The Great Barrier Reef is facing the highest ocean temperatures in 400 years, threatening the survival of corals.

The Great Barrier Reef, one of the world’s most iconic natural wonders, is facing an unprecedented threat due to the highest sea surface temperatures recorded in 400 years. A recent study published in the journal Nature reveals that temperatures in the first three months of 2024 reached 0.19°C above the previous record. This alarming rise has led to widespread coral bleaching, where corals expel the algae that provide them with food and vibrant colours, leaving them white and susceptible to disease and death.

High temperatures pose a serious threat to the Great Barrier Reef’s marine ecosystem

The study, led by Benjamin Henley, a paleoclimatologist at the University of Melbourne, highlights the serious implications of this warming. The Great Barrier Reef, stretching more than 1,400 miles off the coast of Queensland, is home to the world’s largest collection of coral reefs and an incredibly diverse marine ecosystem. But rapidly rising sea surface temperatures are now putting this unique biodiversity at significant risk.

To understand the historical context, researchers reconstructed sea surface temperatures from 1618 to 2024. They used a combination of ship- and satellite-based data and coral cores recovered from the reef itself. These coral cores act as natural archives, with their strontium-to-calcium ratios providing information about past water temperatures. The study found that summer temperatures from 2016 to 2024 were almost 1.7°C warmer than the coolest summers of the past four centuries.

The data has prompted scientists to question the recent decision by UNESCO’s World Heritage Committee not to upgrade the reef’s status from “seriously threatened” to “dangerous.” Helen McGregor, a co-author of the study and a paleoclimatologist at the University of Wollongong, said the science clearly shows the reef is in imminent danger, contradicting UNESCO’s assessment.

She warned that urgent action was needed to prevent further degradation. Despite the bleak outlook, Henley said there was still hope for the reef if global emissions could be reduced. He stressed that the tools to address the problem were available, but that the speed of action needed to increase to preserve this natural treasure.