The ice is thin and getting thinner. On May 16, one Italian and four English scientists published the results of 25 years of satellite monitoring of the Antarctic ice sheets. Their findings were discouraging: The vast Pine Island and Thwaites glaciers are thinning five times faster than they were in 1992; 24 percent of West Antarctica is now “in a state of dynamical imbalance.” Four days later, another study predicted that under a “business as usual” scenario—i.e., the current plan—sea levels will swell by more than two meters by the end of the century, resulting in the displacement of 187 million people. That figure does not count those displaced by other climate-related catastrophes: desertification, drought, wildfires, floods, crop failures, hurricanes, etc. Even so, the authors wrote, there will “clearly” be “profound consequences for humanity.”

We are already beginning to suffer some of them. The racism and fear that dominate the terms of the “immigration debate” prevent us from seeing it, but the climate crisis is one of the major factors spurring the movements of human beings across borders. Severe drought in Central America has been pushing Hondurans, Salvadorans, and Guatemalans north through Mexico to the United States. Droughts in the Sahel, the Horn of Africa, and the Lake Chad Basin have been driving many thousands from both north and sub-Saharan Africa to risk the journeys across the Sahara and the Mediterranean to Europe. A sustained drought in Syria caused massive internal displacement, helping to spark an uprising that degraded into war, causing hundreds of thousands to flee across borders that, for all their apparent permanence, didn’t exist a little more than a century ago.

The timing could not be worse. In the absence of an actual world war, national borders have never in human history been as militarized as they are today. Borders, like nations, present themselves as natural and eternal. They are neither, but movement is. Humans have been on the move for hundreds of thousands, perhaps even millions of years. For centuries, institutions like slavery and serfdom restricted the movements of the sectors of society that did most of the work, but until just over 100 years ago, per John C. Torpey’s The Invention of the Passport, there was no “consensus for the view that states had an unequivocal right to bar foreigners from entry into their territory.” Passports were not generally carried or required until the First World War. The United States had no Border Patrol until 1924. Borders as we now understand them—the fixed and impermeable shells of what the political economist Karl Polanyi called “the new, crustacean type of nation”—did not exist when my grandparents were born.

Over the last hundred years, borders have come to function much as serfdom did until the 19th century: as a means of restricting the movements of the poor. Some of us are free to hop continents, suffering only the discomforts of economy seats; for the wealthy, scholar Parvathi Raman points out, “open borders are already a reality.” Others, who the accident of birth deprived of the right brand of passport, die by the tens of thousands in the deserts and in the Mediterranean. Thousands more survive the journey only to be detained, caged, tortured, and starved, or dumped back where they started.

The planet’s most prosperous residents, meanwhile, have not been gracious about their good fortune. Manufacturing a “crisis” at the borders in order to justify their further hardening has for decades been a project of the super-rich, one achieved through years of investment in think tanks, media, and political candidates spouting “populist” rhetoric. Some of the individuals who have profited most from the creation of the climate crisis are the same ones demanding that the fictional boundaries that disfigure the planet be reinforced with a violence that is all too real. One quick for-instance: The main, long-term funder of the anti-immigrant movement in the United States is the Colcom Foundation, which relies on the fortune of the Mellon Scaife family, and hence of Gulf Oil, now Chevron. To protect their investments, perhaps, Scaife family foundations have also funneled tens of millions into climate-change denial.

If the 20th century offered just one lesson, it is that the ice is always thinner than we think. The centrifugal forces holding nations together are the same ones that can tear the world apart. Ours is already beginning to fissure. In 2015 it took the arrival of fewer than a million refugees, about half of them from Syria, to push a continent of more than 700 million into a panic that continues to threaten the European Union with dissolution. (For comparison, imagine 700 of the most comfortable people human history has ever known all freaking out because a single tired stranger is knocking at the gate.) In the United States, a country of 329 million, the presence of 11 million people without the appropriate papers or levels of melanin has been enough to bring national politics to a near standstill, send an obvious cretin to the White House, and rehabilitate the concentration camp as a viable form of housing for children.

This is just the beginning—of the climate crisis, and the political unravelings that will continue to accompany it. And so, it is time to shout, and loudly, that the freedom of all the earth’s people to move across borders must be at the center of any response to the climate crisis. Unless we do, racism and fear—hidden as always in the guise of “security”—will give way to fascism and war before the tides get a chance to drown us.

Authoritarian solutions are most appealing in times of great uncertainty, which is exactly where we’re at. Eco-fascism, a green-tinged white nationalism that puts a tad more emphasis on the “soil” pole of the old blood-and-soil dyad, was once a fringe phenomenon. No more: Its esoteric strands motivated the shooter in the Christchurch mosque massacre, who described himself as an eco-fascist, but it’s also easy to hear in the president’s latest Twitter refrain: “Our country is FULL.” In a more respectable and dopier form, you can find it echoing through the New York Times op-ed page, where Tom Friedman recently called for an immigration policy that would involve “mitigating climate change” while building a “high wall” with a “smart gate” that allows only “high-energy and high-I.Q. immigrants” to pass.

Any argument for opening the borders has to tackle the specious logic that lies behind all of these formulations. This logic imagines a nation as something like an ark, or a lifeboat, and frets that there is only so much room, so much food, so much water, so much wealth. We would if we could, but we can’t, so fuck off. At its extremes this is nakedly repugnant: See the Finnish eco-fascist patriarch Pentti Linkola’s insistence that “those who love and respect life will take the ship’s axe and sever the extra hands” clinging to the side of the boat. But how different from the ugliest forms of “race realism” is the realism, so-called, that guided American policy for much of the last century? “We have about 50 percent of the world’s wealth but only 6.3 percent of its population,” George Kennan wrote in a State Department memo in 1948. “Our real task in the coming period is to devise a pattern of relationships which will permit us to maintain this position of disparity.”

There is nothing real about the dilemmas that such “clear-eyed” realism poses, and never was. The metaphor misleads: There’s no lifeboat, just a getaway car, and if you think you’re riding in it, you’re probably wrong.

If we are to survive as a species, we must know that no boat can save us except the one we build together. Oil fracked in North Dakota melts glaciers in Greenland and Nepal. Jungle cleared in Indonesia brings drought to Washington and Guatemala, fires to Greece and California, and storms that spread death from Honduras to the Florida Panhandle. Solidarity across all geopolitical boundaries—with one another and against the tiny segment of the planet’s population that is profiting off our demise—is our only hope. Borders can offer no “security,” only a plan for murder-suicide, a delusion that gets more deadly with each passing day.

Since 1848, the southern boundary of the United States has been marked by the Rio Grande—specifically by “the middle of that river, following its deepest channel.” These days, for most of the year, more than 300 miles of the river’s course runs dry. The planet, as always, is speaking clearly, and offering another path.