Scattered patches of red trees are becoming a more familiar sight in ponderosa pine along Colorado’s Front Range. Scientists, land managers and partners are working to reduce beetle impacts while building more resilient forests.

“The amount of mortality we’re seeing over the last four years has steadily increased,” said Marianne Davenport, forest entomologist with the Forest Service Forest Health Protection in the Rocky Mountain Region.

Adult beetles fly to a pine, bore under the bark and lay eggs. The larvae then feed on the inner tissue that carries water and nutrients. A single tree can host thousands of developing beetles, and when they emerge, they fly to nearby trees. When enough trees in one area are attacked, a few red trees can become a pocket, and pockets can spread along an entire hillside.

This isn’t Colorado’s first outbreak; the last mountain pine beetle epidemic went through lodgepole pine at higher elevations. This time, the beetles are working through areas much closer to where people live.

“It’s in ponderosa pine forest, which more often are found in the lower elevations, which also tend to be where we build our houses,” said Mike Battaglia, research forester with the Forest Service Research and Development.

“When we have forests that are too dense, combined with warmer temperatures and drought conditions, those trees are stressed,” Battaglia said. “When a beetle attacks it, it can’t defend itself.”

Most of the damage happens out of sight. Beetles tunnel beneath the bark, laying eggs while their larvae feed on the tissue that carries water and nutrients through the tree. When enough beetles attack the tree, that damage can kill it.

"It's basically girdling or suffocating the tree," said Katlyn Willard, silviculturist with the Pike-San Isabel National Forests & Cimarron and Comanche National Grasslands. 

A native insect

The mountain pine beetle is not an invasive species. Western forests evolved alongside it, and in normal years the beetle mostly attacks weakened or dying trees. Problems start when dense stands, drought and mild winters tip conditions in the beetle’s favor.

“Mountain pine beetle is a native insect, which I think is very important to know,” Davenport said.

At normal levels, beetles play a role in a healthy forest by killing weakened trees and opening space for new growth. Forest managers focus instead on keeping outbreaks from overwhelming entire areas, especially where crowded, drought-stressed trees can give beetles an advantage.  

“We’re definitely never going to stop it, but to slow it down and to make the forest so it stays as a forest, that’s the goal,” Williard said.

In larger forested areas, that can mean thinning trees to reduce competition for resources, which helps improve forest health.

“If you think about a garden and if you plant too many seeds and you have too many germinates coming up, they are all fighting for the resources,” Battaglia said. “They’re fighting for the light; they’re fighting for the water.”

“What we do know from the science is that if you maintain a landscape that isn’t susceptible, we can do things on the ground that can help lessen the impact of bark beetle outbreaks and drought and reduce how many trees die,” he said.  

On the Colorado Front Range, scientists and managers developed a research-backed framework for promoting healthy forests which guide how the Pike and other national forests decide which trees to cut and which trees to leave.

In campgrounds and along popular trails, the concern goes beyond forest health. Dead trees can eventually fall, creating hazards for visitors. However, removing too many trees can also change the character of the places people come to enjoy, such as trails and day-use areas.

"We want to keep these high value trees that people use to hammock or camp under. They love that shade," Willard said. “What we’re doing in recreation areas is more of like a scalpel.”

At the Little Scraggy Trailhead, a popular access point for the Colorado Trail, Williard pointed out a ponderosa pine. Beetles had hit it the year before in a narrow strip up one side of the trunk. The tree defended itself by pushing resin out of each entry hole, something foresters call pitching out.

“We chose to keep this tree just because it wasn’t mass attacked,” Williard said. “So, it wasn’t going all the way around the tree.”

Help from Team Rubicon 

The work is labor intensive, and partnerships help make it possible. On the South Platte Ranger District, volunteers with Team Rubicon helped remove infested trees from recreation sites.

The partnership also provides Team Rubicon sawyers with valuable training. Working alongside Forest Service personnel gives volunteers experience with different trees and cutting situations they may later encounter during disaster response, including work around homes, roads and utilities.

“We can build confidence out here so that when you have to do it in a disaster zone, then you can say, oh yeah, this is like the tree I did up there at that campground,” said Dave LaRivee, sawyer cadre lead for Wyoming, Colorado and New Mexico with Team Rubicon.

Crews cut and removed a cluster of heavily infested trees to reduce the chance of further beetle spread. They cut the trees into firewood-sized pieces, split them and set them bark-side up so sunlight dries the wood and kills beetles under the bark.

Deciding where to start 

The South Platte Ranger District covers roughly 500,000 acres, which is too large to treat everywhere. Managers have to prioritize where their work can make the most difference.

“I would say the hardest part about managing a large unit like this is deciding where to start,” said Brian Banks, district ranger on the South Platte Ranger District in the Pike-San Isabel National Forests & Cimarron and Comanche National Grasslands.

On his district, that means trailheads, campgrounds and campsites where the public spends time.

The work that the Forest Service has been doing the past few years to improve forest health is starting to show. At Buffalo Campground, the largest campground on the district, crews removed 17 infested trees last year. This year, Williard said, they have not found a single new hit.

“The decisions and treatments that we are implementing today are going to have lasting impacts of years down the future,” Banks said.

Banks said the work is long term, with future generations in mind.

“We know and we’ve seen what happens when you do nothing,” he said. “And that is one of the alternatives that we don’t have any interest in.”