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 May 22, 2019
Is the world really overpopulated?

 The notion that we're headed towards some kind of populational apocalypse---that there exists a line which, once crossed, will lead inexorably to mass starvation, and a whole planet like Penn Station at rush hour---has been used to stoke fear and sell books for more than a century. The discourse surrounding these concerns can be so toxic, that just wading into it can feel pointless, or futile, or worse.

But it is, nonetheless, a question worth gaining clarity on. And so for this week's Giz Asks we reached out to a number of experts---in sustainability, environmental studies, economics, geography, and more---to find out, once and for all, whether the Earth is overpopulated.

Jesse H. Ausubel

Director, Program for the Human Environment, The Rockefeller University

With most animal populations, the niches that encase the populations are of constant size. Animal societies growing in a given niche have dynamics neatly fitted by equations with a constant limit or ceiling. In short, from a niche point of view, resources are the limits to numbers. But access to resources depends on technologies. When the animals can invent new technologies, such as when bacteria produce a new enzyme to dismantle a sleepy component of their broth, then we face a problem. New growth pulses suddenly pop up, growing from the prior.

Homo faber, the toolmaker, keeps inventing all the time, so that our limits are fleeting. These moving edges confound forecasting the long-run size of humanity. Expansion of the niche, the accessing and redefinition of resources, keeps happening with humans.

Through the invention and diffusion of technology, humans alter and expand their niche, redefine resources, and violate population forecasts. In the 1920's, the leading demographer, Raymond Pearl, estimated the globe could support two billion people, while today about 7.7 billion dwell here. Today, many Earth observers seem stuck in their mental petri dishes. The resources around us are elastic.

The greatest threat to future well--being is the rejection of science. Having come this far, the 7.7 billion cannot take the road back. Without science, the elastic band will snap back.

"Through the invention and diffusion of technology, humans alter and expand their niche, redefine resources, and violate population forecasts."

Matthew J. Connelly

Professor, History, Columbia University, and Director of the Hertog Global Strategy Initiative

When people ask "is the world overpopulated," I always want to ask them: who did you have in mind? Is there anyone in particular you think maybe shouldn't have been born? Are there perhaps large groups of people, like millions of people, who you think shouldn't be here? Because I think that if you just take the number of people in the world, it doesn't really tell you very much about the things that really matter. If you want to get specific about the things that people really do care about---Is there going to be enough food? Are there too many CO2 emissions?---then you really do have to start talking about who exactly is consuming this food. Is it really the case that we're running out of it? And if it's about global warming, where is that warming coming from?

Since the time of Thomas Malthus, people concerned about overpopulation have been worried about whether there's enough food to go around. The good news is that, yes, there's a lot of food. In fact, on average, caloric consumption has been rising for decades. It's estimated that Americans throw away more chicken than is consumed in all of India; it's also estimated that, in India, people toss out about a third of the food that they buy. So if we're running out of food, it's hard to explain why it is that people are consuming more and more of it, this despite the fact that most of us are living more sedentary lives.

When it comes to CO2 emissions, you have to ask yourself: who is producing most of these CO2 emissions? And Oxfam came out with a study about four years ago that estimated the world's richest 1% probably emit 30 times more than the poorest 50% of the planet.

"There's a big, big difference between a poor peasant farming the land and a fossil fuel corporation executive. The overpopulation framework tends to lump all humans together into one broad category, not differentiating between their differential impacts on the planet."

Betsy Hartmann

Professor Emerita, Development Studies, Hampshire College, and the author of Reproductive Rights and Wrongs: The Global Politics of Population Control, among other books

To some people, the world has been overpopulated for centuries---Malthus was writing about the population "problem" at the end of the 1700s when world population was about one billion. Many people are still frightened about overpopulation---they're worried it causes environmental degradation and leads to scarcity of resources, whether they be environmental, economic or social.

But there are many problems with this narrative. It ignores the fact that people aren't all the same: for example, it's important to identify who's actually doing the environmental damage and why. There's a big, big difference between a poor peasant farming the land and a fossil fuel corporation executive. The overpopulation framework tends to lump all humans together into one broad category, not differentiating between their differential impacts on the planet.

It focuses mainly on negative impacts, not considering the positive role technological innovation and sustainable practices can play in restoring and improving the environment. It also naturalises profoundly political processes of who gains and who loses in a given social and economic order. It feeds into a larger apocalyptic disposition, especially in the United States, where many people believe the end of the world is coming. The U.S. is probably the country with the greatest fear of overpopulation---ironically, given we have so much land and so many resources.

