A Given PLACE

There was a tree – the American Chestnut –  it was called the Redwood of the East. This magnificent canopy tree grew twelve stories high and eight feet around, fast – one hundred feet in 75 to 100 years. It was straight; its wood was hard, and exceedingly practical, resisting rot and warping. In the fall its buttery, sweet nuts fed the forest. Twenty five percent of the Appalachian forest from Maine to Georgia was taken down by a fungus that gets right under the bark and girdles the tree, killing the above-ground portion before reaches an age where it can produce nuts. Within a couple of decades four billion trees were lost, only forest sprouts unable to grow. Chestnut blight was identified in 1904 at the Bronx Zoo, and thought to have been brought in on imported Asian chestnut trees, that co-evolved with the Asian bark fungus; to these trees the fungus is only a minor irritant. That’s all it took to wipe out every one of those trees, though every so often there is a report of a lone tree standing.

A hundred years later there’s a beetle, the emerald ash borer, not from here, and it has marched across forests, fields, parks and yards in North America causing a nearly complete collapse of mature Ash trees.  Billions of dead and dying trees down because of one beetle. And there’s an insect, the wooly adelgid, also not from here, and it is attacking Eastern and Carolina Hemlocks. Tens of millions of these magnificent trees dying.

So trees that came back after clear cutting may be gone soon — the Ash and Hemlock may be going the way of the American Chestnut?

Following successive failed attempts to bring back the American Chestnuts including: hybridizing with other Chestnuts, zapping the trees with gamma radiation hoping for a useful mutation, weakening the fungus by using a virus. NOW, there is progress. The American Chestnut tree, with the help of science, is making its way back; two different approaches are well underway.

In group number one there is the American Chestnut Foundation. Led by Hill Craddock and backed up by citizen scientists spread across the Appalachian forest range, they are using traditional scientific breeding methods with a twist. The twist is a special technique called backcross breading, here’s how it works. First the scientists create successive generations of Asian-American hybrid Chestnut trees. Next, the Asian-American Chestnut trees are cross breed with the American Chestnuts. This decades long process, begun in the 1980s, and has created hybrid, blight free, American Chestnuts with 96 percent American Chestnut genes. But there’s more work to do. At each generation, there is a risk that the genes that are added, might show up with a mutation that isn’t activated until later generations. So, with each generation of tree breeding, a few trees are selected to move forward. The idea is to transfer the blight-resistant characteristics to the American Chestnuts, then phase out the Asian traits. Along the way, there is a need to be able to adapt to geographies, and micro ecosystems in the valleys and on ridges from Maine to Georgia. “If you were a professional gambler,” says Craddock “you’d never bet on the American Chestnut tree.” What are the odds? For every one hundred trees produced over five generations of breeding, only a handful acquire resistance. What’s wrong with just planting Asian Chestnut trees? Well, they aren’t forest trees for one, they are shorter; for another, Asian Chestnuts are not cold hardy so they could not cover the range of the Appalachian forest.   

Still in Tennessee, group number one is making progress. Years ago, Hill and volunteers walked the Tennessee forests to find native American Chestnut sprouts above the old roots to begin the breeding process. Now there is a row fifteen foot tall, fungus resistant, Tennessee bred saplings, planted seven years ago. And other areas along the eastern US are proceeding on this same path.

Group number two is out of the State University of New York, College of Environmental Science and Forestry. Led by Bill Powell and Chuck Maynard, their team includes an army of high school students, undergrads, grad students, post docs, colleagues and citizen scientists. Together, in a process of renewal, they are producing the first genetically modified organism to restore a natural ecosystem.

In graduate school in the ‘80s, Powell became interested in molecular biology. Chestnut blight, it turns out that a common agent, oxalic acid, is what the fungus produces that attacks the American Chestnuts.  Oxalic acid is in many foods, for example, it gives spinach its bitter taste In high doses it is fatal to people. One day, reading through scientific research abstracts, Powell found a paper describing how a gene inserted in a tomato plant produced oxalate oxidase, an enzyme that breaks down oxalic acid. Powell had a EUREKA moment.  Oxalate oxidase, or in short (with a logo fitting for a superhero) OxO could disarm the fungus. The team began testing 30 genes from different plant species that might enhance blight resistance. Genetic modification works. Where Americans get worried about it is in plant crops and food production, where foods are modified to accept chemical fertilizers. This modification is not for the purposes of enhancing economics, in fact, the renewal process for the American Chestnuts is not going to be patented (another first in a GMO process). Instead, the purpose of this process is to put the American Chestnut back into the commons. Scientists eventually found one gene in wheat (not related to the gluten protein) that works. Next, they added a marker gene to receive OxO, the defensive enzyme  also found in wheat, strawberries, barley, oats, bananas, and again, unrelated to gluten.

Then, just two and a half decades later, the team succeeded in getting all the pieces in together. The 40,000 gene American Chestnut tree, renewed through this process is 99.9997 percent American Chestnut. This is the first time genetic modification is being used to restore an ecosystem.

Now researchers are applying for approval from three federal agencies, to test the trees over time in their natural settings, making sure all is good for the whole ecosystem, checking for any impact on other fungi, bumble bees, tadpoles, leaf litter, etc. So far everything looks right. Once approved, the native trees are selected from root and stem systems across the range and particular diverse habitats.

Research like this is happening for ash trees and coral. Future generations will see king trees where there are holes in the forest now. And in the fall the American Chestnuts, with their saw-tooth-edged leaves and their fall crop of sweet, buttery nuts will feed the forest, and the friends of the forest.