Great barrier reef coral loss largest in decades amid bleaching crisis
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Scientists describe the impact of the recent coral bleaching event in a first of it's kind report from The Australian Institute of Marine Science, showing environmental damage unseen since the 1980s.
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A school of grunt fish swims under a piece of coral at a coral reef off the coast of Aruba on May 13, 2024. (Joseph Prezioso/AFP via Getty Images)
The Great Barrier Reef has experienced its most severe annual decline in live coral cover in nearly four decades, according to a new report by the Australian Institute of Marine Science (AIMS). The findings underscore the mounting pressures on coral reefs and the broader environment due to climate-induced events, including widespread coral bleaching and extreme weather.
The report is the first comprehensive assessment of the early 2024 coral bleaching event, deemed the most widespread and intense ever recorded on the reef. The damage has previously been described as catastrophic, with scientists encountering what they dubbed a “graveyard of corals” around Lizard Island in the north, and surveys revealing a 40% coral mortality rate at One Tree Island in the south.
AIMS has been conducting in-water surveys of the reef since 1986. This year’s results show a dramatic decrease in coral cover across large sections of the reef. In the northern region, from Cooktown to the tip of Cape York, coral cover dropped by 25% due to bleaching, cyclones, and associated flooding. In the southern zone, spanning Mackay to just north of Bundaberg, coral cover declined by 30%. Both represent the most significant annual losses ever recorded in these zones.
The central region, which avoided the worst of the 2024 heatwave, saw a smaller but still significant 13% drop in coral cover.
Scientists fear irreversible impact without emission cuts
Dr. Mike Emslie, head of the long-term reef monitoring program at AIMS, described the situation as increasingly volatile, noting, “It has been a pretty sobering year of surveys with the biggest impacts I have seen in the 30-plus years I have been doing this."
According to Emslie, signs of coral reef recovery were present in recent years, reaching record levels of coral cover in some areas. However, that recovery was largely driven by fast-growing acropora corals, which are more vulnerable to heat stress.
“We had said it could all get turned around in one year and, lo and behold, here we are,” he said. Coral cover is now broadly in line with long-term averages, but the system’s stability is under threat.
The 2024 and 2025 bleaching events are part of a wider global phenomenon that has affected over 80% of the planet’s coral reefs across at least 82 countries and territories. Last year, a study concluded that ocean temperatures on the Great Barrier Reef were likely the highest in at least 400 years, posing what researchers described as an “existential threat” to the UNESCO world heritage-listed site.
Widespread coral bleaching on the Great Barrier Reef has now been recorded in 1998, 2002, 2016, 2017, 2020, 2022, 2024, and 2025. The increasing frequency of these events is leaving little time for coral reefs to recover between cycles.
“These impacts we are seeing are serious and substantial, and the bleaching events are coming closer and closer together,” Emslie warned. “We will ultimately get to a tipping point where coral cover can’t bounce back because disturbances come so quickly that there’s no time left for recovery.”
He stressed that addressing the root cause, climate change, must remain a priority, noting that “We have to mitigate the root causes of the problem and reduce emissions and stabilise temperatures."
Urgent action needed to support coral reef recovery
The AIMS report comes just weeks ahead of the Australian federal government's announcement of its 2035 emissions reduction target. Last year, the Albanese government assured UNESCO that it would set “successively more ambitious emissions reduction targets” aligned with the goal of limiting global warming to 1.5°C.
In a report released last week, the Climate Change Authority emphasized that keeping warming “as close as possible to 1.5°C” is essential to reduce the threat facing the reef and to enable coral reef recovery.
Richard Leck, head of oceans at WWF Australia, echoed this sentiment, stating, “This is the one action the government can take to give the reef a fighting chance.”
