A graph like the one above should make you nervous. A line going nearly straight up indicates a “bubble” situation — and all bubbles must pop. Dot-com bubble, U.S. housing market bubble, Dutch tulip bulb bubble; historically, there are dozens of examples of market bubbles. The above graph references population, not markets, but there are just as many examples of animal population crashes (for example the chilling story of the reindeer of St. Matthew Island in Alaska). Bubble dynamics are always the same; exponential growth is never sustainable, and is thus followed by exponential shrinkage.

Human population can’t go up indefinitely. Something will eventually limit (and reverse) our growth. It might be food, it might be energy, or it might be cultural factors. “Doomers” predict human population decline will be brought on by hard limits to oil and food production, and will be accompanied by chaos, violence, and strife (Thomas Malthus, with his predictions of overpopulation and mass starvation, could be considered the original doomer).

Some, like the environmental writer Fred Pearce, predict a rosier decline. Pearce predicts that voluntary reduced fertility (women choosing to use birth control) will allow human population growth to taper off and eventually decline gradually, with a a minimum of strife. We’ll avert economic catastrophe by working into old age; we’ll “harness older people as a resource.”

My bullshit detector goes off listening to both lines of thinking. The doomers and the optimists are both overlooking important variables. To get a complete picture of human population decline scenarios, what factors do we need to consider?

Why So Many?

Why are there so many of us?

The short answer is that we invented artificial fertilizer before we invented birth control.

Historically, our ability to produce food, as a species, was tightly controlled by the availability of natural fertilizer (animal poop, food scraps, etc.). With the invention of the Haber-Bosch process, we could suddenly create ammonia-based nitrogen fertilizer out of thin air (by combining hydrogen, from natural gas or coal, with nitrogen, from air). As you can see in the graph above, human population was already rising quickly in the 1800’s. But when the Haber process became widespread, in the early 1900’s, we really took off. Eat, breed, eat some more!

The thing is, most human beings don’t actually want to have a large number of children. What we want to do is have sex (evolution made sure of that). Evolution also made sure that most of us look after our kids to some extent — we very much want to see them well-fed, healthy, and surviving into adulthood. But if we’re given a choice to have sex without having children, we’ll often go that route. Raising children is difficult and expensive. People who don’t know that quickly learn it as soon as they have their first child. My point is that there is no natural impulse to radically overpopulate the planet with human beings.

Unfortunately, we didn’t figure out a way to reliably have sex without have children until the 1960’s. The Pill changed everything. Women could now control the fertility process (men are less motivated to responsibly use birth control, because the burdens of pregnancy and infant care fall primarily on women).

Women, when they have access to birth control and access to healthcare for their existing children, universally choose to have fewer children. As the availability of birth control, decent health care, and women’s literacy spread in developing countries, fertility rates are rapidly dropping. In most developed countries, fertility rates hover around replacement level, or lower.

Modern agriculture, culminating in the Haber process (and later, genetically modified high-yield crops), removed a hard limit to population growth that had existed for centuries. This allowed human population to explode. Still, we are thinking animals, and we’ll make reasonable procreation choices if given the option. What if oral contraception had preceded Haber-Bosch by a few decades, instead of vice versa? If oral contraception had been invented in 1910, and the Haber process in 1960, global population would currently be under 3 billion, and already starting to drop.

Three Variables

The three most important variables for how human population will decrease (gradually and peacefully or rapidly and violently) are food reform, cheap energy, and global women’s rights.

Important non-variables are climate change (it’s happening, and will be accompanied by floods, droughts, and major local food production disruptions), and culture bleed (increased inability for an isolated culture to remain isolated, due to internet/global media penetration).

If we zoom ahead thirty years, to 2041, we’ll most likely have clear answers to the following questions:

1) Have global food production techniques been reformed? This would include:

sensible ocean management (large protected areas, protected reefs, prohibition of destructive fishing techniques)

widespread ultramodern polyculture farming (hyper-efficient land use, less reliance on chemical fertilizers and pesticides, tree planting to protect topsoil from wind and flooding)

decentralized food production (greater number of smaller farms, more local production, lower shipping/transport costs)

2) Do we have reliable sources of cheap, clean energy? These could include:

ultra-efficient solar cells, large solar energy plants

cold-fusion (probably not, but who knows?)

clean, safe nuclear (not popular right now because of Japan, but if the Chinese can get pebble-bed reactors to work, it would be much safer than coal mining)

modern grids that facilitate low-loss energy transport, electric vehicle charging, etc.

widespread home energy production, totally decentralized energy production (throw your plastic trash into home “electricity maker”)

other renewable sources (wind + compressed air, hydro, geothermal, etc.)

