The Sage Grouse Initiative has released new research highlighting the importance of habitats with a moderate supply of moisture for sage-grouse and other wildlife species.
The sagebrush range in western North America has a semi-arid climate, which means vegetation productivity is limited by occasional drought. Habitats that contain a moderate or balanced amount of moisture are termed “mesic.” These habitats help sustain wildlife by providing the last bits of green areas during dry and hot summer months.
Depending on the annual climate variations, sage-grouse numbers fluctuate. Populations are usually the highest during wet years, when more landscape is green and provides easily-accessible food like insects for chicks. During dry or drought years, sage-grouse hens and their chicks must travel long distances in search of mesic areas, resulting in the death of many chicks.
The Sage Grouse Initiative report stressed the importance of conserving diverse mesic habitats to give sage-grouse and other wildlife species options during low and high moisture years.
Researchers compiled more than 15,000 satellite images from 1984 to 2016 to review annual vegetation productivity across the sagebrush biome. Rangeland productivity during mid-July to mid-September was the focus because ecosystems are the driest during this period and sage-grouse concentrate in the mesic areas.
Productivity patterns were then linked to annual variations in climate. The resulting mesic areas were categorized into irrigated alfalfa, rangeland, riparian areas, or wet meadows. Data was then combined with land tenure information to evaluate proportional mesic resource abundance by ownership within three western regions: the Great Basin; Rocky Mountains; and Great Plains, the report read.
The results of the research showed that sage-grouse populations are structured partly by drought sensitivity—the areas with the lowest mesic availability supported the fewest birds. The Rocky Mountains showed the highest density of mesic resources, as well as the highest number of sage-grouse.
Mesic resources differed between the three regions, despite similar average annual precipitation, the report read. Topography and timing of rain and snow are key factors in mesic resource variation. Mesic productivity in the Great Plains is up to one-third more sensitive to precipitation than similar habitats in the Rocky Mountains or Great Basin.
Privately-owned land contains 68 percent of all mesic resources in sagebrush county, even though private lands comprise just 40 percent of the total land area. Patterns of ownership between regions vary depending on mesic habitat. In the Great Basin, 87 percent of wet meadows are found on private lands compared to 66 percent of productive mesic rangeland on public lands.
Nesting sage-grouse in the Great Basin position themselves in a mid-elevation habitat during the spring to increase their odds—they can then either move down into the wetlands or up to find mesic areas, depending on the summer conditions. This allows the birds to minimize chances of predation as well as energy output by nesting between the two mesic habitat types. This has been coined the “Goldilocks Zone” by researchers, the report read.
This research analysis has provided a new vat of information for where to invest in mesic resource conservation. The report read that the USDA Natural Resources Conservation Service offers technical and financial assistance for mesic conservation that improves or maintains wet meadows and riparian areas. On adjacent upper-elevation sagebrush rangelands more likely to be public land, the BLM can remove conifers to increase water availability and forage quality.
Joining together to conserve mesic resources across public and private lands can open up more habitat for sage-grouse to move between seasonal habitats and safely raise their young, the report continued. This conservation approach could ensure Western rangelands are resilient for wildlife and livestock long into the future, the report concluded. — Anna Miller,WLJcorrespondent
