Fire season in Montana can be an intense experience, especially if it is a very active one like this year. The wildfires dominate the local news, and the announcements of evacuations scroll across the television screen all evening. Even in Missoula, a mid-size town where we are safe from the fires themselves, we have to endure the thick layers of smoke, which constantly irritates the eyes and casts a dirty-yellow light over everything. There’s no better way to keep an issue literally "in your face."
Fire is a truly terrifying phenomenon. These big forest fires can burn with a speed and intensity that is overwhelming. Check out the video in this diary to get some idea. A lot of people around here either know someone who has fought fire, or know someone who has had to evacuate their home. It is understandable that emotions can get a little raw. Unfortunately, those emotions can be exploited, by people who really want there to be simple solutions, and someone to blame.
So how do environmentalists get blamed for this?
The first part of the story comes from the forest scientists themselves (it is still the official paradigm), so it has a lot of credibility and is, in fact, partially true: In the dry forests of the inland West, frequent surface fires used to clear out the understory debris and fine fuels without killing the large trees (mature ponderosa pines and larches are extremely fire-resistant). Decades of fire suppression have prevented this natural "clean-up" process and allowed brush and small trees to accumulate in these forests, so that now fires will burn hotter and climb up these "fuel ladders" into the canopy, resulting in high-severity crown fires where they would not have otherwise occurred.
This "unnatural fuel buildup" claim has been seized on by timber interests, politicians, and a well-meaning but fearful public to spread the idea that ALL high-severity crown fires are unnatural, that they never used to happen, and that they can and must be prevented at all costs. And they have a simple solution: if only we could thin out all these forests, everything would get back to "normal" and we would be safe from fires. And any one who gets in the way of this solution is causing the horrors that plague us.
And thus was born the Healthy Forest Initiative. Written by the timber industry and lapped up by the Bush Administration. There are a lot of problems with this initiative and the Healthy Forests Restoration Actthat came out of it. One of the worst is the attempt to bypass public involvement. But as a biologist, I want to concentrate here on two of the biological assumptions:
- Are forest fires more intense than they used to be?
- Does mechanical thinning (logging) reduce the intensity of fires?
Let’s take these one at a time:
Are forest fires more intense than they used to be?
The extent, and perhaps the average intensity, of forest fires have indeed increased in the last couple of decades (although the graphs that show this are usually national in scope and often include grassland and shrubland fires, which greatly complicates the discussion). But the acreage burned is dependent on weather and the number of ignitions as well as fuels, so the cause of the increase is not necessarily clear. There may well be more fuels in some places, but there are also more human ignition sources, and most importantly, the forests are much, much drier than they have been at any time since such records were kept. We don’t really know if this is due to global warming, since there have always been severe drought cycles and consequent fires in past centuries, but it could be an indication of severe problems ahead.
Huge fire years clearly took place in previous centuries
The pro-thinning lobby is fond of agreeing that fire is natural but "not the kind of fires we have now." That "monster" fires are both unnatural and "catastrophic." This is nonsense. We can see from tree-ring studies that there were in fact widespread fires during drought cycles in previous centuries, but we don’t have to go back that far to prove this claim ridiculous: All we have to say is "1910." And it’s not like 1910 is an obscure reference around here; the Great Burn of 1910 is legendary, ingrained in the mind of anyone who knows anything about forests and fire in the inland Northwest. These people know very well that the kind of conflagration we are seeing now happened in the past, before fire suppression became effective. In fact, 1910 was the event that drove the modern era of fire suppression.
Different forest types have different fire regimes
Almost all forests burn eventually, but most forests only do so every 100-300 years, on average. This is because they are usually too moist to carry fires very far or because they grow and build up fuels very slowly (so basically in areas of higher rainfall or higher elevation). Fires in these areas are almost always high-severity crown fires, because so much fuel has build up since the last fire, and because they only burn in years when they are super-dry. In these areas, fire suppression could not have altered the fire regime, because it simply hasn’t been happening for long enough. For example, every indication is that the 1988 Yellowstone fires that helped start the modern debate were a completely natural event, having happened about every 300 years for millennia.
