Great Barrier Reef suffers third mass bleaching event in five years

After record heatwaves in Australia, which led to the disastrous bushfires there earlier in the year, the Great Barrier Reef has now suffered widespread coral bleaching for the third time since 2016.

Dead reef
A photo of one of the northern sections of the Great Barrier Reef which was killed off in 2016

Last week the Great Barrier Reef Marine Park Authority announced to the world that it had collected enough data to conclude that the reef system had suffered its third mass bleaching event in the last five years. It follows successive and widespread bleaching events in 2016 and 2017 where over half of the shallow water reefs in the system were either temporarily or permanently bleached. The announcement came as little surprise after sea surface temperatures in some places were 5oF higher than the seasonal average during February, as a result of the record heatwaves that had left much of the continent burning for months on end over the summer. The only real surprise is that the announcement came before surveys by James Cook University researchers had even been fully completed. So what does the latest set-back mean for the future of the Great Barrier Reef and what, if anything, can be done to save it?

Surveying the reefs

The decision to officially announce this year as a mass bleaching event was made after collecting data from over 800 reefs covering more than 344,000 km2, which was done by the Centre of Excellence for Coral Reef Studies at James Cook University. Based on initial dive surveys and aerial observations they were confident enough to declare this year as a mass bleaching event before their work was even completed. That work is now finished and until the data has been properly analysed over the next few weeks (or possibly longer due to COVID 19 disturbance) we won’t know for sure the exact facts and figures for the extent of the damage. However the researchers have managed to highlight key areas for concern.

Aerial surveys
Aerial surveys are one of the main methods of surveying coral bleaching on the Great Barrier Reef

One of the big conclusions the researchers were able to make was that large parts of the southern end of the system, which managed to escape severe bleaching in 2016 and 2017, had been seriously affected for the first time. Fortunately some of northern reefs, which are very important to the tourism industry, only sustained moderate bleaching and are likely to recover. However some of these corals will be bleaching for the third time in five years and we have no way of knowing how this affects them in the long run. Although most northern reefs escaped sever bleaching there is also some concern that severe bleaching occurred on coastal and mid-shelf reefs in the far north, where most corals were previously believed to be heat tolerant.

Future outlook

It will take several months to fully analyse what has happened and exactly which areas and species of corals will be most affected, but what we do know is that widespread bleaching has occurred again and it is likely to be the worst event yet. Unfortunately this is nothing new, worldwide coral reefs are bleaching and dying at an alarming rate and their chances of surviving the next century are starting to look a lot bleaker. The most recent UN Intergovernmental Panel on Climate Change report suggests that a majority of tropical coral reefs will disappear by 2100, even if heating was limited to 1.5oC and would be “at very high risk” at 1.2oC. The most worrying thing about this latest event is that we may already be seeing the start of this, as these bleaching events are becoming too regular for reefs to successfully recover before the next one hits.

Shipping lane
A man-made shipping channel is a visible reminder of how we are destroying coral reefs

What can be done?

In response to the confirmation of the latest bleaching event, the Australian government has announced an additional $1.9 billion to help protect the Great Barrier Reef. This is an addition to the $2.7 billion already pledged as part of the Reef 2050 Plan set up in conjunction with Queensland authorities. The aim is to use this money to help reduce other stressors on the reef which can increase the likelihood of coral bleaching. This includes improving water quality by preventing dredging of ports, stopping agricultural run-off and reducing the amount of plastic entering the reef. As well as removing coral damaging species like the crown-of-thorns seastar and preventing damaging practices like destructive fishing. On top of all this researchers are also working hard to identify resilient species of coral and novel ways of aiding reefs in their recovery, which could help provide a lifeline even if reefs suffer major damage.

crown of thornes
The crown of thorns seastar is one of the few problems facing the Great Barrier Reef that can be realistically prevented in the short term

Now or never

So despite the devastating news of another mass bleaching event there is still a glimmer of hope for the Great Barrier Reef. However none of the handwork by researchers and conservation groups, or the billions of dollars in government funding, can have a chance of succeeding if the root cause is not addressed. Climate change remains, according to the Marine Park Authority, ‘the main threat’ to the Great Barrier Reef. However without significant and immediate systematic change across the entire world, climate change will not be reduced in time to save it. Coral reefs, especially the Great Barrier Reef, are important bio-indicators of the climate breakdown. We need to acknowledge these bleaching events and listen to what the corals are trying to tell us before its too late. It shouldn’t have to take the collapse of one of nature’s largest and most spectacular ecosystems for us to start taking the situation seriously.

Bleached coral
A field of ghostly white bleached corals

It’s not over till it’s over, but it’s getting increasing close to being over.


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