Pine Beetles Devastate the Mountain West

Since buying our land a decade ago and building an off-grid cabin, we have encountered much that could cause worry. Mountain lions roam the woods. Bears come steal our bird seed. We’ve had a small fire started by lightning on our property, and watched a fire burn 150+ homes within 2 miles, just beyond the next ridge. Yet, there is a creeping disaster coming upon us, a silent one. An epidemic of Mountain Pine Beetles is devastating the forests of the Western U.S. and Canada.

Like a slowly unfolding train wreck, this epidemic has descended from the north and west. We first became aware of the problem about five years ago when the pine trees started dying across the divide in Rocky Mountain National Park and the Summit County ski areas. Anyone who has gone skiing in the high country has seen the creeping red, brown and gray trees as they die over a season from the beetles. Here is a shot of majestic Long's Peak, the highest peak in the park. Below the ridge, you can see the discoloration in the forests from the dying trees.


When I zoom in on the ridge above, you can clearly see the damage.


Here’s how the Forest Service describes it in a publication called Mountain Pine Beetle on the Colorado Front Range:

Mountain Pine Beetle (MPB) damage across the Western United States is more obvious every season. As trees die, entire landscapes turn red, brown, and then gray. On the Colorado Front Range, the beetle epidemic is intensifying.

Pine forests have experienced severe drought and relatively warm temperatures in both summer and winter during the past decade, resulting in stressed trees and the perfect conditions for an MPB outbreak. The beetles prefer large trees with thick bark, and they have had an abundant food supply in mature lodgepole, ponderosa and limber pine forests.

Beetle population outbreaks are cyclical, and don’t last forever. They end when beetles run out of mature trees, or the larvae die during a prolonged and unusually cold winter.

While we have seen beetle outbreaks in the past, this one is the convergence of a perfect storm. Here, you can see a majestic ponderosa has succumbed. In the next year, those live trees around it will probably die.


For 100 years, the Forest Service lived by a motto of putting out every wildfire. In the last couple of decades, the absence of fire from the forest ecosystem has resulted in crowded, unhealthy forests. Fire used to clear out stands and start the regeneration of the forest, with plants getting plenty of water, sun and nutrients. Scientists now realize how wrong-headed that policy was. Look closely and you can see the gray and red trees along the ridges and valleys.


Even last summer, the epidemic was not this noticeable in the eastern side of the park. Here is a view of Moraine Park that shows the creeping devastation.


Here a closeup shows the damage more readily.


Lodgepole pines are particularly susceptible. Lodgepoles grow in very dense stands and have adapted to fire. Being so close together, the trees tend to go out in a blaze of glory when fire hits. It’s called a stand-clearing event. They have cones that lay dormant on the forest floor, and open when the temperature reaches 800 degrees during a fire. “Lodgepole wants fire,” a Forest Service expert told me. Our mountain is covered with lodgepoles that are all about a hundred years old, grown up since the mountain last burned over.

These unhealthy forests are a boon to the beetles. Healthy trees can produce enough sap to “pitch” the beetles out, but that requires a lot of moisture in the trees. With the drought and overcrowding, the trees are already stressed, and not healthy enough to survive. To kill the beetle larvae requires about two weeks of minus zero temperatures. While we hit 25 below once this winter, the total below zero days at our cabin were about four or five. So the combination of warmer temperatures and drought bring this cataclysm much closer. Half the trees on this slope appear to be infested and dying or dead.


This slope is a little less damaged. Just wait another year.


We were up in British Columbia visiting Vancouver and the Canadian Rockies last spring. I saw great evidence of the epidemic up there. I read estimates that within a couple of years, 90% of the pine forests will be dead in the province. Closer to home, Rocky Mountain National Park west of the Continental Divide has lost 80% of its pines. Take a look here for a series of maps showing the spread of the beetle in this area since 1996. The effect is staggering.

We have been part of a fire mitigation effort in our part of the National Forest for the last five years. We have been thinning our forests and taking out diseased trees each year to improve the health of the forest on our land. I spoke with one of the local Foresters this winter. He says their estimates are that the mountain behind our cabin is 40% infested and that we will lose the great majority of the pines on the eastern side of the Continental Divide in the next several years. While there is some evidence that thinning will save ponderosas, the lodgepole don’t seem to survive despite the thinning. Only trees under 6” in diameter seem to survive.

It’s a geometric curve. Larvae from one infected tree will infest as many as eight trees the next year. Each of those will infest that many a year later. At these rates, the climax comes quickly, with whole forests decimated in less than five years. Here is a hot spot with infected trees in the National Forest adjacent to our property. We cut out two hot spots in our own ponderosa stand when we thinned last fall for fire mitigation.


It is hard to believe how much will change. Trees are taken out of campground to mitigate the danger of people being killed by falling trees. For the first three years after a tree dies, as the needles fall off, the fire danger goes up significantly. As the trees fall, they create an almost impenetrable forest with logs strewn throughout, making trails impassable. The very nature of the ecosystem will change for decades if not longer.

For years, we thought our biggest challenge was a devastating fire destroying the views for miles around. That danger remains, even increases. We have had two fires within ten miles of the cabin in the last six months. But, the bigger challenge is the silent killer that is sweeping in from all sides, decimating the majestic ponderosas and the dense lodgepole stands.

In our infinite wisdom, man has altered the ecosystem by removing the important element of fire, which we now know keeps the forest lands healthy. The warming impacts of our ways of living are still dismissed by multitudes. I, myself, could not believe how a couple of degrees could make much difference. Then, I saw how a couple of degrees is enough to push a dry climate into drought. We experienced drought the first two years at the cabin, and the next thing I knew we were seeing fires burn 100,000+ acres in Colorado. Now, here come the beetles.

My grading contractor told me something when he was working on our road a decade ago that stuck with me. “We haven’t seen a good winter in a long time, but in a good winter, you’d have seven feet of snow in this road.” I was stunned to hear him say that. In 2003, we had a blizzard, and indeed got five feet of snow in three days. But, that storm was an outlier. It has been years since the winter got cold enough for long enough to kill the beetles. That is the best possible outcome, but I’m not holding my breath. Say a prayer for a cold winter to save the forests. God’s intervention is about the only intervention that will work at this point.

Last summer, we went camping in the Routt National Forest near the Mt. Zirkel Wilderness and Steamboat Springs. I have some pictures from that area where the beetles came through a couple of years ago. See the article here.