Two ways to argue for population’s importance

Here at TOP, we are often asked how we define overpopulation and whether it’s a helpful concept. Good questions! Below I propose a definition of overpopulation, after first considering the suggestion that it’s not necessary or helpful to deploy the term, even —or especially! — if we want to convince our societies to accept good population policies.

by Philip Cafaro

According to David Attenborough, “all of our environmental problems become easier to solve with fewer people, and harder – and ultimately impossible – to solve with ever more people.” Attenborough has seen the global population triple since he narrated his first TV nature documentary back in the 1950s, as people have, in his words, “overrun the world.” So he advocates for policies to end population growth and stabilize the global population sooner rather than later, including universal access to effective modern contraception.

Sir David avoids the term ‘overpopulation,’ as do many environmentalists today. It’s a trigger word that can make it hard for listeners to hear what you have to say. It can get you labelled an “ecofascist” who wants to secure more lebensraum for your own in-group by displacing others. Perhaps, though, it isn’t necessary to show that our societies or the world are overpopulated, as long as we convince people that addressing population would help us solve environmental problems. That might be enough to justify good population policies.

Consider global climate change. The IPCC assures us that population growth has been an important factor in driving the carbon emissions increases of the past four decades, accounting for about 40% of the global increase, with the other 60% driven by increased affluence. On that basis, Brian Walsh, Detlef van Vuuren and Brian O’Neill, among others, have advocated for policies to reduce future population growth—without saying the world is overpopulated, or venturing into the complexities of what a sustainable human population might actually be.

Arguably, population growth has been similarly important in driving recent biodiversity losses and the whole array of global environmental problems. The world’s nations have failed, so far, to address these problems successfully, and the dangers of continued failure are immense. There’s your brief in support of policies to limit population growth, and maybe even reduce current human numbers. All without using the word ‘overpopulation’ or broaching the secular heresy that there could ever be too many human souls. We can show population’s importance without explicitly stating that any current or future population is too high. It is enough that limiting our numbers can help drive down harmful environmental impacts.

A potential problem with this approach is that it doesn’t prove that it is necessary to address population. Perhaps technological fixes, voluntary behavioral changes, clever institutional reforms, or some combination of the three, would be sufficient, or better for some reason. Perhaps addressing population is uniquely dangerous. This appears to be a common assumption in feminist critiques of “populationism,” which focus more on past harms to women under China’s one-child policy than on the harms of patriarchal cultures and restrictive reproductive laws in the Philippines or Central America today.

Populationists can respond that humanity’s failure in recent decades to successfully address global environmental problems shows the need to tackle all three impact factors in the I = PAT equation: population, consumption per capita, and the technologies that facilitate consumption. As Michel Bourban has eloquently argued, the time is past for speculating about ideal solutions, or misusing IPAT to prove the pre-eminence of one or another of the three factors. Instead, we need concrete efforts on all three fronts. Continued failure is too dangerous. This fits in well with the views of most population activists, who rarely argue for limiting population instead of driving down per capita impacts, but for both.


Overpopulation a necessary term

So we can advocate for population action without discussing overpopulation. Nevertheless, I see it as a necessary term, both to capture humanity’s current situation and to point the way toward a sustainable future.

I define overpopulation as follows:

Human societies, or the world as a whole, are overpopulated, when their populations are too large to preserve necessary resources for future human generations or to share the landscape justly with other species.

Recent estimates of a sustainable global population run between two to three billion people, depending on how optimistic researchers are about international cooperation to solve wicked collective action problems. Examples include Theodore Lianos and Anastasia Pseiridis, “Sustainable Welfare and Optimum Population Size,” 2016; Christopher Tucker, A Planet of 3 Billion: Mapping Humanity’s Long History of Ecological Destruction and Finding Our Way to a Resilient Future, 2019; Partha Dasgupta, Time and the Generations: Population Ethics for a Diminishing Planet, 2019; Lucia Tamburino and Giangiacomo Bravo, “Reconciling a Positive Ecological Balance with Human Development: A Quantitative Assessment,” 2021. These estimates affirm, commonsensically, that the more people we want to sustain, the more modest their average standard of living needs to be. They all assume increased efficiency and a widespread willingness to limit consumption—not instead of addressing population, but in order to sustain one quarter to one third Earth’s current population.