And although we've had a huge rise in population over the last century and into this one, the growth rate has reduced significantly---globally, the average family size now is about 2.5 children. Birth rates remain relatively high in some countries, particularly in sub-Saharan Africa, but this is mainly due to lack of investment in public health services, poverty eradication, education, women's rights, etc.

Elsewhere in the world many countries are facing population decline, with birth rates falling below replacement level fertility. In the U.S. right now women are having on average less than two children.

I think people get very nervous---understandably---when they see the figures: we have 7.6 billion people now, and the figure could go up to 11.2 billion by 2100. But what people don't understand is that the demographic momentum built into these numbers has a lot to do with age distribution: there are presently a large proportion of people of reproductive age in the population, especially in the global south, and even if they have only two or fewer children, it means an absolute increase in population numbers.

We need to understand that population is likely to stabilise or even go down in the future as the younger generation ages and that momentum peters out. In the meantime the real challenge facing us is how to plan for a growing population in environmentally sustainable and socially equitable ways. Since the majority of the world's people now live in cities, the greening of urban spaces and transport is vitally important.

Talking about overpopulation as a cause of climate change can be a convenient way for some people to ignore the powerful forces that have contributed to the build-up of greenhouse gases, historically and right now. Some far-right, xenophobic movements are now using the language of overpopulation. The manifesto by the New Zealand shooter opens with overpopulation discourse. In Europe and the U.S. the far-right is very concerned about falling white birth rates, and the notion that immigrants are replacing white people.

So I think we have to be extremely vigilant about how population narratives are deployed. In the 1990s and early 2000s, for example, nativists in the US tried to woo over liberal environmentalists with the argument that immigrants, by overpopulating the U.S., were causing the majority of environmental degradation and therefore needed to be kept out. Anti-immigrant groups tried to take over the Sierra Club, for instance (fortunately, they were unsuccessful).

Also problematic is the tendency among some family planning agencies, private foundations and international aid organisations to use overpopulation arguments to try to get more support for international family planning. This ends up convincing people that somehow family planning is the solution to major problems like climate change and poverty. While these groups often use women's empowerment language, women's rights and access to birth control come to be seen as means to an end, instead of important ends in and of themselves.

As a strong supporter of reproductive rights throughout my career, I believe that overpopulation discourse undermines the kind of safe, voluntary family planning and reproductive health care that respects women's autonomy. Too often it encourages coercive methods like involuntary sterilisation.

We live in an era of incredible concentration of wealth: Globally, the bottom 50% of adults on the wealth scale now own less than 1% of the world's total wealth, while the richest 10% own almost 90%. The top 1% alone owns 50%. These numbers are staggering. Let's start there when we start talking about the world's serious problems, and not with the poorest people in the world having too many children.

Warren Sanderson

Professor Emeritus, Economics, Stony Brook University

A better question might be: Are we putting too much CO2 in the atmosphere? The answer to this question is "yes". Another clear question is whether we are using our groundwater unsustainably? The answer to that question is "yes". The goal should be to get the planet on a sustainable footing. Should we do this by sterilising American women who have more than 2 children? Would that help reduce CO2 emissions? Undoubtedly not. Should we spend more money on education in Africa? This would lower the birth rate, but the more educated generation would be wealthier and therefore pollute more. Getting the planet on a sustainable footing needs to be addressed seriously and directly. Trying to get the planet on a sustainable course through population reduction is a dangerous cop out.

Kimberly Nichols

Associate Professor, Sustainability Science, Lund University Center for Sustainability Studies

The latest science from IPCC tells us that to avoid the most dangerous impacts of climate change, we need to cut today's climate pollution in half in the next decade. This means it's critical to reduce emissions present today. The biggest system changes needed to avoid dangerous climate change are to stop burning fossil fuels very quickly, and to reduce the amount of livestock we raise.

Currently, higher income tends to be correlated with higher climate pollution. It's relatively few people who cause a large share of climate pollution. About half the world's population lives on less than $3 $AU4/day; they cause very little climate pollution (only 15% of the global total). Those of us in the top 10% of global income (living on more than $23 $AU33/day, or about $8400 $AU12,140/year) are responsible for 36% of global carbon emissions.

The fastest way to cut emissions today is for those of us who are currently high emitters to reduce our own emissions. Our study showed that the three high-impact choices that can reduce emissions today are to live meat, car, and flight-free. There are health and social benefits to these choices too. Where it's not possible to go all the way, aiming to cut today's flying, driving, or meat consumption in half is a great place to start.

