God promised Abraham that he would make his descendants “as numerous as the stars in the sky and as the sand on the seashore.” We must assume that the readers of the Hebrew Bible took this to be a good thing – the greatest of blessings, in fact.

But Lloyd Williamson, an environmentalist activist from Essex, United Kingdom, takes a very different view of his possible progeny. When he reached his early twenties, as he told the Guardian, he thought “You know what? I don’t want to bring a life into this world, because it’s pretty shitty as it is and it’s only going to get worse.” At the age of thirty, Williamson underwent a vasectomy. He is among a growing number of people who say they are committing to remain childless in response to the threat posed by climate change.

In a paper published in the Lancet last year, among ten thousand people aged sixteen to twenty-five surveyed in ten countries, 39 percent of respondents reported that they were “hesitant to have children” because of climate change. Other surveys find high levels of anxiety among children. One conducted by the BBC in 2020 found that 20 percent of children aged eight to sixteen reported having had at least one nightmare about climate change. Many in this generation are profoundly gloomy about the future of the planet.

Many climate-change campaigning organizations agree with this assessment, and agree also with the goals of “BirthStrikers,” environmental activists who have elected to remain childless. Population Matters, for instance, is a UK-based charity that campaigns on global population size and its effect on environmental sustainability. “One of the most effective ways that we can help our planet today is by choosing to have a smaller family,” the Population Matters website informs visitors.

With or without the interventions of activists, though, population growth is already waning worldwide. “Demographic transition” is a sociological term that refers to the historical shift from the high birth and death rates that were once ubiquitous across the world toward longer lives and fewer children. The first countries to experience the demographic transition were European, beginning in the nineteenth century, and it has now occurred everywhere, with the exception of some parts of sub-Saharan Africa.

In the 1980s, two Dutch sociologists advanced a provocative hypothesis: that many societies might be undergoing a “second demographic transition” that would lead to birthrates so low they would fall below replacement level. At the time, they were dismissed by their peers, but now their hypothesis has been vindicated. The world population is still growing, but only because of high birthrates in Africa – a temporary reprieve. In almost every other part of the world, the population is shrinking. A paper published in 2020 in the Lancet predicted that the world’s population is set to peak at 9.73 billion in 2064, and then decline.

Experts are divided on exactly what is causing the second demographic transition. Brad Wilcox, a fellow at the Institute for Family Studies, describes a complex interplay of factors:

There is an economic story behind falling fertility in the developed world, but there is a cultural story here as well. People who are more religious and conservative seem to have more of a motivation to have kids, and also less fear, including climate fear, whereas people on the left and secularists are more worried about having babies.

Wilcox points out that, while their climate fear is certainly sincere, it is not the only factor at play for those reluctant to have children. There is what sociologists term an “elective affinity” between environmentalism and other lifestyle factors that are known to lead to lower fertility: in particular, lack of religious faith. There is a very strong negative relationship between secularism and fertility, both for societies and for individuals. It seems that people who don’t believe also tend to have fewer babies. Looking at data covering more than fifty countries and more than eighty thousand people, sociologist Landon Schnabel of Cornell University found that across many countries, secular people have fewer children than religious people. The effect holds true for societies as well: in more secular countries, even religious people tend to have fewer children than their co-religionists in less secular countries, though they tend to have more than their secular compatriots. Social mores are powerful – but faith can, it seems, push back against them.

Such studies suggest that there is an important spiritual component to the crisis in which we find ourselves. To be sure, there is a real environmental problem that urgently deserves our attention and action. Yet there is also a problem of faith, and it is expressed most clearly in the divisions within the environmentalist movement.

The writer and futurist Alex Steffen describes three categories of environmentalist: “light greens,” who encourage lifestyle changes at the individual level; “dark greens,” who believe that environmental destruction is an inevitable consequence of industrialized capitalism and therefore work towards radical political change; and “bright greens,” who see an answer in technological innovation.

It is the dark greens and the bright greens who are most at odds over the issue of population reduction. From one angle, the dispute is an empirical one: Could new technology plausibly have a large enough impact to avert climate catastrophe? The American economist Eli Dourado is among those who believe it could. “The writing is on the wall,” he tells me:

By the time the decade is out, the majority of cars being sold are going to be electric. Almost-zero-carbon transport is on the way. … New technologies are coming online, like geothermal, which is likely to be very big in about ten years or so. The potential there is enormous: not just lower cost, and lower emissions, but a greater abundance of energy than ever before.

Techno-optimists like Dourado understand climate change to be a technical problem, readily solvable with enough investment. This could come from governments, or it could come from private companies: the billionaire entrepreneur Elon Musk is currently running a competition to find the most effective solutions for pulling carbon dioxide directly from the atmosphere or oceans and sequestering it durably and sustainably. The winner will be awarded $100 million, the largest incentive prize in history. Musk – who has nine children – is resolutely against the “BirthStrike” movement, telling the audience at a Wall Street Journal event in December 2021 that “if people don’t have more children, civilization is going to crumble, mark my words.”

Light greens vary in their sensibilities, but tend toward a less technologically bombastic approach. They often advocate change driven by personal choice – to cycle rather than drive, to take up various “green” practices. Some light greens seek society-wide commitments to live less wastefully, to live with natural systems rather than seeking to overcome them; they sometimes see in Musk-style technology its own temptation toward excess.

