A new study looks at how umbrella species protect other species in southwest Montana
By Benjamin Alva Polley EBS COLUMNIST
Published in the esteemed Journal of Applied Ecology, a 2024 paper by researcher Elise Zarri and Bureau of Land Management biologist Katie Benzel sheds light on how managing conifer trees to enhance sage grouse habitat inadvertently aids numerous species, such as songbirds, in the sagebrush country of southwest Montana. These findings are crucial for understanding the complex interplay of species in our ecosystems.
Zarri and Benzel found that the more closely non-target species’ habitat overlaps with target species, such as sage grouse, the more benefits other species reap. Sage grouse and many other species rely on healthy sagebrush habitat.
Habitat managers refer to “umbrella species” as an important concept for habitat overlap.
Ecologists first proposed the concept of umbrella species as a way to manage ecosystems and protect the needs of many species by focusing on protecting the needs of just one species—this species’ needs encapsulate many others, like an overarching umbrella. This strategy simplifies management and monitoring efforts, helping conservationists create a more significant influence with fewer resources. Ecosystems are very complex, so focusing on just a few species can make conservation planning more practical.
This strategy, exemplified by removing conifers to benefit sage grouse, is a powerful tool in conservation. It provides hope for the many other species shaded by that umbrella, like songbirds or larger mammals like mule deer and pronghorn antelope.
Sage grouse are game animals managed by states for hunting. They are used as an umbrella or indicator species because game managers have been studying them for years. Their numbers have declined for years, and researchers are honing the reasons for this. Hunting limits and bans will be placed if their numbers fall too low.
The BLM’s interest in funding this research project was piqued by the potential benefits it could bring to their conservation efforts. This promising study opens up new possibilities for enhancing biodiversity in southwest Montana.
Elise Zarri also worked closely with The Nature Conservancy, a key player in the partnership, to lead the way in this vital research. In 2017 and 2018, the Southwest Montana Sagebrush Partnership, a collaborative effort that includes BLM lands, state of Montana lands and private ranching lands, identified several areas for the mechanical removal of conifers.
Annually, the BLM’s Dillon Field Office removes conifers from encroaching into grasslands and sagebrush habitats to help save sage grouse and their necessary biome. The goal is to prevent grasslands from turning into forests because once grasslands surpass the threshold, the sagebrush becomes more arduous to re-establish. Getting that habitat back takes lots of planning, funding, human power and time.
The study’s process and findings
Zarri and Benzel’s study aimed explicitly to see how songbirds respond to conifer expansion into grassland habitats and how conifer removal benefits or impacts ground-dwelling songbirds. Their research spanned four summers in the Medicine Lodge area of southwest Montana.
Songbirds are generally abundant and wide-ranging, so it was easy for the seven researchers to compare each songbird’s population and reproductive successes in areas where conifer removal had occurred and where it had not.
Brewer’s sparrow and sage thrasher are considered “sensitive species” on BLM’s special status species list, which is used for special management considerations to reduce the likelihood of them ever being placed on the Endangered Species List.
The researchers discovered that in edge habitats where conifers were encroaching into sagebrush or grasslands, there were much lower populations of songbirds and lower success rates of babies surviving because conifers provide perches for predatory raptors.
Sage thrashers are extremely sensitive to conifer presence, and researchers didn’t find a single nest or a territory near trees. Brewer’s sparrows’ abundance and reproductive success increased when and where trees were removed. Vesper sparrows also benefited from conifer management in sagebrush grasslands. Removing the conifers was a win-win situation for these three bird species.
This study was a resounding success, benefiting many species that fit under the umbrella, including big game animals like mule deer, pronghorn antelope, and sage grouse, people working the land, and cattle producers. It shows that promoting and maintaining sagebrush habitat and removing conifers helps further grasslands and those who depend upon them. The positive outcomes of this research give hope for the future of these species and the ecosystems they inhabit.
Benjamin Alva Polley is a place-based storyteller. His stories have been published in Audubon, Esquire, Field & Stream, The Guardian US, Outside, Popular Science, Sierra, and other publications on his website. He holds a master’s in Environmental Science and Natural Resource Journalism from the University of Montana.
