The Mountain Pine Beetle, a particularly nasty pest of lodgepole pines, is devastating forests throughout the west. Why? Well, buried in this article: Bark Beetles Kill Millions of Acres of Trees in West is a tiny little mention of ONE of the many causes: milder winters.

Scientists have said that the beetles are only destroyed by winter temperatures of 30 to 40 degrees below zero (Celsius)–and it hasn’t been that cold in the winter for many years in most of the west.