The beetle is a native species and infestations are an ancient part of the forest ecosystem—trees and thousands of species of the beetles have coexisted for thousands of years. But several of the current outbreaks are the biggest in recorded history.
Scientists believe the beetles are getting a boost from consecutive warm years that supercharge reproductive cycles and allow many more of the insects to survive frigid winters. Drought conditions also stress and weaken trees, making them far more susceptible to threats, including attacks by the voracious beetles, which are no bigger than a grain of rice.
Forest management plays a role as well. By protecting forests from natural fire cycles, humans have greatly increased the relative composition of older pine trees in which the beetles prefer to feast.
3 August 2012