To encourage healthy re-growth in grassy undergrowth and leafy wooded areas, a controlled burn operation is undertaken in the spring when it is still cool and before saplings have begun to bud. In forestry and land management, this helps to reduce fungal disease, insect infestations, clear old thatch and keep invasive weeds under control.
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Parks & Recreation here in Toronto have been doing their annual prescribed burning around the residential neighborhoods. This is a part of planned forest management to maintain a healthier forested area and also is a hazard reduction tool. By burning-off in a controlled manner the dead grasses and small fallen limbs and branches that have accumulated over the previous summer and winter, the likelihood of a more serious uncontrolled fire later in the season is reduced. An escaped campfire for instance could cause a bigger forest fire which would be harder to control in the drier summer and potentially involve homes and residential properties.
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A Back-Burn Trail
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Here you can see the control region where the undergrowth was raked back before the ‘back-burn’ was started. There was insufficient fuel for the fire to progress across this trail so the fire spread up the hill back towards the main fire approaching from the other side. Where these two fires meet they run out of fuel and expire.
Notice in the above image that the branches are distributed on the burned area. They were cut and broadcast to limit the fire’s intensity in any one spot for too long.
Permits for swailing, the ‘hazard reduction burning’ must be obtained in advance. Local neighborhoods are advised of the impending event a few weeks in advance with posters, handbills and other notifications. The weather conditions must be perfect. The prescribed day can be postponed if the weather conditions are not ideal. It must be cool outside with no winds and preferably with rain in the forecast. Humidity at the onset would be a asset too as this would limit the intensity of the burn. The organization that performs the controlled burn requires licensing to do controlled burns but still may not be freed from liability should the fire get out of control and cause damage to personal property of home owners. There is always risk involved with controlled burning of woodlot areas but it is managed risk.
Benefits of Controlled Burning
Controlled burns are part of sensible forest management, prairie restoration programs and oddly enough, there are even greenhouse gas abatement issues at stake. A light controlled burn will prevent a larger wildfire later on which will cause more extensive damage and release far more carbon during the months when temperature inversions could trap the smoke closer to the ground, creating ’smog’ pollution. Even if the light burning is not complete or is performed in a ‘mosaic’ pattern’ over larger tracts of land, it still greatly limits the potential damage that a subsequently larger and uncontrolled wildfire can do.
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The taller dead grasses, weeds and tangled thickets of last summer’s vines are now gone. The tree trunks show only mild scorching. There will be less pollen and probably fewer pesky insects as a result of this action. Another successful controlled burn in this Toronto suburb has resulted.
Light burns actually help the soil by quickly returning some nutrients such as nitrogen and phosphorus from the burned underbrush, and swailing encourages some conifer seeds to germinate while killing undesirable weeds and their seeds.
Soil can actually be physically damaged if the fire is too intense or concentrated on any specific area for too long, such as a burning log pile, fallen tree or piles of branch debris left over from logging operations. Burn piles such as bonfires are the example and in a controlled burn, these piles would be leveled out or removed altogether prior to the burn.
Broadcast burning (spreading the burnable material such as branches out over a larger area) has a lower overall temperature and is the most helpful and is the least damaging to the field or woodland being treated.
Coniferous forests benefit the most from controlled burns. The controlled fires help protect the trees from diseases, insect infestations and even from future fires. A controlled burn will improve the grassland and forest for many wildlife and reduce undesirable vegetative species, allowing better undergrowth which means better grazing range for wild animals such as rabbit, deer etc. The grass is always greener and lusher after a controlled burn has cleared the way.
Insect and Snail Population are Controlled
These snails numbers in the hundreds and probably thousands around this particular wooded grove. They are spaced within inches of each other everywhere in this woods. After the fire they are all dead. Their calcium will now quickly return to the soil and help the plants flourish.
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The numbers of land snails that were killed here in these controlled burns will very quickly rebound. Within a month or two these woods will again host these curious snails in the familiar hoards which seem to be ever abundant in this woodlot.
Other Controlled Burn Casualties
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Nearly all the animals benefit but as with everything that is interfering in the name of helping, there are always a few casualties. Their numbers are small and while unintended and unfortunate, can be dismissed. I found several deceased grass snakes. They seemed to have perished after the fire as if they tried to flee their underground hideaways and encountered tortuous hot spots. The grass beneith them was burned, suggesting that they had entered the area after the fire had passed through. They probably attemtped to flee the relative safety of an underground hideaway and encountred misfortune. Perhaps there was too little ground-level oxygen and the snakes suffocated? This snake was dead but not visibly scorched. The same was true with several other snakes that I discovered on my photographic hike, dead but not visibly scorched.
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In the above image we can see the ‘white ash’ of a somewhat denser fuel-pile that burned. Here, logs or branches probably lay and burned a lot hotter and longer. I examined this controlled burn region over 24 hours after the event had ended and some of the larger ‘white ash piles’ were still giving off noticeable heat. Here, the soil was probably temporarily sterilized to a depth of several inches but it will build-back very quickly.
Slash and Burn
Field burning is a technique to clear large tracts of land of unwanted crops, weed and debris. Less expensive than tilling the soil or using pesticides and therefore desirable to the farmer, field burning produces large amounts of smoke which is bothersome to residential areas and homeowners making it an unpopular option.
Some states have had bad events result from sanctioned controlled burning. In 1988 in Oregon, farmers burning grass from fields caused a smoky condition on an interstate highways which lead to a multi-vehicular pileup. Twenty-three cars crashed on the highway due to obscured visibility. There were seven deaths and thirty-seven additional injuries as a result of the visibility-reduced conditions. Since then, increased scrutiny and public outcries on field burning performed by farmers has resulted in proposals to ban field burning in Oregon altogether. But perhaps Oregon should not act too hastily on this proposition. The state of Florida offers a counter-view and could serve as a lesson to be learned.
Fire Prevention by Controlled Burning
In Florida during the drought of 1998, many large wildfires spread through the everglades and damaged many homeowners’ houses and properties. I suppose that those episodes of “CSI: Miami” of a few years ago that used field shots of everglade wildfires was actual stock footage of these real fires.
Controlled burning had not been performed for a number of years leading to an ever-increasing layer of debris, leaves, mosses and dead branches. This would serve as fuel for the bigger uncontrolled fires that would eventually burn out of control and devastate the region. Had smaller, controlled burning been employed in the years prior, this uncontrolled wildfire event may have been averted or certainly been greatly reduced. I think the homeowners whom lost homes due to the wildfires would agree. I’d accept a weekend of mild irritating wood-smoke once a year over an eventual real-estate destroying wildfire every decade or so.
