Is overpopulation a dirty word?

Many readers of our blog probably see no problem with “overpopulation,” but we sometimes get negative responses when we use the word, even from colleagues who largely share our views. Why is this so? How should overpopulation best be defined?

By Frank Götmark, Jane O’Sullivan and Phil Cafaro

In contrast to other organisations dealing with population growth and its associated negative impacts, TOP uses the word overpopulation in our name. When we started two years ago, that surprised some people. They wondered, what is “The Overpopulation Project”? In one sense, it’s humanity’s present project: the process of increasing human numbers globally to the detriment of wildlife, our common climate, food security, green urban spaces, and more. Our project’s overall aim is to understand and explain the connection between human numbers and these problems, in order to help societies address them more effectively.

But for many people who, like us, have worked to draw attention to the risks of excessive human populations and promote family planning to minimize further population growth, “overpopulation” is a dirty word. According to them, it can paint us as misanthropes: perhaps not as bad as Thanos in the film Avenger’s: Endgame, but still somehow guilty of wanting to eliminate surplus people by unethical means. Of course this is a misrepresentation, but it happens. Should we self-censor to be a smaller target for criticism, or should we present our honest view: that humanity is already overpopulated, and that by denying it we turn our backs on the best options for averting humanitarian and ecological crises?


What does science say about overpopulation? The word can be applied to any species which exceeds the carrying capacity of its habitat. For a while, the species might continue to thrive, but only by running down its “natural capital,” consuming things faster than they can regenerate and disrupting the balance that sustains each year’s bounty. Ultimately, the degraded habitat will no longer support such numbers and the population collapses. But people can modify environments to support more people. They can use technology to get more goods and services from the same resources, and they can gather and trade resources over vast distances far from where they actually live. This has led to lengthy discussions about the question “How many people can the Earth support?” (Joel Cohen’s 1996 book of that name ran to 534 inconclusive pages). The answers depend on value judgements, such as what quality of life we want people to have and how much we value preserving wild places where other species can thrive; also on what technologies we might conceivably draw upon in the future. Maximum and optimum population sizes are likely to differ.

All of this creates a large grey area, with much room for disagreement about what constitutes overpopulation. The Global Footprint Network, for example, defines “overshoot” by contrasting a population’s overall consumption with its country’s total biocapacity. This definition assumes perfect substitutability between different biocapacities, as well as an entitlement for humans to consume it all. But even this selfish and overly optimistic treatment concludes that we’d need 1.7 planet Earths to sustain our current behaviours. Whether we could retreat from this excess purely by consuming less and improving technology, without also stemming humanity’s population growth, is beside the point – for now, we are overpopulated by their assessment.

Grey areas aside, we believe there are limits beyond which human overpopulation becomes undeniable. Surely overpopulation exists where 1) people are displacing wild species so thoroughly, either locally, regionally, or globally, that they are helping create a global mass extinction event; and where 2) people are so thoroughly degrading ecosystems that provide essential environmental services, that future human generations likely will have a hard time living decent lives.

Urban growth causes natural habitat loss

This definition recognizes that people are not on this planet alone, we share it with perhaps 10 million other species, and that in any case, we don’t want to live like rats in a cage. We don’t just want to live, we want to live well, we want our grandchildren to live well, and we want them and their grandchildren to live in a biologically rich world. On this definition, most nations, and the world as a whole, are overpopulated right now, and getting more overpopulated with each passing year.


So why are people uncomfortable using the term? First, some people deny overpopulation exists, referring to recent progress in human well-being around the world. Second, the term may cause communication problems, if not explained well. Some colleagues and other conservationists, both in rich low-fertility countries and poor high-fertility countries, feel it gives the wrong impression about whose interests are being pursued. Let’s consider these two issues in turn.

Regarding the first, we do not deny that the average living conditions for many people around the world have improved in recent decades. But this general case is often taken too far, since in absolute numbers undernourishment, for instance, persists and has even increased compared to 60 or 70 years ago. Furthermore, future improvements in peoples’ lives are commonly taken for granted, despite the UN’s forecast that we face another 80 years or more of substantial population increases, while environmental capital, from groundwater reserves to climate stability, are being run down already. But pointing to the fact that food and freshwater cannot increase indefinitely as the human population grows usually has little effect; many will argue that Malthus was proven wrong in the 19th century, Paul Ehrlich in the 20th, and smart Homo sapiens will solve new problems through clever management or new technology in the 21st. And the more people, the more brains to solve the problems!

