other.
“What conservation geneticists have argued for some time is that the focus ought to be on preserving for the long term the whole metapopulation,” says Bergstrom, the Valdosta State professor. “Then, you have to look at how each subpopulation plays into that ultimate goal.”
Van Manen says he isn’t concerned about the loss of genetic diversity if the Yellowstone and Northern Continental bears are prevented from naturally connecting. He says there is no indication now or in the near future of genetic depression with the Yellowstone bears.
He points to a 2015 research paper that concluded the Yellowstone population is “sufficiently large to avoid substantial accumulation of inbreeding depression, reducing concerns regarding genetic factors affecting the viability of the Yellowstone grizzly bears.”
And if genetic depression becomes a factor, van Manen supports the approach of translocating bears. “There would be an easy solution by moving animals from another ecosystem into Yellowstone and make sure they breed and produce offspring. It only takes a few animals in every generation to do that.”
The same research paper states that over many generations the grizzly population “could benefit from increased fitness following the restoration of gene flow particularly given the unpredictability of future climate and habitat changes.”
Conservation groups including Defenders of Wildlife and Greater Yellowstone Coalition stated in a 2015 letter to the U.S. Forest Service concerning grizzly recovery plans that relying on “human assisted trans-location does not support the notion that the [Yellowstone] population has been restored to where it is again a secure self-sustaining member of its ecosystem.”
That supports the conservation researchers’ contention that natural grizzly bear dispersal between the subpopulations helps strengthen the entire metapopulation and would support creation of a healthy regional ecosystem that can support the West’s largest predator and other species such as wolverines.
“So, from the standpoint of greater Yellowstone it is very important that it be allowed to play its role in providing emigrant dispersers to other populations and vise-versa,” Bergstrom says. “Its own health, ultimately in the long term, over many generations, relies on receiving immigrants.”
Grizzly researchers who support natural connectivity versus relying on translocating bears between highly controlled, isolated populations say corridors need to be established between the six grizzly bear recovery zones created by the Fish and Wildlife Service in the 1982 Grizzly Bear Recovery Plan.
So far, none exist. Thirty-five years after adopting the recovery plan, only two of the six ecosystems have a significant number of grizzly bears.
The largest grizzly recovery area is the Greater Yellowstone Ecosystem, with about 700 bears, in northwest Wyoming, southeast Montana and eastern Idaho and includes Yellowstone and Grand Tetons national parks. The Yellowstone ecosystem includes 34,375 square miles, according to the National Park Service, which notes the “size(s), boundaries, and description of any ecosystem can vary.” The Yellowstone Demographic Monitoring Area rests within the Yellowstone ecosystem.
The Northern Continental Divide Ecosystem, with about 960 bears, covers 16,477 square miles in northwest Montana and includes four wilderness areas and Glacier National Park.
In addition, there are about 146 grizzly bears scattered among three of the four ecosystems in Idaho and Washington:
- The Selkirk Mountain Ecosystem encompassing 2,200 square miles in northeastern Washington, northern Idaho and southern British Columbia. It has approximately 88 grizzly bears.
- The Cabinet-Yaak Ecosystem encompassing 2,600 square miles in Northern Idaho is believed to have approximately 48 grizzly bears.
- The North Cascades Ecosystem encompassing 9,500 square miles in north central Washington has between five and 10 grizzly bears and is considered the most at-risk population in the lower 48.
- The Bitterroot Ecosystem in central Idaho is one of the largest 