Natural and human factors make it unlikely a proposed federal network of greater sage grouse conservation habitat will stay intact, the government’s own scientists say.
Scientists also question whether the priority-area conservation plans — known in Wyoming as the core-area strategy — will save small, scattered populations.
The “priority,” or “core-area” framework, is the lynchpin in U.S. Bureau of Land Management and U.S. Forest Service plans to save the dwindling species. But the plans’ framework is “a grand experiment” that carries no guarantees for saving the species, authors of a new study say.
“Numerous factors, both natural and anthropogenic, make it unlikely that the current network of priority areas can be sustained,” the 42-page research paper published last week says. The strategy could isolate pockets of birds leading to “loss of sage-grouse within these regions of the network.”
Penned by the U.S Geological Survey, the paper was funded by it and the U.S. Fish and Wildlife Service, both arms of the Department of the Interior. Fish and Wildlife, through the Endangered Species Act, is responsible for the conservation of species. It judges whether plans — like those proposed by the Forest Service and BLM — will work. But instead of being a guarantee, the priority or core-area strategy is only a “grand experiment,” the authors say.
Fish and Wildlife must decide by Sept. 30 whether the greater sage grouse should remain a candidate for Endangered Species Act protection. Listing the grouse as threatened or endangered could restrict land use across the West’s sagebrush sea with corresponding economic impacts. Regardless of that decision, the underlying federal conservation plans would still be implemented.
Core-area strategy under the microscope
The paper analyzes the core-area strategy that Wyoming adopted in 2008 and which federal agencies have embraced. In Wyoming, federal plans propose 8.3 million acres of priority habitat, another 8.65 million acres as less-protected general habitat.
Priority areas are those “having the highest value to maintaining sustainable [greater sage grouse] populations.” In them, the goal is to minimize new surface disturbance, improve habitat and reduce the threat of fire. But the conservation effort will take more than that, said Steven Knick, one of the authors.
“Given the amount of change we are seeing — the fires in the West — it’s just unlikely over the long term that the current configuration [of priority habitat] will remain that way,” he said. Wildfires that destroy sagebrush can render priority habitat unusable by the birds. “That boundary will be readjusted.There likely will be areas added as we lose parts, pieces or all of the current network as defined. We’re at the very beginning of this kind of strategy of priority areas, in that it’s going to take monitoring and time to say how well this works.
“This design doesn’t end it all,” Knick said. “It’s rather just part of the process we’re attempting to learn from and, hopefully, we can understand a little bit more about sage-grouse land use and what it takes to conserve them.”
All grouse eggs in one basket?
The paper Range-wide network of priority areas for conserving greater sage-grouse — A design for conserving connected distributions or isolating individual zoos? warns of a potential deep problem with the priority, or core-area, strategy.
Using “centrality metrics from social network theory,” researchers illustrated how the sage grouse plans might function. They identified 118 priority areas ranging in size from 272 acres to 20.5 million acres. They calculated “centrality scores” for each.
A centrality score is “an index that’s based on the number of connections you have with neighbors,” Knick said. If 80 percent of connections go through one person, for example, “that one person is very important.”
In the case of grouse habitat, only 20 of the 188 priority areas — about 10 percent — account for 80 percent of the connections. “All your eggs may be in one basket with these large priority areas,” he said. In conservation biology, such concentration raises the specter that a single event or catastrophe — a wildfire, heavy predation, or disease outbreak — could upset a population.
There’s another danger. “Many of the areas themselves are too small to support a viable population,” Knick said. “If something disrupts that connection [to other grouse habitats], then you effectively isolate that priority area.
“If they put all their conservation into strictly the priority areas without ensuring some kind of functional connection, there’s a risk you’ll see isolation of some populations,” Knick said. Isolated populations, especially small ones, are usually in greater danger of extinction than connected ones. “I think connectivity is important,” Knick said.
Wyoming has designated connectivity areas, inside the state as well as to its borders. But the idea is not a tenet in the sage grouse conservation thrust, Knick said. “I don’t know that anyone has specifically said ‘Here’s a pathway that we need to focus on.’”
Even defining connectivity is dodgy. There’s genetic connectivity, for example. A grouse flying from one area to another and mating there every 10 years might provide that.
There’s also seasonal, migratory connectivity. And there needs to be a connection between a small area and larger ones that provide overflow birds to keep the smaller area populated.
“You need to be careful in defining what connectivity you’re talking about,” Knick said. Plus, scientists still don’t know everything about how and why sage grouse move.
“We don’t know how a sage grouse perceives its landscape,” he said. “We don’t know exactly what sage grouse are willing to cross.”
The research paper may not recognize all conservation efforts, an advocate for the BLM, Forest Service and Wyoming plans said.
“I thought it missed a couple things,” said Brian Rutledge, vice president and executive director of Audubon Rockies. “The study seems to assume there won’t be birds anywhere but in their core habitat. That’s not what we’re seeing and that’s not the intent. These birds are capable of [flying] greater distances than people think — 40 to 50 miles to nest site from lek.
“There are still protections in non-core to allow for genetic drift,” he said. There also are grouse corridors across state lines. “I don’t know that those were counted for in their study.”
The paper reveals flaws in the conservation plans, said Steve Holmer of the American Bird Conservancy. “This USGS study is very relevant and indicates that the plans may not have designated enough protected habitat,” he said. “Right now they need to go further.
“Based on this analysis, which indicates that many of the proposed priority habitat patches are too small … it may be necessary to add to the priority habitat,” he said. “It also indicates that loopholes in the plans to allow for continued oil and gas drilling, mining, and power line construction need to be tightened up to ensure the priority habitat remains viable.”