by Lipton Matthews
In recent years, a quietly radical idea has gained traction in certain environmental circles: stop having children. Some members of Extinction Rebellion in the UK have embraced an anti-natalist position, arguing that a shrinking human population is one of the most powerful levers available for reducing environmental damage. If fewer people exist, the thinking goes, then less energy gets consumed, fewer habitats get destroyed, and the planet gets a much-needed chance to breathe. It is an emotionally compelling argument. But is it actually true? The evidence suggests not. A growing body of research indicates that population decline, by itself, is a surprisingly weak instrument for environmental repair. The relationship between fewer people and a healthier planet is messier and far less automatic than anti-natalists tend to assume.
Perhaps the most fundamental problem with the anti-natalist climate argument is one of timing. Climate change is seen as an urgent crisis demanding decisive action over the next few decades. Population decline, by contrast, operates on a generational timescale, and the two simply do not align in the way that environmental campaigners often hope. To understand why, researchers constructed a rigorous thought experiment. They compared two long-run visions of humanity’s demographic future: one in which global fertility continues falling below replacement level, eventually leading to a shrinking world population, and another in which fertility rates stabilize at replacement level, sustaining a population roughly 90 percent larger by the year 2200. These are dramatically different futures in human terms. Yet when scientists ran both scenarios through a leading climate and economic model, the difference in projected global temperatures by 2200 was less than one-tenth of a degree Celsius.
That result might seem startling at first, but it follows logically once you understand what demographers call population momentum. Think of population size like a tanker ship: even if you change course immediately, the sheer weight and inertia of the vessel means it takes an enormous distance before the new direction becomes apparent. Even if fertility rates changed dramatically today, it would take many decades, an entire generation or more, for those changes to meaningfully shift the total number of people alive on Earth. So slow is this process that it takes until around 2080 for the difference in population size between the two scenarios to even reach 10 percent, despite fertility rates diverging immediately and dramatically. This matters enormously, because it is precisely in these early decades that emissions reductions are most urgent, and by the time any meaningful population difference has emerged, per capita emissions are already projected to have declined substantially due to technological progress and energy policy.
There is also a second force at work that makes population decline an ineffective climate tool, and it concerns not just how many people exist, but when they exist. The carbon footprint of each additional person born is projected to fall steadily towards zero over the course of this century, as the global economy progressively moves away from fossil fuels. Children born today will not be producing large amounts of carbon emissions for another 20–30 years, and by that point the world’s energy systems are expected to be considerably cleaner than they are now. Fertility decisions made in 2025 are, in a very real sense, arriving too late to make a meaningful difference to the atmospheric concentrations of greenhouse gases that will determine the climate of the coming century.
Even under deliberately pessimistic assumptions, scenarios in which warming exceeds 6°C and humanity has not reached net zero even by 2200, the additional warming attributable to a significantly larger population amounts to less than half a degree. Researchers tested this result across twelve different model configurations, varying assumptions about climate policy ambition, the relationship between population size and emissions, and different representations of how greenhouse gases translate into temperature changes. In every single case, the core finding held: large differences in population size produced only small differences in long-run warming. Population decline is not a substitute for climate action. It barely qualifies as a meaningful complement to it.
There is one further dimension to this that cuts against conventional wisdom in an unexpected way. If carbon dioxide genuinely is the primary driver of the climate problem that anti-natalists are concerned about, then a larger population may actually prove to be an environmental asset in the long run rather than a liability. Technologies capable of removing carbon dioxide from the atmosphere at scale are increasingly considered a necessary part of any serious climate strategy, and most major climate projections now assume they will eventually be deployed. Removing a fixed volume of greenhouse gases from the atmosphere represents a fixed cost, much like paying off a collective debt. That cost is cheaper per person when shared among a larger population. Therefore, a larger population, with its greater collective wealth and resources, is better placed to finance and deploy carbon removal at scale, spreading the enormous cost of that undertaking across more contributors and therefore achieving it more quickly and more cheaply per person.
