Death of reef looms: top scientists

Climate change will certainly kill off large swathes of the Great Barrier Reef, top Australian scientists say.

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What’s really at stake now is how much of the reef, if any, can survive beyond the turn of the century, they say.

Climate and reef experts from the ARC Centre of Excellence for Climate System Science have analysed the mass coral bleaching event currently playing out along almost the entire length of the reef.

They say climate change was directly responsible for a one-degree Celsius rise in sea temperatures in March, which killed and sickened coral, especially in the most pristine sections of the reef north of Cairns.

Within the next 20 years, such mass bleaching events will be normal and occurring about once every two years, the scientists warn.

And that will spell death for large stretches of the reef because corals won’t get anything like the 15-year break they need to fully recover from severe bleaching.

“We are going to lose a lot of the Great Barrier Reef over the next couple of decades. There is no doubt about that,” Professor Ove Hoegh-Guldberg, who co-authored the analysis, told AAP on Friday.

“And if we don’t stabilise sea temperatures, and other things like ocean acidification, our reef will disappear.”

Lead author Dr Andrew King said that by the mid-2030s, the sea temperatures that did so much damage in March would be considered average.

“After beyond that, this would be a relatively cold March. That’s really quite a scary thing,” he told AAP.

“Even if we reduce our emissions now, we’re still going to see quite a lot of warming over the next few decades. It’d only be from the mid-21st century onward that we’d really see any substantial benefits from reducing emissions now.”

Prof Hoegh-Guldberg leads the University of Queensland’s Global Change Institute and is running cutting edge experiments to simulate the effects of climate change on the reef, in compressed time frames.

He said some of his scientific colleagues branded him alarmist back in 1999 when he released a research paper predicting the loss of coral-dominated reefs by 2040.

“Now that looks conservative and I’m in a position where I’m standing here saying this is happening faster than we originally thought.”

Prof Hoegh-Guldberg believes there’s still time to stabilise key climate change effects, including warmer and more acidic oceans, but the window for action is closing.

“The steps we take today will determine whether or not coral reefs will re-flourish in the mid to late century – or not,” he said.

He said last year’s Paris agreement – that saw almost 200 countries including Australia commit to limiting global warming to well below two degrees Celsius, and 1.5 degrees in the long term – was an important first step.

But he struggles to comprehend how the federal and Queensland governments can reconcile their professed concerns about the reef and climate change with their recent approvals for Adani to build Australia’s largest coal mine in the Galilee basin.

“That sends a really strange message internationally and perpetuates the idea that Australia doesn’t get it,” Prof Hoegh-Guldberg says.

“… 80 per cent of known fossil fuels have to stay in the ground for the reef to have any chance of surviving this century.”