This essay is adapted from It’s Debatable: Talking Authentically about Tricky Topics, published by Olive Branch Press.

Here’s a question almost no one wants to talk about: What is the sustainable size of the human population, at what level of aggregate consumption?

Why are so many people afraid to discuss something so essential? Because the question suggests we need to impose limits on ourselves, something modern societies are not good at and most people don’t want to consider.

No one has a definitive answer, of course, about the number of people or our things that would make possible a decent human future. But given the multiple cascading ecological crises we face, it would be prudent to assume that we should move in the direction of “fewer and less”—fewer people consuming a lot less. That conclusion seems obvious to me, today.

The qualifier, “today,” reminds me of how easy it is for all of us to avoid harsh realities.

A couple of years ago I was talking to a friend about why so many people on the left side of the fence—my political home—refuse to acknowledge that imposing limits is necessary. Standard left dogma is that the problem is not population and consumption but capitalism—if the world’s resources were distributed equitably, there would be enough for everyone. This dodge—it’s economics not population and consumption—is a serious deficiency of left analysis, I told my friend, because it avoids coming to terms with the biophysical limits of the larger living world of which we are but one part.

Brief uncomfortable pause.

“When I asked you about population a long time ago,” my friend said, “you told me that it wasn’t important. Your answer was that the problem was capitalism. You gave me what you are now calling left dogma.”

Another brief uncomfortable pause.

I had two possible responses. I could construct some tortured explanation of how my past comments were more nuanced and that what I had really meant was …

I spared us both that torture and agreed. Yes, I said, you’re absolutely right. For a long time, I repeated that dogma, even though I was never sure it made sense. I didn’t challenge the claim because I hadn’t read widely enough or spent enough time thinking about the question, and so I said what people of my political leanings were supposed to say. I stuck with the herd. I wanted to be seen as a good leftist, and that was lazy. Reasonable people can disagree about the issue, but accepting dogma to avoid critical thinking is bad intellectual practice and contributes to bad public policy. In other words, I may be wrong about my conclusion today, but I definitely was wrong simply to repeat the party line for so long.

Here’s how I think about these questions today.

First, concern about what are typically called “environmental problems” is widespread, of course. But rather than focus on specific threats, such as rapid climate destabilization, we should recognize that any single ecological crisis is a derivative of overshoot—too many people consuming too much in the aggregate. The highly skewed distribution of wealth is morally unacceptable, but as a species we are living collectively beyond the carrying capacity of the ecosphere.

Here’s a simple timeline from my life to help us grasp the scale. My father was born in 1927, when the world population was 2 billion. In 1974, the midpoint of his life, we hit 4 billion. When he died at the end of 2022, the world population was 8 billion. In one person’s lifetime, just three generations, the world population doubled and doubled again. That’s unprecedented, as was the increase in energy consumption. In the 20th century, the average annual per capita supply of commercial energy more than quadrupled. That consumption also is marked by inequality; at the end of that century, 10 percent of the world’s population consumed more than 40 percent of commercial primary energy, and the bottom 50 percent of the population had access to about 10 percent of the energy.

Also unprecedented are the effects on the ecosphere of all those people consuming all that energy. Virtually every ecosystem on Earth has been degraded by this level of human habitation. A 2019 UN report shows that three-quarters of the land-based environment and two-thirds of the marine environment have been significantly altered by human actions. Such studies now appear regularly in the news. “A ‘Crossroads’ for Humanity: Earth’s Biodiversity Is Still Collapsing” described a 2020 report from the UN Convention on Biodiversity that reminds us species extinction is not only unfortunate for the species that go extinct but also threatens humanity’s food supply, health, and security. A study published the following year concluded that only 3 percent of the land surface is “faunally intact.”

Politics and economics have yet to adapt to this. In 2022, a respected think tank warned that “To Prevent the Collapse of Biodiversity, the World Needs a New Planetary Politics.” Even if one’s focus is on the economic bottom line, such as the folks at the World Economic Forum in 2023, it’s hard not to notice: “Terrestrial and marine ecosystems are facing multiple pressure points due to their undervalued contribution to the global economy as well as overall planetary health.”

The rate of population growth is slowing, due in large part to advances in the status of women and education of girls, but growth is predicted through this century, peaking at perhaps 10 billion. Slowly slowing growth is of little comfort. Even if we were to reduce per capita consumption worldwide, especially in affluent countries, all three potential population scenarios pose problems.

• A growing global population poses serious challenges for humanity by intensifying the consequences of overshoot. That means greater social instability and more rapid ecological degradation.

• A stable global population poses serious challenges for humanity, since we are already in overshoot. That means, at the very least, existing levels of social instability and ecological degradation can be expected to continue.

• A shrinking global population poses serious challenges for humanity, given that the world economy is built on overshoot.

By the 2020s, politicians routinely were raising alarms about how falling birth rates in affluent societies raise the elderly dependency ratio (the ratio of working people to older folks; a high dependency ratio means that fewer young people carry a heavier burden to support those who are not economically active). Slowing population growth risks the economic growth on which virtually all of the world economy is based. Even China, once the country working hardest to restrict births, is concerned.

Many of my friends and allies in progressive movements reject any concerns about population, dismissing them as neo-Malthusian, as if Thomas Malthus’s inaccurate predictions about food production in the 19th century mean we need not worry about the question today. Many on the left avoid the question because of the racist and ethnocentric ideologies that have been associated with concerns about overpopulation in the past, and unfortunately continue today in what is being called the “ecofascist” movement, defined as “a kind of environmentalism that advocates violence or the exclusion of some groups of people due to their race or class—or both.” That doesn’t mean there is no overpopulation problem, only that we must be careful to avoid bad analysis and ugly politics, a task in which Population Balance is leading the way.

The problem of too many humans should not be blamed on poor or non-white people in the developing world. It’s a problem created by the trajectory of human history, the result of our ability to get at more and more energy-rich carbon with new technologies, leading to ecological degradation resulting from too many people consuming too much overall.

No one can pull off the shelf a quick-and-easy plan to reduce human aggregate consumption by reducing our numbers, our appetites, or both. But the fact that we don’t know how to impose limits on ourselves doesn’t mean we don’t have to do it. And the only way to come up with a plan is to stop avoiding the issue.