Forest Fire in Canada > Forest Fire Facts and Questions

Frequently Asked Questions About Forest Fires

Introduction

Forest fires are an important part of the Canadian landscape. This FAQ is intended to provide a basic understanding of wildland fires and their effects on the land.

Fire Basics
Role of Fire
Fire Suppression
Fire and Climate Change

Fire Basics

1. When is the forest fire season in Canada?

Generally, the forest fire season in Canada runs from April through to October. The most fires and the largest areas burned happen in June, July, and August.

2. How many forest fires occur each year?

During a typical year there are over 9,000 forest fires in Canada, burning an average of 2.5 million hectares (ha) or 25,000 square kilometres. The number of fires and area burned can vary dramatically from year to year.

3. What causes forest fires?

In Canada, two-thirds of all forest fires are caused by people, while lightning causes the remaining third. This varies across the country: lightning causes over 50% of fires in western Canada and the Northwest Territories but only 10% of fires in the Maritime provinces. Despite this, lightning fires account for over 85% of the area burned in Canada, largely because many of the lightning-caused fires occur in the West and North, where there are more remote areas that are difficult to reach with fire suppression equipment. Human-caused fires usually start close to communities, where they are reported quickly and dealt with by local fire crews.

4. How big do forest fires get?

Most forest fires are caught in the early stages before they have chance to grow. Under extreme conditions fires can grow rapidly, sometimes exceeding 100,000 ha. In Canada, approximately 2% of forest fires account for 98% of the total area burned.

5. Is there a way of telling if this will be a bad fire season?

Not really. Weather forecasts are reliable for only a few days, and long-range forecasting is still unreliable. The amount of snowfall that occurs during the winter can indicate how dry the forests may be at the start of a fire season, but this usually changes after the spring rains.

6. How fast do forest fires burn?

Most forest fires advance at a rate of less than 0.5 km/h, and few spread faster than 1 km/h. The fastest forest fires can burn at 6 km/h or more.

The speed that a fire burns depends on the type of trees and the amount of moisture in the forest. Coniferous (evergreen) trees burn 5 to 10 times faster than deciduous trees because of the resin in the bark and needles. Deciduous trees are more resistant to fire when the leaves are out.

7. How much heat comes off a fire?

As with the speed of a fire, the intensity of a fire depends on the type of trees and the amount of moisture in the forest. An average surface fire on the forest floor might have flames reaching 1 metre in height and can reach temperatures of 800°C or more. Under extreme conditions a fire can give off 10,000 kilowatts or more per metre of fire front. This would mean flame heights of 50 metres or more and flame temperatures exceeding 1200°C.

8. What about all that smoke?

Smoke rises from a fire in a plume consisting of liquids, gases, and particles of different sizes. The small particles in smoke, and ozone produced by the reaction of sunlight with gases in the plume, can easily pass through our noses into our lungs and cause health problems in children, the elderly, and people with heart or lung conditions.

The spread of smoke is affected by a combination of wind and air temperature. Dense smoke occurs when the winds are calm and the surface air temperature is cooler than the air above it, but when the air is unstable and windy, smoke can be carried thousand of metres up in the atmosphere or downwind from the fire. Weather features may even trap smoke in areas far from a forest fire, while regions close to the fire will have little smoke.

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Role of Fire

1. Are fires good or bad?

Fires are natural and play an important role on the Canadian landscape. Forest fires remove the mature trees in the forest that are the most susceptible to insects and diseases. Surface fires remove accumulated materials on the forest floor, promoting the growth of new seedlings. Some species of trees even rely on fire to open their cones and release their seeds to regenerate. Pioneer organisms (those colonizing immediately after fire) gain new habitat and become more abundant.

Fire is not positive for all species, however. Many birds, mammals, and insects are dependent on old growth forest and are displaced by fire. Several species of trees such as white spruce, balsam fir, and white cedar need longer intervals between fires in order to reach reproductive maturity and will not survive in an area that burns too frequently.

2. Why is the boreal forest often referred to as a forest shaped by fire?

Fire is a frequent disturbance in the boreal forest because of the combustible nature of the trees and a warm, dry climate that facilitates severe fire weather. Fires in the boreal typically kill most trees, and as a result the boreal forest is a patchwork of forest stands that reflect the time since the last fire. The species composition of plants and animals changes over time through a process called succession.

