Borders,” said Jordan Bardella, the leader of France’s far-right National Rally party, in 2019, are “the environment’s greatest ally; it is through them that we will save the planet.” It’s a tall claim, for no amount of wall-building or border militarization will keep the climate out. But for Bardella, as well as for his predecessor at the National Rally’s helm, Marine Le Pen, there is a simple logic to border control as an environmental policy. Eight years ago, the party—then the National Front—launched its New Ecology movement, a strand of eco-nationalism that sees immigration as the chief threat to France’s ecological survival. Until then, much of the party’s anti-immigration rhetoric had focused on the threat that incoming migrants posed to French “culture” (whatever that may be); its shift to include climate change in its party platform was an effort to fuse white nationalism with “green nationalism”—to greenwash xenophobia—and, in the process, make its nativist ideology attractive to a wider pool of voters.

The axiom that borders protect what’s within from what’s without has provided political leaders with a rationale for reifying them as physical barriers since the time of the first walled cities six millennia ago. Little has changed. Donald Trump had wanted his “big, beautiful wall” along the US-Mexico border because, as he saw it, many of the evils eating away at American prosperity—drugs, violent crime, cheaper labor—are brought in by migrants and refugees. That has also been the argument, spoken plainly and confidently, of successive recent home secretaries in the United Kingdom, while the National Rally’s addition of an ecological gloss to this age-old canard about migration’s ills only speaks to the way the power of the border has evolved in the minds of nationalist leaders.

Implicit in these leaders’ efforts to limit outside intrusion is a belief that the national body contained within has already decided the shape and character it wants to have and will brook no challenge to that. But that notion has its challengers. The political philosopher Glen Newey thought strong borders to be anything but proof of a society’s confidence in its sense of self: “The wall and its symbolic proxies,” he wrote, “are built when a political authority cannot flatter itself as a settled fact.” In his reading, efforts to strengthen a border don’t evidence an authority already well-established but rather are part of a process by which an authority attempts to establish and maintain itself; ergo, fences, walls, militarization, and the like reflect a national mindset that is brittle and, especially today, fearful of the state of impermanence that all political authorities and all societies in our globalized world exist in—and the fate it entails.

Borders—and land borders in particular—also often fail to establish the “us/them” dichotomy between insider and outsider that exclusionary nationalist politicians and citizens might wish for. More often than not, they are sites of busy interaction and cross-cultural exchange, if not contiguity. In regions of Asia and Africa once ruled by Europeans, colonial cartographers often drew borders straight through ethnic groupings; as a result, peoples of shared ethnicity and lineage have long existed across borders, and they pay scant attention to the barriers to movement they are supposed to be. The fact that the edges of many nations are dynamic and porous, not repellent, makes the task of constructing a national identity via antithesis—the “we are what they are not” exercise beloved of the likes of Le Pen—difficult. Anyone with a critical eye who visits those edges may struggle to see evidence that the peoples on either side of the line are in any way distinct from one another, let alone “settled” in their national identity.

James Crawford, a Scottish journalist and broadcaster, has just such a critical eye. His new book, The Edge of the Plain: How Borders Make and Break Our World, is, at its core, an argument against the assertion that borders can ever make anything permanent, not least themselves. Jordan Bardella’s claim that borders will “save the planet” is risible on many fronts, but perhaps the greatest irony of the green nationalism his party promotes comes from the fact that borders are themselves now threatened by the very thing the National Rally believes it provides a bulwark against: climate breakdown.

Crawford visits the Graffener Glacier, high up in the Ötztal Alps. Its uppermost ridges mark the watershed line, along which meltwater runs down on one side into Italy and on the other into Austria. For more than a century, that high line has marked this section of the Italy-Austria border, but the Graffener Glacier is moving. And so too, therefore, is the border.

Italy and Austria recognized the mutability of their shared border (in some places, it has moved by nearly 100 meters) via an agreement signed in 2006. Switzerland, which has also long used the watershed line to mark parts of its southern limits, followed suit in 2009. These agreements introduced something new to geopolitical relations: A state cedes its powers to decide a borderline to a mobile natural feature. It is a glacier—or rather, the climatic forces that cause the glacier to migrate—that now determines sections of the three countries’ borders. Sometimes Austria loses a bit of land, sometimes Italy or Switzerland does. As the owner of a mountain lodge somewhere on, or rather near, the Italy-Switzerland border has discovered, this can complicate a number of things, not least one’s sense of where they belong: His lodge, atop a glacier, bedecked in Italian flags, was once squarely in Italy; now it may well be in Switzerland.

Crawford writes frequently of the “restlessness” of borders. That description chimes with the notion pushed by the German geographer Friedrich Ratzel in the late 19th century that nation-states should be understood as biological entities of sorts—“living spaces,” or Lebensraum, that need to take ever more territory if they are to sustain themselves. Although Ratzel’s thinking later became central to the ideology of the Third Reich and is therefore invariably studied as a Nazi concept, it’s a useful way of understanding how most nation-states, ever since the Treaty of Westphalia in 1648 brought the system into being, have envisioned the functioning of their borders: as a protective epidermis (as Crawford puts it) that must adapt and expand in accordance with whatever the “brain” thinks the “body” needs to feed and nourish itself.

