Cassandra has moved. Ugo Bardi publishes now on a new site called "The Seneca Effect."

Monday, June 20, 2016

The end of the "population problem"? Another Seneca cliff in our future

Image from "National Geographic"

If the demographic projections by the United Nations will turn out to be true, the world population should reach over 11 billion people by 2100. Some think that it will be a disaster, others see it as a good thing as it would bring more economic growth. But is it really possible to reach such numbers? Can we really think that women would be so stupid to continue making children even in the midst of the crisis caused by declining natural resources and worsening ecosystem disruption? (unless the Pope himself were to tell them to stop)?

Yet, some models tell us the human population could keep increasing even after the collapse of the world's economy. There exists something called the "demographic transition" and it is a historical observation that may be extrapolated into the future. The data show a sort of "U-shaped fertility curve" that makes the poor and the very rich to be more fertile than those who are in the middle. When applied to the scenarios of "The Limits to Growth" of 1972, this idea generated a curious behavior, with the impoverishment of the population causing an increase in the birthrate that causes the population to continue increasing for a few decades after the collapse.

But, as it is always the case, extrapolating past trends into the future is extremely dangerous. In particular, it is at least improbable that the post-collapse world will be like running the same movie in reverse. The demographic transition has been observed to occur in growing economies, it won't simply change sign and reverse itself in contracting economies. To see how it works we can look at the demographic trends in Russia.

The increase in the death rate among Russians was not compensated by an increase in birth rates, as the demographic transition model would say. Russian women and Russian families reacted to a difficult situation by postponing or avoiding to generate new children, correctly understanding that these children would face very hard times and that it would have been impossible for their families to support them. Note the rapid collapse of birthrathes, a true "Seneca Cliff."

Now, I have a highly positive opinion of the intelligence of Russian people and, in particular, of Russian women. But I just can't think that people in other regions of the world would behave very differently. Those who maintain that people will make more children as they become poorer seem to assume that most people, and women in particular, are not more intelligent than an average rabbit. But, as it is always the case, extrapolating past trends into the future is extremely dangerous. While is true that most people are not very effective at the task of acting in order to benefit humankind as a whole, most people are perfectly able to understand what's good for themselves and their immediate families. And, in times of trouble, they normally react by planning in order to optimize the number of their surviving offspring. Humans apply what's called the "K-strategy" in reproduction: they concentrate the resources available on fewer children in order to maximize their probability of success.

Of course, we are dealing with phenomena of which we know little. After that the world's economy peaks, all the bets are off. But it may not be a coincidence that whole regions of the world, such as Southern Europe have started a population decline, despite having traditionally been demographically active. Among these GreeceItaly, Spain, and Portugal. Outside Europe, Japan has also started to decline, inverting a tendency of growth that had been ongoing from the 1920s. It is not yet possible to say if these inversions are to be understood as long-term trends. But, if this is the case, they are evidence that an economic crisis has nearly immediate effects on population.

A global population decline would have at least a positive effect in the sense that it would reduce the threat of climate change and the pressure on the ecosystem. But it may turn out to be a disaster if we enter the rapidly descending slope that I called the "Seneca Cliff". Will that lead to the "near term human extinction" that some think as a likely future? It cannot be excluded, but it is also true that there may be life on the other side of the cliff if we are smart enough to understand the future. It is up to us to prepare for it.


  1. Syria before the war: Here people kept breeding like rabbits, particularly the poor farmers who already received food aid. And then came the drought. And now we harvest their population overshoot.

    I hope this was not because women there were stupid like rabbits. It was the men.
    Recently Turkey's leader Erdogan declared contraception unislamic...

    1. Moreover, Erdogan wants a growing, and young, Turkish population as part of his drive for a new Ottoman-style supremacy. The young will also be easily indoctrinated in his new education system, which is being Islamised. If having large families brings social prestige and is rewarded in some way by the state, he will succeed in this. All quite mad. (If he reads this, he'll no doubt try to extradite me for trial for insulting Turkey.......)

    2. rapidly expanding populations burst outward to grab the resources of others

      or implode.

