The Fox News host Tucker Carlson has made similar arguments, falsely claiming in an interview with The Atlantic that the Potomac River has gotten dirtier “and that litter is left almost exclusively by immigrants.” The month before, he asked why environmentalists want to let refugees into the United States: “Isn’t crowding your country the fastest way to despoil it, to pollute it?”

It is not hard to see why such ideas are making a comeback. As the relentlessness of environmental calamity — epic fires and floods, escalating extinctions, warming oceans — becomes impossible to ignore, the right needs a way to talk about it. Nationalistic framings fit comfortably with a worldview many already hold. And for the so-called alt right, they offer the bonus of a cudgel for bashing establishment conservatives as beholden to globalist, corporate interests.

Some radicals are drawn to apocalyptic climate scenarios, seeing openings for authoritarianism or a complete societal breakdown. “They want to accelerate it,” said Blair Taylor, program director at the Institute for Social Ecology, a left-wing educational center, who has studied such groups. “So after the downfall they can set up their fascist ethno-states, they can be the Übermensch.” Violent actors are grabbing hold of such ideas. The killers accused of targeting Muslims and Mexican immigrants last year in New Zealand and Texas posted online manifestoes weaving white supremacy with environmental statements.

The Australian man who allegedly murdered 51 people at two Christchurch mosques called himself an “ethnonationalist eco-fascist” and wrote that “continued immigration into Europe is environmental warfare.” The suspect in the El Paso shooting that killed 22 — modern America’s deadliest attack targeting Latinos — ranted about plastic waste and overconsumption. “If we can get rid of enough people, then our way of life can become more sustainable,” he concluded.

If there’s one thing Americans have learned in the Trump era, it is that toxic ideas can move between the fringes and the political realm with stunning speed. Marine Le Pen, leader of France’s far-right National Rally — now the country’s main opposition party — has incorporated worries about the natural world into the party’s anti-immigrant, anti-Muslim ideology. She espouses an ideal of the French citizen as “someone rooted, someone who wants to live on their land and to pass it on to their children.” By contrast, she says, those who are “nomadic … do not care about the environment. They have no homeland.”

“Borders are the environment’s greatest ally,” said Jordan Bardella, the party spokesman and a member of the European Parliament. In Hungary, the far-right party Our Homeland accused Ukraine of poisoning Hungarians by dumping waste in the Tisa River. Extremist Polish groups hurl similar charges at Germany.

As climate change reshapes our world, we face a future filled with new pressures and constraints on resources, including arable land, food and water. Droughts, floods and storms are likely to push millions from their homes, some toward the relative safety and security of Europe, Australia and the United States.

The upsurge of anti-Asian discrimination that has followed in the wake of fears about the coronavirus offers a glimpse of the ugly sentiments such external pressures can unleash. Without giving it much thought, I used to accept the framing of environmental problems as shared concerns we would have to work together to solve. Now I can see there is another path too, one in which dark forces wield real dangers as weapons to tear us apart, and scarcity fuels conflict, brutality and racism. Our future in a hotter world of rising seas and more powerful storms already felt terrifying. Unless we come together — and fast — behind serious action to check the existential danger of climate change, it could be darker still.

Beth Gardiner is an environmental journalist and the author of “Choked: Life and Breath in the Age of Air Pollution.”

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