84% of world's coral reefs struck by worst bleaching event in history

Yahoo

23-04-2025

April 23 (UPI) -- More than 80% of the world's coral reefs fell victim to harmful bleaching and is now in "uncharted territory" with the worst global bleaching event in recorded history.
The coral reef system in at least 82 nations and other territories have been exposed to enough heart to turn at least 84% of the world's coral white since the global event started last year in January, according to data by the U.S. government's Coral Reef Watch.
"Reefs have not encountered this before," said Dr. Britta Schaffelke of the Australian Institute of Marine Science and coordinator of the Global Coral Reef Monitoring Network, adding it was "unprecedented" and now the most intense event of its kind ever recorded.
When water is too warm, coral will expel the algae -- otherwise known as zooxanthellae -- living in their tissues which causes the coral to turn completely white, according to the National Oceanic and Atmospheric Administration.
During coral bleaching events, environmental stress like temperature change will trigger a breakup of the symbiotic relationship between coral and algae, which is now spreading like a wildfire to corals across the Pacific, Atlantic and Indian oceans and killing countless coral habitats.
Otherwise known as the "rainforests of the sea," coral supports biodiversity and about a third of all marine species and at least a billion people.
Although corals can recover from bleaching if temperatures are less extreme, past surveys have indicated a bleak picture of widespread global coral elimination.
NOAA said last April that the world's oceans were undergoing the fourth global coral bleaching event on record and its second in the last 10 years as scientists in Florida, Mexico and the Caribbean raised alarm bells that summer over extreme bleaching in the northern hemisphere.
Scientists further describe a "graveyard of dead corals" in Australia's northern Great Barrier Reef following 2024's bleaching event that caused about 40% of its coral life to die in one spot to its south.
In Florida, where divers worked to save the Sunshine State's coral reefs, an average of one in five corals were lost and on Mexico's Pacific side, one area lost nearly 93% of its corals. But while warming water temps -- a result of climate change -- are a primary driver, newer research suggests that nitrogen pollution is the main cause of coral bleaching in Florida.
Meanwhile, almost a quarter of corals were killed by heat last year in the middle of the Indian Ocean in the remote Chagos Islands.
"Bleaching is always eerie -- as if a silent snowfall has descended on the reef," said Melanie McField, founder of the Caribbean-based Healthy Reefs for Health People initiative. "There is usually an absence of fluttering fish and an absence of the vibrant colors on the reef. It's an ashen pallor and stillness in what should be a rowdy vibrant reefscape."
The report came as U.S. President Donald Trump has taken steps to boost fossil fuel production and a rollback of clean energy programs.
"World leaders need to really commit to reduce fossil fuels and increase investments in clean energies and make it a reality," said Dr. Valeria Pizarro, a senior coral scientist at the Perry Institute for Marine Science working on reefs in the Bahamas and Caribbean Sea.
The small island nation of Palau in the western Pacific experienced intense marine heatwaves in 1998, 2010 and 2017, but interestingly, each successive event led to less coral bleaching. However, scientific consensus is that ultimately the future of coral reefs will depend on a rapid reduction of carbon emissions which runs counter to Trump administration policy.
"We need them to stop having it on paper and on the news, we need it to be real," Pizarro said.