GE American Chestnut — Restoration of a Beloved Species or Trojan Horse for Tree Biotechnology?

Biotech industry hopes that getting genetically engineered chestnut approved for conservation planting will soften public opposition to transgenic trees.

About a century ago the American chestnut tree was attacked by the introduced fungal pathogen (Cryphonectria parasitica). This fungus drove the chestnut to functional extinction. Now, scientists at the State University of New York College of Environmental Science and Forestry (SUNY ESF) claim to have created, through biotechnology, a resistant American chestnut variety. They aim to petition the required regulatory agencies (USDA, FDA, EPA) for deregulation of their genetically engineered chestnut in the near future, with the stated goal of “restoring” the species to nature. 

photo of American chestnut leaves in fall
American chestnuts were once among the most common forest trees in eastern North America. A blight early in the twentieth century eliminated most of the trees. However, the root systems continue to produce new growth. The young trees usually succumb to the blight before reaching maturity. Photo by Nicholas A. Tonelli.

If it is deregulated, the GE chestnut would be the first GE forest tree species to be planted out in forests with the deliberate intention of spreading freely. Monitoring or reversing their spread, once released, would likely be impossible. Performing valid risk assessments of the potential impacts of GE American chestnut on forests, wildlife, water, soils, pollinators or people, is hampered by our lack of knowledge about both the ecology of the American chestnut and forest ecosystems. Furthermore, since American chestnuts can live for more than 200 years, risk factors may change over the tree’s lifetime in unpredictable ways.

Critically, the choices we make about the GE American chestnut will set a precedent for the future use of biotechnology on other forest tree species and even more broadly, on the use of biotechnology, including new technologies such as gene editing, gene drives etc. as “tools for conservation.”

It is therefore critical that we carefully evaluate the case of the GE American chestnut. Towards that end, we recently published “Biotechnology for Forest Health? The Test Case of the Genetically Engineered American Chestnut.”

That paper was inspired by previous experience with a 2018 National Academy of Sciences study group on “The Potential of Biotechnology to Address Forest Health.”  The case for using genetically engineered American chestnut for species restoration featured within the NAS study group.  Similarly, it has also been featured in other contexts where the potential for using biotechnology in conservation has been evaluated.  For example, it is presented as a “case study” in the International Union for Conservation of Nature 2019 report “Genetic Frontiers for Conservation: An assessment of synthetic biology and biodiversity conservation”. We therefore felt compelled to clearly articulate and share our reasons for opposing the GE American chestnut.

An American-Chinese Chestnut hybrid. An American-Chinese Chestnut hybrid. The American Chestnut Foundation has worked to implement a breeding program that would hybridize American chestnut with the naturally blight resistant Asian chestnut, and then backcross to produce a blight resistance tree that nonetheless preserved the growth characteristics of the American chestnut.Photo by Photolangelle.org

The American chestnut is a much beloved, iconic, “perfect tree” — that once was a dominant species along the eastern USA and into Canada. Prolific nuts reliably provided nutritious and delicious food, and fodder for livestock. The wood, rot resistant, easy to work with and pleasing to the eye was prized by the timber industry. Cryphonectria, “the blight” was a catastrophe — for the forests and wildlife, and for the human economies, especially those of rural Appalachia, where the seasonal nut harvest was key source of income, and sustenance. Restoring the American chestnut is a long-held dream for some people, even as our collective memory of chestnut-filled forests grows dim with the passage of time. 

The American Chestnut Foundation has worked to implement a breeding program that would hybridize American chestnut with the naturally blight resistant Asian chestnut, and then backcross to produce a blight resistance tree that nonetheless preserved the growth characteristics of the American chestnut. Hundreds of thousands of hours of painstaking work across many years has gone into this breeding program — a long process that has slowly progressed, albeit with some setbacks along the way. 

The SUNY ESF scientists claim that genetic engineering will provide a faster solution. After experimenting with various genes and combinations of genes, they have settled on using a gene sequence derived from wheat that causes the tree to produce an enzyme, oxalate oxidase, (aka OxO).  This enzyme inhibits the spread of the fungus once established, making it less lethal to the tree.  OxO is not uncommon in nature, and has been experimented with in a variety of common crops. In their promotional materials, the scientists are careful to highlight that OxO is common, and that the gene comes from ordinary wheat — conjuring images of saving the chestnut with nothing more dangerous than a tasty slice of buttered toast.

