Canada’s forests are some of the largest in the world. They have enormous economic, cultural, environmental, and recreational value for Canadians of all walks of life. 
Forests clean the air, water and soil. They support abundant and important populations of plants and animals. They are a vital economic resource, sustaining a thriving wood, pulp and paper industry. They allow people to practice traditional hunting and trapping lifestyles, preserving culture and providing an essential food source in isolated and northern communities. They sustain a profitable tourism and recreation economy, offering rest, refuge, and adventure to both Canadians and visitors.
Our forests are also vulnerable to climate change. 
Ken Zielke has studied and worked in the forests of British Columbia for over thirty years “I’m a professional forester, and I’ve worked in the field off and on my whole career. I like to spend as much time as I can out there,” Zielke says. He recently retired as Director of Investigations for the BC Forest Practices Board, and is an expert in both sustainable forestry and the effects of climate change on forests.
The effects of climate change on Canada’s forests are already evident.
From Zielke's standpoint, climate change poses a variety of threats to Canada’s forests. Most worrisome are the potential for more destructive insect outbreaks, more intense and more frequent wildfires, and shifts in weather patterns that threaten our trees and the industries and communities that depend on them.
Moving forward, it is clear that we need to take steps to protect our forests and ourselves from what could be a climate catastrophe. “The first step is recognition that there’s a problem,” continues Zielke. “We need to start adapting.”
The effects of climate change on Canada’s forests are already evident. The mountain pine beetle has caused extensive forest damage in British Columbia and now threatens Alberta as well.  Forest fire seasons have become longer and more destructive, as illustrated by the massive 2016 Fort McMurray fire and the record-setting 2017 and 2018 British Columbia wildfire seasons.  And shifts in weather have started to cause die-back in sensitive species such as aspen that are facing increased drought stress and higher temperatures. 
Changing Forests Change the Climate
Worryingly, the threat posed by climate change to Canada’s forests also risks making climate change worse.
Healthy forests act as a huge storage system that keeps carbon out of the atmosphere (Read more about Greenhouse Gases). This means that as forests die, or are burned or logged, we are losing a powerful natural resource that’s been keeping climate change from getting even worse.
Terry Teegee is Regional Chief of the British Columbia Assembly of First Nations, Tribal Chief of the Carrier Sekani Tribal Council, and the former forestry coordinator for Takla Lake First Nation. For Teegee, “trying to get back some sort of balance into the imbalance of CO2 emissions” is an important challenge for forest management in the face of climate change. “The more forested land we leave up, the more carbon we can sequester in those trees.”
Protecting our forests will resist the worsening of climate change, and if we can mitigate the severity of climate change we will also protect our forests.
Read more: Insect Pests
In recent decades, unseasonably mild winters have unleashed extremely damaging and widespread insect outbreaks. The most well-known example is the mountain pine beetle. Formerly a local, minor pest, the pine beetle has suddenly become a major threat to forestry in BC and has started spreading east into Alberta. 
Ken Zielke says, with amazement, that “we simply haven’t seen anything like that before, in the province and perhaps in the world.” He says the pine beetle outbreak provides a “peek into the future,” of climate change, which is likely to offer “more of what we’re seeing right now, but worse”.
Historically, pine beetle outbreaks have been kept under control by autumn cold snaps or by long, cold winters. Unfortunately for BC and Alberta, twenty years of mild winters have failed to keep the beetles in check, leading to a huge population explosion. Additionally, longer and hotter summers are, for the first time, allowing the beetle to go through two complete breeding cycles per year, something Terry Teegee describes as “unprecedented”.
The same hot, dry conditions that allow the beetles to flourish can also make trees more susceptible to infestation. This double whammy of massive insect populations and vulnerable trees means that “you see a vast area being infested, faster and faster,” says Teegee.
Other forest pests will thrive in a warmer climate, too, including the spruce budworm and the forest tent caterpillar.  Zielke warns that other beetle infestations could well appear, including new pests spreading into the region for the first time as climate conditions change.
See our Forest Pests and Climate Change article to learn more.
Read more: Wildfires
Forest fires are a natural aspect of the forest life cycle. As Terry Teegee observes, “fire is an integral part of the forest.” Fires help clear litter from the forest floor, recycle nutrients back into the soil, open up gaps in tree stands to promote new growth, and kill invasive plant and animal species and forest pests. The heat from forest fires is even needed by some tree species – such as the Jack Pine – for reproduction.
Unfortunately, fires can also destroy huge swaths of forest, threaten human lives, and cause widespread risks to health, ecosystems, and the climate.
