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Climate change will impact grass fire season, experts say

Like clockwork, every summer the hissing and sizzling of farm land brings plumes of smoke billowing under a hard sun. It’s a predictable season for rural, volunteer fire departments, interchangeable with the arrival of spring and hot, dry weather.

In 2018, the Wilmot Fire Department, in Ontario, responded to 10 grass fires, according to Chief Rod Leeson.

Record-shattering heat waves brought about a hotbed of fire activity in 2017 across the globe. Leeson said the department even came close to enacting a burn ban.

This year, the department hasn't seen any grass fires.

An abnormally wet season

Agriculture and Agri-Food Canada's most recent Agroclimate National Risk Report says seeding is up to six weeks behind normal, with many fields still too wet, needing several weeks to dry out. Data from the same agency and Environment and Climate Change Canada, show precipitation levels in the Wilmot area ranging from 15 to 35-millimetres above average, with a Kitchener-Waterloo weather station having accumulated 205.4-millimetres of precipitation between April 1 and June 17.

Geoff Coulson, a warning preparedness meteorologist with Environment and Climate Change Canada, said year-to-year changes are common. This year has been "quite a different story in regards to precipitation and temperatures," due to a jet stream lingering over the lower great lakes, instead of tracking north, in what he called a "very stubborn pattern." As a result, we're seeing the "unsettled conditions" we've all been complaining about, a flip-flop between sunny and rainy days, which Coulson expects to continue for the remainder of June.

Environment and Climate Change Canada's three-month seasonal forecast, released at the end of May, tells a story of temperatures below seasonal, and levels of precipitation on par with, or below expected averages throughout June, July and August. Coulson says more time is still needed to properly speculate about the potential for midsummer grass fires.

Grass fires and climate change

Studies are predicting marked increases in temperatures and human-caused fires in Ontario. There will also be more lightning strikes and a lengthening of fire seasons in a warming world indispensable to climate change.

David Phillips, a senior climatologist with Environment and Climate Change Canada, has been watching Canada's weather for more than 50 years, and cautions that models are forecasting an increase in air temperature due to climate change.

For every one-degree rise in air temperature, Phillips says the atmosphere has a seven-per-cent increase in how much moisture can be held and dropped, meaning it will take longer to reach a level of saturation needed to rain. When it does rain, there will often be more of it, but with more time between rainy days.

During dry periods, the dirt surface hardens, becoming like pavement, allowing water to run off and preventing the absorption of moisture.

"Amounts [of rain] aren't as crucial as frequency," Phillips said. "Twenty-five-millimetres to one-inch of rain per week would be ideal to prevent grass fires from occurring."

Phillips said he doesn't see how anyone could argue the potential for grass fire occurrences wouldn't rise.

Getting close to the flames

Dr. Mike Wotton is a fire behaviour research scientist with the Canadian Forest Service and the University of Toronto's fire lab where he's currently researching grass fires in Southwestern Ontario.

Wotton says fuel moisture and wind are the most important predictors of how a grass fire will behave.

In the midsummer when water is lowest, plants "cure off," sending nutrients back into the root system for next season, leaving a plant in prime burning condition, with a moisture level around five-percent. That's a drastic decrease from the beginning of the season, when new-growth plants can hold three times their weight in water.

As wind fans across an open and exposed burning fields of light, dry fuel, flames are bent over and pushed onto other plants. Each piece of fuel only burns for around 20 to 25 seconds, said Wotton, but it's an energetic fire that burns quick and hot. Provided there's enough fuel and no breaks like large roadways, a grass fire could cover 10-kilometres every hour in a strong, sustained wind.

When the first flare up of the season inevitably arrives, volunteer firefighters from New Hamburg, Baden and New Dundee will employ pumpers, tankers, hoses and hand tools to gain the upper hand of what is often a preventable fire.

The service has a total of 85 volunteers, but the biggest challenge when fighting grass fires is time and access. Everything needs to happen on foot.

"You need lots of staff, you have to put boots on the ground to get right to the fire," Leeson said. "It's such a fast dynamic."

Firefighters will focus on exposures and setting up defensive lines to prevent a fire from reaching barns or homes, while others are sent out to flank a fire into submission.

For those wanting to have an open burn, including small backyard fires, a burn permit will be needed in Wilmot and can be applied for online. No permits will be issued when a burn ban is in effect.

Leeson says if someone doesn't have a burn permit, violates the terms and conditions of a permit or defies a burn ban, there could be hefty charges or fines on the table for the person responsible. Property owners are also liable for a fire getting out of control, even if they have a permit.

"They are fully responsible for all consequences once they decide to light the fire.

"In most cases the fine is relatively small, however the fire department response can reach several thousand dollars depending on the number of firefighters, apparatus and time it takes to fully extinguish the fire," Leeson said in an email.

Leeson noted two fires last year without burn permits, one of which resulted in a $3,000 fine issued and another which approached a central communications tower, a situation which he said could have interrupted critical emergency communications.

While Leeson says most comply with burn permits — with only three documented burn complaints last year and one to date this year — he mentioned several factors that are often present when open burns get out of control: not having a permit, not watching for weather changes, not having a method to extinguish a fire, not being physically present during a burn and burning materials that shouldn't be burned.

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