In this June 12, 2018, photo, U.S. Forest Service scientist Paul Schaberg stands beside a healthy red spruce tree growing on Mount Mansfield in Stowe, Vt. Schaberg is co-author of a new study that found that the tree species, once heavily damaged by acid rain, is rebounding in five Northeast states due to stricter air pollution regulations and a changing climate. (Lisa Rathke/AP Photo)