A section of the U.S.-Mexico border wall between Sunland Park, Texas, and Ciudad Juárez, ChihuahuaJose Luis Gonzalez / Reuters

On Tuesday afternoon, President Donald Trump shared a new idea with congressional Republicans:

His vision was a [U.S.-Mexico border] wall 40 feet to 50 feet high and covered with solar panels so they’d be “beautiful structures,” the people said. The president said that most walls you hear about are 14 feet or 15 feet tall but this would be nothing like those walls. Trump told the lawmakers they could talk about the solar-paneled wall as long as they said it was his idea.

“One person cautioned that the President wasn’t presenting the solar-paneled wall as the definite solution,” adds Jonathan Swan, the Axios reporter who first reported most of the news.

Despite the president’s insistence on getting credit, this is not the first time someone has suggested swaddling the wall in solar panels. During the government’s call for proposals in April, a small, Las Vegas-based construction-supply firm named Gleason Partners suggested a suspiciously similar plan. It proposed building a wall of cement, steel, and solar panels. Each mile of wall would cost $7.5 million, it said, but each mile would also generate two megawatts of electricity. This power could then be sold to utilities on both sides of the border.

Never mind Mexico—now the sun would pay for the wall. (Or as Tom Gleason, the firm’s founder, told E&E News: “The wall pays for itself.”)

Gleason’s proposal even included a mockup, which hints at how his firm would solve a tricky engineering problem. Solar panels usually go on roofs, not on walls, because the goal is to keep them out of shadow and expose their surface to as much sun as possible through the day. To get around this issue, Gleason angles two rows of panels slightly off the wall’s perpendicular:

Gleason Partners LLC
Gleason Partners LLC

In North America, solar panels also usually face south, toward the equator. So presumably the most expensive hardware on the wall would look toward Mexico.

From Trump, the idea seemed like a politically simplistic troll. Progressives will not magically come to support a divisive mega-project if it also subsidizes renewable firms. Environmental groups that believe the wall will hurt local ecosystems will still oppose the project even if it becomes carbon neutral. As Brett Hartl of the Center for Biodiversity said in a statement on Tuesday: “An ecological disaster with solar panels on top is still an ecological disaster. With solar panels on top.”

But it is not the first time that immigration restrictionists have borrowed environmental arguments to bolster their appeal. John Hultgren, a professor of environmental politics at Bennington College, filled a book with examples of the overlap between the two groups: the now aptly titled Border Walls Gone Green.

Some contemporary figures in immigration restrictionism began in the environmental movement. John Tanton, who founded three immigration-lobbying groups, including the Federation for American Immigration Reform, began his involvement in politics through environmental activism. He says he once lobbied the Sierra Club to adopt anti-immigration positions; when they demurred, he founded his own network of groups.

Today, the Southern Poverty Law Center calls Tanton “the racist architect of the modern anti-immigrant movement.” They cite a letter of Tanton’s held at the University of Michigan, in which he writes: “I’ve come to the point of view that for European-American society and culture to persist requires a European-American majority, and a clear one at that.” (The New York Times covered the relationship between Tanton and the SPLC in April.) Linda Chavez, a veteran of the Reagan administration, has said that Tanton is both “anti-Hispanic” and “anti-Catholic.”

Tanton’s own website describes him as a supporter of “population stabilization” and “environmentally sustainable immigration numbers.”

But the connections between pro-nature sentiment and anti-immigration politics—especially at their most racist—are strongest long before the modern era.

“Some of the earliest American environmental groups had interesting and important connections to the eugenics movement,” Hultgren told me. The most famous of these is Madison Grant, who worked to conserve huge swaths of American wilderness and helped create the national park system.

As Citylab’s Brentin Mock wrote last year, Grant was also a eugenicist and white supremacist. His book, The Passing of the Great Race, served as a bedrock of American and European pseudo-scientific racism until the second world war. Hitler quoted often from Grant’s writing in speeches and allegedly corresponded with him. (F. Scott Fitzgerald also implies Grant’s work is a favorite of Tom Buchanan’s in The Great Gatsby.)

But Grant’s influence was not just theoretical: He had a material and long-lasting influence on U.S. immigration policy. His statistics and “expertise” informed the quotas of the Immigration Act of 1924, which banned almost all Asians and Arabs from migrating to the United States. It also placed quotas on the entry of southern and eastern Europeans. These rules effectively prevented many Jews from escaping Nazi Germany, and they were not fully repealed until the Immigration Act of 1965.

It may seem a casual coincidence that an American conservationist was also smitten with racism. But Grant’s views on the environment were inseparable from his adoration for eugenics. When he helped found the Save the Redwoods League, it was out of the same loyalty to the pure.

“To Grant, the redwoods were threatened with ‘race suicide’ in the same ways that whites were,” says Hultgren. “These folks really saw national purity and natural purity as being interconnected.”

This was true also of Theodore Roosevelt’s nationalist project, which birthed the U.S. National Park Service. In a 1909 government report commissioned by President Roosevelt—A Report on National Vitality, Its Wastes and Conservation—the economist Irving Fisher spends a full chapter on “Conservation by Heredity.”

“President Roosevelt has pointed out that ‘race suicide’ is a sign and accompaniment of coming decay,” Irving writes. “A race that can not hold its fiber strong and true deserves to suffer extinction through race suicide. The decline of our Puritan stock ... need not alarm us if we can replace it with a new influx from the West or from the vigorous stocks of Europe.”

Hultgren notes that many environmental groups have now reversed their old anti-immigration positions. In 2013, the Sierra Club, Greenpeace USA, and 350.org all embraced comprehensive immigration reform.

And—of course—most contemporary advocates of immigration restrictionism do not make racial arguments or share Grant’s zeal for eugenics.

But the occasional overlap between conservationist and restrictionist rhetoric persists. The Federation for American Immigration Reform and other anti-immigration groups have recently used green-style arguments to push for new legal limits. A magazine ad from the early 2010s argued:

With every new U.S. resident, whether from births or immigration, comes further degradation of America’s natural treasures. There’s not much we can do to reclaim the hundreds of millions of acres already destroyed. But we can do something about what’s left.

Stephen Colbert picked up on a TV commercial from the same coalition while in-character on the Report.

Yes, immigrants cause global warming,” he said. “Saving the planet by demonizing immigrants give liberals and conservatives something they can do together. Now, when a liberal yammers on about the record heat we had this winter, a conservative can say: ‘Let’s save the environment by building an electrified border fence that runs on alternative energy.’”

These “Solar Death Panels,” as his chyron put it, made for a laugh line in 2012. In 2017, they constitute a serious U.S. policy proposal.

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