The study, published Friday in the peer-reviewed journal Current Biology, found that only two percent of the vast ecosystem has escaped since the first major coral bleaching in 1998 – the warmest year ever – a record that has since been broken time and time again. while global warming has accelerated.
The frequency, intensity and extent of heat waves in the water, which cause coral bleaching, are increasing, according to Terry Hughes, professor and director of the Center for Coral Reef Studies at James Cook University.
– Five rounds of mass bleaching since 1998 have transformed the Great Barrier Reef into a collection of reefs with very different histories. It ranges from the two percent who have completely escaped bleaching, to the 80 percent who have now been severely bleached at least once since 2016, he says.
MASS DEATH OF CORALS: Climate change has led to the mass death of corals. Australia is now setting aside three billion kroner for the work of preserving the Great Barrier Reef. Video: NTB Scanpix view more
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Three times in recent years
The bleaching occurs when healthy corals are exposed to stress factors such as increased sea temperature, acidification and pollution. The corals get rid of the algae they normally live in symbiosis with, lose their color and can be seriously damaged.
The Great Barrier Reef has been hit by three episodes of mass bleaching in connection with heat waves in recent years, in 2016, 2017 and 2020, respectively. This has made many foxes struggle to survive.
Australian researchers said in July that corals had shown some signs of improvement since the last bleaching, but acknowledged that the long-term prospects for the 2,300-kilometer ecosystem were “very poor”.
The reef is also exposed to damage from cyclones and starfish that eat the corals. Both factors are deteriorating in line with climate change.
Researchers have found that corals that have previously been exposed to heat waves are more resistant to heat, but the study’s co-author Sean Connolly, who comes from the Smithsonian Tropical Research Institute, warns that more frequent and severe bleaching can make them more vulnerable.
Corals need time to recover before a new round of heat stress, so that they can have children that spread, settle down and rebuild the depleted parts of the reef. Action to slow down climate change is vital, he says.
The study is being published while leaders from around the world have gathered for the COP26 climate conference in Glasgow, in an attempt to come up with solutions to the climate crisis.
