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The West Kelowna, B.C., blaze spreads down hillsides toward residential areas.JONATHAN HAYWARD/The Canadian Press

Few people know better than Lori Daniels that the pillars of dark smoke rising over the forests of British Columbia this summer are going to increase in both frequency and intensity in the future.

The University of B.C. associate professor knows that in part because of what she sees looking into the deep past, studying the fire scars left on trees as far back as 700 years ago when the Black Death was sweeping through Europe and the Ming Dynasty was beginning in China.

"In our Cranbrook [research] area we have fire records back to the 1300s," she said, referring to the data being gathered from tree rings.

Now, driven by climate change and fuelled by a stockpile of debris, the forests of B.C. are headed for another period of frequent fires.

But this time around they will be more intense and the fire season will be two months longer, according to one Natural Resources Canada study that looked at the impact of climate change on forests.

Part of the problem in the future lies in the past. Drawing on samples collected from nearly 250 research sites in the Cariboo, Okanagan and East Kootenay regions, Prof. Daniels and her team have received "a strong, repeated message" that fires centuries ago were more frequent.

Her research shows that surface fires were flashing through forests once every 25 to 40 years. In some areas, there were fires every 10 years.

"And then a very interesting pattern emerges regardless of where we are [gathering data]," Prof. Daniels said. "The fire scars stopped about a century ago."

She attributes the change partly to a period of cooler, damper weather, but largely to the arrival of settlers.

"There were many changes to the forest that came with that. In part, land clearing," she said, "and also with settlements we would have had First Nations being excluded from the landscape … so they were no longer using the land in a traditional way or it was changing where and when they were using fire as a management tool."

Aboriginal people used to set fires to promote the growth of berry plants and to clear grazing areas for elk, deer and moose.

But the biggest impact Europeans had, Dr. Daniels said, was the introduction of forest firefighting. As settlements grew and the importance of logging to the economy increased, the government became increasingly efficient at suppressing fires.

"We made a decision decades ago that fire had only negative effects on the forests and we valued the forests for economic reasons … so we made a huge effort to suppress fires and we have been very successful," she said. "The numbers from the Ministry of Forests tell us 97 per cent of fires are put out before they reach four hectares in size. And over many decades that's had a cumulative effect and certainly that's reflected in that lack of fire scars in the 20th century."

But the success of firefighting created more risk. Without regular fires, fuel built up on the forest floor.

"When there's high frequency of fires, every 10, 20, even 40 years, that means in a human lifetime there would have been three or four fires repeated in the forest around them. And those fires would have burned off leaf litter and needles and fine fuels that accumulate on the ground … But in absence of those fires the fuels accumulate and … you get the conditions for a much more severe fire," she said. "And so there's the big paradox – by trying to protect ourselves from surface fires we've created conditions … for big severe fires."

When fires get going in a forest where fuel has been stockpiled, they can quickly get out of control, as they have increasingly in B.C. They have sometimes become so big, so fast that even the best fire teams can't stop them. In Kelowna in 2003, a fire swept over Okanagan Mountain, destroying 25,000 hectares of forest before jumping fire lines, forcing the evacuation of more than 27,000 people and burning 239 homes.

Fires of that intensity are going to be more common in the future said Dr. Daniels, because climate change is making the already dangerous forest more vulnerable.

"If I look to the past and try to see what we've learned and then look to the future, there's a few patterns that emerge. One is that … fires burn during drought years," she said.

And droughts will become more common because of climate change, which has already caused the average temperature to climb by 1.7 C in B.C., with a up to a 4 C increase predicted over the next 100 years.

Climate change means greater precipitation in some regions, but it has reduced winter snow packs and is producing drier springs and longer summer droughts.

Dr. Daniels said droughts in B.C. are driven by oceanic conditions such as El Nino, which brings warmer water up from the South Pacific. El Nino events have become more frequent and more intense off the West Coast since 1980.

All of that sets the stage for more and bigger fires.

"Climate change models … tell us … what used to be extreme [is] what we're moving toward in terms of what might become our average," Dr. Daniels said.

Dr. Mike Wotton, a research scientist with Natural Resources Canada, says studies over the past 20 years show that climate change will have a dramatic impact across the country – but especially in B.C.

One study he did, which broke the country into six zones from West to East, suggests that the fire season will be extended on average by 30 days nationally by 2040, except in B.C. where it will be 50 days longer.

Dr. Wotton isn't sure why B.C. will be the hardest hit, but topography and the influence of El Nino events on regional weather are key factors.

There is no question, he says, that climate change is increasing the fire risk. Simply put, longer periods of warmer weather will quickly dry out the forests, making them more susceptible to lightning strikes or human-caused fires.

"We do not intend to suggest that increased fire season length and the accompanying increase in forest fire occurrence and severity would be catastrophic for the Canadian forest," wrote Dr. Wotton and his co-author Dr. Mike Flannigan, a professor of wildland fire at the University of Alberta. "However, increases in the severity of fires and in fire-occurrence frequency, and thus fire load, could make forest management a more difficult task. From a fire protection and suppression point of view, this could translate into significantly increased resource commitment by firefighting agencies."

This week B.C. has more than 3,000 firefighters on the ground, including 350 from other provinces. B.C. has allocated $161-million to fight forest fires this year, up from the $134-million spent last year but less than the 10-year average of about $170-million. If the fire season extends by 50 days, it could add hundreds of millions of dollars to the annual bill.

In an interview Dr. Wotton said the changes over the next 30 years will be relatively small compared with what will happen by the end of the century.

Over the next 85 years, climate change models predict "an increase [in fire occurrence] on average for the nation of 75-100 per cent. So almost doubling the numbers," he says.

Dr. Daniels said it is clear British Columbians will have to do a better job of living with the threat of forest fires. That calls for more prescribed burns, to mimic the frequent surface fires of the past and clear out fuel. It also means more fires should be left to burn, when they don't threaten infrastructure or valuable resources, which is a policy recently adopted by B.C. And it means communities have to work continuously to clear away fuel building up in nearby forests.

"We have the fuels present and we have the right weather conditions … to dry out the fuels that put us at risk," she said. "I know people in Kelowna after 2003 … thought of that fire as a once-in-a-lifetime event. Maybe an important message to get across to British Columbians is … That was the new norm."


Forest Living Tips

Assess the "ignition zone," land within 30 to 100 metres of any structures.

Clear away any build-up of pine needles and leaves in that area.

Create a three-metre-wide, non-combustible zone on all sides of the home.

Keep trees and shrubs pruned and spaced far enough apart to slow the spread of fire.

"Limb up" trees around the house by removing branches within 2.5 metres of ground.

Keep lawns irrigated.

Use non-flammable roofing materials.

Ensure chimneys for all wood-burning appliances are screened so sparks can't escape.

From FireSmart Canada

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