Outside of ideas like ‘we should not exterminate entire species’ and ‘we should not hunt so much that we ruin hunting grounds for future generations’ it does not seem obvious to me.
I guess maybe we are so far gone that the only thought is to damage control.
There's a YouTube video I like, called "The Chinese Farmer," by Alan Watts.
The gist of the video is that reality is so unimaginably complex that we cannot know if a given change is going to be a net positive (over what time frame?) or a net negative (again, over what time frame?).
This pretty much informs my thinking these days, and when something happens that I notice, I find myself more able to refrain from labeling it as either good or bad.
Wasn't familiar with this video myself, so I searched it up. Passing it along for the next person:
https://www.youtube.com/watch?v=byQrdnq7_H0
I like the message as well.
Human pollution creates new niches that didn't exist before. Microbes in particular can adapt to them in dramatic ways, increasing genetic diversity. Surely we don't want to promote diversity by finding novel ways to pollute. Biodiversity can increase as a sick ecosystem decays, so sustainability is a crucial consideration. Below some threshold more radiation increases biodiversity. But is it worth more mutant babies?
So changes in absolute quantities of biodiversity might not be a good way to measure the health of the environment. Optimal biodiversity probably depends on for who, and is different each species and niche.