An official long-term monitoring program announced on Thursday that two-thirds of Australia’s Great Barrier Reef has the most coral cover in 36 years, but the reef remained susceptible to more frequent mass bleaching.
The rebound in the middle and northern lengths of the UNESCO world heritage-listed reef contrasted with a loss of coral cover in the southern area owing to crown-of-thorns starfish outbreaks, according to the Australian Institute of Marine Sciences (AIMS) in its annual report.
“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 monitoring programme 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,” he added.
Following a visit by UNESCO specialists in March, UNESCO is considering whether to label the Great Barrier Reef as “in danger” The World Heritage Committee meeting, which was supposed to take place in Russia in June but was postponed, was canceled.
Based on long-term reef surveys, AIMS classifies hard coral cover of more than 30% as high value in a critical metric of reef health.
The northern region’s average hard coral cover jumped to 36% in 2022 from 13% in 2017, while the central region’s hard coral cover improved to 33% from 12% in 2019 – the greatest levels recorded for both areas since the institute started monitoring the reef in 1985.
However, in the southern area, which has more hard coral cover than the other two zones, cover declined to 34% in 2022 from 38% the previous year.
The recovery follows the fourth global bleaching episode in seven years, and the first to occur during a La Nina phase, which generally brings lower temperatures. While broad, the bleaching in 2020 and 2022, according to the institution, was not as harmful as in 2016 and 2017.
On the negative side, Acropora corals, according to AIMS, are especially prone to wave damage, heat stress, and crown-of-thorns starfish.
“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,” Emslie said.