I really hope our civilization can go from 7 billion people to 1 billion without a total collapse. Unfortunately we might not be ready. Will we be able to keep our technological level? Our current understanding of math, physics and nature? That requires quite a lot of people to transmit and learn. It certainly is theoretically possible but in practice? It's exponential. This has the potential to creep on us really soon.

The issue lies in who those 1 billion people will be. The most anti-LGBT, anti-women, anti-education, low income cultures which have the most kids? Or a "controlled landing" in which most of the Western world doesn't become a ghost town or has its culture more or less replaced because it couldn't reproduce itself?

Is this what you are saying?:

“Feeble-mindedness perpetuates itself from the ranks of those who are blandly indifferent to their racial responsibilities. And it is largely this type of humanity we are now drawing upon to populate our world for the generations to come. In this orgy of multiplying and replenishing the earth, this type is pari passu multiplying and perpetuating those direst evils in which we must, if civilization is to survive, extirpate by the very roots.” -- Margaret Sanger, The Pivot of Civilization, 1922

In hindsight I should've probably not make 1b (1800) but rather the 1.65b of 1900 the goal, just because from a time frame and as a vision it is so much easier to communicate: around the turn of the century we already had electric streetcars, electric underground, electric lighting, motorcars, elevators, entire countries with rail networks and so on. I do not see why a slow-ish-ly shrinking population should entail tossing all of our advances since then—in medicine, computers, telecommunication, chemistry, virtually all fields, not least agriculture (although the way we do it now is utterly unsustainable). Rather, I believe that in a situation where you have an extremely high birthrate and a doubling of the population in a matter of just 15 or 30 years you end up with half of population being rather young and lacking experience; you will also, as an economy, have a hard time to build enough schools and housing. People will and already do live, in many places, in cities that are almost entirely without any built history to speak of. This is what erodes local traditions, customs, awareness; I see this and not the OP's notion of 'shrinking societies cause cultural attrition and global homogenization' (paraphrased from memory) as a major cultural problem. Population growth, not shrinkage, is a great contributor to cultural loss.

This is one of the reasons why we put together this document. We (as authors) see there being many benefits to smaller human populations on earth, but we think that any transition made needs to be made very thoughtfully.

So far we we can see, there is very little (effective) proactive action being taken to ensure that as population levels decline, things we value (like technological progress, women's rights, diversity of cultures, etc.) are protected.

Addendum Quote "The economic systems of virtually all developed countries are predicated on an assumption of constant growth"—I'm with you that shrinking societies will be facing a wholly new set of societal problems. However an economic system that is predicated on constant growth will necessarily fail at some point in the future because physics. We as a species have to find ways to prevent that from happening. To keep adding people is not an option. If we can live with 10 billion people or maybe with 20 billion people (shudder, but who knows) then at some point–100 billion? 200 billion?–there must come a point at which it is with absolute certainty not going to work.

>However an economic system that is predicated on constant growth will necessarily fail at some point in the future because physics.

Nonsense. And the audacity to add "because physics" at the end. Newton himself proved this wrong.

1+ 0.5 + 0.25 + 0.125....

Is this sequence constant growing? Yes. Is this sequence infinitely increasing? Yes. Does this sum up to a finite value? Also yes!

You are right and I am glad I didn't write 'because Maths'. The sum you're quoting from is monotonically growing but at an ever shrinking clip. However, the series does not describe the kind of growth that our economy seemingly needs and our politicians like to promise, nor does it AFAICS describe the OP's idea of continued population growth given his recommendation to shun shrinking populations with fertility below replacement rate; theirs is a constant or in the midterm increasing growth and notwithstanding [minority opinions](https://www.youtube.com/watch?v=w-I6XTVZXww) claiming that 1 + 2 + 3 + 4 + 5 + ... equals -1/12 such a series cannot have a finite sum, hence is physically unfeasible to represent.

Cute counterexample, I'll grant you that, but the parent posts were – if implicitly – talking abound unbounded growth.

Bounded growth on the other hand might mathematically indeed continue for an infinite length of time, but for all practical purposes can most certainly be rounded down to zero past a certain point.

But that's not our growth. Our system suppose constant exponential growth. And to use your maths:

1% + 0.5% + 0.25% + 0.125%....

Is this sequence constant growing? Yes. Is this sequence infinitely increasing? Yes. Does this sum up to a finite value? _Sadly no_

I'd have to brush up on my math but even that feels bounded. Per cent is just division by 100, you take it out as a common divisor and you still arrive at the same sum.

Unless you mean something like

  1 * 1.01 * 1.02 * 1.03.....

Which is indeed unbounded.

When creating this document, our goal wasn't to give people the impression that our populations should expand in number indefinitely (especially not on Earth alone). You're right that expecting the planet to shoulder indefinite population growth is impractical.

We're just trying to highlight the hazards of population decline that hits humanity like a tidal wave and produces unnecessary suffering and damage. There are ways for populations to sustainably decline without wiping out entire cultures, for example.

We, personally, care a lot about memetic/cultural diversity and worry that a population collapse for which we don't prepare will eliminate loads of perspectives that would otherwise contribute great new innovations and technologies to humanity's future.

We also think it's important that people know that population decline will affect certain fundamentals upon which their lives are based (e.g. "I put all my retirement savings in the stock market because on average the stock market always goes up" isn't going to be a healthy thought when population decline accelerates).

I'm happy to hear that the overall perspective is relatable and sober although I can not agree on 'tidal wave' and 'apocalypse'. 'Antideluge' or 'negative tsunami', anyone?

You know, you could even blame Russia's current war on its declining population (their leader desperately trying to keep together the country and the people) but I know of another Great War that was fought under the pretense of having the right to expand b/c of a growing population (and they happened to have laid their eyes on the same stretches of fertile farmland). I do not believe in either, the reasons being in both cases largely unrelated to demographic growth or lack thereof. Given that this former event did cause stocks to take a plunge, well, that's what trouble and disorder give you, trouble and disorder. And that can have so many reasons that I'm not afraid of the shrinking population => economic setback linkage, even if and so far as it does have predictive value.

Some say the world will end in fire,

Some say in ice...