A Surprising Climate Find

We humans have settled in all sorts of precarious environments: parched deserts, barren tundra, high mountains. None are precarious in quite the same way as atolls, the tiny, low-lying islands that dot the tropics. As the planet warms and the oceans rise, atoll nations like the Maldives, the Marshall Islands and Tuvalu have seemed doomed to vanish, like the mythical Atlantis, into watery oblivion.

Of late, though, scientists have begun telling a surprising new story about these islands. By comparing mid-20th century aerial photos with recent satellite images, they’ve been able to see how the islands have evolved over time. What they found is startling: Even though sea levels have risen, many islands haven’t shrunk. Most, in fact, have been stable. Some have even grown.

One study that rounded up scientists’ data on 709 islands across the Pacific and Indian Oceans showed that nearly 89 percent either had increased in area or hadn’t changed much in recent decades. Only 11 percent had contracted.

To understand why, I spent time this past spring with a team of researchers in the Maldives as they collected data on two key pieces of the puzzle: ocean currents and sand.

Currents and waves can erode sandy shorelines, of course. But they can also bring fresh sand ashore from the surrounding coral reefs, where the remains of corals, algae, crustaceans and other organisms are constantly being crushed into new sediment. (Another source of sediment? Colorful parrotfish, which munch on coral and churn out white sand from their digestive tracts.)