Wednesday, September 29, 2010

And Eastern Forests Would Never Be the Same

The American Chestnut was once the dominant tree in eastern forests from Mississippi to New York City.  Taller and straighter than its European and Asian relatives--the genus from which it branched after American split off of Europe and started its long collision course with Africa--it provided a sweet nut, too, in reliably sweet droves that had farm and city folk alike marveling at its bounty.  In the early twentieth century entire Appalachian communities like the ones my grandparents grew up in based much of their livelihoods on the wood, bark, and chestnuts.

Then in 1904 in New York City, some chestnuts there looked sick, and started dying.  Tree diseases were no mystery to the forestry of the time, so they sprayed the trees with lime and copper sulfate and waited for recovery.

Recovery did not come.  Within 35 years, the dominant tree of Appalachia was gone; only a few hundred hardy stragglers now remain.  It is estimated that humans watched helplessly while 3 to 4 billion trees died, more than the number of people who existed on earth at that time.

The culprit was a run-of-the-mill fungus, well, run-of-the-mill for chestnut trees in China.  For years scientists feared that a native disease had suddenly gone deadly--and some folktales suggested that the "chestnut blight" was God's punishment for recent sins of mankind.  But the spores were discovered in the living, thriving bark of the Chinese and Japanese chestnut varieties, trees which had been imported to America for their ornamental properties.  The great naturalist Thomas Jefferson even had some growing at Monticello. 

The Chinese and Japanese trees had genetic resistance to the fungus, which had chosen the genus Castenea as its exclusive feeding ground.  American Chestnut, Castenea dentata, now diverged from its Asian cousins by tens of millions of years of isolation, had none, and died in droves at the first assault.  Exotic invasive species to this day wreak havoc on all continents:  Australia has erected a country-spanning rabbit-proof fence to keep at bay the rabbits, imported for a good hunt, that regularly decimate native outback grasses.  Here in the Appalachians, the stiltgrass, mullen, velcro-like burdoch, ornamental bittersweet, and kudzu choke out native plant life and colonize acres of forest for their own.  It is nature being nature, but it is also a potently destructive tipping of the balance-scales that human travel has directly enabled.  And no story has so high a death toll, so grave an alteration of an entire ecosystem, as that of the American Chestnut.

To say that humans watched helpless is not entirely correct.  We watched this icon of the forest fall with dismay, and ardor to act could certainly be mustered.  Unfortunately, it was often misguided, appearing a hubris to the better scientific understanding of our day.  Pennsylvania declared an all out war on the chestnut blight, using a method tried-and-true for diseases which did not spread on the wind by thousands of microscopic spores:  quarantine.  They vowed to cut down every sick chestnut in every square inch of the eastern half of their state, and create a several-hundred mile buffer zone besides in which no chestnut tree would stand to transfer its germs to any western neighbors.  The resulting political battled resembled the way in which scientific subtlety is often trounced for political will today:  the admonishment by leading scientists that such a plan would not work was belied as the dour guesses of men too smart for their own good.  Talking in impossibilities is un-American, they said.  You are only guessing, and one man can guess as well as any other.  But one who has studied something is usually able to form a better guess than one who has not--and although considerable public funding and labor went underway, the quarantine was never finished, and never began to appear successful.  At worst, it may have sealed the fate of the chestnut:  for those few trees that might have possessed better natural resistance, might have made up the naturally-selected hardy survivors of the species, were cut as indiscriminately as the rest.

These days, you can walk a forest dominated by oaks, hickory, and maple, and occasionally see a small sprout on the forest floor.  It reminds one of an oak, with evenly toothed leaves, pointed at each end as white oaks are distinguished from red.  It is a chestnut sapling; does it represent rebirth and renewed hope for the once-majestic species?

American chestnut sapling, located on Hawksbill Moutain trail in Shenandoah National Park.