  2. Fertility declines not so much with wealth, but with industrialization, because in an industrialized society, it becomes difficult to achieve/maintain high social status when you have a lot of kids, and the cost of ensuring that each kid will also enjoy a high social status increases a lot faster than the increase in wealth associated with industrialization.

    That's the basic fault in the superficial interpretation of the demographic transition.

    In the Soviet bloc fertility declined even further than it had already done prior to 1989 because those were still highly industrialized societies, it just became even harder to maintain social status than prior to that.

    In the modern West, there are groups that have a lot of kids, in particular various religious fanatics, and they do so because they derive their social status from outside the general societal system.

    Crucially, the collapse will have two effects:

    1) deindustrialization
    2) a rise in religious fanaticism

    The first one is pretty much 100% certain, the second slightly less so but still extremely likely (it seems to have reliably happened in prior instances of societal collapse).

    Both of those will seriously affect the ways people approach the task of maximization of their perceived inclusive fitness through elevation of their social status.

  3. Humankind is no different to any other species of life. We are here to eat and procreate. Those linked forces are unstoppable other than by famine

    The rest of our "infrastructure"---our buildings, roads, mechanical devices, everything, should be seen as a form of window dressing that allows those two fundamental driving forces to be more efficient and productive. We look on on sophisticated civilisation and growing awareness particularly among women, as the factor that will ultimately control our population.

    But we should examine what birth control is, and how it works.

    That we are about to enter a period of (almost certainly permanent) industrial decline cannot now be in doubt, ie our factory system will no longer support our future expectations. Right now, we can buy pretty much anything we want, with very little work effort. That includes contraception, yet somehow the myth persists that it is ''education'' that controls population. No matter how educated a woman is, if cheap contraceptives cease to become available, she won't stop having sex.

    Population control and industrial complexity cannot be separated.

    Consider the processes necessary to produce the birth control pill and the efficient condom at almost zero cost.
    In a declining industrial environment, they will cease to become available.
    But the driving urge to procreate will continue, such is nature's directive.
    The ultimate result of that will be a surge in births and a fight for survival as population struggles towards some kind of peak (around 9bn maybe?---who knows?). This fits exactly with the notion that population will continue to increase for a few decades after collapse.
    With all other pleasure options removed, sex might be all that's left!!

    At at various future points (in time and geographically) starvation will begin to kick in and provide the ultimate form of birth control: Starving mothers do not ovulate. That is when population crash begins.

    we cannot say where and when of course. but without industry to provide support, it is inevitable as we approach the 9bn mark

  4. Ts ts, you seem to have a very low esteem of men and their caring not to have too many children. You are not alone whith that. Men are widely considered to be even more like rabbits, eager to make children whenever and wherever they can, only stoppable by concerned and thoughtful women (and sometimes even not that).
    I repeat a remark from an earlier comment, that the mere access to contraceptives for every - yes, couple - could probably stop the growth of world population tomorrow. (

  5. Ugo, you are right about humans being k strategists when it comes to reproduction, but in a collapse scenario the key factor I would imagine is a rise in infant mortality, not just overall death rates. This could induce people to switch to the 'r' strategy of producing more babies to have better chances of children making it to adulthood.

    Another observation I can make from the LTG charts is that population continues increasing post collapse due to momentum as death rates take awhile to spike dramatically, not so much the effect of birth rates increasing?

  6. I never for one moment believed the extrapolations of the United Nations' team of demographers with regard to future global human population. 11 billion people in 2100? Forget it! There are not enough natural resources to support this. What about topsoil? George Monbiot wrote an article not long ago in which he mentioned a source suggesting that the topsoil that people depend on for farming will be all but destroyed well before 2100. What about aquifers? Quite a few large fossil aquifers (Ogallala, some in India, Saudi Arabia, etc.) are being drained dry and there is nothing to replace them. Lester R. Brown pointed this out in a couple of books written in the last 6 years or so. What about the effectiveness of antibiotics? Plenty of evidence suggests that strains of bacteria are evolving defenses to all known antibiotics. What happens when an epidemic breaks out and only the strength of a person's unaided immune system lies between itself and death by infection? What about the destruction of fish stocks in the world's oceans? This continues unabated, with plastic pollution playing a destructive role.

