This photo supplied by the Great Barrier Reef Marine Park Authority (GBRMPA) shows diseased corals at a reef in the Cairns/Cooktown on the Great Barrier Reef in Australia, April 27, 2017

The amount of coral in some areas of the Great Barrier Reef is at its highest in 36 years, according to a new report from the Australian Institute of Marine Science. From August 2021 to May 2022, the central and northern regions of the Great Barrier Reef had hard coral cover levels of 33% and 36%, respectively. Coral cover decreased by 4% in the southern region, due to an outbreak of crown-of-thorns starfish.

The Australian agency found that 87 coral reefs generally had low levels of acute stress from things such as cyclones and increases in the crown-of-thorns starfish population. (Crown-of-thorn starfish are the second largest in the world, reaching up to three feet, and prey on coral. They have spikes with venom that is toxic to humans and marine wildlife.)

The area surveyed represents two-thirds of the Great Barrier Reef.

Almost half of the reefs studied had between 10% and 30% hard coral cover, while about a third of the reefs had hard coral cover levels between 30% and 50%, the report said.

While higher water temperatures led to a coral bleaching event in some areas in March, the temperatures did not climb high enough to kill the coral, the agency said. Coral in the Great Barrier Reef is resilient, and has been able to recover from past disturbances, the Institute said. But the stressors impacting it have not gone away for long.

The agency's outlook shows more frequent and long-lasting heatwaves, cyclones and crown-of-thorns starfish.

"Therefore, while the observed recovery offers good news for the overall state of the [Great Barrier Reef], there is increasing concern for its ability to maintain this state," the report said.