Two-thirds of the Great Barrier Reef has now been devastated by severe coral bleaching, with damage occurring further south this year, Queensland scientists say.

Two of the world's leading experts on coral bleaching in the Great Barrier Reef said aerial surveys they conducted this year along the reef's entire length showed an accelerated rate of bleaching in the central section.

The ARC Centre of Excellence for Coral Reef Studies undertook the aerial surveys in both 2016 and 2017.

In 2016, bleaching was most severe in the northern third of the Reef, while one year on the middle third has experienced the most intense coral bleaching.

Dr James Kerry from James Cook University in north Queensland, who was one of the scientists involved in the surveys, said the latest damage had occurred in a stretch from Cooktown to Townsville.

"Last year we saw severe bleaching in the northern third, and this year we have seen severe bleaching on the Great Barrier Reef from about Cooktown down to Townsville, so we are calling that the central third," he said.

"So about two-thirds of the reef now in the past 12 months have had a fairly serious bleaching event."

He said there was little doubt that bleaching was being caused by record-breaking temperatures driven by global warming.

"It is fair to say that this is extremely concerning for the long-term health of the reef," he said.

"It is facing a number of stresses, but I think the outside stress is coral bleaching, and we have now seen two major events in two years, which we have never seen before - that is unprecedented."

He said it was the fourth time the Great Barrier Reef had bleached severely.

"In 1998, 2002, 2016, and now in 2017 - bleached corals are not necessarily dead corals, but in the severe central region we anticipate high levels of coral loss," he said.

Coupled with the 2017 mass bleaching event, Tropical Cyclone Debbie struck a section of the Great Barrier Reef in March.

Scientists said the intense, slow-moving system was likely to have caused varying levels of damage along a path up to 100 kilometres in width.

Researchers said any cooling effects related to the cyclone were likely to be negligible in relation to the damage it caused, which unfortunately struck a section of the reef that had largely escaped the worst of the bleaching. </s> An unprecedented amount of coral bleaching for two consecutive years has severely damaged two-thirds of Australia’s Great Barrier Reef, aerial surveys have shown.

Scientists at the ARC Centre of Excellence for Coral Reef Studies recorded severe coral bleaching for the second time in 12 months after surveying the Great Barrier Reef’s entire 2,300km-long (1,500) miles ecosystem.

“This is the fourth time the Great Barrier Reef has bleached severely – in 1998, 2002, 2016, and now in 2017. Bleached corals are not necessarily dead corals, but in the severe central region we anticipate high levels of coral loss,” said Dr. James Kerry of James Cook University. 



“It takes at least a decade for a full recovery of even the fastest growing corals, so mass bleaching events 12 months apart offers zero prospect of recovery for reefs that were damaged in 2016.”

READ MORE: Australia’s Great Barrier Reef on brink of collapse - scientists

The study found that while the northern third of the reef experienced the most severe bleaching last year, the middle third experienced the most intense coral bleaching this year, resulting in catastrophic damage of the natural wonder of the world.

“The combined impact of this back-to-back bleaching stretches for 1,500km (900 miles), leaving only the southern third unscathed,” said Prof. Terry Hughes who undertook the aerial surveys in both 2016 and 2017.

“The bleaching is caused by record-breaking temperatures, driven by global warming. This year, 2017, we are seeing mass bleaching, even without the assistance of El Niño conditions.”

The 2017 survey of the reef covered more than 8,000km (5,000 miles) and nearly 800 coral reefs that matched the 2016 aerial surveys. Last year, Climate Central found bleaching has hit 93 percent of the reef, with 80 percent enduring severe bleaching.

READ MORE: Viral spiral: 'Obituary' for embattled Great Barrier Reef slammed for hyperbole

The mass bleaching, coupled with the destructive Tropical Cyclone Debbie in March, has struck a previously undamaged section of the reef.

