Does Cattle Grazing Preclude Large Blazes?
By George Wuerthner, originally published in The Wildlife News
If cattle graze to bare soil, it is true that fires are slowed under such conditions, but the ecological impacts are enormous. Photo George Wuerthner
When I worked for the BLM, us “ologists” (hydrologists, ecologists, biologists, archaeologists, geologists, and botanists) used to refer to Range Conservationists as Range “Cons” because they conned the public into believing many myths about livestock grazing.
It’s essential to keep in mind that range cons have a financial conflict of interest. If there are no cows, there is no reason to have a range conservationist on the payroll. So, what you will see over and over is that range cons will do just about anything to maintain cows on the range. And they don’t mind spending your (the taxpayer’s) money to make this happen. Most range cons (and range professors) have allegiance to the livestock industry, not the public interest.
One of the “cons” heard continuously from range conservationists and repeated by uninformed media is that grazing can help preclude large “mega” fires by “reducing” fuels. This is one of those many assertions that have a grain of truth but are nevertheless misleading.
Experimental vs. Landscape Scale of Results
In an overview of various fuel reductions, the researchers (Reinhard et al. 2008) concluded that: “Extreme environmental conditions …overwhelmed most fuel treatment effects….This included almost all treatment methods including prescribed burning and thinning….Suppression efforts had little benefit from fuel modifications.”
Although they primarily examined forest management options, the same necessary conclusions apply to reducing fuels on rangelands (Williamson, Matt. A. et al., 2019)
Windblown fire races through grazed grasslands near Helena, Montana. Photo George Wuerthner
Other evidence is simply anecdotal. Cattle graze a strip of cheatgrass. A fire arrives, and the fire slows or is easily suppressed by firefighters. An example is here found with the title Firefighting Cattle: Targeted grazing creates firebreaks in cheatgrass.
Without knowing the circumstances of the fire’s burn and weather conditions at the time, one can’t assume that grazing had anything to do with the fire’s behavior. Did the wind shift directions or simply stop? Was the fire even burning under the “extreme conditions” that are the only conditions under which large fires burn--the very fires that cattle grazing advocates suggest can be halted or slowed by grazing?
Typically, under extreme weather conditions--which always include high winds--any wind-blown fire will project embers up to a mile or more beyond the burning front. Such a blaze will easily skip over a strip of grazed land, making such fuel breaks, and the targeted grazing that created them, ineffective.
Whenever you read such pronouncements, be skeptical. Almost all the “evidence” for the value of grazing to reduce wildfires comes from government apologists with connections to the livestock industry.
Many of the studies purporting to demonstrate the influence of livestock grazing on fire spread were done on small experimental plots of land. The transfer of these findings to the larger landscape scale is questionable.
For instance, in an experimental study of cattle grazing impacts on fire, 90% of cheatgrass in plots was consumed during the “boot” stage. These grazed plots were then burned and found to slow or stop fire spread (Bailey, Derek W., et al. 2019). The problem with this and many other experiments is that given a choice, livestock will not consume cheatgrass except early in the spring while green. So, getting cattle to remove 80-90% of the grass except in experimental plots is unlikely.
Another problem is keeping cattle on the desired target area–typically this is done by transporting cattle by truck to the target site, then herding or using moveable fences to keep cattle grazing focused. All of this adds immensely to the cost of any livestock grazing operation. Most ranchers are simply not interested in spending that kind of money to get a bit of cheap forage.
Furthermore, the process of getting the cattle to remove such a high percentage of cheatgrass would decimate soil biocrusts, which slow or prevent cheatgrass establishment. Since cattle prefer to forage on native perennial grasses, if a site had any native species left, they would disproportionately be grazed, harming their competitive ability to survive cheatgrass invasion (Reisner, Michael D., et al., 2013).
In another widely cited study in Arizona, the researchers had several small plots of several acres in size. They compared the fuel remaining after fields were grazed with non-grazed plots. They used modeling (the BehavePlus fire model) to conclude that with light utilization of 26% in treated sites, herding reduced fire rate of spread by more than 60% in grass communities and by more than 50% in grass/shrub communities (R.A. Bruegger et al. 2016).
There are several misleading implications of this study. As in the previous study, the experiment was done on small plots where grazing was monitored and tightly controlled. This kind of monitoring and control does not exist on most public lands or even on private land parcels.
But the real problem with this and many other studies that presume to show a livestock grazing-induced reduction in fire spread is that they do not work under extreme fire weather.
