Sage-grouse Priority Areas Function as an Interdependent Network
BOISE, Idaho — The network of greater sage-grouse priority areas is a highly centralized system of conservation reserves.The largest priority areas likely can support sage-grouse populations within their boundaries, but smaller priority areas will need to rely on their neighbors in the surrounding network to sustain local populations, according to new research by the U.S. Geological Survey.
Eleven western states and federal management agencies within the greater sage-grouse range have developed conservation plans that embrace the concept of priority areas – also referred to as Priority Areas for Conservation or PACs by the U.S. Fish and Wildlife Service. Priority areas are key habitats identified as having the highest number of greater sage-grouse and the resources of greatest benefit to the species. Priority areas were designed to balance the needs of sage-grouse with activities such as energy development by focusing conservation activities and regulating development in these areas.
“The development of the priority areas may represent one of the largest experiments in conservation reserve design for a single species,” said Michele Crist, USGS wildlife biologist and lead author of a new USGS Open-File Report. “We have an opportunity to understand the potential for these areas to function as a connected network to conserve greater sage-grouse populations.”
The researchers ranked the relative importance of all the priority areas using social network theory, centrality metrics, sage-grouse ecological minimums, and a range-wide map created by combining the priority area boundaries as delineated by the 11 western states within the sage-grouse range – Washington, Oregon, California, Idaho, Nevada, Montana, Utah, Wyoming, Colorado, North Dakota and South Dakota.
Centrality metrics described the number of connections any one priority area has to another priority area as well as how that priority area acts as a bridge between priority areas. These metrics, combined with an index of sage-grouse movement through the landscape based on a combination of ecological factors necessary to support sage-grouse, were used to rank the priority areas’ relative importance to one another. Highly ranked priority areas are large in size, more centrally located within the network, and surrounded by many other priority areas of various sizes.
The study shows that the loss or fragmentation of one of the larger, highly ranked priority areas could have a disproportionally large influence across the priority area network. The study also identifies linkages and narrow corridors between priority areas where landscape conditions are favorable for sage-grouse movement and may be important for sustaining sage-grouse movements among the priority areas. Other lower-ranking priority areas may also be important stepping stones along habitat corridors to connect smaller more isolated priority areas to allow movement of sage-grouse between priority areas.
“The current priority area network consists of large and small areas that collectively and individually address requirements important for maintaining greater sage-grouse populations,” said USGS research ecologist and co-author Steve Knick. “This study’s findings may help predict impacts to connectivity when priority areas are lost, degraded, or fragmented.”
Knick noted that it is critical for strategies focused on conserving greater sage-grouse to assess not just the size of the priority area and the number of connections, but also how sage-grouse are linked together to function as a viable population.
The study was funded by the U.S. Geological Survey and the U.S. Fish and Wildlife Service, and was prepared in cooperation with Western Association of Fish and Wildlife Agencies.
Greater sage-grouse occur in parts of 11 U.S. states and 2 Canadian provinces in western North America. The U.S. Fish and Wildlife Service is formally reviewing the status of greater sage-grouse to determine if the species is warranted for listing under the Endangered Species Act.