As a nod to human supremacy, any time we hear the word “population,” it generally goes without saying that we mean human population, of course. Other such words include health, lifetime, prosperity, intelligence, wisdom, murder, pro-life, culture. To many in modernity, it makes no sense to discuss the murder of an animal, the wisdom in mushrooms, or a culture among crows. Such self-centered arrogance!
But where was I? Oh my—I got derailed before even starting. This post is about population of the human sort. In the 1960s, the rate of growth of human population appeared to be on a runaway ascent, enabled by the fossil-fueled Green Revolution. This alarming phenomenon prompted Paul Ehrlich to write The Population Bomb in 1968, warning of the inherent downsides in such an uncontrolled explosion of humans. But interestingly, the word “bomb” can also describe a dramatic failure, or falling flat—as in bombing a test.
In the past, my attention to population has been limited to the following points.
- The growth rate is grossly unsustainable, has accelerated historically, and is a reflection of temporary fossil fuels (Section 3.1 of my textbook).
- Despite lower birth rates, population growth in prosperous countries constitutes the largest population-growth-related resource burden on the planet (not poor countries).
- The demographic transition that worked in a past age for today’s “developed” countries is not really an option for the rest in a thoroughly-exploited world. Also, the inevitable population surge and resource demand accompanying the transition is an ecological double-whammy that Earth is not obligated to (and cannot) support.
These views are still valid for me, with an asterisk on the first point that will be the focus of this post. Last week’s post included a plot of human population growth over time. I was struck by the recent phenomenon of rapidly declining growth rates, which I had noticed in tables (pre-COVID) but had never seen in visual form. Here is the relevant graph in a larger format, straight from the United Nations’ 2022 population report and associated data.
Data (dots) and projection (green-dotted line) from the United Nations. We’ll get to the solid curves later.
The annual fractional increase, in percent, is shown as blue or red dots, depending on whether tracking the July 1 to July 1 annual increase (blue, centered on the year boundary) or January 1 to January 1 (red, centered mid-year). The green dotted line is the U.N. 2022 projection for how growth rate evolves (look how it changed its mind on the slope!). When it hits zero, in 2086, the population peaks at 10.43 billion. Or their model tells us so. I’ll get to the magenta and yellow curves in due course.
The rapid decline in population rates in recent decades is impressive. The first plummet transpired from about 1988 to 2005, dropping from 1.8% per year to 1.25%. After a decade’s pause, the downward trend resumed, lately averaging 0.85% per year.
Since human population plays a huge role in the global meta-crisis, what do we make of these trends, and how might they shape our future?
Dumb Extrapolation
I tend to be wary of extrapolations—because they often take an unsustainable and manifestly transient trend and pretend it can go on forever, even though it is unlike anything that came before and is in no way proven as a long-term normal. Obviously, shorter extrapolations are safer than longer ones. Since I spend probably too much time wondering what happens millennia from now (for which extrapolations are nonsense), it is a luxury to now think in terms of years and decades, where recent trends are more likely to hold. Extrapolation misgivings aside, what happens if we project the tail end of the decline in population growth rate?
Zoom-in of U.N. data (dots) and two fits to the recent pre-COVID trends.
First, we must discuss the recent impact of COVID, beginning in the first half of 2020. Looking carefully, the blue point at the year 2020 involves data spanning from 2019 July 1 to 2020 July 1, which is the first data point “contaminated” by COVID. I therefore work with points before this disruption.
I fit a linear curve to the last six points in the plot above, from 2017 to 2019.5 inclusive (indicated by yellow ticks), and a quadratic fit to a longer interval from 2009 (magenta tick) to 2019.5. The linear fit indicates an intercept to zero growth as soon as 2042, and the quadratic in 2033 (zero-intercepts are visible in earlier full-scale graph). Wow—that’s fast! I had no idea this was even feasible. Granted, we probably won’t follow either curve, exactly. The decline could ease up (or speed up), but it is fascinating to recognize that the pre-COVID course was on track to deliver us to the peak of human population on planet Earth as soon as the next decade or two! Who knew?
