About 80 percent of Tumaco's people live on or alongside the water, where they are highly vulnerable to any changes in the climate or water levels. The flooding in recent years has caught many of the locals by surprise. Tom Gjelten/NPR hide caption

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A U.S. Army helicopter flies over the snow-capped Hindu Kush mountains of Afghanistan in this 2002 photo. U.S. security analysts are trying to develop a set of early warning signs that could suggest which countries are in most danger of being destabilized as a result of dramatic climate changes. Joe Raedle/Getty Images hide caption

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