Alas, it does not, because there are not enough tall trees left to have made this sapling the result of cross pollination.  It is likely a last attempt from a still-living root mass to rise once again, and it will grow to teenage years, and the chestnut blight which has been patiently waiting in dormant phase on the bark of a nearby oak or hickory will gleefully attack once again.  Is there hope that eventually the fungus, deprived by its own fecundity of its food source, will eventually die away, so human-planted chestnuts might tower once again?  There is always hope, but the evidence so far suggests no such thing.  The blight can stay dormant but alive for decades.

There are groups of people who do not want to let the chestnut go.  It was quite a valuable tree, after all:  tall, straight hardwood with an attractive grain, bark full of the tannic acid once used to make leather, and it does grow faster than many other eastern hardwoods.  And the chestnuts themselves, of course.  The American Chestnut Foundation has, for half a century, been crossing American with Chinese chestnuts, hoping according to mendelian genetics to pass Chinese resistance into trees that are otherwise American in characteristics.  If successful they would reintroduce hybrids, 15th/16th American and 1/16th Chinese, into the wild, though now they will have to clear away native oaks to do it.  Even a small corner of the biotech world has jumped to the chestnut's rescue--though I cannot become comfortable with the idea of reintroducing a species which contains man-made genetic material, nor the time and money that must go into trying a variety of genes injected in a variety of places and then waiting a decade to see how the resulting treelet fares.  Probably these trees would become farm trees only, enabling chestnut wood and chestnut fruit to enter the marketplace once again. In truth the dream of returning the mighty chestnut stands to Appalachia will probably not be accomplished by human hands.

Looking at the forest of oak and maple that I only stories inform me are a paltry imitation of the past--I'm not sure we should try.  I grew up in a forest with no chestnut tree, the oaks and yellow poplar are the biggest species I remember.  I do live and work where the chestnut once defined life--but life has moved on now, and what happened is not personal to me.  I am two generations removed.

Yet the other day I was hiking and found a specimen of Castenea dentata large enough to bear fruit.  I saw the strangest spiky green balls on the ground, and I looked up, and there it was:  leaves I was accustomed to viewing with excitement on saplings I nonetheless knew were doomed, adorning a tree of middling height.  It was not a healthy tree, the crown was a spire of dead wood, the leaf-covered branches were short and close to the trunk, which was mottled and peeling.  But it was a tree, not a sprout, and I was mesmerized, confronted with a tiny glimpse of what the forest of my grandparents' time, the forest they tell me of with such reverence, must have been like.

Tree-sized American Chestnut, looking into canopy.  The green balls encase the nut inside; they are quite spiney to the touch.  Toothed leaves grow close to the trunk, one indication that the tree is infected with the chestnut blight.  CCC Dynamite Cabin trail, Shenandoah National Park.

You can't find yourself suddenly face-to-face with a species that is for all intents and purposes nearly extinct, and not feel mesmerized.  Not feel put on trial, not feel compelled to answer the question, how can we do better?  How can we learn from the inadvertent mistakes of the past?  Our understanding of forestry and forest management is much improved from the days of the Pennsylvania quarantine, yet the onslaught of exotic invasive species continues.  The Frasier fir and eastern hemlock both have their devastating bugs from Asia, but treatment has been found for the hemlocks, at least, that can keep a gene pool alive.  The emerald ash borer spreads slowly southward, perhaps there is hope that with education its transfer can be delayed until a suitable control can be found. Biological control in the form of a fungus has done relatively well at halting the gypsy moth's century-long oak ravaging spree.  There is a native fungus that makes the chestnut blight sick, as well--it isn't currently enough to stop the blight, but it might, with time, help tip the balance scales back in favor of a partial chestnut recovery.  There remain challenges, but hope as well.  I am certain that learning from the past is absolutely possible.

Sources:  American Chestnut: The Life, Death, and Rebirth of a Perfect Tree, Susan Freiknel.

The American Chestnut Foundation,

Photos are taken by author, permission to redistribute them but not the text of this blog entry is granted.

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