The science is stacking up on the need to close some roads, especially those first constructed for resource extraction, to improve struggling grizzly bear populations in Western Canada.
Higher road density leads to lower grizzly bear density, says population ecologist Clayton Lamb, a PhD candidate at the University of Alberta. He co-authored a study that appears Tuesday in the Journal of Applied Ecology.
In 2015, Lamb and fellow researchers collected grizzly bear hair samples across an 8,000-square-kilometre area in the Monashee Mountains, east of the Okanagan.
The area has been heavily affected by the logging industry, with about 1.6 kilometres of road for every square kilometre of wilderness land area.
“If you’re to add all of the roads up, there’d be about 10,000 kilometres in that area,” he said. “To drive from Vancouver to Ottawa, it would be less than 5,000 kilometres.”
The team used DNA to identify individual bears and estimate the density of the bear population.
The next step was to ask how the landscape affects those numbers.
“We found that heavily roaded areas have lower grizzly bear density,” Lamb said.
He noted the B.C. government has closed public access to some of these roads.
“It showed by closing these roads, the public restored grizzly bear density in that area. Maintaining a large roadless area was critical to maintaining a large population of grizzly bears in the area and recovering it.”
Grizzly bears threatened in Alberta
Grizzly bears were listed as threatened in Alberta in 2010 when it was determined there were only about 700 left. A recovery strategy was introduced aimed at reducing conflicts between bears and people.
Grizzly bear researchers such as Gordon Stenhouse from the Foothills Research Institute have also shown how roads affect the survival rates for grizzly bears.
Lamb said when it comes to grizzly bear density, the risks of roads are twofold.
“Roads and the humans that travel them increase both the risk of grizzly bear mortality and the chance the bear won’t use habitat near the road anymore,” he said.
“You could have fewer bears because they’re killed near the road, or you could have fewer because bears avoid the area because there are people on the road. It’s likely a result of both of those mechanisms that result in lower grizzly bear density.”
Many of the roads in the area that Lamb studied were initially…