Scientists urge restraint in thinning piñons

A group of scientists and researchers is challenging the conventional notion that dead piñon trees need to be aggressively cleared to reduce the risk of catastrophic wildfire.

However, some fire experts disagree and worry that the researchers’ advice may discourage private landowners from taking necessary steps to protect their rural homes.

In a six-page letter to U.S. Agriculture Secretary Ann Veneman and Interior Secretary Gale Norton, dated Dec. 23, 2003, 13 scientists from around the Southwest urge land managers “to resist pressures to launch ambitious salvage or tree-removal operations in the mistaken assumption that the dead trees constitute a serious fire hazard.”

The scientists argue such efforts could damage the delicate piñon-juniper ecosystem.

Among those signing the letter are Bill Romme, formerly of Fort Lewis College in Durango and now professor of fire ecology at Colorado State University; and Lisa Floyd-Hanna, head of environmental studies at Prescott College in Arizona.

Floyd-Hanna spoke recently in Mancos and Dolores about the newly published book “Ancient Piñon-Juniper Woodlands: A Natural History of Mesa Verde Country,” to which she and Romme both contributed chapters.

That book does not deal directly with the fire-management issue covered in the letter, but discusses the complex and delicate ecology of the piñon-juniper forest. It describes threat to the PJ habitat, such as air pollution, invasive weeds, and habitat fragmentation.

In the Dec. 23 letter, Romme, Floyd-Hanna and the other researchers perceive another threat: too-aggressive thinning. They describe the factors that combined to create the “perfect storm” that is wiping out tens of millions of piñons, as well as ponderosa pines and other species, throughout the Four Corners. Decades of unusually high moisture that prompted excessive foliage in the area, followed by a severe drought and a devastating bark-beetle epidemic.

Now, land managers are wondering how to deal with such an extensive tree die-off, and are contemplating over-zealous thinning efforts, the researchers believe.

They contend that the dead trees will pose a critical fire threat only for a short while, until their needles fall; and that afterwards, the fire danger will be lower than it was when the trees were living, because the foliage won’t be as dense.

“Although dead woody fuel loads will increase dramatically, the actual risk of damaging crown fire will likely DECREASE in many pinyon-juniper woodlands,” they write, “because the mass and continuity of live canopy fuels will be reduced once the dead needles fall from the trees (which occurs usually within about a year of tree death).”

After that, they maintain, the risk of catastrophic wildfire will be even less than it was before the tree die-off because there won’t be needles left to burn in the crowns.

“Large, intense fires in southwestern pinyon-juniper woodlands almost always occur as wind-driven crown fires under conditions of extremely low humidity and fuel moisture,” as the recent major fires in Mesa Verde National Park demonstrated, they state.

Crown fires primarily burn the live needles and small twigs of trees, “not the coarse wood of stems and branches.” The researchers believe that although dead needles may ignite more easily, drought-stressed live needles burn more intensely because they contain highly flammable compounds called turpenes, which disappear when needles die.

The moisture conditions and density of the living trees are more important factors in wildfires than how much dead matter is on the ground, the researchers believe. “The death of large numbers of canopy trees actually reduces the mass and continuity of canopy fuels, once the dead needles fall,” the letter states.

As the piñon limbs and trunks decay and fall, the fire danger will decline even further, the scientists believe. Piñons begin to fall apart within a few years, they say.

Although clearing the dead trees might still seem prudent, the researchers believe it could have unfortunate ecological consequences, including:

  • Damage to the delicate biotic crust on desert soils.
  • Harm to piñon seedlings not affected by the beetles. In addition to possibly being trampled or chewed up by a hydromower, the seedlings could die if the dead wood they use as protective shade is removed.
  • Removal of dead trees that are depended on by wild animals for homes and hiding places.
  • Invasion by noxious weeds such as cheatgrass.

The letter supports localized fuel reduction to protect structures or other important resources, but argues against “extensive salvage efforts.”

“We urge a reevaluation of ongoing and planned pinyon-juniper thinning operations, in the interest of preserving the healthy pinyon trees that have managed to survive,” the scientists conclude.

But Phil Kemp, a forester with the Mancos-Dolores District of the San Juan National Forest, doesn’t buy all of the researchers’ arguments. He shares their concerns about noxious-weed invasions and destruction of seedlings, but he doubts their conclusions about the quick drop in wildfire risk.

