Distribution in the San Bernardino Forest
The bark beetle outbreak was first observed in the southwestern portions of the forest, near the communities of Crestline, Lake Gregory, and Lake Arrowhead. The beetles have rapidly spread eastward into the communities of Running Springs, Big Bear Lake and beyond. The pines of the southwest regions of the forest have been more heavily harmed by ozone pollution and are therefore more susceptible to bark beetle attack. It is reasonable to speculate that the beetle outbreak started in the southwestern areas of the forest because of the increased stress of pollution in addition to the other stresses present throughout the forest.