Resurrecting A Forest

Monday, March 25th, 2013

When Europeans arrived in North America, they found forests filled with American chestnut trees:

These mighty plants, which could grow to be 100 feet tall, were the most abundant trees in the forests, making up 25 percent of the standing timber of the eastern United States. In the summer, the peaks of Appalachian mountains appeared to be capped with snow, thanks to the explosion of white chestnut flowers. Chestnut trees anchored the ecosystems of eastern American forests, providing food and shelter to bears, Carolina parakeets, and a vast number of other species. They were also a mainstay of loggers, who could fill an entire train car with boards cut from a single tree.

In 1904, a scientist observed that a chestnut tree at the Bronx Zoo was dying. It turned out to be infected with a fungus that came to be known as chestnut blight. No one is quite sure how it got to the United States, but all the evidence we have indicates it hitch-hiked its way in the 1870s on chestnut trees imported from Japan.

Chestnut blight, while harmless to Asian trees, proved devastating to the American ones. The fungi released a toxic substance called oxalic acid that killed off the tissue, allowing them to feed on it. An infected tree developed cankers on its trunk, and once they spread around the full circumference of a tree, it could no longer carry water and nutrients from its roots to its branches.

Chestnut Blight

Over the course of about eighty years, the chestnut blight spread across almost the entire range of the American chestnut, from Maine to Missippi. It conquered nine million acres and infected three billion trees. A few lone trees still survive unharmed here and there, but no one under the age of sixty has ever seen the forests of the eastern United States as they once were.

In the pantheon of extinction, American chestnuts are poised awkwardly at the door. Chestnut blight doesn’t kill the trees outright; as it spreads down to the roots, it encounters other microbes that outcompete it. As a result, infected trees become stumps. Sometimes they send up a new shoot, but once it reaches a few feet in height, the fungus attacks it again, and the shoot dies back.

Chestnut Backcross Diagram

In the 1980s, a group of scientists embarked on a different approach, one that is now showing signs of success. If they couldn’t stop the blight, they would help the trees defend themselves.

The reason that chestnut blight was able to come to America in the first place was that Asian chestnuts can fight the fungus. They have genes that allow them to hold the cankers in check and scar them over. The trees can continue to grow and produce pollen and seeds. American chestnuts, evolving thousands of miles across the Pacific, never got the opportunity to evolve defenses against the blight. So the American Chestnut Foundation, a non-profit established to save the tree, decided to start breeding the two trees together, to see if they could provide the American chestnuts with Asian defenses.

When the foundation’s scientists interbred the American and Asian trees, the plants mixed together their genes in different combinations in their hybrid seeds.


  1. Odin says:

    I read this other article today about scientists and geneticists goals of resurrecting extinct animals like the Woolly Mammoth, Dodo Birds, and assortments of large birds and such.

    Incredibly interesting stuff. I get excited about this kind of technology, a bright spot in a mostly dark modern age.

  2. etype says:

    No mention of the elms? The great elm blight got under way in the late 1960s. Wiped out most of North America’s elms, and yet no one really cared. Every bit as bad as the chestnut plague. Also, the destruction of the great forests of the West…

    The point to be derived from this is Americans do not like trees, unless of course, there is someone who likes trees, who doesn’t clothe themselves with strips of fabric donated by Oxfam, then they will go out of there way to love trees, make movies about jive-talking trees, legislate tree marriage, have tree lotteries, tree tattoos, tree daycare, etc.

    But the bottom line is Americans are fine with plastic.

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