84% of the world’s coral reefs hit by worst bleaching event on record

Harmful bleaching of the world’s coral has grown to include 84% of the ocean’s reefs in the most intense event of its kind in recorded history, the International Coral Reef Initiative announced Wednesday.

It’s the fourth global bleaching event since 1998, and has now surpassed bleaching from 2014-17 that hit some two-thirds of reefs, said the ICRI, a mix of more than 100 governments, non-governmental organizations and others. And it’s not clear when the current crisis, which began in 2023 and is blamed on warming oceans, will end.

“We may never see the heat stress that causes bleaching dropping below the threshold that triggers a global event,” said Mark Eakin, corresponding secretary for the International Coral Reef Society and retired chief of the Coral Reef Watch program of the U.S. National Oceanic and Atmospheric Administration. “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,” Eakin said.

Last year was Earth’s hottest year on record, and much of that is going into oceans. The average annual sea surface temperature of oceans away from the poles was a record 20.87 degrees Celsius.

That’s deadly to corals, which are key to seafood production, tourism and protecting coastlines from erosion and storms. Coral reefs are sometimes dubbed “rainforests of the sea” because they support high levels of biodiversity — approximately 25% of all marine species can be found in, on and around coral reefs.