And they still do. Russia’s annexation of Crimea in 2014 and parts of Ukraine in 2022 are obvious contemporary demonstrations of it. But the idea also, dare it be said, is present in the logic of Israel’s separation barrier and the Israeli state’s goal of complete control of the West Bank. Even that barrier, set for the most part in concrete, and sunk deep into the ground to prevent tunnelling, cannot be described as settled. “It had pushed deep into Bethlehem, a long finger of concrete,” writes Crawford, who spent time along the barrier.

But it wasn’t a symbol of permanence. Rather, it was one of movement. I could tell that it was anxious to push further, to self-replicate, to keep going.

In a sense, however, the moving barrier is a symbol of permanence—or, at least, a hoped-for permanence. According to the argument of successive Israeli governments, it has to be able to grow—longer, higher, stronger—and annex ever more Palestinian land in order that Israel itself be made permanent. The British Israeli architect Eyal Weizman has described the barrier as the “material embodiment of state ideology,” but more specifically it is the material embodiment of state insecurity. Eight meters high in some places, with sniper towers, checkpoints, and high-tech surveillance systems, the barrier announces Israel as a state that loudly and urgently wants to establish itself as a “settled fact,” but can’t.

It would be tempting to organize a book on international borders around geopolitical flash points: places where territorial disagreements have been the fuse for conflict, or where borders have become sites of migrant “crises.” Crawford does cover some well-trodden ground, and in several sections, like the one on Israel-Palestine, he recapitulates familiar histories, giving necessary context but adding little that’s new. But as all good travel writers do (and this is a travelogue as much as it is a political-historical examination of borders), he also leaves the beaten track, steering the narrative away from the typical flash points to places where, for instance, the fluid boundaries of a homeland, rather than the rigid borders of a nation-state, structure how a community understands its “place,” or where individuals have taken up the task of mapping long-erased borders, in the process reminding us that these lines can one day simply disappear and, in time, be forgotten.

Crawford documents a years-long effort by two artists—a Mexican, Marcos Ramírez ERRE, and an American, David Taylor—to map, and mark with six-and-a-half-foot-high steel obelisks, another US-Mexico border: one that existed two centuries ago and ran not from Tijuana to Matamoros, as it does now, but from Oregon down to Louisiana. This was the location of the Adams-Onís Treaty borderline, which lasted from 1821 until the Mexican-American War of 1848, after which Mexico lost a half-million square miles of its land to the United States. Ramirez ERRE and Taylor’s guerrilla operation (they didn’t seek permission from authorities, except when the line they followed crossed Native American territory) is richly narrated by Crawford, who writes that the planting of these obelisks—purposefully not cemented into the ground, and thus at the mercy of people and weather—“was a perfect way to capture the ephemerality of borders.”

As Taylor told him:

“The idea was that our obelisks could be stolen, tripped over, blown over. The whole notion was that this work would be transitory. It would recede over time. And so it really ends up being emblematic of the fact that this border didn’t really exist for any great period. We wanted to create a gesture in the land that really acknowledged its existence, made its claim to history. But then allowed it to take its course from there on out.”

Crawford’s book asks whether we might ever “let go of the lines that divide us.” That desire doesn’t belong only to the left: Cosmopolitans and neoliberals who want greater freedom of movement, for themselves and their money, also consider borders to place unfair limits on their ability to set up shop and prosper in whatever part of the world they choose—the only difference is that the rich among them have the means to buy access and citizenship, and few states are really so precious about their cultural integrity that they won’t let the wealthy “other” in.

So what fate awaits these lines? Their durability, of course, is inextricably bound up with the durability of the nation-state system. And because that system’s ability to survive for much longer in a world of deregulated finance, international legal mechanisms, remote-warfare technologies, and other borderless phenomena is in doubt, it should follow that the future of borders is too. Yet, as Wendy Brown argued more than a decade ago, it is precisely this trend—the “waning sovereignty” of nation-states—that spurs ever more aggressive acts of exclusion at the border, such as the building of walls: a “monstrous tribute,” as she saw it, to the weakened condition of the sovereign nation within.

That trend shows few signs of changing direction. If anything, so-called border “crises” are driving ever more extreme acts of deterrence by states—the US and European governments now consider even the rescuing of desperate migrants a criminal act, while the Conservative government in the UK continues to argue its case for shipping asylum seekers to Rwanda. The inhumanity of hard borders may well come into sharper focus as the climate crisis forces migration on an ever-larger scale—but if borders alone won’t deter those moving populations from seeking safer ground, the violent mentality they signify will continue to materialize in physical form to beat them back.