But note, this is a common response from political and intellectual elites whose privilege has allowed them to do well and feel confident about the future. The general public heading to work on crowded buses, low-paid workers fighting flooded labor markets, or poor farmers worried about droughts or subdividing their properties among their numerous children, may have more negative and realistic views about population increase. You can see this contrast when the public responds to newspaper reports or opinion pieces focused on solving environmental problems through technical solutions; check the online comments after the article, where readers often recognize population growth or overpopulation as the missing piece in the texts, and express skepticism that solutions which ignore it will work.

Those who have any interest in wildlife are even less inclined to argue away overpopulation, since they are aware of current negative trends for wildlife numbers. One study of mammal population trends for the period 1900-2015 concludes, of “the 177 mammals for which we have detailed data, all have lost 30% or more of their geographic ranges and more than 40% of the species have experienced severe population declines (>80% range shrinkage).” Another study, published last year, concluded that North American wild bird abundance decreased by 30% during the last 50 years, an astonishingly rapid rate of loss. Overpopulation has obviously contributed to these negative effects on other species, so those who care about other species are less inclined to argue away its existence.

The second issue is that in some circles, such as in discussions regarding international development aid, the term “overpopulation” seems to have become taboo. Among our colleagues in Africa, “overpopulation” can create negative responses, despite our sharing similar views on the negative effects of population growth and on the needed solutions, such as greater financial support for family planning. For example, in a response to TOP’s website where we highlighted overpopulation, an African colleague wrote: “Your piece also ignores the issues of inequities within and across countries which is at the heart of the poor state of human conditions we see in different parts of the world today.  It is NOT overpopulation that is sending millions of children to bed hungry each night. It is not overpopulation that is responsible for the massive ecological devastation in Africa today.”


There is a lot to unpack in these words, but implicit is the idea that citing overpopulation means denying the inequities of colonial legacies and modern exploitation. Even worse, that the person citing overpopulation wishes to impose some sort of penalty on poor, high-fertility countries, rather than identifying a crucial area in which they need help. We’re all raised on stories where adversity is characterized by villains and heroes, so it’s hard for some to grasp that naming is not blaming. Yet it is difficult to argue that population growth has played no role at all in driving deforestation, overgrazing, soil degradation and other environmental harms in Africa, not to mention shrinking land holdings, burgeoning urban slums and insufficient access to food, infrastructure and services. And with all that is known about crowded labour markets leading to low wages and exploitative working conditions, can it really be argued that population growth plays no role in driving economic inequality?

No country outside OPEC has achieved middle-income status without first reducing its birth rate substantially through voluntary family planning, and every country which did so, regardless of their colonial legacy, has seen substantial betterment. By denying the problems generated by continued rapid population growth, our colleague’s commendable desire to address economic equity could contribute to worsening it. Such denial also ignores the fact that limiting future population growth is likely to be an important factor in whether African nations are able to preserve their spectacular wildlife heritages.

Pointing all this out does not mean arguing against greater economic equity between nations, fairer trade relations, or increased foreign aid—all of which we support. Nor does it mean acquiescing in overconsumption by wealthy people, or pretending that overpopulation is only an issue in the developing world. As we say on our web site: It is important to realize that overpopulation exists in many rich countries with too high rates of consumption as well as in many poor countries with too high fertility rates. Every effort should be made to reduce high consumption rates as well as high birth rates; in combination, these two measures would create a much better future for people on the planet.

Black friday

On this view, the fact that some rich nations have aging and declining populations is “good for the Earth,” as we argued in a 2018 paper. On this view, each nation, each political leader, each citizen, can contribute to creating sustainable societies by addressing both consumption and population issues, and their interconnections.

We agree that population isn’t everything. But addressing overpopulation is important in creating societies that sustain good human lives and maintain the existence of other species. We ignore it at our peril. In recent decades, many environmental advocates have done just that. Their neglect or denial has made it much harder to deliver the reproductive freedoms that people in high-fertility countries want. The program FP2020, started in 2012 to revitalize languishing family planning efforts, has helped many women in many countries receive contraception. But it has fallen well short of its targets due to weak political will in both donor and recipient countries.

