New research finds sage grouse populations grow faster in areas with juniper tree removal

Portland, Ore. – June 14, 2021 —  Recently published research found sage grouse populations  grow faster in areas restored by removing juniper trees, highlighting a key to sage grouse conservation efforts in the West.

The research, culminating findings of an eight-year study in the Warner Mountains conducted by University of Idaho and Oregon State University students and advisors, found that strategically removing encroaching trees spells good news for sage grouse, a declining upland bird that serves as a key indicator for the overall health of the sagebrush biome.

This study adds to a growing body of research — much of it based on the long-term study in the Warner Mountains — that documents the numerous benefits of conifer removal for wildlife and grazing lands.

The Warner Mountains run north to south from southern Oregon into northern California. In Oregon’s Warner Mountains, sagebrush rolls across hillsides and valley bottoms, providing productive land for livestock and wildlife.

Like many places in the West, these valuable rangelands are at risk from encroaching trees that displace wildlife, reduce livestock forage, and decrease available water. More than one million acres of sagebrush grazing lands in the Great Basin have turned into pinyon-juniper forests in the past two decades alone.

Sage grouse, a bird who evolved in a large and treeless landscape, suffer when trees take over. Birds avoid mating or nesting if there are more than a couple trees on the landscape, likely because conifer woodlands are riskier habitats for grouse with more predators. Other sagebrush-reliant wildlife like mule deer and songbirds are also negatively impacted when conifers crowd out the perennial plants they need for food and cover.

“In places where junipers were removed, the sage grouse population grew at a rate that was 12 percent greater than in an area where no trees were cut,” explained Andrew Olsen, who led the research for Oregon State University. “By targeting removal where sagebrush plants were still intact, we bought instant habitat for a declining bird species.”

Unfortunately, trees are taking over America’s grazing lands at an alarming rate. Conifers like Western Juniper have expanded by as much as 600% over the last 150 years — and 90 percent of that expansion has occurred in sagebrush country.

Olsen’s research demonstrates how removing expanding conifers before they get too dense can bring back the birds. A previous study from the Warner Mountains found that 29% of marked hens moved back to nest in restored habitat just three years after conifers were cut. Additional research in the Warners also revealed the abundance of sagebrush-loving songbirds, also species adapted to large treeless expansions, doubled following restoration through juniper removal.

“While conifer removal in the Warners has been shown to help sage grouse, many different wildlife and plant species are also benefiting from the restoration of these open sagebrush habitats,” said Todd Forbes, district manager of the Bureau of Land Management’s Lakeview District in Oregon.

Other key project partners include the Bureau of Land Management, USDA Natural Resources Conservation Service, private landowners, Oregon Department of Fish and Wildlife, and NRCS Conservation Effects Assessment Project.

NRCS Working Lands for Wildlife

Through the USDA’s Natural Resources Conservation Service’s Working Lands for Wildlife program, landowners in sagebrush rangelands receive incentives to remove junipers on their properties, helping sage grouse populations thrive.

Beginning in 2010, the USDA’s Natural Resources Conservation Service teamed up with private landowners through the Working Lands for Wildlife Sage Grouse Initiative, public land managers with the Bureau of Land Management, and other local partners on a collaborative, large-scale conifer removal effort in the Warner Mountains. The groups also enlisted the help of university scientists to monitor the outcomes of their work over time.

Ranchers who participated in the project are seeing the positive results from restoring sagebrush rangelands.

“The big value is that removing conifers gives you a reset,” said John O’Keeffe, who ranches near Adel, Oregon, and partnered with NRCS Oregon to remove junipers on his property. “As the trees get thicker and thicker, you lose your understory vegetation and that puts your topsoil at risk. Conifer removal keeps the land in a state where we have native bunchgrass that allow for cattle, grouse, deer, and antelope. Once the conifers get too dense, you lose all of that.”

Using hand-held chainsaws to minimize ecological disturbance, private landowners like O’Keeffe worked alongside public land managers at BLM to strategically remove trees from 34,000 acres (53 square miles) to restore and expand sagebrush habitat. The project partners targeted tree removal places where there was still a healthy understory of native shrubs and plants so birds could move into the habitat right away.

While conifer removal was underway, researchers monitored the outcomes by tracking 417 sage grouse hens with transmitters. The latest Oregon State University study quantified how the bird’s population growth rate has changed over time. Olsen and other researchers marked hens in a 109,000-acre treatment site where trees were removed, as well as in a nearby control site, an 82,000-acre landscape where no conifer removal occurred. They compiled different vital rates of these hens with lek count data from the region.

Five years after conifer removal, the growth rate of the sage grouse population was about 12% higher the treatment site than at the control site. Plus, the survival rates increased for most stages of the bird’s life cycle where junipers were cut. This is encouraging news for conservationists who have been collaborating on similar conifer removal projects across the West to restore open sagebrush habitat.

“We couldn’t be more excited about this new science,” said Ron Alvarado, state conservationist for NRCS Oregon. “Our strategic conservation efforts to help ranchers restore sagebrush range lands are working and these findings highlight that conservation success.”

Over the next five years, NRCS will continue to help ranchers across the West remove conifers to boost agricultural productivity and benefit wildlife. NRCS’ Working Lands for Wildlife recently released a Framework for Conservation Action in the Sagebrush Biome, which details how local, state, and federal partners plan to work together on voluntary, incentive-based strategies to address the main threats facing sagebrush rangelands. In addition, the BLM and NRCS developed the Rangeland Analysis Platform, a free online mapping tool that helps landowners plan conifer removal projects by showing how and where tree cover has changed over time.

Learn more about the Working Lands for Wildlife program here. To learn more about assistance available through the Working Lands for Wildlife program, contact your local USDA service center.