This new episode of massive bleaching, reported in March, is the fifth in eight years due to rising water temperatures. This decline threatens the survival of coral reefs in all four corners of the world, including the Great Barrier Reef, the US National Oceanic and Atmospheric Administration (NOAA) also warned on Monday.
The Great Barrier Reef, which stretches 2,300 km along the Queensland coast, is often considered the largest living structure in the world. It is home to an exceptionally rich biodiversity with more than 600 species of coral and 1,625 species of fish.
Aerial observations showed that about 730 of the more than 1,000 observed reefs were bleached, the marine park administration said on Wednesday.
This phenomenon is caused by an increase in the temperature of the water, which causes the expulsion of the symbiotic algae that give the coral its bright color. If high temperatures persist, the coral will turn white and die.
A ‘difficult’ summer for the Great Barrier Reef
In several areas of the marine park, “corals were exposed to record levels of heat”, the authority points out, noting that the 2023-2024 Australian summer was the second warmest ever observed in the region.
“The Great Barrier Reef is an incredible ecosystem, and while it has proven its resilience time and time again, this summer has been particularly challenging,” said Roger Beeden, chief scientist at the Marine Park Authority.
Another government report says up to 46% of reefs have experienced record heat stress, while only 20% of reefs were exposed in 2016.
“This is the most serious event the South Reef has experienced,” Richard Leck, WWF Australia’s head of oceans, told AFP, calling it “scary” that the bleaching was “more widespread” in areas that had been spared so far.
“Immediate action needed to reduce global emissions”
“We risk losing irreplaceable ecosystems forever unless we take immediate action to reduce global emissions,” warned Anna Marsden, director of the Great Barrier Reef Foundation.
During a recent mission to the Great Barrier Reef, AFP journalists visited one of the areas most affected by the phenomenon.
Lizard Island, a little slice of tropical paradise off the northeastern tip of Australia, would normally be teeming with thriving coral life. But today it is nothing more than a sea graveyard. Around 80% of the reef has been bleached this summer and many affected corals will struggle to survive.
Marine biologist Anne Hoggett has lived and worked on Lizard Island for 33 years. She says that when she arrived, coral bleaching only happened every ten years. Today, it occurs every year in a different proportion.
“We don’t know yet whether they’ve already suffered too much damage to recover or not,” he says.
According to WWF’s Mr Leck, “we won’t know for several months” what the “coral mortality” will be.
Australia has invested approximately A$5 billion (€3 billion) in improving water quality, reducing the impacts of climate change and protecting endangered species.
Thanks to these investments, UNESCO provisionally decided in August 2023 not to include the Great Barrier Reef on the list of endangered world heritage, as it had been threatening since 2021.
But Australia is also one of the largest producers of greenhouse gases, one of the largest exporters of natural gas and coal, and has only recently set goals that are considered unambitious to achieve carbon neutrality.
As reported by NOAA, this phenomenon is not limited to Australia: the American agency announced that the planet is experiencing the second largest episode of coral bleaching in the last ten years.
“Coral bleaching is becoming more frequent and more severe,” noted Derek Manzello, coordinator of NOAA’s Coral Reef Observatory, pointing to record ocean temperatures.
NOAA estimates that the planet has already lost 30 to 50% of its coral reefs, and they could disappear completely by the end of the century without major changes.