Study: Remote coral reefs thrive despite climate change

Lionfish, like this one spotted in the Bahamas, are a carnivorous, non-native predatory fish that damage coral reefs and can decimate native fish populations. (Cammy Clark/Miami Herald/MCT)
Lionfish, like this one spotted in the Bahamas, are a carnivorous, non-native predatory fish that damage coral reefs and can decimate native fish populations. (Cammy Clark/Miami Herald/MCT) MCT

SAN DIEGO--As ocean warming continues to trigger widespread destruction of coral reefs, a decade-long study of remote islands in the Central Pacific suggests these biodiversity hotspots may be able to thrive despite the threats posed by an increasingly hotter planet.

With many parts of the globe in the grip of a nearly two-year coral reef bleaching event -- fueled in part by El Nino-driven ocean warming -- scientists and marine conservation advocates have feared many reefs could suffer irreparable damage and fade from existence in coming decades.

A new report from UC San Diego's Scripps Institution of Oceanography provides reason for optimism by highlighting the potential for preservation efforts. In a massive project spanning 56 islands, researchers documented 450 coral reef locations from Hawaii to American Samoa, with stops in the remote Line and Phoenix islands as well as the Mariana Archipelago.

The results -- published in the journal Proceedings of the Royal Society B -- show that coral reefs surrounding remote islands were dramatically healthier than those in populated areas that were subject to a variety of human impacts.

"There are still coral reefs on this planet that are incredibly healthy and probably look the way they did 1,000 years ago," said Jennifer Smith, lead author of the study and a professor at Scripps' Center for Marine Biodiversity and Conservation.

"The scientists were practically in tears when we saw some of these reefs," she added. "We've never experienced anything like it in our lives. It was an almost religious experience."

Teeming with sharks, manta rays, jellyfish and sea turtles, these remote locations contrasted starkly with the heavily populated areas, which were encircled by coral reefs covered in murky seaweed and lacking much of the colorful algae that helps to cement a reef.

"All of these islands have reefs surrounding them," Smith said. "It's just what's growing on them. On the inhabited islands, you have some corals here and there, but most of those corals are being smothered by these weedy seaweeds."

In recent decades, coral reef ecosystems worldwide have suffered significantly from overfishing, coastal development and dumping of toxic substances into ocean waters. Scientists have predicted that up to 70 percent of coral reefs could be lost by mid-century.

Occupying less than one-tenth of 1 percent of the ocean's sea floor, coral reefs are estimated to be home to nearly a quarter of all marine species. They also provide several human benefits, including food, tourism and flood protection for coastline developments.

The new study will hopefully catalyze coral reef preservation efforts, which some have viewed as futile, said Stephanie Wear, senior scientist for the coral reef conservation program at the Nature Conservancy.

"I think it can energize people who are responsible for managing (reefs) that what they're doing really does matter," she said. "There are certainly people out there who have said, 'There's no point; climate change is going to be the end of reefs,' and I absolutely disagree with that."

Still, localized efforts to safeguard coral reefs will likely only stave off the worst impacts of global warming for so long, said Nancy Knowlton, a coral reef biologist and holder of the Smithsonian Institution's Sant Chair for Marine Science.

"The question is, how long will reefs be able to stay healthy in the context of much more frequent warming events and ocean acidification?" said Knowlton, who previously worked at Scripps and participated in the coral reef project's initial research. "I think most reef scientists will say there are limits.

"What this study shows is that protection in a variety of different ways buys us incredibly valuable time while we figure out how to deal with the threat posed by climate change," she added.