Highest ocean temperatures in 400 years threaten Great Barrier Reef

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

High temperatures pose major risk to the Great Barrier Reef’s marine ecosystem

Led by Benjamin Henley, a paleoclimatologist at the University of Melbourne, the study underscores the serious implications of this warming trend. The Great Barrier Reef, which stretches 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 rapid increases in sea surface temperatures are putting this unique biodiversity at grave risk.

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

The data has prompted scientists to question a recent decision by UNESCO’s World Heritage Committee not to upgrade the reef’s status from “critically endangered” to “endangered.” Helen McGregor, a co-author of the study and a paleoclimatologist at the University of Wollongong, expressed concern that the science clearly indicates the reef is in acute danger, which contradicts UNESCO’s assessment.

She warned that urgent action is needed to prevent further degradation. Despite the bleak outlook, Henley pointed out that there is still hope for the reef if global emissions can be reduced. He stressed that the tools to tackle the problem are available, but that the speed of action must be increased to preserve this natural treasure.