Hemlock is a vital component of the New England forest system, and is the third most prevalent tree in Vermont. Providing protection from erosion along stream banks, food for deer and wildlife, and shelter for deer in the winter, hemlock is also valued both as an ornamental and as an important source of lumber. Where hemlock occurs in pure stands in that region, the most commonly observed tree species to succeed it is black (sweet) birch. In contrast, in the southern extreme of its range, hemlock does not typically occur in pure stands, but in linear riparian areas and other moist sites.
The U.S. Forest Service Southern Research Station suggests the hemlock woolly adelgid is killing hemlock trees faster than expected in the southern Appalachians, and rapidly altering the carbon cycle of these forests. According to Science Daily, the pest could kill most of the region's hemlock trees within the next decade. According to the study, "adelgid-infested hemlock trees in the South are declining much faster than the reported 9-year decline of some infested hemlock trees in the Northeast."