USA — As the lodgepole pine forests west of Laramie turn redder and redder with each season, its not hard to look at all those dead and dying trees as tinder piled and awaiting a spark. Indeed, fire seems to be the logical next step for an aging forest decimated by insects.
The mountain pine beetle also visited the lodgepole pine forests of Yellowstone National Park in the decades before the summer 20 years ago in which they burned so famously, perhaps portending whats ahead for southeast Wyoming in the coming years.
Indeed, fire management officials are bracing for flames as they await the inevitable death of almost all the lodgepoles in the Medicine Bow-Routt National Forest. Theyre educating homeowners and protecting communities.
But not everyone who studies wildland fires and insect epidemics will tell you a catastrophic fire is certainly coming. While the cause of forest fires is a complex balance of fuel and weather, the relative importance of one versus the other is still open for debate, and the mountain pine beetle may not be the harbinger of fire that it seems.
In the Medicine Bow-Routt National Forest, 90 percent of lodgepole pines greater than five inches in diameter will be dead in the next two to three years.
Tony Tezak, forest fire management officer for the Medicine Bow-Routt National Forest, estimated that more than 150,000 acres of the forest are currently infected by the mountain pine beetle, and the spread is inevitable, leaving a swath of red-needled trees across Wyoming and Colorado.
A fire in these red forests would almost certainly spread to the treetops, fueled by the dead needles.
Once you make that transition from the ground to the crowns, you have a catastrophic fire. Its very, very difficult to control, Tezak said. Its exposed to the wind. Theres nothing to stop it.
But that danger is short-lived, as the needles remain on the dead trees for just a couple seasons before falling to the ground.
At that point, scientists say, the fire danger would actually be lower as the dead trunks turn gray and gradually fall during the next few decades. Without needles, tree canopies are much less dense and in some cases no longer touching this stage is analogous to trying to set fire to a row of telephone poles, Dominik Kulakowski, an assistant professor of geography at Clark University who has researched disturbances in forest ecosystems, said in an e-mail. He used to be a research scientist at the University of Colorado.
Things get more complicated as those dead trees fall or are blown over, a process that will continue for many years and lead to the growth of smaller trees that suddenly have sunlight and room.
A paper written by Kulakowski and scientists from Colorado State University, University of Colorado and University of Idaho theorizes that the danger of a crown fire may increase over the decades following a pine beetle outbreak for two reasons.
First, fallen trees that catch fire could create flames large enough to reach tree canopies.
Second, fast-growing young trees could carry a fire from the ground to the treetops.
With all that fuel lying on the forest floor coupled with intermingled new growth and grass, a ground fire would perhaps be more intense and even risk sterilizing the soil, Tezak said, which would mean a longer recovery time afterwards.
Such a fire would also be more dangerous to fight because of the difficulty of getting firefighters in and out.
Jim Myers, resource team leader for timber and silviculture for the U.S. Forest Service, said a beetle epidemic in the decades before the summer of 1988 occurred in the forests of Yellowstone, possibly contributing to the intensity of those fires.
The key thing there is the heavy fuels will still be there, he said. We think well probably have some fires as a result. It may not be immediately.
The lodgepole pine trees west of Laramie are between 90 and 120 years old, Myers said, and approaching the end of their lives.
And generally lodgepole regenerates through fire, Tezak said. Serotinous cones produced by the tree are sealed by resin that only melts in high heat the trees wont regenerate without fire in some cases.
According to Kulakowski, lodgepole pine stands, which are naturally quite dense, have historically burned at high intensity but at long intervals, meaning that a long time between fires is not unprecedented.
Tezak said the Medicine Bow National Forest is sometimes called the asbestos forest, because it seems never to burn.
He remembers working on the Teton in 88: We used to call it the asbestos forest.
The lesson he learned?
If the conditions are right, it burns, he said.
Those conditions include more than just dead fuel, especially in lodgepole forests. Kulakowski said the naturally dense nature of such forests means that theres enough fuel for a serious fire even without beetle-killed timber.
If you walk through a typical lodgepole pine forest that has not been affected by mountain pine beetle, even a casual observer may note that there is no shortage of fuels these forests are dense and the canopies of the trees are touching, which would facilitate the spread of wildfire, he said.
In such a forest, then, the presence of dead fuel as opposed to live fuel wouldnt make as much difference as a drought would.
In these types of forests, the best available science indicates that climate is the limiting factor, he said, adding that theres a strong statistical relationship between drought and severe fire in lodgepole pine forests.
He admitted that research is still ongoing and opinions differ.
Based on research that has reconstructed how fires have functioned in lodgepole pine forests over the past several centuries, changes in fuels have not been nearly as important as fluctuations in climate, he said. It is the climate we should be concerned with more than the beetles.
Back in Yellowstone, remember, drought and wind contributed to the hazard.
What this means for the forests in Wyoming and Colorado is anybodys guess, and predictions are based on theories, which cant account for an inattentive camper or a rogue lightning bolt. Kulakowski and Tezak both advised homeowners in the forest to take basic steps to protect their homes, both for their sake and that of firefighters.
Tezak said hes obligated to protect homes and communities, but forests want to burn, and thats best for the ecosystem anyway.