Forest experts are warning that Boulder’s foothills could look markedly different this year as a mountain pine beetle outbreak intensifies, with potentially far-reaching impacts on recreation and fire risk. Landowners are urged to watch for signs of beetle infestation.
The state has taken action: Gov. Jared Polis announced a task force in December aimed at protecting Front Range forests from mountain pine beetle over the next decade. Boulder County has seen increased beetle activity in several areas, including upper Lefthand Canyon and Jamestown.
Years of drought, warmer temperatures and overcrowded forests have weakened trees, creating ideal conditions for beetles to spread rapidly and overwhelm remaining healthy stands.
“It is expected to turn into an epidemic and become way more widespread,” said Shane Milne, forestry supervisor for Boulder County Parks and Open Space.
The brood of beetles already in trees and poised to spread this summer is substantial, according to Colorado State Forest Service entomologist Dan West. Any pine trees seen with red or orange needles in the fall have already been heavily invaded and are on their way to dying. Many more trees that appeared green last summer are holding broods ready to spread.
“It’s kind of this cake that’s already being baked,” West told Boulder Reporting Lab.
He explained that mountain pine beetles are native to Colorado, generally working as natural “sanitizers” of the forest by clearing trees struck by lightning or disease. But years of drought and overly dense forests have stressed even healthy trees, giving beetles the upper hand and allowing their numbers to surge.
The previous outbreak of mountain pine beetle in Colorado lasted from 1996 through 2013, impacting trees in 3.4 million of the state’s 4.1 million forested acres. The remaining roughly 700,000 acres spared by that outbreak, now at risk, are in the Front Range.
“We’ve seen this uptick from 2020 through 2025 of mountain pine beetle affecting those remaining low-elevation ponderosa pine forests,” West said. “The footprint of mountain pine beetle is only going to grow this upcoming year, and we anticipate the intensity to increase.”
Unlike the previous outbreak, which mostly occurred on public land with limited communities, an outbreak on the Front Range would impact several heavily populated areas, with urban trees potentially also at risk. Prevention and treatment will likely be more difficult because of the mosaic of public and private land ownership.
Milne said beetle mitigation varies by landowner, resulting in uneven treatment and prevention. “It’s just hard to make a dent in it,” he said.
Ripple effects in the ecosystem and beyond
According to West, when large numbers of trees are lost, the consequences can ripple outward. Loss of tree canopy means snowpack can melt sooner. As dead trees decompose, they can affect water quality. Recreation can suffer as views change, the risk of falling trees increases, and hunting opportunities shift as animals search for better tree cover. Fewer trees can also affect air quality, as dust and debris have fewer natural filters, especially during high winds.
“It really is just the whole gamut,” West said.
Chad Julian, a wildfire mitigation specialist with the Colorado State Forest Service, added that falling dead trees also pose threats to homes and utility lines. Municipalities may need to invest in removing dead trees near infrastructure.
When it comes to wildfire, experts say beetles are one factor among several that can shape how fires behave.
“Favorable fire weather, though, that is really what’s key,” Julian told Boulder Reporting Lab. That means low relative humidity and high winds. If Boulder’s forests see plenty of precipitation in the coming years, beetle impacts may not add much more to fuel loads.
But assuming things stay dry, what happens to those dying trees — and when — could really change how fire moves through the forest. That process unfolds in stages as infested trees die.
First come the red needles, the most visible sign of a beetle attack. While drier than green needles, red needles remaining on trees do not increase ignition risk. But if a fire starts, they can help carry flames into the tree canopy, where it’s extremely difficult to fight. When dry needles fall, they add to fuels on the forest floor.
Dead standing trees, while ghost-like, are not ignition risks until they fall and are exposed to ground flames. Because they don’t have needles, they are less likely to spread fire. But they can collapse without warning and endanger responding firefighters.
The outbreak on the Front Range will primarily affect ponderosa pines, unlike the previous outbreak that hit lodgepole pines. Julian noted this could worsen fire risk. Ponderosas have denser canopies and are currently overgrown compared to historical norms. He also expects the highest danger window to fall between September and May, as Colorado’s ponderosa pines live in climates with dry winters. The Front Range also has more development within wildfire-prone areas.
“So when you look at that value of risk, there’s going to be more impacts to homes and people’s backyards in the ponderosa outbreak,” Julian said.
Spring is the best time for action
Mitigation becomes far less effective once large swaths of forest are infected. No treatment exists once beetles enter a tree.
“Once the beetles get inside, the game’s over. You’ve got to fell that tree and focus your energy on the trees that are remaining,” West said.
The best time to act is in the spring, before beetles emerge in search of new hosts. Large-diameter trees tend to be impacted first. West recommends pheromone packets that trick beetles by signaling that a tree is already infected, a method that can be 90% effective in this early stage.
Landowners should regularly inspect their property, marking and removing infested trees. Signs include popcorn-like resin clumps on trunks, boring dust, small exit holes and needles turning yellow or red — evidence of a successful attack.
The best long-term defense is a healthy, well-managed forest with tree diversity.
“Managing your forest for diversity in terms of ages and species is kind of your best preventive measure,” Milne said.
At least two consecutive years of average or above-average precipitation would be needed to end the outbreak. Additional mitigation information can be found on the Colorado State Forest Service’s mountain pine beetle page.