The Indians' real record on the environment was actually mixed, and I give the details in my new book, 33 Questions About American History You're Not Supposed to Ask. Among other things, they engaged in slash-and-burn agriculture, destroyed forests and grasslands, and wiped out entire animal populations (on the assumption that animals felled in a hunt would be reanimated in even larger numbers).
On the other hand, the Indians often succeeded in being good stewards of the environment—but not in the way people generally suppose.
In other words, the American Indians were human beings who responded to the incentives they faced, not cardboard cutouts to be exploited on behalf of environmentalism or any other political program.
The short version is that yes, the Indian record was mixed. But it's far superior to the Euro-American record, which has been atrocious.