Nature in America is not what it used to be. This is not to say that the
observed regularities of the natural order have been suspended, which would be absurd, or to say that natural systems have been deeply altered, which would be truistic, but rather to say that nature no longer means what it once meant. Always a somewhat vague and vagrant category, nature has once again shifted its ground. Many aspects of this change in the meaning of nature fall outside the purview of geography, and of this book, but at least two pertain directly to the geography of the United States at the beginning of the twenty-first century.