But will the OxO trait really enable restoration of the species?  This is highly unlikely. First of all, engineering resistance to fungal pathogens in general has proven extremely challenging.  Biotechnologists have long struggled to do so with familiar common crops with which, unlike forest tree species, we have plenty of prior experience. In spite of many, many efforts, only a single fungal pathogen resistant crop is commercially available (the Simplot potato, resistant to late blight). The problem is that fungi are very good at finding new ways to evade plant defenses. There is a virtual arms race going on between plants, evolving new defenses, and fungal pathogens, evolving new ways around those defenses. Hence making durable effective resistance is extremely difficult. As well, when plants invest in defending against a pathogen, their growth is often stunted or otherwise compromised and they can become more susceptible to other pathogens or stresses they encounter.

SUNY ESF’s OxO engineered chestnut trees appear to be resistant to the blight — but only young trees in controlled lab and field trial conditions have been tested. The oldest trees tested to date are only about 15 years old — other more recently developed lines are even younger. Yet chestnuts can live for over two hundred years during which time they may experience many diverse conditions — weather extremes, insects and pathogens etc. that could affect the expression of the OxO trait, or other characteristics of the trees. We cannot reasonably assume long term durable blight resistance in natural forests based on extrapolation from results on very young trees under controlled and laboratory conditions. 

photo of American chestnut bight
Results of the American Chestnut blight documented on the Chattahoochee National Forest in north Georgia in 1930. Photo courtesy of Chattahoochee National Forest.

Even the SUNY scientist most involved with developing the OxO engineered chestnuts, William Powell, openly acknowledges that long term stable resistance to Cryphonectria, based on the OxO trait alone, is unlikely to succeed.  He states:  “Eventually we hope to fortify American chestnuts with many different genes that confer resistance in distinct ways. Then, even if the fungus evolves new weapons against one of the engineered defenses, the trees will not be helpless.”

Another pathogen, Phytophthora cinnamomi, (aka root rot or ink disease) had been killing off American chestnuts in the southern part of their range even before Cryphonectria arrived. That pathogen is meanwhile spreading northwards under a warming climate. Scientists agree that restoration of the chestnut would require stacking of multiple traits including for resistance to Phytophthora. The OxO trait alone will not restore American chestnuts.  

So why claim otherwise? Why rush the GE chestnut into regulatory review when even its own creators recognize it cannot fulfill the goal of species restoration?  Because the OxO engineered chestnut — using “nothing but a wheat gene” to “restore a beloved iconic species” is being used as a public relations tool for winning over public opinion toward GE trees more generally, and for the use of biotechnology as a “tool of conservation.” This is a strategy that biotechnology industry proponents expect will soften public opposition and open up the potential for commercializing a wide array of GE trees.

The GE American chestnut is in fact very explicitly referred to in terms of its’ value for public relations, and as a “test case”.  For example, Maud Hinchee, former chief technology officer at tree biotechnology company, ArborGen, and formerly from Monsanto, states: “We like to support projects that we think might not have commercial value but have huge value to society, like rescuing the chestnut. It allows the public to see the use of the technology and understand the benefits and risks in something they care about. Chestnuts are a noble cause.”

Scott Wallinger of paper company MeadWestvaco (now Westrock) stated back in 2005: “This pathway [promoting the GE chestnut as forest restoration] can begin to provide the public with a much more personal sense of the value of forest biotechnology and receptivity to other aspects of genetic engineering."

The Forest Health Initiative which funds the SUNY ESF GE chestnut project states their aim is to “advance the country’s understanding and the role of biotechnology to address some of today’s most pressing forest health challenges. The initiative will initially focus on a “test species” and an icon of eastern US forests–the American chestnut.” And even the American Chestnut Foundation states: “If SUNY ESF is successful in obtaining regulatory approval for its transgenic blight resistant American chestnut trees, then that would pave the way for broader use of transgenic trees in the landscape.”

What “broader use of transgenic trees” can we foresee? A review of the literature on forest biotechnology reveals that most tree biotechnology research is focused not on addressing “forest health” for the public good, but on ways to engineer trees for commercial and industrial processes and profitability. A review of forest biotechnology published in 2018 states: “Genetic engineering of trees to improve productivity, wood quality and resistance to biotic and abiotic stresses has been the primary goal of the forest biotechnology community for decades… Examples include novel methods for lignin modification, solutions for long-standing problems related to pathogen resistance, modifications to flowering onset and fertility and drought and freeze tolerance.”

Most efforts to address “forest health” are focused on species of commercial interest, which are often grown in industrial monoculture plantations, and therefore more vulnerable to a variety of pests, pathogens and health threats.

For example, there has been considerable research focused on engineering resistance to insect pests in commercially important species such as pine, poplar and eucalyptus.

