The Effect of Global Warming on Tropical Islands “Is Not an Exact Science”: Many Islands Are Stable or Even Growing

Environmentalists warned for decades that the biggest threat from global warming is to the survival of small low-lying islands. But as the late great physicist Freeman Dyson observed, the earth is more resilient than we know. In the three-full-page article quoted below, The New York Times (yes, The New York Times) reports that the small low-lying islands are mostly doing just fine.

(p. A6) 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, probably in this century.

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.

. . .

(p. A7) 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,” Dr. 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. Whatever was going on, it clearly wasn’t as simple as oceans rise, islands wash away.

Dr. Webb and Dr. 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. Which is why Dr. Kench came back this spring to the Maldives.

On a blob of jungly land just a few miles north of the Equator, Dr. Kench walked past a section of beach that the currents had eaten away. Several palm trees lay toppled, half-buried in the sand.

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

SCIENCE AS ‘DETECTIVE WORK’

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 that, from above, gave the reef its streaky, ethereal look.

One doctoral researcher, Aitana Gea Neuhaus, scooped up a spadeful of sand and beheld the miniature universe it contained: puzzle-piece fragments of coral and calcareous algae in a mad variety of shapes and textures; crushed shells of bivalves, crustaceans and single-celled foraminifera; the sugar-white sand particles that parrotfish churn out of their digestive tracts.

. . .

One morning, Dr. Kench and a few other researchers hacked away a clearing in the jungle and bored a hole in the ground. Down went a six-foot steel pipe.

They were trying to glimpse the island’s deep past, to reconstruct its major chapters, layer by ancient layer. And they had some idea of how far below ground to look, thanks to seismic measurements that Tim Scott, an ocean scientist at Plymouth, had taken. Still, he warned the group: “It’s not an exact science.”

Dr. Scott sledgehammered the pipe down. “This is the moment of truth,” Dr. Kench said.

They levered out the pipe and hoisted it above a tarp. Out came a messy line of sediment and gravel and coral bits. Everyone leaned in close. No group of people in human history had ever seemed more interested in some chunks of damp sand.

Dr. Scott tried to puzzle out why the fine and rough material were jumbled together, not crisply layered as they’d hoped. Gerd Masselink, a coastal scientist at Plymouth, grinned. “Well, you know, it’s not an exact science,” he said.

. . .

On its own, coral bleaching isn’t necessarily bad for islands. When corals go white and frail, they can become infested (p. A8) by even more of the cyanobacteria that parrotfish love to munch on. The parrotfish flourish; they produce more sand.

. . .

It’s . . . less-populated islands where scientists say people can still learn to coexist with expanding and contracting shores, to adapt to nature’s give-and-take.

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.