Rising temperatures are expected to increase the frequency, intensity, and extent of forest fires across Canada. This is partly because warmer temperatures cause more evaporation that dries out forests, making them much more likely to burn. Warmer temperatures also promote the formation of storms with lightning, which is responsible for igniting approximately half of all wildfires across the country. And warmer, drier spring weather has been extending the fire season, meaning that the fire danger starts earlier in the year. The effects of climate change on fires in Canada are likely already evident. “Today we’re seeing the result of climate change: we’re seeing a lot more forest fires,” notes Teegee.
See our Forest Fires and Climate Change article to learn more.
Read more: Weather shifts and extremes
“The forecast is wetter in the spring, wetter in the fall, longer, hotter, drier summers,” explains Ken Zielke, referring to global climate model projections for much of Canada’s forested zone. Each of these changes comes with its own set of problems for Canada’s forests.
Hotter and drier summer weather is a problem for our forests. “That puts a lot of stress on trees, and they shut down, they become quite dry,” says Zielke. Stress and dryness make them more vulnerable to diseases, pests, and fire.
In contrast, increased spring and fall precipitation increases flood risk. The combination of dry summer and wet fall/spring weather means that forests could experience both flood and drought conditions in a single year. Natural Resources Canada notes that changes in precipitation patterns are already causing widespread Aspen dieback across the prairies, and that this effect is expected to get worse with climate change. 
During winter, when many of Canada’s forests stand dormant, changes in temperature and precipitation can cause numerous ill effects. The loss of cold allows pests and diseases to flourish, while lower snow accumulation during warm winters means that shallow root systems are less insulated and can freeze. Mid-winter warm periods have already caused unprecedented die-offs of cedar because their root systems are activated by the warmth, only to be frozen and killed when colder temperatures return, Zielke reports.
Extreme weather events, increased variability in precipitation, and the risk of devastating pest outbreaks pose a serious challenge to the forestry industry. Zielke’s take on this is that “It’s a sustainability problem: it’s hard to keep that constant flow over time that foresters like to achieve when they manage forests. These kind of large disturbances just throw a huge monkey wrench into that kind of planning.”
Mitigation and Adaptation
Models can predict how future climate conditions will change, but forests are such complex ecosystems that it’s hard to know for sure how they will respond. Much research is still required to understand how Canada’s forests will respond to climate change. This means we should expect unexpected threats.
Zielke notes that “no matter what we do to try to understand and try to predict and forecast what might happen, we’re going to see surprises.” He argues that this should encourage us to improve the sustainability and resilience of our forests: “With uncertainty there is opportunity. We need to keep things more diverse. We need to keep things more resilient. We need to think and anticipate and be proactive in everything we do.”
Finding ways to reduce greenhouse gas emissions and slow climate change will help protect our forests and preserve their capacity to defend against and survive climate change. The National Round Table on the Environment and the Economy identified three cost-effective strategies that can help manage climate change risks in Canada’s forests :
- enhance fire protection, control, and suppression
- increase pest prevention and control measures
- plant tree species suited to conditions of climate change
As with so many impacts of climate change, the measures that can be taken to address threats can seem daunting. In the long run, however, taking action now is both cost-effective and absolutely necessary, especially to preserve a resource as important as Canada’s forests.
The need for change is clear to Zielke and Teegee, who have both seen growing threats to the forest with their own eyes. Zielke argues that the disruption promised by climate change “challenges sustainability, and I think in doing so puts the importance of sustainability at the forefront in everything that society’s going to start thinking about. Not just forestry, but almost everything.” Teegee thinks about our responsibility in generational terms: “the following generation, they have to live with our legacy; we have to live with our previous legacies, what we inherited”. He concludes: “the good thing about human beings is that we’re resilient; we’ll make change”.
- Natural Resources Canada. “How do forests benefit Canadians?”
- Natural Resources Canada. “Climate change: Impacts”.
- Natural Resources Canada. “Mountain Pine Beetle”
- University of Alberta news article. "Attack of the pine beetle"
- British Columbia Wildfire Service. “Wildfire Season Summary (2017)”
- CBC news. “2018 now worst fire season on record as B.C. extends state of emergency”
- Natural Resources Canada. “Changing climate, changing forest zones”
- Haynes, Kyle & Allstadt, Andrew & Tardif, J. (2014). “Effects of climate change on forest tent caterpillar outbreak dynamics based on a century of tree-ring data.”
- National Round Table on the Environment and the Economy. Paying the Price: The Economic Impacts of Climate Change for Canada http://nrt-trn.ca/climate/climate-prosperity/the-economic-impacts-of-climate-change-for-canada/paying-the-price