There are ways to grow good yields without tons of fertilizer. See Gabe Brown et al [1].
Usually, the forest is used as an example. Forests are indeed highly "optimized" and full of life, but they are also mostly closed systems. What is produced by the forest is consumed by the forest. We don't want a closed system, we want a system we can tap into and feed our million-people cities. I don't know what such a thing will look like, but most likely not a forest.
The other, more specific issue is about nitrogen. Half of the nitrogen in our body comes from artificial fertilizers, extracted from atmospheric nitrogen using the Haber-Bosch process. If we stop using artificial fertilizers, how are we going to get that nitrogen?
We are almost 8 billion and counting. We are stretching the limits of what nature is capable of. And I refuse solutions that involve limiting population (i.e. genocide), or make our life miserable. Can perma-cluture (or similar ideas) achieve that? I like the idea of a more integrated system (less monoculture), how to do it with reasonable manpower is an open question though, but I also think that artificial fertilizers are a necessity at that point.
We are between a rock (these kinds of extreme solutions) and a hard place (allowing current trends to continue because there are no clear solutions which can be counted on due to corruption/greed/short-term-thinking, which aren't going away).
I see no way around anticipating increasing chaos for the foreseeable future. If you care about the long term health of yourself and your community/family, you should probably be looking for a region with plentiful local resources and inhospitable terrain.
https://en.wikipedia.org/wiki/Milorganite
At scale, in Milwaukee. There have been concerns about contaminants though. Still production and sales have been ongoing since 1926.
> If we stop using artificial fertilizers, how are we going to get that nitrogen?
Many legume crops are able to capture their own nitrogen from the atmosphere by using bacterial symbionts. Crop rotations with legume crops are one way we already take advantage of this. Genetic engineering could allow more types of crops to form symbiotic relationships with these bacteria.
[1] https://www.theguardian.com/global-development/2014/may/13/m...
What's your limit on population growth? When we all have one square meter of space? Is that when it should stop? I'm really curious to know where you draw the line.
I'm increasingly of the mind that humans viewing themselves as apart from the biosphere, rather than an element within it, is a flawed mindset wholly responsible for our current predicament. It seems unlikely that digging ourselves deeper into that hole will bring about a positive outcome for humankind or the natural world on which we have always depended.
The biosphere will always be a resource we exploit. Yes we are part of it, but as true as it might be, it is not very helpful. I think it is more important to think of nature as a kind of machine that you have to maintain. Kind of like a car engine: regular oil change, proper fuel, make sure parts stay clean, don't red zone and let it cool when it needs to. Otherwise your car will not get you where you want to go.