“Clearly the reef is struggling with multiple impacts,” explains Prof. Hughes. “Without a doubt the most pressing of these is global warming. As temperatures continue to rise the corals will experience more and more of these events: 1°C of warming so far has already caused four events in the past 19 years.”

“Ultimately, we need to cut carbon emissions, and the window to do so is rapidly closing.” </s> Great Barrier Reef: Severe coral bleaching hits two-thirds of reef, aerial surveys show

Updated

Two-thirds of the Great Barrier Reef has now been devastated by severe coral bleaching, with the most intense damage occurring further south this year, Queensland scientists say.

Key Points: Of the 2,300km of reef, 1,500km is bleached

Middle third section has most intense bleaching, southern third unscathed

Caused from record-breaking temperature

The fastest growing coral will take a decade to recover

An aerial survey of the reef's 2,300-kilometre length by the Australian Research Council's Centre of Excellence for Coral Reef Studies showed 1,500km had been bleached.

Compared to its 2016 survey, where the northern third was worst off, this year the central third — Cooktown down to Townsville — recorded the most intense bleaching.

The southern third is unscathed.

The council's director, Terry Hughes, who undertook the aerial survey both years, said record-breaking temperatures, driven by global warming, has led to the bleaching.

He said it would take the fastest growing coral in the 1,500km stretch about a decade to recover.

"The 10-year recovery hasn't even started yet, because of the back-to-back bleaching," he said.

"There has been no gap in bleaching between 2016 and 2017, we need gaps between bleaching to get a full recover."

Dr James Kerry from James Cook University in north Queensland said it was the fourth time the Great Barrier Reef had bleached severely.

The survey estimated that a 1 degree Celsius rise in temperatures had caused four bleaching events in the past 19 years.

"It is fair to say that this is extremely concerning for the long-term health of the reef," he said.

"It is facing a number of stresses, but I think the outside stress is coral bleaching, and we have now seen two major events in two years, which we have never seen before - that is unprecedented.

"In 1998, 2002, 2016, and now in 2017 - bleached corals are not necessarily dead corals, but in the severe central region we anticipate high levels of coral loss."

Coupled with the 2017 mass bleaching event, Tropical Cyclone Debbie struck a section of the Great Barrier Reef in March.

Scientists said the intense, slow-moving system was likely to have caused varying levels of damage along a path up to 100 kilometres in width.

Researchers said any cooling effects related to the cyclone were likely to be negligible in relation to the damage it caused, which unfortunately struck a section of the reef that had largely escaped the worst of the bleaching.

Sorry, this video has expired Video: Footage shows areas of the Great Barrier Reef in the Whitsundays devastated by Cyclone Debbie (ABC News)

Search for unspoiled reefs

Mark Read, the Great Barrier Reef Marine Park Authority's manager of species conservation, said it the authority was working with tourism operators to find reefs that had not been affected by bleaching.

"To see whether or not there are areas we need to put additional resources towards protecting," he said.

"Sure there's some areas that have been hit incredibly hard by the bleaching and the cyclone, but it's still a magnificently large place with some areas that have been largely unaffected and that are still in very good condition."

Topics: great-barrier-reef, oceans-and-reefs, climate-change, environment, science-and-technology, academic-research, earth-sciences, townsville-4810, james-cook-university-townsville-4811, qld, australia, cairns-4870, mackay-4740

First posted </s> Back-to-back bleaching is killing huge tracts of the Great Barrier Reef, with almost none of the coral affected in 2016 expected to recover.

Recent aerial surveys by the Australian Research Council's Centre of Excellence for Coral Reef Studies have revealed only the southern third of the reef is unscathed from the bleaching events.

Researcher Terry Hughes said mass bleaching happened in 2017 even without the assistance of El Nino, which normally brings warmer sea surface temperatures.

'The bleaching is caused by record-breaking temperatures driven by global warming,' Professor Hughes said.

'Ultimately, we need to cut carbon emissions, and the window to do so is rapidly closing.'