    I do believe in statistical averaging but I don't believe in mindless unjustified extrapolation. All the systems analysis studies of which I am aware suggest a global human population decline starting far sooner than 2100. Jorgen Randers' book "2052" is the most recent such study. Randers' book has been criticized by Gail Tverberg (and others?) but that does not mean that it is worthless.

    A Seneca cliff model for future human population seems possible if population is truly propped up by industrialization, industrial agriculture and the electrical grid. Once those suffer any sort of major collapse, human population could easily go with it. Lots of people are afraid to talk about such things because they are very frightening. That does not mean that they aren't true.

  7. This situation in Russia is one thing. I think it is quite different among the poor in Nigeria, the Philippines, Pakistan or Venezuela.
    1. Consider that most male-dominated cultures demand women produce children (and even consider the recent remarks of Turkey's Prime Minister, Erdogan who claimed women need to produce at least three children, and Turkey is a relatively prosperous country, until recently trying to join the EU).
    2. But consider the poor women themselves (those you see photos of refugee camps in Somalia or Sudan with an emaciated baby and four other children all under 8 years old). They might feel more biologically fulfilled if they have 8 children, of which 6 die from starvation or conflict, than if they had only 2 children to begin with. Can this be another factor? [I am not saying these women have any choice, but they would at least feel they had accomplished their biological "duty."


  8. It's not a "Seneca Cliff".

    It's Reindeer on St. Matthew's Island.


  9. There will be a decline in human population some time after the collapse, but it won't be due to proper family planning.

    First, to have proper birth control, like Norman Paggett said, you need industry. If we no longer have industry, we will no longer have proper birth control.

    Second, birth control will only occur once humans, specifically women, can no longer produce offspring in such a situation. This usually implies starvation. Until famine sets in, women will continue to reproduce at a higher rate due to a lack of birth control.

    Third, those with the ability to reason, which see children possibly dying before attaining maturity, will switch to making as many children as possible with the hopes that they do attain physical maturity and mate before dying of starvation just as Yanzibit describes. This physical maturity can be as young as 12 if law and order break down. With younger people mating, the number of people able to produce offspring quickly will increase, thus increasing the number of children born like a snowball effect. That is assuming everything breaks down.

    In the end starvation, war, or disease will be the only things to cull the herd. When it does it will cull heavily.

    1. thanks---that's at least two of us who ''get it''

  10. Do we have any statistics on the current Russian birth-rate? A Russian friend told me, after a visit to Moscow last autumn, that he was struck by how many young families he saw, and how many pregnant women. The whole atmosphere was youthful and he said surprisingly happy, considering the effect of Western sanctions. A lot more positive in feeling that England and Iran where he spends most of his time. A very subjective impression to be sure.

  11. Bloom, Overshoot and die off all the rest is noise which includes unimaginable levels of misery as the die off takes place. I hope I'm not around to see it.

  12. Obviously a complicated question with lots of facets. However, I agree with Marc Bernstein that the resources simply won’t be there to support 11 billion people. The discussion gets lost considering local populations and narrow time spans when the big number under consideration is global population. Unless I’m mistaken, famine typically strikes locally and only temporarily, which is to say, until a new balance is found. But global human population trudged intransigently upward for millennia until it took off like a rocket once the energetic and caloric potential of fossil fuels was tapped. As Mark Bernstein points out, the two substrates required to amplify food production are soil and water, both of which are simply being used up at a frightening pace. So despite famine striking locally and temporarily in our past (e.g., Venezuela right now), a global famine is entirely foreseeable. Or use the term carrying capacity instead. Estimates for sustainable human population range around 500 million without fossil fuels -- our number prior to the Industrial Revolution. Without sufficient soil or water, I’d say far fewer still.

  13. Here seems to thrive a all-or-nothing approach - either full industry, or none. To me this is not well thought through, to say the least. Industry will probably shrink gradually and important industries - like the one which makes contraceptives - will never cease to exist, because they use relatively little amount of exergy and some organic chemistry, which can all well be supplied by mother nature.



Ugo Bardi is a member of the Club of Rome, faculty member of the University of Florence, and the author of "Extracted" (Chelsea Green 2014), "The Seneca Effect" (Springer 2017), and Before the Collapse (Springer 2019)