Synthesis / Tech Report
In October 2017, after a review of the 2015 Federal plans relative to State sage-grouse plans, in accordance with Secretarial Order 3353, the BLM issued a notice of intent to consider whether to amend some, all, or none of the 2015 land use plans. At that time, the BLM requested the USGS to inform this effort through the development of an annotated bibliography of sage-grouse science published since January 2015 and a report that synthesized and outlined the potential management implications of this new science. Development of the annotated bibliography resulted in the identification and summarization of 169 peer-reviewed scientific publications and reports. The USGS then convened an interagency team (hereafter referred to as the “team”) to develop this report that focuses on the primary topics of importance to the ongoing management of sage-grouse and their habitats.
The team developed this report in a three-step process. First, the team identified six primary topic areas for discussion based on the members’ collective knowledge regarding sage-grouse, their habitats, and threats to either or both. Second, the team reviewed all the material in the Annotated Bibliography of Scientific Research on Greater Sage-Grouse Published since January 2015 to identify the science that addressed the topics. Third, team members discussed the science related to each topic, evaluated the consistency of the science with existing knowledge before 2015, and summarized the potential management implications of this science. The six primary topics identified by the team were:
- Multiscale habitat suitability and mapping tools
- Discrete anthropogenic activities
- Diffuse activities
- Fire and invasive species
- Restoration effectiveness
- Population estimation and genetics
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This study evaluated spatio-temporal patterns of fire in piñon and juniper land cover types from the National Gap Analysis Program using Monitoring Trends in Burn Severity (MTBS 2016) data (1984 through 2013) for Northern and Southern Intermountain and Central and Southern Rocky Mountain geographic regions. It also examined differences in total area burned, fire rotation, fire size, fire number, and fire season among: 1) the four geographic regions; 2) the EPA level III ecoregions that occur within each geographic region; and 3) the piñon and juniper land cover types (woodlands, savannas, and shrublands) and other land cover types that occur within each geographic region and level III ecoregion. We found that area burned during the 30-year period, number of fires each year, and fire size followed a strong geographic pattern: Northern Intermountain > Southern Intermountain > Southern Rocky Mountain > Central Rocky Mountain. Area burned within piñon and juniper land cover types increased significantly during the 30-year period across the study area overall and for each geographic region, except the Southern Intermountain.
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Spatial wildfire suppression costs regressions have been re-estimated at a more disaggregated level for the nine Geographic Area Coordination Center (GACC’s) regions using five years of data for fires involving National Forests. Results of these revised regression determined that only in the California GACCs did mechanical fuel treatment reduce wildfire suppression costs. However, the results of our second major hypothesis tests that fuel treatments, by making wildfires less damaging and easier to control, may reduce property damages (i.e., structures—barns, out buildings, etc. and residences lost) seems to be confirmed for acres treated with prescribed burning. In four out of the seven GACC regions prescribed burning lowered the number of structures damaged by wildfire. The results for mechanical fuel treatment were more mixed, with a significant negative effect in reducing property damages in two of the three regions with a significant coefficient on mechanical fuel treatment. These results are consistent with past research that suggests that for fuel treatments to reduce wildfire suppression costs it may be necessary to substantially increase the amount of area treated.
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We examined the effect of livestock grazing and previous wildfire events on fuel load in southeastern Idaho as part of a wildfire risk-livestock interaction study. Fuel load was estimated using ordinal fuel load classes at 128 sample sites stratified by current livestock grazing and documented wildfire occurrence (1939-2000). Fifty-nine percent of previous wildfire sites had a documented fire within the past 2 years. Livestock grazing was the most effective means to reduce fuel load compared to recent wildfire and livestock grazing with previous wildfire. Livestock grazing provides a viable management tool for fuel load reduction prescriptions that avoids the negative effect of extreme fire intensity where fuel load is high.
