In a recent review article about forest thinning and its effectiveness to reduce wildfire severity and spread in Forest Ecology and Management, researchers concluded that on reducing fire risk “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.
Ironically, the Forest Service emphasizes logging/thinning over burning. But there are other reasons to question the entire fuels reduction program.
First, logging is not benign. Most thinning/logging operations have other collateral damage like soil compaction, disturbance of wildlife, the spread of weeds, 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.
Fuel reduction are usually negated in 3-10 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, that effectiveness declines rapidly.
Century-long fire cycles
Most forest types like lodgepole pine/spruce/fir (which makes up the bulk of the annual acreage of forest burned) have long intervals — often a hundred years or more — between blazes. So the probability that any fire will actually encounter a fuel reduction in the time when it’s effective is exceedingly small.
However, 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.
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.
Plus, large high severity fires are critical to healthy forest ecosystems. Severe fires provide woody debris that maintains spawning beds for salmon and trout. They provide 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.
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, 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.
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.