The Great Barrier Reef in Australia is showing the most coral cover it has seen in 36 years in its central and northern lengths, suggesting that the vulnerable UNESCO World Heritage site may yet be able to recover from decades of destruction. However, the study found that the southern portion of the reef had less coral cover and that it was becoming more susceptible to common disturbances like mass bleaching occurrences.
The Australian Institute of Marine Sciences (AIMS) said in its annual summary report that the average hard coral cover increased in the northern section of the reef to 36 percent in 2022 from 27 percent in 2021 and increased in the central region to 33 percent in 2022 from 27 percent in 2021.
Despite this, the CEO of AIMS, Dr. Paul Hardisty, stated in a statement that “a third of the improvement in coral cover we reported in the south in 2020/21 was lost last year due to continuous crown-of-thorns starfish outbreaks.” This demonstrates how susceptible the Reef is to the ongoing, acute, and severe disturbances that are happening more frequently and staying longer.
Since 1986, AIMS has kept an eye on the Great Barrier Reef. It declared that the rising frequency of mass bleaching episodes, which occur when coral loses its pigments and symbiotic algae in reaction to stressful conditions like heat, becomes white, and possibly dies, were “uncharted territory.”
“In our 36 years of monitoring the condition of the Great Barrier Reef we have not seen bleaching events so close together,” Hardisty said. “Every summer the Reef is at risk of temperature stress, bleaching and potentially mortality and our understanding of how the ecosystem responds to that is still developing.”
The majority of the coral growth in the north and center of the reef, according to Dr. Mike Emslie of the AIMS monitoring program, was caused by fragile but quickly developing Acropora corals, and could thus be quickly reversed.
“These corals are particularly vulnerable to wave damage, like that generated by strong winds and tropical cyclones,” Emslie said. “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. Future disturbance can reverse the observed recovery in a short amount of time.”