SANTA FE, N.M. — Prescribed burning of forests is done to remove excess fuels in order to prevent catastrophic wildfires. Some years ago, a well-known environmentalist, appalled by this practice, stated that it was “absolutely impossible to fire the forests without destroying the young growth, not to mention the constant risk of the fire breaking out of bounds and destroying buildings, fences, and mature timber.”
“It can be stated without hesitation,” he wrote in an article in Southwestern Magazine, “that a large percentage of the chaparral or brush areas found in the Southwestern states were originally covered with valuable forests,” but that repeated prescribed burns had gradually destroyed their productivity. He predicted that, should this practice “continue for another fifty years, our existing forest areas would be further curtailed to a very considerable extent.”
That environmentalist was Aldo Leopold, and the year was 1920. Prescribed burning was then called “light-burning,” and it was done for the same stated reasons as today. Ten years earlier, the newly created U.S. Forest Service had finally put an end to this destructive practice on the lands that it controlled, and already new tree seedlings were occupying previously unforested areas. However, many people were pressuring the Forest Service to resume the practice of light-burning. Leopold wrote his article to counter their propaganda.
Light-burning, said Leopold, destroys the seedling trees needed for forest regeneration, reduces forage for wildlife, destroys soil humus needed for tree growth, destroys all ground nests; and inflicts scars on trees which makes them more susceptible to insect damage, rots the wood and increases resin which intensifies subsequent fires.
Leopold’s philosophy prevailed for over half a century. But in 1977, the Forest Service resumed prescribed burning in all national forests, a program now well into its fourth decade and a dismal failure.
In 2009, William Lawrence Baker, a forest fire researcher and professor at the University of Wyoming at Laramie, published a comprehensive survey of the subject, titled “Fire Ecology in Rocky Mountain Landscapes,” a 600-page book with a bibliography mentioning more than 1,500 published studies.
The idea that fire was once more frequent in our forests, or that tree density was once less, is “not generally supported by the evidence,” Baker says. He concludes that thinning the forest is inappropriate and unlikely to be of benefit.
Agreeing with Leopold, the studies show that even low-intensity fire kills slow-moving and nesting animals, chemically alters the soil, destroys native seeds and beneficial fungi and opens the forest to invasion by rapidly-growing non-native weeds, increasing rather than reducing fire risk. In addition, thinning the forest admits more sunlight and air. This raises temperatures of surface fuels, reduces fuel moisture, and increases wind speed, further increasing fire risk. One study from northern New Mexico found that native grasses and shrubs remained reduced by half to three-quarters even 16 years after a low-intensity fire.
“Wildland fire management in the United States today,” writes Baker, “has been shown to be expensive, ineffective, and logically misdirected … Ineffectiveness is documented by rising amounts of burned area in spite of increasing fire control and fuel reduction.”
Like Leopold, Baker notes that prescribed fires kill most small trees and some large ones, and that trees continue to die for at least 10 years after even a low-intensity fire. “If similar fires occurred every 10 years,” he says, “canopy trees could be half killed and not replaced in about 100 years.”
Yet this is exactly what the Forest Service has begun to do in the Santa Fe National Forest.
Two years ago, responding to the plan to burn all areas of the Santa Fe atershed every seven years on a rotating basis, Baker warned that the tree ring data have been misinterpreted.
“Our published research suggests fire intervals of 5-20 years imply fire rotations (time to burn across an area once) of about 50-300 years,” he wrote. “The Watershed plan for a 7-year rotation may mean 7 to 40 times more fire than occurred historically.”
In September, the Forest Service announced that it is proposing to extend its burning program into the Pecos Wilderness.
Aldo Leopold, whose idea it was, in 1924, to establish wilderness areas within the national forest system, did not intend that prescribed burning be allowed in them. Congress, in 2003, specifically prohibited forest thinning or prescribed burning within designated wilderness areas.
The Forest Service should not be permitted to go forward with this plan.