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News Release

October 30, 2006

Controlled Fires Help Restore Native Plants, Says Prof

It may seem illogical to set fires to protect threatened native plants and reduce the risk of accidental fires, but a University of Guelph researcher has found it’s a method that works in Vancouver Island’s Garry oak ecosystem.

“We’ve found that prescribed burning is a very effective tool for eliminating problematic exotic plants and allowing native plants to thrive,” said integrative biology professor Andrew MacDougall.

MacDougall has been setting controlled fires in the Garry oak ecosystem near Victoria, B.C., for the past seven years. He has focused his research, which has been published in the journal Ecology and featured in Canadian Geographic, within this ecosystem because “it’s a biodiversity hot spot in Canada,” he said.

The ecosystem used to be burned annually or semi-annually by First Nations people for centuries until Europeans arrived in 1843, said MacDougall. “As soon as you stop burning, you get a conversion from grassland community to a forest, and that’s what has happened. This conversion to forest has resulted in habitat loss, meaning a substantial reduction in the population sizes of hundreds of species.”

Of the 517 species mentioned in Canada’s recently created national Species at Risk Act, 40 of them are from the Garry oak system.

It’s a unique area because of its sub-Mediterranean climate, which means the winters are wet but never get especially cold and the summers are hot and dry, said MacDougall. “There are only five regions in the world that have that climatic signature.”

The rare native plants are being overtaken by exotic plants that were introduced to the area by the European settlers. MacDougall’s test area is overrun with six-foot-tall exotic grass whose presence is associated with the virtual elimination of a number of native plant species, such as the prairie violet, the balsamroot sunflower and the white-top aster.

“A lot of the problems we’re seeing in these systems reflect fire suppression because as soon as we burn, we’ve substantially reduced the exotic plants,” he said. “We’ve found that a large number of native plants, such as the camas lily thrive with fire, so the fire is doing its job to encourage native growth by controlling the exotic plants.”

Many native plant species can tolerate burns because they are inactive during the burning season, he said. “Camas, for example, grows during the winter and spring, so by the time July comes around, it has already set seed and is therefore unaffected by fire.”

MacDougall has found that prescribed burning not only controls invasion by trees and exotic grasses but also eliminates accumulated plant litter (such as dead grass, needles, bark, fallen trees and branches) which reduces the risk of accidental fires.

“By regularly burning, you actually prevent big fires,” he said.

Accidental fires are extremely hot and dangerous because of the huge build up of litter, which causes an explosive fire when it eventually burns, said MacDougall. “Back in the days when fire was a regular occurrence, it cleaned up the litter so the fires could never get really hot. If there’s any message from this research, it’s that if we do burn, we may be able to keep those catastrophic fires in check.”

“Prescribed burning is a method that was used by provincial forest services, but budget cuts and safety concerns have resulted in declining use of those methods, and this has contributed to some of the catastrophic fires we’ve recently seen in western North America.”