For decades, marine scientists have been warning of the demise of coral reefs in a warming world. But now, those warning calls have reached a full-scale alarm, leaving researchers at a loss for exactly how best to save the reefs.

A study published Thursday in Science by some of the world’s top coral experts amounts to a last rites for the ecosystems often referred to as “the tropical rainforests of the sea.” Scientists surveyed 100 reefs around the world and found that extreme bleaching events that once occurred every 25 or 30 years now happen about every five or six years.

With the time transpiring between bleaching events shortened by a factor of five, there isn’t adequate time for the ecosystems to recover. Even the fastest-growing corals that survive a major bleaching event need about 10 years to regain their health. These damaging events are now occurring more quickly virtually eliminates any serious chance of large-scale recovery on a global scale. Huge portions of the world’s reefs face almost certain death — and that loss will reverberate beyond earth’s oceans.

“These impacts are stacking up at a pace and at a severity that I never had anticipated, even as an expert,” says Kim Cobb, a climate scientist and coral researcher at the Georgia Institute of Technology. “It’s really the rapidity of it that is so sobering and shocking — and for me personally, life-altering.”

Cobb, who is not affiliated with the new study, had first-hand experience with the latest and most severe instance of global coral bleaching: a three-year event that hit almost every major reef system in the world and eventually decimated portions of the Great Barrier Reef. In 2016, around the height of the bleaching, she made a series of dives off remote Kiritimati Island, due south of Hawaii. There, Cobb watched in horror as roughly 80 percent of one of the most pristine coral ecosystems in the world died in a matter of months.