Beetle kill on the rise in area spruce populations

What happens next depends on many factors

Every year, the U.S. Forest Service and Colorado State Forest Service conduct an aerial survey of Colorado forests to gauge their health. The agencies monitor tree mortality from insects and disease, and they recently released 2014 results. One thing is clear: the bark beetle epidemic is a major player in the condition of the state’s forests. Mountain pine beetle activity has slowed, but spruce beetle activity is on the rise—including 54,000 new acres in the Gunnison National Forest. Understanding exactly what that will mean for local forests is dependent on many factors, including wind and weather. And while infestations have the potential to dramatically change the character of the forest, evidence suggests there might be a cyclical nature to the relationships between the forest and bark beetles.

Survey results
A Forest Service press release issued by public affairs officer Lee Ann Loupe reported that in the Grand Mesa, Uncompahgre, and Gunnison National Forests, spruce beetle mortality has been found on 64,000 more acres of forest than in 2013. Between 1996 and 2014, there have been approximately 224,000 acres of spruce beetle mortality. The Douglas fir beetle has also been a player, and both have been active in the Gunnison National Forest.
Loupe explained the aerial survey allows the Forest Service to track the trends, and a lot of the activity in the Gunnison National Forest has been moving in from other areas. “The Rio Grande area has been most severely affected, and a lot of what is going up to the Gunnison Basin is coming from the south,” she said.
According to figures released from the Gunnison Field Office, the regional forests are part of a statewide trend. Since 1996, the spruce beetle epidemic has increased to almost 1.4 million acres statewide. The spread has been attributed to wind, drought, warmer temperatures and the presence of an older, denser spruce population.

On the ground in the Gunnison Basin
Tom Eager, a Forest Service entomologist based in Gunnison, says understanding the impacts of bark beetles can get complicated fast. But overall, two main sources are contributing to the rise in local beetle activity. On one hand, Loupe’s observation about beetles moving up from the south is spot-on.
“Beetles fly on warm, sunny days, and large numbers are being blown into areas, creating a sudden and dramatic increase in local activity,” Eager explained. These events, known as windthrows, make it possible for a stand of trees to be beetle-free one year and 90 percent dead the next.
“The only way that can happen is importation. The beetles don’t know that over the next hill there are a bunch of yummy trees to eat. It’s a random process,” Eager continued. As an example, he told a story about a gardener in the San Luis Valley near LaGarita who—prior to a storm cell striking—observed beetles fall from the sky and land all over his produce.
The second source of increased beetle activity is irruptive. Beetles already exist in an area as native insects; conditions then become favorable for them, and their numbers increase. The important thing to understand is that both situations are occurring in old forests.
“A lot of people think that when the settlement period occurred, people cut down the big trees and there’s no old growth out there,” Eager explained. In actuality, Forest Service surveys show most of the stands in the central Rocky Mountains are in a mature or over-mature stage of growth.
“So you have stands that are older trees and dense, and when you get a drought year and have elevated numbers of beetles because of windthrow and the inundation going on, the numbers boil up on their own,” Eager continued. That’s exactly what’s being seen in some of the West Elk Mountains on Alpine Plateau and extending eastward to the Grand Mesa. Bark beetles have also made their way to places like Sargent, Monarch Pass, White Pine, and Old Monarch Road.

Where beetles will go next
Understanding what this means—such  as the spruce beetle will spread and what forests will be impacted and how—is not a straightforward process. There’s the random nature of windthrows. Plus, the life cycle of the spruce tree is so long that Forest Service records don’t go back far enough to fully understand the relationship between the tree and bark beetles.
“Every tree species has a different life expectancy, to put it in human terms,” explained Loupe. “Spruce actually have a 300-year life cycle… Having spruce beetles in a stand is not a strange phenomenon. When you go to epidemic proportions and they move in to the extent they are, we see effects, but because of the timeline of spruce and their longevity, we don’t have a lot of record to see if this is a cyclic trend.”
Yet some evidence suggests it is a cycle. Eager says mud samples in high alpine lakes show spruce pollen and beetle parts coexisted 350 to 400 years ago. “We strongly believe this is going through cycles,” he said, suggesting that the spruce beetle may play the role of fire at higher elevations. The insets terminate the life cycle of older stands and clear the way for the next generations.
This can be a hard thing for  a person to grasp, since we have a shorter life cycle. Old timers who know these lands inside and out have never seen bark beetles, so the infestation seems historic. The situation is also complicated by factors such as climate and human impact. Eager explained, whether you factor in climate change or not, the climate is moving from a wet period into a drier period, and that influences the spread of beetles.
So when it comes to understanding what happens next, Eager said, “My smart Alec-y answer is, you tell me what the weather is going to do and I’ll tell you what the beetles will do. Last summer was a wet summer, and if we have two or three or four years in a row like that, I would strongly predict that beetle numbers crash and the circles on the map go away.”
But of course, that is weather-dependent.

Managing the changes
On a forest-wide level, not much can be done to stop the spread of beetles. As Loupe said, “We can’t stop the beetle. We’re not even attempting. It’s not possible.”
What is possible is to try to salvage usable materials and look across the forest for opportunities, “where good can be done, as well as taking advantage of things that are dying, to boost market economy products and maintain jobs,” Loupe explained.
The Forest Service has been doing just that within the Grand Mesa, Uncompahgre and Gunnison National Forests, developing a project to treat areas of spruce beetle epidemic and aspen decline. The SBEADMR—Spruce Beetle Epidemic and Aspen Decline Management Response—project has included high levels of public input. A draft Environmental Impact Statement for the project will be available in late April for public review.
And on the ground, in more localized areas, the Forest Service is partnering with stakeholders to maintain tree cover. One example is Crested Butte Mountain Resort. “We’re working closely with folks up there to do intensive surveys so when [there are signs of beetles], we can get right on top of it,” Eager said. Actions could include peeling the bark, burning the tree, or hauling it to a sawmill.
It’s the areas that are more hands-off, like wilderness and roadless areas, where the beetle will run its course. For more information on the 2014 aerial survey results, go to http://www.fs.usda.gov/main/r2/forest-grasslandhealth.