The vanishing islands that failed to vanish

DHIGULAABADHOO, Maldives — On a wisp of land in the Indian Ocean, two hops by plane and one bumpy speedboat ride from the nearest continent, the sublime blue waves lapping at the bone-white sand are just about all that breaks the stillness of a hot, windless afternoon.

The very existence of low-slung tropical islands seems improbable, a glitch. A nearly seamless meeting of land and sea, peeking up like an illusion above the violent oceanic expanse, they are among the most marginal environments humans have ever called home.

And indeed, when the world began paying attention to global warming decades ago, these islands, which form atop coral reefs in clusters called atolls, were quickly identified as some of the first places climate change might ravage in their entirety. As the ice caps melted and the seas crept higher, these accidents of geologic history were bound to be corrected and the tiny islands returned to watery oblivion.

Then, not very long ago, researchers began sifting through aerial images and found something startling. They looked at a couple dozen islands first, then several hundred, and by now close to 1,000. They found that over the past few decades, the islands’ edges had wobbled this way and that, eroding here, building there. By and large, though, their area hadn’t shrunk. In some cases, it was the opposite: They grew. The seas rose, and the islands expanded with them.

Scientists have come to understand some but not all of the reasons for this. Which is why a team of them recently converged in the Maldives, on an island they’d spend weeks outfitting with instruments and sensors and cameras.

They were there to learn more about how the steady collision of blue waves and white sand does surprising and seemingly magical things to coastlines, both destroying land and extending it. Really, though, they were trying to answer a bigger question: If atoll nations aren’t facing certain and imminent erasure, then what are they facing? For having a future is not the same thing as having a secure future.

If, for instance, some of their islands become difficult to live on but others do not, then atoll governments will have to make hard choices about which places to save and which to sacrifice. In the places they save, they will have to plan for the long term about supplying fresh water, about creating jobs, about providing infrastructure. They will have to invent the best future they can with the limited resources they have.

In short, atolls might not be such outliers in this world after all. Look hard enough, and they start to look a lot like everywhere else.

Swaying palms, unspoiled beaches and abundant sunshine are the main draws for most visitors to atolls. Not for scientists. No, to understand what really beguiles them about these islands, you need to take a dive into the surrounding sea. Or you need to gaze down from a plane. Or, for the very best view of all, you should really find a way to peer back into the past.

There, you would see the island volcanoes that once stood in the atolls’ place. Fast-forward a bit, enough to let the tectonic plates shift, and you would see the volcanoes start to cool and subside. As they sank, corals would colonize their flanks, growing higher and higher. In time, the volcanoes would be no more and all you’d see was the ringlike reefs, each one encircling a lagoon. Where the reefs poked up high enough, wind and waves would toss up sand and rubble, forming slender islets.

“Such formations surely rank high amongst the wonderful objects of this world,” Charles Darwin wrote in 1836 after visiting an Indian Ocean atoll during his voyage on the Beagle.

It was Darwin who first theorized that atolls were burial sites for dead volcanoes, that these modest, almost shy, formations had astonishing pasts. Only later did scientists discover a key piece of their more recent history: Swings in sea level, they realized, had drowned and exposed the islands several times through the ages. Which didn’t bode particularly well for them today, now that global warming was causing the oceans’ rise to speed up.

To understand what had happened to the atolls since this acceleration began, two researchers, Arthur Webb and Paul Kench, decided to look down at them from above. The scientists collected aerial photos of 27 Pacific islands from the middle of the 20th century. Then, they compared them to recent satellite images. “I’m not sure we really knew what we would find,” Kench recalled.

Their findings caused an uproar.

The seas had risen an inch or so each decade, yet the waves had kept piling sediment on the islands’ shores, enough to mean that most of them hadn’t changed much in size. Their position on the reef might have shifted. Their shape might be different. It clearly wasn’t as simple as oceans rise, islands wash away.

Webb and Kench’s study, which came out in 2010, inspired other scientists to hunt for more old photos and conduct further analysis. The patterns they’ve uncovered in recent years are remarkably consistent across the 1,000 or so islands they’ve studied: Some shrank, others grew. Many, however, were stable. These studies have also added to the intrigue by revealing another pattern: Islands in ocean regions where sea level rise is fastest generally haven’t eroded more than those elsewhere.

And yet, to really grasp the forces at work, and to anticipate what they might do to the islands next, scientists also need to study atolls up close. On a blob of jungly land just a few miles north of the equator, Kench walked past a section of beach that the currents had eaten away.

“People obsess on that end of the island,” he said. Then he pointed up ahead. “This side has got bigger.”

The day before, another island in the same atoll was abuzz with activity. One group of scientists and graduate students measured currents using makeshift buoys. Another group fiddled with a tower-mounted sensor that mapped the waves running up the beach. A third team dove down to the seafloor, where they installed instruments within the intricate coral canyons.

The researchers were hoping all this data from the island, Dhigulaabadhoo, would help them see the future. Only with hard numbers can you start projecting island change going forward, said Kench, who teaches at the National University of Singapore. “That’s the holy grail.”

Among scientists who study islands and coasts, the most common advice for dealing with sea level rise can sound a lot like doing nothing. Coexistence, to use Kench’s word, means accepting that the mighty ocean will do what it will and learning to live with it. It means planning smartly around the water rather than trying to keep it away with expensive engineering projects, which carry their own environmental side effects.

And yet, to the man who actually decides how the Maldives deals with sea level rise, welcoming the water would be just as unacceptable as doing nothing.

“If there’s coastal erosion, then we have to do something about it,” the country’s environment minister, Thoriq Ibrahim, said. “We can’t just leave it, thinking that nature will expand the island.”

The issue is whether people can wait. Whether their needs for modern services, for better lives, will lead them to demand sea walls and breakwaters and land reclamation, the very things that could diminish the islands’ natural resilience. Or whether they will simply leave.

If the atolls’ near future is written in their recent past, then we can foretell it: Some islands will shrink, others will grow. Many will be stable. But which of these places people will actually want to call home is the harder question, a question that every country confronts in one form or another, a question as eternal as the tides.