Hope for almost extinct American chestnut tree

January 22, 2016

By: Brantford Expositor

I have always been a fan of poetry – not this modern nonsense that passes for poetry, but the old-fashioned kind with rhyming verses and iambic pentameter.

My contention is, if it doesn’t rhyme, it is not poetry. Of course, like most prejudices, this one is purely personal and it carries no moral authority, save the respect that I have for my own opinion. However, I suspect I am not alone in this regard. I have to confess a certain liking for the masters, such as Keats and the old sheep of the lake district, Wordsworth.

Sometimes poetry can teach us something about our environment that is not obvious because poetry lives for centuries, at least good poetry does. One of these poems is by the American poet, Henry Wadsworth Longfellow who lived from 1807-1882. Some of his most famous poems are Paul Revere’s Ride, The Wreck of the Hesperus, and Christmas Bells which was later the basis for the carol Heard the Bells on Christmas Day. In 1840, Longfellow wrote a tribute to his ancestor Stephen Longfellow, who was a blacksmith. The poem, The Village Blacksmith starts; “Under a spreading chestnut tree, the village smithy stands.”

In the 1800s and earlier, the American chestnut (Castanea Dentata) was a common and majestic tree that was native to the eastern parts of the United States and Canada. These trees can reach up to 30 metres in height and three metres in diameter. This was one of the major trees in our area, but very few examples may be found in the original range of the tree. In Pennsylvania the tree made up as much as 25% of the forest cover in some places.

Today, that tree is hard to find in its natural habitat and then only as small shrub-like trees. Adult versions can only be found in areas that are far outside of the tree’s normal habitat range. The reason, as seems usual in these cases, was the actions of man. It was not bad forestry practices that doomed the American chestnut, but because of sheer carelessness. The cause of the decline of this tree was due to an Asian bark fungus that devastated the forest. From an estimated population of over three billion trees, the number of adult trees in the traditional growth areas is down to less than 100. This fungus was brought to the American continent in a shipment of imported Asiatic chestnut trees. These, and other species of chestnut tree evolved with the parasite and have resistance to it. Not so the American chestnut, whose destruction marched from the original site of the infestation at a rate of about 80 kilometres per year until the tree was almost extinct. Today you will find the tree in some sections of British Columbia where the summers are not conducive to the propagation of the fungus.

Scientists are busy trying to save this majestic tree and are using three techniques. First, there is an attempt to crossbreed the American chestnut with Asian versions that have a resistance to the fungus. This is being met with limited success, but the resulting species are not truly the same as the American tree.

The second way to save the tree is to find versions which have some natural resistance to the fungus and breeding these trees together. While this can work, it may take many years before this breeding program can yield the results hoped for.

The final attempt is to breed transgenic trees that have DNA from a completely unrelated species inserted into their genome to give the tree the needed defence capability. This is the same technique that is used to improve cereal crops that is often referred to as frankenfood in reference to Frankenstein’s monster. In the case of the American chestnut, this involves splicing DNA from the cereal plant, wheat. This allows the tree to produce a chemical called oxalate oxidase that will change the PH environment of the tree to the point where the fungus will be killed and give the tree a built-in mechanism to resist the blight. This technique has the added benefit of preserving the closest version of the original tree’s DNA.

The transgenic trees are awaiting government permission to be released into the wild to repopulate this species of tree. While it may seem unnatural, transgenic manipulation is common in nature where bacteria share genes all the time. Our annual flu shot is made necessary by the mixing of genes in waterfowl, swine and humans, so there are few mysteries in what happens when genes from one species are encoded in another species.

Genetic manipulation has the power to transform our environment if it is done using proper controls. Unfortunately, many people are afraid of what they don’t understand and want it banned. The answer is proper safety protocols and better education for the people. Sadly, it has been my experience that many people who are against innovations such as transgenics are woefully ignorant of the science and are happy to remain so.

Meantime, while blacksmiths have, like the American chestnut, become rare, perhaps there is hope for the tree under which that village smithy stood so many years ago.

Tim Philp has enjoyed science since he was old enough to read. Having worked in technical fields all his life, he shares his love of science with readers weekly. He can be reached by e-mail at: [email protected] or via snail mail c/o The Expositor.

By: Brantford Expositor

Your comments.

Your #1 source for forestry and forest industry news.

Built by Sofa Communications