The Weekly Anthropocene: Human Population

A The Weekly Anthropocene Deep Dive

The Old Story: Exponential Growth

As you may have noticed, there are a lot of humans around on Earth these days.

After millennia of relatively little growth in population, constantly interrupted by famine, plague, and war, the Industrial Revolution kicked off two centuries of exponential growth in the human population. The twentieth century saw a truly astounding, unprecedented baby boom, from under 1.7 billion people in 1900 to over 6 billion in 2000.

Source of the above images: Our World in Data. Check it out!

Pretty much all the components of modern civilization had a role to play in decreasing infant mortality, increasing lifespan, and generally keeping more people around for longer, from indoor plumbing to penicillin to vaccines. However, particular credit is due to two extraordinary leaps in agricultural science. Fritz Haber’s 1909 invention of the Haber-Bosch process (which chemically converts plentiful atmospheric nitrogen to ammonia) made possible industrial-scale production of fertilizer. The previous best source of ammonia-rich fertilizer had been mining guano islands, and the advent of the Haber-Bosch process won Haber¹ the 1918 Nobel Prize in Chemistry and allowed a massive global surge in agricultural production. Then, Norman Borlaug’s breeding in the 1950s of new ultra-high-yield, rust-resistant varieties of wheat kicked off the “Green Revolution,” arguably saving and/or making possible hundreds of millions to billions of lives in Earth’s tropical regions, as the new wheat allowed mass wheat farming in countries like Mexico, Pakistan, and India for the first time. India in particular saw a dramatic, life-giving transformation: plagued by famines and mass death throughout its history, the country imported 18,000 tonnes of Borlaug wheat seeds in 1966, and subsequently saw national wheat production jump from 12 million tonnes in 1965 to 17 million tonnes in 1968. There hasn’t been a major famine in India since.

This massive advancement in food production, along with medical advances, infrastructure, cheap mass manufacturing, electricity and automation, and a whole bunch of other things led to arguably the greatest achievement of humanity to date: an absolute decrease in the number of people living in extreme poverty ($1.90 a day, inflation-adjusted) at the same time as massive population growth. (See the chart above, and the full fascinating statistical breakdown in this article).

But even with all of this amazing progress in feeding humanity-a truly epic and under-celebrated heroic achievement, worthy of song and legend!-the population was still growing. Could we keep pulling technological miracles out of a hat to keep everybody fed? By the 1960s and 1970s, many around the world were predicting a “Malthusian catastrophe” of population growth outpacing food production and causing famine and chaos. Books like Paul Ehrlich’s The Population Bomb warned of unavoidable millions of starvation deaths set to occur by the 1980s, and it quickly became conventional wisdom among world leaders that starving hordes were just around the corner. India instituted involuntary sterilization programs during the dictatorial “Emergency” of the 1970s, and China imposed a draconian one-child policy from 1980 through 2013. Renowned biologist E.O. Wilson famously wrote in 2002 that “The pattern of human population growth in the 20th century was more bacterial than primate,” and went on to argue that having six billion people on Earth was inherently unsustainable, drawing particular attention to the case of the rising population in China.

The New Story: A Population Peak?

Source of above graphic.

Yet something surprising happened in the last few decades of the 20th century, and continues to gain steam in the 21st: people are having fewer children. We are not bacteria that mindlessly reproduce as long as there are sufficient resources, and then die off once they consume all they can consume. Around the world, in hospitals, bedrooms, and family meetings, humans have made choices about how many kids they want to have, and they’ve overwhelmingly chosen to have a lot fewer than the possible maximum they could feed. The details vary by country and culture: for example, Brazil’s rapid transition into lower fertility rates may have been expedited by soap operas portraying small families (there’s surprisingly strong evidence for this). Poor treatment of working mothers in South Korea has led to record-low fertility rates, falling to 0.81 children per woman in 2021, as women increasingly choose a life and career of their own over traditional, patriarchal norms. Conversely, Israel continues to have a much higher fertility rate than most other developed countries (hovering around 3 children per woman), possibly due to a strong cultural drive to preserve the Jewish people that arose for understandable historical reasons. Overall, though, the worldwide trend is overwhelming: as countries grow richer, more educated, and more likely to allow women the freedom to make their own life choices, they end up having fewer and fewer kids. And this is happening faster and faster as the Internet and social media bring cultural change and family-planning knowledge to Asia and Africa faster than newspapers and radio shows brought it to North America and Europe. This regular, repeated pattern of fertility rate decline is known as the “demographic transition.”

