The Worst Bleaching Event on Record Is Hitting Most of the World’s Coral Reefs
Scientists are alarmed by the ongoing crisis, with deteriorating conditions harming marine life in the tropics and beyond
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More than 80 percent of the world’s reefs have been exposed to the worst bleaching event in history, according to a report from NOAA and the International Coral Reef Initiative.
Coral reefs—dubbed the “rainforests of the sea"—are a vital part of the marine ecosystem. They support biodiversity, protect coastlines from storms and erosion, and are an important source of tourism in many parts of the world. But as oceans get warmer, they are increasingly under threat.
Heat stress causes corals, iconic marine invertebrates, to expel the symbiotic algae that live in their tissues and lose their vibrant colors and vital nutrients in the process. “Bleaching becomes more severe if either the heat stress episodes are more intense or if they last for a longer time,” explains Joerg Wiedenmann, a marine biologist at the University of Southampton, in an email to the Washington Post.
Melanie McField, the founder and director of the Healthy Reefs for Healthy People initiative, tells the Guardian a bleaching event is like a “silent snowfall” descending on a reef. “There is usually an absence of fluttering fish and an absence of the vibrant colours on the reef," she says. "It’s an ashen pallor and stillness in what should be a rowdy vibrant reefscape.”
Since 2023, mass bleaching of coral reefs has been confirmed throughout the tropics. Florida’s corals were hit hard in 2023 because of unprecedented heat—the Florida Keys experienced 100 percent coral bleaching. Australia’s Great Barrier Reef faced a catastrophic bleaching event in 2024. And reefs in the Persian Gulf, the Caribbean and the Red Sea have all also experienced bleaching.
A 2014 to 2017 bleaching event previously held the record, according to NOAA. Almost 70 percent of reefs were exposed to bleaching-level heat at the time. The first two mass bleaching events in history occurred in 1998 and 2010.
This current bleaching event is still ongoing, and scientists aren't sure when—if ever—it’ll end.
“We may never see the heat stress that causes bleaching dropping below the threshold that triggers a global event,” says Mark Eakin, the corresponding secretary for the International Coral Reef Society, to Isabella O’Malley at the Associated Press. “We’re looking at something that’s completely changing the face of our planet and the ability of our oceans to sustain lives and livelihoods.”
Britta Schaffelke, a researcher at the Australian Institute of Marine Science, tells Graham Readfearn at the Guardian that the current global-scale coral bleaching takes reefs into uncharted waters./https://tf-cmsv2-smithsonianmag-media.s3.amazonaws.com/filer_public/7d/d5/7dd53841-da51-4f34-9488-8539179c4a4a/photo-usvi-boulder-coral-recovery-3panel-041523-noaa.jpg)
Still, corals are highly resilient, and, if given the chance, could bounce back. Scientists say that global efforts to mitigate climate change are needed in order to help them recover. That involves implementing more policies that aim to reduce greenhouse gas emissions
“The ancestors of today’s corals survived the impact of the asteroid that wiped out the dinosaurs on land and a lot of creatures in the sea,” says Wiedenmann to the Washington Post, “So, if we manage to decrease ocean warming, there is always a chance for corals to recover.”
Valeria Pizarro, a senior coral scientist at the Perry Institute for Marine Science, tells the Guardian world leaders need to invest more in clean energies and commit to reducing fossil fuels to help reefs.
The news on reefs comes, the AP notes, as the Trump administration has moved to boost fossil fuels and reduce clean energy initiatives, which is cause for concern to coral researchers. “Removing these protections is going to have devastating consequences,” says Eakin.
