Yeah, it's easier to think environmentalism is a luxury when you're post-industrial, and your food, shelter and water no longer relies heavily on your immediate environment.
Water hygiene is a big one. You know how many cultures have major taboos against defiling wells, dumping shit in rivers? How many conflicts over distribution of water?
Clean water is something that takes effort to preserve, or everyone dies shitting their ass out.
Care of the land is another. This is pre-fertilizers, the soil quality will visibly degrade within a generation when farmed poorly, and people learn what not to do...or at least leave chunks of the environment intact so it can provide a buffer.
Finally, for flora(concern for fauna isn't such a big deal yet I think, since it's less immediate), many important medicines and drugs come from plants they've yet to cultivate successfully. Wipe them out and there's no more to use.
When you are at this level of society, making sure your environment can continue to support you is simple sense.
Of course, it just takes one Big Man with a Big Ego to order some major work to show off how Big he is to do a lot of damage. But that's one of the risks of this model.