Warmer water temperatures cause coral to expel their algae, turning them bright fluorescent colours and eventually bone white.

Marine biologist James Kerry said bleached corals were not necessarily dead but it was anticipated high levels of coral would be lost in the central region of the reef, which experienced the most intense bleaching this year.

'It takes at least a decade for a full recovery of even the fastest growing corals, so mass bleaching events 12 months apart offers zero prospect of recovery for reefs that were damaged in 2016,' Dr Kelly said.

Tropical Cyclone Debbie also destroyed parts of the reef around the Whitsundays, a popular tourist destination that had largely escaped the worst of the bleaching so far.

While cyclones normally cause the water temperature to drop, Prof Hughes said any cooling effects were likely to be negligible in relation to the damage caused by the slow-moving Category 4 system.

'Clearly the reef is struggling with multiple impacts,' he said.

The Great Barrier Reef is known to have experienced four bleaching events in 1998, 2002, 2016 and 2017. </s> Scientists in Australia have recorded "severe" coral bleaching across large parts of the Great Barrier Reef for the second time in 12 months.

In a news release on Monday, James Cook University (JCU) in Australia said that aerial surveys had shown that the middle third of the reef had seen the most intense bleaching, while in 2016 bleaching had hit the northern third the hardest.

"The combined impact of this back-to-back bleaching stretches for 1,500 km (900 miles), leaving only the southern third unscathed," Terry Hughes, director of the Australian Research Council's (ARC) Centre of Excellence for Coral Reef Studies, said in a statement. The Centre is headquartered at JCU.

 

 Hughes, who was involved with the aerial surveys in 2016 and 2017, went on to add that the bleaching had been caused "by record-breaking temperatures driven by global warming. This year, 2017, we are seeing mass bleaching, even without the assistance of El Niño conditions."

Bleaching takes place when "abnormal" conditions – such as increased sea temperatures – result in coral getting rid of very small photosynthetic algae, according to the ARC and JCU.

When this happens, the corals "bleach" and turn white. While they can recover if the sea temperature falls again, they can die if it doesn't.

"This is the fourth time the Great Barrier Reef has bleached severely – in 1998, 2002, 2016, and now in 2017," James Kerry, who was also involved in the aerial surveys, said.

 

 "Bleached corals are not necessarily dead corals, but in the severe central region we anticipate high levels of coral loss," Kerry added. "It takes at least a decade for a full recovery of even the fastest growing corals, so mass bleaching events 12 months apart offers zero prospect of recovery for reefs that were damaged in 2016."

As well as the mass bleaching, a corridor of the Great Barrier Reef had to contend with the impact of Tropical Cyclone Debbie towards the end of March. This, JCU said, "was likely to have caused varying levels of damage along a path up to 100 km in width."

Hughes said that the reef was struggling with multiple impacts. "Without a doubt the most pressing of these is global warming," he added.

 

 "As temperatures continue to rise the corals will experience more and more of these events: 1°C of warming so far has already caused four events in the past 19 years." </s> In just nine months, bleaching caused by warmer water has killed around 67% of the coral in a previously pristine part of the reef, one of the natural wonders of the world.

"We've seen three bleaching events (in the reef) and each time it can be explained by where the warm water was," the report's author, ARC Center of Excellent for Coral Reef Studies Director Terry Hughes, told CNN.

"In the north, the summer temperatures got up to two degrees above the normal maximum and that caused severe bleaching," he said.

Extensive aerial surveys and teams of divers were used to map the bleaching, which covered a length of 700 kilometers.

