Research team collecting first field data on 'zombie fires' in N.W.T.

Jennifer Baltzer and her family were living outside of Yellowknife during the worst wildfire season on record in the Northwest Territories in the summer of 2014.

"First night that we were here, we got a call from one of our colleagues in (the Department of Environment and Natural Resources) saying, 'Oh, your road's closed, there's a fire really close to you,"' she recalled.

The extreme wildfire season, known as the "summer of smoke," saw 385 fires burn roughly 3.4 million hectares of forest in the territory, causing the release of an estimated 580 megatonnes of carbon dioxide equivalent. It also resulted in a phenomenon known as "zombie fires." Otherwise referred to as overwintering or holdover fires, these blazes continue to smoulder underground during the winter months before reigniting the following spring.

Baltzer, an associate professor of biology at Wilfrid Laurier University and Canada Research Chair in forests and global change, has been studying the effects of the 2014 wildfires on the environment. She is leading a team of researchers who are collecting the first field data on zombie fires.

"As an ecologist driving through some of those massive burn scars, I realized I couldn't be working up here on these boreal forests without actually starting to tackle some of these questions," she said.

Research suggests zombie fires, which can occur in Arctic, subarctic and northern boreal forests, could become more common due to climate change. Scientists believe that hot, dry conditions associated with heavy fire years can lead to deep burning in carbon-rich soils like peat.

Members of the forest ecology research group, based at Laurier, in partnership with the N.W.T. government, are travelling to about 20 sites in the territory accessible only by helicopter this month to see up close where zombie fires burned. They hope to learn how these fires affect carbon loss, forest regeneration, caribou forage and permafrost, as well as determine whether remote sensing is an effective tool for identifying zombie fires.

Baltzer explained that shrubs that recover quickly from fires are able to do so because of underground plant systems, which they suspect may be damaged by underground smouldering. She added that black spruce regeneration could be affected as their cones open and release seeds following a wildfire. Those seeds could be burned if the fire reignites for a subsequent season.

Risks and benefits of 'holdover' fires

Richard Olsen, the manager for fire operations with the N.W.T.'sDepartment of Environment and Natural Resources, said the territory wants to learn how holdover fires occur under current environmental conditions and the potential effects of climate change.

"We want to get a better understanding of the extremes and the conditions that they exist in in order to better monitor and predictand prepare for holdover fires," he said.

Olsen said the territory prefers the term "holdover fires" to "zombie fires" as the latter has negative connotations, noting fires are a natural process that have long shaped forests.

"People in general I think should be concerned about fires. But they should also be informed on really what the risk is and alsowhat the benefits of fire are," he said.

Baltzer said while she understands the concern, she believes the term can help capture the public's attention and help to convey aconcept that may be new to them in a way that's easy to understand.