Still, the fight to address overpopulation continues. At the end of last year, the organization growing out of the World Scientists’ Warning to Humanity organized a seminar on overpopulation at the annual United Nations climate change summit (COP 25 in Madrid). Several of our competent colleagues argued there that overpopulation is a major threat to climate stabilization and that there are solutions to help us deal with it. Watch video of the seminar here and send it on to others who may be wondering how to define overpopulation and what to do to deal with it.

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26 thoughts on “Is overpopulation a dirty word?

  1. Overpopulation is a dirty word, because it begs the question: Who is overpopulation, and who is not? – The standard “smart-stupid” non-response is “why do like to talk about yourself so much”. – But overpopulation is no less real for that and we should be and become frank about the inconvenient truth that mass migrants are not refugees – but overpopulation. Plain and simple – however inconvenient it may be!

  2. A good article. My personal thought is: There is no other word that better fits the reality than “Overpopulation”, The negative reactions that often arise need to be carefully, but fully, addressed, A variety of religions promote population growth (but that’s a separate discussion). A variety of nations promote population growth (but that’s a separate discussion). Some economic systems promote population growth, almost like a giant ponzo scheme (but that’s a separate discussion).

    Perhaps the most honest way of addressing the issue is to simply point out: Good modern research has shown that the greatest human population that can be sustained, resource-wise, over the long-term is 3.4 billion people. And other studies have shown that, over the long-term, the optimum largest number of people who can reasonably live with the rest of nature on Earth is 2 billion humans. Show other people these numbers, and nicely say: “Duh”. Ask them to research the info, and again say: “Duh”.

  3. An EXCELLENT article!

    “. . . check the online comments after the article, where readers often recognize population growth or overpopulation as the missing piece in the texts, and express skepticism that solutions which ignore it will work.”

    Right! Get the public involved. As is done at the beginning and at the end of “The Population Fix,” simply ask people, “Ultimately, how many people would you like to have living in America?” The same might be asked as, “in the world?” or “in (name a country)?” In other words, give people opportunities (surveys?) to tell those promoting perpetual population growth how they feel about it.

    Again, an EXCELLENT article! Thanks for addressing the semantic issue.

  4. Another excellent article, notable for the wisdom and common sense which seem to have eluded many of our present day activists and NGOs.

    My feeling is that the vociferous and influential proponents of open borders and pronatalism are driven by an overweening emphasis on human rights, ignoring the human responsibilities which we have, as the dominant species,for the world’s flora and fauna; secondly ,a conviction ,arising from their reluctance to acknowledge the consequences of human population pressure, that allowing unfettered freedom of movement will spread us all out evenly and justly, thus relieving mounting environmental and social problems.

    That the public at large do not agree with this magical thinking is dismissed as ignorance and bigotry.

    Thirdly, business and governments alike continue to promote the need for an increase in birthrates in an already crowded world, reliant as they are, on a pool of cheap labour in the flexible service economies which prevail.

    I see so much hand waving and ecobabble now: zero carbon, zero waste, rewilding, green energy, new technologies, automation, more people means more solutions, open borders, the promotion of nuclear energy, longevity research ,all enthusiastically embraced as leading to a brave new very crowded world.

  5. I merely want to add my praise for your essay. Overpopulation is not a dirty word, but an inconvenient truth. Promotion of population growth without a full consideration of the future impact upon all the factors covered in your essay, has much in common with capitalism/neoliberalism which would find “no growth” an existential and systemic threat.

    1. Indeed. One of my pet peeves is that the mainstream media like NYT will run general articles about the environmental problems associated with population growth … but whenever specific examples arise in places like Italy or Portugal or Japan or the US about falling birth rates, the same media publish predictably alarmist articles bemoaning these as examples of “declining” economies with the “problem” of declining fertility rates that needs to be “solved” if economic disaster is to be avoided.

      It’s exasperating. Moreover, the cognitive dissonance in the NYT newsroom must be several feet deep by now, and difficult to wade through.

      1. All of this is the fault of our population scientists, including the authors of this article. See my comment for the technical flaws with the conventional wisdom.


