Canadian wildfire: human and physical factors contributing to the record conflagration

The Canadian state of Alberta in the north-west of the country, has been battling a vast wildfire for four days since the 1st May. It is, in fact, several separate fires which have led to the destruction of 1,600 homes and the evacuation of an entire city of 88,000 people: Fort McMurray. It is due to become Canada's costliest natural disaster as the insurance bill is likely to rise above half a billion pounds (£).

Wildfires are not unknown in Canada - the state experienced a massive incident in 2011 around Slave Lake. But this covers a larger area, is more intense and is threatening far more properties.

The physical causes are:

Medium term: a 12-month long drought in the northern part of the state that has dried out the brush that underlies the forest creating brush fuel that is highly inflammable and a thick layer that may be extinguished on the surface but keep smouldering beneath. And the winter of 2015-16 has seen relatively little snow that, normally at this time of the year, would be melting and keeping the ground surface moist.

Short term: very high temperatures into the mid to upper 20's C in recent days has dried the vegetation further of any remaining surface moisture. Strong south-easterly winds are blowing from the interior of the continent drying material further, providing oxygen once a fire ignites and blowing cinders downwind to create fire-spread over a wide area.

The human causes are:

No-one is sure how this fire first ignited. Human actions may deliberately (arson) or accidentally (camp fires and BBQs) start wildfires, but the most common cause of them in Canada is lightning strikes (39%). But, ironically, it may be success in halting past natural forest fires by human intervention that has ramped up the likelihood of more massive future wildfires. The rapid control of fire in forests over the last 20 years has prevented the fire-induced regeneration of new tree growth and burning of superficial brush at ground layer, and allowed the forests to become dominated by mature and older trees and for brush to accumulate to significant depths. Once a fire breaks out in these conditions, it quickly becomes a wildfire of catastrophic proportions if the weather conditions are conducive.

So far, no lives have been lost - a testament to the effectiveness of Canada's wildfire advisory service and the evacuation systems in place. But a future wildfire management strategy may be to ensure small natural fires are allowed to burn a little longer before being controlled to prevent the build up of conditions that turn it into a record-breaking natural disaster.

Read more on the Fort McMurray fire causes in this article from the Edmonton Journal, and watch the video clip on how to protect life and property from wildfires.

This blog from Canadian Geographic identifies further causes of the wildfire.

With climate change likely to create more extensive drought periods, reduce snowfall, increased temperatures and - with more Canadians moving to live in forested areas - more chances for accidental fires to start and then spread, Canada is likely to see more natural fires in the coming years. Whether they turn into wildfires (uncontrolled natural fires) will depend on understanding all the causes fully and responding effectively.