Overpopulation: Coming face to face with a global food shortage in the coming century
In 1972, a group of researchers published a computer model that could address a serious question for our species: how many people can live on Earth at once?
This model[1], built by a research group called the “Club of Rome” was used to investigate several scenarios by manipulating assumptions about how quickly we can curb pollution and population growth (among other things). Some of the scenarios found that human populations could level at a sustainable level. Others found that we overshoot our population level and then adjust down to a lower population level. Other simulations gave an extremely grim outlook, where we overshoot our optimal global carrying capacity — resulting in a collapse of the human population.
According to their model, they found that Earth can sustain a maximum of about 10 billion people. (see end of article to run the model yourself) And they’re not alone this number is echoed by scientists such as E.O. Wilson. In fact, a 2001 study of all population estimates by the UN found that, on average, studies calculated the carrying capacity of the planet to be 10 billion people.[2] The difference between the World3 model and others, is that the World3 model largely attributes this limit to a complex interaction of resources and failed policy interventions.
However, the problem of having a population that we can’t feed affecting population levels has been known for centuries. In 1798 a priest by the name of Thomas Malthus produced the first model of the problem. Malthus noted that resources like corn and wheat appear to grow linearly, while human populations grow exponentially.3 You can see a basic graph of linear (red line) and non-linear (blue line) growth below.
This is mathematical jargon to some, but it’s significance is an issue for humanity as it represents a species wide crisis: if our population grows faster than our ability to feed ourselves, our population will have to stop growing. So why aren’t we more worried about this?
Well, one possibility is that we don’t need to be worried because it won’t happen. In fairness, some research suggests that this can result in a natural “leveling off” of human populations. This research often cites the slower rates of growth in “modern” populations. For example, some — such as Dr. Hans Rosling — believe that we are nearing peak population for 4 reasons: 1) fertility rates fall as lifespans get longer; 2) women’s education means fewer children; 3) we’re getting used to low child mortality; 4) we’ve hit about the largest number of children we will have. Now, I have a lot of respect for these ideas, but none of them are causal arguments. They are all based on statistical trends, and we hope that these trends hold up in the future and that they hold for other cultures (most of the research done today is done in Western Industrialized Educated Rich and Democratic cultures like the US and Europe).[4]
Other scholars say that modern societies don’t have as many children because of effects such as “Cultural evolution”[5]. However, this paradigm is filled with issues as it simply views culture as an evolutionary process and has almost no verified causal mechanisms outside of psychology.[6–8]
Lastly, there is an issue with the assumption that the population is leveling. Namely, this assumption might just be the result of analyzing data that is but a blip on the radar of human population growth. Recently, the birth rates in the UK jumped 18%, while it hit a 33-year high in Germany last year, and US births, which appear to be tied to economic conditions, are on the rise. Generally, some research suggests that we are entering a baby-boom that may out-perform the one after WWII.[9]
So, what is the likely scenario? Well, the current best estimates say that we’ll be over 12 billion by 2100.[10] This is far over the 10 billion person maximum of most estimates. Currently however, we need to keep in mind that the amount the human population currently consumes is well over the amount the earth can sustainably produce — even though our population is currently at 7.5 billion. Typically, we use about 20% more than the Earth can sustainable produce. So if we want to ask how many people can the earth hold, we have to ask ourselves: how many people can the Earth hold given a specific lifestyle. If it is the American lifestyle, we’re done. The infographic here does a great job of exhibiting the trend.
If we all live like Americans, we need 5 Earths. We have 1.
This brings us to the real doom and gloom section. If we can only have a maximum of 10 billion people, and our lifestyle means we’ve already maximized our planet’s resources, we can safely say that we can really only sustain less than 8 billion people at current levels, and we are extracting resources at an alarming rate. If populations are expected to rise to over 12 billion, we have overshot that by 4 billion.
This leaves us with a devastating question: What happens to those 4 billion people?
Well, there are a few easy answers all of which are hard to face.