    This is a fascinating find: Professor Patricia MacCormack advocates an ahuman future; not achieved by culling but by a renouncement of reproduction.

    That a British academic has had the courage to challenge the status quo gives hope for the future. Most humanities faculties are firmly wedded to the liberal -rights driven dogma typically promoted by the NYT and the UK’s liberal[left commentariat.

    Would it be worth asking her to write for this blog?

  7. Thank you Frank et al. for this essay. The word ‘overpopulation’ is regularly seen as a value judgement, implying that someone thinks that the number of people (on earth, in a country or a region) should be reduced, which is considered a misanthropic, totalitarian, racist or imperialistic position. You perfectly point out that the word is purely descriptive: “[It] can be applied to any species which exceeds the carrying capacity of its habitat.” However, this leaves the reader with the famous Cafaro question: “How many is too many?”
    If I get a fine for speeding, I am entitled to be informed of two things: #1 my actual speed at the moment of measurement and #2 the allowed maximum speed. Similarly, if somebody states that a region is overpopulated, I am entitled to be informed of #1 its actual population and #2 its sustainable population, otherwise the statement is meaningless. If one uses the word “overpopulation”, one should set a standard.
    I believe that the standards defined by the Global Footprint Network are the best we have achieved thus far. There is no substitutability between different biocapacities, as they are calculated separately for different components. Cropland and grazing land measurements will give you an indication of reserves or deficits concerning food as vital necessity. Of course, you can forests turn into cropland, but this will reduce the sequestering capacity for greenhouse gases and exacerbate your carbon footprint. The different footprint components are measured at regular intervals and therefore dynamic; they give you up to date information of consumption and pollution levels and tell you how much your region is in overshoot, given the available carrying capacity. They simply say: if you go on living like this, then you have to reduce your population by X individuals in order to achieve sustainability.
    As with fines for speeding, there is a band width. If you exceed the allowed maximum speed with less than say 8 km/h, then the authorities will not fine you. If a country succeeds in reducing its consumption and/or pollution levels, it can harbour more inhabitants in a sustainable way. On the other hand, if a country is to support wildlife, the sustainability standard might be too low. Nevertheless, a standard is needed, and GFN-standards are a useful first step.

    1. I agree that GFN provides a useful start to discussions regarding sustainable population numbers. And perhaps we are too hard on them, or misunderstanding their treatment of substitutability. That’s worth going back for a further look.

      On the other hand, the failure to make any place within the GFN framework for sustaining other species seems like a terrible flaw. It strongly pushes users to think of sustainability purely in anthropocentric terms, and we have plenty of evidence that those who see the world in anthropocentric terms tend to accept displacement of wildlife with few qualms.

      1. The GFN is idiotic. They count only the carbon emissions, not the actual fossil fuel. In other words, they are going to say that we are sustainable as long as the carbon being emitted by burning fossil fuels is being absorbed. The head of the GFN told me that they did this to be “conservative”. There is no excuse for this garbage.

  8. A thoughtful article with much to provoke rational debate. It has been my experience that even the mention of
    human population” in connection with global sustainability issue causes people to draw back into their defensive shells and immediately label the speaker as a “racist”, “Communist”, “atheist” or “mad.”

    I have heard this response for more than 40 years since turning my own education to finding facts about human growth starting with Malthus when I was only 15 years old in the 1960s. Yes, I am a grey power person but have seen the coming catastrophe continue to build despite the voices of rational thinking. Its not encouraging to find a vacuum when what humanity needs are compassionate listeners and action to admit to our responsibility for earth’s climate dilemma.

    As a Quaker, my spiritual path includes respect for all life and the need for consummate stewardship thereof. I see the over-growth of the human species as the most selfish demonstration of ego ever acknowledged.

    So, what other word than “over-population” can we possibly admit to the conversation if we are not to hide the truth and stumble on destroying every other living being on the planet? Maybe we need to invent a word…but I don;’t know what. Of course ultimately the humans on mother earth first need to admit they are part of the problem and must become art of the solution.

    Thank you for the article and opportunity to discuss.

  9. It is, as you point out, important to reduce both consumption and population. I don’t have the numbers in front of me, but suspect reducing family size by one in rich countries reduces consumption equivalent to a reduction of n in a poor country, with n being sizeable, and dependent on your choice of countries. So both efforts are needed in developed countries.

