Big Picture of Woodland Management in Sagebrush Country
May 9, 2019
Conifers encroach on the sagebrush sea. Targeted removal efforts are making a difference, but more needs to be done.
New research highlights reduction and expansion of conifer encroachment in sagebrush ecosystems
Around the world, trees are taking over productive shrub and grasslands. Every continent except Antarctica is now experiencing the challenges associated with woodland invasion of valuable grasslands. In North America, one of the most concerning vegetation transitions is the encroachment of pinyon-juniper woodlands into sagebrush rangelands. Expanding conifer trees threaten habitat for sagebrush-dependent wildlife, reduce water availability, increase the risk of high-severity wildfires, and diminish forage for livestock.
Public and private conservation partnerships, like SGI, have been working together to
halt the invasion of trees onto rangelands. However, since conifer treatments span multiple states, counties, and land ownerships, it’s been difficult to calculate the full extent of pinyon-juniper removal.
A new conifer mapping effort provides this detail, showing where conifer management and fire are reducing conifer cover and where conifer cover is growing.
Partnerships are restoring precious sagebrush ecosystems in priority watersheds, but we’re still getting flanked by infilling trees across many western rangelands. This new research shows that we need to keep our foot on the gas implementing sagebrush conservation practices like conifer removal to keep rangelands healthy and productive. – Steve Small, BLM
The researchers used LandSat satellite imagery from 2011-2013 to map conifer cover on roughly 285,000 square miles of sagebrush rangelands. Next, they used satellite imagery from 2015-2017 to re-map the area. By combining these maps with Google Earth Engine data, geospatial datasets and modeling programs, the researchers were able to also show: 1) where management efforts reduced conifer cover, 2) where fire reduced conifer presence and 3) where conifer cover increased.
Key Findings From the Study Include:
- From 2011-2017, the extent of conifer cover in sagebrush country decreased by 1.6%. Human management efforts are responsible for 2/3 of the total reduction; the other 1/3 is due to wildfires.
- Previous estimates suggest that conifer cover in sagebrush country is growing by 0.4%-1.5% annually, which means that our efforts are keeping pace with conifer encroachment but that more needs to be done.
- Public/private partnerships are successfully reducing conifers in highly targeted priority watersheds, such as in northwest Utah.
- The maps also show that woodlands are still expanding into many sagebrush landscapes. Continued partnership efforts are needed to strategically conserve priority shrublands.
This research reveals that strong cross- boundary partnerships are working to restore a
few priority watersheds. In northwestern Utah, for instance, some of the most intensive conservation efforts to date have reduced conifer cover by 4.3% in this region, nearly three times the range-wide rate.
This research was made possible due to cross- boundary partnerships. The Bureau of Land Management through the Partnering to Conserve Sagebrush Rangelands effort with the Intermountain West Joint Venture contributed funding for this study.
More Conifer Expansion Resources
The Sage Grouse Initiative is a partnership-based, science-driven effort that uses voluntary incentives to proactively conserve America’s western rangelands, wildlife, and rural way of life. This initiative is part of Working Lands For Wildlife, which is led by USDA’s Natural Resources Conservation Service.