How is it compatible with anarchism to assert that other life forms and the planet itself exist solely to be subjugated into supporting the needs of just one species, just because that one species can (possibly; and it's not looking good on that) get away with said effort?

It’s not. We need to minimise our exploitation of other animals as much as possible.

But, that's the hidden premise in most all arguments that human population isn't a problem. Those arguments inevitably proceed by making claims that it's technologically possible to support not only the current population, but even more people.

It's being argued that population isn't a problem because it's possible to exploit the earth to support that many people (at a given level of affluence). Therefore by those standards population won't be a problem until the earth is maxed out. There's an implicit belief here that the entire earth belongs to one species (us) and it's OK to attempt to completely subjugate it to those ends.

Whether or not it's technologically possible to sustain a given amount of humans is far less relevant to the question of what the human population ideally should be than many people believe it is. (It still has some relevance, of course, but it's hardly the only relevant issue.)

Probably not. (Has any other sort of technological progress led to world peace?)

Could 8 billion be sustained thusly? Almost certainly not, which I would contend is an excellent argument that human population is presently too large.

Overpopulation is nonsense, and anticaps have known that for a long time. Here’s just one example.

Why is it "nonsense"? It's a value judgement, that the human population is higher than one believes it ought to be.

All you've attempted to show is that it's possible to maximize the human population beyond current numbers and still feed everyone. That's begging several hidden premises, perhaps the most significant one being that the human population ought to be maximized.

The more land and resources that are used to sustain humans, the less there is available for other life forms. The more the Earth is subjugated into supporting humans, the less human freedom there is to head out to the hinterlands and start ones own society. In fact, that latter freedom has almost completely vanished.

How is it compatible with anarchism to assert that other life forms and the planet itself exist solely to be subjugated into supporting the needs of just one species, just because that one species can (possibly; and it's not looking good on that) get away with said effort? That sounds like the very definition of an authoritarian attitude.

And before the standard anti-anti-civ strawman is trotted out, no, I don't want to go all Pol Pot and launch a massive global genocide.

We already know that. It’s not genocide in the trust meaning of the word, it’s billions dying from the absence of medicine and insufficient food.

Did you even read what I went on to say, or were you so busy assuming that I was an evil or ignorant anti-civ anarchist that you went on to trot out that tired strawman?

I hope that your antinatalist campaign goes well.

In many ways, it is. Birth rates are already dropping. It's been shown time and time again that if women are given access to birth control and the right to use it, they typically choose to do so.

I think it's a foolish idea, one whose advocates have generally failed to think about its downsides sufficiently.

https://www.reddit.com/r/DebateAnarchism/comments/5knkj4/is_transhumanism_a_desirable_goal/

No, but that’s partially what voluntary extinctionists advocate: if everybody were gone, pollution would not only come to a halt, it would be literally impossible.

Untrue. Certain types of pollution would become inevitable in the thirty or so centuries first following the sudden disappearance of humans. Widespread radioactive contamination, for example; there would be no humans around to tend radioactive waste storage facilities.

Well, the linked post is more than just anti-civ, it's pro-primitivist, and I am not a primitivist, but:

My assumption was that everybody would have to rely on eating wild fruits, a method which I highly doubt could sustain millions of humans, let alone billions.

Maybe you should revisit your assumptions. Nobody was civilized in 8,000 BC, yet most estimates of the human population at that time are around 5 million. That already qualifies as "millions."

https://en.wikipedia.org/wiki/World_population_estimates

Could 8 billion be sustained thusly? Almost certainly not, which I would contend is an excellent argument that human population is presently too large. (And keep in mind my opening paragraph. I'm not a primitivist, therefore I'm not advocating everyone going back to being a hunter/gatherer. I'm just pointing out that even if that were the case, it would still literally be possible to sustain millions.)

And before the standard anti-anti-civ strawman is trotted out, no, I don't want to go all Pol Pot and launch a massive global genocide. Humans are mortal. Wait 120 years and everyone alive today will be dead. Mass-murder is unnecessary; all that needs to be done is to drop the birth rate and let mortality do its work over time.

I think it could serve as a means to facilitate the creation of a post-capitalist anarchist society, if the right sort of non-state social movements exist to leverage things in that direction, for pretty much the reasons in the original post.

Of course, the devil is in the details, and those in power are certain to use all the dirty tricks in the book to prevent the above from transpiring, but it still presents an opening, I think.

How about just using a standard anthropological definition of civilization, based on the following characteristics:

1. Cities
2. Organized central governments
3. Complex religions
4. Job specialization
5. Social class hierarchy
6. Writing
7. Public works

While not all of these are anti-anarchist (I'm certainly not against written knowledge, for example), I think it's clear that (2) and (5) are fundamentally incompatible with anarchism.

Moreover, (3) also tends to be hierarchical and authoritarian, and I would argue that (4) when taken to the extremes that civilization takes it also contains anti-freedom premises (because it makes it difficult or impossible for individuals to exit society or to even grasp and critique it in toto, due to the specialization-induced lack of knowledge broadness necessary to do so).

And that's about it. Note that anti-civilization is a categorization defined by what those of us in that category oppose, therefore there's not much it tells about what we actually positively advocate. So it's a term that's of limited usefulness.