Some of the best-known North American trees are now rare, and most were lost to introduced pests and diseases.
Endangered trees in America
American ashes
In 2017, the IUCN Red List assessed five of the six most widespread eastern North American ash species as Critically Endangered, with the sixth Endangered. White ash and green ash are among them. The cause is the emerald ash borer, a beetle from Asia that has killed well over a hundred million ash trees.
American chestnut
American chestnut was once among the commonest trees of the eastern forest. Chestnut blight, a fungus accidentally introduced from Asia in the early twentieth century, killed most of the large trees. The roots often survive and send up shoots, which are in turn infected. Breeding and restoration programmes, such as those of the American Chestnut Foundation, aim to bring back blight-resistant trees.
American elm
Dutch elm disease reached North America in the 1930s and killed vast numbers of street and forest elms. Some elms survive, and resistant cultivars have been planted in towns. Young elms still grow in the wild, though many die back before reaching large size.
Eastern hemlock
Hemlock woolly adelgid, a tiny sap-feeding insect from Asia, is killing eastern hemlocks across the Appalachians. Hemlock shades streams and shelters wildlife, so the loss affects whole ecosystems. Biological control and chemical treatments are being used to save the trees.
Whitebark pine
Whitebark pine is a five-needle pine of high mountains in the western United States and Canada. Its seeds feed grizzly bears and Clark's nutcrackers. In 2022, the US Fish and Wildlife Service listed it as threatened under the Endangered Species Act, citing white pine blister rust, mountain pine beetle, altered fire regimes and climate change.
Other rare trees
Florida torreya, a yew relative that grows in a small area of the Florida panhandle and nearby Georgia, has been devastated by disease and is among the rarest trees in North America. Franklin tree, found in Georgia in the 1700s, has not been seen in the wild since the early nineteenth century and survives only in cultivation. Giant sequoia and coast redwood both occupy small areas of California, and both are assessed as Endangered by the IUCN.
What you can do
Plant a mix of species, buy local firewood, report pests and support restoration groups. If you find a tree you think is rare, photograph it and contact a botanical garden or your state natural heritage programme before you do anything else.