'Worst I Have Seen': 75% of Great Barrier Reef Suffers Coral Bleaching

Marine conservationists warned Thursday that Australia's Great Barrier Reef may be suffering its worst-ever coral bleaching event amid record ocean heat fueled by the worsening climate emergency.

The Australian Marine Conservation Society (AMCS) said that bleached corals have been found at depths of up to nearly 60 feet, and "some corals are starting to die as they face record marine heatwaves."

"Corals bleach when they are stressed by warmer waters for an extended period of time—during marine heatwaves, which are driven by climate change," AMCS explained. "They expel the algae that inhabit them, which is their main energy source and they starve, sometimes to death."

Data collected from aerial surveys shows that 75% of the Great Barrier Reef has bleached during the current event, which the U.S. National Oceanic and Atmospheric Administration warned last month is likely to be "the worst bleaching event" ever observed in the world.

"This new footage shows extensive coral bleaching in southern reefs, but there are images from the central and northern parts that show bleaching is extensive and severe in some of those areas too," AMCS Great Barrier Reef campaign manager Lissa Schindler said in a statement.

"The Great Barrier Reef is experiencing an unprecedented fifth mass coral bleaching in eight years," Schindler added. "This is worse than the past two mass bleaching events—in 2020 and 2022—and we may discover as bad as the worst bleaching on record in 2016."

According to AMCS:

Some regions in the southern reef have experienced unprecedented marine heatwaves, with elevated water temperatures for a record 14.57 degree heating weeks (DHW)—a measure of excessive heat over time—breaking the previous record of 11.8 DWH set in April 2020, according to data from the U.S. government's world-leading ocean agency, the National Oceanic and Atmospheric Administration.

"I feel devastated. This bleaching event is the worst I have seen. It's a severe bleaching event," said Selina Ward, a coral reef expert and the former academic director of the University of Queensland's Heron Island Research Station.

Ward, who reported extensive bleaching at all 16 sites she just visited along the southern Great Barrier Reef, added: "I've been working on the reef since 1992 but this I'm really struggling with. The diversity of species involved has been hard to deal with. Look at bleached areas, there are many different species that are bleached—many of which are pretty resistant to bleaching."

It's not just Australia or even the Southern Hemisphere. Following the planet's hottest summer on record last year, the Caribbean suffered its worst recorded bleaching event.

The last global bleaching occurred in 2014-17, when scientists say approximately 15% of all reefs experienced major coral deaths. Nearly a third of the Great Barrier Reef's coral perished during that event—a die-off that could be eclipsed this time.

"This bleaching event again brings us to the question, what are we doing to stop the reef from being lost?" Ward asked. "I can't help but wonder what it is going to take for the right decisions to be made."

"We are really running out of time. We need to reduce our emissions immediately," she added. "We cannot expect to save the Great Barrier Reef and be opening new fossil fuel developments. It's time to act and there are no more excuses."