How prescribed burns can help ecosystems thrive

Hayley Reid-Ginis · CBC News

· Posted: May 21, 2025 4:00 AM EDT | Last Updated: 11 minutes ago

The leafy trees that tower over Toronto's High Park are one of the last remaining black oak ecosystems in Ontario.

They're rare, so each year, fire specialists carefully set fires near their roots, in a controlled perimeter  — burning off the dry grass, leaves and twigs.

Smoke billows above the trees, drifting through parts of the park before dissipating. The flames linger where they're set, turning the underbrush to ash.

The traditional and prescribed burns in High Park have gone on for two decades, named Biinaakzigewok Anishnaabeg by the Indigenous Land Stewardship Circle that collaborates with the City of Toronto on the present-day rendition of what was a longstanding Indigenous practice.

While colonial rules in Canada long banned the traditional fire practices of Indigenous communities, that's been shifting, with more use of prescribed burning not just for wildfire protection but ecosystem health.

Renny Grilz is a resource management officer for the Meewasin Valley Authority, a conservation organization in Saskatoon that uses prescribed fires in and out of city limits.

"Part of conservation for, you know, the last 30 years was 'Set it aside, nature will look after itself,'" said Grilz. 

"We're realizing that no, we need to manage these landscapes."

Fire as a tool in urban areas 

The idea of a prescribed burn is to use a fast, low fire along ground level. 

Introducing fire to an ecosystem helps thin the forest of fuel, which can include things like leaf litter, sticks, and dead plants. In High Park, this gives fire-resistant species like black oak the space to thrive by burning back invasive species and allowing more air, nutrients and sunlight to reach them.

In March of this year, the City of Edmonton conducted its first prescribed burn within city limits, to reduce wildfire risk.

"This burn helped the city effectively reduce vegetation that could have fueled wildfire, and helped increase public safety by lowering wildfire risk in the area," Graeme McAlister, deputy fire chief, Community Safety and Risk with the City of Edmonton said in an email to the CBC News.

But conducting a prescribed burn in an urban area comes with risks.

"You have high value assets surrounding the area that you want to burn, but also smoke management becomes very critical," said Grilz.

Winnipeg has been conducting prescribed burns since the 1980s, for example, but Grilz says that other urban areas like Calgary, Regina and Moose Jaw, Sask., have expressed interest in prescribed fires, too. 

"As they [urban areas] advance their skill sets or knowledge base within these urban areas and their planning areas, they're starting to look at fire as a management tool," Grilz told CBC. 

"It's really exciting."

Helping native plants

In densely populated Southern Ontario, tallgrass habitats have a critical role, but they're in danger. They provide habitats for ground-dwelling birds like bobolinks and Eastern meadowlarks, both protected species in Canada.

"Tallgrass communities have been drastically reduced, like less than one per cent of what originally was in southern Ontario remains as native tallgrass. So we're trying to bring that community back," said Adam Brylowski, manager of conservation and trail at the Bruce Trail Conservancy, a non-profit organization that manages land along the Niagara Escarpment UNESCO World Biosphere.

The Bruce Trail Conservancy takes on ecological restoration projects, leaning heavily on planting trees and wildflowers in the past, according to Brylowski. 

In 2019, they recognized the importance of tallgrass prairie restoration, too. After planning and preparing a site, the Bruce Trail Conservancy conducted their first prescribed burn in 2022.

The native grasses need fire for their seeds to germinate, but it can kill off invasive species like Kentucky bluegrass and crested wheatgrass.

The Royal Botanical Gardens (RBG), spanning some 800 hectares along the shores of Lake Ontario between Burlington and Hamilton, also uses prescribed burns. 

The RBG has conducted burns at different sites since 1997, though they don't do them every year.

This year, the goal was to improve rare plant habitat, according to a public notice. This includes big bluestem and goldenrods, both native species in tallgrass prairie ecosystems.