Endless growth is simply not sustainable.
Throughout history, mankind has been exhorted to "go forth and multiply" by various religions and governments. For the most part, the real message was for people in our tribe to multiply, so they could out-populate other tribes and serve as foot soldiers (and later, cannon fodder) in wars and skirmishes to take over others' lands and properties.
The side with less people always loses.
Population growth serves the needs of business and governments - powers-that-be. If you are sitting atop a pile of dung, well, your status is determined by the size of the dung pile. On a smaller scale, we see this in business as well - even on a mid-level-manager scale. If you run a department of five people, you might not make much. But if you can grow your department to ten people, well, you can justifiably ask for a raise, as your responsibilities are greater.
In the business world, this is called "empire-building" and was addressed in the book, Up the Organization. People build small empires - little fiefdoms - within an organization, often at the expense of the greater organization itself. Elon Musk is a narcissistic idiot, but one clever thing he did at Twitter was to disband the PR department. You don't need a dozen or more people to write press releases or say "no comment" over and over again. Departments like that expand and grow as a business gets larger and makes more money. It is only when business goes South that you realize that your "HR Department" was vastly overstaffed. Parasitic functions on a business often expand not out of necessity, but because of the necessity of the department head to have greater status.
But getting back to people and growth, the Republicans have a little organization I call the Club de Growth whose goal is endless growth of everything - people, business, exploitation of resources, etc. It is a nice fantasy, but there has to be an end game. Growth increases the value of fixed resources such as land, over time. So if you own land, growth works in your favor. Even if you own stocks, it works in your favor. If the population increases, demand for products increases, and the company you own stock in, expands and sells more product.
It is, nature's Pozi or Pyramid scheme. A Pyramid scheme would "work" provided there was endless growth in the scheme and the participants would live forever. But like any other pyramid, the people paying in at the bottom are paying for the fat pay-outs for the people at the top. So long as a new, lower level of pyramid is always being added, well, it's all good. But perpetual pyramids don't exist.
What we are learning right now - and what members of the Club de Growth don't want to admit, is that there is an end-game to perpetual growth. Long before we actually run out of natural resources, people will end up fighting one another over scarcity of existing resources. World War II, for example, was a fight over resources. Hitler wanted an expanded Germany with room for growth in lands seized from Slavic States such as Poland and Russia. Japan bombed Pearl Harbor after we denied them oil for their military machine. It is all about resources more than ideologies and government types. When push comes to shove, however, Democracies are always on their heels and the fascists are doing the shoving, as we see right now in Ukraine.
Some have argued that mankind needs to become a "space-faring species" capable of colonizing other planets or even living in artificial habits in space. Once Earth becomes too over-crowded and destroyed, we will simply trade it in, like a well-worn used car, for a shiny new Mars. Simple, right?
It is a trope used in Science Fiction - where exploration and colonization of other planets is deemed parallel to the exploration of the "New World" and the colonization thereof. Some authors, such as Heinlein, even posit there would be life on these other worlds, but like with the Americas, we would push them aside and colonize anyway. It isn't that simple, of course.
I noted before that traveling to Mars isn't like going to the Moon. And living on Mars would be like living in a microwave oven - that is also a deep freezer. Inhospitable is an understatement. Of course, you would walk around on the surface of Mars in a space suit - for a time - but living there would require a continuous supply of goods from Earth, sent at great cost. The idea of "colonizers" being shipped from Earth by the thousands or millions, is ludicrous. It wouldn't be the new Ellis Island.
Granted, Mars is more hospitable than, say, Venus, where your space craft would be crushed in an instant like that stupid Titanic submarine - or slowly eaten through by the acidic atmosphere. Life on Earth is a unique thing - and uniquely adapted to Earth as well. The other planets of our Solar System simply would not support life as we know it, outside of some very expensive bubble.
Exoplanets that would support our life probably exist - there as so many trillions of stars out there. But they are so far away. And since we don't have imaginary technology like anti-gravity and faster-than-light drives, those stars will always be out of reach.
No, we are stuck on this planet, like it or not. And thus, infinite growth isn't possible. Sure, we can grow more - by displacing more and more species from the planet, as we have already done in recent years - a trend which is accelerating. But as we grow, however, other forms of "life" will find ways to exploit this new human resource. The CoVid virus was just a warning shot. Other forms of viruses and bacteria and parasites will adapt, over time, to this new, readily available "food source" called humanity. Our ability to kill off these new predators will be the real test - expect more pandemics as the population increases and population density increases as well.
So, what's the alternative? Well, some folks - going way back - have argued that maybe perpetual growth isn't the answer, other than for the few people at the top. Maybe the world would be a happier place with fewer people and more wild spaces and more biodiversity. Maybe we don't need five billion little miracles after all.
