ANALYSIS: Abundance of rain brings tepid start to grass fire season
SouthWesternOntario.ca
 

The hissing and sizzling of farm land giving way to plumes of smoke billowing under a hard sun is so predictable for rural, volunteer fire departments.

Grass fires have their own season; running parallel to, and at once interchangeable with the arrival of spring and hot, dry weather.

In 2018, the North Perth Fire Department responded to 12 grass fires, said Assistant Fire Chief Jason Benn.

This year, the department hasn't seen any, which Benn attributes to the wet weather.

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 Listowel area ranging from zero to 35-millimetres above average, with a Wroxeter weather station having accumulated 238.2-millimetres of precipitation between April 1 and June 13.

Geoff Coulson, a warning preparedness meteorologist with Environment and Climate Change Canada, said year-to-year changes are common. He said 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 connected to climate change. In Saskatchewan, unprecedented dry conditions have already encouraged 132 fires this year.

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. More drier days without rain could be on the rise.

For every one-degree rise in air temperature, Phillips says the atmosphere has a seven-percent 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.

 

"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."

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

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 the 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, volunteers from Atwood, Listowel and Monkton will employ pumpers, tankers, hoses and hand tools to gain the upper hand of what is often a preventable fire.

Benn, the assistant fire chief, spoke of a fire in July of last year, originating from an overheated and malfunctioning gear which brought out all three of North Perth's stations, including their field tanker. By the time the department arrived, eight to 10 acres had already been scorched.

Benn estimates a 50-50 split between grass fires originating from open burns versus farm implements.

For those wanting to conduct open burns, permits are needed and can be requested by contacting the fire department at 519-291-6825, during office hours, Monday to Friday from 8:30 a.m. — 4:30 p.m.

"We always ask people to burn in an open area, to turn up soil around the fire to limit vegetation, and to keep the pile to a reasonable size," Benn said. "If people just take that extra few moments to think, the fire service won't have to get involved."

If a burn ban is in place, or a burn isn't authorized, the department can charge a service fee to a property owner of $477 per truck, for every hour a truck is at a scene.

Benn said the department has had good compliance from people calling in to request permits before burning, and that no complaints have been called in so far this year, which is good news for everyone.

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