This is starting to add up to big changes. We’ve well and truly left the exponential growth curve and are on our way to leveling out. The UN published a new forecast in July 2022 calculating that “By 2100 the world will contain between 8.9bn and 12.4bn people, with a 50/50 chance that its population will be shrinking.” (Quote and graphic above from The Economist). And there are many reasons to believe that the future will track the lower end of that possibility range.

For a start, the UN essentially has to take China’s word for it that its population data is reliable (because politics), but leaks from hackers indicate that China’s population may actually be over 100 million lower than the official number of 1.41 billion. (Yes, you read that right, the world’s current official estimates of how many Chinese people there are might be off by more than the entire population of Germany.).

And even if you go with the official Chinese numbers (they may well be right after all, we don’t really know) many demographers think the UN population calculations are too conservative and aren’t taking into account how fast birth rates are falling. A landmark 2019 study in The Lancet calculated that global population is likely to peak in 2064 at 9.73 billion and decline to 8.79 billion by 2100. That study predicts that 23 countries, including Japan, Thailand, and Spain, are likely to see population declines of 50% or more by 2100, and another 34 will likely see declines of 25-50%, including a predicted drop in China’s population from 1.4 billion now (officially) to around 732 million in 2100². Interestingly, The Lancet also forecasts that the American population will barely change, just increasing from around 330 million now to 336 million in 2100, although this depends on maintaining or increasing our current level of immigration.

The above map, Figure 4 in that Lancet study, shows the year the world’s countries are expected to see their net reproduction rate fall below the replacement level of 2.1 children per woman. Note how many have already passed this milestone, including much of North America, Europe and East Asia! Also note what countries will likely keep high fertility rates the longest: sub-Saharan Africa and the Middle East. In a just world, this juxtaposition would set up a perfect opportunity for economic revitalization and climate justice: as the West and Asia age, they could accept young migrants to pay into their social security and eldercare funds while providing a safer, more developed home to people fleeing climate disasters in the tropics at the same time. The smarter countries may eventually find themselves competing to shine on the “movement market” as the best destination for young migrants. Of course, it’s also possible that increasingly older voters in developed countries will succumb to fear-mongering, race-baiting politicians and limit immigration even more than it is now, losing trillions in potential economic benefits. We’ll see.

So, it looks like there’s really solid evidence that population growth is slowing down, and a decent-to-high chance that we’ll see global population decline this century. Right on cue, just starting to edge into public consciousness, we’re seeing a modern mirror image of Ehrlich-style alarmism: dire warnings about population collapse. Elon Musk said that declining birth rates and “underpopulation” were “the biggest danger civilization faces by far.” A book called What to Expect When No One's Expecting warns of “Coming Demographic Disaster.” The Institute for Family Studies reports that the share of countries with “pro-natalist” policies explicitly designed to increase birth rates has risen from 10% of all countries in 1975 to 28% in 2015³. Eastern Europe, with its below-replacement fertility rates, is particularly concerned; the conservative Polish government and the quasi-fascist Hungarian government are trying to shore up their countries’ declining fertility rates with a mix of generous carrots (direct cash benefits to families increasing with each child born) and brutal sticks (outlawing abortion and attacking same-sex couples and single mothers). And this article in Works in Progress, the single best-written case that low fertility rates are bad that I’ve read, worries about aging societies being “less dynamic” and claims that “Without new humans, growth will slow, and we will be less likely to reach the stars.”

In Sum: Don’t Worry About Population Growth-or Decline.

There’s something about population growth that seems to attract apocalyptic thinking. We went straight from decades of “starving hordes! no more room!” headlines to “childless hearths! no more babies!” headlines.

We as humanity were worried, very reasonably given the unprecedented global situation, that we were on the verge of mass famine for much of the 20th century. Then, we managed to completely reinvent global food production, feeding more people than had ever been done before. And we worried, again quite reasonably, that it still wasn’t enough, that we’d breed our way past Earth’s capacity to sustain us. Then, when women and families around the world started making different choices and fertility rates plummeted everywhere, not to a no-more-babies level, just a “we might peak around 9 billion and change instead of zooming past 10 billion this century” level, people started freaking out again.

