A Fiery Rx for Open Space

by Wendy Underhill

Each year, Chautauqua meadow goes up in flames. Yet, the Boulder Fire Department does nothing to fight these blazes; in fact, it helps light them as part of a land management philosophy known as prescribed burns.
Although highly visible, the annual burns at Chautauqua are mere flickers compared to the total acreage burned by city and county agencies. Each Chautauqua burn involves 1 to 10 acres. Rod Moraga, forest and fire ecologist with the City of Boulder, prescribes 200 acres of burns per year in public forests and grasslands.
Why start a fire intentionally, especially in parks and forests? In centuries past, grasslands and forests burned from natural causes such as lightning strikes. Grasses may have burned every few years; forests, particularly ponderosas like those in the foothills, burned every 10 to 25 years. In either case, ashes deposited nutrients into the soil.
With so little humidity, Boulder’s woods don’t decay as fast as eastern or northwestern forests, making fire the only available natural land scrubber. In settled areas, where fires are suppressed and natural cleansing doesn’t occur, underbrush thickens, making it difficult for seeds to sprout and easier for a major wildfire to erupt. Trees grow that otherwise would have died in natural fires, and shade created by their canopy inhibits the growth of new species and enables species to sprout that wouldn’t naturally grow here. The result is a decrease in species diversity.
Tree thinning is one management tool that may enhance diversity as well as prepare areas for prescribed burns, says Dave Sutherland, interpretive specialist with Boulder Mountain Parks. In fall of 1998, the city thinned trees at Enchanted Mesa to prepare for the Chautauqua burn. “Thinning was a vital part,” Sutherland says, “since it removed small trees that were growing too thickly, in some cases close to the bases of large old-growth trees we wanted to save.” The thinned trees were mostly Douglas firs, which, Sutherland says, “have invaded ponderosa forests in the absence of natural fires that would have kept them out.”
Prescribed burns give native plants, particularly grasses, a chance to compete against introduced species. Generally, introduced species green up earlier than natives. The idea is to burn nonnatives as they sprout, before natives come out in late May. Steve Armstead, senior ranger with Boulder Mountain Parks, admits some prescribed burns may have been more harmful than helpful in the native/nonnative battle. But, he says, “each time we burn [Chautauqua meadow], we learn.”
Prescribed burns at Chautauqua began in 1994, and the area now serves as a fire research site. Two to three weeks after a prescribed burn, the “sudden flush of new life” hides the black signs of fire from all but the most observant hikers, Armstead says.

TRICKY TACTICS
Filling a burn prescription is tricky, partly because air quality controls effective Nov. 1 to Feb. 28 forbid fires in those months. Summer is usually too hot and dry for safe torching. In remaining seasons, a stiff breeze, no breeze, a breeze in the wrong direction, rain or other uncontrollable factors can cancel a burn.
When a “clear day with a lot of lift” occurs to carry smoke skyward, Moraga says he can burn 150 acres, with the help of as many as a half-dozen agencies including Boulder County Parks and Open Space, Boulder Open Space and Mountain Parks, volunteer fire departments and the U.S. Forest Service. No single agency has enough expertise or staff to handle a burn on its own, Moraga says.
The lead agency on a prescribed burn maps out details: Where to burn? How much? Should it be a superficial or deep burn? On the scheduled day, the burn area is marked off to prevent fire from crossing into adjacent land. Sometimes a “wet line” is used, where the edges of a burn area are hosed down. Other times, it’s a “black line,” where boundaries are burned first to remove fuel from a swath. In either case, fire has trouble crossing the boundary.
When the boundary is secured, the fire is lit via “drip torches” that ignite a diesel mixture. Sometimes the plan is to let wind move the fire along. This type of burn has higher flames that travel fast and don’t burn as deeply as a back burn, or one that goes against the wind.
More often than not, fire officials end up coaxing flames along. Containment is an ever-present concern, and trained staff along all boundaries immediately extinguish stray embers. As many as 40 or 50 people may work a prescribed burn, some just to gain experience. Fire trucks stand by, too. Should a prescribed burn become a wildfire (which hasn’t happened here), it’d be treated as any unintended fire, with reinforcements and aerial water drops.

SMOKE SIGNALS
Nature doesn’t always cooperate with prescribed burns, which sometimes backfire, so to speak. In the 1998 Enchanted Mesa burn, for example, predicted winds didn’t materialize, and the lower Chautauqua neighborhood was inundated with thick smoke for several days, causing alarm among residents and sharp criticism of prescribed burns.
But prescribed burns have been a management tool for a long time, Moraga points out. The Bureau of Land Management, for instance, has prescribed burns of up to 3,000 acres on its land during the past 30 years. What is relatively new are “urban interface” fires—those across the street from $500,000 homes, where precision, precautions and risk-reduction are essential.
That’s what Boulder fire ecologists practice with prescribed burns at Chautauqua meadow and elsewhere. In fact, Boulder is starting to export fire-lighting knowledge to other western communities, which also need a prescription to maintain the health of their natural lands.

Photos courtesy Boulder Mountain Parks