02 March 2026 – Is a Seneca Cliff for the human population on the horizon?
The first chapter of my book starts with:
“Today, those who discuss human population trends tend to split roughly into two groups: the catastrophists and the cornucopians. The catastrophists see population growth as a disaster that generates wars, famines and other ills. The cornucopians view it as a blessing that leads to continued progress and economic growth. Remarkably, both catastrophists and cornucopians tend to see the situation in similar terms; that is, they believe that population growth is the normal state of things, an unavoidable phenomenon that should be either stopped or encouraged. […]
But is growth really destined to continue? On this point, we may be facing a radical change that may make both the catastrophist and the cornucopian views obsolete. Human fertility is declining everywhere; it is called the Demographic Transition. Fewer children are born every year, and many couples are childless. The global population is still weakly growing, but as the people born during the “baby boom” of the mid-20th century (the “boomers”) march toward the Elysian fields, their loss will not be replaced by the younger generations. The trend is going to be reversed, and the global population is going to start declining.”
What I describe in my book is a major change in human history. Two thousand years ago, the Roman philosopher Lucius Annaeus Seneca observed that “increases are of sluggish growth, but the way to ruin is rapid.” He was speaking of human fortune, but the observation applies to populations: they grow slowly over centuries, yet can decline with startling speed when the conditions that sustained them erode. This is what I have called elsewhere the “Seneca Effect” — and there is no reason to think that human populations are immune to it.
When the growth of the human population became noticeable, about two centuries ago, Thomas Malthus thought that famines, wars and pestilences would put a cap on it. Fortunately, though, these factors are not playing an important role right now. But something is reducing fertility with the same effect on the number of human beings. What’s happening? The most common explanations point to social changes, and often fault women for their egoism in preferring their jobs and their careers rather than having children. But another explanation is rapidly gaining ground: chemical pollution. Plenty of evidence points to human-made chemicals causing havoc to the human reproductive system, both in males and females. And how about stress? There is evidence that it plays a role, too, in reducing fertility.
Whatever the cause of the decline, in principle, a gentle population decline could ease the pressure on dwindling resources and a heavily strained ecosystem, including our overheating atmosphere. A declining population may also change the perception of competition among states. Fewer people need less space, making the idea that nations have to exterminate their neighbors to gain space for their own populations is going to disappear into the dustbin of history, where it deserves to stay.
Yet, as for everything else, the devil is in the details. Granted, the world’s human population is going to start declining at some point, but when exactly? And who is going to move first in that direction? Today, practically all the industrialised countries (including China) are already seeing a population decline. Some are declining so rapidly to face serious risks of disappearing forever in a few decades. On the contrary, the Sub-Saharan African countries are still growing, some very rapidly. Even though the African population is showing evident signs of a slowdown, the peak may not appear before the end of the 21st century. If we extrapolate the current trends, we see that Sub-Saharan African countries could reach about 40% of the world’s population by the early 21st century, while the Northern countries could shrink to well under 20%.
If that’s the future, it is surely a turbulent future. So, what do we have to do? The simplest and most constructive answer is to restore ecosystem health, reduce chemical pollution and relieve the chronic stresses that modern civilisation imposes on human biology and psychology. That would restore the natural natality trends in the declining countries, gently taking them back to a condition of population stability or moderate decline.
Whether we will do that wisely, or stumble into darker responses—demographic engineering, forced natalism or worse—depends on how clearly we understand what is actually happening and why. That is what this book is about: not to sound an alarm, not to offer false comfort, not to scare anyone, but to look honestly at where we are, where we are going and what choices, if any, remain open to us.
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