The Fort McMurray fire has released millions of tons of carbon into the atmosphere and destroyed natural habitats. Scientists fear it may have caused long-term damage to the surrounding boreal ecosystem

While burnt-out homes and vehicles dominate visuals of the Fort McMurray devastation, much of the damage done by the enormous fire will be invisible. At the time of writing, the fire has burnt its way across 522,895 hectares of boreal forest and scientists warn it will have destroyed wildlife, scorched the underlying peat and released vast quantities of CO 2 into the air.

‘We have very preliminary estimates of around 89 million tons of CO 2 released,’ Werner Kurz, a forest carbon scientist at Natural Resources Canada, tells Geographical. ‘To put this into perspective, it’s equivalent to about 12 per cent of the annual emissions from all other sectors in Canada. Better estimates will become available when the fires have stopped and we can evaluate the variety of vegetation burned.’

While wildfires are part of the natural cycle of boreal forests and return to one area every 80 to 200 years, it is the sheer size and heat of the Fort McMurray fire that is so damaging. ‘It’s a huge fire – it covered an area twice the size of Dorset or Luxembourg,’ says John Innes, Dean at the University of British Columbia Faculty of Forestry. The blaze, nicknamed ‘the beast’, has been burning so hot that damage may have extended under the ground. ‘We saw similar scenarios with the Tasmania fires last January, which were so hot the soil burnt too,’ says Innes. If the peaty soil around Fort McMurray has burned, not only will that release more sequestered carbon, ‘it could be destroying the forest’s seed bank and tree roots, preventing regrowth.’

As for wildlife, there are some species that could benefit from fire, such as black-backed woodpeckers and black pine trees, so long as they have survived the high temperatures. Large mammals, however, tend to get trapped, especially bear and moose. ‘What you often find with a fire is that there are pockets of woodland that survive,’ says Innes. ‘These may be vital for the future regeneration of the forest.’

The Canadian wildland information system map showing fire risk for 4 May, when the fire jumped from 7,500 to 85,000 hectares. Dots show the locations of forest fires. Click here for an interactive map (Image: NRC)

A WARNING SIGN

Fires have been increasing in intensity in Canada’s northwest boreal forests. It is a trend, in part, that parallels warmer temperatures brought by climate change. Could fires this large and hot be the new normal for Canadian boreal forests? ‘I think it is a warning of what is possible,’ says Innes. ‘For the last few years we have expected to see about 2.1 million hectares of burn across the country. This splits to an average of 200,000 to 300,000 hectares for each province, which is high, but seems to be the normal state of affairs now. What’s more, those are multiple fires, not one large burn.’ During a single event, the Fort McMurray fire has incinerated double Alberta’s average annual burn, at only the start of fire season.

For this reason, Innes is sure that 2.1 million hectares countrywide will be exceeded this year. ‘An El Niño winter has resulted in a lower winter snowpack that melted earlier than usual,’ he says, ‘but what really stokes fires is the weather we have been experiencing.’ On 3 and 4 May, temperatures set record daily highs at around 32ºC, the kind of heat usually recorded in the deep summer months of July and August. These were kindled by a relative humidity well below 30 per cent and wind speeds of over 30 kilometres per hour. ‘It met the 30/30/30 fire rule,’ he explains. ‘However, because there are still large areas of dry fuel all over the northwestern forests, if we keep seeing these weather conditions it could happen again. We could have another fire this size, anytime in the summer’.