September 10, 2018 — RAROTONGA, Cook Islands — Twenty-one degrees, 12 minutes south of the equator, 2,771 miles south-southeast of the southern tip of the island of Hawaii, 30 feet below 4-foot swells, Nicole Pedersen swims slowly, wearing a wetsuit, headband, and full scuba gear and carrying a custom-built plexiglass-and-PVC case the size of a tackle box. Within it, twin DSLR cameras automatically photograph a reef a quarter-mile off the coast of Rarotonga. It’s the last of 12 dives she and colleagues from the Scripps Institution of Oceanography have made over three days of their research expedition here.

Pedersen, 25, is a staff researcher at Scripps, part of the University of California, San Diego, and the image digitization coordinator for a natural experiment called the 100 Island Challenge, launched in the summer of 2016. The images she’s gathering—4 billion pixels comprising 70 to 80 gigabytes of data, just from today—will ultimately help the team build a three-dimensional model of the 100-square-meter (1,076-square-foot) plot of reef Pedersen is swimming over in a lawn mower pattern.

As she gently flaps her black-and-yellow fins, maintaining as constant a speed as is possible underwater where waves and currents can toss her off course, marine ecologists Stuart Sandin and Brian Zgliczynski swim alongside her, counting every fish in the plot and marking on a waterproof data sheet each one’s species and approximate size. The more than 4,000 dives the team will make over five years are the data-collection component of an unprecedented attempt to characterize five examples of every type of reef on the planet—twice—to see how each is responding to climate change, ocean acidification, pollution, overfishing, and the other insults humans have been throwing at many of them with increasing frequency and intensity over the last few decades.

The 100 Island Challenge is so wildly ambitious that even one of its co-leaders, Scripps coral reef ecologist Jennifer Smith, thought it would be absurd to try when Sandin, the project’s lead investigator, and Zgliczynski, a postdoctoral researcher, pitched it to her several years ago. “You guys are idiots,” Zgliczynski says she told them.

Over a dinner of wahoo fillets and Cooks Lager, the local brew, following the first day of diving in Rarotonga, the scientists say they could already see that the island’s reefs, alive with new growth of diverse coral species and crowded with fish scraping away excess algae, are not like those that have dominated the news lately. “Coral reefs are bleaching four times as frequently as they did in the 1980s, scientists say,” read a Washington Postheadline in January. “Coral Reefs at ‘Make or Break Point’, UN Environment Head Says,” blared another January story in The Guardian. “Coral reefs at risk of dissolving as oceans get more acidic,” announced Reuters in February.

Unchecked coastal development pollutes reefs; illegal, unreported, and unmonitored fishing depletes them; carbon dioxide emissions inhibit their ability to grow; and historic ocean warming has in recent years caused back-to-back bleaching events that threatened reefs worldwide, including potentially as much as half of the Great Barrier Reef’s northern corals. Still, although the bad news is undeniable, it’s not the only story. “And it’s not the story when communities take control of their marine ecosystem,” Sandin says. “When a community is engaged and listens to what’s underwater, they can keep it going.”

Read the full story at Scientific American