The snowpack is meager for this time of year and temperatures are above normal, but it is still chilly enough to warrant warming up a bit with a discussion on wildfire.
It’s interesting to look back at fires from several years ago to learn about how they changed the landscape. Let’s revisit the Million Fire and West Fork Complex, both of which burned in the San Juan Mountains, but in different forest types and were managed differently.
The Million Fire burned in 2002, our driest year since stream flow records have been kept starting in 1890. The fire burned over 9,000 acres in mixed conifer forest composed of ponderosa pine, Douglas fir, limber pine, white fir, and blue spruce, as well as through meadows and aspen groves. The trees were mostly green and alive.
Satellite imagery and field evaluations determined more than 50 percent of the fire burned at a high severity and more than 40 percent at a moderate severity. Fire severity is a measure of what was consumed: how much of the organic matter was burned above and in the ground. The chance of soil erosion increases with moderately severe burns and is even more likely in high severity burns. Indeed, it was determined that more than 70 percent of the Million Fire burned area was at high risk for soil erosion.
And erode it did. In late July, 2002, a thunderstorm sent rocks, soil, debris and ash down the slopes of the Million burned area killing all the fish in Million Reservoir and several hundred fish in the Rio Grande. Beaver Creek Road was temporarily blocked by debris and ash filled the yards of several homes below the burn.
Grass seed was spread by air over the burned area in the fall at a cost of well over a million dollars in an attempt to stabilize the soils. Unfortunately, very little of the seed sprouted in 2003 and the erosion continued. The only positive news was that aspen trees were sprouting in the burned groves at over 15,000 stems per acre in places. By the autumn of 2003, many of the aspen were already three to four feet tall.
Forest Service employees who had worked to rehab the burned area were downtrodden. All that work, all that money and for what? But, our ecologist told everyone not to give up hope; maybe next year.
He was right. Grass sprouted throughout much of burned area forming fields of green below the charred trees. Erosion from the hillsides greatly subsided as the soil stabilized.
Three fires made up the West Fork Complex: the Windy Pass, West Fork and Papoose Fires totaling about 109,000 acres. These fires burned mostly in beetle-killed spruce-fir forests. Eleven percent of these fires burned at a high severity and 49 percent at moderate severity. Fifteen percent of the burned areas were considered to be at high risk for erosion.
New studies done since the Million Fire indicated there was less than a 50 percent chance that spreading seed in burned areas would speed up stabilization of soils – we got lucky with the Million Fire burned area. Plus, it would cost many millions of dollars to cover the West Fork Complex burned areas, money the Forest didn’t have.
So what happened?
Several small to mid-sized debris flows occurred within the burned areas and there were fish kills in a few drainages and possibly one small section of the Rio Grande. But because the fire severity wasn’t as high and there was a good monsoon season in 2013, native pioneer plants such as fireweed and heartleaf arnica quickly moved in and began stabilizing the soils.
Today, grass, herbaceous plants, shrubs and aspen are thriving in all of the burned areas. Aspen trees are more than 20 feet tall in parts of the Million burned area and up to eight feet tall in the West Fork Complex. Seventy years from now, all will have mature aspen forests and open meadows similar to what we already see in so many areas of the Rio Grande National Forest today.
Mike Blakeman is the public affairs specialist for the Rio Grande National Forest. He spends much of his free time scrambling around the mountains with a camera in his hand.