Less snow, more rain affecting Labrador caribou, as new study details climate change impact

A new study compiling decades' worth of data details a portrait about how climate change is affecting Labrador's herds of boreal caribou, and calls for more research to manage the species' conservation for years to come.

The study sprang, in part, from researchers questioning why most of the Big Land's boreal herds were shrinking when human disturbances to their habitats were less than in other boreal caribou ranges elsewhere the world.

The Red Wine herd was estimated at just 20 animals in 2015, with hunting considered a primary factor.

Boreal caribou like the Red Wine herd live below the treeline, and don't migrate vast distances like their roaming cousins in Labrador, the George River caribou herd.

"Surprisingly, the survival rates were less than expected," said one of the study's authors, ecologist Isabelle Schmelzer, "and this is one of the reasons we wanted to look into the influence of climate."

The researchers sifted through years of caribou data, much of it culled from radio collar tracking and some of it reaching back to the 1980s, as well as collecting climate data from satellites to understand the changing Labrador landscape.

"This is one of the first occasions in which we've been able to pair these two sources of information together to ask these questions," Schmelzer told CBC Radio's Newfoundland Morning.

While the study noted hunting is a factor exacerbating population decline, its focus remained on climate-related mortality.

Less snow, more rain

While climate change is complex, the study found several factors that could be affecting caribou.

"What we found is that yes, all the ranges were warmer, ubiquitously, and snowfall levels were less. I know it might seem hard to believe when you're shovelling it, but they are in fact less ... that may actually be exerting a negative pressure on survival rates," said Schmelzer.

Extremely deep snow is a part of Labrador caribou's daily life in winter, and while it can seem counterintuitive for that to be a good thing, Schmelzer said those depths actually keep wolves — their main predators — away.

Less snow gives wolves easier access to one of their favourite meals, and mortality in turn rises.

Increasing amounts of freezing rain in the fall are also not working in caribou's favour, as Schmelzer said that ice coats vegetation, and "makes it very difficult for caribou to access the forage below," she said.

"To make matters even worse, it often results in the growth of a fungus that produces a toxin, that is quite bad for caribou."

Schmelzer did note that as the climate continues to warm in Labrador, there may yet be unintended benefits from longer growing seasons, but it also brings with it increasing amounts of insects "that plague caribou and affect their behaviour."

The provincial government's data shows that by mid-century, winters in Labrador will be on average between six and seven degrees warmer, with summers almost three degrees warmer, increases much larger than what's expected for the island.

'The lifeblood of Labrador'

One key point the researchers found "very unusual," said Schmelzer, was that they found the survival of adult female caribou was being affected. Once females make it to adulthood, Schmelzer said, they usually live for a long time, with calves the most vulnerable part of the herd. To find adult females dying "is very significant," she said.

She said that caribou are a species whose survival is intricately tied to the landscape.

"Caribou are part of the lifeblood of Labrador. they are at the root of so many different ecological processes," she said.

The study concludes with a call to action, stressing that "these remaining, relatively intact northern ranges are vital to caribou recovery in Canada and are fundamental for the assessment of natural determinants of adult female caribou survival."

The study recommended more research to better understand what's happening to boreal caribou and plan for ways to manage their future conservation.

Schmelzer said caribou have thrived for more than 40,000 years and adapted to changing landscapes before, although perhaps never as rapid as this.

"We know that they have the capability, but there are increasing challenges that they face throughout their ranges and their landscapes, and of course it's my hope that we can continue to see them for many thousands of more years," she said.

"I'd love to see them recover."

The study has been published online as part of the September issue of the journal Global Ecology and Conservation.

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