A recent study analysing centuries-old coral samples has highlighted the severe threat climate change poses to the Great Barrier Reef.

Australian researchers found that temperatures around the reef over the past decade have been the highest recorded in 400 years. This extreme heat has already triggered five mass bleaching events in just nine years.

Published in the journal Nature, the study warns that rising temperatures, driven by climate change, now present an “existential threat” to this natural wonder.

“The science tells us that the Great Barrier Reef is in danger – and we should be guided by the science,” Prof Helen McGregor, from the University of Wollongong, said.

The evidence comes directly from the coral itself.

Marine scientists examined core samples drilled from the skeletons of the coral. These samples contain chemical markers that reveal how the reef’s environment has evolved over time.

Corals, which are animals, can live for centuries, recording environmental changes in their skeletons.

By re-analysing data from thousands of these coral cores and cross-referencing them with historical sea temperature records from the UK’s Hadley Centre, researchers confirmed that the last decade’s temperatures were the warmest in four centuries.

“The recent events in the Great Barrier Reef are extraordinary,” said lead researcher Dr Benjamin Henley, who carried out the study whilst working at Wollongong University.

“Unfortunately, this is terrible news for the reef.”

“There is still a glimmer of hope though,” he added. “If we can come together and restrict global warming, then there’s a glimmer of hope for this reef, and others around the world, to survive in their current state.”

Corals rely on a symbiotic relationship with a type of algae that lives within them, providing food and vibrant colour.

However, when sea temperatures rise too high, corals expel this algae, leading to bleaching and turning the corals white. If temperatures remain elevated, the corals can die, devastating the ecosystem they support.

“It’s not a pretty sight,” said Dr Henley. “Eventually [other] algae grows on the surface of the white coral, turning it brown.

“While bleached coral can recover, if the heat does not relent, it doesn’t have the chance to,” he explained.

“I’m a little reluctant to say things are doomed,” said Prof McGregor.

“Reefs have survived a lot of change over geological time. So I guess the question comes down to – what kind of reef do we end up with?

“It won’t be like what we have now.”

The Great Barrier Reef, currently a UNESCO World Heritage site, is now at significant risk.

Scientists hope this research will persuade UNESCO to classify the reef as “endangered,” highlighting the urgent need for action to protect this critical marine ecosystem.

Prof McGregor said this “would send a huge signal to the world about how grave the problem is”.

“We know what we need to do,” she added. “We have international agreements in place [to limit global temperature rise].

“I think we just need to put the politics aside and get on with it.”

 

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