8 billion: an overpopulation crisis?

How did we cross this milestone, what are the implications, and is depopulation a viable solution?
06 December 2022
Presented by Chris Smith
Production by Will Tingle.


a large crowd


Last month, we were told, the 8 billionth person was added to Earth’s human population. But despite many acknowledging that some of the biggest threats facing us and the planet, like climate change - stem from our impact on world, and the more of us there are, the worse those threats will be, the topic of population is mysteriously absent from the dialogue at major international fora, like the recent COP27 meeting in Egypt. Surely “living sustainably” must include, as David Attenborough puts it, not over-running the planet and destroying it in the process?

So how many people can, or should the planet support? And to what extent is a growing population the cause of our environmental and social issues, or is it more of a symptom of an imbalanced system and inequality, which - if corrected - will right itself?

In this episode

Population growth

- How did we get to 8 billion people?

What are the underlying factors behind our exponential growth, and how high will it go?

How did we get to 8 billion people?
Alice Reid, CAMPOP

To predict the future we must first understand the past. The road to 1 billion people took us nearly all of human history to reach, in around 1800. In the 2 centuries since, we’ve increased our numbers 8 fold, and the rate has been accelerating over most of that time. Indeed, when I made one of my first radio programmes 20 years ago, the front cover of one science magazine greeted the world’s 6 billionth person. This - as the Cambridge-educated economist Thomas Malthus pointed out would happen back in 1798 - is exponential growth. He realised that our ability to reproduce would go faster the more of us there are. Our ability to produce food, on the other hand, doesn’t. He was one of the first to sound the alarm concerning the ability of populations to outstrip the resources that sustain them. Here to explain more about how we arrived at today’s 8 billion, and the trajectory we’re still on, is Alice Reid, director of CAMPOP, the Cambridge Group for the History of Population and Social Structure.

Alice - Well, the answer to that is we don't know. It is an estimate. We do have censuses and we monitor births and deaths in most, but not all of the world. But we never measure everyone at the same time. So the UN just chose this date to mark 8 billion.

Chris - But we think that's vaguely how many of us there are.

Alice - Yes. Yeah, it's fairly accurate, I should say.

Chris - How fast is the population growing? I mentioned the history of exponential growth and the fact that it has accelerated, it has gone ferociously fast. But what do we think the current rate is as an average across the planet at the moment?

Alice - It's less than 1% a year. So you are right that population growth really picked up after about 1750, 1800. It was quickest in the 1960s when it was about 2.2% per year and it's actually slowed since then. And population growth is going to get slower and slower up until about 2100.

Chris - It's patchy though, isn't it? Because if one asks, what is the population of our country doing? We'll get a very different answer than if I ask, for instance, what's the population of Nigeria doing?

Alice - It's very variable. And many places have populations which are already falling. For example, Italy, many places in Eastern Europe, many places in East Asia, Japan, China and so on. But many parts of Africa still have quite rapidly growing populations.

Chris - Now, if we look back in history, what do you think drove the changes that we saw? Those rates change, very fast, and now in some cases, as you're saying, some countries have diminution in growth or even a shrinkage where other places are still growing quite quickly.

Alice - So most countries have either been through or are going through a process called demographic transition. And this is the change from quite high and variable mortality and fertility rates. So lots of births and lots of deaths, and then a change to low and variable, less variable mortality and fertility. And different countries have gone through this process at different times. And for example, Britain and most of Europe, North America went through this process in the 19th and early 20th century. But other places are still going through this process. Of course, individual countries are also affected by migration, which feeds into that balance of people too.

Chris - I did read a statistic somewhere, I must admit, I haven't fact checked it, but it seems plausible. And it said because of ferocious rates of growth, which you were pointing to in the 1960s and that sort of ilk, that 15% of the people who've ever lived are alive right now. Does that sound plausible to you?

Alice - No <laugh>, well those sorts of statistics have been analyzed and debunked and I can't remember exactly where 15% fits, but there's a great episode of more or less on that. So you can go and listen to that.

