>Humans dramatically increase and multiply the amount of suffering in the world
I don't believe that. All the animals that are alive today would die in pain in anyway, no matter what humans do. Every deer that's shot is one not eaten alive by wolves, or starving to death. Does it matter whether a bird drowns in an oil slick or thrashes in the mouth of a crocodile?
Animal life is nasty, brutish, and short.
Even if we killed a large fraction of the animals on the planet in a painful way, that would be a blip in the colossal historical tapestry of pain, and as there'd be fewer animals in the next generation, it would probably be morally neutral from a consequentialist perspective: the overall, average amount of suffering would be constant.

>there's already suffering in the world, so why do anything about it?

No, that's not what I'm saying.
If I care about suffering, I only care slightly (instrumentally) whether it's caused by humans or nature. You seem to care a lot, but I don't. If I 'm going to decide to care about the suffering of animals generally, then that's going to lead me to certain conclusions.

If humans are going to take responsibility for animal suffering, we should take responsibility for all animal suffering, meaning we should reorganize/destroy the ecosphere, replacing it with something more moral. We should also become able to be wise stewards of the new world, of course.

But if I put myself into the mindset of "I care about the suffering of animals", then going from that to "humans should be hippies and let nature be, man" seems pretty evil. If the suffering of animals is bad, then nature is bad and should be stopped.

>For the most part, a balance is achieved. Animals and plants take what they need in order to survive, and there's no other way for them to survive
No, animals and plants take as much as they can get, and most of them don't get enough. The ones that don't get what they need in order to survive die, by starvation or by being got by a predator. The balance here is on a see-saw greased with the blood of living things: if I built a system like that, where little furry animals reproduced until there was no food left and then competed increasingly frantically, with some of them eating the others, and then turned around to you and said "look, they've reached a balance! As many of them die horribly as are pumped out! :)", you'd call me a psycho. You're only excusing it because it's natural.
It's mathematically beautiful, of course!

>The argument isn't to rid the world of suffering, because how could that even be accomplished?

Wipe out the natural world: Evacuate humans and scans/genomes of all the animals we're interested in somewhere else and build a paradise there; then wreck the surface of the earth so that nothing bigger than a bacterium can survive. Maybe we could engineer runaway global warming, to turn earth into something resembling Venus? Deliberately irradiate the whole surface to the point that nothing survives? Build lots of orbital mirrors to increase the solar irradiance and boil the oceans? Grey goo? Dream big!

If this sounds horrible to you, then I guess you have an aesthetic preference for forests. That's fine, but remember that forests and jungles are hell-pits of torture.