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Set Fire to the Plain

Issue 1NatureNature Issue 1Sustainability

“King’s Head Inn, Burlington Bay [c.1792] When we had near crossed the bay, Beasley’s house became a very pretty object. We landed at it, and walked up the hill, from whence is a beautiful view of the lake, with wooded points breaking the line of shore…The hill is quite like a park, with large oak trees dispersed, but no underwood”

so wrote Lady John Graves Simcoe—wife of the first Lieutenant Governor of Upper Canada, Lord John Simcoe—when she traveled across the escarpment for the first time. She saw fields of prairies and oak woodlands stretching across the Aldershot area of Burlington. She describes landscapes in our watershed that have almost disappeared.

In our watershed, prairies and open oak woodlands actually made up much more of the ecological landscape than what remains today. Historical surveys and evidence from around the time of settlement, like the diaries of Lady John Graves Simcoe, suggest prairies and tallgrass communities made up 3800 hectares in Ontario around the time of settlement. Today there are few remnants bigger than two hectares in Ontario. Prairies are now a rare landscape, and so are the flora and fauna dependent on them. A healthy, biodiverse environment includes many different eco-systems like swamps, marshes, forests, and prairies.

Over the last four years, Conservation Halton’s restoration ecologists have been hard at work rehabilitating a section of Glenorchy Conservation Area to become a prairie once more, and to help it grow: we need to set the land on fire. To nurture a prairie back into being, and to sow the seeds that will promote a sustainable grassland, Conservation Halton will administer a prescribed burn to the hedgerows in Glenorchy Conservation Area.

Prescribe Burn

Photo by Nigel Finney

Prescribed burns are recognized by the province of Ontario as one of the few tools to stoke new growth and ecological regeneration. A prescribed burn, also known as a controlled burn, is a recommended, controlled fire in an area that ecologically requires it for resilience; that is, fire will eliminate invasive species, and prepare the land for restoration work to rebuild prairie grasslands. Prescribed burns are planned well in advance to ensure public safety, to prevent the hazards of a wildfire, and the plan must also comply with the rules laid out by the Ontario Ministry of Natural Resources and Forestry.

Igniting dry tallgrass to encourage growth seems like a foolhardy endeavour. But, fires are a natural occurrence, especially for growing and sustaining prairies. Lightning strikes started natural fires, and since the prairie was long and continuous, and the land flat and rolling, the fire crawled around the land burning up litter.  For many thousands of years, indigenous peoples also purposely set fire to the land. Early indigenous groups preferred sandy soil for agriculture, and sandy soil is the basis of tallgrass communities. They often burned the land to drive wild game, or to nurture local crops, like native blueberry shrubs. It is more or less unknown how often natural and human fires occurred—except, in some areas, we can accurately estimate fire frequency from burn marks on large oak trees. Native species like oak, hickories, and native grasses survived because they are adapted to fire.

Fire is the primary force in the prairies: it nourishes, protects, and rehabilitates the land for rejuvenation. Prairies can’t thrive without it. Tallgrasses are dense organic material; when a tallgrass dies and falls to the ground, it smothers the soil like a suffocating blanket. Fire burns away the litter to reveal the soil to the sun. Not only does fire clear away litter, but it also clears out invasive plants. Most invasive species are not fire tolerant like our native plants. Our native tallgrass plants sink deep roots into the soil–unlike invasive species such as Timothy Grass and Garlic Mustard. Invasive species compete by shading out native plants that need the direct sun to thrive. These plants are burned away while native plants are safe underground. Wildflower blooms are prolific after a burn, as are birds and insects whose populations flourish.

Once the clutter is dusted off the soil, the black ash warms the soil, and the fire itself releases nitrogen. Tallgrass seeds prefer a low nitrogen environment. Viable seeds in the seedbank need the heat of fire to germinate, to crack through the shell and force its roots into the soils. Seeds and prairie vegetation and flora need plenty of sun to germinate, to grow, to sustain the ecosystem. Prairies are full of green vegetation, insects, and small mammals. For prairies to thrive, fire reduces the enemies of the prairies to ash, and coaxes seeds to establish roots.

We cannot wait for nature to ignite the restored land, and it’s about as lucky as getting struck by lightning. We don’t want to be struck by lightning either: wild fires are not safe given the way we now use land in Halton Region. Remnants patches of habitat in Ontario are few, and small: the parcels of remaining prairie are less than two hectares in size. It’s unlikely lightning will strike a remnant, and if it did, the remnants are not connected, so the fire can’t swell over fields of tallgrasses. We have to help nature help itself. Controlled burns are the only alternative, because we literally control every aspect of the burn.

We’re not even burning the grassland yet: we’re burning small patches of hedgerows in Glenorchy Conservation Area. The goal behind for our prescribed burn is to demote invasive species. Restoration ecologists will burn the hedgerows to eliminate species like Common Buckthorn, and Timothy grass—a vicious grass that pierces through the woody roots of oaks, and destroys the very foundations of a native plant. An abundance of Timothy Grass and Common Buckthorn could spread and colonize over the space, which will affect the management and the costs of rehabilitating this landscape.

