Warmer Temps Draw Pine Beetles North

Increasing Temps Allow the Insects to Run Rampant on Northern Pine Forests
Trees have evolved natural defense mechanisms—including chemical defenses—to protect themselves against insects. But according to a study in the Proceedings of the National Academy of Sciences, warming temperatures and seasonal fluctuations may be giving insects the upper hand

pine beetle
Whitebark pine forests are suffering the consequences of global warming in the form of pine beetle infestations. Credit: U.S. Geological Survey

A team of scientists from the University of Wisconsin at Madison reported that native mountain pine beetles are expanding their range further north into whitebark pine forests in the northern Rocky Mountains. Trees at these higher elevations have not evolved defenses to stop the pine beetles. Historically, the northern altitudes were too cold for the pine beetle to survive, but warming temperatures have granted them new access. Now outbreaks of pine beetles are capable of killing entire stands of trees.

Typically, the mountain pine beetle’s preferred host is older lodgepole pines, common in lower elevations. The beetles play a key role in promoting the health of a forest, fostering the development of younger stands. Lodgepole pines co-evolved with the beetle, and the pines developed chemical countermeasures designed to be toxic

The whitebark pine forests have no such defenses and are a critical habitat for grizzly bears. They also play an important role in the hydrology of the mountain range by shading snow and regulating the flow of meltwater. Without natural predators at higher elevations, the beetle populations are left to grow unchecked.

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