Last week was a sad one for the planet, but buried beneath headlines of the history’s largest carbon polluter telling everyone else to piss off, a team of researchers issued a more hopeful message: Coral reefs, a poster child for impacts of climate change, may not be as doomed as we think.
It’s no secret that coral reefs are in bad shape, nor that pollution, overfishing, development, and rising temperatures—in short, humans—are to blame. With overheated ocean waters cooking reefs year after year, scientists have issued dire warnings that these ecosystems might not survive the century. But now, a team led by coral reef experts at James Cook University—the same ones who first raised the alarm about the plight of the Great Barrier Reef last year—are adopting a less apocalyptic tone. The reefs aren’t doomed yet, the researchers wrote in Nature last week, but we need aggressive conservation strategies in order to save them. And we need to accept that the pristine reefs of the past are no more.
“We’re not driving the gloom and doom message that they’ll all be dead by 2030,” lead study author Terry Hughes of the ARC Centre of Excellence for Coral Reef Studies told Gizmodo. “But it’s also a dose of realism in that we’re saying the reefs of 30 years ago will continue to shift, and attempts to get back to where we were are not going [to work].”
Although they cover less than one percent of the seafloor, coral reefs are bastions of biodiversity, sheltering a quarter to a third of all marine species. Reefs are also incredibly important to humans, supporting fishing and tourism industries, and providing ecosystem services from water purification to carbon sequestration, whose total value has been estimated at a staggering $172 billion.
But today, overfishing, ship traffic, pollution and climate change have created a crisis for these delicate ecosystems. For the past three years, this crisis has manifested visibly, as reefs around the globe have suffered the longest, most widespread, and most damaging coral bleaching event on record. The Great Barrier Reef is being hit especially hard, with an estimated 29 percent of its shallow water corals dying from bleaching in 2016, according to the Australian government. More coral die-off is expected this year as elevated ocean temperatures cause corals to expel the algae they depend on for food, turn ghostly white, and starve.
“We’re saying the reefs of 30 years ago will continue to shift, and attempts to get back to where we were are not going [to work].”
The situation is so bad that some scientists, and many more in the media, have declared that the Great Barrier Reef all but dead already.
But as Hughes and colleagues explore in their paper, this alarmist talk masks a more complex—and hopeful—reality. For instance, while the colorful, branching Acropora corals that dominate the northern Great Barrier Reef have been hit hard by bleaching, slower growing, dome-shaped corals appear resilient. Corals are diverse organisms with a range of environmental tolerances, and as temperatures rise, we can expect natural selection to favor those that can take the heat. In fact, scientists are already observing changes at the genetic level that appear to be associated with heat tolerance in certain species.
“Bleaching is not random—there are winners and losers,” Hughes said. “And within each species, there’s inevitably going to be rapid selection for those that are tougher.”
And while rising temperatures are generally considered a bad thing for reefs, a warmer world could cause the habitat range of certain corals to expand north and south of the equator. In the short term, range expansion may even help offset another climate-related threat: ocean acidification. In reality, Hughes and his colleagues write, it’s hard to know how the effects of rising temperatures and rising acidity will impact corals over the next few decades, because laboratory experiments typically simulate much more extreme environmental changes—ones that we’ve still got time to avoid.