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New Study Chronicles Declining Populations, Major Threats to Sage-Grouse

Feds Considering ESA Listing for Greater and Mono Basin Sage-Grouse

DENVER - The U.S. Geological Survey has posted 24 of 25 chapters of a new, definitive monograph on sage-grouse just months before the U.S. Fish and Wildlife Service is scheduled to render multiple listing decisions for the species. The monograph, tentatively titled “"Ecology and Conservation of Greater Sage-Grouse: A Landscape Species and its Habitats,” documents declining populations and major threats to this imperiled species, from energy development and West Nile virus to invasive species and free-roaming horses and burros.

The Fish and Wildlife Service is required, pursuant to federal court approved settlements, to make listing decisions for greater sage-grouse and Mono Basin area sage-grouse under the Endangered Species Act. The greater sage-grouse occurs in sagebrush steppe in eleven western states. The Mono Basin area sage-grouse is a genetically distinct subpopulation with a much smaller range in southeastern California and southwestern Nevada.

The 24 chapters provide important information about sage-grouse and their habitat:

“Model forecasts suggest that at least 13% of the populations but none of the [sage-grouse management zones] may decline below effective population sizes of 50 within the next 30 yr, while 75% of the populations and 29% of the SMZs are likely to decline below effective population sizes of 500 within 100 yr if current conditions and trends persist” (chapter 16).

“Shrublands developed for energy production contained twice as many roads and power lines, and where ranching, energy development, and tillage agriculture coincided, human features were so dense that every 1 km2 could be bounded by a road and bisected by a power line” (chapter 21).

"Sage-grouse respond negatively to three different types of development and conventional densities of oil and gas wells far exceed the species’ threshold of tolerance" (chapter 21).

“A large proportion of existing sagebrush communities is at moderate to high risk of invasion by cheatgrass” (chapter 11).

“Juniper and pinyon woodlands have expanded into sagebrush habitats at higher elevations… Approximately 12% of the current distribution of sagebrush is predicted to be replaced by expansion of other woody vegetation for each 1 C increase in temperature” (chapter 11).

“Very little of the lands used by Greater Sage-Grouse has protected status in national parks or reserves” (chapter 2).

“Available evidence clearly supports the conclusion that conserving large landscapes with suitable habitat is important for conservation of sage-grouse” (chapter 4).

Notably, among the chapters posted today, none describes the myriad effects of domestic livestock grazing on sage-grouse and sagebrush steppe. Livestock grazing degrades nesting, brood-rearing, summer and winter habitat, and spreads cheatgrass and other invasive weeds into sagebrush habitat. A cow has been observed eating a sage-grouse egg in Nevada, and researchers reported this week 146 cases of sage grouse flying into a nearly five-mile section of barbed wire fence over a seven-month period in Wyoming.

The chapters posted today are peer-reviewed and have been accepted for publication together in a special volume in Studies in Avian Biology, a series published by the Cooper Ornithological Society. One more chapter, a synthesis of current trends and management, must still be finished for the monograph. The U.S. Geological Survey has also distributed a news release on the monograph chapters.


 

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