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I keep reading more and more comments about overpopulation on the social media. It is not just an impression: the trend of increasing interest in population matters is visible in Google Trends. Still weak, but it is there.

It is puzzling how the question is returning. It had disappeared from the media after it had been popular in the 1970s, at the time of the first “The Limits to Growth” study. At that time, there were less than 4 billion people and that was viewed as a huge problem. Then, somehow, it became unfashionable to mention overpopulation, just as it became unfashionable to consider “The Limits to Growth” as anything more than a completely wrong study written by people not smarter than Chicken Little (it wasn’t the case).

Now, with twice as many people – 7.6 billion humans – we see a return of the idea that – really – there may be a little problem of overpopulation. Humans are so many that they are appropriating a larger and larger fraction of the ecosystem. That means less and less space for other species which are, indeed, fast disappearing. When you read that, in a not too remote future, the only large animal left on the Earth will be the cow, well, that makes you think.

A specific streak of the discussion is that overpopulation is not just a problem, it is “the” problem. If we could reduce the number of humans, it is said, then all the other problems, pollution, global warming, resource depletion, would all become automatically much more manageable – if not completely solved. This opinion is often accompanied by statements that the reduction must be accomplished by fair and nonviolent means: voluntary birth control only. That doesn’t prevent some people from accusing the “Greens” or the “global elites” of planning the extermination of most of humankind. Others see an evil plot in the growing population, accusing the powers that be – governments, religious organizations, the Illuminati, the gnomes of Zurich, or whatever – to be engaged in a global conspiracy aimed at hiding the dangers of overpopulation.

Personally, I am not too worried about human overpopulation, nor about these pretended evil conspiracies. Not that I think that there aren’t too many people around. The point, I think, is that if today overpopulation is a problem, and it is, it will solve itself rather quickly (although not without pain). No need for evil elites plotting extermination, nor of well-intentioned activists teaching the poor how to use condoms. The system itself will cause the human population to collapse.

The current 7.6 billion people on the Earth are alive in a very special moment of human history. It had never happened before and it is unlikely that it will happen again the foreseeable future. So many people are alive today because there exists a sophisticated and incredibly complex system engaged in keeping them alive. The stupendous transportation system that carries food all over the world is powered by fossil energy and controlled by the financial and political system we call the “globalization.” As long as fossil energy and globalization exist, people will be fed and population may continue growing.

But for how long? The whole system is under heavy strain because of depletion and pollution. Natural resources are more and more costly to produce while fighting pollution – also in the form of global warming – is becoming more and more expensive. A new major financial collapse will be sufficient to disrupt the transportation chain which ships food it all over the planet. Without this system, the food will rot where it is produced and the people at the other end of the chain will starve. It will be the Seneca Cliff of the whole system, including the human population.

There are other factors which may also work in the direction of reducing the human population. Think how interesting are the 400+ million tons of human flesh existing today for predators such as viruses, bacteria, and assorted parasites – we are their prey and we are rapidly becoming an abundant and easy prey. And there are more possibilities, from reduced fertility caused by heavy metal pollution to the old-fashioned, but always effective, large-scale wars. (1)

Recently, I published a paper on the Journal of Population and Sustainability where I looked for some historical examples of how populations (not just human ones) crashed down in the past. I found more than one reason that can lead to an abrupt collapse. An especially poignant example is that of the horse population in the US. It experienced a fast when the horses went down from some 27 million in 1920 to about 3 million in 1960. No one called for the extermination of horses but they had lost their economic value – replaced by machines –  and so they were not cared for anymore and not even allowed to reproduce. And that was the Seneca Cliff for horses.

Why not a similar cliff ahead for humans? They, too, have lost their economic value, being replaced by machines. You say that humans are not horses? Sure, but think about something: who decided the fate of horses? And who decides the fate of humans? You get my point, I guess. With humans rapidly becoming technologically obsolete, there would be no need to wait for an energy cliff to bring down civilization as a whole before seeing their numbers radically curtailed.

So, you may like to read my paper in the Journal of Population and Sustainability.

(1) I know that Paul Ehrlich cried wolf too early about population collapse, in 1968. Sure, that means population will keep growing forever, right?

(2) To explain this point, the fate of horses in the US

Ugo Bardi teaches physical chemistry at the University of Florence, in Italy. He is interested in resource depletion, system dynamics modeling, climate science and renewable energy. Contact: ugo.bardi(whirlything)unifi.it. He blogs at Cassandra’s Legacy where this article was first published.

One Comment

  1. Finally, an essay that places population in perspective but rather than a numbers drop, it should have emphasised the rational planned economics.