The same thing happened to the American chestnut and various species of Elm. Around 100 years ago, the chestnut was the most common deciduous tree east of the M

The same thing happened to the American chestnut and various species of Elm. Around 100 years ago, the chestnut was the most common deciduous tree east of the Mississippi. The chestnut blight, an accidentally introduced Asian fungus that causes the bark to fall off, effectively wiped the species out in less than 40 years. Only suckers from ancient root stocks remain. As soon as a stem grows thick enough to support a thick bark, the fungus kills it. During the second half of the 20th century, the Elm effectively became extinct in the wild, both in Europe and North America, due to the Elm disease. More recently the Hemlock came under attack from the hemlock woolly adelgid, an accidentally introduced Asian insect. The next generation will not be able to imagine what a mature hemlock looked like.