Scientists have recorded the largest annual coral bleaching event in the history of the Barrier Reef

This was reported by the Australian Institute of Marine Science in its annual review.

Although coral cover has gradually increased since 2017, severe bleaching caused by climate change in 2024 has severely damaged the reef. Nevertheless, the total area of live coral has so far remained close to the annual average over the entire monitoring period. Scientists note that the situation emphasises the growing instability of the ecosystem of the UNESCO World Heritage site.

According to Mike Emsley, head of the long-term monitoring programme, 2024 recorded the highest level of living coral cover in almost four decades of observations. Losses from such a high 'starting point' have partially mitigated the effects of climate stressors, but this does not change the alarming trend.

Over the year, the area of living coral has declined by almost a third in the southern part of the reef, a quarter in the northern part and 14 per cent in the central part.

According to the US National Oceanic and Atmospheric Administration, the world is experiencing the largest mass coral bleaching event in history and the fourth largest ever. It began in January 2023 and was declared a global crisis in April 2024. Heat stress has affected nearly 84 per cent of all coral reefs on the planet, including the Great Barrier Reef.

A survey of 281 reefs in the Torres Strait and northern Barrier Reef found that 78 reefs had more than 30% coral bleaching.

Bleaching occurs when corals in prolonged high water temperatures expel the symbiotic algae that provide their colour and nutrition. White corals are not always dead, but they are weakened and vulnerable to disease. With a warming of more than 1.2 °C, tropical coral ecosystems could virtually disappear.

The UN Intergovernmental Panel on Climate Change warned back in 2018 that coral reefs are among the most vulnerable ecosystems. Already, global warming has reached 1.3 °C relative to pre-industrial levels, and recent events in the Barrier Reef confirm that the risks to corals have been underestimated.