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.

Image from Wikipedia Commons. 

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 Greece, Italy, 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.

The population problem: should the Pope tell people to stop breeding like rabbits?

Image by Rakka.

In this post, I argue that overpopulation is a complex problem that has to do with human choices at the level of single families. It is not impossible that such choices will eventually lead to a stabilization of the world population at a sustainable level. It has happened in some historical cases, such as in Japan during the Edo period.


The population question arises strong feelings everytime it is mentioned and there is a general feeling that people will keep reproducing like rabbits unless something drastic is done to stop them. This position often goes in parallel with criticism to religious leaders and to religions in general, accused of encouraging people to reproduce like rabbits. Or, at least, to hide the fact that reproducing like rabbits is bad for the planet.

But is it true that people tend to reproduce like rabbits? And would they stop if someone, let's say the pope, were to tell them to stop? Maybe, but things cannot be so simple. Let me show you an example: Japan during the Edo period.

The population of Japan during the Edo Period (uncorrected data as reported by the Bafuku government). It shows how it is perfectly possible to attain a stable population in an agricultural society, even without "top-down" rules and laws. (data source, see also this link)


Note how the population has remained relatively constant for at least 150 years. It is a fascinating story, discussed in detail in the book "Mabiki: Infanticide and Population Growth in Eastern Japan, 1660–1950" by Fabian Drixler. Here is an illustration from the book:

Another impressive set of data: the net reproduction rates in Japan remained around or below the replacement rate during the Edo period, keeping the population constant for, indeed, something like one century and a half. It is also impressive to note how the reproduction rate literally exploded afterward, bringing the Japanese population from the ca. 25 millions of the Edo period to the present level of around 125 million, five times larger. Note also how rapidly the reproduction rate collapsed after the 1950s; it is a stark example of what we call the "demographic transition."

As we can see from these data, human reproduction strategies are much more complex than what you would imagine if you limit yourself to the biblical commandment "grow and multiply". The Japanese did NOT reproduce like rabbits during the Edo period. It doesn't appear that they were forced to reduce their birthrate by the government or by religious credences. Some famines are reported in Japan during the Edo period, but they couldn't have been truly disastrous, otherwise you would see their effects in the population curve. The population remained stable, it seems, mainly by "bottom-up" strategies at the level of single women or single families: contraception and, when that was not enough, infanticide.

So, what led the Japanese families to choose (rather than being forced) to limit their reproduction rate? There is plenty of scientific literature on the strategies of reproduction of various species, including the human one. The basic idea is that, in all cases, parents have a choice on how to employ their limited resources. Either they invest in having a large number of offspring (the "r-strategy", also the "rabbit strategy") or they invest in caring for their young until they reach adulthood (the "K-strategy" or the "Elephant strategy"). The choice of the reproductive strategy depends on the situation.  Let me cite directly from a paper by Figueredo et al. (1)

...... all things being equal, species living in unstable (e.g., fluctuation in food availability) and unpredictable (e.g., high predation) environments tend to evolve clusters of “r-selected” traits associated with high reproductive rates, low parental investment, and relatively short intergeneration times. In contrast, species living in stable and predictable environmental conditions tend to evolve clusters of “K-selected” traits associated with low reproductive rates, high parental investment, and long intergeneration times.

Humans, clearly, are more like elephants than like rabbits. The number of children that a human female can give birth to is limited, and it is normally a good strategy for her to maximize the survival chances of fewer children, rather than trying to have as many as possible. So, for most of humankind's history a family - or a single woman - would examine its environment and make a rough estimate of what chances their (or her) children could have to survive and prosper. In conditions of limited resources and strong competition, it makes sense for parents to maximize the health and fitness of their children by having a small number of them. It seems to be what happened in Japan during the Edo period: facing limited resources in a limited island, people decided to limit the number of their offspring, applying the "K-strategy."

The opposite is true for periods of abundant resources and scarce competition. When the economy is growing, families may well project this growth to the future and estimate that their children will have plenty of opportunities, then it makes sense to have a larger number of them - hence to apply the "r-strategy". The dramatic growth of population during the past 1-2 centuries is the result of the increasing consumption of fossil fuels. Everywhere, and in Japan as well, people reacted by filling up what they saw as open slots for their children. But with the second half of the 20th century, economic growth slowed down and people started to perceive that the world was rapidly filling up and that the economy wasn't growing anymore. They may not have perceived the depletion of mineral resources, but the result was obvious anyway. It was the "demographic transition," normally related to increasing wealth, but that we may also see as the result of a perception of the future that was seen as less rosy than before.

There are other cases of human populations that remained stable for some periods, so we may conclude that humans do not - definitely - reproduce like rabbits; except in some very special are rare conditions of history. Humans are intelligent creatures and, within some limits, they choose how many children to have in such a way to maximize their survival probabilities. The human population will tend to grow in a condition of economic growth, but it should tend to stabilize in static economic conditions. So, if we were able to stabilize the economic system, avoiding major wars and the need of cannon fodder, then the human population may well stabilize by itself, without any need for a "top-down" intervention by governments (or maybe by the Pope). Unfortunately, between now and then, there is a little problem called "overshoot" and stabilization at a sustainable level may be anything but painless. But if stabilization was possible on the island of Japan during the 19th century, why can't it happen in the larger island that we call "Earth"?


