Thousands of islands in the equatorial Pacific Ocean sit mere meters above sea level. And climate change may make atolls and other low-lying islands uninhabitable as soon as 2030, according to a new study in Science Advances. Rising water could inundate the islands, but the more urgent threat is large waves that crash far onto shore, contaminating groundwater—often the sole freshwater source for inhabitants—with saltwater. How long residents have until their homes become unlivable depends on how fast the climate changes, The Washington Post reports. A more moderate—and perhaps more probable—prediction from the model suggests such a threat won't arrive to the endangered islands until 2055.