Hughes said it could take up to 15 years for coral to grow back to previous levels. Read: Can our oceans be saved from environmental ruin? Threats to the reef have become so severe that in recent years UNESCO has suggested it could be placed on list of World Heritage sites "in danger." A spokesman for Australia's Environment Minister Josh Frydenberg said a report on the status of the Great Barrier Reef to UNESCO was due by Friday, local time. A decision on whether or not the reef will be declared "in danger" is expected within the next year, the spokesman added. Two major coral bleaching events in the Great Barrier Reef took place in 1998 and 2002, but Hughes said this year's had been the most devastating. "It's quite sobering, we've now seen three of these events, each one was more severe than the last and these have occurred with less than one degree of global warming," he said. "Two degrees of global warming will mean these events are more severe." Dramatic coral bleaching, seen in Australia's Great Barrier Reef from March 2016. Some of the bleaching of reefs in the northern section has been described as "extreme." Bleaching occurs when the marine algae that live inside corals die. Of the reefs surveyed in the northern third of the Great Barrier Reef, 81% are characterized as "severely bleached." "At some reefs, the final death toll is likely to exceed 90%," Andrew Baird, of the ARC Center of Excellence for Coral Reef Studies, says. A photo taken on September 22, 2014, shows bleached coral on the Reef, a key Australian tourist attraction. Tourism on the Great Barrier Reef generates an annual income of A$5 billion ($3.9 billion) and employs nearly 70,000 people. Of the reefs surveyed in the northern third of the Reef, 81% are characterized as "severely bleached." Driven by ocean temperatures that have been 1-2 degrees Celsius (1.8-3.6° F) above average, the bleaching event has left large sections of coral drained of all color and fighting for survival. The Reef has suffered two mass bleaching events, in 1998 and 2002, but the extent of the bleaching in these years was less severe than in 2016. Although the coral is expected to regrow, Hughes said a fourth or fifth major bleaching event in the next 15 years could damage the reef even further. "It's too unpredictable for anyone to be sure when the next event will occur," he said. RELATED: The Great Barrier Reef is not actually dead Researcher Grace Frank completing bleaching surveys in November along the less-damaged southern Great Barrier Reef. Northern reef used to be 'pristine' While the northern parts of the reef were damaged severely by the bleaching event, others survived almost entirely intact. The Great Barrier Reef's southern third only suffered about 1% bleaching on average, the report said, mostly due to the arrival of Cyclone Winston in February this year. "It brought temperatures in the bottom half of the reef down and saved it from what would have been a reef-wide bleaching event," Hughes said. – 

Pictured: A solitary bear sits on the edge of one of the Barter Islands, Alaska. There is no snow, when at this time of year, there should be," wrote photographer Patty Waymire. Via National Geographic The "Climate Change -- In Focus" exhibition shows the effects of climate change.Pictured: A solitary bear sits on the edge of one of the Barter Islands, Alaska. There is no snow, when at this time of year, there should be," wrote photographer Patty Waymire. Via National Geographic Your Shot – The exhibition shows the best 100 photographs from a global competition.

