Scientists report that the Great Barrier Reef will never recover from the impact of warm waters

SYDNEY (Reuters) - Parts of Australia's Great Barrier Reef will never recover from the impact of unseasonably warm waters, scientists said on Thursday, as more of the World Heritage Site comes under renewed threat from a recent spike in sea temperatures.

Warm seas around the reef killed some two-thirds of a 700 kilometer (496.4 miles) stretch of coral last year after warm water caused the coral to expel living algae, triggering it to calcify and turn white, a process known as bleaching. That was the worst die-off of coral ever recorded at the reef.

Even the areas that survived will not recover to full health, scientists from ARC Centre of Excellence for Integrated Coral Reef Studies said in a report, as unseasonable hot water becomes more frequent causing more incidents of bleaching.

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A man snorkels in an area called the "Coral Gardens" near Lady Elliot Island, on the Great Barrier Reef, northeast of Bundaberg town in Queensland, Australia, June 11, 2015. REUTERS/David Gray/File Photo TPX IMAGES OF THE DAY
A tourist snorkels above coral in the lagoon located on Lady Elliot Island on the Great Barrier Reef, 80 kilometers north-east from the town of Bundaberg in Queensland, Australia, June 9, 2015. REUTERS/David Gray/File Photo
Oliver Lanyon, senior ranger in the Great Barrier Reef region for the Queenlsand Parks and Wildlife Service, takes photographs and notes during an inspection of the reef's condition in an area called the "Coral Gardens" located at Lady Elliot Island and 80 kilometers north-east from the town of Bundaberg in Queensland, Australia, June 11, 2015. Picture taken June 11, 2015. REUTERS/David Gray/File photo
A large piece of coral can be seen in the lagoon on Lady Elliot Island, on the Great Barrier Reef, northeast from Bundaberg town in Queensland, Australia, June 9, 2015. REUTERS/David Gray/File photo
Peter Gash, owner and manager of the Lady Elliot Island Eco Resort, snorkels with Oliver Lanyon and Lewis Marshall, Senior Rangers in the Great Barrier Reef region for the Queenlsand Parks and Wildlife Service, during an inspection of the reef's condition in an area called the 'Coral Gardens' located at Lady Elliot Island located north-east from the town of Bundaberg in Queensland, Australia, June 10, 2015. REUTERS/David Gray/File photo
Oliver Lanyon, Senior Ranger in the Great Barrier Reef region for the Queenlsand Parks and Wildlife Service, takes photographs and notes during an inspection of the reef's condition in an area called the 'Coral Gardens' located at Lady Elliot Island and 80 kilometers north-east from the town of Bundaberg in Queensland, Australia, June 11, 2015. REUTERS/David Gray/File photo
Tourists snorkel near a turtle as it looks for food amongst the coral in the lagoon at Lady Elliot Island north-east of the town of Bundaberg in Queensland, Australia, June 9, 2015. The lagoon, which is occupied by turtles during high tide, is only accessible for snorkelling during this time. UNESCO World Heritage delegates recently snorkelled on Australia?s Great Barrier Reef, thousands of coral reefs, which stretch over 2,000 km off the northeast coast. Surrounded by manta rays, dolphins and reef sharks, their mission was to check the health of the world's largest living ecosystem, which brings in billions of dollars a year in tourism. Some coral has been badly damaged and animal species, including dugong and large green turtles, are threatened. UNESCO will say on Wednesday whether it will place the reef on a list of endangered World Heritage sites, a move the Australian government wants to avoid at all costs, having lobbied hard overseas. Earlier this year, UNESCO said the reef's outlook was "poor". REUTERS/David Gray PICTURE 9 OF 23 FOR WIDER IMAGE STORY "GREAT BARRIER REEF AT RISK" SEARCH "GRAY REEF" FOR ALL PICTURES
Marine activist Suzanne Kavanagh swims above coral suffering from bleaching on Australia's Great Barrier Reef. The world's largest coral structure is experiencing its worst ever case of bleaching, which scientists fear could threaten its fragile marine environment. Picture taken 25APR98. REUTERS/Handout
Peter Gash, owner and manager of the Lady Elliot Island Eco Resort, prepares to snorkel during an inspection of the reef's condition in an area called the 'Coral Gardens' located at Lady Elliot Island, north-east of the town of Bundaberg in Queensland, Australia, June 11, 2015. Gash snorkels every morning before he attends to managing duties on the island. UNESCO World Heritage delegates recently snorkelled on Australia?s Great Barrier Reef, thousands of coral reefs, which stretch over 2,000 km off the northeast coast. Surrounded by manta rays, dolphins and reef sharks, their mission was to check the health of the world's largest living ecosystem, which brings in billions of dollars a year in tourism. Some coral has been badly damaged and animal species, including dugong and large green turtles, are threatened. UNESCO will say on Wednesday whether it will place the reef on a list of endangered World Heritage sites, a move the Australian government wants to avoid at all costs, having lobbied hard overseas. Earlier this year, UNESCO said the reef's outlook was "poor". REUTERS/David Gray PICTURE 14 OF 23 FOR WIDER IMAGE STORY "GREAT BARRIER REEF AT RISK" SEARCH "GRAY REEF" FOR ALL PICTURES
