Well, clearly I am not always good at responding promptly :)
Re: nonhuman individuals, I touched on it briefly in chapter 2 but I don't know if you'll be satisfied with it.
Realistically, these first few chapters mostly exist to explain the motivation for frugal living. Most of what I want to write about in the book revolves around how to maximize your quality of life while minimizing expenses -- because I think the only real expertise I have to offer is my own story of going from $70k/year to $10k while gaining more freedom and life satisfaction. I can rant about climate change and suffering but I don't have any special knowledge in those fields.
If people become more frugal -- which automatically lessens their demands on the environment -- then they can either work less, which frees up time to enrich themselves / rest / heal / engage in activism / work on creative projects, etc.; or, if they like their job, they can keep the same income but give away a lot more of it.
I think for this kind of thing to catch on, people have to do it in a way that actually helps them thrive and feel amazing in life. If being frugal looks like a punishment then of course nobody will want to do it. So I am kind of pushing that as a starting point, and once people are in a place that they've secured that extra free time or that extra money, they can decide what helpful things they want to do after that.
Not sure why I went on that tangent or what it has to do with animal welfare, but there you go :) Hope you're having a nice weekend.