An invasive fungus wiped out 4 billion American trees in 1904. Can scientists bring them back in 2026? Find out here

In 1904, something alarming was discovered at the Bronx Zoological Park in New York City. It was a deadly fungus, Cryphonectria parasitica, that was killing American chestnut trees.

The result was one of the most devastating ecological disasters in the history of U.S. forestry.

An Asian Invader

The fungus Cryphonectria parasitica was brought to North America from Asia, probably in imported chestnut trees. By 1950, the American chestnut's entire range was infected with chestnut blight.

It's hard to imagine the scale. At one point in time, American chestnut made up an estimated 25 percent of eastern forests, encompassing some 200 million acres. Within decades, a tree that had helped define those forests was almost gone.

Chestnut was a valuable source of food and habitat, and its wood was prized for its durability and rot resistance. The disappearance of the species changed forest composition, nutrient cycling and food for wildlife. A 2026 assessment by the U.S. Forest Service determined the American chestnut, once among the dominant trees in the southern Appalachians along with oaks, is “no longer functionally present.”

But in 2026, the century-old tale took a remarkable turn.

On August 27, the USDA deregulated Darling 54, an American chestnut developed by scientists at the SUNY College of Environmental Science and Forestry that was genetically engineered to improve its tolerance to chestnut blight. The USDA determined that the genetically engineered tree would pose no greater plant-pest risk than the non-modified tree.

Can Scientists Bring It Back?

The goal is an ambitious one: to put American chestnut back in the forests where it once flourished.

The scientists aren’t just trying to save individual trees. The long-term restoration program is designed to establish populations that can survive, reproduce, and ultimately reclaim some of the ecological role lost by the species more than a century ago.

But coming back will not be easy.

Other threats that the researchers face include root rot, deer browsing, competition and changing forest conditions. The U.S. Forest Service said aggressive restoration efforts may be needed to bring chestnut back as a major, stable part of eastern forests.

From Catastrophe to Comeback

Thus, the story of the American chestnut has come full circle.

A foreign fungus arrived in New York and destroyed billions of American trees. More than 120 years later, scientists are using some of the most sophisticated tools of modern genetics to try to reassemble the tree.