New Guides-Reducing Conifer Encroachment in Western Rangelands

New Technical and Pocket Guides explain the processes behind tree expansion and provide practical guidance on where and how to prioritize reduction efforts in the northeast portion of the sagebrush biome.

Land managers and conservation practitioners working in Wyoming, Montana, the western Dakotas, and adjacent states now have two new resources to address conifer encroachment on grasslands and shrublands: the Reducing Conifer Encroachment in Western Rangelands technical guide and companion pocket guide. 

Produced by Working Lands for Wildlife, in partnership with the USDA-Natural Resources Conservation Service, these resources help rangeland practitioners, land managers, and landowners identify early-stage conifer encroachment. They also detail proactive, region-specific treatment approaches and prioritization strategies designed to prevent ecosystem losses before they become costly or irreversible.

Conifer encroachment—also referred to as woody encroachment or tree expansion—threatens millions of acres of western rangelands by fundamentally altering ecosystems that support rural livelihoods and wildlife habitat. Since 1990, tree expansion has resulted in more than $5 billion in lost forage production across the western U.S., while degrading habitat for species like sage-grouse, mule deer, and pronghorn. Without intervention, these gradual but compounding changes lead to costly, and often irreversible, ecosystem transitions.  

According to the Sagebrush Conservation Design (SCD):

• Encroaching conifers are the second-leading cause of sagebrush habitat degradation
• The northeast portion of the sagebrush biome   is a top priority  to target conifer encroachment because opportunities to defend and grow core sagebrush areas are highest

The guides equip land managers and conservation planners with science-based strategies for addressing conifer encroachment specifically in the Northwestern Plains, Middle Rockies, Northern Glaciated Plains, and Wyoming Basin ecoregions. They promote a proactive, vulnerability-based approach that prioritizes defending intact “core” rangelands before encroachment occurs—an approach proven to be far more cost-effective than attempting restoration after trees become established. 

Modeled after the Great Plains grasslands-focused Reducing Woody Encroachment in Grasslands: A Guide to Understanding Risk and Vulnerability and its companion pocket guide, led by Dirac Twidwell, Working Lands for Wildlife’s Great Plains grasslands science advisor and a rangeland professor at the University of Nebraska-Lincoln, the new guides respond directly to land manager and conservation planner requests for western rangeland-specific versions of the Great Plains materials. 

“There is a clear and growing need for woody encroachment guidance across the region—especially in Wyoming. While Wyoming landscapes have always included juniper, pines, and other woody species, their distribution and extent shifted dramatically following Euro-American settlement. Today, woody plants are expanding into areas that were historically grasslands. In addition, formerly open woodlands with productive grass understories are converting to closed-canopy stands with little or no herbaceous cover. These changes have real consequences for wildlife and livestock producers.”

~John Hartung, State Rangeland Management Specialist for Wyoming NRCS

Pages from the Technical Guide

The guides help landowners and managers distinguish between areas where conifer trees are historically appropriate and areas where encroachment is driving ecological and economic decline. By clearly identifying early- and mid-stage encroachment, these guides emphasize the importance of acting now—when treatments are more effective, less costly, and far more likely to preserve long-term grassland function and working lands productivity.

“These guides were coproduced with NRCS and university experts from the region to help local land managers and practitioners apply the latest science and strategies to their own backyard.”

~Lead Author Derek Tilley, Working Lands for Wildlife’s Sagebrush Technical Transfer Specialist

Specifically, the guides include detailed information that empowers practitioners to:

Prioritize strategically using a science-based framework that focuses resources where they’ll have maximum impact—protecting intact rangeland cores before they’re invaded. 

Recognize region-specific patterns through detailed scenarios of how different conifer species encroach across diverse landscape settings, from badlands to mountain meadows. 

Detect encroachment early using both cutting-edge remote sensing tools and field-based methods to identify invasion before it becomes visible and costly. 

Design effective treatments by matching appropriate tools and techniques to specific stages of encroachment, from monitoring seed-dispersal zones to managing established woodlands.

Build collaborative solutions that work across property boundaries, recognizing that conifer seeds don’t respect fence lines.