3) Do the vast majority of women in the world have equal rights? This would include:

access to education

access to birth control and quality health care (for self and children)

voting rights

right to work, equal pay for equal work

In short, the closer we are to three no’s, the more likely the doomers are right. Global population may keep rising quickly and then crash hard and fast, accompanied by war, starvation, and disease.

If we can answer yes to all three questions, then Fred Pearce’s vision may be closer to the truth. Global population growth will taper off gradually, and then decline gradually and peacefully.

Other Factors

In addition to these three variables, there are some black swan type events that could wipe out human population, including:

Giant meteor strike that globally blocks sunlight for several years Supervolcano eruption that globally blocks sunlight for several years Major nuclear war; fires that globally block sunlight for several years. Engineered virus for which none of us have any resistance.

There are many other possible calamities, but I don’t see natural viruses, climate catastrophe, economic collapse, world wars, or robot uprisings taking out more than a few million of us at a time (excepting a robot uprising, we’ve been through them all, and there still are close to 7 billion of us). To get into multi-billion level casualties, you need to cut off human beings from the sun, or engineer something incredibly nasty on a biological level.

There are also other factors that will definitely slow down or provide a boost to human population growth, but to a lesser degree than the big three or a black swan event, including:

The spread of secularism, or religiosity (see my previous post). The spread or regulation of endocrine-disrupting chemicals that significantly and negatively affect fertility (like bisphenol-A). Civic policies relating to healthcare and child care (universal healthcare, public preschool, and mandatory maternity and paternity leave all encourage higher birth rates).

2041, The Most Likely Scenario

Here’s my prediction.

In 2041, we will not have a cheap source of energy; energy will be more expensive than it is now (by 100% or more). However, energy production will be more diverse and less centralized. Some countries will have extremely efficient, clean energy systems. Other countries will still be digging up coal and burning it. Oil will still be our primary energy source, but it will be much harder to extract, and much more expensive.

Food production, for the most part, will not be reformed (or reform will be too late). The oceans will be mostly depleted (though some areas will be protected and recovering). The fish we eat will be mostly farmed. Food production will only be 15% reformed to modern polyculture, primarily to produce high quality food for the rich, but also some pockets where poorer countries have aggressively promoted agricultural reform. We’ll lose massive amounts of food to flooding, drought, and crop disease from global climate change. Fertilizer and food will generally be more expensive (by 100% or more).

Global literacy, education, and access to birth control will continue to rise, and fertility rates in developing countries will continue to plummet. Isolated cultures and countries will be unable to resist the pervasive, virus-like spread of modern Western values via mobile internet devices. Though this may have many noxious effects (spread of shallow pop culture and consumerism), it will also result in more equal rights for women, access to free education (like Khan Academy), and many other positive effects.

Global population will peak at 9 billion in 2060, somewhere in between the low and medium U.N. projections (see graph above). Population decline will be due primarily to couples choosing to have fewer children (high cost of living + availability of birth control).

Higher cost of living will result in more small-scale wars (most battles over food and energy resources), and more revolutions. The most stable government configurations will be those that manage to keep their poorest people well fed and adequately housed. Governments that fail to do this will experience massive protests, revolutions, and military coups.

Population change will be experienced most acutely on the municipal and national levels. Societal collapse due to depopulation will be more common than societal collapse due to overpopulation. The collapse of the Soviet Union can be interpreted as a depopulation event. Russia, Japan, Italy, and other countries with low birth rates will need to reverse (via increased immigration and birth incentives) or manage their population decline, or risk collapse. Some cities, like Detroit, may entirely depopulate if they don’t manage their decline (perhaps via aggressive rewilding), or provide massive incentives to attract new residents (like giving away land and houses, along with multi-year property tax waivers).

