Forest fires are powerful and destructive forces of nature, capable of consuming vast areas of land in a short period of time. Understanding how these fires start is crucial for preventing them and protecting our communities and natural habitats. In this blog, we’ll explore the various ways forest fires ignite, from natural causes like lightning to human activities such as campfires and discarded cigarettes. By learning about the origins of forest fires, we can better appreciate the importance of fire safety and take steps to reduce the risk of these devastating events.

How do most forest fires start?

In BC, natural causes are responsible for approximately 60% of wildfires. In most cases, these fires are caused by lightening strikes. Accross Canada, this percentage falls to just under 50%. Because so much of BC is forested and remote, we see a higher ratio of naturally caused fires than in other areas of the country.

The remaining fires are caused by humans. This kind of fire is often started by:

• Campfires or debris piles burning out of control
• Campfires being left unattended before they are completely extinguished
• Discarded, lit cigarettes
• Arson
• Sparks from machinery and industrial equipment
• Fireworks

Lesser known causes of wildfires

While they are less well known, there are a few causes of forest fires that are just as dangerous as their more publicized cousins:

Discarded glass: throwing a glass bottle on the side of the road is not only littering, but creates a fire hazard. The curved glass of the bottle can refract sunlight, concentrating it into a single point – just like a magnifying glass. If the point of light falls on dry grass or other kindling, it can catch, starting a fire.

Volcanos: It’s not a common occurance in Canada – but spreading lava from a volcanic eruption can quickly ignite anything it comes into contact with, starting large forest fires quickly.

Spontaneous combustion: While spontaneous combustion may sound a little ‘out there’ it’s actually surprisingly common. Spontaneous combustion is usually caused by improper storage of substances with low ignition temperatures. Eg hay, straw, peat, etc. When these are stored in large quantities, heat created by bacteria, or by oxidization can build up. Many of these materials are good insulators, so the heat is created faster than it is lost. This can lead to spontaneous combustion that will quickly spread to the rest of the pile. This is a common cause of naturally occuring coal seam fires.

Electrical malfunctions: Faulty or fallen power lines can spark, igniting nearby vegetation.

Firehawks: While not native to Canada, a group of birds collectively known as firehawks cause a lot of wildfires in Australia. The birds pick up burning sticks and drop them in uneffected areas to flush out prey. 

How do authorities know the causes of a fire?

By tracing evidence left in a fire’s wake, authorities can often deduce the origin point of a fire. Once they find the origin, they can look for signs of what may have caused it. A ring of stones, for example, might indicate a campfire, or a discarded gasoline tank might point to arson. If the fire originated close to industrial or agricultural buildings or activity, it could mean that ignition happened due to stray sparks from equipment.

The indicators that authorities use to determine the origin point of a fire vary, but here are a few examples:

• Protection: if the side of fuel (a tree, for example) is less damaged, it was likely sheilded from the fire. The fire likely came from the direction with more damage.
• Depth of charring: the side of the fuel with the deepest charring, the most scaling, and/or the most soot was facing the oncoming fire.
• Freezing: leaves and small stems are ‘frozen’ by extreme heat in the direction of the winds that the fire creates.
• V-shape: forest fires will often spread in a ‘V’ pattern from the origin point. Viewing forest fire damage from above can make spotting the point of the ‘V’ easier.

 

How fast can forest fires spread?

A forest fire can travel up to 10.8 km/h in most biomes, or up to 22 km/h in grasslands. Many factors effect how quickly a fire will travel including wind strength and direction, how dry the area is, and what is available to burn in a space.

What are the consequences of starting a forest fire?

Irresponsible behaviour that leads to a wildfire is punishable under the wildfire act in BC. Everything from failing to report a wildfire ($383) to using fire against regulations ($1,150) is covered in the legislation. In some situations, individuals may be held accountable for “fire control costs and related amounts” by the government.

If a person intentionally sets a forest fire, it qualifies as arson – an indictable offence. If the arsonist knows that the property they are setting on fire might be occupied, the charge of ‘disregard for human life’ can carry a maximum penalty of life in prison. If one is only damaging property, the maximum penalty is 14 years in prison.

 

We hope you found this post useful! Leave any burning questions in the comments and check out our other fire-themed posts here.

Article written by Zenia Platten – author and emergency preparedness professional.