Livestock Grazing's Contribution to Fire Hazard

In recent years, historic blazes have scorched much of the West.  Congress has reacted by creating a National Fire Plan, which attempts to address some of the factors contributing to the increasing costs of fire fighting as well as loss of life and property.  The plan includes funds for increased fire-fighting capacity, home-owner education, and prescribed burning to reduce flammable fuels.  However, as is always the case, the contribution of livestock grazing to fire hazard is overlooked, and the practice continues unabated on public and private lands throughout the West.  While climatic conditions like extreme drought and high winds are key factors in any large blaze, management practices-including logging, fire suppression, and livestock grazing-have exacerbated the situation by creating densely stocked timber stands and weedy grasslands and deserts that render them more vulnerable to high intensity fires.

No grazing means more grass; regular, low intensity fires; large, evenly spaced trees; no sapling thickets; and no weeds.  A healthy forest.

Historically, low elevation western forests were renewed by frequent, low intensity fires-although high intensity fires may have always existed, even prior to the intervention of European Americans.  Young seedlings and saplings of common tree species like juniper and ponderosa pine are extremely vulnerable to even moderate levels of heat.  As a consequence, low intensity blazes tended to thin forest stands to create open timber stands dominated by a few widely spaced, large trees.

Livestock grazing is usually ignored by land managers as an important factor in changing forest stand conditions and fire regimes.  There is a substantial body of scientific literature that identifies livestock grazing as a major factor in the alteration of historic fire regimes and fire hazard.

First, livestock grazing removes grasses that compete with tree seedlings for water and nutrients.  This favors the establishment of deep rooted trees and allows them to dominate a site.  Study sites in several ponderosa pine dominated ecosystems have found that, in the absence of both fire and livestock grazing, ponderosa pine forests are lush and open with few thickets of young trees.  The reason is that existing grass cover cloaks the forest floor and prevents pine seedlings from establishing by outcompeting them for soil moisture.

Second, most tree species require bare soil for successful germination.  By removing the grassy understory of many forest sites and creating the bare, disturbed soil sites that favor tree establishment, heavy grazing has led to greater tree density.

Third, grazing removes fine fuels, such as grasses, that historically helped carry light intensity fires that once burned at regular intervals throughout lower elevation forest ecosystems in the West.  This has allowed young saplings to become established, often in "dog-hair" thickets within forest stands.

Fourth, by permitting a large number of small saplings to become established, competition for water among existing living trees is increased-making trees more vulnerable to insects and other pathogens.  Under extreme drought conditions, such trees are actually more flammable than dead trees.  Internal water content is often less than kiln-dried lumber, and due to the flammable resins found in living trees, such drought-stressed trees often explode into flames upon contact with fire.

Fifth, by contributing to the spread and persistence of fire-loving, weedy species like cheatgrass, livestock production has created highly flammable plant communities in forests and especially sagebrush landscapes in the West.  Fires have become more frequent, more intense, and larger than nature intended for these habitats since the introduction of livestock and weeds 150 years ago.

Despite its contribution to the on-going and growing fire hazard in the West, livestock grazing on public lands continues unabated and is seldom altered to reduce the incidence or intensity of western fires.

Text by George Wuerthner; edited by Mark Salvo.  This article was originally published with references by George Wuerthner in "Desert Ramblings", the newsletter of the Oregon Natural Desert Association Click here for a PDF copy of the article.