Great Barrier Reef recovery underway thanks to late-summer monsoon

Findings from the 40th AIMS report reveal that coral cover either grew modestly or held steady across the reef's northern, central and southern zones compared with the previous year.

All three regions maintained coral cover at or close to their long-term averages, suggesting the 2025 mass bleaching event and a regional bleaching episode in early 2026 had only limited effects.

Across the 2025/26 field season, the northern region stretching from Cape York to Cooktown saw coral cover climb from 30 per cent to 35.1 per cent, a rise of 16.7 per cent.

The central zone between Cooktown and Proserpine recorded a 10.2 per cent increase, moving from 28.6 per cent to 31.6 per cent, though this fell within the margin of error.

In the southern region from Proserpine to Gladstone, cover dipped marginally from 26.9 per cent to 26.4 per cent.

Scientists examined 121 individual reefs, of which 106 showed moderate to high coral cover.

Just three had hard coral cover below 10 per cent, with data showing 56 per cent of reefs surveyed were unchanged, 28 per cent improved, and 16 per cent declined.

Dr Mike Emslie, who leads the AIMS Long-Term Monitoring Program, said: "The Reef experienced a summer of above-average sea temperatures once again, but the late summer monsoon activity, which increased cloud cover and reduced sea temperatures, likely limited the severity and extent of bleaching in the 2025/26 summer."

Dr Emslie warned that reefs where fast-growing, habitat-forming Acropora corals dominate were hit hardest by the 2024 mass bleaching event, based on detailed surveys of permanently marked sites at 71 reefs.

He said: "The reefs with high levels of Acropora now exist in a highly vulnerable state. It's possible that what looks like complete recovery on these reefs can be reversed in just a year."

The 2024 event also pushed bleaching into unusually deep waters.

Coral mortality increased at depths of 10 to 15 metres across the southern reef, affecting most coral types, a pattern typically confined to shallower areas where temperatures peak highest.

Dr Emslie cautioned that future warming trends would likely expose deeper corals to increasingly severe bleaching impacts.

Despite signs of resilience, the reef remains a system under significant strain.

Six mass bleaching events struck between 2016 and 2025, whereas before the 1990s such episodes were exceptionally rare.

Rising crown-of-thorns starfish numbers in the northern reef point to the fifth recorded outbreak wave since the 1960s, compounding damage from cyclones and flooding.

Dr Emslie said: "While the Reef is showing resilience, it is being pushed and its capacity to recover is limited."

AIMS chief executive Professor Selina Stead stressed that cutting global emissions, sound reef management and developing science-based interventions to support adaptation were essential to helping coral reefs withstand mounting climate threats.

She said: "While evidence of recovery is encouraging, the risks for coral reefs are increasing."