It’s a sad but now familiar story. Earlier last month, the Global Coral Reef Monitoring Network released the first-ever report collating global statistics on corals, documenting the status of reefs across 12,000 sites in 73 countries over 40 years. Overall, they report, the world has lost 14 percent of its corals from 2009 to 2018—that’s about 11,700 square kilometers of coral wiped out.“If this had happened to the Amazon, if overnight it had turned white or black, it would be in the news everywhere,” says Voolstra. “Because it’s underwater, no one notices.”Corals are facing tough times from global warming: Prolonged marine heat waves, which are on the rise, cause corals to expel their symbiotic algae (called zooxanthellae), leaving the bleached corals weak and vulnerable. Local pollution continues to be a problem for corals, but global warming is emerging as the predominant threat. In 2018, the International Panel on Climate Change reported that 1.5 degrees Celsius of global warming would cause global coral reefs to decline by 70 to 90 percent (warming currently stands at 1.2 Celsius). A 2-degree Celsius warmer world would lose more than 99 percent of its corals.There are some hints of hope. The Global Coral Reef Monitoring Network report shows that corals can recover globally if given about a decade of reprieve from hot waters. Some spots—particularly the Coral Triangle in East Asia, which hosts nearly a third of global corals—have bucked the trend and seen coral growth. There are hints that corals might be adapting to warmer conditions. And research is burgeoning on creative ways to improve coral restoration, from selectively breeding super corals to spreading probiotics on stressed reefs.
“I’m hopeful,” says Voolstra. But it’s going to take a lot of quick action, he says, and even then we won’t be able to save all reefs. “That’s impossible. The point is you save some reefs so they can go through the dark ages of climate change.”From 1978, when the Global Coral Reef Monitoring Network’s data collection began, hard coral on the world’s reefs held relatively steady for decades. That changed dramatically in 1998 with the first global mass bleaching event. Warm waters around the world, caused in large part by a powerful El Niño, wiped out about 8 percent of living coral globally, equivalent to a grand total of 6,500 square kilometers. “All the drama started in 1998,” says David Souter, coordinator of the Global Coral Reef Monitoring Network and a researcher at the Australian Institute of Marine Science in Townsville. “Corals are actually pretty good at sustaining short, sharp temperature increases, but when it starts to last months, we see real issues.”