Photo: Albert Plawinski/Flickr Creative Commons

A global coral bleaching event that’s been killing reefs around the world since early 2015 finally appears to be ending, according to a report just released by the National Oceanic Atmospheric Administration. That said, reefs aren’t out of hot water yet.

For nearly three years, coral reefs—which grow mainly in warm, tropical waters near the equator—have suffered a mass bleaching event due to excessive heat. Coral, a squishy animal wrapped in a crunchy exoskeleton that contains colorful algae called zooxanthellae, has a tendency to evict its photosynthetic roommates when the water gets just a few degrees too warm. Seeing as those roommates provide coral with all of its food, this is bad news. It causes the coral to turn a ghostly white, and eventually, starve.

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That’s what’s been happening around the world since the beginning of 2015, when NOAA declared a global bleaching event, the third on record. Since then, we’ve seen massive coral die-offs in Australia’s Great Barrier Reef, as well as reefs in Florida, Hawaii, and across the South Pacific. A satirical eulogy to the Great Barrier Reef went viral last year, and, as if it underscore how truly dire things are, loads of people thought it was real.

Now, after nearly three years of stewing in overheated water—due in part to a strong El Niño and in part to you-know-what—reefs around the world finally seem to be catching a break. NOAA’s latest coral bleaching heating stress outlook, which uses ocean temperature data from satellites and climate models, shows that temperatures in all three major ocean basins—the Atlantic, Pacific, and Indian—are simmered down to the point that a global bleaching event is no longer likely.

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Scientists will continue to monitor temperatures over the coming months to confirm that the bleaching event is, in fact, over.

That doesn’t mean everything’s suddenly fine. As this latest bleaching event showed, coral reefs, which support roughly 25 percent of all marine species, are incredibly sensitive to even small changes in the temperature. And as long as humans keep dumping billions of tons of carbon into the atmosphere each year, temperatures will keep rising. Bleaching events are expected to become more frequent and more severe in a warming world, leaving reefs less time to recover in between bouts of starvation. Plus, as NOAA notes, certain coral reefs, including reefs in Hawaii and the Caribbean, continue to be at risk for bleaching this summer.

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“We’re hoping a lot of reefs will get some time to recover before the next bleaching comes,” Mark Eakin, Coral Reef Watch Coordinator at NOAA, told Gizmodo. “The problem is, 2017 is tracking right at the second warmest year on record,” even without the El Niño climate pattern causing a buildup of warm water across the tropical Pacific.

“Now we’ve got no tropical forcing, but a lot of warmth that’s been absorbed by upper ocean, and no place for it to go,” Eakin continued.
“So it’s not going to take as much to push [reefs] over the limit again.”

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The oceans are catching a well-deserved break—but we’re going to need to get our shit together fast if we actually want to save the reefs.

[NOAA]

This post has been updated to include comments from Mark Eakin.