Last month, the media reported extensively on the die-off of aspen trees in the West linked to climate change. Called sudden aspen decline or SAD, the phenomenon is characterized by the death of mature over story with an absence of subsequent regeneration. Open stands at lower elevations, with south to west aspects, are more vulnerable.
The disease is responsible for the die-off of 553,000 acres (17%) of aspen in Colorado alone. Aspen stands in southwestern Colorado, northern Arizona, southern Utah and Wyoming, and southeastern Idaho are primarily affected.
Aspen is the most widely distributed tree species in North America and a vital component of almost every forest ecosystem in western North America. Drought is the principal suspect influencing the die-offs. The lack of water only weakens the trees. Secondary pathogens or insects such as such as canker fungi, wood borers, bark beetles, and clear wing moths actually kill the trees.
The Forest Service is hoping that timber harvesting and prescribed burns will lead to greater regeneration of the aspens. The following photos help document the problem.