Even setting aside the climate question entirely, the idea that a shrinking population automatically translates into lower resource consumption runs into a significant real-world obstacle. The evidence from countries already living through depopulation suggests the opposite can happen, and Japan offers one of the most instructive examples available anywhere in the world. More than half of Japan’s 47 prefectures have been shrinking since at least 1990, making the country one of the longest-running natural experiments in peacetime depopulation. Researchers analyzing prefectural data on population change and per capita energy consumption between 1990 and 2014 found a counterintuitive pattern. The biggest reductions in energy use per person were generally occurring in the regions where the population was still growing. In many of the regions that were losing people, per capita energy consumption was actually increasing.
How does this happen? The answer lies in the economics of infrastructure and housing, and it is worth pausing to think through the logic carefully, because it overturns a seemingly obvious assumption. When a town or neighborhood loses residents, the buildings, roads, heating systems, and public facilities that were designed to serve a larger population do not simply disappear or switch themselves off. They remain in place, still requiring energy to operate, but are now shared among a smaller number of people. Picture a residential building where half the units have been vacated: the common areas still need lighting, the elevators still run, and the boiler still heats the building. The energy cost per remaining resident goes up, not down, because the fixed overhead of running that infrastructure is now divided among fewer contributors.
The same logic applies to commercial buildings, offices, schools, and public transport networks. Lower occupancy rates mean that the fixed energy demands of running large structures fall on a shrinking pool of users. Worse still, old and inefficient buildings and equipment, which in a growing and dynamic economy would be replaced with newer, more energy-efficient alternatives, tend to linger longer in a stagnating economy where investment is cautious, demand is uncertain, and the case for upgrading infrastructure is harder to make.
A declining population, paradoxically, can trap communities in outdated energy systems precisely when they most need to move beyond them. The carbon dioxide emissions data from Japan’s prefectures closely mirrored these energy consumption trends. Depopulation was not delivering the environmental dividend that campaigners might have hoped for. For those within Extinction Rebellion who believe that fewer people means a lighter footprint on the Earth, Japan’s experience over a quarter century is a genuinely sobering corrective.
Furthermore, the anti-natalist case for the environment often includes a vision of rewilding: as human populations retreat from the land, nature fills the void, forests return, wildlife recovers, and biodiversity flourishes. It is an appealing and romantically powerful image. But Japan’s experience complicates it considerably, and the complications matter. Research tracking biodiversity across 158 sites in Japan’s wooded, agricultural, and peri-urban landscapes—monitoring more than 1.5 million individual detections of birds, butterflies, fireflies, frogs, and more than 2,900 plant species over periods as long as 17 years—found that biodiversity losses continued regardless of whether local human populations were growing or shrinking. What is particularly telling is where stability was found: it was only in areas where the human population remained relatively steady that species richness and abundance also held relatively firm.
This matters because it inverts the assumption at the heart of anti-natalist environmentalism. The implicit logic of that position is that human presence degrades nature, and human absence allows it to recover. But the literature from Japan suggests something more complicated and more interesting: that a stable human presence, one rooted in traditional land management and agricultural practices, is itself a condition that supports biodiversity rather than undermines it. Nature, it turns out, does not simply bounce back when people leave. In many cases, it declines faster.
Japan’s rural satoyama landscapes—the traditional patchwork of farmland, managed woodland, and village settlements where agriculture meets the forest edge—have been losing population for decades. Yet rather than triggering a spontaneous ecological recovery, the withdrawal of human activity has produced unpredictable and often negative outcomes for wildlife. The crucial insight is that many species in these landscapes had not simply been tolerating human activity but had evolved alongside it, depending on the particular agricultural mosaic that humans had created and maintained over centuries. The paddies, the managed woodland edges, the cycle of cultivation and fallow—all of this constituted a habitat in its own right. When human management disappears, so does the habitat these species require.
The research found that depopulation was driving biodiversity loss primarily through its effects on land use, contributing either to urbanization, disuse, and abandonment, or agricultural intensification—none of which provides a refuge for the species that traditional farming landscapes had long sustained. Invasive species, freed from the pressures of active land management, move in and dominate, while fragmented plots of abandoned farmland rarely connect with forested areas in a way that would allow native wildlife to extend its range.