Natalie Friere, a diving and snorkelling guide, swims through a natural archway in an area called the 'Coral Gardens' located at Lady Elliot Island and 80 kilometers north-east from the town of Bundaberg in Queensland, Australia, June 10, 2015. UNESCO World Heritage delegates recently snorkeled on Australia's Great Barrier Reef, thousands of coral reefs, which stretch over 2,000 km off the northeast coast. Surrounded by manta rays, dolphins and reef sharks, their mission was to check the health of the world's largest living ecosystem, which brings in billions of dollars a year in tourism. Some coral has been badly damaged and animal species, including dugong and large green turtles, are threatened. UNESCO will say on Wednesday whether it will place the reef on a list of endangered World Heritage sites, a move the Australian government wants to avoid at all costs, having lobbied hard overseas. Earlier this year, UNESCO said the reef's outlook was "poor". Picture taken June 10, 2015. REUTERS/David Gray
Huts that form part of the Lady Elliot Island Eco Resort can be seen where a turtle digs for food amongst the coral in the island's lagoon, located 80 kilometers north-east from the town of Bundaberg in Queensland, Australia, June 9, 2015. UNESCO World Heritage delegates recently snorkeled on Australia's Great Barrier Reef, thousands of coral reefs, which stretch over 2,000 km off the northeast coast. Surrounded by manta rays, dolphins and reef sharks, their mission was to check the health of the world's largest living ecosystem, which brings in billions of dollars a year in tourism. Some coral has been badly damaged and animal species, including dugong and large green turtles, are threatened. UNESCO will say on Wednesday whether it will place the reef on a list of endangered World Heritage sites, a move the Australian government wants to avoid at all costs, having lobbied hard overseas. Earlier this year, UNESCO said the reef's outlook was "poor". Picture taken June 9, 2015. REUTERS/David Gray
Dried coral lies on a beach as the sun sets on Lady Elliot Island located 80 kilometers north-east from the town of Bundaberg in Queensland, Australia, June 10, 2015. UNESCO World Heritage delegates recently snorkeled on Australia's Great Barrier Reef, thousands of coral reefs, which stretch over 2,000 km off the northeast coast. Surrounded by manta rays, dolphins and reef sharks, their mission was to check the health of the world's largest living ecosystem, which brings in billions of dollars a year in tourism. Some coral has been badly damaged and animal species, including dugong and large green turtles, are threatened. UNESCO will say on Wednesday whether it will place the reef on a list of endangered World Heritage sites, a move the Australian government wants to avoid at all costs, having lobbied hard overseas. Earlier this year, UNESCO said the reef's outlook was "poor". Picture taken June 10, 2015. REUTERS/David Gray
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"Given time, coral can recover from bleaching but the problem comes when you get repeated events. With less time between them, capacity for the coral reef community to recover diminishes rapidly," Janice Lough, senior principal research scientist at the Australian Institute of Marine Science, told Reuters.

The conclusion is a major blow for Australia's tourism industry, with the reef attracting A$5.2 billion ($3.9 billion) in spending each year, a 2013 Deloitte Access Economics report estimated.

Repeated damage to the Great Barrier Reef may also see UNESCO's World Heritage Committee reconsider its decision in 2015 not to put the Great Barrier Reef on its "in danger" list.

Academics said the findings demonstrate the urgency in tackling climate change, which climate scientists argue occurs when increased carbon dioxide in the atmosphere is trapped by heat radiating from earth.

The outlook for the Great Barrier Reef has further darkened with evidence of an unprecedented second consecutive bleaching event this year, researchers at James Cook University said.

Unseasonably warm waters threatens to cause bleaching of the central region of the Great Barrier Reef, which avoided the large-scale damage from the bleaching in 2016.

"We're hoping that the next two to three weeks will cool off quickly, and this year's bleaching won't be anything like last year," said Terry Hughes, director of ARC Centre of Excellence for Coral Reef Studies.

(Reporting by Colin Packham; Editing by Randy Fabi)

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