Burns Bog fire: How bog fires burn and why they’re difficult to combat

Forest fires can be difficult to combat, but peatland — or bog — fires present a whole set of new challenges for firefighters.

The Burns Bog fire burning in Delta, British Columbia, is an example of how peatland fires can burn out of control.

READ MORE: Burns Bog fire update: Road closures, evacuations remain in place

According to Natural Resources Canada, peatland accounts for about two to three per cent of Earth’s land surface, and about 25 to 30 per cent of the global boreal forest region. Of that, Canada is home to roughly 25 per cent.

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    Bogs are home to peat, a collection of decayed organic matter and vegetation. This peatland collects more carbon than any other means on Earth. For that reason, when these areas burn, they release considerable amounts of carbon dioxide and other greenhouse gases into the atmosphere.

    When peat burns, it can burn deep underground for metres, even in damp conditions, until its fuel is exhausted. These fires are known to smoulder underground, even riding out the winter months.

    Due to climate change, warming temperatures and the rising incidence of drought conditions, there is concern that these peat fires will become more common. Melting permafrost can also add more peat to the forest, which in turn provides more fuel.

    WATCH: Challenges of fighting aggressive Burns Bog fire

    Steve Taylor, research scientist with the Canadian Forest Service in Victoria, B.C., said that fighting peat fires can be more difficult than crown forest fires.

    “The strategy in upland situations or non-bog fires is often to contain the fire by scraping the organic layer away down to mineral or soil by hand using crews with tools or bulldozers so you’re creating a fire guard,” he said. “But in a peat situation, where there’s likely a metre or many metres of organic material, that’s not necessarily possible, or it might not be ecologically sensible.”

    As well, firefighters might have a more difficult time finding the fires.

    “You can usually see open flame or smoke with infrared; but if the fire is burning deep and smouldering with no open flame [there may] not be a thermal signal,” Taylor said.

    While it’s not known how the Burns Bog fire started, peat fires can begin in much the same way as large forest fires, with a lightning strike or a human cause, such as a discarded match or cigarette. In the case of a lightning strike, peat can ignite after a tree is struck by lightning and ignites, travelling down into the root and spreading throughout dried out vegetation.

    Though we likely think of bogs as moist areas, they go through dry periods.

    “Peat is quite dense,” Taylor said. “It has quite a significant energy content and will burn slowly, as long as it’s dry enough.”

    The region experienced drier than normal conditions in April and May, which could mean that the peat has dried out centimetres into the ground or even a metre or more, Taylor said, allowing for favourable burning conditions.

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