What are the motifs in Crossing Open Ground by Barry Lopez?

At the same time as he's describing and/or commenting on various positive aspects of humanity's relationship with nature (including the creative inspiration portrayed in "Gone Back into the Earth"), the author also repeatedly, and pointedly, comments on how humanity has exploited, and continues to exploit, nature in insensitive, ultimately destructive ways. Here it's important to note that the author makes this point not only in terms of his contemporary experiences of such exploitation (such as those documented in "A Reflection on White Geese" and "The Bull Rider") , but also refers to particularly vivid historical examples of such attitudes and practices ("The Passing Wisdom of Birds.")