WESTERN SAN JUANS - The West Fork Complex wildfire continues its unchecked rampage this week through southern San Juan Mountain forests decimated by bark beetles.
It is, perhaps, a logical assumption that these vast swaths of standing dead trees are to blame for the fire’s savage intensity.
But research conducted by Dr. Jason Sibold, a forest ecologist at Colorado State University who has studied wildfires and bark beetle outbreaks in subalpine Colorado forests for 15 years (and recently visited Telluride to take part in a forest health workshop sponsored by the Telluride Institute’s Watershed Education Program), shows that wildfire risk in subalpine forests is extremely high during severe drought conditions, with or without bark beetle outbreaks.
The severity of the West Fork Complex wildfire should be blamed not on the massive beetle kill, Sibold maintained, but rather on the cascading effects of climate change.
“Everything you see says the fires are feeding on beetle-killed forest. But the big thing driving this is that it’s so doggone dry, and it’s been dry for 11 years, more or less,” he emphasized. “That area is experiencing extreme drought, low snowpack, late onset of winter, early snowmelt and warmer springs and summers,” he said, and “there are reports of incredible fire behavior all the way up at tree line. A lot of those places, in the old climate scenario, would still be under snow. There’s no way they would be burning. We still don’t know exactly what role beetles are playing, but this is a drought-driven fire.”
Sibold has conducted extensive research at several sites throughout Colorado. One project took him into the exact area that has in recent days been decimated by the West Fork Complex blaze. Here, through extensive tree ring sampling, he discovered that spruce beetles are actually endemic to the area. Past significant outbreaks killed off only 30 to 40 percent of the trees, however, while the current infestation is breaking all the rules, with the beetles munching their way through every single drought-stressed tree they encounter.
“There are so many beetles, they will eat anything,” Sibold said. “In theory, they are not supposed to attack seedlings and saplings; they cannot successfully reproduce in saplings, because the phloem is not thick enough for them to reproduce. But there is nothing else for them to attack; they are going after everything.”
Sibold’s research also shows that in spite of past beetle-kill outbreaks, the area where the West Fork Complex fire is now raging has been remarkably immune to wildfires in the past, going back as far as the tree record allows, due at least in part to the fact that the mountains used to hold onto their snowpack well into wildfire season, helping to keep trees healthy and wildfires at bay.
When wildfires did happen in the past, they behaved very differently. “They would spread halfway up a valley and stop because of avalanche breaks and higher elevation forests which would still be wet. But we are seeing that this fire does not care about topography or avalanche breaks.
“It did not get that memo,” Sibold joked, and so, “it is breaking all the rules of at least the past 500-600 years.”
Modeling work conducted by research ecologist Carol Miller of the Aldo Leopold Wilderness Institute, the prestigious federal institute that funded Sibold’s work in the San Juans, corroborates this theory that a new paradigm is at play. Miller’s work shows that in the past, snow in the San Juans lingered for so long, there wasn’t sufficient time between snowmelt and the start of monsoon season for a real fire season to develop. But with climate change, earlier snowmelt creates a true fire season in the San Juans, even at high elevations.
“This is a big change,” Sibold said.
There are potential policy implications to Sibold’s research. In April, he was called to Washington, D.C. to testify before the House Subcommittee on Public Lands and Environmental Regulation regarding the Healthy Forest Management and Wildfire Prevention Act (H.R. 818).
This bill, sponsored by U.S. Rep. Scott Tipton (R–Colo.), seeks to decrease the perceived elevated risk of wildfire to mountain communities as a result of recent and ongoing bark beetle outbreaks by thinning tree densities in beetle-affected stands; and to mitigate the risk of future bark beetle outbreaks through forest thinning projects in healthy stands where the risk of outbreaks is perceived as high.
To the dismay of the bill’s supporters, Sibold’s testimony largely debunked the premises upon which it is based.
“The scientific evidence does not suggest that fire risk has increased as a result of recent and ongoing bark beetle outbreaks,” he told legislators. “In contrast, the vast majority of evidence suggests that bark-beetle outbreaks have either no influence on fire risk or potentially decrease fire risk,” due in part to the fact that as the trees die, their needles eventually fall to the forest floor, making the crowns of trees, where forest fires tend to feed, less flammable, “and that weather” – most particularly, drought – “is the dominant influence on fire risk in these forests.”
Sibold also testified that thinning healthy forests does not seem to mitigate the risk of bark beetle outbreaks, particularly when they have already reached epidemic proportions nearby.
“In contrast, forest-thinning projects could result in several unintended consequences,” he warned – including killing seedlings and saplings in beetle‐affected stands that are critical components of forest recovery, and increasing the likelihood of wind toppling remaining trees, which often acts as a catalyst for the development of bark beetle, he said.
Tipton himself, as the sponsor of the bill, has said he endorses the idea that it is important for beetle-kill to be harvested and healthy forests to be thinned, to prevent wildfires and restore forests, while critics of the bill allege that it plays on people’s fears about wildfire to push through the timber industry’s agenda.
Sibold maintains that the bill’s supporters should simply call a spade a spade.
“If a lawmaker wants a more vibrant timber industry, then cutting trees is a logical conclusion,” he said. “But people should not be fooled into thinking you can thin forests and decrease risk for fires; you just can’t do it. I guarantee you, this fire in the San Juans is going through a huge range of tree densities, sizes, canopy structures and apparently does not care at all. Unless people are willing to have thinning to the point where it takes out a large percentage of the trees –over 50 percent – there will not be a whole lot of an impact.”
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