Other environmentalists are skeptical of the idea that technological innovation, personal choice, or renewed cultural interest in and commitment to sustainable agriculture alone will avert climate catastrophe. Anna Hughes is the director of Flight Free, a British organization that campaigns to inform people of the climate impact of aviation and inspire them to travel by other means. She has also personally resolved not to have children – a decision she reached in her early twenties, partly in recognition of the environmental impact of population growth. I ask Hughes for her view of the “bright green” environmentalist project:

Sure, we can try to technologize our way out of this, but we cannot just keep adding to our number because, regardless of how much we reduce our emissions, if we keep on growing then our emissions will keep going up: it’s simple maths. So we have to talk about the population question.

To some degree, the disagreement between Dourado and Hughes is simply on the question of timescale. Dourado is expecting the technology to come on in leaps and bounds, and soon – by the end of this decade, say – whereas Hughes is more pessimistic.

But there is also something more temperamental at play in the differences between the bright and light and dark greens. There is a fundamental gap between how these groups of people regard the future, and it is expressed most clearly in their outlook on children – the people who, of course, literally embody the future.

One of Anna Hughes’s fellow campaigners told her recently that she felt distress, not so much at the prospect of her children suffering in a world affected by climate chaos, but at the prospect of their loss of faith in the future, that “they will live knowing that all hope is lost.”

Contrast this perspective with Elon Musk’s project to build human settlements on Mars, a project that Eli Dourado supports, telling me “I think it would be a shame if, within the next century, we are not expanding into the solar system.” Faced with exactly the same environmental problem, some people have resolved not to bring any more human life into the world, while others are looking to the heavens and imagining new human lives “as numerous as the stars in the sky.” This is in part, again, a question of timescale: Can we get off the earth soon enough? But it is a spiritual one as well.

This division of sensibility within various branches of the environmental movement is echoed, though not perfectly, in divisions among political and religious groups. Modern secular progressives – the group least motivated to reproduce, according to Nitzan Peri-Rotem’s 2016 study “Religion and Fertility in Western Europe”– have a fraught relationship with both the past and the future. Theirs is a restless ideology that both predicts and insists upon constant renewal in the form of “progress,” with new frontiers constantly presented to adherents. We live in a society that is unhappy with its past – really, in truth, unhappy with itself.

Climate change presents a problem for progressive ideology, which comes from a tradition predicated on the expectation of inexorable improvement. But at the same time, progressives are more likely to believe that we will find ourselves collectively faced with catastrophe at some point in the near future. A 2017 study of Americans revealed that around 70 percent of Democrats believe that major climate-related catastrophes will occur within the next fifty years, while only about 20 percent of Republicans do. Anecdotally, I’ve found that those who believe in a very definite full stop within our lifetimes due to climate apocalypse are almost always progressive and secular.

“If you’re younger than sixty,” claimed novelist Jonathan Franzen in a 2019 New Yorker article, “you have a good chance of witnessing the radical destabilization of life on earth. … If you’re under thirty, you’re all but guaranteed to witness it.”

Franzen is also noted for his rejection of those authors in whose tradition he writes, for their regressive sensibilities. “Read a book from fifty years ago by John Updike, Norman Mailer, Thomas Pynchon, Kurt Vonnegut and, even though I love him, Joseph Heller, and you see they weren’t thinking about women in the right way,” said Franzen in a 2021 interview defending, essentially, cancel culture. “I wish people would be spontaneously sensitive, but if they can’t, then a little bit of enforcement doesn’t seem to me a bad thing.”

Thus progressives like Franzen find themselves precariously poised in the present moment. Both the past and the future are rejected: the former for its sinfulness, the latter for its fearsomeness.

In 1968, The Population Bomb, a book written by Stanford University professor Paul R. Ehrlich and his wife, Anne Ehrlich, predicted catastrophe as a consequence of uncontrolled population growth, with hundreds of millions of people set to starve to death in famines that would occur during the 1970s and 1980s. The book was written in a tumultuous year, both politically and culturally, and it evidently hit a nerve, going on to sell millions of copies, aided by the apocalyptic public pronouncements of its author. “Sometime in the next fifteen years, the end will come,” Paul Ehrlich told CBS News in 1970. “And by ‘the end’ I mean an utter breakdown of the capacity of the planet to support humanity.”

The Population Bomb’s dire predictions did not come to pass, either after fifteen years or fifty and counting. The world’s population has more than doubled since the publication of the book, and yet deaths from famine have declined radically since the book was published, from fifty people per one hundred thousand annually during the 1960s to less than one person per hundred thousand anually in the 2010s. As well, world hunger is now dramatically reduced: at the time the Ehrliches wrote, one person in three was chronically hungry; that proportion has fallen to one in nine. This improvement is due in large part to the “green revolution” of high-yield crop varieties that increased food production. In this instance, the techno-optimists were vindicated.

That does not, of course, necessarily mean that they will be vindicated again. But the mistakes of The Population Bomb reveal something important about how a febrile historical moment can lend itself to widespread panic about the future. At times of conflict and uncertainty, faith often falters. It’s little wonder that one-third of a generation is reluctant to participate in the transhistorical project that is family formation – a project that demands that we place our faith in the future, delivering to it our most precious offering. But though this reluctance is understandable, it is ultimately not sustainable. The future belongs to those who hope.