See also a post of mine titled "The cuckoo that won't sing: sustainability and Japanese culture"


1. Aurelio José Figueredo, Geneva Vásquez, Barbara H. Brumbach, Stephanie M.R. Schneider, Jon A. Sefcek, Ilanit R. Tal, Dawn Hill, Christopher J. Wenner, W. Jake Jacobs, Consilience and Life History Theory: From genes to brain to reproductive strategy, Developmental Review, Volume 26, Issue 2, June 2006, Pages 243-275, ISSN 0273-2297, http://dx.doi.org/10.1016/j.dr.2006.02.002

The coming "tipping point" of the climate perception: enough to solve the problem?

Recognizing the existence of world scale problems takes time. For instance, the above Google "Ngram" search show that world hunger was not recognized as a serious problem until relatively recent times. However, starting in the 1960s, considerable efforts were dedicated to increasing agricultural yields (the "Green Revolution"), with a certain degree of success. But was the problem really solved? Or was it only postponed - or even worsened - as a result of agriculture becoming totally dependent on fossil fuels? Something similar may happen in the future for the problem of climate change; it may be recognized, at last, but that doesn't mean it will be solved. 

Apart from a small number of diehard deniers, most people are perfectly aware that we have a serious problem with climate change. The public is just confused by a bombardment of contradictory statements pushed in the media, but probably that all what is needed to change the terms of the debate is just a push in the right direction. The pope's encyclic on climate - expected for this week - could do just that, reaching a "tipping point" in the general perception of the problem.

After the tipping point, a consensus may be reached that the idea that climate change doesn't exist or is not caused by human activity is not just wrong, but positively dangerous for society. Something comparable to such ideas as - say - that there is really no evidence that smoking causes cancers, that wearing a seat belt while riding a car is useless, and that crack is no more dangerous than coffee as a recreational drug.

Of course, we can't be sure that the pope's encyclic will have this effect; but, suppose it does, then what can we expect to happen? Optimistically, we could think that most of the work is done and that, from then on, something serious and effective will be done to stop global warming. Unfortunately, things will not be so easy.

How hard acting against climate change is likely to remain may be understood by considering another big and serious problem affecting humankind: world hunger. It had not been always recognized and it was only with the 1960s that it became a standard feature of our intellectual horizon. At that point, nobody would have dreamed to say that world hunger was a hoax designed by a conspiracy of scientists who wanted to keep their fat research grants to study a problem that doesn't exist. The debate was effectively over, but that, alone, didn't solve the problem.

Mainly, the attempt to eliminate world hunger was based on brute force; that is, on increasing agricultural yields. It was what we call today the "Green Revolution." As you know, the results of these efforts are often described in glowing terms, a triumph of human ingenuity over the limits of nature. It is also true, however, that the world hunger problem was never completely solved; it could not be if every increase in agricultural yield was matched by a corresponding increase in human population. And it may well be that the Green Revolution was not just a "non-solution," but something that made the problem worse by turning agriculture into an industrial activity wholly dependent on fossil fuels and artificial fertilizers.

Something similar could happen if we pass the turning point of the perception of climate change. The Google Ngram data, below, indicate that the interest in the problem is rapidly growing and we may be close to reaching the tipping point in perception that world hunger reached in the 1960s.

 
If we compare the result of the Ngram data for "world hunger" and for "Climate Change", we see that the perception of climate change trails that of world hunger by some 30 years. So, it may be high time for arriving to a general consensus on the climate problem.

The result, however, may not be as good it could be hoped. The sudden appearance of the dramatic reality of climate change in the mediasphere could lead to forget that the best (and probably the only) way to get rid of fossil fuels fast enough to avoid a climate disaster is to make them obsolete by means of renewables. So, we could see a mad scramble toward quick and dirty solutions; actually, non-solutions or solutions that worsen the problem.

One of these non-solutions is "geo-engineering" as it is normally described, that is spreading a reflective layer in the upper atmosphere. That would do something to reduce global warming, but nothing to avoid the acidification of the oceans and its regional climatic effects (e.g. droughts) are all to be discovered. Or think of carbon capture and storage: a desperate and expensive attempt to keep using fossil fuels ("eat the cake and still have it") by literally sweeping the problem under the carpet - where nobody can guarantee for how long it will stay. And what about biofuels? An excellent way to starve a great number of people in order that a small elite could keep using their expensive metal toys called "cars".


We all know that climate change is a wicked problem. Probably, in the near future we are going to discover how exactly wicked it is. Maybe the Pope himself would tell us not to expect miracles. We need to keep working hard at it, and we still have a fighting chance to avoid catastrophe.