All forest biologists and managers understand this, but the debate is about how much of the total forest area is "out of whack." Estimates range widely around a ballpark figure of about 10%. But the proponents of Healthy Forests (including President Bush) still claim that "over 190 million acres" of forests need treatment. Where do they get this number? Because there are 193 million acres in the entire National Forest system(and that includes National Grasslands). In other words. they want it all.
Even in the lower elevations, crown fire sometimes occurred.
Recent studies have been making it clear that lower elevation ponderosa pine forests did in fact have some significant amount of mixed-severity fire, so at least some crown-fire events are perfectly natural. Even if the acreages over which crown fires are greater now than in the historic past, that is not to say that the presence of crown fires in these dry forests represents a process that is unnatural; severe fires are clearly natural in all forest types.
Current fires are made to sound bigger than they really are.
The huge acreages listed for fires in the news refer to all of the land within the outside perimeter of the fire complex. But not all of this area is actually burned. For example, the largest 2002 fire (the same Biscuit fire that Bush used as a backdrop to announce his Initiative) was listed around 500,000 acres, but only about 16% of that area burned severely, 23% moderately (not all trees killed), about 41% lightly (no crown fire) and 20% was essentially untouched. Other large fires usually have similar numbers. This mosaic of forest disturbance is more or less the way forests have always burned.
Burned forests have their own unique ecosystem
Another clue to the "naturalness" of severely burned forests is that they result in unique ecosystems, with animal and plant species that are not as abundant anywhere else. Some of these species are even relatively narrowly restricted in their habitat distributions to, and presumably relatively dependent upon, burned forest conditions. In our research group we study fire-dependent birds, especially the Black-backed Woodpecker, which is highly specialized on severely-burned forest. My boss told this story well in an in our local paper. The dramatic positive response of so many plant and animal species to severe fire and the absence of such responses to low-severity fire in conifer forests throughout the West argue strongly against the idea that severe fires are unnatural; the biological uniqueness associated with severe fires could emerge only from a long evolutionary history between a severe fire environment and the organisms that have become relatively restricted in distribution to such fires.
Does mechanical thinning (logging) reduce the intensity of fires?
Whether or not thinning actually reduces fire danger is not entirely clear. Some studies show it doing so, and some studies show it doing the opposite. Still, all else being equal, removal of all small fuels will probably lower the probability of intense fire. Most experts therefore agree that thinning in the"wildland-urban interface" is probably a good idea. In fact, the most important thing determining whether a home will burn is the fine fuels within 100 feet. Unfortunately, the Healthy Forests Restoration Actwill spend only half of the funding in this Community Protection Zone.
But there is a right way and a wrong way to thin forests for fire reduction:
The problem, everyone agrees, is the build-up of small fuels in the understory, including small trees that have grown up during the last few decades of fire suppression. So this is what needs to be cleared out. But none of that material can be sold, so larger trees are usually taken for economic reasons (the Forest Service because they don’t have any money to do it otherwise, and the timber industry because that was what they wanted in the first place).
Removal of larger trees may actually increase the likelihood of burning.
Logging the large trees not only disrupts the ecology of the forest for virtually no gain in fire suppression, but there are some studies showing that such logging can increase the probability of fire. This is because it exposes the understory to increased drying from wind and sun, and it also allows wind to circulate more and whip up any fires that might occur. Also, if the area is not cleaned up well after the logging (which is more expensive), it is possible to leave more slash and fine fuels lying around than were there in the first place.
Fire intensity and annual area burned is mostly determined by weather.
Fuels may affect how hot a fire burns in some years, but big fires only occur in dry years, and then everything is so dry that the fires will burn through everything, regardless of the amount of fuel. This points to what may be the most important lesson of all in this debate:
You can’t fireproof forests.
Most of the journal articles I used for background are on subscription sites but the scientific view of fire ecology is summarized in a scientific summary and policy statements published by the Ecological Society of America and the Society for Conservation Biology, and many other online resources