The Idaho BLM is implementing what is sometimes called “targeted grazing” with livestock in an effort to reduce large wildfires. The theory is that if livestock graze enough of the “fuel,” then large wildfires like the 600,000-acre Murphy Complex or the Soda Fire which burned across southern Idaho in recent years could be more easily controlled.
On the surface, this strategy seems plausible. Less fuel should mean fewer large fires. But here’s the rest of the story.
First, nearly all the acreage burned annually is the result of a very few large fire complexes. For instance, in the years 1980-2003 there were 56,320 fires in the Rocky Mountain states. Of those fires, 96 percent of the blazes were responsible for charring only 4 percent of the total acreage burned. By contrast, 0.1 percent of the fires — less than 50 — were responsible for over half the acreage burned during that time.
Therefore, the fires that are the biggest threat to both human communities and the ones fuel treatments like targeted grazing seek to control are those very infrequent but large blazes.
However, large blazes occur during what are categorized as “extreme fire weather” conditions. These conditions include serious drought, low humidity, high temperatures and, most importantly, high winds.
The reason winds are key to fire spread is they “fan” the flames, and toss embers 1-4 miles ahead of the fire front, making any attempt at containment impossible. A narrow strip of targeted heavily grazed rangelands is not going to stop a wind-driven blaze since burning embers will easily be blown over any fuel reduction.
Numerous studies of large fires have acknowledged this, including a University of Idaho study, following the 2007 Murphy Complex fire, that burned more than 600,000 acres, which found “much of the Murphy Wildland Fire Complex burned under extreme fuel and weather conditions that likely overshadowed livestock grazing as a factor influencing fire extent and fuel consumption in many areas where these fires burned.”
Another widely cited study done in Arizona heralding the benefits of “targeted grazing” on wildfire reduction concluded that while fuel removal by livestock might reduce fire spread under low and moderate fire weather conditions the situations where it might be beneficial were limited to small areas and under less than extreme fire weather.
The authors concluded, “Targeted grazing treatment did influence fire behavior in grass/shrub communities, but its effects were limited. Although it is a promising tool for altering fire behavior, targeted grazing will be most effective in grass communities under moderate weather conditions.”
In other words, targeted grazing is limited in affecting fire behavior and outcome under the extreme fire conditions agencies like the BLM seek to control.
To have any effect on fuels, the areas targeted for grazing need to be scalped down to stubble. This removes the hiding cover for wildlife, results in soil compaction, serious impacts on native grasses due to “overgrazing” and destruction of soil crusts.
Loss of soil crusts is important because this facilitates the establishment of cheatgrass, a highly flammable annual. So in effect, target grazing often creates a more flammable zone of cheatgrass.
Another issue is the very low probability that a fire will encounter any fuel break. Because the conditions under which a blaze is transformed into a large, unstoppable wildfire are so rare most fuel breaks never encounter a fire, making their implementation a waste of time and money.
Target grazing is like “investing” in the lottery. Yes, you can always point to someone who is a winner, but most people buying lottery tickets are just throwing away their money. It’s the same with “fuel treatments” like targeted grazing.
George Wuerthner is an ecologist, former BLM biologist in Idaho, and has published 38 books. He lives in Bend, Ore.