Great Barrier Reef becoming more fragile
A 2025 survey finds a steep decline in coral cover across reef regions.
What’s Happening?
The Great Barrier Reef has recorded one of the most dramatic annual declines in coral cover in its 39-year monitoring history, according to the Australian Institute of Marine Science’s (AIMS) latest Long-Term Monitoring Program (LTMP) report.
The 2025 report covers surveys conducted between August 2024 and May 2025 and focuses on the impacts of the 2024 mass bleaching event.
Why It Matters
The AIMS report reveals a new level of coral cover volatility, signalling that the Reef ecosystem is under growing stress.
“We have seen coral cover oscillate between record lows and record highs in a relatively short amount of time,” said Dr Mike Emslie, LTMP leader at AIMS.
“This year’s record losses in hard coral cover came off a high base, thanks to the record high of recent years.”
Local Impact
Coral loss was observed across all regions, with significant reductions noted even in areas previously less impacted.
The southern region, from Proserpine to Gladstone, experienced substantial bleaching for the first time, leading to its largest recorded decline.
By the Numbers:
Northern region (Cape York to Cooktown) coral cover dropped from 39.8% to 30%
Central region (Cooktown to Proserpine) fell from 33.2% to 28.6%
Southern region (Proserpine to Gladstone) declined from 38.9% to 26.9%
Zoom In
A total of 124 reefs were surveyed. Most reefs (77) recorded hard coral cover between 10% and 30%, while 33 reefs had coral cover between 30% and 50%. Only two reefs exceeded 75% coverage and two had less than 10%.
Coral species most impacted were Acropora, known for rapid growth but high vulnerability to heat, cyclones and crown-of-thorns starfish.
Zoom Out
“This was the fifth mass bleaching event since 2016 and had the largest spatial footprint recorded,” said AIMS CEO Professor Selina Stead.
“It’s the first time we’ve seen a single bleaching event affect almost all the coral reefs in Australia.”
What To Look For Next?
The report signals a call for continued reef monitoring and adaptation strategies.
Peer-reviewed findings from detailed in-water bleaching surveys will be released to further verify the manta tow results and assess mortality causes across reef sites.