Environmentalists - don't make me laugh. Being dependent on local wildlife because you're to ignorant to invent agriculture does not make you an environmentalist.
As far as riches...yes they surely did raid amongst other Indian tribes but never referred to those they raided and killed as the same as "themselves" they were enemies. But perhaps you could learn about "giveaways". No they were not environmentalist in the sense of the word that has developed from the '60's. But they sure understood their environment which afforded them to live centuries off of a land that oft killed early Europeans who came here...they dealt with harsh winters, foraged for food, cultivated agriculture, irrigated deserts, and hunted.
That is essentially the point. When a society has five to six million square miles of resources to draw upon there is no need for environmentalist. Just how much asphalt do you think it took to pave an Indian village?