May 30, 2023

Central and northern areas of Australia’s Great Barrier Reef have the highest coral cover seen in 36 years, showing the fragile UNESCO World Heritage site could still recover from decades of damage, a monitoring group reported on Thursday. Coral cover in the southern region of the reef has declined, however, and the reef is vulnerable to increasingly common disturbances such as mass bleaching events, the team said.

There was an increase in average hard coral cover in the northern region of the reef to 36% in 2022 from 27% in 2021 and an increase in the central region to 33% in 2022 from 27% in 2021, according to the Australian Institute of Marine Sciences (AIMS) states in its annual summary report.

Despite this, “a third of the increase in coral cover we recorded in the south in 2020/21 was lost last year due to ongoing thorn star outbreaks,” said Dr. Paul Hardisty, CEO of AIMS, in a statement. . “This shows how vulnerable the reef is to ongoing acute and severe disturbances that occur more frequently and last longer.”

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AIMS has been monitoring the Great Barrier Reef since 1986. It said an increase in the frequency of mass bleaching events – when coral, in response to stressful conditions such as heat, loses its pigments and symbiotic algae, turns white and eventually dies – was “uncharted territory.”

“In 36 years of monitoring the state of the Great Barrier Reef we have not seen bleaching events this close,” Hardisty said. “Each summer the reef is at risk of temperature stress, bleaching and potentially mortality, and our understanding of how the ecosystem responds to this is still developing.”

Dr. Mike Emslie, also from the AIMS monitoring programme, said most of the coral growth in the northern and central parts of the reef was due to fast-growing but fragile Acropora corals and could therefore be quickly reversed.

“These corals are particularly vulnerable to wave damage, such as that created by strong winds and tropical cyclones,” Emsley said. “The increasing frequency of ocean warming and the extent of mass bleaching events underscore the critical threat climate change poses to all reefs, particularly while starbursts and tropical cyclones also occur. Future perturbation may reverse the observed recovery in short time”.

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