Coral bleaching could happen every two years: report

Coral bleached by rising sea temperatures on the Great Barrier Reef. AAP Image/University of QLD/Ove Hoegh-Guldberg

The Great Barrier Reef could be hit with catastrophic bleaching every two years by 2034, under current greenhouse gas pollution levels, according to the latest report from the Climate Council.

The ‘Lethal Consequences: Climate Change Impacts on the Great Barrier Reef’ report shows the future survival of coral reefs around the world, including the Great Barrier Reef, depends on how deeply and swiftly greenhouse gas pollution levels are slashed over the coming years and decades.

Climate Councillor and ecologist Professor Lesley Hughes said accelerating climate change has driven a 54 per cent increase in the number of marine heatwave days each year (between 1925-1954 and 1987-2016), placing global reefs at serious risk.

‘Intensifying marine heatwaves around the world are now occurring more often, lasting longer and are more intense than ever before,’ she said.

‘Now, coral reefs around the world are also in the firing line, with rising ocean temperatures and more frequent marine heatwaves placing them at increasing risk.’

Professor Hughes said the unprecedented bleaching events on the Great Barrier Reef in 2016 and 2017 resulted in mass coral mortality, with the 2016 bleaching event at least 175 times more likely to occur due to intensifying climate change.

‘Unless drastic action is taken, extreme coral bleaching will be the new normal by the 2030s. We will see extreme ocean temperatures, similar to those that led to these bleaching events possibly occurring every two years, which will effectively sign the death certificate for the world’s largest natural living wonder that is the Great Barrier Reef,’ she said.

Report key findings include:

  • Unprecedented bleaching events on the Great Barrier Reef in 2016 and 2017 have resulted in mass coral mortality.
  • Rising sea surface temperatures over the past century have resulted in more frequent and prolonged global marine heatwaves.
  • By 2034, the extreme ocean temperatures that led to the 2016 and 2017 bleaching events may occur every two years. Such a short period between bleaching events is not sustainable as the development of coral assemblages takes at least a decade.
  • Between 1925–1954 and 1987–2016 the global average frequency of marine heatwaves increased by 34% and the global average duration increased by 17%.
  • Global sea surface temperatures have increased by 0.2°C from 1992 to 2010, increasing the odds of more frequent and prolonged marine heatwaves.
  • The return period for global bleaching events has decreased from 27 years in the 1980s to only 5.9 years now.
  • In the future, regional-scale bleaching can be expected to occur in hot summers in both El Niño and La Niña years.

Climate Council Acting CEO Dr Martin Rice said the future of coral reefs around the world depends on nations including Australia doing their part to effectively tackle climate change.

‘Limiting global temperature rise above pre-industrial levels to no more than 1.5°C is critical for the survival of reefs worldwide, along with economies and tourism operators who rely upon them,’ he said.

‘We cannot place our heads in the sand as marine heatwaves intensify due to the burning of fossil fuels such as coal, oil and gas around the world.

‘This report shows that the Great Barrier Reef may never fully recover or return to its pre-bleaching state, which should serve as a serious warning signal for governments around the world to act now.

‘We all have a part to play in cutting greenhouse gas pollution levels in order to protect these natural wonders. The only thing standing in the way is political will,’ he said.


One response to “Coral bleaching could happen every two years: report”

  1. Lyn Dickinson says:

    One important step Australia should take in fulfilling its global responsibility is to stop the proposed Adani coal mine in its tracks and adopt a no new coal mine policy. This will give investors the certainty they need so that we can achieve 100% renewables and zero greenhouse gas emissions ASAP. The Turnbull Government’s current 26% emissions reduction target by 2030 falls far short of what is needed to get our global temperatures down to 1.5 degrees C. Even though Labor’s policy is zero net emissions by 2050, how do they expect to achieve it if they continue to support new coal mines? The Greens are the only party which is standing up against Adani with an energy policy which does not include coal.

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