THE NEXT GREAT MIGRATION

Science journalist Shah looks at the biology and human ecology of migration, a topic overladen these days with all sorts of political shadings.

The child of Indian immigrants, Shah—author of the excellent and ever more timely book Pandemic (2016)—returns with an incisive examination of migration, which she considers a phenomenon both biological and cultural. Many bird species, for example, travel great distances in annual migrations, and a delicate butterfly species with which the author opens her narrative exhibits “a consistent pattern of movement across half of North America.” We have been taught to view such movement as potentially perilous: Invading species arrive, we think, and immediately disturb pristine ecosystems. Even Shah admits that “the idea of migration as a disruptive force has fueled my own work as a journalist.” Yet nothing could be more natural than animals moving in response to changes in environmental conditions. As the author shows, only a tiny fraction of relocated species displace others, an act that is consistent with Darwinian theories of natural selection. “Condemning newcomers as inevitably disruptive,” she writes, pointedly, “blames them for all transgressions committed by 1 percent or less of their members.” When it comes to humans, she writes, the topic becomes more fraught. In a time when humans are increasingly on the move, whether because of political or economic displacement or because their homes are becoming uninhabitable thanks to climate change, politicians such as Donald Trump are using the tiny number of problem-makers, real or potential, to keep the vast majority of law-abiding would-be citizens from making their homes in new lands. This ignores millennia of human movement from one place to the next. Even though “over the long history of life on earth, [migration’s] benefits have outweighed its costs,” nationalists still create xenophobic, incoherent policies, agreeing only that strangers are to be despised.

A scientifically sophisticated, well-considered contribution to the literature of movement and environmental change.