the fragile environment. Another issue is that the time left to the 1.5 °C warming threshold (the temperature limit that coral reefs can still cope with ) is very limited. As part of the Reef 2050 plan, an AUD$ 443 million grant was given to
11312-649: The same amount of oxygen as cold water. As a result, oxygen from the oceans moves to the atmosphere. Increased thermal stratification may reduce the supply of oxygen from surface waters to deeper waters. This lowers the water's oxygen content even more. The ocean has already lost oxygen throughout its water column . Oxygen minimum zones are increasing in size worldwide. These changes harm marine ecosystems , and this can lead to biodiversity loss or changes in species distribution. This in turn can affect fishing and coastal tourism. For example, rising water temperatures are harming tropical coral reefs . The direct effect
11424-587: The sea turtle's population and available habitat. Bleaching events in benthic coral communities (deeper than 20 metres or 66 feet) in the Great Barrier reef are not as well documented as those at shallower depths, but recent research has shown that benthic communities are just as negatively impacted in the face of rising ocean temperatures. Five Great Barrier Reef species of large benthic corals were found bleached under elevated temperatures, affirming that benthic corals are vulnerable to thermal stress. A threat for
11536-400: The sediment until its edge was too far away for suspended sediments to inhibit coral growth. In addition, approximately 400,000 years ago there was a particularly warm Interglacial period with higher sea levels and a 4 °C (7 °F) water temperature change. The land that formed the substrate of the current Great Barrier Reef was a coastal plain formed from the eroded sediments of
11648-470: The southern islands have 200 which tend to be herbaceous; the Whitsunday region is the most diverse, supporting 1,141 species. The plants are propagated by birds. There are at least 330 species of ascidians on the reef system with the diameter of 1–10 cm (0.4–4 in). Between 300 and 500 species of bryozoans live on the reef. Four hundred coral species, both hard corals and soft corals inhabit
11760-538: The submerged hills, to form the present cays and reefs. Sea level here has not risen significantly in the last 6,000 years. The CRC Reef Research Centre estimates the age of the present, living reef structure at 6,000 to 8,000 years old. The shallow water reefs that can be seen in air-photographs and satellite images cover an area of 20,679 km , most (about 80%) of which has grown on top of limestone platforms that are relics of past (Pleistocene) phases of reef growth. The remains of an ancient barrier reef similar to
11872-411: The surface water to higher latitudes where the air is colder. This cools the water, causing it to become very dense in comparison to lower latitude waters, causing it to sink to the ocean floor, forming North Atlantic Deep Water (NADW) in the north and Antarctic Bottom Water (AABW) in the south. Driven by this sinking and the upwelling that occurs in lower latitudes, as well as the driving force of
11984-562: The symbiotic algae that resides within coral tissues. These symbiotic algae are the reason for the bright, vibrant colors of coral reefs. A 1-2°C sustained increase in seawater temperatures is sufficient for bleaching to occur, which turns corals white. If a coral is bleached for a prolonged period of time, death may result. In the Great Barrier Reef , before 1998 there were no such events. The first event happened in 1998 and after that, they began to occur more frequently. Between 2016 and 2020 there were three of them. Apart from coral bleaching,
12096-410: The water sinks more slowly than it would normally. The Atlantic Meridional Overturning Circulation (AMOC) may have weakened since the preindustrial era, according to modern observations and paleoclimate reconstructions (the AMOC is part of a global thermohaline circulation ), but there is too much uncertainty in the data to know for certain. Climate change projections assessed in 2021 indicate that
12208-456: The wider environment due to erosion of farm soil, which has a detrimental effect on the coral. Mining company Queensland Nickel discharged nitrate-laden water into the Great Barrier Reef in 2009 and 2011 – on the later occasion releasing 516 tonnes (508 long tons; 569 short tons) of waste water. The Great Barrier Reef Marine Park Authority (GBRMPA) stated "We have strongly encouraged the company to investigate options that do not entail releasing
12320-399: The winds on surface water, the ocean currents act to circulate water throughout the sea. When global warming is factored in, changes occur, particularly in areas where deep water is formed. As the oceans warm and glaciers and polar ice caps melt, more and more fresh water is released into the high latitude regions where deep water forms, lowering the density of the surface water. As a result,
12432-454: The world. As it rose, the corals could then grow higher on the newly submerged maritime margins of the hills of the coastal plain. By around 13,000 years ago the sea level was only 60 metres (200 ft) lower than the present day, and corals began to surround the hills of the coastal plain, which were, by then, continental islands . As the sea level rose further still, most of the continental islands were submerged. The corals could then overgrow
12544-445: Was Matthew Flinders who named the Great Barrier Reef, after his more detailed mapping of it in 1802. Flinders used various terms to describe the reefs comprising what we now call the Great Barrier Reef including "great reef", for one such reef, "barrier reef", for any reef preventing a sailing vessel in, or waves from, the open sea, from reaching the coast, and "Barrier Reefs", for the collection of such reefs. The Great Barrier Reef
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