And not just that, but all the new diseases and pests that are wiping out species of trees here in the eastern U.S., too. The butternut, for example, an obscure walnut species: the last speciment on our mountain was in my front yard, and just toppled one calm autumn morning seven years ago. In that case, the loss of a single charismatic individual symbolized the species’ mysterious blight-caused extirpation throughout much of its range.