Meanwhile with increasing awareness of the dangers inherent to using fossil fuels, burning wood instead of, or in addition to coal is heavily subsidized (alongside solar panels and wind turbines) as renewable energy, and falsely accounted as “carbon neutral”. Efforts to convert wood into liquid transportation fuels have so far largely failed to attain commercial scale in spite of massive investments. Turning trees into biofuels, bioplastics etc. largely depends not only on genetically engineering specific characteristics into the trees, but also on engineering microbes that produce enzymes needed to break down, access and ferment the sugars in wood.  A 2017 review, titled “Biotechnology for bioenergy dedicated trees: meeting future energy needs” points to eucalyptus, pine, poplar and willow as the species of most commercial interest, with biotechnology research focused on enhanced growth and yield, altered wood properties, side adaptability and stress tolerance, and the alteration of lignin, cellulose and hemicellulose for effective biorefinery conversion to cellulosic biofuels.

In sum, there is much riding on winning over public opinion on GE trees.    

This is why such entities as Duke Energy, ArborGen, and Monsanto, as well as various multinational timber corporations, are among those funding or promoting the GE chestnut. The Forest Health Initiative, which receives funding from some of the above, and in turn has provided large grants to the SUNY ESF research, states: “Biotech trees will find their place in this world, providing fiber, fuel, and even sustainable comfort food (e.g. biotech chestnuts roasting on an open fire). This is an industry to watch as it evolves toward responsible use and takes its place in the pipeline of sustainable biotech products.”  

photo of an American chestnut tree
A young American chestnut tree at the Harkness Preserve in Rockport, Maine. Public opinion has long been solidly opposed to GE trees in general, and remains a significant barrier to their release. Photo by Nicholas A. Tonelli.

Enthusiasm for GE American chestnuts has so far been underwhelming. Recently, board members of the Massachusetts/Rhode Island chapter of the American Chestnut Foundation, Lois Breault-Melican and her husband, Denis M. Melican, who had worked for over 16 years on backcross breeding of resistant American chestnuts, resigned in protest against the organizations’ embrace of SUNY ESF’s GE American chestnut. They stated: “We are unwilling to lift a finger, donate a nickel or spend one minute of our time assisting the development of genetically engineered trees or using the American chestnut to promote biotechnology in forests as any kind of benefit to the environment. The GE American chestnut is draining the idealism and integrity from TACF.”

Indeed, public opinion has long been solidly opposed to GE trees in general, and remains a significant barrier to their release. A number of protests have taken place around the world where GE trees have been tested, including the destruction by women from social movements in Brazil including the MST (landless worker’s movement), of GE tree seedlings belonging to Futuragene in Brazil in 2016. The Campaign to Stop GE Trees was founded in 2014 and has both national and international presence.

When ArborGen sought to field test their GE eucalyptus in the U.S., several organizations filed a legal suit in 2010 challenging the planned field trials. And when the USDA issued a draft Environmental Impact Statement recommending approving deregulation of ArborGen’s GE eucalyptus in 2017, over 284,000 people signed onto or submitted their own comments opposing deregulation of the GE eucalyptus. (To date, no final EIS has been issued by USDA and the petition for deregulation appears to be languishing). Forest certification bodies including Forest Stewardship Council, the Programme for Endorsement of Forest Certification and the Sustainable Forestry Initiative have banned the use of GE trees and their products. The 2008 decision IX/5 (1) of the UN Convention on Biological Diversity Conference of the Parties from 2008 recommended a precautionary approach to GE trees.

GE tree proponents claim that regulatory processes can ensure safety, and complain that they are overly burdensome. But experience with common GE crops demonstrates that standard regulatory reviews, as exemplified by the escape and invasion of GE creeping bentgrass, do not preclude serious harms. In the case of the GE American chestnut, uncontained spread is in fact intentional. Hence there will be no way to prevent contamination of remaining pure American chestnuts, or hybrid chestnut orchards. Nor will it be possible to prevent the spread of GE chestnuts across territorial boundaries.    

The GE American chestnut is meant to launch us down the slippery slope of tree biotechnology. In the wings, and waiting to follow in that newly forged path are a host of other GE forest tree species, engineered for commercial industrial purposes. Natural forests meanwhile are rapidly declining, even as climate science dictates that protecting and restoring forests is a crucial part of regaining carbon balance. Yet logging, even of the precious remaining old growth forests, continues largely unabated, often subsidized with public funding. Replacing real forests with tree plantations, and then referring to them as “planted forests”, conceals the fact that tree plantations are more akin to corn fields than forests.  They often displace natural forests and rural communities, are monocultures lacking biodiversity, doused with herbicides and agrichemicals, rapidly drain fresh water sources, and are designated for fast growth and short rotation mechanical harvesting.

Debates about forest health, and the potential for biotechnology to provide solutions are irrelevant when underlying drivers of forest demise are not addressed. 

If we are seriously concerned about protecting forest health, then reigning in those underlying drivers of forest destruction is the real solution — not genetically engineering trees or replacing diverse natural forests with industrial plantations.     

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