Defining Overpopulation

A recent book introduces a new approach to the science of overpopulation. We Zijn Met Te Veel (Dutch for We Are Too Many) explores a new theoretical foundation for the concept of overpopulation and explains why a smaller human population is a necessary – but not sufficient – condition for a more hospitable world.

by Fons Jena

Before you start to talk about something you must first define it. That logic must certainly be applied to the topic of overpopulation, because much of the fierce resistance against recognizing overpopulation comes from the fact that people use a wrong or limited definition of the concept.

Most definitions we can find are partial definitions, as they limit themselves mainly to the criterion of carrying capacity (including ecosystem services) and rarely mention two other criteria, biodiversity and quality of life, as separate and equally important criteria. Only a definition referring to these three fundamental criteria does justice to the concept of overpopulation. A definition that does not refer to the criterion of biodiversity is too anthropocentric, while one that only or mainly refers to the criterion of carrying capacity for humans leaves out the many effects of overpopulation on quality of life (both material and immaterial aspects).

Additionally, this three-faceted definition counters the common misunderstanding that overpopulation is solely a problem of shortages of food or other resources, or that it can be solved by technological means alone. The negative effects of overpopulation on the quality of life (peace, democracy, liberty) and biodiversity can at best be limited by technology. A hundred windmills or vegetarians will always leave more room for nature and humanity than a thousand of them.

Thus overpopulation can be defined as a condition where at least one of the three following conditions are met:

  • When a population exceeds the carrying capacity of its environment (the ‘sustainability’ criterion)¹.
  • When other species are not given enough space to survive (the ‘room for nature’ criterion, in which other species and their habitats are taken into account).
  • When there is insufficient room and resources to guarantee every individual a high quality of life (the quality of life criterion).

By consistently referring to these three conditions we can expand the debate and strengthen the case for tackling overpopulation and promoting smaller populations.

A model based on Ecology, Economy, Demography (EED)

This three-faceted definition illustrates a potential problem: the relative nature of overpopulation. The three criteria (carrying capacity, biodiversity and quality of life) can be interpreted, and weighed, differently. What is a sufficient carrying capacity? And how much room for nature must there be? Maximizing these two aspects could mean a human population reduced to a handful of cave dwellers. Quality of life is also a widely relative concept, since some of us need (or think we need) a large house and expensive cars to be happy, while others are happy with much less.

These three facets and the relativity of the concept can be summarized by a simple model, which I call the EED-model (the fields of Ecology, Economy and Demography) of overpopulation (see figure 1). When the population increases above the capacity that the economy can provide for, poverty rises. When the economy increases above the carrying capacity of the environment, we face an ecological collapse scenario.


Figure 1: Overpopulation can be defined as a balance exercise between the carrying capacity of the environment (ecology), the whole of products and services (economy) and the population size (demography).

There is also a hierarchy to be respected between these relationships. The economy must fit within the ecological limits of the environment and the population must fit within the size of the economy. This means that the balance between economy and ecology (relation 1 in the figure) is more important than the balance between the economy and demography (relation 2 in the figure). A society that has achieved a balance between its economy and its population is nice, but without having a balance between the environment and the economy it has no future. When one of these two relationships is out of balance we have overpopulation and the larger the imbalance the more severe the overpopulation.

A model based on means and ends (SNQ)

While the EED-model is a simple way to show the different aspects of overpopulation and their relativity, it isn’t enough to show how a smaller population may be a necessary condition (but not sufficient) for a more hospitable world. To show that, you need a more complex model that defines the elements that are needed to achieve a more hospitable world.

Without going through an extensive philosophical debate about the purpose of life, we may stipulate that the purpose of a good and sustainable society is to maximize the quality of life for all its members, while remaining within the carrying capacity of its environment. Furthermore, such a society should also minimize its impact on the other lifeforms with which it has to share its environment. This not only further increases the society’s sustainability, but it also increases its members’ quality of life, both morally and aesthetically. Notice that these three aspects (maximizing quality of life, staying within the environmental carrying capacity, and minimizing the impact on other lifeforms) match the three criteria of our earlier definition of overpopulation. This is no accident, since an overpopulated world cannot be a hospitable world and vice versa.