In particular, flying is an extremely carbon-intensive activity, and every flight avoided is a substantial emissions savings. (For example: you would have to recycle for four years to equal the climate benefit of a year without eating meat; you emit as much carbon in one roundtrip flight (eg New York-London) as two years of eating meat, or eight months of driving a car).

"We live in an era of incredible concentration of wealth: Globally, the bottom 50% of adults on the wealth scale now own less than 1% of the world's total wealth, while the richest 10% own almost 90%. The top 1% alone owns 50%... Let's start there when we start talking about the world's serious problems, and not with the poorest people in the world having too many children."

Raywat Deonandan

Associate Professor, Health Sciences, University of Ottawa

It depends on what you mean and on how you measure these things. A region is typically considered overpopulated when it exceeds its carrying capacity, which is the number of people that that region's resources (typically food) can support. But that estimate will depend on what those people are eating, and what they are willing to eat. It's well known, for instance, that a vegetarian diet is easier to sustain than a carnivorous one. Sufficiency will also vary with our ever-changing ability to produce food.

And it's not just about food. It's also about whether there is enough energy and water and jobs and services and physical space to support people. With innovations in urban architecture, space is being managed. And depending on the level of development of the society we're talking about, energy demands will vary. Softer factors, like jobs and services, will depend on political leadership and global socioeconomic factors that are difficult to measure and predict.

How we define population density varies, as well, depending on what you're looking for. The population density of the entire world is about 13 people per km2, if you look at the entire surface of the globe. But it's 48/ km2 if you just look the land area of the Earth (because no one can live on the ocean). We call this the arithmetic density. But we could also look at "physiological density", which only considers the amount of arable land available to live upon. And with rising sea levels and desertification, there's less arable land every day.

It might be wisest to look at the "ecological optimum", which is the size of population which can be supported by an area's natural resources. By some estimates, for everyone to live the lifestyle of a comfortable middle class American, the Earth could support about 2 billion people. For a more humble and frugal European life, that number probably goes up above 3 billion. And with additional lifestyle changes, that number would rise again, possibly dramatically. How much lifestyle reduction are we willing to tolerate?

When we talk about "overpopulation" we're really talking mostly about food, since that's the rate-limiting step. Insufficient food would be a crisis clearly noticeable well before ecological collapse manifests, I would think. When fears of global overpopulation were at a fevered pitch back in the 1970s, the prediction was that we would be beset by constant famines by now. Instead, even in the poorest areas of the planet, the food supply typically exceeds the recommended 2000 calories per day. This is mostly due to improvements in food production practices and technology.

In fact, the FAO (Food and Agricultural Organisation of the UN) estimates that 1.3 billion tonnes of food produced for human consumption goes wasted each year. This is approximately 1/3 of all food produced. Most of the loss is caused by improper storage and transportation. This means that we actually have a huge calorie buffer for greater population growth, assuming that food management can be made more efficient.

Given exponential population growth, though, you would think we would exceed that food threshold pretty soon, though, right? Well no. There's something called the Demographic Transition which, in its simplest form, says that the richer a society becomes, the fewer children it produces. There is proportionally less poverty now than at any time in recorded human history, and all trend lines show consistent gains in anti-poverty measures in the foreseeable future.

In other words, we expect this increasing global wealth to manifest as slowed population growth, and eventually population shrinkage. Estimates vary, but most show that human population will peak in the 2070s, plateauing at the 9-11 billion mark, and start declining thereafter.

Will we be officially overpopulated before the decline? We simply don't know. See, it's not the number of people that's the issue. It's how much those people consume. With increased wealth, people tend to want more ecologically damaging foods, like meat. There may be fewer of us, but each of us will have a much larger ecological footprint.

See, another way to look at overpopulation is not to consider whether we have enough resources to support the existing number of people, but rather whether the existing population is creating an intolerable amount of ecological stress and damage. A poor person in the low-income developing world produces one tonne of CO2 per year. A rich person in the high-income developed world can produce 30 times that amount.

In other words, large population growth in low income countries is likely not as damaging as moderate population growth in high income countries. We could probably accommodate many more people if comfortable people in wealthy developed nations consumed a little less. So, if your concern is ecological damage, you're probably better advised to lecture First World people on our wasteful ways, rather than wringing your hands over large families in low income communities.

If I really had to answer your question directly, I would say no, the world is not overpopulated. I say this because: (1) most people in the world are not over-consuming; it's the wealthier people in low fertility populations who have the more damaging consumptive behaviours; (2) most growth is in those populations that are least responsible for ecological damage; (3) we actually have plenty of food for everyone and more, but lack the organisational and political acumen to make it universally accessible; (4) the rate of global population growth has already slowed, and we will have decline by the end of the century.