The costs of failing to create sustainable societies now will be continued environmental degradation and, according to many ecologists, reduction or loss of the ecosystem services our descendants will need to live good lives. So there is a clear moral imperative to create sustainable societies. But we are a long way from sustainability and these studies suggest it will be difficult to achieve, even with much lower populations. Hence we need the term ‘overpopulation.’ We need it to explain that in all likelihood, the current global population is much too large to ever be sustainable. We need it to advocate for policies to significantly reduce bloated national populations, in both rich and poor countries, rather than allowing business leaders and chambers of commerce to define population issues for the general public.

The second half of my definition states we are overpopulated if populations are too large to share Earth justly with other species. This assumes that our relationships to other species have a moral dimension. Do you agree? Many discussions of “Earth’s carrying capacity” assume that people have a right to monopolize the world’s resources: that other species are themselves nothing more than resources for our use, to be displaced or extinguished if they inconvenience us. This is the economists’ view of the natural world and if environmentalists ignore population matters, we allow it, without a fight, to govern our interactions with other species. That’s because > people = < wildlife.

In just the past fifty years, wild vertebrate populations declined by approximately 60% globally. Anthropogenic extinction levels are an estimated 1000 times higher than the historical background rate and climbing. Such trends provide prima facie evidence that humanity is overpopulated. The key to reversing them, according to conservation biologists, is preserving much more habitat in protected areas: 85-90% of wild species could be preserved if humanity set aside half of Earth’s terrestrial landscapes and seascapes primarily for other species. But such interspecies generosity is impossible at anything like our current population. To grant Half Earth to our fellow earthlings, we will likely need billions fewer people. Instead, according to UN projections, we are on track for billions more.

Henry Thoreau once remarked, “in the long run men only hit what they aim at. Therefore, though they should fail immediately, they had better aim at something high.” Sharing Earth fairly with other species and with future generations are noble goals. They are achievable—but only at much smaller populations. Even if environmentalists use it selectively in our political work, ‘overpopulation’ remains a necessary word. Hitler couldn’t imagine too many Germans. If we can’t imagine too many people, we are well on the road to real ecofascism.

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45 thoughts on “Two ways to argue for population’s importance

  1. You could also define overpopulation politically, which is perhaps the first mode we must address, by treating overpopulation as any state of affairs where persons are not treating their capacity for self-determination as directly inverse to the growth of their polity, relative to nonpolity (nature). See e.g., This approach has the virtue of invoking human rights as an overriding mechanism to correct the problem, for example. by treating concentrations of wealth as subject to family planning incentive/entitlement/reparation claims.

    1. Carter, if I understand your approach, it would define ‘overpopulation’ as a society having too many people to sustain a flourishing egalitarian social democracy, as well as flourishing populations of nonhuman species. Is that correct?

      1. A “flourishing egalitarian social democracy” is even less a universal goal and even less measurable and definable than “sustainability”, though.

      2. Gaiabaracetti – Your statement is inaccurate. The entire human rights regime is premised on that goal, and ” treating their capacity for self-determination as directly inverse to the growth of their polity, relative to nonpolity (nature)” is a clear metric for the size of polities, pointing us towards Tucker/Dasgupta and the qualitative outcomes we should see along the way.

