Great Barrier Reef ocean temperatures hit 400-year record: study August 8, 2024

Water temperatures along Australia's spectacular Great Barrier Reef have been the warmest in 400 years over the past decade, according to a major study (DAVID GRAY)

By AFP -Agence France Presse

Great Barrier Reef ocean temperatures hit 400-year record: study

Laura CHUNG

Over the past decade, water temperatures along Australia's famous Great Barrier Reef have been the warmest in 400 years, according to a major study on Thursday.

Ocean temperatures around the spectacular coral system have increased annually since 1960, but were particularly warmer during recent mass coral bleaching events, according to a study published in the scientific journal Nature.

According to the report, the warmer waters are probably due to human-induced climate change.

Co-author Helen McGregor said she was "extremely concerned" about the reef, describing the temperature rises as "unprecedented".

"These are corals that have been living for 400 years and are the hottest temperatures they are experiencing. These are the Redwood trees of the reef," she told AFP.

Often dubbed the world's largest living structure, the Great Barrier Reef is a 2,300-kilometer-long expanse, home to an impressive array of biodiversity that includes more than 600 types of coral and 1,625 species of fish.

However, repeated mass bleaching events, when extreme heat depletes the corals' nutrients and color, threaten the reef's fragile ecosystem.

Coral bleaching occurs when the water temperature rises by more than one degree Celsius (1.8 degrees Fahrenheit).

- The changes are occurring very quickly

The Australian researchers examined sea surface temperatures in the Coral Sea, a 2,000-kilometer stretch of ocean that runs along the northeast coast and includes the Great Barrier Reef.

The scientists used coral skeleton samples to reconstruct sea surface temperatures from 1618 to 1995, as well as more recent data.

They found that temperatures before 1900 were relatively stable, but that the sea had warmed by 0.12C (0.2F) on average from 1960 to the present.

These temperatures were even higher during the last five mass bleaching events in 2016, 2017, 2020, 2022, and 2024, according to the report.

McGregor said that although corals could recover, rising high temperatures and repeated bleaching events were damaging this ability.

"These changes - from what we're seeing so far - seem to be happening too fast for corals to adapt to them, which threatens the reef as we know it," said McGregor, a climate researcher at the University of Wollongong.

This year's bleaching event left 81% of the reef with extreme or high levels of damage - one of the most severe and widespread ever recorded, according to the latest government figures.

Scientists will take a few more months to determine how much of the reef is beyond recovery.

- 'Existentially threatened' - Richard Leck

Richard Leck, oceans director at World Wide Fund Australia, said the future of the reef is "increasingly vulnerable".

"At the moment, we can see that the reef is resilient. It has recovered from previous coral bleaching events, but at some point that elastic band will break," he told AFP.

"Coral reefs, as an ecosystem, are the first ecosystem on the planet to be existentially threatened by climate change."

"I think we have to hope that the world is not going to stand by and let this happen. But it's a split second to midnight," he said.

Governments around the world are stepping up efforts to help reduce greenhouse gases or invest in reef adaptation and mitigation efforts.

Australia has invested around Aus$5 billion (US$3.2 billion) to improve water quality, reduce the effects of climate change and protect endangered species.

But Australia, one of the world's largest exporters of gas and coal, has only recently set targets to become carbon neutral.

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