Restoring our Ecosystems - The American Chestnut

Biodiversity - By Dr. Reese Halter

A century ago the most dominant tree in the U.S. – the American chestnut towered the land and ruled the East Coast forests from Georgia to Maine. In a manner of a human lifespan this majestic tree has not only disappeared; it has in many cases been forgotten.

Chestnuts belong to the genus Castanea and are a member of the beech family, which flourishes in the temperate zones across the northern hemisphere.

Once upon a time chestnuts grew all over North America and Eurasia then joined to a supercontinent called Laurasia. Once Laurasia broke-up seven species of chestnuts developed: Chinese, European, Japanese, dwarf Chinese, Chinese chinquapin, American chestnut and Allengheny chinquapin.

All species bear nuts – high in fiber, protein, vitamin C and carbohydrates; low in calories and fat.
All chestnuts have root systems that are able to regenerate new trunks – coppicing is a potent form of resilience against natural disturbances including landslides and flooding.

The native range of tall American chestnuts once span over 100 million hectares across the East, west to Ohio, Kentucky and Tennessee. In fact, there are 1,094 places with chestnut in their names across the U.S.

The American chestnut’s fruit – its nuts are the sweetest of all the species and produced prodigiously, annually. A single tree could easily produce 6,000 nuts. Those nuts fed bears, elk, squirrels, deer, raccoons, mice, wild turkeys – perhaps as many as 10 million, and supported enormous flocks of passenger pigeons.

Native Americans relished the chestnuts using them for food as well as medicine.

Families in the 18th and 19th century that lived in the Southern Appalachians depended heavily upon the chestnut crop for food and used it as a resource to trade for all other necessities.

The wood was even-grained, sandy colored and strong. By 1909, 600 million board feet of chestnut was cut annually. And by 1915, two-thirds of the tannic acid produced in the U.S. came from chestnut wood and bark.

In the summer of 1904 the stately chestnuts at the New York Zoological Park began mysteriously to die.

The trees exhibited peppering of sun-colored spots, sunken patches of bark high over-head, handfuls of pale or withered leaves and lots of dying branches.

By the spring of 1905 every chestnut tree in the New York Zoological Park was infected.

Dr. William Murrill, a mycologist from Cornell University, discovered the life cycle of the fungus Cryphonectria parasitica or the chestnut blight. The fungus encircles the limbs or trunk and girdles or cuts-off the food and water supply – within two or three years it kills a mature tree.

The blight likely came from a Japanese chestnut imported in the late 19th century carrying the fungus that both Japanese and Chinese chestnuts were immune to, yet lethal for the American chestnut.

The U.S. did not have a national quarantine system until 1912.

By 1911, Pennsylvania had mounted an all out campaign to eradicate the blight but it was futile as the spores spread far and wide with even the slightest breeze.

In 1915 another imported destructive fungus Phytophethora cinnamomi attacked the roots of the American chestnuts.

By 1925 the chestnut blight had advanced deep into North Carolina – moving at a lightning speed for a fungus of 42 miles a year.

At the height of the pandemic the U.S. Forest Service urged lumberman and landowners to cut all chestnut trees – dead or alive. How many resilient American chestnut trees to the chestnut blight there may have been – is anyone’s guess.

By 1943 some four billion American chestnut trees were dead; that is enough trees’ to cover Yellowstone National Park one thousand eight hundred times over.

Today there are about 300 known resilient mature American chestnut trees as the species teeters on the edge of extinction.

Since the 1920s scientists have been attempting to breed Chinese and American chestnuts utilizing the Chinese genetic resistance to the fungus. Other scientists are trying to develop a strain of fungus that attacks itself but not the tree. A third strategy is using biotechnology to recombine the American chestnut genetics to provide resistance against the blight.

Should these intrepid tree scientists succeed – reintroducing a species back into the wild is not without its challenges or risks. Much of the basic ecology of the American chestnut is unrecorded and how it will cope with wildfire is speculative.

Yet in an era where humans are destroying 50,000 species a year or one every 10 minutes, re-establishing the American chestnut offers hope in making a difference and the opportunity to restore a magnificent ecosystem.