Once the hedgerows are burned, we will seed Canada Wild Rye, Big Bluestem, Switchgrass, Butterfly Weed and Wild Bergamot: we’re anticipating a burst in pollinator populations such as Monarch butterflies and bumblebees. Prairies buzz with life when they’re healthy. Insects, like bumblebees, thrive in this ecosystem, and therefore sustain the vivacious biodiversity in this environment.

Wild Bergamot

Wild Bergamot

Nigel Finney, Watershed Restoration Planner at Conservation Halton, said the team will seed the area by hand after the hedgerows are burned. It’s onerous work. Restoration ecologists have a big shoulder bag and walk slowly in a line, four metres apart from each other. They will grab a handful of seeds and spread to the right and then to the left. There are two different passes. There is a ‘fluffy’ seed mix, like Canada Wild Rye; and there is a hard small seed mix, like Wild Bergamot. Bergamot are tiny and need to be thinned out and spread onto the landscape, which is best accomplished by slowly walking up and down and spreading the seed by hand. Some seeds native to prairies are covered in a hard coating as a protective layer from water. Remaining seeds in the seed bank need a nudge from quick fire to alter the seed coating, enabling germination. Seeds will wait for years until the time is ripe.  It’s literally a trial by fire.

When a prairie is healthy, and able to sustain itself (albeit with periodic assistance from a controlled burn), the environment is able to withstand the threats of climate change, and changing weather patterns. Deep prairie roots penetrate the heavy Halton clays, allowing rain water to recharge the water table and reduce runoff. By building up the strength of a healthy ecosystem, the land itself is better able to absorb sudden, crushing storms, and therefore lessens its impacts on us, like damage to our drinking water or to our homes. Good stewardship is good public health policy.

Restoration Technicians broadcasting seed by hand.

Restoration Technicians broadcasting seed by hand. Photo by Nigel Finney.

As with any project, costs add up; fire is a cost-effective method as a tool in restoration. Other tools like mowing and pesticides are not as effective ecologically or financially. Mowing cuts down the grass, but it creates dense litter that suffocates the soil. Furthermore, mowing doesn’t fully eliminate invasive species. To replicate a burn that’s completed every three to five years, mowing would need to be done every year.  Unlike mowing, which leaves litter, and isn’t guaranteed to work, prescribed burns are one and done. The frequency of mowing versus a burn means that the costs would add up with mowing. Prescribed burns provide the most bud-for-buck in regard to labour, staff, and equipment; and, it also nurtures the environment by replenishing the soil with needed nutrients, and releases nitrogen. And one thing mowing cannot do is replicate those environmental processes. We would end up with less biodiversity, and therefore the restored land is less resilient.

Timing is critical for the success of a prescribed burn. Restoration ecologists are targeting specific species to grow, and specific invasive species to kill. The species we want to thrive grows in the mid-to late summer. A controlled burn before the growth period will affect the seeds at the correct time in the growth cycle and target invasive species that begin to green up in the spring.

The site is prepared beforehand to protect the public and to manage the burn. There are ‘burn breaks’, areas of bare soil, so that the burn is contained in a pre-designed area. These breaks are either made of up a band of raked leaf litter in an oak woodland setting or a lightly tilled band of soil in a grassland setting.

Once the site is prepared and the time is ripe, the site is secured and checked to make sure no one is on the trails or near the site. The team will then use drip torches to light the grasses and leaves on fire. Qualified practitioners watch from all sides, and there are people ready with water to douse the flames should the fire travel where it shouldn’t. After the fire dies out, staff survey the area for ‘hot spots’, like coals. Finney says it’s remarkably quick: a controlled burn he attended at Holy Sepulchre in Burlington was ninety minutes. The prescribed burn at Glenorchy Conservation Area is expected to last an afternoon, and everyone will go home after their usual work day.

Lastly, there is a special feature near the burn site that the restoration ecologists are going to save: a large dead standing tree, also known as a snag. Snags are wonderful ecological features. It’s a central spot for wildlife. Insects eat them, woodpeckers burrow in, owls nest here,and racoons hide. Species-at-risk, like bats roost in dead trees. According to Finney, the snag on this land is a beautiful, hollow Bur Oak tree. Since this snag is hollow, the fire can escape into it, and the hollow will act like a chimney: this could burn for weeks if unprotected. To protect this wildlife feature during the prescribed burn, staff will cover and fill any openings at ground level with wet soil so that the wood does not ignite and that native creatures will continue to make use of it.

Ultimately, fire will not only benefit the environment, it will also benefit us. A diverse portfolio of ecosystems in our watershed equips us with a resilient and self-sustaining environment. Prairies are full of life, and will greatly add to the quality of life in our watershed. Lady John Graves Simcoe wouldn’t recognize the landscape now, and nor would she recognize the newly rehabilitated prairie fields. Critics can argue that humans have meddled with the environment enough, but there’s always been human impact on the land whether it was post-settlement in the 1700s, or indigenous groups setting the land ablaze, pre-contact. As restoration ecologists, it’s our role to determine what natural landscapes are needed, what can be achieved, and how to achieve it: we’re scientists using data, weather patterns, soil types, and natural disturbances to conserve, restore and nurture Glenorchy Conservation Area and other natural areas into a biodiverse, sustainable, landscape for now and into the future.

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Last modified: June 19, 2018

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