Fire Patterns in the Range of the Greater Sage-Grouse, 1984-2013
OAKHURST, Calif. -- Overall fire threats to greater sage-grouse habitat are much higher in the western part of the species’ range than in the eastern part, according to a U.S. Geological Survey fire threats assessment study published today.
The USGS report provides a scientific assessment of a 30-year-period of comprehensive fire data (1984-2013) across sage-grouse management zones (see map) and vegetation types that include sagebrush as a major component. Researchers evaluated the implications of these findings for conservation and management of the greater sage-grouse in wildland areas across the species’ range.
The greater sage-grouse’s range is split up into seven management zones. The four western zones are distinguished from the three eastern zones due to differences in rainfall and vegetation, which affect fire regimes. Overall, the results indicate that fire threats are higher in the four western zones than in the three eastern management ones.
Fires have the potential to degrade habitat conditions for the greater sage-grouse, and there isevidence that fire is becoming increasingly more prevalent in the western United States, in many cases associated with the spread of invasive annual grasses.
“During recent decades, fire area and fire size have increased across large portions of the western zones, hindering recovery of sagebrush and threatening sage-grouse habitat,” said lead author Matthew Brooks, a USGS fire expert and research scientist at the USGS Western Ecological Research Center. “In contrast, parts of the eastern zones were less impacted by fire, and may actually have less fire than historically occurred.”
Sage-grouse rely on sagebrush habitat for food and breeding. This research focused specifically on sage-grouse habitat within sage-grouse population areas across the species’ 11-state range so that the research could best inform sage-grouse conservation and management efforts.
For example, noted Brooks, the fire history, vegetation type and soil moisture data developed in this study can be combined with other data to create science-based potential risk assessment maps for the establishment of a grass/fire cycle or habitat degradation information for the greater sage-grouse. “Also,” he added, “in light of these findings, it may be useful for managers to reconsider the relative importance of wildfire as a threat to greater sage-grouse in the eastern management zones.”
- Among the four western management zones, the Snake River Plain and the Columbia Basin ranked slightly higher than the Southern Great Basin and Northern Great Basin in terms of fire effects on sage-grouse habitat. These results support the previous high ranking of fire as a threat to the greater sage-grouse in the western region.
- The eastern zones were less impacted by fire, and may actually have less fire than historically occurred, especially in the Grassland vegetation type.
- Among the vegetation types with a dominant sagebrush component, Big Sagebrush accounted for 56 percent of vegetation burned in the 30 years examined, Black/Low Sagebrush 14 percent, Grassland 10 percent, Desert Mixed Scrub 4 percent, Mountain Brush 1 percent, and Floodplain less than1 percent. Non-Sagebrush accounted for 15 percent of the area burned.
- Increasing trends in percentage of fires in larger fire size classes were noted in the western management zones, but not in the eastern zones.
- Recurrent fire area (burning 2 or more times) encompassed 22 percent of the total fire area in the western region, most of which was in the Snake River Plain and in the Big Sagebrush vegetation type. Although the smallest amount of recurrent fire area was in the Columbia Basin, it represented 34 percent of the total fire area in that management zone.
- Fire rotation estimates were generally lower than published estimates of historical conditions for Big Sagebrush and Black/Low Sagebrush in the western management zones. In contrast, Big Sagebrush fire rotations were generally higher than historical estimates in the eastern management zone.
- The length of the fire season was fairly constant during the 30-year study period for all except the Southern Great Basin, Great Plains, and Wyoming Basin, which displayed significantly increasing trend towards longer fire seasons.
- Big Sagebrush, Black/Low Sagebrush and Desert Mixed Scrub are comprised mostly of areas that have low resilience to fire and recover slowly. Non-native annual grasses often grow back in these areas, which in turn increase fire size and frequency, decreasing suitable habitat for the greater sage-grouse.
- Floodplain, Grassland, and Mountain Brush are mostly in areas of relatively high resilience and resistance to non-native annual grasses.
This research, Fire patterns in the range of greater sage-grouse, 1984–2013—Implications for conservation and management,was authored by M.L. Brooks, J.R. Matchett, D.J. Shinneman, and P.S. Coates, all of USGS. U.S. Geological Survey Open-File Report 2015-1167.
About Greater Sage-Grouse
Greater sage-grouse occur in parts of 11 U.S. states and 2 Canadian provinces in western North America. The U.S. Fish and Wildlife Service is formally reviewing the status of greater sage-grouse to determine if the species is warranted for listing under the Endangered Species Act.