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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. Differences and abrupt contrast lines in the level of fuels consumed were affected mostly by the plant communities that existed on a site before fire. A few abrupt contrasts in burn severity coincided with apparent differences in grazing patterns of livestock, observed as fence-line contrasts. Fire modeling revealed that grazing in grassland vegetation can reduce surface rate of spread and fire-line intensity to a greater extent than in shrubland types. Under extreme fire conditions (low fuel moisture, high temperatures, and gusty winds), grazing applied at moderate utilization levels has limited or negligible effects on fire behavior. However, when weather and fuel-moisture conditions are less extreme, grazing may reduce the rate of spread and intensity of fires allowing for patchy burns with low levels of fuel consumption.
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Targeted livestock grazing must be carefully implemented and monitored to meet fuels management objectives on an annual and long-term basis. Grazing to reduce fuels on a landscape must be both strategic and surgical. Surgical means that targeted livestock grazing will be done to the level and limited to the minimum area needed to meet fuel and landscape or project management objectives within BLM’s regulatory framework. Therefore, sound project planning is essential.
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Herbivory and fire are natural interacting forces contributing to the maintenance of rangeland ecosystems. Wildfires in the sagebrush dominated ecosystems of the Great Basin are becoming larger and more frequent, and may dramatically alter plant communities and habitat. This synthesis describes what is currently known about the cumulative impacts of historic livestock grazing patterns and short-term effects of livestock grazing on fuels and fire in sagebrush ecosystems. Over years and decades grazing can alter fuel characteristics of ecosystems. On a yearly basis, grazing can reduce
the amount and alter the continuity of fine fuels, potentially changing wildlife fire spread and intensity. However, how grazing-induced fuel alterations affect wildland fire depends on weather conditions and plant community characteristics. As weather conditions become extreme, the influence of grazing on fire behavior is limited, especially in communities dominated by woody plants.
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Cattle grazed a cheatgrass-dominated pasture during the fall dormant period for four years (2006-2009) and were provided a protein nutrient supplement to improve their distribution, uptake of dry feed and production performance. Cheatgrass standing crop was reduced by 43 percent to 80 percent each year, and cattle weight and body condition score increased each year. The fall-grazed site had less cover from cheatgrass than the ungrazed site had. The fall-grazed site also had no decline in perennial grass cover. Cheatgrass density was 64 percent less on the grazed site after two years, and had 19 fewer plants per square foot than the adjacent ungrazed area. The seedbank potential for cheatgrass decreased much more on grazed areas than on the adjacent ungrazed areas, with a 95 percent or greater reduction in the seedbank potential. The difference was due to the grazing treatment.
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Proper grazing management appears urgent in preventing or delaying further encroachment of cheatgrass (Bromus tectorum) into perennial vegetation on western grazing lands and subsequently gaining site dominance. In mixed stands with desirable perennials, livestock grazing might be directed to (1) reducing cheatgrass competition by concentrating grazing of cheatgrass during dough seed stage, providing perennials still have opportunity to complete their life cycles, or (2) basing grazing on the needs of perennials while mostly ignoring cheatgrass. When cheatgrass domination results in a closed community, alternatives appear limited to (1) managing as annual grassland, or (2) revegetation using intensive cultural practices. In conjunction with revegetation, livestock might conceivably be employed for “graze out” in site preparation and I or for selective plant control during germination and emergence of the seeded perennials. However, with these possible limited exceptions, grazing is concluded not to be an effective general tool for cheatgrass control.
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This study found evidence of a gap between risk perceptions of WUI residents and wildfire professionals. On average, residents underestimated the overall risk of their property. One third of the study participants reported having a neighbor that they think is increasing their risk. Perceived likelihood of fire reaching the property and causing damages was positively correlated with perceiving a neighbor is not taking action. The only consistent predictor of defensible space was the level of defensible space on neighboring properties. Our results suggest that programs that are effective in getting single homeowners to mitigate risk may have benefits that spillover to neighboring properties, and risk neutral/tolerant individuals lived on parcels that were rated by the professional as having less defensible space and more ignitable structure materials.