It is one of the great natural wonders: the Great Barrier Reef off the coast of Australia. According to a new study, the sea water there has never been as warm as it is now. Researchers say there is a threat of a permanent mass extinction of the corals.
The water temperatures around the Great Barrier Reef in Australia have reached a new high: according to an Australian research team, never in the past 400 years has it been as warm there as this year.
Warming due to human influences?
The warming can be attributed to human influences, the team writes in the journal Nature. The researchers led by Benjamin Henley from the University of Melbourne in Australia reconstructed the sea surface temperatures from 1618 to 1995 using coral skeletons from the reef and compared them with the recorded sea surface temperature data from 1900 to 2024.
Barely Temperature fluctuations until 1960
Before 1900, water temperatures were relatively stable. The study shows that there was a steady increase from 1960 to 2024: an average warming of 0.12 degrees Celsius per decade was measured in the period from January to March. Nevertheless, as the authors note, there are also uncertainties in the reconstructed temperature data from the period before 1900.
Some of the chemical compositions in the corals used to model temperatures may have been influenced by other variables such as salinity, but additional coral core sampling from the region could reduce these uncertainties.
Five mass bleachings in eight years
As water temperatures rise due to global warming, the risk of mass bleaching and coral deaths in Australia's natural wonders is also increasing. Mass coral bleaching was first observed in 1980; in recent years they have increased in frequency. In March this year, the fifth mass bleaching event in eight years was confirmed on the Great Barrier Reef, which is home to a diverse ecological network.
“The downfall of a great natural wonder”
The researchers show that in the years of the last mass bleaching events (2016, 2017, 2020, 2022 and 2024), the average months of January to March were significantly warmer than in any year of reconstruction before 1900. “Without rapid, coordinated and ambitious global action to combat climate change, we are likely to witness the demise of one of Earth's great natural wonders,” the team writes.
The scientists point out that 70 to 90 percent of corals worldwide are likely to be lost – even if global warming is kept below the Paris Agreement's target of 1.5 degrees Celsius. In addition, future coral reefs would likely have a different community structure with a lower diversity of coral species.
