It is often claimed – especially by environmentalists – that there is a human overpopulation problem: there are too many humans, or the number of humans is growing too rapidly. I will argue for the controversial, opposite claim. Of all animal populations on this planet, the human population is perhaps the only population that is not overpopulated. The non-human animals, on the other hand, face a real overpopulation problem. The claim that there is a human overpopulation problem, and that non-human wild animals do not have this overpopulation problem, is very far from the truth.
Let’s analyze this claim about human overpopulation. How can we know whether there is an overpopulation? Overpopulation is defined as a population that is too big or grows too fast. A crucial word in this definition, is the word ‘too’. This word makes the definition ambiguous and vague, so we must be more precise. It is a normative concept: it refers to something bad. If we think about overpopulation as a problem, what kind of bad things are we really thinking about?
Traffic jams or long rows at the cash desks in the supermarkets are not the real issue here. When people are worried about overpopulation, they are thinking about more serious issues, such as death and disease. They expect increased levels of mass-starvation, new pandemic diseases, more war and violence, a collapse of civilization. This all comes down to: a lot of people dying at a young age, because of a lack of resources (e.g. food or shelter) or increased negative externalities (e.g. pollution or contagious diseases), such that the population size will suddenly decrease by say more than a factor two (i.e. the size will more than halve).
Before we can answer the question when a population is overpopulated, we need to solve a few more technical details. First, to what does the population size refer to? Suppose there is a planet with a population of extraterrestrial aliens on the northern hemisphere. For the first ten years, those aliens are overexploiting the northern hemisphere, such that its ecosystem completely collapses after ten years. All the aliens at the northern hemisphere die, but in the meantime the southern hemisphere becomes habitable and the same number of new aliens are born there. After ten years of overexploiting the southern hemisphere, the ecosystem collapses, the population dies, but the northern hemisphere becomes habitable again and new, northern aliens are born. According to the above formulation of overpopulation, even if overexploitation results in high premature death rates, the total planet is never overpopulated, because the total alien population remains constant over time. However, there is clearly an overpopulation, when we focus on a single generation of aliens, or all the newborn aliens in a short time period.
Second, overpopulation can refer either to the population size or the population growth rate. When we look at a single generation as the population, there is no growth rate. However, in this case, we can consider the reproduction rate instead of the population growth rate. If too many new individuals are born, there can be overpopulation.
Third, overpopulation is related to the premature death rate: the fraction of a population that dies prematurely. Here, I will define a premature death as either a death before the individual enters reproductive age, or a death before the individual reaches an age equal to half the age of the oldest individual in the population. For example, the oldest human died at an age of 122 years, so for the humans of her generation, I consider a death before the age of 61 years as a premature death.
Considering the above, I will define overpopulation very specifically as a situation where reproduction becomes so large that it results in a lack of resources or increased negative externalities, leading to a premature death rate that is so high or will become so high that the population size of a newborn generation will suddenly decrease with at least a factor two. This definition is very concrete and measurable. If you prefer another definition of overpopulation, then you can come to other conclusions and hence the title of this article can become misleading.
There is no human overpopulation
Now we can finally answer the question: is there a human overpopulation? The fact is: the premature death rate amongst humans is decreasing. Starvation and deadly diseases are decreasing. Also war and violence are decreasing. Roughly 1 in 26 children die before reaching age five. More than three quarters of a newborn generation of humans survive to age 65. Consider the countries with the highest infant mortality rate: Afghanistan, Somalia and the Central African Republic. In those countries, roughly one in ten newborn children die in the first year of their life (i.e. with a lifespan that is hundred times shorter than the life expectancy of a healthy human). This is not yet halving the human populations in those countries: the average life expectancy in those countries is more than 50 years. If such low life expectancy is considered an overpopulation, then the whole world was hugely overpopulated in the 19th century.
