The Great Barrier Reef in Australia has deteriorated to a “critical point” with its future outlook downgraded from “poor” to “very poor” due to global warming and local pollution, a major government report has concluded.

Immediate national and international action is required to improve the reef’s prospects, with the global climate crisis representing the greatest long-term threat to the natural wonder, according to the five-year Great Barrier Reef Outlook Report 2019.

The degradation of the world’s largest living structure has resulted in significant habitat loss for turtles, fish and sea birds. Back-to-back major coral bleaching events in 2016 and 2017 resulted in the death of around half of the entire 133,360-square-mile structure due to marine heatwaves exacerbated by rising global temperatures.

“The current rate of global warming will not allow the maintenance of a healthy reef for future generations,” the report said, stating “the window of opportunity to improve the reef’s long-term future is now”.

“Significant global action to address climate change is critical to slowing the deterioration of the reef’s ecosystem and heritage values and supporting recovery,” the authors said. “Such actions will complement and greatly increase the effectiveness of local management actions in the reef and its catchment.”

Coral reefs: Trying to combat climate change damage Show all 25 1 /25 Coral reefs: Trying to combat climate change damage Coral reefs: Trying to combat climate change damage Masked Butterflyfish (Chaetodon semilarvatus) swimming over a bommie reef in the Egyptian Red Sea marine reserve of Ras Mohamed, off the southern tip of the Sinai peninsula AFP/Getty Coral reefs: Trying to combat climate change damage Rising sea temperatures cause corals to bleach (go white) and die Getty/iStock Coral reefs: Trying to combat climate change damage A giant clam is seen nestled among coral reefs at the Obhor coast, 30 kms north of the Red Sea city of Jeddah AFP/Gett Coral reefs: Trying to combat climate change damage Coral reef in seychelles that has degraded After the reef has died they break up and become rubble. On this reef there is some regrowth of young corals so there is hope for recovery Getty Coral reefs: Trying to combat climate change damage Coral gardening A rabbitfish in a net H Goehlich Coral reefs: Trying to combat climate change damage A school of fish and a sea can in a healthy coral reef off the coast of Isla Mujeres, Mexico Getty/Lumix Coral reefs: Trying to combat climate change damage Sky views of great barrier reef in Australia Getty/iStock Coral reefs: Trying to combat climate change damage A fish swims among coral reefs at the Obhor coast AFP/Getty Coral reefs: Trying to combat climate change damage Researchers from the Interuniversity Institute for Marine Sciences in the southern Israeli resort city Eilat monitor coral growth while scuba diving in the Red Sea AFP/Getty Coral reefs: Trying to combat climate change damage Coral gardening A rope nursery Nature Seychelles Coral reefs: Trying to combat climate change damage Fish swimming off the coast of Egypt's Red Sea resort of Hurghada. The rebounding tourism sector is worrisome for the fragile marine ecosystem AFP/Getty Coral reefs: Trying to combat climate change damage Coral gardening A parrotfish on the reef C Reveret Coral reefs: Trying to combat climate change damage Gorgonian sea fan on a a coral reef in the Egyptian Red Sea marine reserve of Ras Mohamed AFP/Getty Coral reefs: Trying to combat climate change damage A diver swims during a Great Barrier Reef experience on Lady Elliot Island, Australia Getty/Tourism Queensland Coral reefs: Trying to combat climate change damage Jessica Bellsworthy, a PhD student conducting research on the coral reefs of the Gulf of Eilat, holds a coral in an aquarium at the Interuniversity Institute for Marine Sciences in Eilat AFP/Getty Coral reefs: Trying to combat climate change damage Coral reefs in the water off the Obhor coast, 30 kms north of the Red Sea city of Jeddah in 2008 AFP/Getty Coral reefs: Trying to combat climate change damage A diver photographs golden anthias (Pseudanthias aurulentus) on a coral reef in the Egyptian Red Sea marine reserve of Ras Mohamed AFP/Getty Coral reefs: Trying to combat climate change damage FUNAFUTI, TUVALU - AUGUST 15: From the air the ocean (L) and the logoon (R) and separated by a thin stip of land on August 15, 2018 in Funafuti, Tuvalu. The small South Pacific island nation of Tuvalu is striving to mitigate the effects of climate change. Rising sea levels of 5mm per year since 1993, well above the global average, are damaging vital crops and causing flooding in the low lying nation at high tides. Sea water rises through the coral atoll on the mainland of Funafuti and inundates taro plantations, floods either side of the airport runway and affects peoples homes. The nation of 8 inhabited islands with an average elevation of only 2m above sea level is focusing on projects to help it and its people have a future. Four of the outer islands are 97% solar energy dependent and the Tuvalu Government is working to achieve 100% renewable energy from wind and solar by 2025. Tuvalu's 11,000 inhabitants see the effects of climate change in their daily life. (Photo by Fiona Goodall/Getty Images for Lumix) Fiona Goodall Getty/Lumix Coral reefs: Trying to combat climate change damage A photo taken on April 4, 2019 shows fish swimming off the coast of Egypt's Red Sea resort of Hurghada. - In dazzling turquoise waters off Egypt's Red Sea coast, scuba divers swim among delicate pink jellyfish and admire coral -- but the rebounding tourism sector is worrisome for the fragile marine ecosystem. (Photo by Mohamed el-Shahed / AFP) (Photo credit should read MOHAMED EL-SHAHED/AFP/Getty Images) MOHAMED EL-SHAHED AFP/Getty Coral reefs: Trying to combat climate change damage Coral gardening A damselfish Sarah Frias-Torres Coral reefs: Trying to combat climate change damage Divers swim past a coral reef in the Egyptian Red Sea marine reserve AFP/Getty Coral reefs: Trying to combat climate change damage A puffer fish hovering above coral in the Egyptian Red Sea marine reserve AFP/Getty Coral reefs: Trying to combat climate change damage Researchers from the Interuniversity Institute for Marine Sciences in the southern Israeli resort city Eilat monitor coral growth while scuba diving on June 12, 2017 in the Red Sea off Eilat. Global warming has in recent years caused colourful coral reefs to bleach and die around the world -- but not in the Gulf of Eilat, or Aqaba, part of the northern Red Sea. At the Interuniversity Institute for Marine Sciences in southern Israeli resort city Eilat, dozens of aquariums have been lined up in rows just off the Red Sea shore containing samples of local corals AFP/Getty Coral reefs: Trying to combat climate change damage This photo taken on April 21, 2017 shows an aerial shot of part of mischief reef in the disputed Spratly islands on April 21, 2017. Philippine Defence Secretary Delfin Lorenzana flew to a disputed South China Sea island on April 21, brushing off a challenge by the Chinese military while asserting Manila's territorial claim to the strategic region. / AFP PHOTO / TED ALJIBE (Photo credit should read TED ALJIBE/AFP/Getty Images) TED ALJIBE AFP/Getty Coral reefs: Trying to combat climate change damage fish swimming off the coast of Egypt's Red Sea resort of Hurghada AFP/Getty

