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The study of dinosaur bones has provided four centuries of scientific information coral The Australian Great Barrier has such a long history that the conclusion is clear: the largest bleaching events have coincided with peak temperatures in the southern hemisphere summer caused by climate change.
According to Nature magazine, 2024, 2022, 2020, 2017 and 2016 were five black summers, when large areas of the largest coral reefs on Earth turned a dead white.
Specifically, the years 2024 and 2017 are the most disruptive for the ecosystem.
“Ocean temperatures during these bleaching events were unprecedented in the past four centuries“One of the authors, Helen McGregor, a researcher at the University of Wollongong in Australia, emphasized at a press conference.
The study is based on the reconstruction of 400 years of sea surface temperatures in the Great Barrier Reef using geochemical data obtained from the analysis of rocky coral skeletons collected in the Great Barrier Reef by scientists from the universities of Wollongong, Melbourne and Queensland (Australia), Tulane University and Columbia University (USA).
Comparison with UNESCO decision
The authors certainly link this finding to climate change, showing that political and institutional decisions are not always consistent with existing scientific knowledge.
Just two weeks ago, at a meeting in India, UNESCO decided to stop declaring the Great Barrier Reef an “at risk” ecosystem, citing efforts by the Australian administration to halt its deterioration.
“The Great Barrier Reef is definitely in danger”, retorted a researcher from the University of Melbourne. Benjamin Henry, At the same press conference.
Although the current study preceded that decision, it was accepted by the journal on 4 June and adopted by the decision on 25 July, and its results confirm existing indications that devastating bleaching has been recorded on the Great Barrier Reef as a result of increasing warming with every temperature record ever recorded.
Data from the study concluded that sea temperatures on the reef during January to March (austral summer) reached their highest levels in 400 years in 2024, 2017 and 2020, with 2024 being the warmest year on record.
How does whitening happen?
The whitening effect is coral It occurs when stress, in this case caused by high temperatures, causes the coral to expel the algae that live in its tissues and give it its color.
If extreme warming of the oceans does not abate over a long enough period of time, corals can become “bare,” or bleached, and eventually become sick and, in many cases, die, allowing the corals to recover and once again attract protective algae to inhabit them.
Protecting marine biodiversity
“When I looked at the 2024 numbers, I had to triple-check my calculations: They were off the charts, I couldn’t believe it,” Henry noted.
Emergency intervention
“Without urgent intervention, the iconic Great Barrier Reef is at risk of annual bleaching due to high ocean temperatures, which would put its ecological integrity and value at risk. The corals that have survived for hundreds of years and provided the data for this study are seriously threatened,” McGregor added.
UNESCO decided not to consider the Great Barrier Reef an ecosystem at risk (it has been since 2021) and detailed a long list of actions taken by the Australian government and Queensland to protect the Great Barrier Reef, including large-scale investments in protection and not approving new fossil fuel projects.
But are the efforts of a single government enough to prevent the barrier from being breached? Scientists say no, because climate change is a global challenge, so its impact also depends on what the rest of the world does.
“When all the evidence is put together, what really strikes me is that the impacts on the reefs in the coming years are inevitable, and therefore this decision is misunderstood.” (from UNESCO), McGregor said.
Zanzibar discovers clever way to save corals
“We already have the key solutions to stop climate change; what we need is to radically accelerate their implementation in all countries,” the researchers insisted. “Every degree of temperature increase we manage to avoid counts. We cannot lose hope.”
Whether or not this is done depends not only on the survival of Australia’s Great Barrier Reef, “one of the most spectacular natural wonders on Earth,” but also on other coral reefs around the world that face the same problems described in this study. (I)
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