Starting from the last blue data point (which is already close to the extrapolation curves, having recovered from the COVID dip), if we indeed followed either of these curves toward zero growth, the world would peak at 8.8 or 8.5 billion people in the linear or quadratic cases, respectively. If this came to pass, color most of us (including me) surprised to not exceed 9 or 10 billion, and to find that we’re already 95% of the way to the peak. It’s not what we’ve been led to believe.
Yeah, But Really?
To be clear, I’m not claiming that this is what’s destined to happen. But I am now persuadable that population could peak in the first half of this century. The U.N. projection acquires a discontinuous slope from the pre-COVID dynamic, which seems suspect: where does that come from? I’ll mostly resolve this mystery in a bit.
A key reason to be incredulous is that recently-reduced birth rates across the globe represent an amalgam of many factors that are somewhat baked-in and hard/slow to change. From my years of interaction with college students, I sense that a big factor is skepticism on the part of young people about the promise of the future. We’re not in 1955 anymore, when projections came up roses. Young people today worry about climate change, war (including the nuclear variety, now pleasantly back on the table), declining prosperity, rising authoritarianism, and basically a world circling the toilet. Sure, many cling to faith in technology to save us, but that faith is justifiably getting thinner and starting to feel empty and internally desperate. So: wanna have some kids? “Maybe I’ll pass.” Perhaps relatedly: as many of the younger women I know are expressing in their lives, this seems like the best time in history to be gay. But my misgivings go beyond speculation and anecdote.
A few months ago I was pointed to an article by John Michael Greer (and later a related article), who I respect as a clear and independent thinker based on some of the things I’ve seen from him (his Elegy for the Age of Space was the bomb!). Here is a two-paragraph excerpt where JMG lays out some numbers [emphasis mine].
Let’s start with the demographic realities. It requires a total fertility rate of 2.1 live births on average per woman to maintain population at any given level; this is called the replacement rate. (That .1 is needed to account for the children who die before they reach reproductive age themselves, or who never reproduce for some other reason.) In 1970 the world’s total fertility rate was well above 5 live births per woman; now, it’s right around 2.3 and is falling steadily. Africa still has a total fertility rate of 4.1, down from nearly double that in the mid-20th century and still falling; but Asia and Latin America both have fertility rates of 2.0, North America (including Mexico) is at 1.8, and Europe is down to 1.6 live births per woman.
Some of the biggest countries are surprisingly far down the curve. India, the world’s most populous nation these days, is at 2.0, below replacement rate; China, second most populous, is at a stunningly low 1.1 despite recent efforts by its government to encourage births. The United States, third most populous, is at 1.7, and Indonesia, fourth, is at 2.1. Only with the fifth, Pakistan, do you get a rate that will sustain population growth, 3.3, and only with the sixth, Nigeria, do you get the kind of fertility rate the whole world had half a century ago, 5.1. Only six countries on the planet have a higher fertility rate than Nigeria does, while 187 have a lower rate. At the very bottom is South Korea, with a 0.8 fertility rate; if that stays unchanged, it will leave each generation not much more than a third the size of the generation before it.
I can’t argue with the numbers. But wait: something feels inconsistent. If global fertility rates have come down from above 5 (we’ll call it 5.1 for convenience) to 2.3, that’s 93% of the way to the 2.1 replacement (zero-growth) figure, yet the growth rate in the same period has fallen from just over 2% to just under 1%: less than 60% of the way down. Likewise, many of these countries, like India, are still growing their populations, despite a fertility rate that’s already below-replacement. How does this square up?
The secret is inertia stemming from the demographic distribution of ages, which has been youngster-heavy for the world as a whole. This means that the number of reproductive-aged people is on the rise in many regions of the world, so that even if the fertility rate had been at replacement rate (2.1) for the last 20 years, the total population would still grow as the more-numerous youngsters move into reproductive status. Eventually it would level out, but after a generational lag.
Age distributions across the world. This kind of figure is called a “population pyramid,” which tells us something about the historically “normal” bottom-heavy shape (i.e., it was very triangular several decades ago, and still is in Africa). It’s in the process of turning from a population pyramid into a “population spade” which metaphorically will dig the grave for population growth.
