An "unprecedented" bleaching event struck the Great Barrier Reef in 2016, with perilously high temperatures affecting the 1,400-mile-long stretch of coral. The Atlantic notes we already knew that this occurred, but that the toll is just now being fully understood: It describes a new study published in the journal Nature as "a kind of autopsy report for the debacle." A team led by Terry Hughes, the head of the ARC Centre of Excellence for Coral Reef Studies, examined the "catastrophic die-off" more closely to establish links between high levels of heat exposure, the resulting coral bleaching, and how well the coral ultimately withstood it. The upshot isn't good: About a third of the world's largest reef system succumbed to the "mass mortality" between March and November that year, per the Guardian.
The Los Angeles Times notes a second heat wave in 2017 exacerbated things, with both events leading to the destruction of about half the Great Barrier Reef's coral. The researchers found that coral in areas where the heat exposure was greatest experienced the biggest die-offs. (Per the New York Times, it only takes a spike of two or three degrees Fahrenheit above normal to decimate the coral.) Another shocker: About half the coral destroyed in 2016 didn't gradually die from starvation, as scientists believed would happen, but instead went south "very quickly" from heat stress, taking only a few weeks to perish. Hughes says he's trying to keep a "glass half full" outlook, noting that the billion corals that did endure are more resilient than their unfortunate counterparts. Still, if we can't keep the heat under control, it's "game over," he says. (Australia will feel a "profound" impact from this loss.)