Fire in the forest
A wildfire is an uncontrolled fire that burns through forests, grasslands or other natural areas. Canada has about 8000 wildfires in an average year, burning over 2 million hectares. Some years are much worse. In 2023, Canada had its most destructive wildfire season on record, with more than 15 million hectares burned and smoke drifting as far as Europe.
The fire triangle
Every fire needs three things, called the fire triangle:
| Part | Source in a forest |
|---|---|
| Heat | Lightning, sparks, campfires, cigarettes |
| Fuel | Dry grass, leaves, branches, trees |
| Oxygen | The air |
Remove any one side, and the fire goes out. Firefighters do this by cooling with water (heat), clearing fuel to make firebreaks (fuel), or smothering with dirt or foam (oxygen).
What starts wildfires?
| Cause | Share in Canada |
|---|---|
| Lightning | About half of fires, but most of the area burned (they often start in remote places) |
| People | About half: campfires, cigarettes, sparks from equipment and vehicles, burning debris, arson |
What makes fires spread?
| Factor | Effect |
|---|---|
| Dry weather and drought | Dry fuel burns easily |
| Hot temperatures | Fuel dries out faster |
| Wind | Brings oxygen, pushes flames forward and carries burning embers far ahead |
| Steep slopes | Fire races uphill as flames preheat the fuel above |
| Type of fuel | Conifers with resin burn intensely |
Types of forest fires
| Type | Description |
|---|---|
| Ground fire | Smoulders slowly underground in peat and roots; hard to put out and can survive winter ("zombie fires") |
| Surface fire | Burns grass, shrubs, fallen leaves and branches; moderate intensity |
| Crown fire | Spreads through the treetops; very intense, fast and dangerous |
Large crown fires can create their own weather, including towering pyrocumulonimbus clouds and lightning.
Fire as part of nature
Fire is a natural and important part of many ecosystems, especially Canada’s boreal forest.
Benefits of natural fire
- Clears dead material and returns nutrients to the soil
- Opens space and sunlight for new plants
- Controls insects and diseases
- Creates a patchwork of young and old forests, which supports more kinds of wildlife
Fire-adapted plants
Many plants are fire-adapted:
| Plant | Adaptation |
|---|---|
| Jack pine and lodgepole pine | Cones are sealed with resin that melts only in high heat, releasing seeds after a fire |
| Trembling aspen | Sprouts quickly from roots after fire |
| Fireweed | One of the first plants to bloom after a fire; it’s Yukon’s territorial flower |
| Ponderosa pine and Douglas fir | Thick bark protects them from surface fires |
Ecological succession
After a fire, life returns step by step. This is ecological succession.
- Fireweed, grasses and wildflowers sprout within weeks.
- Shrubs and fast-growing trees like aspen follow.
- Pine and spruce gradually return.
- Over decades to a century, a mature forest grows again.
Animals like woodpeckers move in to feed on insects in burned trees, and moose browse on fresh plants.
Fires and people
Dangers
- Destroyed homes and towns (Fort McMurray, AB, 2016; Lytton, BC, 2021; and Jasper, AB, 2024, where fire destroyed about a third of the town’s buildings)
- Smoke, which harms lungs and hearts, especially for children, older adults and people with asthma
- Evacuations of whole communities
- Loss of timber, power lines and roads
Fire management
| Strategy | How it works |
|---|---|
| Fire detection | Lookout towers, aircraft, satellites, lightning detectors |
| Firefighting | Ground crews, water bombers, bulldozers making firebreaks |
| Prescribed burns | Planned fires in safe conditions to reduce fuel |
| FireSmart | Clearing brush and choosing fire-resistant materials around homes |
| Indigenous cultural burning | Many Indigenous peoples have used small, controlled fires for thousands of years to manage land; this knowledge is now helping guide modern fire management |
Climate change and wildfires
Warmer temperatures, longer fire seasons and more frequent droughts are making large wildfires more common in Canada. Scientists expect fire seasons to keep getting longer and more intense.
Preventing human-caused fires
- Follow fire bans.
- Keep campfires small, never leave them unattended, and drown them with water until cold.
- Don’t throw cigarettes from vehicles.
- Report fires immediately.
Common mistakes
- Thinking all forest fires are bad. Fire is natural and necessary in many forests.
- Thinking a campfire is out because flames are gone. Embers can stay hot for hours.
- Thinking wildfires only start from lightning.
Try it yourself
- Draw the fire triangle and explain how firefighters remove each side.
- Research a jack pine cone. Why does it need fire to open?
- Check your area’s current fire danger rating and explain what it means.
Quick recap
- Wildfires need heat, fuel and oxygen: the fire triangle.
- Lightning and people each start about half of Canada’s wildfires.
- Fire is a natural part of many ecosystems; some plants depend on it.
- Forests recover through ecological succession.
- Climate change is making wildfire seasons longer and more severe.