The heat wave that began in Hawaii in 2014 reached the Great Barrier Reef in 2016, producing another global bleaching event. By the time it ended, the following year, more than ninety percent of the Great Barrier Reef had been affected and something like half its corals had perished. Fast-growing species were particularly hard-hit; they suffered what researchers termed a “catastrophic” collapse. Terry Hughes, a coral biologist at Australia’s James Cook University, took an aerial survey of the damage and showed it to his students. “And then we wept,” he tweeted.