3. How often do forest fires occur?

The percentage of annual area burned within a region is often used to estimate the frequency of fires. If an average of 1% of an area burned each year for 100 years, the fire frequency would be estimated at 100 years. Fire frequency varies widely and depends on the location and the period over which it is calculated. For Canadian forests, historic fire frequencies can be as short as 10 years or as long as 1000 years. The boreal forest typically has a fire frequency of 50 to 200 years, fire being more frequent in the west and less in the east.

4. What is a fire-dependent species?

Species that need fire in order to replace themselves are fire-dependent. For example, jack pine need the heat from fire to open their cones or else seeds will not be released and the stand will not be renewed. If enough time passes between fires, other species may invade and eventually eliminate jack pine from the landscape.

5. What is prescribed burning?

Prescribed burning refers to the use of planned and controlled fires to reduce the built-up fuels in forested areas. This improves the health of an ecosystem and helps to protect the people living and working in forested areas as well as their homes and businesses.

6. Why do agencies start their own fires?

Prescribed burns can be used to reduce the build-up of surface fuels and reduce the risk of large fires starting later or to promote a natural landscape and habitat for wildlife. In some situations, agencies in Canada ignite fires to allow some fires to burn freely in order to promote beneficial ecological impacts or to meet other land management objectives.

7. Has there been a serious build-up of fuels in the forest?

Needles, leaves, and branches are highly flammable fuels and can increase the likelihood that a fire will be able to spread through an area if they have accumulated on the forest floor. If an area is fire-free for a long time, the build-up of these forest fuels could possibly increase the intensity of the next fire that occurs.

Some drier forest types, such as in the interior of British Columbia, had more frequent fire cycles in the past. Fire suppression along with logging and grazing practices have resulted in increased stand densities and greater potential for crown fires (fires that move through the upper parts of the trees). For many northern ecosystems there is sufficient fuel available for fire, and build-up is not an issue. A more important consideration is whether there are breaks between fuel sources or if they are continuous, which can determine the area over which a fire will grow.

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Fire Suppression

1. How much money is spent fighting fires in Canada?

Public agencies in Canada spend an average of over $400-million dollars a year on fighting forest fires. This figure varies from year to year depending on the region and the severity of the fire season. Because of Canada’s size and the nature of large-scale atmospheric motions, one or more regions of Canada can experience high levels of fire activity in any given year.

2. Do we try to fight all forest fires?

The current approach for fire management in Canada is that more than 90% of all fires are fought. As part of this approach, each province and territory assigns a priority to various areas that determines the level of fire suppression activity. High priority areas include wildland-urban interfaces (where communities are adjacent to forested areas), forests with a high commercial value, and recreational sites. These areas typically receive aggressive action to contain and suppress fires. Efforts in these areas represent the majority of expenses related to fire fighting.

Low priority areas such as wilderness parks and remote forested areas of limited economic value are monitored, but fires are fought on a limited basis unless they approach high priority areas. These fires represent the majority of the area burned in Canada.

3. How do you protect your house and community?

There are a number of simple and affordable methods to help homeowners reduce the risk associated with living in forested areas. These include clearing vegetation from around the home, building with fire-resistant materials, and identifying and dealing with risks before fire occurs.

Community protection requires a long-term, multi-disciplinary approach to reduce the risk of forest fire damage or loss. Public education, emergency response planning, hazard assessment, and land-use planning can all make a difference. Community protection is about minimizing the negative impact of fire on a community and preparing efficient and effective community responses when fires occur.

For more information about protecting your home and community, visit the Partners in Protection web site: http://www.partnersinprotection.ab.ca

4. How do sprinklers work?

Sprinkler systems are installed on houses and other structures in order to create a dome of humidity that will reduce the potential fire intensity and radiant heat from burning vegetation adjacent to the structure. The sprinklers will also change the moisture levels of the building and roof materials, making them less likely to catch fire from falling embers.

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Fire and Climate Change

1. Are we getting more fires due to climate change?

Fire occurrence varies greatly over time, and this variability makes it difficult to see any statistical trends over the last few decades that are caused by climate change.

Models that estimate the future climate indicate that conditions will likely be drier and warmer in the future throughout much of Canada. Under these conditions fire can be expected to increase in Canadian forests on the whole, with the area burned possibly doubling over the next century.

May 26, 2004