But a look at the global “population pyramid,” above, indicates that the bottom-heavy days are ending. Leaving out Africa, the world is already convincingly past “peak infant,” and even with Africa it’s teetering on being “demographically flat.” So: things are about to change. By the time the youngsters of today reach reproductive age, fertility rates will probably have fallen further—continuing the trend of the last decade seen in countries the world-over—resulting in a convincing population contraction. It’s essentially locked in, and a matter of waiting out the delay.
Incidentally, the downward trend in the rate data (data points in first two graphs) already folds in the dynamics of declining fertility and changing demographic realities: it’s the final result of all these real things, so that the trend reflects the aggregate effect, including demographic inertia. The “pyramid” gives us a sneak peak at what lies ahead, providing no reason to expect much in the way of a rally/surge in the coming decades.
Says Who?
Many of the “official” projections for global population still show a lazy peak and in some cases stabilization above 10 billion people near the end of the century. I wondered how much of this is motivated by belief, so that models of future fertility rates are chosen for “sensible” and politically palatable results rather than trying to predict underlying dynamics. I initially wrote the last sentence in the present tense and then converted to past tense after looking for answers and stumbling across the following jaw-dropping graph (extracted from the 2022 UN model’s giant spreadsheet, but also here). The figure below reveals that the United Nations’ expert “model” appears to have picked an arbitrary long-term fertility rate out of who-knows-where to which all regions asymptote, abruptly abandoning their current declines to head for theory-land! I’m honestly a bit aghast.
U.N. Total Fertility Rate data (pre-2020) and projections (post-2020). Like the Nazgul who suddenly drop whatever they are doing to race to the Ring, the U.N. model forsakes recent trends to race toward a steady asymptote—around 1.7—seemingly pulled out of thin air. “Latin” includes South America, Central America, Mexico, and the Caribbean. N.A. stands for Northern America (mainly the U.S. and Canada).
I mean: look at all those artificial kinks at 2020, slapping the world out of its fairly universal (pre-COVID, note) downward trends! “We interrupt this program to bring you a special announcement from the land of wishful thinking. This station powered by fantasy.” The single-parameter “model” all boils down to this unsupportable guess at a magnificently stable and universal long-term fertility rate, leading to the green dotted curve in the first figure above. I hope you can better appreciate my skepticism now.
The U.N. model contains plenty of sophistication and granularity in projecting how each country and region evolves toward this imaginary and powerful magnet, based on a boatload of demographic specifics. But the end result really boils down to this single element of asserted imagination. It’s sort-of like painstakingly modeling the motion of all the planets in the solar system under a model where gravity is 60% as strong as it actually is: one can go to tremendous effort to incorporate every detail and interaction for every planet—but why? It’s guaranteed to be wrong based on faulty assumptions, even if otherwise perfectly executed in an almost super-human attention to detail.
They do acknowledge uncertainty in their choice and explore different scenarios that amount to varying the “universal attractor” fertility rate, but still force the world to promptly flock toward this stable happily-ever-after endpoint. Their 95% confidence intervals correspond to somehow knowing the final universal fertility rate (as if that’s even a thing) to about ±0.2, although I have perhaps no more than 10% confidence that their basic premise is right (an example of statistics conveying false confidence based on highly dubious underlying assumptions which are implicitly 100% right, somehow). I get it that predicting the future is hard, but it’s worth appreciating just how thin the U.N.’s projection is. My high-odds prediction: the real world will ignore this bit of theory and continue to exhibit unpredictable dynamics in actual fertility rates.
