Great Barrier Reef Has Highest Coral Cover in 36 Years, But Global Heating Could Jeopardize Recovery

Reef scene with fish and branching corals
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The Australian Institute of Marine Science (AIMS) has recorded the highest amount of coral cover in the northern and central portions of the Great Barrier Reef since it started monitoring 36 years ago, reported Phys.org. 

However, the AIMS long-term monitoring report warned that the same corals that had quickly increased coral cover were the ones that were the most vulnerable to storms, crown-of-thorns starfish (COTS) and especially the marine heatwaves exacerbated by global heating, The Guardian reported.

“What we’re seeing is that the Great Barrier Reef is still a resilient system. It still maintains that ability to recover from disturbances,” AIMS Long-Term Monitoring Program (LTMP) leader Mike Emslie told Reuters. “But the worrying thing is that the frequency of these disturbance events are increasing, particularly the mass coral bleaching events.”

Of the 87 reefs surveyed under the LTMP from August of last year to May of this year, the average hard coral cover in the area to the north of Cooktown, Australia, increased from 27 percent to 36 percent, Phys.org reported. In the central portion of the Great Barrier Reef, coral cover went up from 26 percent to 33 percent.

In the Reef’s southern region, however, average coral cover decreased to 34 percent from 38 percent last year.

AIMS CEO Dr. Paul Hardisty said the recovery in the north and central parts of the Reef showed its potential to bounce back, but not without persistent threats.

“A third of the gain in coral cover we recorded in the south in 2020/21 was lost last year due to ongoing crown-of-thorns starfish outbreaks,” Hardisty said, as reported by Phys.org. “This shows how vulnerable the Reef is to the continued acute and severe disturbances that are occurring more often and are longer-lasting.”

Experts from UNESCO visited the Great Barrier Reef in March, but whether the Reef will be listed as “in danger” has yet to be decided, as the World Heritage Committee meeting scheduled to be held in Russia in June was postponed, Reuters reported.

In 1998, the first mass bleaching on the Great Barrier Reef was recorded. Since then, five such events have occurred, with the most recent happening earlier this year during La Niña, reported The Guardian.

“The fact that we have had four bleaching events in the last seven years and the first one in a La Niña year is really concerning,” Emslie told The Guardian.

The AIMS report said that, due to climate change, the Great Barrier Reef would experience longer marine heatwaves more often, with the continuing threat of COTS.

The increased coral cover has been made up of fast-growing Acropora corals, which, according to AIMS, are especially susceptible to COTS, heat stress and damage from waves, Reuters reported.

Emslie said that, while the bleaching earlier this year hadn’t caused the corals to actually die, they were starving while they bleached and the event might affect their reproductive capabilities, make them more vulnerable to disease and put a strain on their growth, reported The Guardian.

As the climate crisis continues and bleaching events occur with more frequency, they could quickly undo the recent coral recovery, Emslie added.

“We’re really in uncharted waters when it comes to the effects of the bleaching and what it means moving forward. But as of today, it’s still a fantastic place,” said Emslie, as Reuters reported.

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