By Jeremy Williams

There is no hotter topic in today’s politics than migration. In the UK, debates around who is and who isn’t allowed to be in the country have fed into the historic self-sabotage of Brexit, and led to cruel policies such as exporting refugees to Rwanda. If policies are ugly now, it is troubling to contemplate how things might look in the coming decades as climate change drives growing numbers of people into moving.

Many things are often missing from popular debates on migration, including compassion and empathy. But we also misunderstand the idea of migration itself. In this intriguing book, American journalist Sonia Shah takes a broad look at movement – both human and non-human, and its role in shaping life on earth.

The book begins in search of migrating butterflies, in the company of scientist Camille Parmesan. She was the first to publish a study showing how climate change had shifted the distribution of a species northwards. It was the first of many of course. Thousands of species are now on the move, some faster, some slower, towards more habitable climes. Even plants. It is one of the most obvious and more natural forms of climate adaptation. “A wild exodus has begun,” writes Shah.

There’s a stark distinction between this wild exodus and human migration. A butterfly can cross a border. “The paths taken by human migrants, in contrast, are shaped by abstractions.” Borders, visas, citizenship, government policies. Green cards and quotas. Refugee status, rights.

Historically, this is a strange state of affairs. Life on earth has always moved. All human life can be traced back to East Africa, so we are all migrants at some point. Through archaeology and through genetics, the story can be told of who moved where, in what order – including the extraordinary settling of the Pacific Islands. People have always travelled and sought new opportunities. Migration has even shaped human evolution, as Shah explains. We are who we are, in all our diversity, because of the freedom to roam across the planet.

Populations being in flux has been normal, in the grand scheme of things. The idea that people and species ‘belong’ in certain places is a relatively novel idea. Shah explains where it came from. Racist pseudo-science attempted to draw lines around human sub-species, categorising and ordering people into hierarchies. Building on this work, eugenicists fought for immigration restrictions in order to protect the bloodlines of supposedly purer people. All sorts of abuses and prejudices ensued.

Conservation biology also fed into this, as scientists developed theories around habitats and sorted animals into native and non-native species, often missing migration entirely because it is hard to observe in the wild. This helped to embed the notion that the world is more or less fixed, and that migration is an anomaly – or even dangerous.

Another part of the story is environmentalist fears around over-population, Paul Ehrlich being the most prominent voice on the issue. In an eye-opening chapter, Shah details how racist theories around population moved from environmental circles to the right wing, ending up shaping immigration restrictions in the Trump administration.

Weaving together reportage, science and history, Shah shows how migration has been a life-saving “force of nature, rooted in human history and biology, along with that of the scores of other wild species with whom we share this changing planet.”

As the world warms and more places become challenging or even impossible to live in, our current attitude to migration closes the door to the most powerful solution. This is something we need to discuss, nationally and internationally, and The Next Great Migration is an engaging and informative background to the whole idea of life on the move.

First published in The Earthbound Report.