Study: North Cascades grizzlies could gain more habitat as the climate warms
Grizzly bears in Washington’s North Cascades could gain habitat as the climate warms, according to a study that looked at how climate change could affect the reintroduction of grizzly bears.
The study, published in the journal Biological Conservation, found potential high quality grizzly bear habitat in the North Cascades Ecosystem will expand as the climate changes. The study looked at climate scenarios through the 2080s.
For grizzlies, high quality habitat includes plants the bears like to eat, such as huckleberries and cow parsnip, greener vegetation, and open canopies, said Jason Ransom, the lead wildlife biologist for North Cascades National Park and the lead author of the study.
“In the big picture, you’re gaining some of these grizzly bear foods through climate change, which makes them winners,” Ransom said of grizzly bears that could be reintroduced to the North Cascades Ecosystem.
In addition, he said, some high quality habitat will expand higher to elevations, coaxing grizzly bears to move even farther from the river valleys and foothills where people live.
Today, only a handful of grizzly bears might exist in the North Cascades, making this grizzly population the most imperiled in the United States. Washington’s most recent confirmed grizzly sighting happened in 1996. Since then, people have spotted two bears on the Canadian side of the ecosystem.
Now, the federal government once again is considering translocating grizzly bears to the North Cascades Ecosystem. More than 6,000 people recently commented on what officials call a scoping plan, which helps officials consider topics for an environmental impact study.
Over the last century, the killing of grizzly bears and habitat loss extirpated grizzlies from 98% of their habitat, according to the U.S. Fish and Wildlife Service. The North Cascades habitat also is cut off from other grizzly habitats in the Lower 48.
“If we were to magically put grizzly bears back today into the North Cascades, it’s not the same North Cascades as it was 100 years ago,” Ransom said. “Ecosystems change constantly.”
As officials consider moving in grizzlies to the North Cascades, researchers wondered how climate change would affect grizzly habitat, Ransom said.
“When we know that all the models are pointing to ecosystem-scale changes decades from now, or a century from now, I think the responsible management thing is to say, ‘If we’re restoring this species, what does the future look like for them?’” Ransom said.
In moderate heat-trapping greenhouse gas scenarios, the North Cascades might warm up to 5.94 degrees Fahrenheit. Under high greenhouse gas emissions, or business-as-usual scenarios, the North Cascades could warm up to 10.08 degrees Fahrenheit. However, scientists said current policies and increasing renewable energy development could mean the business-as-usual scenario is becoming unlikely.
In Washington, winters will get warmer, with more snow falling as rain, causing significant declines in spring snowpack. Washington also is facing declines in glacier cover, changes to stream flows as snowpack melts at different times, extreme heat, and increasing numbers of wildfires.
With all of the climate change challenges, the grizzly habitat results of this study were surprising, said Meade Krosby, a senior scientist with the Climate Impacts Group at the University of Washington and study co-author.
“After doing this work for some time, any good news is a pleasant surprise,” Krosby said. “In fact, it made me want to double and triple check everything.”
For grizzlies in the North Cascades Ecosystem, high quality habitat increased across all climate scenarios and models, increasing in the central and western parts of the ecosystem and remaining the same or increasing slightly in the eastern areas of the ecosystem, according to the study.
While this study showed a piece of good news about future grizzly habitat, Krosby said, climate change will affect grizzly bears in other ways.
“There are other studies in other areas that have shown changes in the timing or abundance of key seasonal food sources, like berries or seeds, that could negatively affect them,” she said, referring to grizzly bears.
Or, if bears are denning later in the fall because the climate is warmer, bears could be out and about at times that overlap with hunting season, she said.
Moreover, she said, climate change will affect biodiversity in the North Cascades. For example, some wildlife such as wolverines are limited to higher elevations and depend on cold, isolated habitats, making them much more sensitive to the effects of climate change.
For Ransom, the results were reassuring because all the models showed an increase in the scope of high quality habitat.
“These kinds of models are important to ensure that we’re not just doing the right thing conceptually but doing the right thing ecologically,” Ransom said.
One place researchers expect grizzly habitat to change with the climate is at higher elevations. As temperatures warm, plants grizzlies rely on will climb higher in elevation, displacing alpine areas. While that displacement will harm some species, it will increase high quality habitat for the bears.
“When we look at some bear foods marching up in elevation, at least theoretically, that should draw bears up in elevation. It’s also drawing good grizzly bear foods farther away from people,” Ransom said.
Grizzly bears are habitat generalists, Krosby said, which means the bears can move around and adapt more easily as the climate changes. Grizzlies also have a wide variety of foods in their diets and historically have large ranges, exposing them to different climate extremes, she said.
“Those often are the kind of species that fare better in a changing climate,” Krosby said. “They can move out of the way if there’s an impact. They can shift their ranges to track changing climates. If something that they eat becomes scarce, they can eat something else.”
To that extent, Krosby said, perhaps wide-ranging species generalists could be better candidates for reintroduction efforts as the climate changes because they are more adaptable.
A draft environmental impact statement on reintroduction efforts is expected this summer, after which officials will hold public meetings and public comment periods. A decision on a final environmental impact statement is expected in the spring of 2024.
CORRECTION 2/17: An earlier version of this story misstated the name of the journal where this study was published. The journal is Biological Conservation.