Scientists have pushed back hard against what they regard as a complacent assessment by the United Nations of the level of threat posed to the Great Barrier Reef by climate change.
At the end of July, UNESCO’s World Heritage Committee declined to list the GBR as “in danger” when it handed down its final decision on the state of the world’s biggest coral reef.
In contrast, in a new report just published in Nature, an Australian-American research team led by Dr Benjamin Henley of the University of Melbourne claims that the highest ocean heat in the past four centuries places the GBR firmly in danger. Warming sea temperatures and mass coral-bleaching events are threatening to destroy its ecology, biodiversity and beauty, they say.
Using coral skeleton samples taken from within and surrounding the Coral Sea, the scientists reconstructed annual summer sea-surface temperatures between 1618 and 1995. This data was combined with recorded sea-surface temperature data from between 1900 and 2024.
The team also analysed climate model simulations of sea-surface temperatures, run with and without climate change, and found that human-caused climate change was to blame for the region’s rapidly rising temperatures.
Recent mass-bleaching events were found to have coincided with five of the six hottest years in the 400 years covered by the study. In 2024, 2017 and 2020 the Coral Sea experienced the warmest temperatures in the entire period.
The current year is proving the warmest on record by a large margin. Heat events in 2016, 2004 and 2022 were the next warmest three years on record.
Off the charts
“When I plotted the 2024 data-point, I had to triple-check my calculations,” said Dr Henley. “It was off the charts, far above the previous record high in 2017. It is a tragic but near-inevitable consequence that mass coral-bleaching has occurred yet again this year.
“It’s the inevitability of the impacts on the reef in the coming years that really gets to me. In the absence of rapid, co-ordinated and ambitious global action to combat climate change, we will likely witness the demise of one of Earth’s most spectacular natural wonders.”
“Without urgent intervention, our iconic Great Barrier Reef is at risk of near-annual beaching from these high ocean temperatures,” concluded Dr Henley, who undertook most of the study as a post-doctoral researcher at the University of Wollongong. “The reef’s ecological integrity and outstanding universal value are at stake.
“We have many of the key solutions to turn climate change around. What we need is a step-change in the level of co-ordinated national and international action to transition to net zero. We hope that our study equips policy-makers with more evidence to pursue deeper cuts in greenhouse gas emissions internationally.”
“Most World Heritage properties are also vulnerable to climate change,” stated UNESCO in declining to declare the GBR in danger. “Australia is delivering an ambitious environment and climate agenda, at home and abroad, to achieve a net-zero and nature-positive world.
“We are supporting global efforts to protect all World Heritage properties from the impact of climate change. We are a world leader in reef management and will continue to share our expertise with international partners, to protect more of what’s precious, restore more of what’s damaged, and manage nature for the future.”
Also on Divernet: GBR BLEACHING AGAIN – AS FISH FADE TO GREY, MASS GBR BLEACHING EVENT CONFIRMED, RUN-OFF IS LATEST THREAT TO GBR, GBR TRIP REVEALS UNKNOWN CORALS
