Australian scientists have reported the sixth mass coral bleaching event on the Great Barrier Reef since 2016, highlighting the ongoing threats of climate change to one of the world’s most iconic natural wonders.
In a report released on Wednesday night, federal agencies including the Great Barrier Reef Marine Park Authority, the Australian Institute of Marine Science, and the Commonwealth Scientific and Industrial Research Organisation revealed that the reef experienced a “widespread coral bleaching event” during the summer of 2024-25.
“Prolonged heat stress throughout the Far Northern and Northern regions of the reef caused widespread bleaching,” the report stated.
This marks not only the sixth mass bleaching event since 2016 but also the second consecutive year that such severe bleaching has occurred. Coral bleaching happens when corals, stressed by unusually warm water temperatures, expel the symbiotic algae living in their tissues, causing them to turn white. While bleaching is not immediately fatal, bleached corals are more susceptible to starvation and disease, and full recovery can take a decade or more.
Out of the 162 inshore and mid-shelf reefs monitored from the air, 41% recorded medium to high levels of bleaching. In the Great Barrier Reef Marine Park, 9% of reefs exhibited very high levels of bleaching, though none were categorized as having extremely high prevalence.
Richard Leck, head of oceans at the Australian branch of the World Wide Fund for Nature (WWF), expressed deep concern over the findings. “Bleaching is becoming the new normal for the reef,” he said. “Year after year, the reef is being cooked by underwater heatwaves. It’s our international treasure, and it desperately needs serious action to drive down emissions.”
Beyond coral bleaching, the report also noted that the reef faced additional challenges over the past summer, including cyclones, outbreaks of the invasive crown-of-thorns starfish, freshwater inundation, and coral diseases.
