24, 1855, Henry David Thoreau sat down to his journal to reflect on all the ways his homeland had changed since the first English colonists had arrived on the shores of Massachusetts two centuries earlier. For several days, Thoreau had been reading the accounts of some of the earliest settlers. Compared to the America they had found, Thoreau reflected, his experience in the forests was like listening to a symphony played without most of the instruments. As he further considered in what became his essay, "To Know an Entire Heaven and an Entire Earth," Thoreau decided that the European colonists had acted as demigods who had impoverished his world by, in effect, plucking from the heavens many of the best and brightest stars.Only a span of years later and a continent farther west, the Crow leader Plenty Coups, speaking of his vision atop the Crazy Mountains wherein he witnessed the replacement of buffalo with speckled cattle, summarized the Indian perspective on that change with this cryptic remark: "After this, nothing happened." Even Western pioneers who experienced the change were shocked. As L.A. Huffman, the famous Montana photographer, remembered it, when he first came west in the 1870s, "This Yellowstone-Big Horn country was then unpenned of wire, and unspoiled ... One looked about and said, "This is the last West. ..." There was no more West after that. It was a dream and a forgetting, a chapter forever closed." From any perspective, that great world of sunlight and grass, endless forests and clear streams anyone could drink out of anytime, now seems central in our experience as a people. Being born literary, Native American, or a sensitive pioneer was and is no requisite to mourning the loss of a world like that, a wilder life on a wilder continent.Most of us interested in the natural world here on the eve of the 21st century understand Thoreau's sentiment: "I am that citizen whom I pity." Looking out my windows at the American ...