Pine beetles in our forests:

A history lesson from Diana Six

Diana Six, professor of forest entomology at the University of Montana, has been studying pine beetles for 18 years now, which has given her a unique perspective on these insects.

"There are more than 49 million acres of forest across North America with infestation now, which is 10 times what it's been in the past," she says.  "No outbreak has ever been as bad as this."

Why does she think that the current mountain pine beetle outbreak is so much more severe than usual?

"Unfortunately, more and more the cause is climate change," she says.

The link between climate change and pine beetles

In the past 100 years, average temperatures in Montana have increased by 2-3 degrees Fahrenheit, and that is having a huge effect on the native bark beetle population:

  • "The beetle has expanded its geographic range further north because it's now warm enough for it to survive there," she says.
  • "It's also moved up in elevation" as temperatures have warmed, and is now infecting new host species that it never has historically, like the whitebark pine.
  • "The beetle didn't used to do well up in the high elevations," Diana says, "because again, it was too cold."
  • Beetles also used to only fly and attack trees for two weeks per year; now they fly continuously from May through October, or half the year.

The condition of the trees in our forests is another huge factor in the current outbreak.

Warmer, drier conditions like we have been experiencing in Montana the past 15 years "put a lot of stress on trees, which has the effect of really lowering their defenses and making them easy food for insects," says Diana.

So what's her take-home message?

"We see more and more insects developing these large outbreaks.  If you are thinking about managing an insect or trying to deal with its impacts, it's very important to remember that actually they are responding to something," which in this case is an increase in average temperatures caused by our changing climate.

Sources for the above quotes from Diana Six can be found in the stories and links at right. To learn more about her research, check out these stories in their entirety, or visit her home page at the University of Montana.

Photo at top of Page: Richard Hofstetter