Chris - <laugh>. When do you think then, based on what we know and what facts, figures and stats we can rely on, when do you think we are going to reach peak person? When will the population top out at whatever number it's going to?

Alice - Current estimates suggest that it will probably peak at about 10 and a half billion, somewhere around that. Before the year 2100.

Chris - Right. And is that assuming just everywhere continues, continues to grow at the rate it is now? Are people factoring into these predictions climate change, migrations, the fact that some parts of the world will become much nicer to live in, but they're far fewer and outstripped by the number that will become worse places to live because of things like climate change?

Alice - Each country's estimates are done on a country level basis and take into account what's happening to mortality. And most of the assessments reckon that mortality will continue to decline slowly and that fertility will, depending on what's happening to fertility in that country, will either sort of decline if it's not already below replacement, which is below about two children per woman. So I don't think there are massive issues with mortality built into those to do with climate change. I think most of the assessments of population are that mortality will continue to decrease slowly. Of course that may not happen if there are problems with mortality events connected to climate change,

Chris - Where do we think the hot spots are for the next few decades?

Alice - Well, most of the population growth will occur in Africa. Population is declining already in China, although fertility has been low, below replacement levels in China, since about 1990. Population overall is finally starting to decline, but population growth is likely to carry on in Africa where fertility is still three or four, five children per woman.

Chris - Is there any reason why the population isn't higher than it is already?

Alice - Well, that's because of the demographic transition, because fertility does tend to start to fall at some point after mortality has fallen. So as populations' living standards get better with falling mortality, then women start to want to have fewer children, partly because more of their children are surviving into adulthood. Partly because some of those changes, um, which occur, give women more opportunities. Partly because they begin to see that they have control over their fertility and can reduce it. So if fertility hadn't declined and wasn't declining, then the population would be bigger than it is.

Chris - And we'll probably be hearing a bit more about that in a little while from Kathleen Mogelgaard. Alice Reid, thank you very much indeed for outlining the current population situation for us.

A crowded beach

- The challenges of a greater population

What are the issues that a population of 8 billion people have to face?

The challenges of a greater population
Kathleen Mogelgaard, Population Institute

If our immediate future is for the moment set to be one of continuing growth, what are the challenges that we are facing with a greater population? Will Tingle spoke with Kathleen Mogelgaard, CEO of the Population Institute about the array of challenges that come with a growing number of people, from disease, to the economy, to the environment…

Kathleen - This is also a complicated one when it comes to thinking about population trends and environmental impact, because we know that not every person has a uniform environmental footprint. This is illustrated really clearly with the climate change issue where folks in the United States and other industrialized countries have a huge carbon footprint with the kinds of consumption patterns that we have. And places around the world that are growing the most rapidly, in sub-Saharan Africa, for example, their carbon footprints per capita are extremely small. So while it is true that an overall growth in the world's population over time is a factor that can drive the growth of greenhouse gas emissions, population growth is not an area that is dominant in terms of its impact on the growth of greenhouse gases. The area that is dominant in the growth of greenhouse gases is the highly fossil fuel consumption patterns that are happening in industrialized countries. That's not to say however, that we shouldn't be thinking about population dynamics in our response to the climate crisis. And one area where this is extremely evident is in terms of climate change vulnerability. We know, for example, that the countries that are most vulnerable to the negative impacts of climate change, many of them are experiencing rapid population growth. So as we as a collective global community are thinking about long range responses to the climate crisis, we really need to be understanding those demographic trends, how they exacerbate vulnerability, and also thinking about how the investments that we make today that improve the health and wellbeing of people here today can have an impact of shaping demographic trends over time in ways that reduces the scale of human vulnerability to climate change and really strengthens adaptive capacity. Things like investing in the education of girls, ensuring that reproductive health and family planning services are available and accessible to everyone everywhere.

