According to new research, many atolls could become uninhabitable by the middle of the 21st century as sea levels continue to rise and coastal flooding becomes significantly worse. The study, published in Science Advances, has found that flooding will impact terrestrial infrastructure and limit access to fresh water, making it unlikely that these places will sustain their populations long term.
Sea levels are rising at the highest rate in the tropics where thousands of low-lying coral atoll islands are located. The scientists conducted their analysis on Roi-Namur Island, which is part of Kwajalein Atoll in the Republic of the Marshall Islands, from November 2013 to May 2015. The team concluded that the lives and livelihoods of hundreds of thousands of people in the Marshall Islands are at risk.
Previous studies have estimated that atoll islands will be in grave danger later than the 2050s, closer to the end of the century. But those models didn’t take surge storms into account. This additional hazard has a big impact on the availability of fresh water, simply because wave-driven overwash contaminates the water reservoirs on these islands.
"The tipping point when potable groundwater on the majority of atoll islands will be unavailable is projected to be reached no later than the middle of the 21st century," lead author Curt Storlazzi, from the US Geological Survey (USGS), said in a statement. "Such information is key to assess multiple hazards and prioritize efforts to reduce risk and increase the resiliency of atoll islands' communities around the globe."
The team claims that these findings apply beyond the Marshall Islands. Atolls such as those in the Maldives, Seychelles, Northwestern Hawaiian Islands, Caroline Islands, Cook Islands, Gilbert Islands, Line Islands, Society Islands, and the Spratly Islands are also at risk.
At current levels of greenhouse gas emissions, the team expects events where overwash contaminates potable water resources to occur annually. Between damages to infrastructure and scarcity of drinking water, it is likely that these islands will have to be abandoned.
"The overwash events generally result in salty ocean water seeping into the ground and contaminating the freshwater aquifer," explained Stephen Gingerich, USGS hydrologist and co-author of the new report. "Rainfall later in the year is not enough to flush out the saltwater and refresh the island's water supply before the next year's storms arrive repeating the overwash events."
Communities worldwide have already been affected by global warming and migration from those regions is becoming more common. International cooperation and action are crucial to reduce the number of people affected and provide help when necessary.
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