    It’s always struck me that criticism of advocates for limiting fertility in poor countries is tantamount to support for more starving children, for that is the reality, and it needs airing more widely.

    What’s the evidence? The “president” of Venezuela has just called for women there to procreate more while malnutrition amongst children is rife and citizens who can, flee. History has many more examples.

  10. To address the over population part of the human impact equation that distresses the planet, and threatens survival of every living being, we as intelligent creatures (?) ought to see the need not to politicize our actions in response – which of course is being evidenced in such actions as you mention with Venezuela. It is hard to comprehend how any worthy world leader could make such a request…I find it hard to think the women in his country would respond positively because they can see first hand what more children does to the level of poverty and hunger in their own populations.

    To avoid distancing people from thoughtful consideration of our human dilemma, it seems a turn of phrase that is less personally threatening as “over population” appears to be might help our arguments. I am reading Jennie M Ratcliffe, PhD ‘s 2019 book “Nothing Lowly in the Universe” which presents her scientific views of an integral approach to the ecological crisis. In her book, she elects to use the word “biocapacity” when speaking of population impacts. Its a good description. We need to recognize is the earth’s capacity to sustain us. Perhaps this turn of phrase may support our arguments with less political overtones.

  11. Thank you for this blog. It’s an island of common-sense, rationality, and thoughtful discussion about the human population issue for those of us concerned about the environmental impacts.

    This article is good, and very relevant. I am continually shocked and demoralized by the extent to which ostensibly “environmentalist” websites like studiously ignore overpopulation as a basic problem undermining efforts to restore the earth’s ecological balance (at best), and accuse anyone who might suggest this is the case (e.g., me) of being ignorant and racist (at worst). The hipster meme seems to be that if we just create some sort of socialist utopia where resources are fairly and rationally utilized and distributed, then all our environmental problems will go away, with continued population growth being an irrelevant distraction.


    The cluelessness of those hip and leftist “environmental” activists is infuriating. And I say this as a leftist myself. No amount of rational discussion, specific examples, data summaries or personal observations will sway them from their politically correct stance that any discussion of “overpopulation” is, by definition, insidious and evil.

    So, thanks again for this blog and this article. For my personal sanity, I should probably spend more time here, where environmentally conscious people seem to “get” it, and less on sites like Grist, where they have developed earnest but exasperating tunnel vision on the population issue.

  12. It is noteworthy in my experience that the balance of biological scientists accept the word overpopulation as important to understand and to act on. But a great percentage of social scientists reject it as not being useful and irrelevant. Anyone had a similar observation?

    1. I have a similar experience. Natural scientists often avoid the term to preempt tedious flak from social scientists. I have also heard a social scientist admit (without realising the implications) that he and his colleagues avoid studying population in order to not touch on sensitive and unpopular issues.

      BTW – my working definition of overpopulation is this:
      An area or region is overpopulated if, given its cultural and technological regime, it requires geographical expansion or out-migration [emigration] to move into the distant future [persist long term].
      Corollary 1: For the same region, different cultural and technological regimes can sustain different population sizes. For example, one is not better than the other per se, but a pastoralist culture and society and an agricultural society can typically sustain different population sizes in a given region.
      Corollary 2: When cultures and sub-populations compete for the same resources in a region, a multicultural society can sustain fewer people than a monocultural society. This is due to transactions being more efficient and less wasteful absent barriers of language, trust and inflexible cultural traits.
      Corollary 3: When cultures and sub-populations do not compete for the same resources in a region, a multicultural society can sustain more people than a monocultural society. For example it has been argued that what is now Sweden was in prehistoric times for centuries inhabited by both hunter-gatherers and early farmers without much interaction between them, neither peaceful nor hostile.

  13. The conventional wisdom from our population scientists is fundamentally flawed. This article continues that. The conventional wisdom only has 1 term for “overpopulation”. There are 2 separate concepts that need their own separate terms and must be comprehended by anyone attempting to be a population expert.

    1) The definition of overpopulation is trivial to understand. It is when the population exceeds the carrying capacity, which is the maximum that can be sustained indefinitely. There is only one logical interpretation of this. If the species is consuming resources faster than they renew, then the species is overpopulated. The last time the world population was sustained using only renewable resources, the numbers were below 1b.

