Greater sage grouse habitat is declining at a sharp rate in the West, and aggressive steps need to be taken to shift away natural gas and oil development, according to a peer-reviewed study.

The three-year study, published earlier this month in PLoS ONE, an open-access scientific journal, is one of the first to look at drilling’s impact on a specific species. The findings come as the Obama administration nears a February deadline on whether to list the sage grouse as threatened or endangered under the Endangered Species Act (ESA) (see NGI, July 6).

“Our analysis shows that we can expect a 7-19% population decline in sage grouse from future oil and gas development and that the impacts within our study area will be greatest to sagebrush (3.7 million hectares) and grassland (1.1 million hectares) ecosystems and the species that inhabit them,” the authors said.

If sage grouse is federally listed, the bird’s status could curb natural gas and oil drilling, impact grazing rules and slow development across parts of the U.S. West. Last month Wyoming Gov. Dave Freudenthal said listing the sage grouse under the ESA would impact an estimated 83% of the gas production, 64% of the oil production and 80% of the coal production in his state (see NGI, Sept. 21).

The new study was completed by members of The Nature Conservancy, the National Audubon Society and the Wildlife Biology Program at the University of Montana in Missoula. According to the authors, some studies have quantified the indirect effect of hydrocarbon economies on climate change and biodiversity, but “few studies have measured the direct effect of new energy production infrastructure on species persistence.”

Greater sage grouse was chosen for the study because it is “a species for which energy development impacts have been well documented, spatially comprehensive and long-term data is available,” the study noted.

By creating “build-out scenarios” for future energy development demand, the authors quantified future impacts on sage grouse in six western states. A map was created of gas and oil development potential for portions of 12 states in the Intermountain West, and the authors relied on “the most recent” available Bureau of Land Management (BLM) planning documents.

In addition to the federal information, the authors used oil and gas well data acquired from IHS Inc. Statewide gas and oil well records were merged into a single well file, with injection, storage and unclassified wells, and wells without permits or with drilling in progress, removed.

The authors admitted that the drilling data from federal and state sources could change.

“BLM estimates are frequently revised from new field discoveries and as technological advances influence resource extraction methods,” the study noted. “Forecasted impacts to sage grouse populations could be revised lower if directional drilling to reduce well pad density at the surface became more commonplace.

“Our build-out scenarios are applicable across whole landscapes regardless of land tenure because we assumed that development could occur on any parcel of land, public or private…Our estimates provide insights into the trajectory and eventual endpoint of oil and gas development, but the rate and exact location of development will be subject to additional factors not considered such as market demand, the capacity to transport oil or gas to consumers, and federal air and water quality laws (e.g. Clean Air Act, climate change legislation).”

The study, “Mapping Oil and Gas Development Potential in the US Intermountain West and Estimating Impacts to Species,” is available at

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