Tuesday, February 1, 2011

A Sanctuary in Peril

Extinction is nothing to be bitter about.  It’s been going on since the first life crawled out of the primordial ooze, got outcompeted by the second life that crawled out, and promptly vanished forever.  Death is part of life.  Extinction is part of being a unique species.  The bitterness sets in, for me, when the cause of an extinction (or at least a massive extirpation) is the hands of humanity.  In an unceasing quest to dominate nature, man is destroying it.  Even when the affront to natural balance occurred before the age of ecological enlightenment, I can’t help but harbor a grudge.  Such is my mood these days when looking upon groves of ancient Eastern Hemlocks (Tsuga canadensis).
We returned a day after our rainy hike to take some photos with a dry camera.

It's a rainy afternoon in May.  The central Appalachian highlands can be a popular tourist destination, but this spot is not often crowded and in the rain it’s deserted.  Sarah and I are in Cathedral State Park, one of the jewels of West Virginia’s treasure trove of protected natural areas.  Here more than 130 acres of virgin forest have been protected from the lumberman’s saw.  That may not sound like much, and sadly it isn’t, but it’s the largest virgin tract left in a state that was once nearly completed covered by forest.  (West Virginia started with around 10 million acres of forest.  Today the total uncut acreage is about 260.  It’s called “progress”, I believe.)  In this sanctuary stand dozens of Eastern Hemlocks, centuries-old, up to seven feet in diameter, over a hundred feet tall.  These are behemoths.  No challenge to California’s Sequoias, but impressive for the Appalachians.
Sarah hugs a hemlock.  This tree is likely at least 200 years old.

We walk a couple miles, stopping frequently to admire a giant hemlock here and there.  The forest is alive, bathed in spring rain.  The massive trunks are nearly black, the nurse logs on the floor the tawny brown of sweet decay.  All else is a cacophony of green.  A fine example of what this entire region must have looked like 300 years ago.  And this last remaining gem is safe forever, right?
Not so fast.  Sometime in the 1920’s some nursery stock was imported from East Asia, and along with it came a bug called the hemlock wooly adelgid (Adelges tsugae).   Today this bug (it is a “true bug”, order Hemiptera) is threatening the very existence of eastern hemlock and Carolina hemlock trees.
Hemlock wooly adelgid nymph feeding.  NPS photo.

Hemlock wooly adelgids (HWA) consume the sap from the tender shoots of the trees.  Infested trees typically lose most of their growth shoots, cease to produce new growth, and die within a decade or often much quicker.  In Asia, the hemlocks have evolved in concert with the HWA and show a natural resistance to this predation.  No such luck for the hemlock species of eastern North America.  Thanks to a seemingly harmless importation of ornamental trees decades ago, it seems the giants of Cathedral State Park are doomed.
Dead hemlocks in Great Smokey Mountain National Park.  Photo taken by Will Blozan in July 2007 from the top of a giant hemlock in Caldwell Fork, NC.
Is there no way of stopping HWA?  Not that we know of yet.  There has been some success using a systemic insecticide called Imidacloprid.  This is injected into the soil near the tree or into the vascular tissue of the tree itself, something like a vaccination.  This method is extremely labor-intensive and costly, thus it has so far been used only on trees of “high value and high visibility.”  The best hope now rests with biological controls – always a sketchy proposition.  Recently, a beetle native to British Columbia (Laricobius nigrinus) has been released in the east with the hope that it will establish itself and prey upon HWA.  While HWA exist in the northwest and are present on hemlocks there, there is little mortality.  Some conjecture these beetles are limiting the HWA.  Pseudoscymnus tsugae, a beetle native to Japan has also been released and shows some promise as a HWA predator.
An old growth hemlock forest is more than just standing trees.  This nurse log, protected by the shade of the living giants, is a cradle of diversity.

No one knows what the future holds for Cathedral’s hemlocks.  The best advice would probably be to visit now.  Should we lose the old growth hemlock forests, the vision of those giants standing darkly against a spring cloudburst should be etched in the memory of more than a just a few.
What future for this seedling hemlock?

Hopefully this!

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