A mass coral bleaching event in 2024 has led to a significant decline in the Great Barrier Reef’s coral cover, with regional declines ranging from 14% to 30% compared to 2024 levels. The Northern GBR saw the largest annual decline, while the Southern GBR experienced its biggest region-wide annual decline yet recorded.
The 2024 event was part of an ongoing global mass bleaching event that began in 2023 and has resulted in severe coral mortality. Fast-growing Acropora corals, which facilitated rapid recovery between 2017 and 2024, were among the most severely impacted by the bleaching event.
Regional hard coral cover declined as follows: Northern GBR (30.0% from 39.8%), Central GBR (28.6% from 33.2%), and Southern GBR (26.9% from 38.9%). Crown-of-thorns starfish were detected on 27 reefs, with severe outbreaks reported in the Southern GBR.
Above-average water temperatures occurred again during the austral summer of 2025, peaking in March, leading to a coral bleaching event in the Northern GBR and parts of the Central GBR. The impact on coral cover will be captured in next year’s report.
The Great Barrier Reef is under severe cumulative pressure, with coral cover gains reversed over the 2024 summer. While the reef retains higher coral cover than many reefs globally, mass coral bleaching events are now occurring with increasing frequency, while recovery periods are decreasing.
Source: https://www.aims.gov.au/monitoring-great-barrier-reef/gbr-condition-summary-2024-25