  2. A comment on the accusation that favoring family planning in Africa is racist or anti-female reproductive rights. Nonsense. Most of us who advocate smaller families for Africans are talking about moving towards the birthrates of Europeans, Japanese, Koreans, Americans and others in prosperous countries. What’s wrong with equality? Large family countries are almost invariably poor countries. It is racist to ignore the poverty and misery, ill health, infant mortality and maternal mortality that makes life expectancy 20 years shorter in high compared to low birthrate countries. Millions of Africans are fleeing poverty trying to get into Europe. It is racist and sexist to ignore the patriarchy that sells daughters for a few cows after genitally mutilating them. By the way, I marched with Dr. King and am a proud, lifelong anti-racist. Africans are going to have to invent and implement their own paths to the fertility transitions that have made other countries more prosperous and healthy. If they don’t many more will suffer and die. It is truly racist to ignore the mathematics of larger populations on a continent ravaged by soil losses and climate change.

    1. Max, agreed! But I think as long as population activists focus exclusively on population growth in the developing world, we will be vulnerable to such criticisms. Admitting that populations in the developed world need to decrease should blunt such criticisms. But I doubt anything will end them entirely.

    2. It is a very strange logic. X is bad. X is currently done mostly by a certain ethnic group. Therefore, to say X is bad equals being racist. So X is actually not bad.

      No one is every accused of racism for pointing out that it’s mostly “Westerners” (whites) who over consume (even though it’s not just them – it’s N Americans and Europeans on average, plus some oil-rich Arab countries, plus the rich in every single country including North Korea).

      If X is bad, it doesn’t matter who does it: it is still bad.

      1. Gaia, absolutely! But that is the stage of illogic we have reached, at least in the US, around racial issues. And any issue can be reinterpreted within a racial lens. My sense is that the economically powerful are happy to have the general public biting each others’ ears off about race (and gender) matters.

  3. My answer: It makes no difference now that MEDIA ARE DEREGULATED, owned by hedge firms, no longer serving the objective news and information of the nation and the world. Media have worked hard to make population a NON-ISSUE and until we change what the major “educator” on Earth–mass media–are putting out, population and its link to SPECIES EXTINCTION, CLIMATE CHANGE or why 54 National Academies of Science and over 18,000 of the world’s climate scientists say it MUST BE DEALT WITH will remain UNREPORTED and INCONSEQUENTIAL! A democracy without honest media cannot survive and, duh, the ISSUES MEDIA DON’T EMBRACE WILL QUICKLY DISAPPEAR FROM ‘REALITY’!

  4. (This might be a duplicate comment, in which case please delete it)

    It won’t, because in the developed world population growth is due only to migration from the developing world. And in said developed world, immigrant women tend to have higher birth rates. So it is an ethnic issue, right now, even if we don’t want it to be. Not intrinsically ethnic, since low-TFR populations today used to have very high fertility in the past, but it looks that way now.

    I think it’s unrealistic to expect birth rates among non-immigrant women in developed countries to be lower than they are today.

    So population growth, right now, is a “developing world” problem first and foremost and we will be called racists no matter what even if we aren’t.

    1. Yes, but I sense an increased impatience among many environmentalists with people “playing the race card.” All we can do is persevere and try work on the issues that we believe are important. Like overpopulation!

  5. Bravo Philip! A Ukrainian refugee here in my town was talking about how no land in her country was ‘wasted’, that is, it was all put under the plough for agriculture as the soil was so good. She didn’t seem to understand that other species had a right to exist on the land as well. We do need to move to ‘Half Earth’ as soon as possible though, point taken, we need a billion fewer humans in order to achieve that.

    1. At the same time, in many countries (including my own, Italy) forests have come back because we buy grain from other places, including Ukraine, so I wouldn’t blame just them… especially considering they’ve been feeding us, but were still poor.

      1. Maybe it’s time that all countries agreed to leave a certain percentage for ‘nature’, ideally 50%, but if that means people will starve then start with 10% and move upwards as population is stabilised and hopefully reduced.

    2. Yes, like the tall grass prairie here in the US: the soil was just too productive not to convert it all to cropland. Now some people are trying to save bits and pieces of it, restoring a few hundred acres here and there.

