The coral reefs that offer hope
After years of doom and gloom, scientists discover some good news underwater
These are not fun times to be a coralreef researcher.
Like so much of environmental science, the field can be a dismal one, often devoted to documenting decline. There are mass die-offs, worldwide bleaching events, plagues of sea stars, the ominous “warm blob,” the “godzilla” El Nino and devastating oil slicks. Not to mention the everlooming threat of climate change.
“In the coral reef world, the situation can seem dire a lot of the time,” Julia Baum, a marine biologist at the University of Victoria in B.C., told the Washington Post last year.
Which is why the discovery that some pristine reefs still exist near the uninhabited islands in the Pacific brought ecologist Jennifer Smith so much joy.
“It’s hard to fathom,” Smith, the lead author of a sweeping 10-year evaluation of central Pacific reefs, told the Post. “I would jump into the water and there would be so much coral, so many different species of fish, so much complexity and colour.”
For Smith and her colleagues — their senses dulled by years of working in dying and degraded ecosystems — it was almost “a religious experience.” The scientists were very nearly moved to tears.
“I would find myself underwater, shaking my head, looking around in disbelief that these places still existed,” Smith said.
Smith’s report, which was published recently in the journal Proceedings of the Royal Society B, examined reefs at 450 sites spanning the Pacific from Hawaii to American Samoa. The researchers wanted to determine how the reefs responded to climate change and a 1998 El Nino event that led to widespread bleaching (a phenomenon in which stressed coral banish the symbiotic algae that give them their brilliant colours).
Some of the findings were the same, grim statistics so familiar to coral researchers. Most of the reefs around inhabited islands had been colonized by smothering macroalgae and fleshy algae — big seaweeds whose growth was likely spurred by the absence of fish (nature’s lawn mowers) and the presence of fertilizer runoff in the water. These reefs were less complex, less colourful, less developed — a monotonous suburban subdivision to a healthy reef’s thriving city.
But another discovery surprised them. If the reefs existed around uninhabited islands — away from localized problems such as overfishing and pollution — they were often able to bounce back from global stressors relatively unscathed
“Going to these uninhabited locations, you can still find reefs that look the way they did 1,000 years ago,” Smith said.
Because the researchers had no baseline measure of the reefs’ wellbeing, they can’t say for sure whether the reefs near inhabited islands were always dominated by seaweed. It’s possible that the presence of macroalgae is just a natural outcome of their environment.
But if their arrival is a more recent change spurred by human interference, which seems likely, those habitats “may be losing . . . one of the most significant ecological services that they are known for, their capac- ity to build carbonate reefs,” the authors write. That’s because a reef is not just a reef. The calcium carbonate skeletons and the tiny creatures that constitute them provide the foundation for a habitat that is home to a quarter of all marine life, even though coral cover just 2 per cent of the ocean bottom. Their global contribution to fisheries, tourism, medicine, even shoreline protection, is estimated by the National Oceanic and Atmospheric Administration (NOAA) to be in the vicinity of $30 billion (U.S.) per year.
According to NOAA, a host of problems threatens to destroy some 45 per cent of reefs in the next 20 to 40 years. Many of those threats are global: Climate change makes the oceans warmer, more acidic and less hospitable to coral regardless of how far they are from the closest human.
But Smith’s findings suggest that reefs may be able to survive that menace if they are sufficiently insulated from human activity. Which, by the relatively low standards of often-grim coral research, is great news.
“It gives us incentive and motivation to believe that by managing these local impacts we can build a healthier reef ecosystem,” Smith said. “Warming events, El Nino — they’re impending. But the remote reefs show that if we can build these living organisms to be as healthy as they can be, they’re going to be much more likely to recover.”