MELBOURNE/SYDNEY, Aug 4 (Reuters) – Two-thirds of Australia’s Great Barrier Reef showed the largest amount of coral reef in 36 years, but the reefs are often prone to mass bleaching, an official long-term monitoring program said on Thursday. .
The recovery of the central and northern parts of the UNESCO World Heritage-listed reef contrasts with the southern part, where the crown starfish outbreak has led to coral loss, according to the Australian Institute of Marine Science (AIMS). In its annual report.
“We see that the Great Barrier Reef is still a resilient system. It still maintains the ability to recover from disturbances,” AIMS monitoring program leader Mike Emsley told Reuters.
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“But what is worrying is that the frequency of these disturbance events is increasing, especially mass coral bleaching events,” he said.
The report comes as UNESCO considers whether to list the Great Barrier Reef as “in danger” following a visit by UNESCO experts in March. A World Heritage Committee meeting was scheduled to take place in Russia in June, where the fate of the rocks was on the agenda, but was postponed.
A variety of reef fish swim above a stunted coral colony as it grows on the Great Barrier Reef off the coast of Cairns, Australia, on October 25, 2019. REUTERS/Lucas Jackson
As a key measure of reef health, AIMS defines high value as more than 30% hard coral based on long-term surveys of reefs.
In the northern region, average hard coral cover grew from 13% in 2017 to 36% in 2022, while hard coral cover in the central region increased from 12% to 33% in 2019 – the highest levels since the agency began monitoring reefs in 1985 for both regions.
However, the southern region, which generally has more hard coral than the other two regions, dropped to 34% in 2022, down from 38% a year earlier.
The fourth mass bleaching in seven years and the first recovery comes during a La Niña event, which typically brings cooler temperatures. Although extensive, the agency said bleaching in 2020 and 2022 was not as damaging as in 2016 and 2017.
Downstream, cover growth is driven by Acropora corals, which are vulnerable to wave damage, thermal stress and crown starfish, AIMS said.
“We’re really in uncharted waters when it comes to the effects of bleaching and what that means moving forward. But to this day, it’s still an amazing place,” Emsley said.
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Reporting by Sonali Paul in Melbourne and James Redmayne in Sydney; Editing by Stephen Coates
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