Climate change is not equally felt across the globe, and neither are its longer term consequences. This map overlays human turmoil — represented here by United Nations data on nearly 64 million “persons of concern,” whose numbers have tripled since 2005 — with climate turmoil, represented by data from NASA’s Common Sense Climate Index. The correlation is striking. Climate change is a threat multiplier: It contributes to economic and political instability and also worsens the effects. It propels sudden-onset disasters like floods and storms and slow-onset disasters like drought and desertification; those disasters contribute to failed crops, famine and overcrowded urban centers; those crises inflame political unrest and worsen the impacts of war, which leads to even more displacement. There is no internationally recognized legal definition for “environmental migrants” or “climate refugees,” so there is no formal reckoning of how many have left their homes because climate change has made their lives or livelihoods untenable. In a 2010 Gallup World Poll, though, about 12 percent of respondents — representing a total of 500 million adults — said severe environmental problems would require them to move within the next five years.

1. Amazon Basin

As glacial melting reduces freshwater reserves for the Andean plain, tensions are growing between locals and the mining and agribusiness operations that consume much of what remains. Researchers predict that this resource conflict will drive more migrants to the Amazon Basin where many have already turned to informal mining and coca cultivation, fueling the rise of criminal syndicates.