A new federal study covering oil and natural gas development in Wyoming over a 25-year period found that as drilling density increased, the productivity of greater sage grouse breeding grounds consistently declined.
The conclusions in the latest peer-reviewed study — led by researchers at the U.S. Geological Survey and Colorado State University and published in The Journal of Wildlife Management — analyzed male attendance at grouse breeding grounds near drilling sites in Wyoming between 1984 and 2008. They found that male counts at these sites, called leks, decreased by 2.5 percent every year during the study period.
The decline in male attendance was “negatively related to oil and gas well density,” the 12-page study concludes. The low male attendance did not appear to be influenced by other factors including the height of sagebrush cover or precipitation patterns.
“Our results support those of other studies reporting negative impacts of oil and gas development on sage-grouse populations and our modeling approach allowed us to make inference to a longer time scale and larger spatial extent than in previous studies,” the study says.
What’s more, the study says that nearby oil and gas drilling “may also negatively affect other sagebrush-obligate species,” such as mule deer and elk, and that “active management of sagebrush habitats may be necessary to maintain some species.”
The link between drilling density and declining sage grouse populations is well-known. Oil and gas drilling, and the associated roads, pipelines and other infrastructure, have been shown in previous studies to drive away grouse.
But the study appears to counter a detailed report released last summer by the Denver-based Western Energy Alliance and the Petroleum Association of Wyoming, which concluded that advances in horizontal drilling have significantly reduced the amount of surface acreage needed to tap oil and gas reserves in environmentally sensitive areas (EnergyWire, June 15).
The result, according to that report, is that sensitive species like greater sage grouse, mule deer, elk and pronghorn “can coexist with energy development,” and even thrive.
Kathleen Sgamma, the Western Energy Alliance’s vice president of government and public affairs, dismissed this new study, saying it is based on “old data” and “obsolete assumptions” about oil and gas development.
“The study ignores more recent information that shows surface disturbance has been dramatically reduced, by up to 70 percent, because of horizontal drilling and other industry innovation,” Sgamma said in an emailed statement to E&E News.
“The study suggests that at well densities over 10 wells per square mile there’s an impact on sage grouse, yet in 2016, industry practices combined with the state’s sage grouse plan mean that well pad densities are well below that number,” she added. “Other than for historical purposes, this study is largely irrelevant to what’s actually happening in Wyoming’s sage grouse habitat today.”
But Chris Saeger, director of the Western Values Project, said he disagrees.
Instead, Saeger said the study’s conclusions justify the oil and gas development protection measures included in the Interior Department’s sage grouse conservation plans, which call for guiding drilling away from sensitive grouse habitat.
The Western Energy Alliance and the North Dakota Petroleum Council earlier this year filed a federal lawsuit challenging the federal sage grouse plans as violating key federal laws (Greenwire, May 12).
“The [federal] plans are designed to take new information on board, so the results of this study will only make this effort stronger,” Saeger said.
Thanks to the federal plans, he said, grouse habitat conditions have improved.
The latest report, he said, is a “reminder of how far we’ve come since 2008, when special interests dictated how our public lands should be used. Now, thanks to the plans and ongoing collaboration between federal and state agencies, sportsmen and others who care about our public lands, conditions are improving for sage grouse and the landscapes they inhabit.”
USGS and Colorado State University defended the study, saying the years of data collected and analyzed allowed the researchers to look at many aspects of oil and gas drilling on grouse, including the “delayed response” in some cases to nearby development.
“This approach allowed us to look at long time periods, including years before the oil and gas boom, which gave us a better picture of how sage-grouse have responded to oil and gas development,” Adam Green, lead author of the paper and a former CSU research scientist, said in a statement. “We found evidence of decreasing populations in response to increasing oil and gas development. This response was apparent as far as four miles from a lek, and the response was strongest four years following development.”
This detailed look at the responses of grouse over an extended period of time is relevant, in large part, because USGS says global energy demand is expected to increase “substantially in the next two decades, with fossil fuels accounting for more than one-third of that demand.”
The researchers found that sage grouse populations were stable when no wells were present near a lek, but “began declining with the addition of the first well,” according to a USGS summary of the study.
“Declines were not statistically significant until well density reached about 10.4 wells per square mile; however, at this well density, populations were predicted to decline 14 percent per year,” the summary says.
The study suggests that even well densities at one well per square mile within the boundaries of Wyoming’s designated core sage grouse areas “will likely result” in population declines.
“Energy development continues to affect important sagebrush habitat required by sage grouse and other species,” said Cameron Aldridge, an associate professor at CSU and one of the study’s authors. “This analysis provides new information to managers on how sage grouse populations respond to energy development, as they simultaneously work to implement conservation measures for sage grouse and meet demands for additional energy supplies.”