The news today is full of stories of dislocated people on the move, provoking fears of the spread of disease and conflict and waves of anxiety across the Western world, and countries respond by electing anti-immigration leaders who slam closed borders that were historically open. But the science and history of migration in animals, plants, and humans tell a different story, argues Sonia Shah, who frames the phenomenon as a lifesaving response to environmental change. Tracing centuries of mankind on the move, Shah offers here a "provocative invitation to imagine the inevitable migration of the future as an opportunity, rather than a threat" (Washington Post).