Scientists baffled by sudden decline of aspen in Rockies

There is something doleful about the whispering of the white-barked aspen trees that carpet the slopes of the Rocky Mountains. It is a sound of sickness and death.

Scientists believe that up and down the mountain chain, the aspen trees are beginning to vanish. As many as 10 per cent have died or are ailing in parts of Arizona, Colorado and Utah, according to the surveys. In parts of Alberta, Canada, about 30 per cent of the trees have died in five years.

The greatest problem for the 100 scientists at a conference in Utah last week is that they are not sure what is afflicting the trees."As soon as we understand what's going on, then maybe we can do something about it," said Dale Bartos, a US Forest Service ecologist based in Utah. Tom Wardle, a forester from Colorado, said: "We will, I'm very confident, figure it out."

Researchers are focusing on the unusual reproductive system of the aspen. Instead of distributing seeds, the trees sit upon hugely complex root systems. As older trees die, the roots send up shoots which become saplings.

The greatest worry is that in areas where the trees are in trouble, the shoots are not appearing either. "If we're losing roots," warned Wayne Shepperd, of the US Forest Service, "that's going to change the amount of aspens on the landscape."

One possibility could be the presence of a previously undetected fungus. Recent periods of drought in the American West could be to blame, as well as the eating of shoots by herds of elk as well as human interference with the normal cycles of forest fires. Scientists are also wondering if caterpillars are responsible.