Dr. Barry Cooke has had something to get off his chest for several years now.

The research scientist says he and his colleagues at the Canadian Forest Service have been growing increasingly worried about what climate change is doing to trees in the North.

So this week, against the backdrop of a political debate around the Liberals' carbon tax and rebate scheme, Cooke took "a big breath" and fired off 75 tweets about "drunken trees" and browning forests in Canada's North.

"We see these compelling images of trees dying over large areas and it's fairly frightening," he told Day 6 host Brent Bambury.

43. As bad as the situation is today, it's really only started. Big change is coming. <a href="https://t.co/FVKmmiZWZY">pic.twitter.com/FVKmmiZWZY</a> —@barryjcooke1

Cooke's worries began in 2013 when his colleague Roger Brett, who had been doing field research in the Northwest Territories, returned to their office looking upset.

When Cooke asked Brett if he was all right, Brett showed him a series of pictures.

"He said, 'You know those spots of forest decline that we were seeing a little bit around Norman Wells and a little bit around Fort Smith? They're growing. They're getting bigger and bigger and it's just a little bit disturbing.'"

When Cooke saw the pictures, he says he also became uneasy.

"He was upset and he upset me as he went through slide after slide after slide. I was like, 'Wow.'"

Browning forests and 'drunken trees'

About 40 per cent of Canada is covered in trees. In the North, two factors in particular are leading to forest decline, Cooke said.

Low-lying trees like black spruce are falling over because of too much moisture at their roots due to melting permafrost, leading to what Cooke calls the "drunken trees" phenomenon.

On drier, gravelly slopes like the Rocky Mountains, trees are still standing — but they are browning.

Dr. Barry Cooke says tall trees are faring worse in a warmer climate in Canada's North. (Ho-Garth Lenz/The Canadian Press)

"These sites are more exposed and so the warmer, drier air conditions are drying out leaves," Cooke said.

"Trees like it just right, sort of in a Goldilocks-type situation."

What's worse, Cooke says, is that taller and older trees are faring worse in these drier areas.

"Tall trees are designed to pump water from the ground up to the tips of the tops of the trees and when they can't do that, then those top tissues desiccate. They dry out," Cooke explained.

It's not enough to fly a satellite over planet Earth and say … 'How's the Earth doing?' - Dr. Barry Cooke, research scientist at the Canadian Forest Service

Shrubs, on the other hand, tend to do better because they don't have to pump water very high.

In addition to being an integral source of timber for Canada's natural resources industry, tall trees are also a source of biodiversity, Cooke said.

Aerial view not always accurate

The face of climate change in Canada's north is melting ice, not dying trees. That's partly because a satellite view would lead people to believe that the north is still green, according to Cooke.

In fact, he says there's a narrative out there that a warming climate has made forests greener.

In the 70s, 80s and even 90s, that was true, Cooke said. But it's no longer the case.

Aerial views may show more lush green areas, he says, but that picture tends to miss the browning tall trees.

39. On the ground, what you see in alpine regions is a browning that does not appear in decadal studies of satellite imagery. Satellite imagery is imprecise. Ever heard of the phrase "ground-truthing"? <a href="https://t.co/Z2Qs4s7lAf">pic.twitter.com/Z2Qs4s7lAf</a> —@barryjcooke1

"When you look at the planet from a satellite you see one thing. When you look from an airplane, you see another thing, [and] when you're on the ground and walking through the woods, you see different things," Cooke said.

"The closer you get, the more you can start to see early signs of browning and mortality. So it's not enough to fly a satellite over planet Earth and say … 'How's the Earth doing?'"

Indirect impact of climate change

While browning and falling trees are the direct result of climate change, Cooke says forests are also facing indirect consequences of a warming planet.

Once-innocuous insects and disease are becoming more dangerous to trees, he said, adding that invasive species also pose a great threat to Canada's boreal forest.

41. Jasper National Park has lost the battle of the pine beetle. We saw it coming in 2008. We knew it was hopeless even before it started in 2012. <a href="https://t.co/9CNhRrByGb">pic.twitter.com/9CNhRrByGb</a> —@barryjcooke1

Cooke worries the decline he is seeing in the North may spread to the other parts of the country.

While he and his colleagues have discussed their concerns about trees internally, sometimes he says it feels like "we're talking in a closet of like-minded people."

"We're not really talking to Canadians," he said. "We haven't really taken the case to Canadians at large saying, you know, 'Your North is changing, folks.'"

To hear the full interview with Barry Cooke, download our podcast or click the 'Listen' button at the top of this page.

