Glass domes help forecast the fate of Canada's boreal forests

The boreal forest is Canada's first line of defence against climate change, but warming temperatures could soon put our greatest carbon sponge at risk.

Black spruce, one of our country's most common boreal tree species, will be smaller in future climate conditions, according to Western researchers.

"When you increase growth temperatures, basically what you find is a decline in growth in the species," said Professor Danielle Way, a plant biologist at Western University.

Her work is just one component of the SPRUCE initiative, a massive environm​ental research project based out of Minnesota's Oakridge National Labs.

Like a climate time machine, the SPRUCE project is using huge glass enclosures to simulate climate conditions a century from now. Half remain at current conditions, and half are being tested at varying stages of global warming.

"You can look at everything from what does current vegetation look like, all the way up to what would a plus-nine-degrees-Celsius, high-CO2 world look like," Way explained.

Their findings are concerning because boreal trees filter massive amounts of carbon dioxide out of the air, most of it in the wood of living trees and the chilled corpses of fallen trees.

"It doesn't decay very fast because it's cold. And so, you lock up a lot of carbon in the landscape," Way said.

Right now nearly 11 per cent of the planet's carbon is locked up in the forest, or about 208 billion tons. But as the boreal forest warms, more carbon could remain in the atmosphere.

"Declines in its performance and its growth, in its ability to hold carbon and sequester carbon, could really mean big changes in our ability to absorb carbon out of the atmosphere," Way said.

A forest in the balance

The success of the SPRUCE initiative is crucial because the boreal forest is an essential ally in helping us reach our Paris Agreement climate targets.

"We basically are counting on, partly on our forests to help meet our requirements to compensate for the CO2 that we're emitting."

And if projected climate trends come true, we could instead get locked into a dangerous process called climate change positive feedback.

That's where the consequences of global warming cause it to self-accelerate.

"It's almost like a runaway train," Way said.

Put simply, the less carbon that ends up in the boreal forest, the more greenhouse gases and more global warming. Then the trees get even weaker and the cycle continues.

But other aspects of the forest could help temporarily keep the ecosystem in balance.

Unlike black spruce, tamarack trees seem unfazed by the higher temperatures and carbon dioxide concentrations.

"It's able to acclimate or adjust its performance so that it can maintain its performance to absorb CO2 from the atmosphere," Way explained. "It uses the carbon in that CO2 to build its tissues and that's why you can maintain growth."

A separate SPRUCE study also recently found that, while global warming gives boreal plants a longer growth season, so far, it hasn't been able to make up for the slower black spruce growth observed.

"My guess is that you're still going to overall have negative effects of the warming on feedback from the climate system," Way said.

"I think you might end up really getting a transition from the type of forest we see now to, instead, species that are, for example, deciduous."

Species like poplar that survive better under warmer conditions, replacing Canada's iconic boreal trees.

And the ever-growing threat of forest fires - more frequent and destructive than ever - further threaten the boreal forests along with pests.

"On top of that, the increasing temperatures mean that you get more severe outbreaks of insect pests that defoliate everything. In other words, they eat all the leaves," Way said.

In the end, SPRUCE will follow these trees through 20 years of their lives, and Way intends to stick with the project until they have complete answers.

"I plan to stay involved for as long as I can during that time period to see how the ecosystem changes over that time," Way said.

"I'm really excited to see what we get over the next few years - excited but also a little worried."