Aspens are dying mysteriously in the Western U.S.

Aspens, the most widely distributed trees in North America, are rapidly dying in some Western states — and no one knows why. The culprit may be insects, or climatic stress, or overgrazing. Or all of those. Or none of them. It may be a lack of recent avalanches and fires, because aspens thrive in the aftermath of disaster. Or the aspen die-off may have been triggered by a recurrent drought that started in 1996. “There’s no real pattern,” says U.S. Forest Service researcher Wayne Shepperd. Younger groves of aspen seem to be healthier than mature groves, but it remains to be seen whether they will sprout. “Quite honestly, we just don’t have any answers,” says Shepperd. Whatever the cause, USFS aspen ecologist Dale Bartos predicts that 10 percent of aspens in the West could die within several years if the trend continues — and some of his colleagues think that may be a conservative estimate.