Will - In less economically developed parts of the world. Obviously, as you say, they are not responsible for the majority of carbon emissions, but is there anything to the claims that as their populations grow and industrialization increases and they have access to better transport, better infrastructure, better standard of living, that their levels of carbon emissions will suddenly spike up? And with the increase in population they have, it becomes an environmental effect of a greater population, but 20 or 30 years further down the line?

Kathleen - For sure. And some of the climate modeling that has been done has demonstrated this. That over time, as we have growing world population and as we make assumptions about the kinds of poverty alleviation and economic development goals proceeding, that there will be, even with the best technology in renewable energy extended to everyone everywhere at as quick a pace as we can possibly do, there will be continued use of fossil fuels to some degree in parts around the world. And so as populations that are growing now hopefully begin to come out of poverty, we can expect their carbon footprints to increase to some degree. But we hope that we can really be doing our job to support the development and dissemination of renewable energy technology very widely.

Will - It's a hot topic now, and it certainly has been for the last few years, but with an increased population, does that go hand in hand with areas being more prone to disease outbreaks?

Kathleen - Certainly as communities live in closer contact with one another as population density proceeds, you know, there is a global trend toward urbanization. In the last couple of decades, we have crossed over the threshold of 50% of us now living in urban areas around the world. And we are also pushing up against the boundaries of natural habitats. And these are things that, as I understand, can lead to greater transfer of disease between animal populations and human populations. And then when you have human populations that are living in much greater density, in closer proximity to one another, diseases can transfer, and can be spread more rapidly in those kinds of conditions. Particularly if there are places where infrastructure is not in place, where communities are not planned in ways that really support clean water and sanitation, for example. There's that kind of human population density that can lead to the rapid spread of disease.

Will - What are the economic effects? Because presumably you'd think if there were more people, surely we are generating more money.

Kathleen - It's not quite that simple, unfortunately. We are living in an increasingly demographically divided world, and I know there are a number of countries that are experiencing population aging, with greater proportions of their populations in the older age brackets. There are some countries right now that are actually experiencing population decline, but there are many countries around the world that are continuing to experience very rapid population growth, and they have extremely youthful age structures. So each generation is larger than the one before. And in places where they're already struggling to provide basic services around education, around housing, around job opportunities, when each generation is larger than the one before, it can be very difficult to even stay in place with the kinds of progress that you are offering to your own population. And a very rapid population growth rate can overwhelm those basic services, can make it very difficult to provide education to the population, to provide housing and to provide job opportunities. So a rapid population growth rate that many countries are still experiencing can make it very difficult to pursue our goals around poverty alleviation, for example, or other sustainable development goals.

An ageing woman

- The economics of 8 billion people

What are the economic challenges of an ageing population, and who's responsibility is the environment?

The economics of 8 billion people
David Willetts, Resolution Foundation

David Willetts is president of the Advisory Council at the Resolution Foundation think tank that looks at ways to improve the living standards of those on low-to-middle incomes. Before that he was the UK’s minister for science and universities.

David - I think that we've had some fantastic analysis already from your earlier contributors, but I thought one point they didn't quite bring out was the sheer drama and challenge of this demographic transition that every society goes through eventually, where you've, as they say, 'first you stop dying like flies, and then you stop breeding like rabbits.' So first of all, people observe that there's many more babies surviving and then they lower their birth rates. But in the meanwhile, you have this surge in the number of young people and it makes or breaks a society. It's the biggest single event in the history of any society. And that transition can mean that you have lots of productive workers and can take your economy up to real prosperity. But if you can't absorb them and you have large numbers of unhappy, unemployed young people, you have revolution and civil war. And it's a massive challenge to absorb these young people. If you do it successfully, then this bulge works its way through the population. And then the great image is, it's like a python swallowing a pig. This monster generation of young people who've all, all survived, means that you end up with a lot of old people and they have a new set of challenges. So my view is that for each society and economy, riding that set of changes is in many ways more important than the exact number of people we have in the world. The question is, if we can manage that transition well and we have economic advantage, then we should be able to tread more likely in the world than we do at the moment. And we've obviously got to produce far less carbon dioxide. But if societies make a mess of that transition, then they're unstable and often poor countries that will find responding to the challenge of climate change very difficult indeed.

