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Background- The 2023 Fire Season
The 2023 wildfire season in Alberta saw over 2.2 million hectares across the province burn (Beverly and Schroeder 2024). This season may represent a glimpse of what is to come with current climate warming trends. Fire seasons in Alberta are getting longer, starting earlier in May and running later into September (Jain et al. 2017). The 2023 season saw a high number of early-season fires accounting for half of the large fires (>10000ha) (Beverly and Schroeder 2024).
The 2023 fire season was an aberration, not predicted by any models or experts; it caught management agencies off guard (Beverly and Schroeder 2024). As a cause of anthropogenic climate change, we will likely see future seasons with similar early-season extreme fire behavior (Beverly and Schroeder 2024). Knowing the potential for future seasons of similar intensity, it is important to learn from what has passed.
Perimeter Formation and Wildfire Behavior
Fire needs three things to burn: fuel, oxygen, and heat, these make up the fire triangle (Nova Scotia 2021). Fire perimeter formation is caused by the removal of one of these three components. Precipitation can remove heat, smothering in mineral soil can remove oxygen, or a fire can run into a fuel break, either natural or man-made (Nova Scotia 2021). Perimeters can form naturally or via suppression, on larger fires it is impossible to suppress the entire perimeter. Suppression resources are triaged to the important areas leaving many areas free burning. This means large sections of large fire perimeters will likely be stopped by natural fuel or weather.
Weather, topography, and fuel are the main factors influencing wildfire development and growth, notice there is one constant between the fire triangle and the fire behavior triangle: fuel (Werth et al. 2011). Fuel types in Canada are clearly defined using the CWFIS FBP system (Fuel type descriptions 2019). Conifer fuels are often more volatile, with deciduous stands acting as fuel breaks most of the year (Werth et al. 2011). Deciduous stands are however, more flammable than usual in spring, before green-up, and during spring dip, where the trees have less moisture due to their emphasis on leaf production (Jolly et al. 2016). Once the leaves on the canopy close, less sunlight and wind reach the surface fuels, and the forest retains more moisture (Fuel type descriptions 2019). The grass is also dead in the spring and an available fuel source that becomes less involved later in the season (Fuel type descriptions 2019).
This study focuses on the role of fuel, many forest types in Canada are considered fuel breaks due to their naturally low volatility (Alberta Government 2021). This study sets out to determine whether these classifications were still accurate throughout the varying seasons and changing climate in Alberta.
Seasonal Fuel Differences
The images below show the differences in deciduous and grass fuel types throughout the fire season. Imagine the different effects of dropping a match in each of those areas. Conifer trees are not shown, as the two photos would be near identical! Conifers maintain their needles throughout the year; thus, the understory fuels remain similar. Needled trees also contain volatile sap, so as a whole, they are a more volatile fuel type than leafy trees (Alberta Government 2012). Due to these differences in volatility, fire managers often treat deciduous trees and grass fields as fuel breaks. Once the fire reaches those fuels, it will stop or slow enough to be stopped by suppression resources.
The Alberta government made this pamphlet, which is linked and provides more details as to how different tree species burn: How different tree species impact the spread of wildfire.
Understanding how fire responds to fuel types at different times of the year is essential to making better-informed management decisions. Guiding where to prioritize suppression resources and understanding what fuel types may act as fire breaks or slow fire spread will aid in mitigating wildfire damage. If fire seasons are going to start earlier, a better understanding of fires' relationship with fuel in the spring is vital.
"Spring dip" and other seasonal changes to fuel types have been part of wildland fire managers' collective consciousness for years (Jolly et al. 2016, Parisien et al. 2023). A prime example of these spring factors contributing to a large fire is the Horse River Wildfire that hit Fort McMurray in 2016 (Parisien et al. 2023). Understanding their true impacts and the true impacts of climate change will allow for a better understanding of fire perimeter formation. In a world where fire is seemingly only getting more challenging to stop, do less volatile fuels still stop fires? Or is all we can do pray for rain? What was previously considered a fuel break may now need to be treated as a potential spread area.
Hypothesis
With all the above in mind, this study set out the following hypothesis:
H01: Seasonal fuel types are not a reliable fuel break under current climatic conditions.
H1: Seasonal fuel types are reliable fuel breaks under current climatic conditions.
H02: Seasonal fuel types are not a reliable fuel break in early-season wildfires
H2: Seasonal fuel types are reliable fuel breaks in early-season wildfires.
If this hypothesis is found to be likely to be true, then fire managers can follow the status-quo fire management when working on early-season fires. If these hypotheses are not supported an area that generally would halt or slow a fire may need to be reinforced with air tanker retardant drops or dozer guards to aid in slowing the fire's spread. If fire seasons like 2023 are a new precedent, managers must learn to adapt to the changing climate. This study will provide some knowledge to aid in their work.
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