"On a recent trip to Indonesia we were saddened to see the huge number of bleached anemones. We expected to see some coral bleaching, but we were surprised by how many anemones were also becoming victims to rising ocean temperatures," wrote photographer Diana Paboojian. Via National Geographic Your Shot Emperors at the edge in Antarctica – Photo: Kira Morris. A group of emperor penguins faces a crack in the sea ice, near McMurdo Station, Antarctica. Via National Geographic Your Shot – Photo: Jetje Japhet, South Africa. "These animals have found the secret stash of the orange farmer who dumps the oranges that have fallen from his trees at least 7km away from the orchards to control the breeding of fruit fly. It is the end of a long, dry, winter exacerbated by global warming which makes the winters longer and drier and the summers hotter with less rain in an already dry climate. These animals then behave totally out of character with baboons and warthog still feeding after dark," wrote Japhet. Via National Geographic Your Shot – A seal lies near among massive cracks in the sea ice near Ross Island, Antarctica. Photo: Kira Morris, Antarctica. Via National Geographic Your Shot – Photo: Probal Rashid. "A flood-affected woman on a raft approaches a boat, searching a dry place to shelter herself in Islampur, Jamalpur, Bangladesh. Bangladesh is one of the countries most vulnerable to the effects of climate change," wrote Rashid. Via National Geographic Your Shot – Photo: Vladimir Melnik, Russia: "I was in expedition exploring Franz Josef Land archipelago. There was a polar station where people brought dogs as guards against polar bears. The summer is difficult time for bears. In recent years warming in Arctic resulted in loss of sea ice which is critically important for bears as they can hunt only from ice. The bears which stay on the islands doomed to meager ration and go to human settlements," wrote Melnik. Via National Geographic Your Shot – Photo: Ujjal Das, India: "The pic was taken in Puruliya District of West Bengal. This is a drought-prone area and in summertime the whole district becomes dry creating water problem." Via National Geographic Your Shot – Matuf Ikhsan, Indonesia: "In Gers, France, an irrigation reservoir supplies water to a monocultural field. Here the economy revolves mainly around culinary tourism." – Riddhima Singh Bhati, India: "This part of Rajasthan is badly affected by intense heat waves and dryness because of decreased precipitation. The anticipated rise in temperature due to climate change poses formidable challenge to development of livestock in India." – Photo by Hira Ali, Pakistan: "The picture shows a flooding in the mountainous area of Chitral, in the north of Pakistan. There are many glaciers high in the mountain. Due to climate change, for the past two years there has been a lot of flooding and destruction." – Photo: Leung Ka Wa, China: "A visible aspect of climate change is the turbidity in the air. It can be caused by particulates caused by combustion products. The turbid air decreases visibility so it is harder to see the stars in urban areas." – Photo: Tom Schifanella, USA: "Since 2000, Icelandic glaciers have lost 12% of their size, in less than 15 years. Pictured here, Icelandic guide Hanna Pétursdóttir admires an ice cave inside the Svínafellsjökull Glacier, which she notes is rapidly expanding due to the effects of global warming," wrote Schifanella. Via National Geographic Your Shot – Photo: Stuart Chape, Samoa: "This aerial view of the Chong Kneas floating village on Tonle Sap lake, Cambodia, demonstrates just how threatened the great lake is from changing rainfall patterns and rising temperatures." Via National Geographic Your Shot – Photo: Long Yat Chau, Hong Kong: "Air pollution, particularly in the form of waste gas from generating stations, is a serious problem in Hong Kong." – Photo: Ryan Lai, Hong Kong: "Piles of solid waste lie behind a perfectly-framed photograph of spectacular scenery." – Photo: Felicia Hou, USA: "It is almost as if Mother Nature is sending us a warning that if we do not stop destroying the planet now, there may not be one to destroy in the future." – Photo: Vadim Balakin, Russia: "These polar bear remains have been discovered at one of the islands of Northern Svalbard, Norway. While it is not certain whether the polar bear died from starvation or old age, the good condition of its teeth indicate that it is most likely from starvation," wrote Balakin. Via National Geographic Your Shot Hughes said the northern sections had previously been among the most pristine in the entire Great Barrier Reef, remaining untouched while the southern regions saw their coral drop by half in the past 30 years. "It's hard to get to, so it's the part where there are more sharks, more crocodiles, more turtles, more coral. Unfortunately the 67 per cent loss we've detected means that pristine northern part is now in a worse condition than the lower part," he said. </s> In just nine months, bleaching caused by warmer water has killed around 67% of the coral in a previously pristine part of the reef, one of the natural wonders of the world.

"We've seen three bleaching events (in the reef) and each time it can be explained by where the warm water was," the report's author, ARC Center of Excellent for Coral Reef Studies Director Terry Hughes, told CNN.

"In the north, the summer temperatures got up to two degrees above the normal maximum and that caused severe bleaching," he said.

Extensive aerial surveys and teams of divers were used to map the bleaching, which covered a length of 700 kilometers.