Chris - I thought among poor countries we could include the UK <laugh>. Because we are sort of the beneficiaries of that big baby bump. We call them the boomers, don't we? Big population expansion after the war. That has led to a huge level of economic productivity because people are most economically productive when they're north of 20 and south of 70 in age. And then as you say, you've got to deal with what happens next because people in their retirement are net consumers. So we've had the benefit, we've had that bump, but we don't seem to be managing it very well. We've now got about three or four people in work for every retired person that we're trying to pay tax to support.

David - Well, indeed, one of the reasons for the underlying pressures on public spending, leading in term to the increases in taxes, is quite simply that we have increased numbers of pensioners and also, as the boomer's age, and look I'm a boomer myself born in the boom between 45 and 60, there's also increasing pressures on the NHS. So that process of the change in the age composition of your population means at first you go through a sweet spot, all this surge in the population, when the pig is in the middle of the python. Then you've got lots of workers, not many pensioners ahead of them, not many kids behind them. Then when that big generation grows older, the pressures change. And then you add in climate change. In my book about this, The Pinch, I actually provide the figures for, the other fact about it is we, baby boomers in Europe are likely to have produced 700 tons of carbon dioxide each during our lives. 1500 tons of carbon dioxide for each American boomer, by the way. But our kids and then our grandchildren eventually are clearly going to have to make a massive adjustment of producing far less carbon dioxide. They can still, let's hope, enjoy prosperity, but they're gonna be treading much more lightly through the world, doing far less damage and producing far less carbon dioxide than we've done.

Chris - The point that Will Tingle put to Kathleen Mogelgaard was, lots of people living in poorer countries don't have anything like that carbon footprint that you were just sighting. So for us to say to them, you've gotta rein it in, is unreasonable to some people's minds. But the point is, well, won't they then embrace the kind of lifestyle that generates that kind of carbon footprint with industrialization of those countries? And that's presumably what we've got to safeguard against.

David - Yeah, and look, we do have a historic responsibility. In fact, because Britain had the industrial revolution. We were where it started, we do have a unique historical position. It was our inventors and our market economy that led industrialization. On the other hand, behind each British citizen, there is more historic production of carbon dioxide from our country than any other citizen in the world. And we have to accept that. And of course that does change the balance with places like India where production of carbon dioxide per person is low. However, if India and China industrialize and modernize the way we did, then they really will destroy the world's climate. So we all have to work together on this. Looking to the future, of course. One of the reasons why we in the West have to contribute is because of our historic role.

Chris - Are they receptive, these economies, to that argument though? Do they understand that they basically are the knife edge upon which climate is balancing with the scale of population? They have a billion plus people in India, a billion people in China. Do they appreciate that that's where we are and that they have a stake to play? Or are they waiting for the rest of the world to do something about it and they will carry on the same way?

David - Look, every individual country can think of a reason why they shouldn't. Either they don't have the same historic responsibility, or now we are so small compared to everyone else, it won't make much difference. Or, we've got a particular economic problem. Now we can all think of an excuse, but it's not really an excuse that anyone can use. We've got to do it all together. And I think that is the only way forward. But the other point I'd make is that, linking this to population, first of all technology can help. There is no reason why we shouldn't be able to enjoy the levels of prosperity we have today, but with far less carbon dioxide production. And actually the good news is, although it's hard to install, we know how to have decarbonized electricity. We know how we can better insulate our homes. And one of the reasons why I think this matters more than exact population numbers is that people are not just producers of carbon dioxide, they can also be innovative. They can also be creators. The people are creators of culture, they're creators of scientific ideas, they're developers of technologies. And so we should also remember that in our path through the world, we can create things that make the world a better place. The challenge is therefore to try to ensure that even relatively populous countries like we in Britain, contribute to new economic growth and new ideas whilst not producing large amounts of carbon dioxide and not extracting resources from the world that can't be replaced.

