Despite Sea Level Rise, Some Small Islands Are Expanding

Wave-driven flooding and overwash on Roi-Namur Atoll, Republic of the Marshall Islands    Photo: Peter Swarzenski, U.S.G.S.

Researchers studying climate change have found that despite sea-levels rising, some islands are growing faster and are able to stay ahead of the ocean.  Atolls — islands that are situated within rings of coral reefs — are formed by sediments shed by the reefs around them.  Scientists believe that many atolls in the Pacific will disappear in the decades to come because of sea-level rise.  The team of researchers, who compared aerial photos of certain atolls, was surprised to find that at least some atolls are still increasing their landmass.  The researchers focused on Jeh Island in the Marshall Islands, where even though sea levels have risen by 0.3 inches a year since 1993, the island had increased in size by 13 percent, with two separate islands merging.

Why This Matters:  This research, funded in part by the U.S. Geological Survey, shows that natural systems can adapt in the face of momentous changes — the sea level at Jeh Island is rising much more each year than in most parts of the world.  As one of the authors of the study explained, “We have found islands are resilient in the face of rising seas and that sediment supply to some atolls is out-pacing sea level rise. What we don’t know is how that will play out in coming decades.”

Previous research

Pacific Island nations are acknowledged to be particularly at risk due to climate change. For example, a recent 2018 US Geological Survey study found that many low-lying atolls will be uninhabitable by 2050. Moreover, the Asian Development Bank president Takehiko Nakao said “the four atoll nations — the Marshall Islands, Tuvalu, Kiribati, and the Maldives, which are together home to more than half a million people — were the most vulnerable on the planet to climate change.”  But, according to CNN, a number of studies in the last 10 years have shown atolls increasing in size. For example, a 2018 study of 30 Pacific and Indian Ocean atolls, including 709 islands, found that no atoll had lost land area. More than 88% of islands were either stable or increased in area, according to the study. And climate change is still a problem for atolls and their residents — sea level rise causes other threats like more frequent flooding that could deteriorate freshwater reserves and make atolls uninhabitable, as well as tides that could also cause coastal erosion.

New Sedimentation

The researchers also used sediment samples to determine that much of the new sediment that caused the island to grow was added after 1950. “This is the first time we can see the islands form, and we can say the stuff making that island is modern … so it must be coming from the reef around the island,” one of the study’s authors told CNN. “It’s entirely the skeletons of the reef and the organisms that live on it.”

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