Sage-grouse were determined by U.S. Fish and Wildlife Service (USFWS) to be warranted for listing under the Endangered Species Act but listing was precluded by other higher-priority species. USFWS has been ordered by a federal district court judge to make a final determination by 2015. Numerous factors, including energy development, loss of habitat to agriculture (especially in Washington and southern Idaho), wildfire, diseases and livestock grazing, have been implicated in the decline.
Potential impacts of livestock grazing are, however, confounded with the grazing impacts of feral horses, especially in the western part of the sage-grouse distribution. Ranchers have complained that they are unfairly blamed for, what are in fact, impacts caused by horses. Additionally, advocates for feral horses have resisted appropriate management of the abundance of horses on public lands.
The Bureau of Land Management now spends about $75M annually on management of feral horses on their lands. It is therefore important to better understand the relative impacts of feral horses versus livestock on vegetation and the associated impacts on sage-grouse populations.
This project takes advantage of a unique combination of historical data and current distributions of feral horses and livestock to separate the effects of horses and livestock on Great Basin vegetation and sage-grouse.