Over one thousand small islands in the Pacific and Indian Oceans will become uninhabitable sooner than scientists thought, according to new research. The study warns that sea-level rise and wave-driven flooding will force hundreds of thousands of people who currently inhabit these low-lying tropical islands from their homes in just a few decades.
The findings, published on Wednesday in the journal Science Advances, show that as sea level rises, large waves will break farther onto shore and contaminate freshwater sources used for drinking.
The research focussed on Roi-Namur Island on Kwajalein atoll in the Marshall Islands and was carried out by an international team of scientists, with members from the US Geological Survey (USGS), the Deltares Institute in the Netherlands, the US National Oceanic and Atmospheric Administration (NOAA) and Hawaii University.
Based on current greenhouse gas emission rates, sea-level rise and wave dynamics, researchers project that the combination of damage to infrastructure from flooding and the loss of drinking water sources would begin to make the islands difficult for humans to inhabit sometime between the 2030s to 2060s.
“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,” said Curt Storlazzi, USGS geologist and lead author of the study.
Most of the freshwater sources on populated atoll islands come from rainwater that soaks into the ground and then floats on top of denser saltwater.
“The overwash events generally result in salty ocean water seeping into the ground and contaminating the freshwater aquifer,” explained co-author Stephen Gingerich, a hydrologist at USGS. “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.”
While previous studies suggested these islands would not experience significant impacts from flooding until at least the end of the 21st century, they did not take into consideration the added effect of wave-driven overwash and its subsequent impacts on potable water, according to the authors of the new study.
“Such information is key to assess multiple hazards and prioritise efforts to reduce risk and increase the resiliency of atoll islands’ communities around the globe,” said Storlazzi.
“Historically, there would be an overwash event due to a cyclone or typhoon every 20 or 30 years,” Storlazzi told The Washington Post. “Every 20 or 30 years or more, communities can recover in that time. The concern is that with sea-level rise, those flooding events are going to happen more frequently.”
Hilda Heine, president of the Marshall Islands, told The Washington Post that the new report “brings home the seriousness” of the issues her island nation is preparing to face.
“It’s a scary scenario for us,” she said.
Although the research focussed on the Marshall Islands, the authors said their findings are relevant for atoll island communities around the world. The Caroline Islands, Cook Islands, Society Islands, Maldives, Seychelles, Northwestern Hawaiian Islands and others share similar features to the islands studied and have even lower land elevation on average.