High coral growth observed on Australia’s Great Barrier Reef

• Coral cover on two-thirds of Australia’s Great Barrier Reef has reached its highest level in 36 years.
• Recovery was limited to the central and northern stretches of the UNESCO world heritage-listed reef.
• Climate change is causing more frequent and longer-lasting marine heatwaves.

According to marine scientists monitoring the ecosystem, coral cover on two-thirds of Australia’s Great Barrier Reef has reached its highest level in 36 years.

However, the coral remains highly vulnerable to mass bleaching events, which are becoming more common as human activity warms the oceans, according to the Australian Institute of Marine Sciences (AIMS) in its annual report.

The recovery in the central and northern stretches of the UNESCO world heritage-listed reef did not extend to the southern region, which lost coral cover due to an outbreak of crown-of-thorns starfish.

The Great Barrier Reef is still a “resilient system,” with the ability to recover from disturbances, according to AIMS monitoring programme leader Mike Emslie.

“But the worrying thing is that the frequency of these disturbance events are increasing, particularly the mass coral bleaching events,” he added.

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

Climate change, according to Dr. Emslie, is causing more frequent and longer-lasting marine heatwaves.
“The increasing frequency of warming ocean temperatures and the extent of mass bleaching events highlights the critical threat climate change poses to all reefs, particularly while crown-of-thorns starfish outbreaks and tropical cyclones are also occurring,” he said.

“Future disturbance can reverse the observed recovery in a short amount of time,” he warned.

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

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

The report comes as UNESCO considers whether to list the Great Barrier Reef as “in danger” following a visit by the United Nations body in March.

The issue was scheduled to be discussed at a World Heritage Committee meeting in Russia in June, but it was postponed.

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

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

However, in the southern region, which has higher hard coral cover than the other two, cover fell to 34% in 2022 from 38% the previous year.

Also Read

Global warming kills 14 percent of world’s corals in a decade

Dynamite fishing and pollution -- but mostly global warming -- wiped out...