Hughes said it could take up to 15 years for coral to grow back to previous levels. Threats to the reef have become so severe that in recent years UNESCO has suggested it could be placed on list of World Heritage sites "in danger." A spokesman for Australia's Environment Minister Josh Frydenberg said a report on the status of the Great Barrier Reef to UNESCO was due by Friday, local time. A decision on whether or not the reef will be declared "in danger" is expected within the next year, the spokesman added. Two major coral bleaching events in the Great Barrier Reef took place in 1998 and 2002, but Hughes said this year's had been the most devastating. "It's quite sobering, we've now seen three of these events, each one was more severe than the last and these have occurred with less than one degree of global warming," he said. "Two degrees of global warming will mean these events are more severe." Dramatic coral bleaching, seen in Australia's Great Barrier Reef from March 2016. Some of the bleaching of reefs in the northern section has been described as "extreme." Bleaching occurs when the marine algae that live inside corals die. Of the reefs surveyed in the northern third of the Great Barrier Reef, 81% are characterized as "severely bleached." "At some reefs, the final death toll is likely to exceed 90%," Andrew Baird, of the ARC Center of Excellence for Coral Reef Studies, says. A photo taken on September 22, 2014, shows bleached coral on the Reef, a key Australian tourist attraction. Tourism on the Great Barrier Reef generates an annual income of A$5 billion ($3.9 billion) and employs nearly 70,000 people. Of the reefs surveyed in the northern third of the Reef, 81% are characterized as "severely bleached." Driven by ocean temperatures that have been 1-2 degrees Celsius (1.8-3.6° F) above average, the bleaching event has left large sections of coral drained of all color and fighting for survival. The Reef has suffered two mass bleaching events, in 1998 and 2002, but the extent of the bleaching in these years was less severe than in 2016. Although the coral is expected to regrow, Hughes said a fourth or fifth major bleaching event in the next 15 years could damage the reef even further. "It's too unpredictable for anyone to be sure when the next event will occur," he said. RELATED: The Great Barrier Reef is not actually dead Researcher Grace Frank completing bleaching surveys in November along the less-damaged southern Great Barrier Reef. Northern reef used to be 'pristine' While the northern parts of the reef were damaged severely by the bleaching event, others survived almost entirely intact. The Great Barrier Reef's southern third only suffered about 1% bleaching on average, the report said, mostly due to the arrival of Cyclone Winston in February this year. "It brought temperatures in the bottom half of the reef down and saved it from what would have been a reef-wide bleaching event," Hughes said. Hughes said the northern sections had previously been among the most pristine in the entire Great Barrier Reef, remaining untouched while the southern regions saw their coral drop by half in the past 30 years. "It's hard to get to, so it's the part where there are more sharks, more crocodiles, more turtles, more coral. Unfortunately the 67 per cent loss we've detected means that pristine northern part is now in a worse condition than the lower part," he said. </s> The Great Barrier Reef is dying, and there might be zero hope of recovery.

Australia’s Great Barrier Reef is approaching “terminal stage” after two years of consecutive mass coral bleaching, according to scientists who just got back from an aerial survey of the World Heritage site, as reported by Express UK.

Researchers, who recently surveyed the 2,250 km long Great Barrier Reef, said that unusually warm waters caused severe coral bleaching on two-thirds of the reef. The bleaching data on the world’s largest reef was collated after researchers surveyed about 800 individual coral reefs.

A previous survey conducted last year confirmed that two-thirds of corals in the northern section of the Great Barrier Reef are dying due to warm waters caused by global warming.

This year, researchers from ARC Center of Excellence for Coral Reef Studies at James Cook University in Queensland announced that the central part of the reef has been severely damaged following another year of warm climate.

“We’ve had a back-to-back bleaching for the first time,” said Professor Terry Hughes, who directs the center.

“So we redid our aerial surveys again, which was a bit tough. I was hoping to never have to do it again,” Hughes tweeted. “I showed the results of aerial surveys of #bleaching on the #GreatBarrierReef to my students, And then we wept.”

