Shah confesses to a certain kinship with those migrations. Shah joined the butterfly hunters marking that progress and along the way found evidence that myriad other species are also checking out of familiar territories: Atlantic cod, for example, are moving at a rate of 200km a decade toward the cooler poles. A celebrated paper in Nature in 1996 showed that in response to warming temperatures the edges of the population of checkerspots were moving northwards at a rate of 20km per decade. Because of its sensitivity to changes in habitat and environment, it also proved one of the first bellwethers of climate change. It flies very low to the ground and only lives for 10 days. The checkerspot, most abundant on the west coast of America, is not a powerful creature. The first concerns the habits and behaviour of the checkerspot butterfly. Shah begins her history with a series of observations that become parables from the natural world. “End freedom of movement!” “build the wall!” One billion! the NGO Christian Aid projected.” One result of those alarmist predictions had been the populist politics that has emerged with a single purpose in mind: how to make those people stay still. Two hundred million by 2050, the environmental security analyst Norman Myers announced.

“There would likely be 50 million on the move by 2020, experts at the United Nations University projected.

The “next great migration” has been predicted by many – and feared by some – ever since the end of the cold war. The national security expert Robert D Kaplan described it in a 1994 Atlantic magazine article as “the coming anarchy” – the binary superpowers had held borders mostly in check, now people would start to move.

Pandemic sonia shah sparknotes