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Science

Martell: 'Fire is a natural part of forest ecosystems in Canada'

Flames are still ravaging Alberta's forests. Wildfire expert David Martell explains why small fires are sometimes set intentionally to prevent bigger ones - and why that wasn't done in Alberta.

DW: What is your relationship with forest fires?

David Martell: I help forest fire managers with their decision making and planning. I develop computer models they can use to help them evaluate their strategies: for example, how many aircraft they need for fighting fires in their area. Managing that is not unlike an emergency medical system. You have to predict when and where medical emergencies might occur and where you should pre-position your ambulances to minimize the response time.

David Martell. (Photo: private)

As a young man, Martell spent six weeks on a fire crew

The job of these incident management teams is to basically contain and extinguish the fire as quickly, as inexpensively and, most importantly, as safely as possible.

How can you stop or contain wildfires?

First, you have a good fire prevention system that's designed to reduce the chance that people will start fires accidentally. We also have detection systems - here in Ontario they use patrol aircraft to look for fires when they're small.

Then there's an initial attack system: if there is a small fire that's reported somewhere in Ontario, they will send two air tankers. Those are water bombers that fly down near the surface of a lake and scoop up water into tanks. Then they fly over and drop the water on the flames. While that's happening, there'll be an initial attack crew of firefighters. They will set up a portable pump from a river near the fire, lay a hose up to the fire and gradually stop it from spreading, eventually extinguishing it.

What's it like in Alberta?

In some parts of Alberta there's not as much water. So often they will use so-called hand-tools, shovels, axes and so on, to dig a trench around the fire. Sometimes they will also use land-based retardant bombers. That's what you see on TV when an aircraft drops a bunch of red stuff instead of water on a fire.

Water bomber dropping water on a forest. (Photo: REUTERS/Government of Saskatchewan)

Water bombers, like this one over Saskatchewan in 2015, aren't usually employed in Alberta

And what happens if the fire is really intense and escapes these initial attacks?

Then an incident management team is brought in. They'll devise a strategy for how to contain the fire. They could have anywhere from dozens of firefighters to hundreds of firefighters. I've seen [teams] with more than 350 firefighters in them.

Sometimes smaller, low-intensity wildfires are "created" on purpose, in agreement with fire managers. Why is that done? It seems very counter-intuitive.

Basically, what people want to do with that is reduce the continuity of the forest vegetation. Fire managers refer to forest vegetation as fuel, because it can burn. They're interested in the vertical and the horizontal continuity of the fuel.

If you go to southern interior British Columbia, you'll find a forest type called ponderosa pine on grasslands. After fighting fires there for many years, new trees grow under the larger, older pines. Eventually, if you don't cut out the understory, you get a continuous distribution of fuel from the ground through the intermediate trees up to the large ponderosa pines. If you get a fire in there on a hot, dry, windy day, it's going to become very intense.

However, if you go in there before the understory becomes really established, and you occasionally use low-intensity prescribed burns, the ponderosa pine, with its very thick bark, will withstand that fire. You'll burn some of the grass and some of the seedlings that are starting to grow, but the large trees will survive. Doing that on a regular basis keeps that forest type in a relatively non-hazardous state. You're thinning it out by using low-intensity, intentionally set fires. If a large fire occurred in that state, it would be less intense, no high flames and it would not kill the existing trees.

So that's using fire to disrupt the vertical continuity of a forest. What about the horizontal one?

In Australia, they have a lot of areas that have brush and grass. One of the methods they use there is not unlike crop rotation, in theory. They break the landscape up into patches and then they will burn a patch every five or six years. They look at it as a mosaic and decide: which patch are we going to burn this year? And then they develop a plan. That's breaking up the horizontal continuity because once a fire gets to a previously burnt part, it can't spread anymore.

Trees burning in Alberta. (Photo: Getty Images/AFP/C. Burston)

The fires around the city of Fort McMurray in Alberta are still not under control

Was either of these methods used in Alberta, where the fires are currently raging?

The problem with the trees in Alberta - highly flammable spruce trees - is that you can't thin the forest structure with low-intensity burns. You can't even consider understory burning to break up the continuity - having a small, controlled fire would definitely not work there.

Breaking it up into a mosaic and burning it in cycles in the way they burn the grass in Australia is also not practical because there's so much fuel there. So the only way they can actually deal with the fuel problem in Alberta is to go in and remove the spruce trees near communities and replace them with something that's less flammable, perhaps grass or trees that burn less easily.

What about animals that live in the area, where small contained fires are used to thin out the forest?

Fire is a natural part of forest ecosystems in Canada. When you burn, you're recycling nutrients and improving the habitat for animals. The one exception would be ground-nesting birds. You don't want to do a prescribed burn when ground-nesting birds are around. But in general, fire is natural, fire is good for trees in the long run. I always say to my students: Fire destroys trees, it doesn't destroy forests.

David Martell is a professor in the Forestry Faculty at University of Toronto in the Canadian province of Ontario. He started working there as a fire management specialist in 1974. For the past six years, he has been assigned to one of Ontario's Incident Management Teams, a small group of managers tasked with fighting large fires.

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