The American chestnut was once the dominant hardwood species in Appalachian mountain forests, comprising as much as 40 percent of the overstory trees in the climax forests of the Eastern United States. Foresters used to quip that an enterprising squirrel could travel from Maine to Georgia on the interlocking branches of chestnut trees. The fast-growing American chestnuts often reached five feet in diameter and 60–100 feet in height.
Then came the Asian chestnut blight in the early 20th century that killed over 3 billion American chestnuts basically causing the tree to become functionally extinct throughout its natural range. The blight fungus was probably brought to America on imported nursery stock of Chinese chestnuts. American trees had simply never evolved resistance to this parasite. The American chestnut is now almost entirely gone from the landscape except for a few stumps in the woods that still produce shoots that the blight kills before they reach 15 feet in height.
For more than 30 years, the American Chestnut Foundation (ACF) has been engaged in a privately financed program in which its geneticists have been crossbreeding American chestnuts with blight-resistant Chinese chestnuts. The goal is to produce an American chestnut tree that retains essentially only the blight resistance genes from the Chinese chestnut tree.
More recently, the ACF has been collaborating with researchers at the State University of New York’s College of Environmental Science and Forestry (ESF) to use modern biotechnology to endow American chestnut trees with blight resistance. To that end, the researchers have added a gene from wheat that produces the enzyme oxalate oxidase that breaks down the oxalic acid the fungus uses to attack chestnut trees. It works; the added gene does indeed protect American chestnuts from the blight.
Now the ACF and ESF researchers are officially petitioning the U.S. Department of Agriculture (USDA) to give their blight-resistant American chestnut “nonregulated status” which would allow the blight-tolerant bioengineered trees to be planted without restriction as part of restoration programs.
However, a coterie of anti-biotech activists organized as The Campaign to STOP GE Trees are opposing the petition to the USDA. To justify their opposition to blight-resistant genetically-engineered American chestnuts, the campaigners cite the precautionary principle. But the precautionary principle measures only risks and not benefits of new technologies and amounts to arguing that we should “never do anything for the first time,” as I’ve previously argued. In this case, the activists assert that since researchers do not know absolutely all of the possible consequences of planting blight-resistant American chestnut trees, then none should be planted. Perplexingly, the activists ignore the glaring fact that we do know what the deleterious ecological and economic consequences of having no blight-resistant chestnut trees have been.
In fact, extensive research by the ACF and ESF finds no significant ecological effects from inserting the oxalate oxidase gene, apart from enhancing blight tolerance. The researchers point out that their blight-resistant “chestnuts retain 100 percent of their natural complement of genes; no native genes or alleles have been removed or replaced, and expression of nearby genes is not affected.” In other words, except for the blight-resistant trait, their trees are, in all relevant respects, genetically identical to natural American chestnuts.
In addition, the researchers point out there are no negative human health issues since the oxalate oxidase gene is naturally present in many food crops and is non-allergenic. After all, people have been eating that enzyme in bread for millennia.
In their USDA petition, the researchers observe that if their blight-resistant American chestnuts are granted nonregulated status by the USDA, they will be made available for not-for-profit distribution to the public, and to groups including private, indigenous, state, and federal restoration programs. If the USDA regulators do grant their trees nonregulated status, they can then “be planted like wild-type or traditionally bred chestnuts to accomplish meaningful conservation and restoration of the American chestnut.” Perhaps squirrels could once again travel from Maine to Georgia through the branches of restored chestnut forests by the end of this century.
Disclosures: I have occasionally made small contributions to the ACF in the past and will do so again soon. I have also made a public comment at the USDA in favor of granting nonregulated status to the blight-resistant chestnut trees.