Five prominent species of ash tree in the eastern US have been driven to the brink of extinction from years of lethal attack by a beetle, a scientific group says. Tens of millions of trees in the US and Canada have already succumbed, and the toll may eventually reach more than 8 billion, the International Union for Conservation of Nature said Thursday. Ash trees are a major part of eastern forests and urban streets, providing yellow and purplish leaves to the bounty of fall colors. Their timber is used for making furniture and sports equipment like baseball bats and hockey sticks. The rampage of the emerald ash borer is traced to the late 1990s, when it arrived from Asia in wood used in shipping pallets that showed up in Michigan, per the AP.
Asian trees have evolved defenses against the insect, but the new North American home presented it with vulnerable trees and no natural predators. "The populations are exploding," says Murphy Westwood of the Morton Arboretum in Lisle, Ill. Infestations have been detected in 30 states. "It's a very efficient killer," Westwood says. "As the ash borer moves through a forest, it will completely kill all of the mature ash trees within three or four years." The five species on the brink are the green, black, white, pumpkin, and blue ash. A sixth species, the Carolina ash, was put in the less serious category of "endangered" because it might find some refuge from the infestation in the southern part of its range, which includes Florida, Texas, and Cuba. (The feds tried unleashing wasps to kill the emerald ash borer.)