“It’s our belief that the (wildfire) risk may not be particularly reduced for up to 20 years” after the trees die, Kemp said. Until then, when the trees are thoroughly decayed, the risk will remain high, he believes.

“Prior to that,” he said, “you have more fuels on the ground – drier fuels which tend to carry a fire better – and you also have probably an increase in grass, forb and shrub growth because you’ve reduced the tree canopy,” allowing more sunlight and moisture to reach the ground.

“Just the trees dying doesn’t mean to me that the risk of fire is at a level where we don’t need to worry,” he added.

Kemp also doubts that any widespread thinning of dead piñons is feasible on public lands outside the “urban-interface zone,” adjoining private lands and structures.

“Our focus has been to reduce fuel loads in those areas around private lands, homes, developments, etc.,” Kemp said. “The money we have to treat fuels is going to be focused on the wildland-urban interface.

“If you look at something like the Disappointment Valley, for example, we will probably be doing a little (fuels-reduction) treatment in spots, but by and large there won’t be either the money, or the emphasis for what money we do have, to put it into (remote) places like that.”

Kemp said two hydromowers – giant mowers that chew up trees and brush – are currently being used to thin trees on BLM lands in the local San Juan Resource Area. One is operating just south of Summit and Puett reservoirs, and another is at work in the Aqueduct area directly northwest of Mancos between highways 160 and 184.

Some other BLM areas targeted for future thinning include land west of the Indian Camp Ranch development in western Montezuma County; tracts east of Egnar; and an area south of Highway 160 between Cortez and Mesa Verde National Park. All are near private land, Kemp said.

Public-lands managers ARE concerned about potential damage to piñon seedlings, he said. Hydromower operators have been told to avoid seedlings they see, and operators are also leaving some patches of vegetation untouched.

“We have a concern and we are going to lose some of the smaller, younger trees as we operate our equipment, but we’re trying to reduce that loss,:” Kemp said.

He said references in the letter to “extensive salvage efforts” are misleading because no such efforts are planned locally.

“We’re not doing any real salvage of P-J,” he said. “We’re offering some of this dead material as personal-use firewood but that’s a drop in the bucket” compared to the countless acres of dead trees that won’t be touched.

“We’ve got no other salvage efforts under way,” Kemp said. “Piñon is not a high-value woody species.”

But Floyd-Hanna, contacted by phone, said – though she has received no reply from Norton or Veneman – she has heard from BLM employees in Arizona that more extensive thinning and salvage may be planned in that state.

“There’s a question about the definition of what is urban interface,” she said. “They say they’re going to stay in areas mostly that are threats to urban areas, but I’ve heard from the BLM in Arizona that there is pressure for them to go into other areas that might be deemed important.”

A major reason for not rushing into fuel-reduction projects is that there is little information about how they affect the PJ ecosystem, she said. “We don’t have any good data on how well restoration works there. We do with the ponderosa pine, but we don’t have that with piñon. Our fear is that they’ll be starting with no real restoration plan that’s been tested.”

She agreed that thinning efforts such as those undertaken at Mesa Verde certainly can be successful in saving structures. For instance, cleared sites in the park provided a staging area from which firefighters could battle the 2,600-acre Long Mesa Fire in 2002.

But she hopes fire officials aren’t giving landowners the impression that thinning can save their personal patch of forest. The thin-barked piñons, unlike ponderosas, are very sensitive to even low-level fires and will die, she stated.

“You won’t be introducing a surface-fire regime that will allow the trees to survive,” she said. “They don’t.”

She said the researchers have run numerous fire models and believe the flammability of the piñons will go up for a short period, maybe a year, and then drop. “The destruction we might do by cutting them all down might be worse,” she said. “We’re recommending people not do anything, from a conservation standpoint,” except in areas immediately near their homes.

Kemp, however, maintains that somewhat more extensive thinning efforts remain critical for protecting structures. “I’m a little concerned that this letter will result in some complacency about fuel conditions and the risk of catastrophic fire,” he said. “If you were to read this, you would think, a year after these trees die, everything’s going to be OK and I’m just not convinced of that.”

“Ancient Piñon-Juniper Woodlands: A Natural History of Mesa Verde Country,” is available at Maria’s Bookstore in Durango. It can be also ordered through Main Book Company in Cortez or the Dolores Bookstore in Dolores.

From March 2004.