Beetle graphic

Beetles no bigger than a grain of rice are destroying conifer forests, and their greatest weapon is invisible.

Six: “Bark beetles are tiny little insects. They kill trees by actually releasing these odors, these pheromones that attract other beetles to the tree, and if they’re lucky enough to attract literally hundreds to thousands, they can overcome the tree’s defenses and then they can raise their young under the bark.”

Entomologist Diana Six of the University of Montana says that in the past, bark beetle populations were generally not large enough to do widespread damage.

But warmer temperatures are allowing more beetles to survive the winter. And, the longer growing season gives insects more time to reproduce, so populations are booming.

Climate change is also causing drier conditions, which is bad news for trees.

Six: “Drought is one of the big drivers of bark beetle outbreaks because it stresses trees, and trees that are stressed have much lower defenses and so they’re not able to fight against the beetle attacks very well.”

Six says that in recent years, the beetles have wiped out tens of millions of acres of forests across western North America.

Reporting credit: ChavoBart Digital Media.
Image graphic: Created by David McCarthy.

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Daisy Simmons

Daisy Simmons is a freelance writer and editor with more than 15 years of experience in research-driven storytelling. In addition to contributing to Yale Climate Connections since early 2016, she also...