Mountain Pine Beetles Chewing into Grand Teton National Park Forests

Mountain pine beetles long have focused on lodgepole pine trees, but warming temperatures have allowed them to survive in higher elevations where whitebark pines reign. In this photo, taken in late-August in the Wind River Range of Wyoming, the reddish tree on the left is a whitebark pine killed by the beetles, while the green tree on the right is Engleman spruce. Kurt Repanshek photo.

There already are splashes of fall color showing up in Grand Teton National Park. But the reds and rusts are not associated with the changing of the seasons. Rather, they're a dire harbinger of what climate change could exact from the park's forests.

The red trees interspersed among Grand Teton's coniferous forests are dead and dying due to infestations of mountain pine beetles. Mountain pine beetles evolved with the West's lodgepole pine forests. Indeed, beetle infestations have been sweeping these forests for just about as long as they've been around.

Once a beetle bores through a tree's outer bark, it sets up shop in the spongy phloem layer where it lays its eggs and eats the phloem; in the process, according to park officials, they cut off the flow of water and nutrients between the tree's roots and its needles.

Evolution provided lodgepole pines with defensive tools -- thick, sticky resin that can smother the bugs and even a chemical odor to ward them off. However, there's a critically important tree higher up in elevation that has no natural defenses and which also is being attacked by the beetles.

In years past whitebark pines, whose nutritious pine nuts are a key staple for Greater Yellowstone Ecosystem grizzlies in the fall, avoided infestations because it was simply too cold where they thrived for the beetles. With the onset of climate change, though, warmer winters are enabling the beetles to go higher in elevation and into the whitebark pines.

Now, it doesn't take a much warmer winter for these pests to survive. Forest entomologists say it typically takes a ten-day cold spell of 40-below-zero weather to kill these beetles. There haven't been many of those cold snaps in recent years, and so the beetles are flourishing. In fact, in some instances the adults are living through the winter only to resume their gnawing and egg laying late the next spring.

Interestingly, the folks at Grand Teton don't seem overly concerned about the beetle outbreak. In a recent release they said the sprinkling of dead trees in their park "stem(s) from a cyclic, natural phenomenon."

"Periodic outbreaks of mountain pine beetles play an important ecological role in the Greater Yellowstone Ecosystem and are central to the life cycle of western forests," the release added.

Now, Grand Teton officials do acknowledge that "warmer air temperatures of recent years have allowed bark beetles numbers to expand into higher elevation ecosystems, as well as to flourish where they have historically occurred." But they stop short of using the term "climate change."

"Periodic increases of this insect, and the subsequent tree mortality, are part of a naturally occurring cycle. In fact, similar beetle infestations occurred throughout the Rocky Mountain West and in Grand Teton National Park during the 1930s and 1960s," the release states. "Biologists and ecologists acknowledge that mountain pine beetle outbreaks help to create a mosaic of forest types and ages, and to maintain nutrient and energy cycling in a natural ecosystem, much like other natural events: fires, avalanches and microburst winds that topple large tracts of trees."

What the release also doesn't detail is the concern that the current beetle outbreak is unlike any other experienced in the Rocky Mountains and that it likely will be catastrophic in terms of the damage done to whitebark pines. Take the whitebark pine out of the ecosystem and you remove a key food that sow grizzlies rely on in the fall when they're bulking up for hibernation.

Scientists who are following the spread of mountain pine beetles in the Greater Yellowstone Ecosystem were somewhat surprised by the park's seeming shrug of the shoulders to the beetles' advances into whitebark pine stands.

Grand Teton's release "is for the most part accurate. However, it really does play down what is happening in whitebark pine substantially -- One wonders if this is intentional or if the park folks really do not know what is happening," says Dr. Diana Six, a forest entomologist at the University of Montana whose specialty is bark beetle ecology. "I assume the former and that this downplaying is being done in order to alleviate concerns of the general public."

Park biologists are using a synthetic pheromone called "verbenone," which can work to drive away mountain pine beetles, to try to protect small numbers of individual whitebark pines. While Dr. Six says verbenone has had limited success in past uses, she adds that that's "really the only tool the park has at this time."

Comments

What is different about this pest and the one destroying the lodge pole pines in the Rockies of Colorado? There we were told the destruction came as a result of the lack of normal thinning that occurs as a result of wildfires and only trees 8" and above were being attacked. It appears the "experts" in each area have different stories all covering the same outbreaks. It's no wonder it's hard to get the backing of people in lobbying those in power to change things.

Anon,

Having been gone for a week, I'm a bit late in responding to your questions. From my understanding, what's going on in Colorado is the same as what's transpiring in Wyoming and Montana. As I've been told, the lack of normal thinning does heighten the likelihood and impact of beetle attacks. Also, trees 8" and above in circumference are preferred by the beetles; apparently smaller trees don't pack the nutritional resources sufficient to maintain an infestation. That's been seen in whitebark pine infestations as well.

Long story short, the experts are in agreement about what's going on.

Are Engleman spruce affected by Mountain Pine Beetle? In Winter Park, Colorado, lodgepole Pines are greatly affected, but I haven't noticed any Engleman spruce affected even though they are surrounded by dead lodgepole. Is there a possibility that the Mountain Pine Beetle will attack Engleman spruce in the future?

I'm afraid there's another beetle that's deadly to Engleman Spruce -- the aptly named Engleman Spruce Beetle. And a little Internet research shows that the "western spruce budworm is another potentially damaging insect that attacks both Engelmann spruce and subalpine fir."