SO vile is the anti-migrant rhetoric currently bubbling from the mouths of media populists and political chancers that it’s easy to be attracted to the very opposite view.

To wit: migrants always add value, worth and innovation to the territories they land in. Migration is the default mode of humanity, the largest part of our evolutionary heritage. The countries which embrace the inevitability that climate meltdown will drive the peoples of the south to the north will be those that survive and prosper.

This is the brilliance of Gaia Vince’s Nomad Century: How To Survive The Climate Upheaval, correctly receiving many rave reviews. To read it is a real act of futurism. It lays out a concrete vision of how many of our core values and practices have to change, faced with grand and implacable tendencies.

The book also, by implication, shows how a coming independent Scotland that welcomes migrants – the current rhetoric of our stateless state – will be in the global vanguard of these challenges. More on that later.

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Firstly, the big numbers. Here’s what the weird stupidity of Farage, Braverman and co wilfully denies. Vince shows research which anticipates that, at 4 degrees warming by the end of the century, 3.5 billion people will be fleeing their now uninhabitable homelands.

The UN’s International Organisation for Migration estimates there could be 1.5bn environmental migrants by 2050. The Met Office suggests one billion on the move globally if we end up at 2C in 2100 (recent predictions by climate scientists Zeke Hausfather and Frances C Moore have us landing there at 2.6C). In any case, a massive chunk of humanity will be increasingly demanding that we, in the north, respond to their absolute destitution. They will be facing “drowned cities; stagnant seas; a crash in biodiversity; intolerable heatwaves; entire countries becoming uninhabitable; widespread hunger …”

“They will keep coming because there will be no choice,” writes Vince. “The question is whether they will be helped or whether the rest of the world will stand by and watch them die.”

What is daring about Nomad Century is that Vince goes to the heart of that question – which is our deep attitude to humanity on the move across the surface of the planet. How do we shift these feelings away from fearfulness and defensiveness?

Partly by dwelling on our ancient and primal history, the author suggests. Humans’ superpower as a species has been our ability to live – and thus move to – almost anywhere on the planet.

We aren’t tailored to an environmental niche, writes Vince: “We are highly adaptive and hypersocial, able to cooperate with large numbers of unrelated people, supporting each other and sharing resources, ideas and knowledge… Migration allowed our species to survive environmental challenges, intertribal clashes, territorial disputes, food and resource scarcity, interbreeding and disease.”

If that’s the natural human story, pertinent for most of our existence, then we should be able to look at our current borders and walls with some scepticism, suggests Vince. She digs up some intriguing historical facts.

For example, in the UK, between 1823 and the Aliens Act of 1905, “not a single foreign citizen was either refused entry or expelled from the country”. An 1835 Times editorial declared: “this country is an asylum nation, and it will defend the asylum to the last ounce of its treasure and to the last drop of its blood”.

This is very far from today’s “hostile environment”, as Vince sharply notes: “While in the late 19th century, 14% of the global population were international migrants, today, just over 3% (though of a much larger population) are.”

So can we construct another new, 21st-century consensus on migration, shifting it from “what ought to be allowed, towards planning for what will occur”? That is, from controlling to managing migration?

Vince thinks we’ll get there by supporting new global bodies. She suggests a United Nations department for global migration, which could administer a “universal travel scheme”. She sees a precedent for this in the “Nansen Passport” of the inter-World War years. This was first proposed by the Norwegian explorer Fridtjof Nansen, who was also the first international High Commissioner for refugees.

THE Nansen passport enabled the movement of stateless refugees to find work in all the participating nations (the League of Nations at the time). Today’s equivalent would grant migrants a prior status as “UN citizens”, allocate them to globally managed quota systems, and then expect them to participate in the upscaling and retrofitting of the cities in which they had landed.

Might it be too idealistic of Vince, in the age of lectern-thumping populists, to suggest that governments will be able to disconnect their politics from their geographies? Her vision is that we can globally “identify where the freshwater resources are, where the safe temperatures are, where gets the most solar or wind energy, and then plan population, food and energy production around that.”

Yet where’s the world governance for that process coming from, in these fractious, multi-polar days? I’m wondering if there might still be a role for nation-states – old, new or forthcoming – in prototyping these visions. I reached out to Vince on social media on Thursday to ask whether a Scottish state might have competitive advantages if it welcomed migratory populations.

“Absolutely”, she posted back.”Pro-migrant policies are to the nation’s benefit, building economic and social strength … Longer, more productive growing periods for crops and forestry, greater fish diversity (unless overfishing kills that), warmer winters requiring less heating”. These benefits will drive new and expanding cities in “Scotland, Ireland and Estonia,” she writes, “elevated sites with plenty of water”. Like Iceland, notes Vince, Scotland’s land level is even rising since the end of the last Ice Age.

I had also noticed a graphic in her book, titled “belts of habitability in a 4C world”, where the line of habitability dividing “high-latitude areas where agriculture is possible” and “Saharan deserts expanding into southern and central Europe” ran right through the Midlands, leaving the north and Scotland on the desirable side. True?

“Everywhere will experience the negative impacts of extreme weather, but Scotland will be less affected than most places further south,” replied Vince. Another map on “the most vulnerable regions of the world” shows a globe covered in blackened heat spots – with these sceptred isles pale and unblemished.

We generally know that a teeming possibility for Scotland is our position in the North Sea, as melting ice makes an Arctic trade passage ever more possible.

Vince adds to this the fact that cities will have to be built in these newly habitable Arctic lands, further fuelling trade possibilities. As ever, looked at from these megatrends, the case for effective Scottish national sovereignty to manage these realities becomes thuddingly obvious.

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But there’s an old irony to be savoured here. The “independence in Europe” that got many of us on the bus of indy implied a sophisticated sovereignty – one that, when asserted, was then intelligently shared with co-operative neighbours.

We now have to complement that with “independence in the biosphere”. We’re in a situation where a responsible northern state faces tidal waves of humanity torched out of their homelands by the climatic consequences of an industrial and consumerist era we fully played our part in.

Our vision of Scottish independence will once again have to subject its national self-determination to wider, juster considerations – particularly in this migration-centred, nomadic century. At least, we can say we’ve already had the argument.

And we know exactly who we’re distancing ourselves from.