In a recent review article about forest thinning and its effectiveness to reduce wildfire severity and spread in Forest Ecology and Management, the researchers came to a conclusion with regards to reducing fire risk and effects that “thinning alone had either less of an effect or none at all, compared to untreated sites.”

The study did conclude that thinning followed by at least one, (but better two) prescribed burn treatments is generally effective at reducing fire risk. And if you can only do one thing, prescribed burning is more cost-effective at reducing fires than thinning/logging alone. However, both the Forest Service and Bureau of Land Management tend to spend far more money and effort on logging the forest than on prescribed burning.

There are a host of reasons for this. There is strong pressure from the timber industry on the federal government to provide more subsidized timber sales on federal lands. Plus, due to the lack of transparencies on the part of the Forest Service and other agencies, you seldom hear anyone admitting that thinning/logging has been proven to be largely ineffective at reducing fire risks.

Plus, most thinning/logging operations have other collateral damage like soil compaction, disturbance of wildlife, the spread of weeds and road construction, which fragments forests and causes sedimentation of streams. These are the “externalized costs” of logging that are seldom counted in the “cost”/benefit of a timber sale.

Even without considering these externalized costs, most federal timber sales lose money — another fact that the federals are loath to admit or try to justify by claiming that logging will reduce wildfire risk. But as this and other recent studies conclude, thinning alone is rarely effective in accomplishing this goal.

The effects of fuel reduction are usually negated in three to 10 years by new growth of fine fuels — fallen needles, shrubs, small trees and so forth. And while there’s money for logging/thinning, there’s less available to do the maintenance. So even if effective immediately after treatment, the effectiveness declines rapidly.

However, even if federal agencies shifted emphasis to more burning than logging, the other unacknowledged fact is that all fuel treatments, while they may work occasionally to slow or control blazes under moderate fire weather conditions, usually won’t stop the large fires burning under severe fire weather that are the real threat to western communities.

Severe fire weather conditions include drought, high temperatures, low humidity and, most importantly, high winds. If you have high winds, you cannot effectively control a blaze.

Ironically, most fires burning under low to moderate fire weather conditions will self-extinguish or are easily controlled. However, under severe fire weather, nothing works. Thinning and prescribed burning usually fail to alter the outcome for the largest fires burning under severe fire weather.

Also, most forests burning at high severity are higher elevation, moister forests types like lodgepole pine, spruce or fir that have very long fire return intervals, and it may be decades or even centuries before they burn, making any fuel reductions useless since trees would grow back before any fire encounters the fuel reductions.

Plus, large high-severity fires are critical to healthy forest ecosystems. Severe fires provide a major input of woody debris that maintains spawning beds for salmon and trout. They provide structural components (snags) that are valuable for birds and mammals for feeding and homes (cavities). Burned forests also store carbon and nutrients. Ecologically speaking, thinning impoverishes our forest ecosystems, while large wildfires enrich them.

Of course, no one wants to see a home or community threatened by wildfire, but we don’t have to destroy our forest ecosystems with logging to protect our homes. Don’t build any new homes in the “fire plain” on the edge of town.

For those homes already constructed in the wrong places, reducing the flammability of homes is proven highly effective. Metal roofs, screened roof vents, removal of flammable materials around the base of the house and building a modest wall that can keep surface fires from burning to the edge of a home, are only a few of the proven methods that can save a home from wildfire.

And yes, even some moderate thinning and prescribed burning immediately adjacent to the home and on the edge of the community can be useful — but only if these fuel treatments are regularly maintained and strategically done.

The idea that you can preclude large wildfires through forest-wide thinning is snake oil, very expensive snake oil. And not only does the taxpayer pay for ineffective fire protection, but we degrade our forest ecosystems in the process. — George Wuerthner