Some propositions are so obvious that no one takes the time to defend them. A few such propositions are that human life is good, that people can and often do provide more benefits to the world than they take away, and that we should design society to support people in leading lives that are good for themselves and others.

These ideas came under attack, sometimes subtly and sometimes overtly, by environmentalists in the 20th century who were worried about overpopulation. Although major organizations have abandoned population management as an explicit policy goal, the underlying fear that too many people are running up on the limits of too few resources and Well shouldn’t someone do something about that? has never fully been rooted out of American political thought. It is alive and well among NIMBYs. Of all the objections people raise to new housing and infrastructure, perhaps the most risible is that their community is already too crowded. Some even suggest that municipalities should limit housing supply explicitly to combat population growth.

At a recent Palo Alto city-council meeting, one resident argued against pro-housing policies, saying, “Does it make sense to be planning for more people? … More people on the planet spells more consequential implications for climate change, loss of biodiversity, stress, war, famine, etc. At a time when humans are in major ecological overshoot, doesn’t it make more sense to plan for a reduced population, plan for reducing population, not increasing it?”

[Jerusalem Demsas: Community input is bad, actually]

Invariably, the problem is always other people. The man behind the organization that sued UC Berkeley to reduce its enrollment, Phil Bokovoy, told The New Yorker that he opposed building more housing in Berkeley in part because “I don’t think we’ll be able to tackle climate change unless we tackle population growth and rising living standards over a huge part of the world.”

Lest you worry that this is a California-specific brain disease, let me reassure you that this antihuman thinking has permeated discourses all over the nation—and the world.

But population growth is not the problem that so many people seem to think it is, not least because of the global decline in fertility; arguably, declining population growth is the real population-related concern of the century. And even if it were a concern, the policies that NIMBYs support not only fail to create a climate-conscious built environment but actually make fighting climate change more difficult.  

Paul Ehrlich’s 1968 book, The Population Bomb, catalyzed overpopulation concerns among the American public. Ehrlich, a Stanford biologist, also served as the first president of the group Zero Population Growth (ZPG). As the historian Keith Woodhouse recounts in his book, The Ecocentrists, “The group’s goal was an end to population growth; the means, troublingly, were not yet specified. Within three years [of its founding in 1970], ZPG had thirty-two thousand members.”

The Population Bomb opens not with a depiction of overconsumption by high-income Westerners but with the author’s memory of a taxi ride with his wife and daughter “one stinking hot night in Delhi.” Ehrlich describes the “crowded slum area” and proceeds to detail, in prose dripping with disgust, the view from his cab window of people just living their lives: “People eating, people washing, people sleeping. People visiting, arguing, and screaming. People thrusting their hands through the taxi window, begging.” This goes on and culminates in the almost-too-on-the-nose admission: “All three of us were, frankly, frightened.”

As Ehrlich’s family gawked at Delhiites, the U.S. was emitting 18.66 tons of carbon per capita to India’s .33, meaning that the average American was emitting 56 times more than the average Indian. If Ehrlich was genuinely concerned about overconsumption, why is the opening image of his book that of poor, brown people and not the suburban car-centric sprawl that characterizes his home country?

The book’s main argument is that an increasing population will run out of resources and if steps aren’t taken to reduce the population, then scarcity will make the world poor. In particular, Ehrlich was concerned about the world running out of food, and he foretold that mass starvation events would mark the waning decades of the 20th century.

Ehrlich’s dire predictions have been wrong time and again. Hunger and undernourishment have declined since The Population Bomb was released. To emphasize how alarmist his predictions were, a brief aside: In 1969, the author predicted that “by the year 2000 the United Kingdom will simply be a small group of impoverished islands, inhabited by some 70 million hungry people, of little or no concern to the other 5-7 billion inhabitants of a sick world,” later adding, “I would take even money that England will not exist in the year 2000.”

As careful students of history know well, England still exists.

To say that overpopulation skeptics were simply wrong is too generous. Twentieth-century critics on the left saw the movement for what it was: In the 1970s, New Left activists and Students for a Democratic Society both criticized ZPG and overpopulation mania. The latter group, Woodhouse writes, “accused ZPG of reckless simplification, reasoning that by treating all people as a single flat category, population activists ignored not only human difference but also human value.” New Left activists specifically called out the underlying racism of ZPG’s project: “ZPG says that there are too many people, especially non-white people, in the world … that these people are terrifying and violent, and that their population growth must be stopped—by ‘coercion’ if necessary.”

[Read: The next century’s big demographic mystery]

One legacy of this intellectual tradition is the modern xenophobic anti-immigration movement. The Federation for American Immigration Reform (FAIR), founded by John Tanton, was instrumental in advocating for strict immigration controls. (To get a flavor for the callousness of this group, check their website, which tells visitors “How to Report Illegal Aliens.”)

Tanton was president of ZPG from 1975 to 1977 and, as the historian Sebastian Normandin and the philosopher Sean A. Valles wrote in a 2015 paper, FAIR “began as a 1979 offshoot of ZPGs Immigration Committee, following ZPG approval of the proposal in 1978.” While the blend of “1960s ecology and neo-eugenics” seems “idiosyncratic or even fringe today … their influence remains.” The authors conclude that “today’s immigration restrictionist network was built and led by—and in some cases is still led by—a network of conservationists and population control activists.”

Tanton’s anti-immigration views were not just compatible with his concerns about overpopulation, they were born out of them: As Jason Riley wrote in 2019 for The Wall Street Journal, “Opposition to immigration, legal or illegal, was simply a means to that end.”

