U.S. Fish and Wildlife Service

The photo looks down on sagebrush ecosystem being overtaken by conifer trees. Most trees and shrubs bear bright green foliage, some trees and shrubs are white and have no leaves. Behind the sagebrush lies foothills, with snow-capped mountains further in the background

The expansion of trees into sagebrush

Information icon Encroaching conifers and sagebrush. Photo by Tracy Robillard, NRCS Oregon.

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In most cases, we think of more trees as more of a good thing and, in most cases, that is true.

However, in sagebrush country, sagebrush bushes were historically the largest plants on the landscape. The fast-paced encroachment of conifer trees, such as juniper and pinyon pine, into sagebrush habitats is changing the dynamics of this delicate ecosystem in ways that have negative impacts for many species of native wildlife.

The intrusion of conifers into sagebrush is primarily in response to suppression of natural wildfire cycles, intensive livestock grazing, and changes in the climate. Conifers are anticipated to continue their expansion in the future unless effectively treated, with the most pronounced risks occurring in the Great Basin (western) portion of the sagebrush ecosystem.


The Problem Plants

Two images side by side. One the left, a lone juniper tree stands in sagebrush habitat. On the right, a pinyon pine tree
On left, a lone juniper tree stands in sagebrush habitat. Creative Commons licensed photo by Matt Lavin. On right, a pinyon pine tree. Creative Commons licensed photo by Jimmy Thomas.

The Negative Impacts


Trees that encroach into sagebrush habitat disrupt the ecosystem, and have been shown to:

Conifers encroaching on sagebrush habitat in Paulina, Oregon
Conifers encroaching on sagebrush habitat in Paulina, Oregon. Photo by Tracy Robillard, NRCS Oregon.

Solutions


Treatment methods include cutting, mastication, prescribed burning, and herbicide application. These treatments have different costs and varying impacts on the desirable plant species and degree of surface disturbance.

Proactive removal of conifers during early phases of invasion, with minimal ground disturbance and retaining perennial shrub and herbaceous communities, is the most cost-effective treatment and reduces risk of invasive annual grasses moving in post-treatment. In addition, the greater the cover of perennial grasses and forbs prior to treatment, the greater the likelihood the system can resist invasion by cheatgrass.

As with all conservation issues in sagebrush country, communication and collaboration with our county, state, and federal partners, as well as private landowners, is critical to our success.

An eagle-eye perspective, with slight fish-eye distortion, of sagebrush landscape that is being overrun with conifer trees. The picture shows a bulldozer removing small conifer bushes as part of a conifer removal project
A conifer removal project funded by the Sage Grouse Initiative outside of Minden, Nevada. Photo by NRCS.

References and More Information