Coral mass bleaching happens when warmer-than-usual waters cause the coral to expel living algae, changing its color to white. Coral bleaching, usually, is no cause for worry since mildly bleached coral can recover itself once temperature drops. Global warming, however, has been keeping the waters warm longer than usual, thus not giving the Great Barrier Reef enough time to recover itself.

“Bleached corals are not necessarily dead corals, but in the severe central region we anticipate high levels of coral loss,” James Kerry, senior research officer at the ARC Center of Excellence for Coral Reef Studies, explains.

This is the fourth time the Great Barrier Reef has suffered mass coral bleaching since 1998.

As previously reported by The Sun, category four Cyclone Debbie, which left a trail of disaster in northeast Australia and New Zealand, could have damaged the Great Barrier Ref even more. The amount of damage the storm left in its wake is still unknown at this point, but scientists said it could range from minor to severe.

Queensland Parks and Wildlife Service and the Great Barrier Reef Marine Park Authority conducted a study last week to determine the extent of the damage and have found destroyed coral at famous snorkeling spots.

“The feedback that’s coming back is the more sheltered areas have come out a bit better, but they all seem to have suffered some form of damage,” Association of Marine Park Tourism Operators’ Brendon Robinson said.

Professor Hughes said that the Great Barrier Reef is not considered dead yet, but it’s going there if no concrete action plan is made to salvage the site.

“Clearly the reef is struggling with multiple impacts. Without a doubt the most pressing of these is global warming,” he said.

Hughes reminded Australia to take decisive action in saving the reef since tourists are spending £3.15 billion each year to pay the tourist attraction a visit. </s> Two-thirds of Australia's Great Barrier reef has been devastated by back-to-back years of "severe" coral bleaching, aerial surveys have found, raising fears that the natural wonder may not fully recover.

While mass bleaching has been recorded on the Great Barrier Reef before, researchers say two events have never occurred in such close proximity.

Coral bleaching occurs when abnormal environmental conditions — such as heightened sea temperatures — push corals to expel tiny photosynthetic algae causing them to turn white.

The damage was recorded by the Australian Research Council's Centre of Excellence for Coral Reef Studies, which carried out separate studies over the past two years.

Its 2016 survey found the top third of the reef had experienced the most intense bleaching. But research completed last week recorded more damage along the 1,400 mile long reef's middle third.

"The combined impact of this back-to-back bleaching stretches for [900 miles], leaving only the southern third unscathed," ARC director Terry Hughes said Monday.

He said bleaching can be caused by weather patterns such as El Nino as well as higher temperatures driven by global warming.

While the 2016 bleaching was part of a "global event associated with the 2015-2016 El Nino," this year has more to do with a "very mild winter and [summer] heatwaves" on the east coast of Australia, Hughes said.

Situated on Australia's north east coast, the Great Barrier Reef was given World Heritage status in 1981.

It is described by the Australian government as one of the world's natural wonders.

Severe bleaching events have been recorded previously on the Great Barrier Reef in 1998 and 2002.

Bleached corals can recover if the temperature drops and algae can recolonize. But experts warn this process can take up to 10 years.

James Kerry, who was part of the aerial survey team, said: "It takes at least a decade for a full recovery of even the fastest growing corals, so mass bleaching events 12 months apart offers zero prospect of recovery for reefs that were damaged in 2016."

The researchers also said a section of the reef untouched by the bleaching was damaged by Tropical Cyclone Debbie last month.

But while Hughes said the reef was likely struggling with multiple problems, the most pressing was global warming.

"As temperatures continue to rise the corals will experience more and more of these events. One degree Celsius of warming so far has already caused four events in the past 19 years," Hughes said. "Ultimately, we need to cut carbon emissions, and the window to do so is rapidly closing."

Jon Brodie, a water quality expert who was not involved in the research, told the Guardian he believes the reef is now in a "terminal stage."

"Last year was bad enough, this year is a disaster year," he told the newspaper.
The Australian Research Council reports that two thirds of the Great Barrier Reef have suffered from severe coral bleaching, denoting a second consecutive year of severe bleaching.