What about the future? Can we still feed all humans when we are overexploiting the Earth, when we face climate change, pollution, a nuclear winter after a world war, a super weed, or another catastrophic disaster? Technically speaking, it is possible to feed everyone, even after global catastrophes that destroy crops or block sunlight for years. If you want to help making the future human population more resilient against such extreme catastrophes, you can support an organization like ALLFED: the Alliance to Feed the Earth in Disasters.
There is non-human animal overpopulation
Let’s compare these numbers with the real overpopulation: wild animal populations. In nature, if an animal survives till reproductive age, it can give birth to more than ten and sometimes thousands of offspring. Of course, if all those offspring would survive and reproduce, we would see a huge population growth in nature. Also, almost every adult animal had more than ten siblings. Of course, If all those siblings would still be alive, we would see huge animal populations. The fact is: more than 90% of all the newborn animals die at an early age. The premature death rate amongst wild animal populations is higher than 90%. That is why we don’t see the huge population growth and all the siblings of all those wild animals. Even without human interference in natural environments (even without anthropogenic climate change, pollution, land degradation, deforestation,…), the wild animal premature death rate would be so high.
As mentioned above, every new generation can be considered as a population. If we look at animals, we see that within each population of newborn animals (e.g. the animals born past spring), more than 90% die prematurely. Each population of newborn animals more than halves. Those animals didn’t have enough resources such as food which resulted in starvation and increased levels of competition, and they generated more negative externalities (e.g. infecting each other with deadly diseases). Looking at the population of fish for example, we see that resource scarcity resulted in predation, where some fish eat other fish in order to survive. Looking at the definition of overpopulation, it becomes clear that non-human animals are clearly overpopulated. It is an eternal overpopulation, like the alien planet, where each new generation is drastically thinned out.
What about the growth rate? Humans are a unique population, because they have a fertility rate of 2,4 children per woman, reaching 2 by the end of the century. No other animal population achieves this. It means human population growth will stop. Non-human animals on the other hand, have very high fertility rates: an adult female animal can give birth to more than ten offspring, and only a few of those offspring survive to adulthood.
These high fertility rates are the real overpopulation problem. This reproductive strategy of wild animals is the root cause of most of wild animal suffering. So if you are concerned about the real overpopulation problem, you could support Wild Animal Initiative to look for safe and effective means to intervene in nature to improve long-term animal welfare.
The problems with spreading the human overpopulation myth
Believing that there is a human overpopulation problem can be dangerous, because of several reasons. First, it can set the wrong priorities. Environmentalists who worry about human overpopulation put more focus on immigration restrictions and birth control measures, trying to convince people to have fewer children, instead of focusing on sustainable production and consumption.
Second, it can result in drastic, coercive measures that violate the right to bodily autonomy of women. People who warned about human overpopulation sometimes proposed means such as forced sterilization, which happened in some regions such as India.
Third, it can also decrease support for development aid. People who worry about overpopulation sometimes claim that saving lives of people in poor countries is not good because those poor countries face high levels of population growth and fertility rates. However, the area that has the highest fertility rate, Sub-Saharan Africa, is currently sparsely populated compared to highly developed regions such as Western-Europe. The population density of Sub-Saharan Africa is 50 people/km², which is almost four times lower than Western-Europe with 180 people/km². Even when its population is projected to be quadrupled by the end of the century, its population density will still be comparable to current Western-Europe.
What I am not saying
The claim that non-human animals are overpopulated cannot be used as an argument to destroy nature or harm wild animals. I am not saying that we should decrease the population sizes of wild animals. We should improve wild animal welfare and strive towards a world where each animal has on average one offspring that gets a long happy life. (And in the very far future, when all humans and animals could have quasi infinitely long lifespans, the average number of offspring per female animal should be close to one.)
Personal statement as a final remark
In the past I have often communicated about the human overpopulation problem, and I supported campaigns against human overpopulation. After thinking more critically about this issue, and learning about the problem of wild animal suffering, I changed my mind. Although I still support voluntary family planning because it has several benefits, human overpopulation is no longer a reason to support it.