Eastern U.S. forests once had billions of American chestnut trees but now there are only 4. Chestnut trees nourished ecosystems, built homes, and sustained Appalachian communities. In the early 1900s, a foreign fungus arrived, and within decades, nearly all of the American chestnut trees were gone. Researchers are working to develop American chestnut trees that survive and thrive in the native range they formerly dominated but the chestnut’s comeback will take time. Be sure to watch One Massive Tree if you enjoyed this nature video.