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Livestock Grazing in the Western United States: Challenges and Opportunities

Written by Adrian Monroe, 2015-2016 Sustainability Leadership Fellow and Research Scientist at the Natural Resource Ecology Laboratory

Livestock grazing—a widespread land use across the Western United States—can have important consequences for ecosystems and their animal inhabitants.  Among such sensitive ecosystems are sagebrush-dominated (Artemisia spp.) communities, whose plant species did not co-evolve with the heavy grazing pressure that can exist today.  This has led to conflicts between some scientists and environmentalists who have called for the removal of livestock from these ecosystems, and ranchers whose families have managed livestock on these lands for generations [1].  Although studies have documented the effects of heavy grazing on these plant communities in individual study sites, little is known about the broad scale implications of grazing across this vast landscape.

In sagebrush ecosystems, populations of greater sage-grouse (Centrocercus urophasianus) have declined substantially over the previous half-century [2, 3].  Grazing may affect sage-grouse populations because herbaceous cover provides concealment for nests and food for broods [4, 5]. Recommendations typically call for reductions or delays in grazing to avoid impacting vegetation for nesting sage-grouse, but much of what we know about how grazing affects sage-grouse come indirectly from fine-scale habitat studies [6]. Studies attempting to directly test effects of grazing on sage-grouse are extremely challenging because sage-grouse, a “landscape” species, require an enormous area during their life cycle.  But, there could be conditions where livestock grazing is compatible with species such as sage-grouse, and studies are needed to identify these conditions to better inform management and policy.

How could grazing be compatible with sage-grouse, you may ask? After all, herbaceous cover can increase the likelihood of sage-grouse successfully hatching and raising chicks, and livestock remove herbaceous cover through grazing, so it intuitively makes sense that removing livestock should benefit sage-grouse. However, there is reason to suspect this may be overly simplistic and does not consider the complexity of these systems. For example, sage-grouse need forbs to raise their broods [4] and forb cover can increase brood survival [7]. At moderate rates, grazing can increase the variability in structure and composition of rangelands [8], and therefore reductions in grazing could have a negative effect on sage-grouse if this reduces forb cover.  Furthermore, recent studies have shown that using heavy grazing to characterize impacts may actually be a false comparison, and that well-managed grazing regimes can have equivalent or better outcomes compared to ungrazed pastures [e.g., 9].

After the previous summary, one would be forgiven for thinking this is all too uncertain for making decisions that could affect the fate of species and the livelihood of ranchers.  But there is reason for hope that more answers will be available in the coming years.  For one, our lab is developing the use of public grazing records to characterize livestock grazing at large spatial scales.  Much of the land in the Western U.S. is publicly-owned, and agencies such as the Department of the Interior-Bureau of Land Management maintain records on the timing and intensity of grazing on the grazing allotments that they administer.  When we pair this with long-term monitoring of sage-grouse through annual counts of males at breeding display sites (leks), we have the opportunity to investigate for responses of sage-grouse to grazing at an unprecedented scale.  At the same time, studies are being conducted to experimentally test the effects of grazing on sage-grouse (e.g., https://idahogrousegrazing.wordpress.com/current-project-status/), which should directly relate the response of vegetation to grazing at multiple scales, and subsequent sage-grouse responses.  Results from these and other studies will help agencies and land managers consider potential impacts to sage-grouse when prescribing grazing amounts and timing, and hopefully ensure the continued coexistence of this species with modern ranching operations across the West.

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