Other projections (like in this report) acknowledge declining fertility trends and are slightly less timid about projecting population reduction in the next several decades. I also saw a New York Times article in September 2023 expressing horror at the prospect of peak population (10 billion) late this century and the subsequent inexorable decline. The author laments the lost opportunity of humanity’s blessed ascent to greater godliness, which is classic human supremacist claptrap. I ignored most of the wailing, focusing instead on the projections, and was struck by the simplicity of models that just lock in various current “developed” fertility rates ad infinitum—resulting in an unrealistic extinguishing of humanity in a few hundred years. Sure, I was glad to see acknowledgment that the present state of affairs is not permanent, in that population would peak, decline, and bring radical change to the world. But I could not take the centuries-long single-value extrapolation results at all seriously, and dismissed the piece accordingly as it made no attempt to acknowledge changing underlying dynamics. The point of all this is that the prospect of population decline is starting to get some sporadic attention.
At this stage, I want to remind folks of a familiar 1972 work called The Limits to Growth, whose models almost invariably showed a population peak and decline mid-century (a bold prediction 70-plus years out that we still can’t say is wrong!). In order to coax their model into stabilized population in the face of all the inter-related factors, they had to work really hard and concoct seemingly impossible political scenarios—which is another way to say that a steady-state, non-peaking population is probably just baseless fantasy, succumbing to the ubiquitous conceit that we’re in control of our destiny and will “figure things out.” Below are two model runs from the Limits to Growth work: the default “standard” run (business as usual; BAU), and the one that doubles resources (BAU2). Both show population peaking and declining before 2050. Efforts to track progress (e.g., Herrington, 2020; see associated Resilience article) point to the BAU2 run as the one we are most closely following.
Two model runs from the Limits to Growth (from Gaya Herrington’s 2020 paper, with following attribution: Adapted from Limits to Growth: The 30-Year Update (p. 169, 173, 219, 245), by Meadows, D. H.,Meadows, D. L., and Randers, J., 2004, Chelsea Green Publishing Co. Copyright 2004 by Dennis Meadows. Adapted with permission).
Also worth pointing out is a very simple model I created in a post called Finite Feeding Frenzy, based on the premise that most of the present human population is propped up by non-renewable fossil fuels that are critical for industrial-scale agriculture. As fossil fuels inevitably phase out, it should not surprise anyone to see human population follow. People in our culture resist the idea that godlike humans are subject to mundane realities like food, but what can I say: we are no more and no less than biophysical beings. In terms of net energy, a compelling argument can be made that we are already past the peak and might expect population to reflect this fact once the delay mechanism (aging to reproduction) has caught up in a few decades. Indeed, fertility rates in much of the world are already below replacement and marching down, still.
What’s Next?
Okay, so let’s say that a global depopulation trajectory manifests in the second half of this century, as I am now more inclined to believe. What does it mean? How does it interact with modernity’s fate, for instance?
As if I know!
But, let’s think about it. Do you think people will notice? Do you think it will be newsworthy? Am I kidding? It’s about people! It will be huge news and likely dominate conversations around the world for decades! Nothing like this has ever happened outside of plagues, which people probably also noticed and talked about. Depending on what narratives emerge (odds are, more than you can count), I can imagine a prevalent theme about impending decline with no end in sight. After all, infinite extrapolation is one of our favorite games. Older generations will panic that the utopia they imagined we were on track to achieve is threatened, and beseech the young to get busy. But younger folks (whose self-possessed attitudes count more when it comes to reproduction) might well see things differently, already accepting that the world envisioned by Boomers is a failure and a farce, resentfully wanting no part of it. Efforts to get them to make babies seem unlikely to be persuasive.
My Best Guess?
If I don’t like the unimaginative “theory” behind the UN model (which can be summed up as: TFR → 1.7), then what do I think is in store? I’ll take a stab without a crystal ball (although in parallel I have tooled up a reasonably sophisticated demographic projection tool so I can investigate consequences of different assumptions—maybe to be explored in a future post). I imagine that whatever has been driving the current plummet in fertility since about 2015 is not going to abruptly stop, as I don’t perceive any game-changers in the air at present that would increase fertility. I would not be surprised if the downward slope moderates, but for that matter I can also imagine scenarios in which it picks up steam. In any case, it seems rather plausible that global population could be in decline by 2050, setting off unpredictable consequences.