      Other species have a right to exist! We need to shout it from the rooftops.

      1. I’ve had more than one friend, when discussing the (let’s call it) genocide against the Native Americans, say: “and the thing is, it was completely unnecessary, as America was big enough for everyone!”
        Well, not really. First of all, not for everyone if you include non-humans. Secondly, Native Americans mostly needed huge open spaces for their traditional and relatively sustainable lifestyles. It’s very hard to explain to a landless European from back then that open American land should have stayed the way it was. And now, looking at the size of the average American farm or even backyard, it seems like it would be even harder to explain it to the descendants of those Europeans.

  6. Although I think I have read or heard the two words used together, I wonder if we should use the term
    “sustainable population” or “sustainable populations” (within each country with its own cultures and traditions
    present standard of living) more often or as the standard Label for our movement. I think this expresses the more
    technical mathematical reality of ‘carrying capacity’ or ‘stocking rate’ (that most farmers have realized for hundreds
    of years) in a more ‘humane’ sort of tone. In other words it expresses the reality that civilization or the human species, who many think are the only entities that have any intrinsic/moral value, could be set back hundreds of years by an overpopulation cataclysm. Or even driven extinct by too many people in the present day or near future..

    1. Well Win, we could define ‘sustainable population’ that way. But I seem to recall an article we published 10 years ago, in which we argued that human beings should share the earth justly with other species:

      So I think we should fold that idea into our conception of what a sustainable population should be. Or we could distinguish between “selfish sustainability”, just for humans, and “just sustainability” or “generous sustainability,” where we calculated what human population is sustainable while also sustaining populations of other species.

      Conservation biologists should be calculating the “just sustainability” population number for countries around the world. Nature lovers should know what numbers we should be aiming for.

      1. Now we frame the “sharing the Earth with other species” as a choice we, as human, get to make. It’s up to us.
        I wonder whether there’s gonna be a time when other species are simply gonna take the Earth back from us, and what that’s going to look like.

  7. Carter, “The entire human rights regime” is not premised on having necessarily an egalitarian social democracy. Lots of countries talk about human rights and do not have a democracy, or have a democracy that aims neither for egalitarianism neither for a “social democracy”.
    Also, human rights don’t seem to be that shared a human goal nowadays, judging from the popular support to human rights-violating regimes.

    1. I think Carter is talking about an ethical ideal: one that includes both robust human rights and democratic self-government. Gaia is pointing out, correctly, that these dont necessarily go together. Arguably, in many populous countries in the developed world, we have pretty strong protections for many human rights, but little in the way of democratic participation in self-government. As countries get more populous, the latter becomes harder to achieve.

      1. We also have countries, such as China, that are almost as undemocratic as it gets, yet still want to keep demographic growth under control.

  8. Broadly agree with Cafaro. Nations should set maximum resource throughput that gradually falls, based on best evidence, to reach sustainability. Arguments about potential decoupling then largely disappear, as can some population arguments. Please see our new collected volume ‘Sustainability and the New Economics: Synthesising Ecological Economics and Modern Monetary Theory’ (Springer, 2022) with a chapter on population by Ian Lowe and an important section on population by Lawn & Williams in the chapter on ecological economics.

  9. Jenny, while I agree in principle, I worry about this idea in practice.
    I don’t like to see us humans as being separated from nature. I do think there should be some areas ideally completely untouched and wild, but to me it’s more important how we can be in nature without destroying it.

  10. Hi Gaiabaracetti. Both are good. I need to be in nature to stay sane but I’m sure there are lots of species who don’t need me or other humans around!

    1. Jenny, it’s not about pleasure, it’s about subsistence and lifestyle. It’s about how you produce food and other things you need, about where you live.
      Many of those advocating for land to be left completely untouched don’t understand the dangers of industrial agriculture, of new technologies, and of very high human densities. Indigenous people are being kicked off their land in the name of conservation. This is the kind of stuff that worries me.

