ON THE OPEN RANGE: A Guest Column FROM GEORGE WUERTHNER

Big Burns Vs. Forest Thinning

By George Wuerthner, 3-04-07

	ABOVE: George Wuerthner. BELOW: The Derby Fire from the highway near Big Timber, photographed in the early few days of the blaze by Jeremy Lurgio.

One hears continuously from politicians, timber cutting advocates and even some conservation organizations that we can reduce fire hazard and improve forest “health” with an aggressive forest thinning program.

The idea is that if you cut out some of the trees, you will eliminate the fuels that support large blazes and reduce competition for water, sun, and nutrients among trees, thus improve the “health” of the forest. Many of these thinning proposals are, of course, nothing more than timber cutting programs by another name.  There are, however, some thinning advocates who are truly interested in improving forest productivity and reducing big blazes—not in padding the timber industry’s pockets.

Let’s consider why even these proposals may be based upon flawed assumptions. Consider the following points.

POINT 1. Most of the acreage burned in any one year occurs in a relatively few large blazes. In other words if you were to put out all the other fires, these few fires would account for the bulk of all acreage burned. This is important because of point 2.

POINT 2. Big blazes are driven primarily by climatic conditions--when there is extended drought, low humidity, and high winds, you get big fires. The 1910 burn that scorched 3.5 million acres of northern Idaho and western Montana is a good example. More than half of the acreage that burned occurred on Black Friday August 22. That day the winds were roaring across North Idaho and into Montana. This leads to point number 3.

POINT 3. When conditions are ripe for a big blaze, and assuming you have an ignition source (lightning or human), you can’t stop the fires. You just have to get out of the way or are out of the way (i.e. do not build your house in the woods).

POINT 4. As consequence of points 1, 2, 3, thinning proposals as “fuels reduction” have little impact on fire spread. Thinning does work to reduce fire severity (how hot it burns), but little to stop the spread of large blazes. This is because high winds blow burning embers as much as a mile or more ahead of any fire front, starting new blazes. Unless you were to thin all the forests in the West (an impossible task to say the least), you are going to have little effect on fire spread on a landscape scale—though there may be some benefit to surgical thinning in very specific and concentrated areas—more on that below.

POINT 5. There is no predicting where a fire will start and burn. So many things affect fire spread including the wind direction, topography, past fire and insect history which shapes present stand age and species composition, The idea that you can thin forests across the landscape in hope that the areas selected will be the same ones that will likely burn is optimistic at best.

POINT 6. Thinning is not a one time treatment. When you thin a forest you release a lot of other trees from competition which rapidly grow to fill holes in the canopy and understory. Unless you are prepared to go back repeatedly and re-thin the forest over and over again, you lose much of the fuel reduction value. Long before any federal or state agencies could finish with their first generation of thinning, they would need to go back and repeat the thinning process again on the earlier thinning projects. Are there realistically the funds to pay for all this thinning—only if you accept the commercial logging of big trees to pay for it all—and that results in unacceptable impacts to the forest. Logging big trees to pay for the cutting of small trees is really a “Vietnam strategy” of destroying the forest to save the forest.

POINT 7. Thinning is not a proven strategy. Most of the evidence to support thinning is anecdotal—but as many places where advocates claim thinning stopped or slowed a fire, there are other examples where fires burned right through thinned stands.

For instance, much of the forest that was charred in the big Derby Fire in Montana last summer were stands of savanna like ponderosa pine. A similar effect was noted in Oregon’s Biscuit Fire where naturally thin (due to special soil that restricts plant growth) Jeffrey pine stands were scorched. In both of these cases, high winds drove flames across the landscape.

Remember even if thinning appears to work under normal fire conditions, it appears to be less effective under severe fire weather. And it’s very difficult to replicate these conditions in an experiment. No scientist can thin a forest, then create a super drought, low humidity and winds in excess of fifty miles an hour and have it burn both the thinned and adjacent unmanipulated forest stand at the same time.

Thinning, as a fire hazard reduction strategy, could work under less than severe fire conditions, but fail miserably under the high fire severity climatic conditions.

POINT 8. There is even some evidence that suggests that thinning can actually increase the fire severity and intensity because thinning opens up the forests to more wind and permits greater drying of ground vegetation and the fine fuels that sustains fire spread.

POINT 9. Logging is not a benign activity, nor is it the same selective factor as natural events like fire and beetles.  Logging introduces human intrusions into the forest ecosystem. This can disturb sensitive wildlife like wolverine and grizzly bear. Logging can be a vector for the spread of weeds and disease into the forest. Logging almost certainly creates more sedimentation in streams. Logging removes woody debris (dead wood) which has many ecological functions including providing homes for many invertebrates. Logging removes snags, and the potential for future snags—snags are important for many wildlife species, particularly cavity dwellers. Logging can alter nutrient cycles. Logging roads, even closed and “reclaimed” roads, often become new ORVs routes. Furthermore, logging tends to select against early successional species that are favored by fire and beetles, and also skews age classes.

POINT 10. Where thinning may be appropriate is for community protection. I.e. if you thin say within a half mile or less of a community or whatever, AND you can get a big fire fighting force in the area, thinning can sometimes help to slow a fire enough that fire fighters can put it out. However, you have to have a lot of fire fighters on the scene for this to be effective--and the only time you can cost-effectively justify this kind of force is to protect structures. For instance in 1988 in Yellowstone, there were was a massive effort to protect Old Faithful Inn--this worked because you could get hundreds of firefighters in one spot, but you’re not going to get that kind of force to focus on a big fire front that may be miles wide.

POINT 11. Finally, nearly all efforts to reduce big blazes and restore “healthy” forests assume that “healthy” forests are ones with few dead trees and without large fires. This may itself be a flawed assumption. Many ecologists would argue that a “healthy” forest has a good share of dead trees and at some times in the natural course of events, to have a great many dead trees. The same can be said for large fires—large stand replacement blazes may be ecologically important.

The bottom line is that we should seriously question whether we need any manipulation of our forests. I believe the forests are perfectly capable of taking care of themselves. After all they have been operating without our aid for a lot longer than we have even existed. They are used to drought, fires, beetles, and even changing climate. In the face of global climate change, protecting large tracts of unmanipulated landscapes may be the real salvation for our forests.

EDITOR’S NOTE:  As a photographer, George Wuerthner has amassed 250,000 images of wildlands and wildlife on the continent, most of them in the American West, Canada and Alaska.  See some of them at George Wuerthner Photography.

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