This writer’s informed opinion: everybody chill the heck out. If there’s one thing the last few centuries have shown us, it’s that humanity controls its own demographic destiny: we will not be driven to a Malthusian trap or to a long, slow extinction by vast, impersonal forces beyond our control. There’s no “Two Or Fewer Kids Mind Virus” forcibly taking over the globe, the demographic transition is fundamentally a result of more freedom. In countries like Israel and societal sub-groups like the Amish where lots of people want to have more kids, they can and do. What we’re seeing is overwhelmingly the result of people choosing to have fewer kids, despite living in a favored time and place in human history where their kids probably won’t starve or die in infancy.

“The balance of population in the past was controlled by death: it was ugly and unacceptable. The new balance is controlled by love.”-Hans Rosling

And this writer just fundamentally doesn’t buy the assertion that a declining population means the loss of some nebulous spirit of “dynamism” or makes us “less likely to reach the stars.”

Shakespeare wrote his plays when there were less than 600 million humans on Earth. Ada Lovelace wrote the first computer program when there were less than 1.3 billion. Albert Einstein developed special relativity and Marie Curie discovered and isolated radium when there were less than 1.8 billion.

This writer is pretty freaking sure that we can continue to advance humanity, science, and culture with a world population smaller than 10 billion. And besides, nobody really has any idea what the world will look like beyond 2100. Maybe advances in genetic and cybernetic technology will drastically expand human lifespans, causing population growth to rise again. Maybe the knowledge that the population has started to decline will trigger a massive social movement in favor of having more kids, changing the culture in a new direction. Maybe we’ll automate food production and other key economic sectors to the point that we can get along fine with “only” a few billion people, and give everyone a big private estate and/or return vast swathes of land to wilderness.

The point is that right now, and as far as we can see, we’re actually in a pretty excellent place, human population-wise. We have unprecedentedly high numbers of people due to better food production, and unprecedentedly low fertility rates due to better reproductive planning and sociocultural freedom to have fewer kids if we so choose. And we have the freedom to make different choices in the future and be fairly confident that it won’t cause a mass famine. No matter what challenges humanity faces in the 21st century-war, climate change, finally ending extreme poverty, pandemics, things we haven’t even thought of yet-we’re doing it as a species that is handling its population growth fairly well, all things considered. That’s worth celebrating!

1. Fritz Haber was one of the most influential figures of the 20th century, yet also one of the most tragic and arguably one of the worst enablers of evil. In addition to his Nobel Prize-winning and probably millions-of-lives-saving work on the Haber-Bosch process, Haber was known as the “Father of Chemical Warfare.” He led development in deploying chlorine gas as a weapon for Imperial Germany in World War I, and personally oversaw the first successful use of chlorine gas in war at the Second Battle of Ypres in April 1915, which saw casualties of over 60,000 Allied soldiers. His making possible this particularly brutal form of mass murder was likely the cause of his wife’s suicide in May 1915. In the 1920s, the insecticide Zyklon A was developed at Haber’s institute, the basis of the Nazis’ later genocidal weapon, Zyklon B. However, Haber was himself Jewish, and to his credit resigned his leadership positions in protest and left the country in 1933 when the Nazis came to power. He died in 1934 before he could see the fruits of his labor being used to murder his relatives.

2. Right on cue, China’s authoritarian leadership has switched their messaging and legal incentives from decades of “one kid only” to “have more kids, as many as you want!” The one-child policy was replaced by a two-child policy in 2015, then a three-child policy in 2021. It’s not working, as the fertility rate keeps dropping and Chinese people are understandably annoyed about the policy “whiplash” after decades of totalitarian coercion, without so much as an apology.

3. Pro-natalism of course isn’t inherently bad, and often brings excellent poverty-reducing and life-enhancing benefits. For example, France has the following pro-natalist measures: income tax reductions for larger families, financial incentives for mothers staying off work to spend time with their kids, three years’ paid parental leave for both parents, government-subsidized daycare for children under three, and free full time school for children above three. It also notably doesn’t have Poland or Hungary’s anti-gay and anti-abortion laws or culture. This has led to a French fertility rate (as of 2021) of 1.79 children per women, among the highest in Europe and notably higher than America’s 1.66, Hungary’s 1.58, or Poland’s 1.46.

This newsletter’s position is all in favor of pro-natalist “carrots” like subsidized daycare, child tax credits, more accessible housing, etc., but 100% against pro-natalist “sticks” like limiting birth control, banning reproductive healthcare, or attacking LGBT, single, or childless people. We should be maximizing freedom for people to make the reproductive choices they want, both making it easier and more affordable to have kids and making it safe and stigma-free to not have kids. This is simply the right thing to do, irrespective of broader population growth trends-which are pretty OK anyway!