      1. I think it is both / and. Other species need areas that are strictly off limits to intensive human economic use. The science is clear that such strictly protected areas provide the highest level of biodiversity protection. On the other hand, we need more benign agricultural practices, better use of technologies, and other changes to improve human economic activities in the world — to better protect both our own health and other species.

  11. Yes! If a complete argument does not include both reasons 1. that all species have intrinsic value and have a natural moral right to exist and 2. that increasing the human population much more is likely suicidal or at least will result in our having to live in a few rights police state like over populated China’s … then there is the great danger that the perpetual growthers like economist like Lawrence Summers, many business leaders and Wall Street are ‘free’ to declare that because the “human imagination is infinite” the world can support perhaps 15 billion by 2100. Because they or some geniuses they imagine will be born will be capable of going all out anthropocene and designing a world ecosystem that has only animal and plant species that are economically beneficial to humans …. and kill off all the rest. However, there seem to be different motivation and argument realms and audiences that need to be appealed to and I have to admit that I do not know how many of the true reasons to include what will work the best in many of them

    1. Always tricky to know your audience, know what will grab them, what will turn them away …

  12. Overpopulation and Over-consumption are equally bigger problems. In India we have achieved TFR of 2, our population is expected to peak at 1.56-1.61 billion people and reduce to 1.1 to 1.2 billion people at the end of this century. Even with decreasing populations some states have shown reduction in flora and fauna. It is because we have no choice but to destroy our environment and produce cheap products for consumptive global economy. If we don’t do this then we can’t full-fill basic necessities of our population. Providing fair share to raw material producing societies would go a long way towards environmental protection. Although Overpopulation is a “developing world problem” but similarly Over consumption is largely developed world problem. Emphasizing on only one even as there is no action on other is may be nothing but mild imperialism.

    1. I think everyone here is aware that overconsumption and overpopulation are both important and to be addressed at the same time.

      I personally think that the main difference is that, while it’s easy to reduce consumption in a relatively short time frame, especially for rich countries, you cannot reduce human numbers as rapidly, unless you want to engage in mass killings. The consequences of reproductive choices today will be felt for generations.
      That’s one of the reasons I find overpopulation more urgent as a problem. And I say this as someone who lives extremely modestly by her country’s standards.

      1. Totally agree Gaia, There is no doubt that fertility rates needs to go down further. It’s just that, it becomes so much harder for someone like me to campaign for one child or No child in my community while rich nations continue to consume the way they do. Many tribal communities in India live in harmony with the nature and just want to be left alone with complete ownership rights on their forest. Comparatively even reducing 100 million of rural population in India (By birth control of course) is not going to have much effect for environment than say if we banned all cruise ships. Rich countries are trend setters for rich in India too. G7’s choices does affect our policy decisions too. Current Indian government have completely thrown their lot for wealth creation undermining environmental laws, to compete in global economy.
        I would like to admire your modest lifestyle but I am still pretty sure that your footprint would be more than a rural Indian couple.Real change will only occur if developed economies find solutions towards sustainability and respect for other species. More emphasis on reducing populations in developing economies is not going to help a lot.

    2. Niraj, thanks for sharing your perspective. Agreed that excessive numbers and excessive per capita consumption both need to be addressed.

      Two recent books quantify the costs of overpopulation in India: Bedprakas SyamRoy, India’s Journey Towards Sustainable Population (2017) and Aalok Ranjan Chaurasia, Population and Sustainable Development in India (2020). I have only skimmed them myself, so far, but they look interesting.

      1. Niraj, do you know which Indian states have a decreasing population? I did a quick research on the states with the lowest fertility rate (, but even they seemed to have a growing population in spite of below-replacement fertility. But I couldn’t find data broken down by state for the whole country.

