Fire officials investigating how forests have changed after bark beetle infestations
As Colorado’s bark beetle infestations have faded, ideas have changed about the insects’ impacts on mountain ecology and the prospects for wildfires in beetle-afflicted areas.
A current study of forest recovery by Robert Andrus, Sarah Hart and Thomas Veblen was recently published in the journal of the Ecological Society of America. Andrus and Veblen are professors in the Geography department at the University of Colorado Boulder. Hart is a professor in the department of Forest and Wildlife Ecology at the University of Wisconsin Madison.
The study focused primarily on forest recovery in Colorado’s southern mountains. But in a telephone interview, Veblen said many of those findings are also relevant in Colorado’s central and northern mountains.
Veblen noted that in the early 2000s, a mountain pine beetle outbreak that began in the 1990s attracted a lot of attention from politicians and some land managers.
Veblen said the “initial, knee-jerk reaction” was that the abundance of dead trees would lead to an increase in the probability of the outbreak and severity of wildfires.
Over the ensuing years, Veblen said that fear “is not justified.”
The drive to “do something” about the outbreaks resulted in widespread logging to reduce the fire hazard. That wasn’t really necessary.
Veblen said that fire hazard depends in large part on “fine fuels,” including grasses and needles dropping from dead and dying trees. But putting more of those fuels on the ground has resulted in a decline in the probability of forest-consuming “crown fires,” in which fire jumps from treetop to treetop.
But Veblen added, dead and dying trees can make access to fire sites “extremely hazardous,” particularly in stands of lodgepole pine, the dominant species in this area.
By the 1990s, those stands of lodgepole pine were roughly 100 years old, the result of widespread fires in the middle of the 19th century. Trees that old were ripe for a beetle infestation.
Over the past 15 years or so, land managers have altered their thinking to concentrate more on what’s called the wildland-urban interface — zones where human development comes in contact with wildlands.
Veblen said at this point, the idea is to concentrate efforts in those areas, as well as roads and trails into the forests.
Paul Cada is the Vail Fire Department’s wildland specialist. Vail has much of the valley’s wildland urban interface. In a phone interview, Cada agreed that fire behavior has changed due to beetle infestations.
What’s known about the post-beetle landscape has changed how land and forest managers view fires, and how to prepare for fires. The town is now in the final stages of drafting a community wildfire protection plan, and those changes will be incorporated.
“The goal is to prevent landscape-scale, high-severity events,” Cada said. That approach includes letting some fires do their work. The challenge, Cada said, is to identify ways to contain fires to a relatively small area.
In a standard fire season, Cada said most fires are confined to small areas ranging from a single tree to less than an acre. That same season might see a few slightly larger fires of up to 15 acres. Larger fires usually require some kind of “significant” weather, say a dry winter followed by a hot summer.
To keep those fires small, measures near the wildland urban interface include forest thinning and creating openings in the forest canopy.
Outside of the lodgepole forests, there are a number of local aspen stands that are getting on the “over mature” side, Cada said, adding that those stands have been growing too long without being thinned by a naturally-occurring fire. In those cases, some prescribed burning could be useful.
Those fires mean land managers are picking the time, place and weather conditions that have the most benefit and lowest risk, Cada said. That particularly applies to interface areas.
Over the past 15 years or so, as the wildland interface has expanded, thinking about fire management has shifted.
The thinking a few years ago was “control the vegetation and the problem goes away,” Cada said. But large fires such as the Camp Fire in California revealed a different reality — fire jumping from home to home, without much damage to surrounding vegetation.
The evolving management philosophy led town of Vail officials last year to pass revised building codes mandating more fire-resistant materials in new construction.
And ideas continue to shift about wildfire near populated areas.
“Almost monthly there’s some new, groundbreaking research about building components or ways communities are engaging (around the interface),” Cada said. That’s why it’s important for communities to stay as up to date as possible, he added.”
Back in the forest
While ideas about wildfire are changing, there’s good news from the affected forests.
Veblen said at the beginning of the beetle outbreaks, land managers worried about long-term recovery. Those concerns turned out to be largely unfounded.
“Leave the forest along and it’ll be fine,” Veblen said.
But that doesn’t mean the forest growing now will look like the one devastated by insects.
Veblen said land managers are seeing a good deal of species replacement in the natural new growth coming up through the dead trees.
Some lodgepole pine is being replaced by aspen and subalpine fir trees, he said. Spruce is popping up at higher elevations.
Current conditions provide land managers with some advice for the coming decades.
“Management should be aimed at efforts to improve recovery,” Veblen said. “You would want to create pre-outbreak conditions of small trees.”
But that regeneration may not be obvious at first glance.
“It may take 20 years or so for big lodgepole pines to fall over,” Veblen said. “But walk around in those forests, and recovery is well underway.”
Vail Daily Business Editor Scott Miller can be reached at email@example.com or 970-748-2930.