Scientists Bringing American Chestnut Tree Back from Near Extinction

Published November 22, 2010

The American chestnut tree, which once numbered 4 billion but almost went extinct in the 1950s because of an invasion of Asian fungus, may be on its way to recovery through scientific advances and new breeding techniques.

The American chestnut tree once covered 25 percent of the hardwood forests in the eastern United States. It was an important part of Appalachian culture and commerce, provided a valuable source of food for wildlife, and contributed to the health and diversity of the forest ecosystem. The tree spanned an area covering more than 200 million acres of woodlands from Maine to Florida and from the Piedmont west to the Ohio Valley.

By 1950, however, blight caused by an Asian fungus had killed all but 50 to 100 trees, and the American chestnut was nearly extinct.

Now, however, researchers with the American Chestnut Foundation, the U.S. Forest Service, and the University of Tennessee are breeding a hybrid American chestnut tree, with 6 percent Chinese chestnut tree stock, which may be able to resist the Asian fungus blight. Already, 25,000 hybrid trees have been planted in Eastern forests, and scientists are monitoring the trees to see how they fare.

Researchers hope to eventually restore the tree throughout the Eastern United States and reforest the strip mines of Appalachia, which constitute millions of acres that overlap the native range of the tree.

Disease Spread Rapidly
Scientists believe the blight that nearly made the American chestnut extinct originated in Asia. The Japanese chestnut tree, which was imported to America around the turn of the 20th century, is most likely responsible.

“The Japanese already had a well-developed nursery industry, and the trees were imported for people’s yards because they were fairly precocious and would grow within a year,” said Fred Hebard, Ph.D., chief scientist for the American Chestnut Foundation.

The first observed instance of the blight was in 1904 at the Bronx Zoo. The disease spread quickly, and by 1950 the tree was nearly extinct, Hebard says.

Durable, Valuable
American chestnut trees were giants among early American forests, growing up to 150 feet tall with a base up to 10 feet in circumference.

Bryan Burhans, president of the American Chestnut Foundation, says there is no substitute for the American chestnut.

“The wood is very valuable to the niche market of building rot-resistant porches, decks, railroad ties, etc. There are telephone poles in New England built in the early part of the last century from chestnut trees that are still standing today,” Burhans said.

Big Economic Effects
According to Meghan Jordan, director of communications for the American Chestnut Federation, the wood is especially desirable for its straightness and durability.

“Wood from the American chestnut is ideal for building the structures that farmers in the region needed, like houses, barns and, sheds. The trees grow tall and straight, and there are no branches for the first 50 feet, so they are easy to work within the saw mills,” Jordan said.

In addition, the nuts were a staple food for livestock and for the Appalachian people. Losing the trees to the blight presented a serious loss to the region, said Jordan

“I don’t know if anyone has tabulated the costs of the economic loss to the Appalachian region, but I do know that the worst of the blight hit during the Great Depression. Not only were families and livestock deprived of the American chestnut as a cash crop and food source, but also they were hit with a terrible economy,” Jordan explained.

Hopes for Crossbreeding
Scientists know the Chinese chestnut has a high level of blight resistance. Through a process of crossbreeding American chestnut trees with Chinese chestnut trees, they hope to create a blight-resistant American chestnut tree with the Chinese tree’s gene for resistance. The American Chestnut Foundation has invested $16 million over 26 years breeding trees to produce an American chestnut that resists the blight.

“We start out with a cross between an American and Chinese chestnut, then breed their offspring with another American chestnut. Each time you do this, you are getting rid of 50 percent of the Chinese genes, and by culling out the bad trees, we now have trees that are 15/16ths [American], with about 94 percent of [their] genes from the American chestnut,” said Burhans.

“We’re going to know in the next four to five years if our efforts have been effective. Long-term, though, the test will be to see if the trees survive and compete out in the wild with other hardwood trees. In the meantime, we’re continually improving the line of trees we’ve produced,” Burhans explained.

Multiple Benefits
One long-term goal is to reforest the areas cleared for strip mining in the Appalachians. These constitute a million or more acres covering roughly the same area as the American chestnut’s natural range. So far, some of the most promising work is being done on land that was strip-mined and now must be restored under federal law.

“As the years go by, there will be more and more American chestnut trees. I think in our lifetime we’ll see an American chestnut forest in the East. We’ve come a long way,” said Robert Mangold, Ph.D., director of forest health production for the U.S. Forest Service.

Kenneth Artz ([email protected]) writes from Texas.