    (The GFN is just plain stupid. They do not count the consumption of the fossil fuels as unsustainable, but only the production of CO2. This is like reporting that empty cans of food are littering the deck of the ship that’s on a journey at sea for an unknown length of time. The occupants are not able to catch enough from the sea, so they are eating the stores of food, but the GFN only reports the piling up of sharp metal!)

    Most experts seem to comprehend the definition of overpopulation, but they confuse the issue with useless quality of life measures. They bloviate on and on about poverty and wars and whatever, because they do not comprehend the second term.

    2) The missing definition is “the limit”. To comprehend this we must imagine that the population is at the limit such that the population cannot grow. If we are in that situation (x-2)/x children must die when we average x babies. Notice what this tells us! The one and only consequence of averaging too many babies for too long is dead children. Poverty is optional. Environmental destruction is optional. Wars, disease, etc are all optional. All of the criterial listed in the comments and article here are useless.

    Of course the population limit can be rising. This very article points out the obvious ways we have raised the capacity (e.g. the green revolution, and modern fertilizers, and refrigeration). But if we are causing child mortality by pumping too many babies into the environment too fast, then we are at the limit even as the limit is rising. How do we know if we are doing that?

    Well, how is it possible that we are not? Humans, and our ancestors, have existed for far far longer than required for a population to balloon into the trillions. There are huge amounts of time when the human population was not growing. The only possible way that humans are not at the limit is if there is some sort of fertility regulator that throttles back our fertility worldwide to prevent future child mortality. This is obviously not possible.

    The groups of people suffering starvation related child mortality that have existed throughout the world are proof that we are at the limit. The limit has been growing for the past several hundred years, but during that time we have always had starvation related child mortality.

    Note: Groups is important because you could make an argument that randomly distributed starvation is nothing more than birth defects. Since these occur in groups, you cannot argue that this is some genetic flaw. The typical excuse for poverty is politics and distribution. This is NOT a viable argument that we are not at the limit. You cannot argue that other people behaved badly in order to prove that there are not so many people that children are dying as a consequence. These groups of people would have no problem muscling other species out of the way of the food that grows on the planet. They failed to muscle other humans out of the way.

    Note, starvation is not required. Any form of child mortality is sufficient. It will be the swing producer of child mortality if other proximate causes of death are not killing children fast enough relative to how many babies we average.

    3) There is a 3rd concept that our population experts fail to comprehend. If your descendants average more than 2, your descendants will cause your descendant children to die. If atheist’s descendants average more than 2, atheist’s descendants will cause the death of atheist’s children. If Joe Blow’s descendants average more than 2, Joe Blow’s descendant children will die as a consequence.

    This dirt simple, and obvious math concept is totally overlooked. If you comprehend this you’ll recognize that the conventional solutions to “overpopulation” are all garbage. You have to prove that parents cannot influence how many babies their children have before any of the crap flowing out of our demographers and population experts makes any sense. The population projections are crap because nobody has proven that parents cannot influence how many grandchildren they have. The demographic transition is a pile of unjustified conclusions from observations, because again, nobody has proven that parents cannot influence how many babies their children have.

  14. Good article. To both sides of politics, if humans are doing okay, there’s no problem – with zero thought about other species or sustainability. People feel sorry for the poor and forget about annihilation of other species.

    There is no way to avoid a hard landing now. Warnings about population and climate change have long been dismissed – not only by politicians but by the people. It’s been largely BAU.

    There’s a significant proportion of people would prefer a world of just people supported by technology, entirely scouring the world of plants and animals, of nature. To them, human overpopulation is impossible. That’s the world that lies ahead.

    Massive waves of disasters are coming. Those who have been warned for decades about the issues (and ignored them) will act as though something totally unexpected happened. BAU.

    Being realistic, however, is now called “misanthropy” by some idealists. For them, even admitting that there are population issues is an endorsement of inequality, eugenics and sanctioned murder.

    Maybe it’s too obvious, but not many point out that, as populations increase, people are increasingly in each others’ way, so frustration and conflict increases. This increased tension happens at all levels of society – from the poor individuals to nations. War seems likely.

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