American Chestnut: Ghosts of Our Eastern Forests

Menu American Chestnut: Ghosts of Our Eastern Forests

Our woods are haunted. Generations ago, there was a massacre that left few survivors, and our nation has never been the same. The ghosts of the victims still cling to our forests, reminding naturalists and hikers of what was lost. This isn’t fiction. I wish it was. This is the true horror story of the American chestnut and how it was mercilessly eradicated in what many agree is one of the worst ecological disasters to befall forests in the eastern US.

The American chestnut, Castanea dentata, was an incredibly important species, for humans and our eastern deciduous forests. It quickly grew tall and wide, producing large quantities of straight, rot-resistant wood that are still supporting old buildings today. It was also an important food source for wildlife and humans alike – those “chestnuts roasting over an open fire” were holiday traditions provided by the bountiful tree. In the nineteenth century, it was estimated to comprise 25% of hardwoods in its range.

In 1904, an infection on an American chestnut was first noticed at the Bronx Zoo, in New York City. It turned out to be chestnut blight, a fungus by the name Cryphonectria parasitica. By 1906, 98% of the chestnuts in the Bronx were infected, and by 1950 the wind-borne fungus had spread throughout most of the tree’s range. The fungus is thought to have traveled to New York in a chestnut imported from Asia; Japanese and Chinese chestnut (Castanea crenata and mollissima, respectively) are commonly infected but rarely killed by the blight. C. parasitica forms cankers in an American chestnut’s inner bark that eventually girdle the stem. The tree is able to resprout from the stump, but because the blight can linger in nearby oaks (and notably does not harm them), it will infect the chestnut sprout before it can reach sexual maturity, typically before the tree is more than 20 feet tall. The tree is still present in our woods, but is functionally extinct because it is unable to reproduce. American chestnut sprouts, the “ghosts” alluded to earlier, don’t look much like the tall, stately, “sequoias of the east” that dominated our forests before the blight; they are now typically relegated to the understory, where they grow low, scrubby, and multi-stemmed.

The American chestnut was such an abundant and important component of our forests, it’s challenging to determine exactly how much was lost due to the chestnut blight. An estimated four billion individuals were killed, trees that provided immense quantities of excellent lumber and a nearly limitless supply of food to people and livestock. From an ecological standpoint, a major (and perhaps the dominant) species vanished over decades, permanently changing the forested landscape. American chestnut produced a consistent mast (crop of nuts), unlike oaks which have acorn cycles that produce a bounty in some years and next to nothing in others. Due to the dominance of this reliable food source, the loss of American chestnut likely devastated many wildlife populations. Indeed, qualitative reports from the early 1900s describe collapses in squirrel populations, and turkeys, deer, and other nut-eating animals were also likely heavily impacted. At least seven species of moth that relied exclusively on chestnut for larval forage went extinct, and many more invertebrates likely also suffered from the disappearance of such a large food source, including pollinators, which feasted annually on the mid-summer sea of chestnut flowers. Conversely, it is also reported that woodpeckers fared well in the decades following the blight thanks to the new abundance of enormous snags (standing dead wood) in the landscape. Many bat species also likely temporarily benefitted from this flush of high-quality roosts. Those ephemeral benefits to some species are the very few, ephemeral silver linings to the tragic loss of the American chestnut.

If the blight suddenly disappeared and our chestnuts could grow tall again, they would likely never be as prominent. Before 1904 there weren’t many invasive plants in our forests, and deer numbers were famously low, so it was a fantastic time for seedlings to grow. While the chestnut has been a “ghost”, the world has changed. But this hasn’t stopped a dedicated mass of forest enthusiasts who are working to restore the species. Continuing our Halloween theme, learn all about this effort in Resurrecting the American Chestnut.