Majuro Atoll in the Marshall Islands
Photo: AP

In a matter of decades—not centuries—most atoll islands, low-lying islands that emerge around coral reefs, could become uninhabitable. These thousands of tiny islands scattered throughout the Pacific, which are home to more than 50,000 people, are at severe risk due to sea level rise and, as a new study details, wave-driven flooding.

Published in the journal Science Advances Wednesday, the Department of Defense-funded study found that Pacific Islanders living today will have to deal with the consequences of human-caused climate change. Not their children or children’s children, as some scientists believed previously.

“When we start talking about decades, we’re talking about current inhabitants’ lifetimes,” said Curt Storlazzi, the lead author of the study and research geologist with the U.S. Geological Survey’s (USGS) Pacific Coastal and Marine Science Center, to Earther.

This study, spearheaded by a team from the USGS, looked at one island in particular from November 2013 to May 2015: Roi-Namur Island on the Kwajalein Atoll in the Marshall Islands. The team decided on this island because “it recently experienced wave-driven marine flooding,” per the study. The thing about these waves is that they not only flood people’s homes and destroy them. The saltwater that rushes in during these events can also seep into the groundwater islanders rely on for drinking.

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The paper refers to wave-driven floods as periods of overwash. And, well, they’re no good. During the study period, the island’s groundwater saw its salinity levels increase as a result of overwash events. And when the researchers used climate models to forecast how much rising temperatures and rising sea levels will impact overwash events, the result wasn’t any good, either.

Without the wave-driven flooding (the way most studies prior to this have looked at the impacts of climate change on atolls), the island of Roi is safe from inundation until the end of the 21st century. Add in that wave-driven flooding, which is slated to occur more often with higher sea levels, and the thin piece of land that connects Roi to Namor will see regular annual floods that’ll hurt the area’s infrastructure much sooner.

With these events happening so regularly, the freshwater supply won’t have a chance to bounce back to normal. It’ll become saltier—and, eventually, it’ll be gone. The new study projects this to happen within the lifespan of the island’s current residents. Different carbon emissions scenarios give different years, but it could be as soon as 2030, or as late as 2065. Either situation is still too soon.

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While the study looked only at the Roi-Namur Island, its results are easily relevant to most other atoll islands across the tropics. They’re all susceptible to the same threats, some even more so because their options to manage their groundwater are much more limited, according to the study.

The Department of Defense directed Storlazzi and his team to understand what islands are at risk so that the United States can more effectively help plan mitigation or relocation efforts. “We’re trying to save dollars and lives and provide guidance to do just that,” he said.

The problem is, mitigation and relocation cost money. And the GDP of the Marshall Islands, for example, is only $183 million. (The U.S., in comparison, is $18 trillion.) How will a lower-income nation like that afford to keep its residents on these islands?

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Aerial photograph of Kwajalein Atoll showing its low-lying islands and coral reefs.
Photo: Thomas Reiss (Pacific Coastal and Marine Science Center)

What really sucks is people living on these coral atolls have only contributed a small fraction of the fossil carbon emissions driving climate change. They’re just living their lives, but the ocean is knocking at their front doors.

Storlazzi doesn’t expect these islands to completely drown and disappear. The study didn’t take a look at how the land masses would evolve in the face of sea level rise, but knowing that could help these nations plan better for their futures. There’s more research to do, and more hope to hold onto.

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What we have less of, now, is time.