DENVER
03/18/2010 05:12 am ET Updated May 25, 2011

Aspen Trees Dying Off; Scientists Still Don't Have Definitive Reason

DENVER -- This should be the golden season across the West, when aspen paint hillsides in shades of fall.

But a mysterious ailment -- or perhaps a combination of factors -- is killing hundreds of thousands of acres of the trees from Nevada, New Mexico and Arizona through Utah, Colorado, Wyoming and into Canada, according to the U.S. government and independent scientists.

Read more on Wall Street Journal