The problem is, of course, there is no way to enforce this. The poorest and least-educated of any society, or of societies, tend to have the greatest population growth. In many third-world countries, having many children is the only way to insure that some survive childhood diseases and accidents, so that someone will support you in old age. As I noted, many religions have, as their primary tenet, that you should "multiply". It is pretty hard to fight that sort of thinking. Not only that, but sex is a powerful inducement to multiply, and in cultures where there is little else to do, sex becomes a major recreational activity.
And of course, most religions decry the use of birth control, abortion, homosexuality, or any form of sex that is not linked to procreation. It's all about the multiply!
There have been two recent "experiments" in population control, with mixed results. In China, they enacted a two-child policy in an attempt to limit population growth. China had always been famous for its "endless hoards" of people - a notion used to scare Westerners. For example, there is an old trope that if you marched the entire population of China, 100 abreast, past one point, the parade would never end, as the population would keep increasing. Of course, the same could be said for any country - you'd just have to adjust the width of the parade, accordingly. For the most part, these sort of things are just anti-Asian bigotry.
China, having a strict, totalitarian government, could enforce this "two-child" rule and the results were interesting. Everyone wanted to have boys, and girls were often abandoned, given up for adoption, or even murdered as infants. The economy sort of stagnated as well, and the government did an about-face and instituted a new policy promoting people to have more children.
So population control failed? Maybe. Maybe not. One reason the policy was abandoned, I think, is that the Chinese leaders wanted to sit atop a larger dung hill, and increase their standing on the world stage. To do this, they needed to expand their economy, which meant they needed more and more workers. They also wanted to expand their military, which meant they needed more and more soldiers. They were least concerned with the plight of either the workers or soldiers, of course.
The second experiment was unintentional, in nearby Japan. The cost of living in Japan is so high that many young people gave up on the idea of owning a home and raising a family - a sentiment that is being echoed in Western countries as well. Japan is aging and population growth is stagnating - and their economy has stagnated as well. Their mono-cultural society does not lend itself well to immigration, as immigrants stand out like a sore thumb (or as in a purported old Japanese saying, the "nail that sticks up, must be hammered down").
Now, when I say the economies of China and Japan "stagnated" as a result of reduced (or zero) population growth, that is not to say everyone became unemployed and starved to death. No, what it means is that the people who owned stocks didn't see increased profits over time and the economy - as you might expect - became static. This is not necessarily a bad thing, of course. As I noted before, during the recession of the late 1970s and early 1980s, I still had a job - as did 90% of the population - and everyone still got up in the morning and went to work and put food on the table. It just wasn't the dizzying growth of later on (particularly in the Clinton era) that was countered by later recessions, of course.
Maybe a static economy isn't such a bad thing. But an economy that lurches from excess to want, again and again, can provide huge windfalls to certain individuals and huge disparities in wealth as well - as we are seeing today. But it seems that mankind cannot figure out a way to live without endless growth. We will have to re-invent economics to live in a zero-population-growth society.
Of course, this is all just fantasy. So long as teenagers get horny, there will be population growth. It is hard, if not impossible to fight this primary urge. Totalitarian governments may be able to enforce such a ban on child-rearing, but in a Democracy, it is a non-starter.
The irony, of course, is that the vaunted colonization of space (or other planets) would be predicated on strict population control. When every breath you take is manufactured, you cannot simply decide to have 10 children - or even one - without permission and permits from the authorities. As I noted before, life on Mars would be like living under a strict dictatorship.
But what about Japan? Or the US for that matter? In many instances, it appears that societies stop growing after a certain point. Maybe this is some signal the brain sends via pheromones or something that "hey, this is enough" or maybe societies get tired of growth. Or disturbingly, perhaps it is more like rat utopia After mankind reaches a certain level of prosperity, it just gives up.
The chart above illustrates age pyramids for rapid growth, slow growth, and zero growth societies. When I was born, our age pyramid in the USA looked like the rapid growth model. Today, it is more like the slow growth model. Many middle-class people are deciding not to have kids, or if they do, only two or so. Oddly enough, you would think the Club de Growth would be all-in on increasing immigration to increase growth - but they are not. It is an odd situation. So, in a way, our country may be headed toward slow or no-growth, organically.
It is a hard puzzle to crack, but human brains have cracked harder puzzles in the past - developing the secrets of the atom, blasting rockets to the moon, figuring out new and unusually cruel ways to kill one another - that sort of thing. Our ability to solve problems has increased crop yields from year to year, but like anything else, there will be an end-game to that as well. There is still a lot of headroom there, as much of what we grow we don't eat, but feed to animals which we then eat - it is a very inefficient system, and "fake meat" is just the next logical step in increasing the number of humans the planet will support. It is not some option, but a reality we will eventually face, if humanity lives that long.
We could easily double the population of the planet by going vegan, crowding into cities, and using mass-transit. But it wouldn't be much of a life, I think. In many parts of the world, people already live like this - parts of the world where people are giving up on the idea of having children.
But like I said, long before humanity reaches that point, they will go after each other and fight over resources, as we indeed are seeing today in many parts of the world. And I don't expect that to get better, over time.
Cheerful thoughts!
