Drier, warmer climate impeding forest regeneration, research shows

Forests are defined by their resiliency, their ability to regenerate after fire rips through the landscape. That image isn’t just familiar to the news cycle — it’s a natural cycle.

“Forests are used to burning,” University of Guelph ecologist Merritt Turetsky told CTVNews.ca. “They have been burning for 5,000 years since fire came into the landscape.”

But a growing body of research suggests humans are messing with that resiliency. “What we’re doing as a result of human climate change is we’re really whacking that resilience cycle,” she said

Forests are drier than they’ve ever been and the forest fires that typically have allowed them to regenerate are burning more intensely than ever, instead leaving soil conditions too stressful for seedlings to grow.

“We’re pushing these forests into new climate scenarios,” she said.

The research supports her claims. In a new study published in the journal Ecology Letters in December, U.S. researchers looked at 1,500 forests impacted by more than 50 wildfires across the Rockies over a 30-year period beginning in 1985.

Regrowth was less common after the year 2000 than before because of warmer and drier conditions. The study, led by Camille Stevens-Rumann at Colorado State University, found there was no regrowth at about 500 of the sites, or a third of the 1,500 analyzed in the research.

Though the study looked at an American ecosystem, Turetsky says there are parallel findings and concerns for the Canadian boreal forest. Indeed, Natural Resources Canada says climate change will result in more frequent wildfires as “fire-prone conditions” increase across the country.

With drier conditions and more intense fires, the soil is often burned down to the bedrock.

“It’s literally removing all signs of life,” said Turetsky. “It’s really hard for plants to regenerate on that kind of stressful soil.”

The effects are two-fold, she says.

First, the impact on “Northern ways of living,” as witnessed in the Fort McMurray fires that ravaged North Alberta in 2016, with billions of dollars in estimated damages.

Second, the long-term effects on Canada’s boreal forest, defined by coniferous trees but seeing more deciduous growth with the new conditions. This could have broader impact than simply what trees Canadians see.

“If we see a shift from coniferous to deciduous in general that will mean the boreal biome will store less carbon. That carbon is going to end up in the atmosphere,” she said. “What happens in our Canadian forests doesn’t stay in our Canadian forests. It effects the whole climate system.”

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