The means we have at our disposal for maximizing these three aspects can be grouped into four categories. In no particular order these are the technological factor, the cultural factor, the environmental factor and the scale factor. The first represents the technical means we have at our disposal, such as agricultural machinery, and how we organize society (non-material technology). The cultural factor stands for the moral and intellectual condition of society, its software instead of its hardware. The environmental factor is equally obvious. The capacity of a society is completely dependent on its environment and climate. A desert society cannot achieve the same complexity or develop the same technology and culture as a society in an abundant environment². The fourth factor, scale, is the one that is of primary interest here. It defines the space where the three other factors are developed and applied. A mass society develops other technology and culture than a small-scale society and it also has much more impact on its environment and climate. The scale is thus a powerful factor that co-determines the other factors and thus the potential of a society to achieve its purpose³.

This model of four means and three factors that measure the ‘hospitality’ of a society is represented in figure 2. I call this the SNQ-model, referring to sustainability (S), room for nature (N) and quality of life (Q).


Figure 2: A schematic visualization of the SNQ-model that is used to clarify the message of the book. The impact of the scale factor on the other factors is shown with dashed lines.

The SNQ-model is a formal way of showing why the scale factor (population size) is so critical in shaping a just and sustainable world. Contemporary societies instead focus mainly on the technological factor for increasing the sustainability factor. Indeed, they often ignore or deny the scale factor and its effect on society’s ability to achieve its purpose.

For our purpose, we are most interested in the impact of population size on achieving a better world, and we limit ourselves to the relation between the scale factor and the three SNQ-factors, as shown in figure 3 below.

The graph illustrating the quality of life starts with a strong increasing curve because a minimum population size and social complexity is necessary to produce all the products and services one would expect in a hospitable society. At a certain point population growth does not provide any additional benefits and after a further increase of population pressure the quality of life starts to decrease (complexity becomes too high, too much pollution, noise, loss of democracy and individual value, etc.). The graph of sustainability and room for nature is represented with a continuous decreasing line, since the more people there are the higher the environmental impact and the less room there is for other lifeforms⁴.

Figure 3: The impact of the population size (x-axis) on the quality of life (left y-axis) and the biodiversity and sustainability of a society (right y-axis). A decrease in population size gives a higher quality of life, greater sustainability and more room for biodiversity.

Today we find ourselves in the condition ‘C’ because overcrowding has already started to reduce quality of life in most parts of the world. If we would decrease population size to a condition ‘B’, we would increase the average quality of life, sustainability and room for nature. Condition ‘A’ is called the SNQ-optimum, as it is the condition where quality of life is maximized and the negative impacts on sustainability and biodiversity are minimized.

It is important to note that the SNQ-optimum is the best possible EED-equilibrium. While there are many EED-equilibria possible (each representing a sustainable condition) there is only one SNQ-optimum possible. In the EED-model you may have a sustainable situation where poverty and violence are nonexistent, but where the quality of life and room for nature can still be increased. This means that with the SNQ-model there is less room for a relative interpretation of the concept of overpopulation, which is important for making a stronger case in public debates about overpopulation. The model can even be used to define an absolute reference frame for judging whether there is overpopulation or not⁵.

The plea of every overpopulation activist can now be restated as limiting the population size to the size defined by the SNQ-optimum, because only then have we achieved a world where we can maximize quality of life, sustainability and the room available for nature. In a follow up blog, I introduce a new method for calculating optimal population size according to the SNQ-model.


  1. ‘Sustainability’ refers throughout the text to the balance between the environment and the economy. The lesser the impact of the human economy is on the natural environment, the more sustainable the society.
  2. The relations between the environmental factor and the technological and cultural factors are well described in Jared Diamond’s book Guns, Germs and Steel. Thomas Homer-Dixon’s ‘Environment, Scarcity, and Violence’ also comes to mind.
  3. For the relation between the scale factor and the other factors I refer to excellent books such as E.F. Schumacher’s Small is Beautiful and Kirkpatrick Sale’s Human Scale.
  4. This relation isn’t strictly linear, as the available technology can both increase or decrease an individual’s impact on sustainability and room for nature.
  5. In that case, the relationships between the different factors must be more concretely defined.


This blog post summarizes the first and second chapters of the book ‘We Zijn Met Te Veel.’ It is currently only available in Dutch, but the author wishes to publish an English translation in 2022. For our Dutch-speaking audience the book can be ordered through If you are interested in helping with the English translation or finding a publisher, you can contact the author via

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5 thoughts on “Defining Overpopulation

    1. Thank you for your reaction. I already tried to simplify it from the original text in the book, but I’ll try to further simplify it (and I’m not a native speaker).

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