The Essential Forest
The globe’s boreal zone is under siege. In Canada, home to more than 30 per cent of it, what’s happening in the woods — and what needs to happen? Plus: what YOU can do
The globe’s boreal zone is under siege. With Canada home to more than 30 per cent of it, here is what is happening, what needs to happen… and what you can do
The North American boreal forest is home to some tough characters: the elusive and ferocious wolverine, the cunning wolf and the powerful grizzly bear. But one of the toughest of them all is the boreal chickadee. Weighing in at around 10 grams, this small, roundish bird doesn’t fly south when the mercury falls but instead puffs up its downy chest and takes winter on the beak. Staying warm comes at a high energetic cost, though — it must feed daily on food caches to survive, as it lacks sufficient fat stores to survive prolonged cold snaps. On chilly winter nights, it slips quietly into torpor to conserve more energy still.
Sure, winter is tough, but the boreal chickadee can handle it. It’s what scientists call a boreal-obligate species — an animal so highly adapted to habitats in the boreal forest that it can survive only within them. And for thousands of years, it’s been doing just fine. However, there’s a wrench in the evolutionary plan. As climate change takes hold, the boreal is changing — perhaps faster than this tough little bird can adapt. The past decade has ushered in some of the hottest and driest conditions on record, and climate models predict temperatures will continue to rise. From research on the ground to the analysis of satellite images, scientists are working to understand the implications of these changes for the species that live there.
The boreal is Earth’s largest forest, a circumpolar ecosystem that blankets roughly six million square kilometres in North America — much of Canada and Alaska. Vast tracts of spruce, fir, larch and pine dominate this great expanse, taking up carbon from the atmosphere and providing homes for the bears, wolves, wolverine and cougars that weave the deep trees to hunt deer, moose and caribou. The melancholy call of the loon can be heard drifting across a multitude of lakes across the country. Boreal toads, beavers and massive flocks of migratory birds all depend on the wetlands that also filter water and hold back floods.
Though we speak of it as one big forest, the Canadian boreal is made up of eight ecozones, each of which possesses unique characteristics. In some places, symphonies of songbirds call from great stands of aspen, while in others, stunted spruce grow more sparsely before giving way to the Arctic. To understand how the boreal forest is changing is to investigate in multiple places, at multiple scales.
Scott Goetz, a professor at Northern Arizona University, is the lead scientist for NASA’S Arctic-boreal Vulnerability Experiment, known as ABOVE. One of the many things its
scientists are studying is how boreal vegetation is changing. For example, how will increasingly longer fire seasons and larger, more severe fires change the forests of the future, and how will that affect the carbon cycle?
In a 2015 study, Goetz and colleagues measured the carbon emissions released from the massive wildlife fires in 2014 in the Northwest Territories: 2.9 million hectares burned in what Ernie Campbell, deputy minister of the environment and natural resources for the N.W.T., called “the most intense fire behaviour seen by this generation.” The team estimated that 94 million tonnes of carbon was released into the air — more than half the amount of carbon estimated to be taken up by the entire Canadian boreal forest in a year. Though the release of carbon through fires has been a natural part of the Earth’s carbon cycle for thousands of years, as the Earth warms, more frequent “big fire” years could become part of a feedback loop that amplifies climate change.
It’s not just carbon emissions from fire that can affect climate, but how fire changes the landscape. “What we see in fire-disturbed areas, especially when they are severely burned, is that they switch from being an evergreen forest to a deciduous forest,” says Goetz. “Generally, the more severe the fires are, the longer the deciduous forests persist.” The dark coniferous trees of the boreal “absorb a lot of energy from the sun, and they hold that energy in a way that’s different from a deciduous forest,” says Goetz. Deciduous forests take up more carbon from the atmosphere and also reflect more sunlight. These changes affect the Earth’s energy budget — a key driver of climate.
Fire is only one of the symptoms of increasing temperature. Drought, insect infestations and disease may also become more prevalent in some areas, contributing more significantly to tree mortality. By studying 30 years' worth of satellite images documenting tree growth patterns, Goetz and colleagues have found there are early warnings that a forest is heading for this kind of distress. Patterns of decreased growth rate often precede tree death by several years — even decades. And while some boreal forests are showing increased growth rates from recent warming, Goetz’s analysis suggests the opposite is true for areas in central Alaska and central-western Canada, where “it’s pretty clear [growth rate] is declining.”
The past decade has ushered in some of the hottest and driest conditions on record, and climate models predict temperatures will continue to rise
Nowhere is this trend more apparent than at the southern edge of the boreal, where warming is most pronounced and the ecosystem is the most vulnerable. “When you get multiple hot years within a decade, you start to see much higher tree mortality,” says Goetz.
It’s not just the trees that are losing ground. The range of many boreal-adapted species is receding in the south. Ecologist Dennis Murray, of Trent University, is part of a team of scientists that recently developed models to help predict how suitable current boreal environments will be for 12 key boreal-obligate species, including caribou, moose, spruce grouse and boreal chickadees, in the next 60 years. Their work shows that most species’ ranges will get smaller and shift northward over time, but, says Murray, “There’s an endpoint as to how far north [a species’] range can expand.” For example, he says most northern soils are not conducive to the growth of large trees. “The entire forest will be constrained in terms of its northward migration. Meanwhile, southern recession has no constraints, so the forest will shrink over time.”
This squeeze between north and south will be felt more intensely in some areas, like what Murray calls the Ontario-quebec bottleneck, a region that straddles the provincial border just south of James Bay. “In the future, that area will be extremely affected by climate change, to the point where moose and other animal populations will become disconnected in that zone.” Some, like the winter-hardy boreal chickadee, may find that by 2080, there’s no suitable habitat in this region at all.
The boreal is Earth’s largest forest, a circumpolar ecosystem that blankets roughly six million square kilometres
As critical connection zones are pinched off, the models predict habitat will become more fragmented. “Essentially, some areas of the boreal forest will become inhospitable to [most boreal-obligate] species, creating disjunct populations,” says Murray. As boreal species move out, other species better adapted to new conditions will move in. “We’re going to see a dramatic change in species composition.” Murray says we need to continue to invest in the collection of data to further refine models and better understand what will happen at a fine scale.
Ecologist Erin Bayne, of the University of Alberta, agrees. He studies everything from worms to wolves but is known especially for his work on how human activities affect boreal birds. He has also helped develop models to predict the effects of climate change on the boreal, some of which he says are “very sobering, and very scary.” But he is also careful to point out that models have limitations — they are meant to be used as planning tools, not necessarily the last word. “We are trying to identify places on the landscape that are going to be more resistant to change,” he says, and with birds, this might mean looking in more northern locations, in very specific places.
Right now, a lot of the data used to assess boreal bird status is collected in the southern part of their range, Bayne says. It’s not good news. “Over the last five years, a number of species that call the boreal their home have been listed by the Committee on the Status of Endangered Wildlife in Canada as species of concern.” These include the Canada warbler, olive-sided flycatcher and common nighthawk.
And yet, by looking further north, Bayne and his students recently found what is thought to be one of the largest populations of common nighthawks in the world. The birds are hunkered down in a burned area, just north of the oilsands mines, near Fort Mcmurray, Alberta.
The question now, he says, is whether or not this group of nighthawks has been in the area for a long time, or if he has found a southern population that
Snow-melt pools linger in the boreal forest near Saskatoon, Saskatchewan. Opposite: the hardy boreal chickadee
New growth after a forest fire in NWT. Opposite: boreal fixtures moose and spruce grouse
Human development and resource exploitation is a leading cause of boreal deforestation