A correspondent from the Friends of Allegheny Wilderness writes:
The non-native and invasive insect hemlock wooly adelgid (Adelges tsugae) has killed eastern hemlock (Tsuga canadensis) and Carolina hemlock (Tsuga caroliniana)
trees across thousands of acres over the last several decades, and
continues to slowly creep westward from the eastern seaboard. Though
the Allegheny National Forest is not yet infested, the hemlock wooly
adelgid has been confirmed in Elk County on more than one occasion in
recent years.
Prior to European settlement, a vast old-growth forest dominated primarily by eastern hemlock and American beech (Fagus grandifolia)
trees cloaked virtually the entire Allegheny Plateau -- on which
today's Allegheny National Forest is located. The frequency and
abundance of hemlock was drastically reduced across the region by the
tannery industry here in the late 1800s and early 1900s due to
widespread clearcut logging.
Though the hemlock has made a tremendous comeback in the decades since
the massive clearcutting, the hemlock wooly adelgid now threatens to
eventually all but eliminate the hemlock from northwest Pennsylvania's
landscape.
related info:
Hemlocks dying in North Carolina
Pennsylvania DCNR Hemlock Wooly Adelgid site
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