At about the same moment that millions of Americans sat staring at their television or laptop or phone—watching the results from the presidential election stream in, seeing state after state called for Donald Trump—Kim Cobb was SCUBA diving near the center of the Pacific Ocean. She did not watch the same trickle of news as other Americans. She surfaced, heard the results, and dove in the water again. She was, after all, attending to devastation.Cobb is a climate scientist at the Georgia Institute of Technology. On November 8, she was on her most recent of many research trips to Kiritimati Island reef, the largest coral atoll in the world. (Kirimati is pronounced like Christmas.) She first began studying the reef in 1997, during the last big El Niño warming event; she has returned nearly every year since. Last year, she went three times.“We had been waiting for the big one. And boy… did it happen,” she told me earlier this year. “It really rolled out at an unprecedented magnitude. This particular El Niño event had its maximum temperature loading almost in a bulls-eye almost around Kirimati Island.”
By any measure, its caused a cataclysm. Eighty-five percent of the corals in the reef died: They will never recover, disintegrating into sand over the next several years. Two-thirds of the surviving corals bleached in some way, meaning they did not reproduce and may have sustained long-term damage.“Almost none of this reef has made it through 2015 and 2016,” Cobb said, calling the event “the wholesale destruction of the reef.”By any measure, 2016 was not a good year for coral reefs. El Niño raised ocean temperatures worldwide, devastating corals the world over. The Great Barrier Reef—the sprawling system off the coast of Australia, and among the world’s most biodiverse reef systems—suffered a particularly debilitating year. Miles and miles of the coral reef bleached so severely, and for so long, that they died.
On Monday, news broke that it happened again. For the second year in a row, warm ocean temperatures are bleaching the Great Barrier Reef. The white splotches of ocean floor indicative of the phenomenon run even farther south—some 500 kilometers—than they did last year. The bleaching occurred even though there is no worldwide El Niño this year: The reef is ailed not by a rare climatic phenomenon but by the baseline warming of the oceans.
Until this decade, back-to-back bleaching events like that simply didn’t happen.
“It’s new. It is so new. It’s a complete change in the phenomenon that all of us study,” said Ruth Gates, a professor at the Hawaii Institute of Marine Biology and the president of the International Society for Reef Studies. “We knew that this day would come—we’ve been seeing the thermal-tolerance threshold for corals get closer and closer, and we knew it was pushing over the limit for coral survival.”
“There will now be years where it doesn’t take an El Niño event to reach the bleaching threshold. This is going to be statistically more likely in a warming world,” said Cobb.The intensity and duration of bleaching events is ultimately leading to a change in the study of coral reefs overall. Instead of focusing on reefs in situ, scientists are increasingly having to study how reefs recover from warming oceans and other forms of environmental disaster.“We are in a different moment with coral reefs right now. We’ve had this global insult on reefs. The choice now is to study recovery because that’s what we are doing, because that’s what we have to do,” said Gates.
The reef that Gates knows best—the coral reef in Kāne’ohe Bay, right next to the institute where she works—was one of the first in the world to suffer a back-to-back bleaching. In 2014, a warming Pacific pushed the Kāne’ohe Bay corals to warm; in 2015, the sea bleached them again. “We were not really expecting it to be a bleaching year then and we didn’t expect it to be a bleaching year the following year,” she told me.
Since then, she has been monitoring the health of the reef and watched it recover. Scientists still don’t know how repeated bleaching events—especially in back-to-back years—will affect the long-term health of a coral reef. Kāne’ohe Bay has recovered faster and more vigorously than Gates expected, but it is a considerably less biodiverse reef than the Great Barrier Reef. Much of Gates’ research focuses on expanding coral resilience between reefs. (There was a wonderful New Yorker profile on her work last year.)
Cobb, meanwhile, is organizing research into how Kirimati Island bounces back from the El Niño bleaching. Thankfully, Kirimati has been slightly cooler than normal over the last few months, and baby corals have already begun to sprout in the reef. “We’ll see in out years as a team of climate scientists, ecologists, and oceanographers focus on this island,” she told me. “We plan on witnessing its recovery in its various stages and trying to see how it differs from the reef that was there before this event.”This represents another major step forward for the field. When Gates started her doctoral research in the 1980s, scientists were still beginning to understand that coral bleaching can occur in the first place. Now, they know it is triggered in large part by temperature changes.The devastation to coral reefs will continue as climate change runs apace. The International Society for Reef Studies predicts that 90 percent of coral reefs worldwide will be at risk of destruction by 2050. (This stands out: Many really dire predictions of severe climate damage start after 2050.)
“We are just one species that are in line to be hit very heavily by climate change,” said Gates. “Coral reefs are in the front line but they’re telling us something very important.”