Bruegger and colleagues admit as much in their next to last paragraph: “Although it is a promising tool for altering fire behavior, targeted grazing will be most effective in grass communities under moderate weather conditions.”
The weather factors are significant because nearly all massive wildfires burn under extreme fire weather conditions. Under such conditions, targeted grazing, prescribed burning, thinning of forests, and fuel breaks all fail to contain or stop fires. In attempting to reduce fuels, such prescriptions often lead to more fire-prone species like cheatgrass.
Extreme fire weather conditions--drought, high temperatures, low humidity, and most importantly, high winds--overwhelm all fuel reductions. The problem for Americans is that climate change, not fuels, is driving large blazes.
Severe Grazing and Collateral Damage
Severe grazing can reduce fuels that would allow fires to spread. Still, grazing to this level creates significant collateral damage--including soil compaction, which reduces water infiltration (Warren, S.D. et al., 1986, Belsky et al. 1999), social displacement of native herbivores like elk and deer (Clegg 2014, Frisina 1992), water pollution (Carter, 2002), destruction of riparian areas (the green line of vegetation influenced by water) (Kauffman et al 2001, Kauffman 2004), consumption of plants needed by other wildlife like the forbs consumed by sage grouse (Doherty et al. 2014), and reduction of hiding cover for wildlife, along with many other impacts (Fleischner 1994, Freilich et al., 2003).
It is important to note that much of the grassland/shrub ecosystems of the western United States west of the Great Plains evolved in the absence of large herds of grazing herbivores like bison (Mack and Thompson 1982), thus are vulnerable to heavy grazing pressure.
Alternatively, and far more critical these days, livestock grazing is one factor in the spread of cheatgrass, an annual exotic that is extremely flammable (Belsky, A.J. and J. L. Gelbard, 2000). Merriam et al. (2006) found that nonnative plant abundance was considerably higher on fuel breaks than in adjacent wildland areas, especially when heavy ground disturbance provided a potential vector for weed invasion.
Collateral damage from livestock grazing includes cattle damage to riparian zones
(the green vegetation area near water). Photo George Wuerthner
Therefore, cheatgrass has increased fire frequency in sagebrush ecosystems, causing complete type conversion of sagebrush steppe in many areas (Reisner Michael D. et al. 2013).
The factors that favor cheatgrass spread include livestock grazing as selective grazing of preferred perennial grasses reduces their competitive ability, permitting cheatgrass colonization (Maestas et al. 2019)
Additionally, biological soil crusts (BSC) found in the interspaces between bunchgrasses inhibit cheatgrass establishment. Cattle trample these BSC (Root, Miller, and Rosentreter. 2019).
Cheatgrass surrounds a relict perennial native grass. Photo George Wuerthner
Biological crust covers the surface of soil. Cattle trampling crusts creates habitat for cheatgrass establishment. Photo George Wuerthner
Maintaining healthy stands of perennial grasses has been shown to inhibit cheatgrass spread (Strand et al., 2017).
Another study that looked at fuel breaks created by targeted grazing and other measures like bulldozing native vegetation cautioned that the “cure might be worse than the disease,” in reference to the destruction of soil biological crusts and loss of native grasses. Other fuel reductions create a disturbance habitat that favors the spread of cheatgrass.
The authors cautioned: “these projects could also add thousands of kilometers of new fuel breaks to the region over the next decade or two, directly altering hundreds of thousands of hectares through habitat conversion, and indirectly affecting sagebrush plant and animal communities through the creation of new edge effects and habitat fragmentation” (Shinneman et al. 2018).
Furthermore, the probability that any area “treated” by targeted grazing and other fuel reductions will encounter a blaze when fuel removal is effective is extremely small (Rhodes and Baker 2008). Thus, targeted grazing and further fuel reductions are generating their own set of impacts, frequently for no reason at all.
Fuel break on BLM land creates the ideal habitat for cheatgrass establishment. Photo George Wuerthner
Using livestock grazing to preclude large wildfires is an ineffective means of coping with blazes. Livestock grazing has little influence on large-scale blazes, which are primarily driven by extreme climate/weather events. The probability that a large fire will encounter a recently grazed area is small, but livestock grazing’s ecological impacts are enormous and assured. The best way to reduce wildfire’s threat is to fire-safe human dwellings and ultimately reduce global climate warming, which is the main driver for many of the largest blazes experienced in the West.
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