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Nature or Nurture? Researchers Say Both Important for Imperiled Sagebrush Ecosystems

-By Trevor Caughlin

Photograph of Sagebrush in different seasons
The big sagebrush (left) dominates vast stretches of iconic landscapes in Western North America (right). Photo by Trevor Caughlin

Historically, vast areas of cold desert in the Western United States were defined by the abundance of one keystone plant species: sagebrush. Yet the iconic sagebrush plant with its aromatic green-gray leaves and gnarled woody trunk is disappearing from western landscapes, threatened by wildfires, invasive species and urban growth.

To curb the degradation of this imperiled ecosystem, land managers have spent hundreds of millions of dollars to restore sagebrush populations across their historic range in the Great Basin. However the enormous range of environmental conditions in the Great Basin, from Badwater Basin (the lowest point in North America) to Mount Whitney (the tallest mountain in the contiguous United States) complicates the question of how sensitive sagebrush cover is to human impacts, both positive and negative.

In a study of sagebrush distribution spanning more than 200,000 square miles, Boise State researchers led by post-doctoral researcher Juan Requena-Mullor are working to find the answers to this question. In collaboration with agency partners at the United States Geological Survey, the research team assembled a record of data on sagebrush plants, fire history and restoration treatments spanning nearly 30 years. The project is supported by the National Science Foundation Established Program to Stimulate Competitive Research GEM3.

“Sagebrush steppe helps to maintain soil stability, water availability, stabilize the natural wildfires regimen and provides crucial wildlife habitat,” said Requena-Mullor. “Our research allows an understanding of how human impacts occurring at a local scale affect sagebrush at broader scales and provides key insights for its long-term conservation.”

The researchers then applied mapping and mathematical models to tease apart the importance of wildfire and restoration from climate and topography. They found that wildfire history had negative impacts on sagebrush comparable to the effects of geographic variation in elevation, rainfall and temperature. This result emphasizes the threat that changing wildfire frequency poses to ecosystem health in the West.

A photo of a burned area juxtiposed with a photo of healthy sagebrush
Sagebrush view after wildfire (left) and post-fire ecosystem recovery (right). Photo courtesy of the United States Geological Survey.

At the same time, the team found cause for hope. Restoration action can have a positive impact on sagebrush ecosystems. This was a surprising result, because the 35-year record of restoration treatments included a very wide range of management actions, from planting seedlings to invasive species removal. Altogether, these results point the way for models and mapping to conserve an imperiled habitat.

To read more about the team’s research, read more here:

Citation: Requena‐Mullor, J. M., Maguire, K. C., Shinneman, D. J., & Caughlin, T. T. (In Press). Integrating anthropogenic factors into regional-scale species distribution models — a novel application in the imperiled sagebrush biome. Global Change Biology. doi: 10.1111/gcb.14728

This project, “RII Track-1: Linking Genome to Phenome to Predict Adaptive Responses of Organisms to Changing Landscapes,” was funded under National Science Foundation grant No. OIA-1757324. The total amount of federal funds for the project will be $20 million, which amounts to 83 percent of the total cost of the project. The total amount of non-federal funds for the project will be $4 million, which amounts to 17 percent of the total cost of the project.