Scientists produce forecast of boreal caribou habitat change

New projections map where boreal caribou habitat may be and how populations may change until 2100 as the climate warms.

A new study focuses on five boreal caribou monitoring areas in the NWT’s Taiga Plains, a 50 million-hectare expanse in the western part of the territory.

The projections could be used to inform land management and conservation planning for the species.

Boreal caribou are listed as threatened both territorially and federally. In 2019, the territorial government pledged to develop five regional range plans that will lay out how to manage boreal caribou habitat. The work is scheduled to be completed in 2023.

A variety of disturbances negatively affect boreal caribou, such as roads, logging and seismic lines. Natural disturbances are also expected to have an important impact on the animals, especially as warming progresses in the North.

Biologist Frances Stewart, the Canada Research Chair in Northern Wildlife Biology at Wilfrid Laurier University, said climate change “will be a big factor” but researchers largely lack detailed projections of how habitats and populations may change as the climate warms.

Although people use weather forecasts in their everyday lives to decide how to dress or plan activities, Stewart said: “We don’t really have those same tools for deciding what we do with our land and the species that live on the land.”

To that end, Stewart and her colleagues are working to predict where species are going to be in the future, with and without climate change.

She said the work goes back roughly 10 years, when Stewart’s supervisor, Eliot McIntire, started putting together computer algorithms to produce ecological forecasts.

Stewart and her colleagues have since been able to make forecasts for several species, including more than 70 boreal bird species and boreal caribou.

The forecasts for boreal caribou suggest that suitable habitat will decline in the southern and northwestern regions of the Taiga Plains, whereas habitat might increase in central and southwestern areas.

Despite these changes in habitat, population growth rates are not expected to change, the researchers reported in February in the journal Ecological Applications.

“It’s nice not to have a catastrophic paper come out,” said Laura Meinert, a wildlife management biologist with the Wekʼèezhìi Renewable Resources Board, who was not involved in the research.

Although predictions for many species aren’t so rosy, Meinert said the forecast for boreal caribou in the NWT is not necessarily bad news.

“I think it shows how strong the range is here,” she said, “and how much it’s worth protecting for future generations.”

Meinert added that the paper’s northern focus makes the findings more applicable.  

“A lot of the time, as biologists in the North, we get papers from southern Alberta or Wisconsin or Norway, and we have to think, ‘OK, how can I extrapolate that to work here?’ This is work done on the Northwest Territories’ range with the boreal caribou, which is fantastic,” she said.

Northern shift

To create the forecasts, Stewart and her colleagues first took information from global climate models and fed it into two other models – one that looks at how forests change and one that looks at how wildfire moves through forests.

Stewart said the climate, forest and wildfire components essentially “swirl around each other” to produce maps of what the Taiga Plains will look like on an annual basis.

The team then integrated this information with models of population growth and habitat selection to determine where caribou will be, and how their numbers may change, based on coming alterations in forest and wildfire patterns. They also quantified the uncertainty associated with anticipated changes, which is rarely done, Stewart said.

The research revealed suitable habitat is expected to decline slightly in the Taiga Plains, although focusing on specific areas highlights important differences. Suitable habitat is expected to increase in the Gwi’chin Settlement Area and the north of the Dehcho region, the team reported. In the Hay River Lowlands and southern Dehcho, boreal caribou habitat is expected to decrease.

“We’re generally seeing a northern shift in boreal caribou habitat across the Taiga Plains,” she said.

The forecasts don’t point to major changes in population growth rates. Stable herds are expected to remain so and those slightly declining are projected to continue on that track, Stewart said, although she acknowledged a lot of uncertainty in these results.

What might explain the changes ahead? Most regions of the Taiga plains will see a conversion from coniferous to deciduous forests over time, according to the forecasts. Stewart said that wildfires are also a major factor. Boreal caribou generally select old forests or very young forests that recently burned. The animals typically aren’t seen in areas 20 to 40 years after a burn, she said.

With climate change, the amount of area burned and the number of wildfires are anticipated to increase. This means the location of caribou habitat and when it is used may shift, Stewart said.

Although fire will have a huge impact on the North, Stewart said “a real critical take-home, I think, is that there will be the habitat … It’s about recognizing where that habitat will be so that we can really focus on conserving it now.”

According to Meinert, the forecasts may be used in the Wekʼèezhìi boreal caribou range plan, which is currently in an interim state and will be finalized this year.

Stewart said the projections could prove useful in other range plans too.

Peter Redvers, who leads negotiations and consultation for the Kátł’odeeche First Nation, was previously KFN’s director of lands and resources and has been involved in research looking at preferred boreal caribou habitat within the First Nation’s territory.

Redvers said KFN has also been actively involved in the working group developing a range plan for the southern NWT.

“We’ve been having to deal with some of the more immediate impacts,” Redvers said, such as clear-cut logging in northern Alberta and existing climate change effects. He said warm spells during the winter, for example, can cause ice crusts to form in the snow, which makes it harder for caribou to walk, feed and evade predators.

Redvers said the new study “adds that extra dimension, which is helpful.”

“Ultimately, what it all means is that we have to take actions now to ensure that we’re not putting undue pressure on the boreal caribou populations,” he said. A decline in suitable boreal caribou habitat in the region around KFN would be a loss, he said, but ensuring that more immediate impacts don’t harm populations might help caribou handle longer-term changes.

One of the study’s limitations, according to the researchers, is that human-caused disturbances are treated as static over time.

“They say they can’t predict where things will be in 100 years,” Meinert said. Still, she thinks it would have been useful for the team to plop a hypothetical mine or road onto the map to compare the magnitude of a human-caused disturbance to that of climate change.

Stewart also points out that the researchers were only able to model changes in forests, even though boreal caribou are known to use other landscapes.

“This is definitely just a starting point,” she said.

The forecasting framework is open code, she said, so anyone can look at it and add to it.

“If they have other information or knowledge types that we haven’t incorporated to date, we can do that later on and update the forecast,” she said, adding that the team would like to hear communities’ assessments of the projections and include Indigenous knowledge in a future iteration.

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This article is produced under a Creative Commons CC BY-ND 4.0 licence through the Wilfrid Laurier University Climate Change Journalism Fellowship.