In other parts of the world, massive overpopulation combined with high food and energy prices could lead to malnutrition and stunting, greater incidence of disease, violent revolutions, tribalism, criminal gang wars, and all manner of ugliness. China and India will continue to be the most populous countries, with most of the world’s poor, and civic policies in these countries will influence billions of lives. Choices related to food production, energy production, and social welfare will stave off suffering in some populous countries, and invite it in others.

Worldwide, higher energy and food prices will stagnate the global economy. The poor and remaining middle class will consume fewer goods and services because more of their income will go to food and energy. Governments that support the poor and middle class with progressive taxation (taxing the rich, who don’t spend their money anyway), and providing quality public services (healthcare, education, and infrastructure) will fare better, and be less vulnerable to revolution.

A major depopulating black swan event will occur sometime before the sun explodes, but human population will have already peaked before then.

Population will peak well before we migrate into space (terraform Mars, or even have a constantly inhabited, self-sustainable moon base).

It Could Be Worse

Is it time to start hoarding ammunition and tins of sardines? For most people, probably not. However, the most likely scenario does point to a few decades of much higher energy and food prices, along with general economic stagnation.

Successful food reform or cheap energy could change things dramatically. The world’s poor would be much better off, and so would the global economy. All of us would have more money to purchase goods and services if we had to spend less on food and energy.

Fortunately, birth control and family planning will ultimately save us from a massive human die-off. We’re already slamming on the brakes, voluntarily, well before we starve to death like the reindeer of St. Matthew Island.

2100 and Beyond

Once we’re on the downslope, the major problems we’ll be facing as a species will be global economic stagnation, and municipal depopulation.

Eventually human population will decline, and renewable energy will advance, to a point where food and energy once again become cheap. This will provide a boost to the global economy, freeing up massive amounts of wealth to purchase goods and services. Until then, nations that want to thrive will need to do whatever they can to avoid rapid depopulation, support the middle class and lift up the poor (thus freeing up money to buy goods and services and support the economy), maintain public trust, and generally encourage economic activity.

Cities will need to voluntarily shrink, rewilding large portions or converting abandoned lots to food or energy production. As we’re currently seeing in Detroit, this kind of process requires vast amounts of political will and community organizing, and is difficult. Some cities may simply decay to the point of total abandonment, to be reclaimed by the elements within a few decades. This is already happening to many houses in Detroit.

Until energy and food production are once again growing faster than demand, we’ll experience a new Dark Age. What the doomers don’t realize is that this age has already begun. Look at the headlines. Oil and mineral wars, revolutions, stingy spending on “non-essentials” like culture and science — we’re already in it! Peak oil already happened. For most of the developed world, the “ticking time bomb” of global overpopulation will explode slowly, over a 100 year period that we’re already well into. It won’t mean guns and canned food, but it will mean shorter vacations, higher unemployment, choosing to have fewer children, and more vacant lots.

When Will The Next Golden Age Begin?

I hope this post hasn’t left you feeling pessimistic. I actually feel more upbeat about the future than I did before I started researching and thinking about this topic. Our current Dark Age won’t be nearly as bad as the original Dark Ages. Some of us will die prematurely from oil wars, lack of healthcare, or working three jobs, but most of us will muddle along as usual, with our tight budgets and zero to two children. The wise will be just as happy as ever, deriving pleasure from family, friends, food, sex, nature, spiritual or religious practice, novels, music, film, sports, and other low-cost human pursuits.

When the energy production curve once again overtakes the energy demand curve (perhaps sooner, due to massive innovation, or perhaps later, due to less innovation and decreased population), human beings will start getting interesting again. We might start to take on some huge, expensive projects, like creating a space elevator, interstellar starships, or virtual worlds indistinguishable from reality (holodeck!).

It’s even possible that a new Golden Age could be triggered before energy production catches up with demand. While the internet is mostly used for porn and looking at funny cat pictures, it also happens to be a fantastic medium for idea sharing, knowledge acquisition, and active (if rarely civil) political and philosophical dialogue. I can’t rule out the possibility that the internet will trigger (or has already triggered) a second Enlightenment.

Modern civilization might collapse entirely, but I’m optimistic that once we’re “over the hump” (of population peak), we have some excellent times ahead.