The American Chestnut and the Evolution of Conservation

An unusual crowd descended on Asheville, North Carolina last month comprised of foresters, concerned citizens, scientists, and conservation professionals.  They were in town for a symposium hosted by The American Chestnut Foundation to discuss their common goal: to restore the once-dominant American chestnut tree to its former glory in the forests of the eastern United States.  Advocates for these trees have arrived at what might just be the long-awaited turning point in their efforts: a promising new strain of trees has been developed for replanting.  But moving forward with planting these new trees is not a simple decision because they are genetically modified organisms (GMOs), containing a new gene that helps them fight a disease called chestnut blight.

 

Conservation as a field was built on the idea of trying to keep nature from changing.  However, the American chestnut is just one example of how species are struggling to keep up in a world dominated by change.  With people transforming landscapes for agriculture, roads, businesses, and homes, introducing species to new places, and changing the global climate, life everywhere is caught in a race just to keep up.  In this changing environment, keeping things the same as they used to be is simply no longer an option.  Instead, to be successful in conservation going forward, people are going to have to come to terms with the fact that species and ecosystems will only persist if they can adapt.   The story of the American chestnut is emblematic of this shift, and it’s the subject of a major decision looming in conservation that will have ramifications for decades to come.

 

The American chestnut once reigned as one of the most abundant trees across a broad stretch of Eastern forests, especially throughout Appalachia.  It was valued for its timber, edible nuts, and the food and habitat it created for many woodland creatures, like bears, deer, and wild turkeys.  But this all came to an end with the introduction of a new fungal disease, called chestnut blight.  Between 1904, when the disease was first detected in New York, and the 1950’s, nearly every American chestnut tree was killed.  Since then, the trees have been largely absent from eastern forests.

 

The chestnut blight originated in Asia, where it fed on different species of chestnut, which are distant cousins of the American trees.  Over eons, the fungus fine-tuned its attack strategies on the Asian chestnut species, which responded in turn by increasing their defenses.  Today, Asian trees can fight the blight to a stalemate by using a complex suite of genetic tools.  The American trees, with no history of living with the blight, were wholly unable to mount a significant defense against such a novel foe.

 

For more than a century, chestnut lovers have been trying to find a solution to bring the trees back.  At first, they tried to stop the spread of the blight by cutting down infected branches and trees, but this was futile as fungal spores could disperse long distances in the wind, infecting new trees.  Then they looked for the few surviving trees, hoping they might have some natural immunity that could be the basis for developing the next generation of resistant trees.  Unfortunately, the levels of disease resistance in these trees just weren’t high enough.  Others tried to find a way to tap into the disease resistance of Asian chestnut species and started making new hybrids that crossed Asian and American trees.  After a hundred years of breeding these hybrids and selecting the most promising progeny, they managed to create new strains that, while still susceptible to the blight, don’t give up quite as easily.

 

Perhaps the most significant event in helping American chestnut trees fight the blight occurred when scientists from the State University of New York’s College of Environmental Science and Forestry in Syracuse spliced a new gene into the tree’s genome.  The gene in question came from wheat, and it codes for an enzyme that reduces damage from fungal infections.  And it’s not just wheat that makes this enzyme, it also occurs naturally in many plants, like corn, rice, strawberries, and cacao, so there’s a good chance you’ve eaten it today.

 

Armed with their new defensive capability, the genetically modified trees are better at tolerating the blight, often reaching a détente with the disease.  But the teams working to develop blight-resistant trees are not satisfied to stop there, so they are crossing these genetically modified trees with the best hybrids and wild trees to make strains that are even stronger against the blight, while also being better able to tolerate environmental threats, like climate change and other diseases.

 

In trying to bring back their beloved trees, the symposium attendees and their colleagues have ventured into new territory in conservation.  Never before has this kind of genetic modification been used to bring a species back from the brink of extinction.  Not surprisingly, this effort is creating something of a reckoning in conservation circles.  Is this kind of technology, which some people avoid in the food they eat, acceptable when a species’ fate is on the line?  In some cases, it’s pitting groups against each other, especially those who oppose GMOs versus those who see them as just another tool in the conservation toolkit.

 

American chestnuts are just the tip of the iceberg for species that are under threat and may benefit from technological advances in tools like selective breeding, hybridization, and genetic engineering.  To find other examples, one needs to look no further than the eastern forests where American chestnuts have already declined.  Ash trees are under threat from the emerald tree borer, Elm trees are dying from Dutch elm disease, and Oak trees are suffering from oak wilt, just to name a few.  In many cases, declines have a similar underlying story: native trees are being attacked by a new suite of pests and pathogens.  To survive, they’re likely to need to develop new capabilities to defend themselves.

 

In 2020, developers of genetically modified chestnut trees applied to the United States Department of Agriculture for permission to freely plant them.  In their proposal they argue that the trees that they’ve grown in controlled environments, and wild plants with the same enzyme, have yet to show any special risks to people or wildlife, indicating that they’re safe to plant more broadly.  An answer is expected soon, perhaps in time to start planting next year if the application is approved.

 

The forthcoming approval decision represents a major milestone in conservation.  If approved, it signals that we have formally arrived at a new era in which genetic engineering is part of our toolkit for saving species that are struggling.   Many proponents of restoring the American chestnuts have already made their peace with this new reality.  For the rest of us, similar questions may be coming soon as we grapple with whether and how to try to save the many species that are at risk of disappearing on our watch.  To save them, we all need to ask: how far are we willing to go?

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Michael Mehta Webster is the author of The Rescue Effect and an expert in ecology, conservation, philanthropy, and non-profit management. His research interests focus on how organisms and ecosystems adapt to environmental change, how this information can be translated into effective conservation strategies, and the practical and ethical dilemmas that arise along the way

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