The report comes as Australia’s government has published figures indicating its greenhouse gas emissions have hit a seven-year high.

Other major threats to the reef include coastal development, farming pollution and illegal fishing.

The report is the third of its kind and monitors the continuing damage and degradation to the Unesco World Heritage site.

The report reflects the expanding area of coral killed or damaged by the severe bleaching events in recent years.

The Great Barrier Reef Marine Park Authority chairman Ian Poiner said: “The accumulation of impacts, through time and over an increasing area, is reducing its ability to recover from disturbances, with implications for reef-dependent communities and industries.

“The overall outlook for the Great Barrier Reef is very poor.”

The authority’s chief scientist David Wachenfeld said in a statement: “Gradual sea temperature increase and extremes, such as marine heatwaves, are the most immediate threats to the reef as a whole and pose the highest risk.

“Global action on climate change is critical.”

The United Nations World Heritage Committee expressed concern about bleaching in 2017 and the latest report could lead to the reef being reclassified by Unesco next year as “in danger”.

Australian environment minister Sussan Ley said she was not surprised by the downgrade in the reef’s condition given the damage done by recent cyclones and bleaching events over successive years.

She said her government is “building resilience in this important global reef” and is keeping its Paris commitment to reduce Australia’s greenhouse gas emissions by 26 per cent to 28 per cent below 2005 levels by 2030.

“I want to make the point that it’s the best managed reef in the world,” she added.

“There are those who will not be happy unless we declare the reef dead in the name of climate change, just as there are those who want to claim that nothing out of the ordinary is taking place,” she wrote in an opinion piece for the Sydney Morning Herald titled “The Great Barrier Reef is not dead... long live the reef”.