By Will Parson, Chesapeake Bay Program

If you travel from the bottom of Pennsylvania to the top, you’ll see why the state is called “Penn’s Woods.”

Near the heart of Pennsylvania, where tree-covered ridges rise and fall at regular intervals like rumples in a blanket, several state forests are interspersed with valleys claimed by farmland.

Eventually, the farmland gives way entirely to a huge, unbroken mass of trees spanning most of the north-central portion of the state.

You may think that these miles and miles of dense forests are ancient, but things are not as they appear.

Before Europeans arrived, forests covered almost all of Pennsylvania’s 28.7 million acres of land, but by the end of the 1800s, forest cover dropped to just nine million acres.

The state now holds roughly 17 million acres of trees, but the amount of old-growth forest that was spared by the era of clear-cutting is measured in the hundreds-- not thousands-- of acres. [Read more about old-growth forests in PA.]

One such stretch of virgin woods can be found in Alan Seeger Natural Area, part of Rothrock State Forest in remote Huntingdon County.

The area is home to 500-year-old eastern hemlocks as well as white pine, yellow birch and large specimens of other species. A short trail through the area crosses Standing Stone Creek, which is lined by a thick understory of rhododendron.

Parts of what is now Alan Seeger evaded logging even as the harvest of hemlocks peaked around the turn of the century. By the 1930s, harvesting plummeted to a tiny fraction of what it had been.

However, another threat has arisen decades later.

The hemlock woolly adelgid was accidentally introduced from Asia and reached Pennsylvania in the 1960s. The invasive insect stresses trees, making them more likely to be killed by heat and drought.

And because hemlock is a keystone species that shades streams, thereby keeping the water cool, losing hemlocks can lead to sunnier, warmer streams. In turn, those streams can become inhospitable to cool-water species like brook trout.

Parts of Pennsylvania have seen significant defoliation and death of its hemlocks.

Since 1999, Pennsylvania has been fighting the adelgid with biocontrols—predatory species that target a pest—and has been chemically treating high-value hemlocks in state forests and parks since 2004.

Signage at Alan Seeger refers to the adelgid damage visible there, but also points out how a healthy forest can better withstand pests.

The fate of Pennsylvania’s hemlocks isn’t yet sealed but may be tied to climate change.  [Read more here.]

The adelgid can’t survive very cold winters, so Pennsylvania’s northern latitude is working in its favor.   Hemlocks there haven’t been hit as hard by the adelgid as those in warmer, southern states like North Carolina.

And hemlock deaths seem less severe in areas with healthier, more extensive forest cover, where there are fewer stressors that adelgid-inflicted trees could succumb to.

But if Pennsylvania winters become milder, the adelgid may have more of an impact.

For now, at Alan Seeger, you can still walk a short trail and witness trees that first stood tall centuries before the threats they currently face.

[Visit DCNR’s Woolly Adelgid webpage to learn more about the fight for Pennsylvania’s hemlocks.

[PA Chesapeake Bay Plan

[For more information on how Pennsylvania plans to meet its Chesapeake Bay cleanup obligations, visit DEP’s PA’s Phase 3 Watershed Implementation Plan webpage.

[Click Here for a summary of the steps the Plan recommends.

[How Clean Is Your Stream?

[DEP’s Interactive Report Viewer allows you to zoom in on your own stream or watershed to find out how clean your stream is or if it has impaired water quality using the latest information in the draft 2020 Water Quality Report.].

(Reprinted from the Chesapeake Bay Program Blog.)

Related Articles - Hemlocks:

-- Bay Journal: Hope For Hemlocks: New Tactics Found To Fight Deadly Woolly Adelgid Pest

-- DCNR Good Natured Blog: The Fight To Preserve Hemlocks In Pennsylvania

-- Cathedral, A Film About Cook Forest To Benefit Fund For Hemlock Woolly Adelgid Treatment

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[Posted: December 31, 2020]

1/4/2021