Over 90 Per Cent Of The Great Barrier Reef Is Bleached, And May Never Recover

Image: Terry Hughes, ARC Centre of Excellence for Coral Reef Studies

We need to take action to stop rising sea temperatures from global warming right now if we have any hope of preventing mass coral bleaching in the future, according to a group of Australian scientists. The researchers warn it is "unlikely" the reef will ever recover from a 2016 bleaching event affecting over 90 per cent of the reef.

A detailed analysis of the Great Barrier Reef over the past two decades shows that extreme heat is the key driver of mass bleaching. As temperatures continue to rise, further bleaching events are likely, which researchers say may push the reef system beyond recovery.

Rising sea surface temperatures due to global warming have triggered major bleaching events in tropical coral reefs, and this damage can be potentially fatal to these delicate ecosystems. The most severe event in 2016, driven by record temperatures in the 2015–2016 El Nino event, bleached over 90 per cent of the corals in the Great Barrier Reef.

To understand more about the effects of climate change on reefs, Terry Hughes and colleagues assessed three major bleaching events on the Great Barrier Reef in 1998, 2002 and 2016. By analysing individual reefs, the researchers determined why some corals are more prone to bleaching than others.

They found that the distinctive geographical footprint of bleaching is primarily driven by patterns of sea temperatures; in general, unbleached reefs were located towards the southern end of the Great Barrier Reef, where waters are generally cooler.

Local management of reef fisheries and water quality offered little to no protection against extreme heat, but the researchers note that these efforts may help these ecosystems to recover from bleaching events.

However, it is unlikely that the Great Barrier Reef will ever fully recover from the severe bleaching that occurred in 2016, and the security of coral reefs requires urgent and rapid global action to curb future warming, researchers conclude.

[Nature]

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