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Powder River Basin Sage-grouse at Risk for Extirpation

Population viability study exposes problems with Core Area strategy in NE Wyoming

Additional Contact:

Erik Molvar, Wildlife Biologist, Biodiversity Conservation Alliance (307) 460-8300

LARAMIE – A new study commissioned by the Bureau of Land Management exposed major difficulties with the agency's current approach to sage-grouse conservation in the Powder River Basin. Conservation organizations are calling for stronger protections based on the results.

The study, authored by scientists from the University of Montana, including eminent sage-grouse biologist Dave Naugle, indicates that an increasing density of coalbed methane wells and conventional oil or gas wells coupled with an outbreak of West Nile virus could cause "functional extinction" of the Powder River Basin population. Under such a scenario, modeling predicts that of 370 active leks (sage-grouse breeding areas) known today, only 6 would remain under a scenario of continued heavy development coupled with a West Nile outbreak.

"The sage grouse population in the Powder River Basin is the critical link between the heart of the sage grouse range in southwestern Wyoming and populations in the Dakotas, Montana, and southern Canada, several of which are already on the brink of disappearing," said Erik Molvar, Wildlife Biologist with Biodiversity Conservation Alliance. "The position of the Powder River Basin as a critical linkage makes the area a Significant Portion of the Range for the sage grouse under the Endangered Species Act. Failure to protect this populations could easily cause the Endangered Species listing of the grouse all by itself."

The study estimates that 27 percent of the pre-development sage grouse population has already been lost as a result of heavy coalbed methane and conventional drilling in the Powder River Basin, and predicts that only 39 percent of the original population will remain when the full build-out of coalbed methane wells reached 8 wells per square mile across the Basin, even in the absence of a West Nile outbreak. The study also found that large leks would be expected to decline by 70 percent from pre-development numbers as well spacing reaches 4 wells per square mile, the standard density for conventional oil and gas but only half the density of coalbed methane fields. The effect of drilling on sage grouse was found in the study to be strong out to 12.4 miles from the lek itself, indicating that larger Core Areas are warranted.

“Every new study on sage-grouse in oil and gas country indicates that we must protect leks with increasingly larger buffers,” said Mark Salvo, Director of the Sagebrush Sea Campaign for WildEarth Guardians. “We’ve been saying it for years: sage-grouse are a landscape species, they need large expanses of undeveloped sagebrush to persist.”

"This study is a wake-up call for the BLM that shows they need to expand the sage-grouse Core Areas in the Powder River Basin," said Molvar. "The current Core Areas in the Powder River Basin exclude the best grouse habitat that's actually at risk of being drilled; it's time for the BLM to stop ducking the issue of protecting sage-grouse in this important region and start protecting the key habitats where oil and gas development is likely."

West Nile virus was identified by the study as a critical factor in determining the persistence of sage-grouse in the Powder River Basin. Earlier studies linked the Culex mosquito, the known carrier of the West Nile virus, to coalbed methane wastewater reservoirs that provide breeding and larval habitat for the mosquito population.

"There is a strong need to switch from surface disposal of coalbed methane wastewater in surface reservoirs to underground injection, so we can get rid of all that mosquito habitat that the coalbed methane industry is creating," added Salvo.

The study is available from Biodiversity Conservation Alliance or WildEarth Guardians on request, and is expected to be posted on the Internet by the Bureau of Land Management today.


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