The overpopulation myth, debunked by a data scientist | Hannah Ritchie

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• If you go back in human history, I'm sure the 'silver bullet' of many environmental problems was just, "There's just too many people. If we had less people, this problem would be solved."

This particular overpopulation concern became really prominent in the 1960s and the 1970s. At the time, the big concern of the day was how we could produce enough food for a rapidly growing global population. This is really brought to the fore with the publication of the book, "The Population Bomb," by Paul R. Ehrlich in 1968.

I think there are many people of this same opinion today who still really strongly argue that the root of our environmental problems is that there are just too many people on Earth.

So some of the really alarming proposals on how to tackle overpopulation are, for example, adding sterilants to the water or food supply, offering responsibility prizes for families that chose not to have children, offering lotteries where you only get into the lottery if you are a couple that hasn't had children, removing financial support for families of a given size, or some of the most morbid, which is that, and especially for lower income countries, not just this notion of forced or encouraged sterilization, but also the withdrawal of food aid packages.

There's often this framing of a triage system, where some countries in the world might be redeemable, and maybe we should help those countries to feed themselves, but some countries are past this point—they could never be able to feed themselves, and therefore, we should withdraw any food aid.

I think there was two key things the proponents of the population bomb or this overpopulation argument got wrong: I think the first one is that they underestimated the impact of the demographic transition.

I think they assumed that the world population would continue to grow exponentially, and it hasn't. While the global population is still growing, in fact it's growing at a much slower rate. Global population growth rates peaked decades ago and have halved since then.

If we look at projections into the future, the UN, for example, expects that global population will peak well before the end of the century and start to decline. The key thing that they underestimated here was the fall in global fertility rates.

Now, this is the kind of average number of children that an average woman would have. Now globally in 1950, that was around five, so every woman would have, on average, five children. That has since fallen to 2.3 children per woman, and this is true across most countries in the world.

I think the other key thing the proponents of this underestimated was the massive technological advancements we've seen in agriculture. The issue at the time is that we wondered how we would produce enough food for a growing population, but not only has global population growth slowed, we've also massively increased the amount of food we can produce.

Crop yields across the world have doubled, tripled, or quadrupled over the last 50 years, which means that the amount of food we produce per person has actually gone up, not down, despite the fact that we have billions of more people on Earth.

I think a key argument that people often say in terms of climate change is that there's just far too many people. And they'll often point to particular countries where fertility rates are still very high.

There are some countries, for example, across Africa, where the average number of children per woman is four or five. I think what's really key to highlight here is that in these countries where fertility rates are very high, the incomes are low, and per capita CO2 emissions are also very, very low, extremely low.

That means that when you do the maths on this, you could actually add billions of people at those very low incomes; it would have almost no impact on global CO2 emissions.

I think the other issue that some people are now highlighting is the notion of underpopulation. Actually, population growth slows down too much, and it creates particular problems.

I think this won't be a problem for many countries in the world, but I think for some, especially richer countries with aging populations, you will start to see problems with particular demographics and particular balances of different demographics.

The key problem with aging populations is that within a country, you want a large number of people in the kind of working age bracket. Those are the people that are propping up the economy and driving the economy forward.

I think the problem that some countries will have with large aging populations is that they won't have a large enough group of people in the working age category.

I think there is this comparison that's often made by people that say that the problem is overpopulation is that humans are often compared to a cancer.

Well, it's true that we do have environmental impacts, and we do have large problems to solve— I think it's a very dire prediction that we don't contribute anything to the world.

If your messaging is that the human in front of you is a cancer, what you're saying is that you don't want them to be there, and you think that they should be removed. If this is gonna be the comparison we make on how to tackle environmental problems, it's really damaging messaging, and just one that won't get us there.

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