First, hunger. The model reflects some of the concerns of Malthus, but it is useful to note that Malthus did not account so much for population overshoots and collapses, he was generally noting that populations will level off when they reach the “carrying capacity” of their environment. However, in his recent book Collapse: How Societies Choose to Fail or Survive [11] Jared Diamond outlines some historical scenarios where cultures have overextracted from their environments before, leading to a collapse of their civilization. I highly suggest you read the book, if you don’t have time, here is his TED talk:
One example that is prevalent, is that of Easter Island, which is a remote island in the Pacific Ocean that sustained a flourishing culture for quite some time. They’re most well known today for the statues that are found on the Island known as the moai; they are large stone carved heads with bodies buried beneath the surface. This society overharvested its resources, put simply, they had too many people and not enough resources to sustain their society.[12,13] So, their society collapsed and their population adjusted to a level far lower than it had previously been. This was because the remoteness of the island did not allow for them to bring in new resources from outside. They were, effectively, a closed system. What the World3 model, and writers such as Diamond and E. O. Wilson and the United Nations, note, is that our planet is a similar system, and if we overshoot it’s natural boundaries, we will have to adjust our population accordingly.
This brings us to the most grim issue at hand: war. It is common knowledge that people fight over resources. Sometimes this is oil, sometimes land, sometimes water, but the picture being painted by the World3 model is that we will not have enough oil, land, and water to grow our food. In many societies resource scarcity has led to civil conflict, war, and other forms of inter-group violence.[14–17] We can expect to see a “tightening” of cultures as we begin this process according to the research on cultural tightness, which shows that cultures in some circumstances (such as war) are more strict18,19.
Perhaps we are already seeing a tightening? Extremist ideologies are more prevalent in the news these days than they were before. Political parties are polarizing and appear less tolerant of deviance. The rise of right-wing groups such as UKIP have resulted in the United Kingdom leaving the European Union. Countries like Russia and China are becoming more authoritarian. What can we expect throughout the world? We know that this tightening effect happens in the US[18] as well as in countries throughout the world.[19,20]
So, we’re faced with an issue long predicted, the question is how do we address it?
Note: if you want to play with the model, I’ve programmed it, available free to run in AnyLogic here: https://github.com/cogijl/World3
However, if you don’t want to install new software, it can be run in your web-browser here:
REFERENCES
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2. United Nations. World population monitoring 2001: Population, environment and development. (United Nations, 2001).
3. Malthus, T. R. An Essay on the Principle of Population. (J. Johnson, 1798).
4. Henrich, J., Heine, S. J. & Norenzayan, A. The weirdest people in the world? Behav. Brain Sci. 33, 61–83–135 (2010).
5. Newson, L. & Richerson, P. J. Why Do People Become Modern? A Darwinian Explanation. Popul. Dev. Rev. 35, (2009).
6. Lane, J. E. ‘Contemporary Evolutionary Theories of Culture and the Study of Religion’. J. Cogn. Sci. Relig. 3, 210–221 (2017).
7. Knudt, R. Contemporary Evolutionary Theories of Culture and the Study of Religion. (Bloomsbury Academic, 2015).
8. Gabora, L. Five Clarifications about Cultural Evolution. J. Cogn. Cult. 11, 61–83 (2011).
9. BCA Research. The Coming Baby Boom in Developed Economies. (2013).
10. Gerland, P. et al. World population stabilization unlikely this century. Science (80-. ). 346, 234–237 (2014).
11. Diamond, J. Collapse: How Societies Choose to Fail or Succeed. (Penguin Books, 2005).
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18. Harrington, J. R. & Gelfand, M. J. Tightness — looseness across the 50 united states. Proc. Natl. Acad. Sci. 111, 7990–7995 (2014).
19. Gelfand, M. J. et al. Differences Between Tight and Loose Cultures: A 33-Nation Study. Science (80-. ). 332, 1101–1104 (2011).
20. Uz, I. The Index of Cultural Tightness and Looseness Among 68 Countries. J. Cross. Cult. Psychol. 46, (2015).
