"Taken together, the many factors that influence global immigration make it a huge and unwieldy thing to predict. No one knows exactly how many people will be uprooted thanks in part to climate change; estimates range from 50 million to as high as one billion. It’s also challenging to predict which regions will be hardest hit, but places already struggling with drought and flooding “will see their problems increase,” Bradatan says. Southeast Asia, the Amazon Basin, and a lot of Africa are all vulnerable. Coastal areas and small island countries will face major displacement, too, experts say, as sea levels rise. In the Pacific islands of Kiribati and Tuvalu, for example, more than 70 percent of households say they’ll probably move if the climate worsens."