I’ll skip the intermediate reaction for now and zip to the farther future. I don’t imagine the present decline in fertility rate to be monotonic, which mathematically leads to near-term extinction. I think it rises again, and probably back up to the replacement neighborhood as population (approximately) stabilizes at a much lower value. What I say next will probably strike many as a disastrous outcome, but after modernity winds down we can probably expect death rates and infant mortality to rise, and life expectancy to fall. As an aside, and stated in the extreme, human immortality—which does not exist anyway—is obviously not what makes the world great and amazing. I hope we can see our way to acceptance that death is natural—not an evil to be defeated—and a fair price for the privilege of living in a biodiverse, ecologically sustainable “paradise” in an otherwise empty and hostile space. Since the current low levels of mortality go hand-in-hand with ecological devastation and a doomed modernity, their embrace is itself a problem (yes, I’m really swimming against the current now!). So, in the farther future—likely lacking medical birth control—I can envision higher birth rates balanced by higher death rates for a reasonable and comfortable stability in right-relationship to the community of life. Earth back in balance. Good, right?
How we get from here to there is likely to be turbulent and is difficult to predict. Rather than accepting and adapting smartly, the transition may be marked by violence and war, and/or by simple starvation as complex food production/distribution networks fragment. Either way, I would not be surprised if mortality rates rise significantly during the transition, making the population decline sharper than any mainstream model is courageous enough to explore. Meanwhile, birth rates may stay low as a result of turbulence, or could conceivably experience an uptick as birth control becomes unavailable and young couples seek after-dark entertainment when screens are no longer prevalent.
In any case, smooth convergence to a “final” fertility rate as modeled by the U.N. is about the last thing that I imagine will actually happen. Roller coaster is more our jam.
Repercussions
Presently, “healthy” economies depend on growth. Decline is no bueno, in political and economic sectors. A horizon of opportunity and expansion becomes a horizon of empty buildings, closed shops, shuttered schools, withering supply chains, and generally scaled-back lifestyles. Economies also depend on optimism and the idea that tomorrow will be bigger than today. Take that away, and what happens to investment? We’re talking about an event that makes the Great Depression look like a month-long visit of the in-laws: unpleasant, but you can have some faith that you’ll get through it—even if it lasts longer than seems reasonable. In the population decline case, we’re confronting the possibility of a generations-long—or even indefinite—phenomenon during which institutions, supply chains, and industrial food production/distribution falter. When the longstanding normalcy is shattered, when food security is a thing of the past, and when no credible reprieve is in sight, how will people view procreation? Birth rates will never drop to zero, but all things considered population growth also seems unlikely to rally amidst disorienting uncertainty.
One bright spot is that because different countries are at different stages of demographic development (age distributions, fertility rates), a handful already appear to be past their peak, including China! The game has already started, and should pick up steam. Thus, well before global population peaks, we’ll have example after example of “early adopters,” and as such possess convincing evidence of the global peak to come, and furthermore may draw useful lessons from the outcomes. These “test runs” may help soften the experience globally, by allowing others to avoid repeating mistakes in accepting and adapting to the new reality..
In the past, I assumed that modernity would fail (bomb) under the weight of resource shortages, technological disappointments, exploding debt and financial collapse, ecological/biodiversity collapse, resource wars, or most likely a swirling, confusing mix of all of the above. Now, I can imagine the depopulation dynamic acting as a leading agent in the great story of how humans slough off modernity, giving the more-than-human world breathing room to recover. In some ways, this is the gentlest, most humane exit strategy, and may represent a smarter-than-expected proactive reaction to the limits that are increasingly obvious: we’d be dodging the worst by deflating the balloon before it pops.
The juggernaut simply runs out of steam, as people stop believing in the fantasy—in reaction to hollowing institutions—and get on with inventing other ways to survive that are more locally-reliant and place-specific. No more one-size-fits-all, top-down approach to living, but a fragmented diversity of living arrangements that go back to being tested on the grounds of biophysical/ecological viability in relation to the community of life. The economy as we know it will gasp and die, but people will find they’re made of sterner stuff , based on a much older genetic heritage.
As population bombs, perhaps there’s no explosion, but a whimper of modernity as the larger living world finds its voice again, accented by human song.
