Coral cover on two-thirds of Australia’s Great Barrier Reef has reached its highest level since records began 36 years ago, according to marine scientists monitoring the ecosystem.

But coral remains highly vulnerable to mass bleaching events, which are occurring with increasing frequency as human activity warms the oceans, the Australian Institute of Marine Science (AIMS) said in its annual report.

Recovery in the central and northern parts of the UNESCO-listed reef has not extended to the southern region, which has lost its coral cover amid an outbreak of crowned starfish. thorns.

The Great Barrier Reef remains a “resilient system” that “always maintains this ability to recover from disturbances,” said AIMS monitoring program manager Mike Emslie.

“But what is worrying is that the frequency of these disturbance events is increasing, especially the massive coral bleaching events,” he added.

Earlier this year, the first mass bleaching occurred during a La Niña year, a natural climate cycle that typically brings cooler temperatures that allow coral to recover. It was the fourth mass laundering event in seven years.

Dr Emslie said climate change was causing increasingly frequent and longer-lasting marine heat waves.

“The increasing frequency of warming ocean temperatures and the magnitude of massive bleaching events highlight the critical threat that climate change poses to all reefs, especially as outbreaks of crowned sea stars thorns and tropical cyclones also occur,” he said.

He warned: “Future disruptions can reverse the observed recovery in a short time.”

AIMS chief executive Dr Paul Hardisty said the increasing frequency of such events is “uncharted territory” for the reef.

“In our 36 years of monitoring the state of the Great Barrier Reef, we have not seen bleaching events this close together,” he said.

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Great Barrier Reef bleaching fears

The report comes as UNESCO debates whether to classify the Great Barrier Reef as ‘endangered’, following a visit by the UN body in March.

The issue was to be discussed at a meeting of the World Heritage Committee in Russia in June, which was later postponed.

In a key measure of reef health, AIMS defines hard coral cover of more than 30% as a high value, based on its long-term sustainability.
reef surveys.

In the northern region, average hard coral cover increased to 36% in 2022, while in the central region hard coral cover increased to 33% – the highest levels recorded for both regions since the institute began monitoring the reef in 1985.

But in the southern region, which generally has higher hard coral cover than the other two regions, coverage has fallen to 34% in 2022 from 38% a year earlier.

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