Legal and administrative complications make things worse. Japan’s land registration system is notoriously difficult to navigate, and in many cases, local authorities cannot identify who owns abandoned properties. Derelict buildings, unused car parks, and overgrown industrial sites remain standing for years, physically blocking the plant growth that insects, birds, and mammals depend upon. Estimates show that an area in Japan approximately the size of Austria is expected to be left vacant and unclaimed by 2030, yet this land is not being converted into a wildlife habitat. It is sitting in legal and ecological limbo.
The headline figures tell the story with uncomfortable clarity. Even as rural Japan has steadily emptied out, the number of species threatened with extinction has continued to rise, increasing by 13.6 percent in just three years between 2016 and 2019. The direction of travel could hardly be more unambiguous: population loss and ecological recovery are simply not moving together. Depopulation, on its own, is not rewilding. This conclusion is reinforced by the finding that in locations experiencing active population decline, the abundance and species richness of almost all organisms studied were falling at a steeper rate than in areas where human numbers were holding steady—a pattern that held consistently across birds, frogs, fireflies, and butterflies. The implication is not merely that depopulation fails to help biodiversity. It is that the loss of the people who have long maintained these landscapes actively accelerates its decline.
This reflects a broader truth about the relationship between land abandonment and biodiversity. When farmland falls out of use, it may be sold for urban development, converted into more intensively farmed monocultures, or left in a state of neglect that actively suppresses the natural succession of plant communities rather than enabling it. For woodland and rich native ecosystems to return, you need not just the absence of human pressure but also the active presence of ecological management, investment, and time measured in decades. Simply removing people from the equation is not sufficient, and in many cases it makes things worse, not better.
There is one more dimension to this debate that receives too little attention in environmental discussions, and it concerns the relationship between population size and human ingenuity. One of the more popular findings in social research is that larger populations tend to produce more ideas, more innovations, and more technological progress, simply because there are more minds working on problems and more resources devoted to finding solutions. These innovations are what economists call non-rival goods: a new clean energy technology or a more efficient design, once discovered, can be shared and applied across the entire global economy, regardless of who first developed it.
In practice, this means that a larger world population may actually accelerate the development of the technologies and solutions that environmental challenges demand, rather than impede progress on them. Researchers modeling the economic and productivity effects of population decline found that even modest benefits from the innovation advantages of a larger population substantially outweigh the small climate costs that the larger population generates.
The productivity gains from more people contributing to research, technology, and economic dynamism were found to be several times larger than the additional climate damages associated with the slightly higher temperatures that a bigger population might produce. This is not a marginal finding. It suggests that the anti-natalist prescription may actually be counterproductive: not only does reducing fertility fail to deliver meaningful climate benefits, but it may also slow down the very technological progress that the world needs to address its environmental challenges.
The people drawn to anti-natalist environmentalism are asking a genuinely important question. Human activity is placing enormous pressure on natural systems, and it is entirely reasonable to ask whether the sheer number of humans on Earth is part of the problem. The concern is legitimate. But the answer being offered—that having fewer children is a meaningful contribution to saving the planet—does not hold up to scrutiny.
Population decline moves far too slowly to address environmental challenges that demand action now. It does not reliably reduce energy consumption and may actually increase it at the individual level by making infrastructure inefficient and investment timid. It does not restore biodiversity and may actively harm it by removing the human stewardship on which many ecosystems quietly depend. As the evidence from Japan makes plain, it is not depopulation that protects wildlife—it is the continuation of careful, traditional human land management that depopulation steadily erodes. And in a world where collective resources and human ingenuity are needed to develop the technologies and solutions that environmental challenges require, a smaller and less dynamic population may leave humanity less equipped rather than better positioned.
The inconvenient truth for anti-natalist environmentalism is that the planet’s wellbeing depends far more on how people live, what they build, and how they manage the land around them than on how many of them there are. Population decline is not the shortcut it promises to be. The difficult work of building a more sustainable relationship with the natural world cannot be avoided simply by having fewer children.
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Lipton Matthews is a researcher and podcaster. His work has been featured in Mises, The Federalist, Chronicles, American Thinker, Epoch Times, and other publications. He is also author of Busting African Delusions: Institutions, Human Capital, and the Path to Progress.
