Prairie soil after a fire

Risks


Some mainstream news outlets tend to sensationalize their coverage of prairie wildfires by emphasizing how many “acres of land were destroyed,” leaving Canadians with the impression that the land is gone.

Grassland specialists such as Barry Adams counter those reports by explaining that fire cannot destroy land.

“But it can destroy peoples lives,” said Adams, who recently retired after a 38-year career in rangeland management with the province of Alberta.

“The land always recovers. People sometimes do not. That’s the cost we should focus on in dealing with wildfire. There’s always human impact, human losses.”

Grasslands take care of themselves, he added.

“We’re talking about native rangeland and native grasses that evolved for thousands of years under a regime of fire, grazing and stress,” he said.

“They’re designed to bounce back every time. Fire burns the vegetation. It doesn’t burn soil.”

History shows that before settlement and modern firefighting technology, Mother Nature conducted a major grassland burn on virtually every area of the Prairies approximately once per decade.

In the winter of 1792-93, Hudson Bay Company surveyor Peter Fiddler travelled from the Saskatoon area to the Calgary area.

His journals describe a totally black landscape throughout the whole area, the result of a massive wildfire.

Adams said the 1987 prairie fire west of Nanton, Alta., was an eye-opener for grassland specialists and the public in general, even though we’ve observed prairie fires since the first days of settlement.

The Nanton situation was exacerbated by a unique condition called crossover, meaning the relative humidity is lower than the ambient temperature.

The fire gave researchers an opportunity to hone their skills. By measuring the speed at which the fire front moves and estimating flame height, they’re able to calculate how much heat the fire creates. This, in turn, lets them determine the degree of damage to the grassland cover.

“It wasn’t until late 1980s and the Nanton fire that people began to understand how dangerous and how powerful a grass fire could be,” Adams said.

“Our equipment just wasn’t adequate to control a fire like that.”

When the Granum fire broke out in Alberta in mid-December 1997, it shocked people again.

The fire burned 54,000 acres of grass and travelled 32 kilometres before being brought under control. Approximately 250 cattle were lost, five homes destroyed and more than 1,000 kilometres of fence line burned. There was one human fatality.

“Even if there’s no human injury, there’s still a human cost, in terms of productivity and in terms of how many years before the plant community can be grazed again. That human cost depends on how severely those components in the plant community have been damaged,” he said.

“After the Granum fire, the ranchers who’d been burned out came to see us. They were like shipwrecked sailors. They didn’t know what to do or what to expect from their grasslands.”

Adams said ranchers can assess their losses and predict when the burned areas can be grazed again.

Moist areas, such as the parkland region and foothills, have a distinct organic layer right at the soil surface called thatch.

Just above the thatch is a duff or mulch layer, and on top there’s standing litter and litter that’s breaking down. The effect of fire depends mainly on the extent of damage to the growing perennial plants as well as damage to the litter, mulch and thatch layers.

“This is how we summed it up for them (the ranchers.),” Adams said.

“In lightly damaged areas you can still see the bunchgrass, and the surface is still well covered with organic material. In moderate damage, you can see the fire has burned into some of the crowns of the bunchgrass and you see openings in the organic cover.

“In a severe or extreme burn, you see that the organic cover has been burned away, and the fire has burned away the living perennial plant material. Recovery from an extreme burn is much slower.

“We’ve studied the recovery period in a number of fires, and we can say it’s common to expect a period of four or five years before an area is back to full productivity. In a severe burn, it can take longer. If you’re a cattleman and you depend on that grass, a fire can put you right out of business.”

It’s not natural for a prairie ecosystem to live without some form of vegetation disturbance through grazing or fire, Adams said.

If a plot of land is not used, and a lot of litter and excess material accumulates, it becomes a scene for a bad fire. On the other hand, a certain amount of organic litter is necessary to prevent erosion, cool the soil and conserve moisture.

“If you get rid of the litter through over-grazing, you create what we call a man-made drought,” he said. “The worst damage we saw in the Granum fire was on the knolls and hilltops where there hadn’t been any grazing at all. Tons and tons of litter had accumulated and it was like a torch.

“I realize it’s a challenge to get your animals to graze up there, but you’re inviting disaster if you don’t. Ranchers use water and salt and supplements and extra feed to coax their animals up there. It can be done, and it is necessary, but you wouldn’t want to use fire to remove litter. You’d only do it with grazing.”

Prairie residents — in the nearly two centuries that cattle have been grazing the region — have had a fair degree of success in preventing the giant fires that previously had controlled forest encroachment. As a result, trees and scrub brush thrive in areas that had once been pure grassland.

“We now have a lot of prairie landscapes that have a lot of woody cover, and that impedes grazing by cattle,” he said.

“If you go up to the top of the Cypress Hills, for example, you can see the pine is moving into the grasslands and expanding it’s grasp on the prairie. So fire does have a role in controlling scrub brush.

“You have to be fully aware of what type of soil you’re on. One thing we’ve noticed is that extreme fire on sandy soils can allow wind erosion.”

Adams said there’s not much a rancher can do to hasten the recovery. He cautioned against the temptation to fertilize or seed the burned area.

People have previously cultivated and even plowed burned prairie, but he said that’s the worst thing to do because it buries millions of seeds too deeply to ever come to life. As a result, the makeup of the natural plant community will be forever lost.

“The question rangeland managers hear the most is, ‘when can we graze this land again?’ ” he said.

“It’s important to study the area to assess the extent of damage. Is it slight, moderate or extreme? You may have to wait until the start of the next growing season to determine what’s happened.

“If the plant community hasn’t changed, the recovery, of course, is quicker. You can start to put animals back on the grassland very gradually as you see significant fresh growth. We actually measure the re-accumulation of litter. As litter increases, you can put more animals on the land. But don’t rush it. There’s no silver bullets.”

Some worry that a hot fire can harm helpful soil-borne biological agents, but Adams said he doubts it. All biologicals that are present in the soil today are members of families that have developed with fire for thousands of years.

In accordance with Charles Darwin’s theory of evolution, the weak genetic lines that were susceptible to fire kill would have been eliminated long ago.

For more information, contact Adams at 403-394-5899 or email bwadams1@telus.net.

Risk and reward after a Prairie fire

Risks

  • forage loss
  • livestock loss
  • infrastructure loss
  • farmer stress
  • financial loss
  • soil erosion
  • weed invasion

Rewards

  • ecosystem renewal
  • forage improvement in quality and availability
  • improved wildlife habitat
  • removal of decedent vegetation
  • nutrient cycling

About the author

Comments

explore

Stories from our other publications