        Moreover, the total population of India is growing at more than 10 million a year. That’s one very big city every year. It sounds like it’s truly a lot.

  13. Philip and all, I keep reading articles in the media I consult most (eg. the Guardian and Al Jazeera) on every current emergency such as famine, refugees agencies running out of food, drought, heat waves, biodiversity crisis, you name it. I’ll read the whole article looking for mentions of population growth, and I never find them. Typically it won’t even be listed among the reasons for the problem being discussed. It’s maddening. How can we pretend that food being insufficient has absolutely nothing to do with more and more mouths to feed? When we talk about species being lost to “urban expansion”, agriculture or “development”, who are we to suppose those are done for? Are we building cities and growing food for ghosts?
    Bottom line is, I wonder if there’s a way to approach these outlets and similar ones and convince them to at least mention population growth in articles that obviously call for it. It’s like their going out of their way to avoid it. They need to be called out.

  14. Niraj, I think it’s one of those situations in which everyone needs to do something, but no one wants to go first. The same way you’re saying that it’s hard to argue for lower birth rates in India while rich people in certain countries consume so unnecessarily much, it’s also difficult to ask, say, to support very poor people in other countries when they keep having children they cannot properly care for (look for example at recurrent famines in Africa). For example, a lot of people in Italy resent not being able to afford a second child, and yet seeing recently arrived migrants with large families who get a lot of subsidies and public services.
    We each have our own point of view based on our experience.

    I of course agree that we consume too much in rich countries – no argument about that. You’re probably right that I still consume more than a rural Indian couple, but the problem is that consumption has a big systemic component and in rich countries it becomes impossible to consume below a certain threshold, because you’re required, mostly through taxes and compulsory expenses, to support everyone else’s lavish lifestyle. For example, if the law requires me to pay a lot for a notary, or a certain piece of paper I need, or a medical examination, because the people providing those services have a high salary, I am required to produce more than I would like to just to pay for that. Taxes also subsidy other’s people overconsumption. Finally, social life becomes very difficult when you are prepared or able to spend a tenth of everyone else – so you consume more than you’d like to just to see your friends or family.

    I agree that the West is giving a bad example in terms of lavish consumption, but India has a growing upper and middle class that is actually very rich, probably richer than sizeable chunks of Western populations. I think that even without “our” bad example, this could probably still happen. For at least hundreds of years, before colonialism, Asia and India in particular were actually wealthier than the West and much admired by visiting Europeans.

  15. All this problems have started after industrial revolution so last point is irrelevant.
    Let me be clear earth is overcrowded and we need to peak as quickly as possible. But what I am arguing for is that this might not be enough. Most migrants to developed world are either rich or highly skilled or both. Refugees are small chunk in the whole immigration to western world well at least in U.S. Now I think with current global geopolitics and economy, over consumption by the rich (most of them happens to live in developed world including china) would be far more consequential in coming 2-3 decades to what happens with climate catastrophe, pollution and biodiversity loss than say half a billion more people in Africa and south Asia. This may sound inhumane but this is a reality. Population should be kept in check with low TFR, and better healthcare facilities but over consumption is bigger devil here than overpopulation considering demographic occurrence, density and their respective consumption levels.

  16. Niraj, ok, but are you saying that people in India are poor because there is overconsumption in the West?

    1. No, I’m saying that consumption behavior in the West is going to be more consequential in dealing with problems I mentioned earlier than population growth in global south (which is overcrowded no doubt).

      1. If you look at the global picture, it’s not so simple:

        Still, I don’t think there should be a conflict. Since both things are certainly necessary, some people will work to lower (over)consumption, others to lower the fertility rates. We don’t need to all do the same thing.

        As for me, I studied International Development Studies at university. Once I figured that there was a global imbalance I decided it would have been more helpful to go back to my own rich country and try to lower consumption, than to go to a poor country to assist with “development”. It’s better to do the right thing than to tell others what they should do.

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