Chris - David, thank you for sharing your insights. That's David Willetts from The Resolution Foundation.

An empty park

- Would depopulation work?

Would a reduction in our population help solve the climatic, social, and economic problems we face?

Would depopulation work?
Kathleen Mogelgaard, Population Institute

A higher population has consequences not just for our environment, but also our economy. So should depopulation - long term measures to cut population growth rates - be on table at all? At face value, it seems straightforward: a lower population would liberate resources and living space, and probably cut disease outbreak risks. But is this even feasible, or worth pursuing? The Population Institute’s Kathleen Mogelgaard…

Kathleen - This is a really interesting question, and I think it's a question that is asked over and over again, over the decades and asked in different ways. But essentially, I think the question is how many people can the Earth support? And to me, this is a question that is kind of interesting to ask because it does lead us to further explore what that means, what the assumptions are that we're making about those people and how they live on the planet. The effects that a given population has on the planet is a result of a number of different factors, the number of people that are there, the consumption of those people, and then the kinds of technologies that we have in place that moderate that consumption. So from my perspective, there is no magic number of people that the earth can support. The answer to that question is, it depends. What do we envision for the lifestyle of those people? What do we envision for the technology that's in place, that's widely used in people's consumption? And then what do we assume about the resources that they are using in that consumption? So in my mind, there is not necessarily any benefit to a reduction of human population or to an increase in human population. It all directs us to think about how we live on this planet and what our values are in terms of people's overall levels of health and wellbeing, and how we value other natural systems on the planet too - other species biodiversity or freshwater systems, that kind of thing. So it really is a question of how we can organize ourselves collectively to ensure that the planet can be sustained, the natural systems that sustain us can continue to be sustained, and that we all can have a world in which people can enjoy health and wellbeing.

Will - So it's far more worth putting time and energy into improving our infrastructure and our levels of equality than it is simply trying to reduce the number of people we have.

Kathleen - Right, but it certainly does not mean that we shouldn't think about population issues and particularly as we've passed this population milestone of 8 billion people, it's a terrific opportunity for us to reflect on population dynamics and what that means for our life. And in particular, I think this is an opportunity for us to understand where there continues to be deep and persistent inequities that are driving rapid population growth in many parts of the world. So from my perspective, the day of 8 billion is an opportunity for us to really understand and double down on our commitments to women and girls around the world. Women and girls who don't have opportunities in their lives, who don't have access to services, who don't have rights to their own bodily autonomy and who maybe are not able to pursue an education. All of these things, when we can make these kinds of investments, will have the effect of not only improving people's lives, but reducing fertility over the long term and putting the brakes on the population growth that we are continuing to see. And that just makes our other sustainable development goals, the prospects for achieving those sustainable development goals brighter. If we can put the breaks on population growth, and do it in a way that improves the health, wellbeing and rights of people around the world. I'm not sure why we're not doing that right now. Those are investments that pay dividends now and in the future.

Will - People who go, 'oh, we just need to reduce our population', perhaps don't realize the nuance of that kind of question because as you say, there's a severe imbalance in emissions across each individual. There are huge ethical implications to decide who suddenly has to go.

Kathleen - I'm not even sure what it means to reduce our population. If people are advancing this notion that we should reduce our population... I'm not sure what they're thinking about. Because even understanding the basic demographic concepts, you know, we've passed 8 billion people right now. We have the largest generation of young people entering their childbearing years now. So I'm not sure what it would mean to reduce population when we actually have a lot of momentum that is built into the population that we have here right now. People being born today are going to be tomorrow's parents and there are a lot of them. We just need to think more about how we could create a world that is safe, healthy, full of rights and opportunities for people. And that will have an effect of shaping population trends over the long term. But population trends are not anything that can be turned on a dime. It's something that investments today will have the effects a generation or two down the line. So if people are talking about population reduction in the present moment, it's really hard for me to understand what they have in mind in terms of how we would achieve that.


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