Bad news: The decline is likely the result of growing scarcity of the beetle’s favorite food, lodgepole pines.
Since the beginning of the beetle outbreak in 1996, the rice-sized insects have killed trees on about 750 million acres throughout the West. The outbreak apparently peaked in 2009, when four states — Wyoming, Montana, Colorado and Idaho — reported a total of 9 million acres damaged by the infestation.
In 2010 these Rocky Mountain states reported a significant decrease in affected acreage, down to 6.8 million acres. 2011 showed another dramatic reduction, down to 3.8 million acres.
But according to a U.S. Forest Service report, the decline of beetle activity is most likely due to there simply being fewer pines to infest. Even though the insects are taking advantage of warm winters to drill into trees at higher elevations, their numbers seem to be waning for lack of food sources.