What should be obvious, but apparently is not, is that opposing immigration actually reduces the U.S.’s ability to cultivate and take advantage of brilliant people who could develop the technological advances to save the planet. (Thirty-seven percent of American Nobel Prize winners in chemistry, medicine, and physics from 2000 to 2020 have been immigrants.)

A growing population means more people generating more ideas, but also more interactions among different people coming from different perspectives. These two effects can sound trivial but actually do lead to more and better ideas. The economist Hisakazu Kato argued in 2016 that “a large population will generate many ideas that could bring about rapid technological progress.”

Overpopulation concern-mongers not only underestimate the ability of people to help solve the problems of climate change; they also fail to accept that neither resources nor human needs are fixed. The idea that resources will “run out” implies that human ingenuity will remain stagnant. But it doesn’t. Norman E. Borlaug won the Nobel Peace Prize in 1970 (just two years after The Population Bomb was published) for helping Mexico become “self-sufficient in grain” by developing “a robust strain of wheat—dwarf wheat—that was adapted to Mexican conditions.” He then worked in India and Pakistan to introduce dwarf wheat to the countries’ agricultural landscape and became known as the father of the “Green Revolution.”

As Gregg Easterbrook noted some years ago in The Atlantic, Ehrlich had written in 1968 that it was a “fantasy” that India would “ever” feed itself. But “by 1974 India was self-sufficient in the production of all cereals.” Borlaug himself was concerned about population growth, but instead of pursuing an anti-humanist agenda, he turned to technological innovation to save countless lives.

The economist Julian Simon, a longtime critic of the overpopulation activists, bet Ehrlich that the price of five metals would fall from 1980 to 1990. As The New York Times noted in Simon’s obituary, Ehrlich believed that “rising demand for raw materials by an exploding global populace would pare supplies of nonrenewable resources, driving up prices.” Simon won the bet.

If the overpopulation alarmists of the 1970s had really wanted, above all, to protect the environment, they should have promoted the development of dense, energy-efficient communities.

The evidence is clear, and has been for some time, that density is good for the environment. As UC Berkeley researchers argued in a 2014 paper, “population-dense cities contribute less greenhouse-gas emissions per person than other areas of the country,” and “the average carbon footprint of households living in the center of large, population-dense urban cities is about 50 percent below average, while households in distant suburbs are up to twice the average.”

But the people worried about other people don’t have a pro-density history; quite the opposite.

As the urban planner Greg Morrow detailed in his 2013 dissertation, overpopulation activists fought for the very legal frameworks that would keep cities low-density and worsen suburban sprawl. Morrow noted that in the early 1970s, the UCLA professor Fred Abraham, then-president of ZPG of Los Angeles, argued that “we need fewer people here—a quality of life, not a quantity of life. We must request a moratorium on growth and recognize that growth should be stopped.” Morrow added that “the Sierra Club (L. Douglas DeNike) agreed and suggested ‘limiting residential housing is one approach to lower birth rates’ and recommended ‘a freeze on zoning to limit new residential construction.’”

Half a century later, NIMBYs who cite overpopulation concerns when opposing new housing say they are afraid of overcrowding on their streets and in their parking lots. Some continue to invoke the global South as a dark warning for the future. In an interview with Slate’s Henry Grabar, Bokovoy, the Berkeley anti-growth activist, warned that his city could end up like “Bangkok, Jakarta, Kuala Lumpur” if more students are allowed to attend the local UC campus. In Trussville, Alabama, the president of a local homeowners’ association played all the hits as he stated his opposition to the inclusion of multifamily housing in a new development in his area: “You’re bringing that many more people with that many more cars,” he complained. “We envision this side of town as spacious properties, higher home values … not having crowded streets.”

We have, of course, discovered an elusive technology to allow more people to live on less land: It’s called an apartment building. And if people would like fewer neighbors competing for parking spaces, then they should rest assured that buses, trains, protected bike lanes, and maintained sidewalks are effective, cutting-edge inventions available to all.

Perhaps you’re pessimistic about technology’s ability to help solve the big environmental problems we’re facing. You may not trust that technology could ever be sufficient to reduce carbon emissions, or that our political systems could make that technology widespread.

If that is the case, think for a second about what it would take to slash the population down by several billion. (Ehrlich himself recently put the optimal number at 1.5 to 2 billion.) The only way to do this is to kill people, limit the aid you give to sick people, and/or stop new people from being born.

Some believe that the third approach could be adequate, and achieved simply by providing people with contraceptives. But survey data show that women are actually having fewer children than they would like, so providing more family-planning services is not going to cut the population by four-fifths.

[Derek Thompson: Why U.S. population growth is collapsing]

NIMBYs and overpopulation skeptics share a sense that the world is too full, that their communities are for the people who already live there, and that new people—immigrants from abroad or the next state over—are simply burdens. And in doing so, they create the world they imagine: unacceptable rates of homelessness, a country lagging far behind its peers in building mass transit, and declining trust.

“I think once you get past this idea that NIMBYs are simply curmudgeons or busybodies then you start to realize why this attitude toward growth today – which in the context of the present housing crises and cost of living crises seems so ridiculous – actually has very firmly embedded ideological roots within…liberalism and thus why it’s so difficult to root out among people who consider themselves liberals,” the historian Jacob Anbinder explained to me.

Between a politics of scarcity that demands inhumane policy interventions and a politics of abundance, it’s not much of a choice, but it’s one that population skeptics have to make. Enough with the innuendo: If overpopulation is the hill you want to die on, then you’ve got to defend the implications.