Canadian wildfire activity is increasing in part because human-caused climate change is causing more hot and dry weather conditions conducive to wildfires, also referred to as “fire weather”. Future patterns of fire weather will look different from the past – conditions have already changed and will continue to do so. Understanding this change will be important for building resilience to wildfires.
Canadian wildfire activity is increasing in part because human-caused climate change is causing more hot and dry weather conditions conducive to wildfires, also referred to as “fire weather”.1 As climate change progresses, longer fire seasons and worsening fire weather conditions are expected in many regions of Canada, leading to more intense and frequent wildfires.2,3 Future patterns of fire weather will look different from the past – conditions have already changed and will continue to do so. Understanding this change will be important for building resilience to wildfires.
To help Canadians respond to shifting wildfire danger, the Fire Weather Projections application provides future projections of fire weather using visuals and data. This guidance article, and others, are available in the application to help users confidently apply this information.
Wildfires are a common natural occurrence in Canada and play a critical role in the ecology of forests, grasslands, and other ecosystems. In addition to naturally ignited fires, Indigenous peoples have used cultural burning for millennia to steward ecosystems and biodiversity. Generally, wildfires occur more often and are more severe when there is:
Together, these three factors are often referred to as the fire regime triangle – and characterize the key drivers of regional fire activity. The information in the Fire Weather Projections application focuses on the weather aspect of the fire regime triangle and how this will evolve as the climate changes. However, due to direct human activity and climate change, vegetation and ignition sources will also change over time. For example, forestry operations may change the type and amount of vegetation, affecting the fuel available to burn. Due to climate change, lightning – which historically has started roughly half of Canadian wildfires – is becoming more common in regions where it was relatively uncommon in the past.5 This app provides data on how fire-conducive weather conditions are projected to change in a changing climate. For a more holistic assessment of future wildfire danger, this information should be evaluated alongside considerations of how fuels, ignition sources, and the landscape are projected to change.
The fire regime triangle. Climate (the long-term statistics of weather) is one of three key factors that affect wildfire activity.
Wildfire risk considers both the likelihood and severity of a wildfire (in this case, the “hazard”) combined with the consequence of a potential fire, including what things are present (“exposure”) and how vulnerable those things are to fire (“vulnerability”). As described above, fire weather is one factor that affects potential fire frequency and severity, which, in turn, is one aspect of overall wildfire risk. This is illustrated in the graphic below.
The relationship between fire weather and wildfire risk. Climate (the long-term statistics of fire weather), ignitions, and vegetation are three key factors that affect fire danger and ultimately wildfire activity – in this case, the hazard of concern. In turn, this hazard can be related to wildfire risk by also considering the vulnerability and exposure of at-risk communities. Fire weather is only one of several components that must be considered to assess overall wildfire risk.
Canadian forest fire professionals use the Canadian Forest Fire Danger Rating System (CFFDRS) to estimate wildfire danger, or the potential for wildfire ignition, spread, and intensity. The CFFDRS considers all the factors in the fire regime triangle, as well as other wildfire controls like topography (landscape features). Within the CFFDRS, fire weather is described by a system called the Canadian Forest Fire Weather Index (FWI) System. Because it is widely used for wildfire planning in Canada, the future fire weather data provided in the Fire Weather Projections application is based on this system. Understanding FWI System basics is one important part of understanding future wildfire danger.
The FWI System is comprised of codes and indices that reflect the potential impact of weather on different aspects of wildfire. Each of these, described below, provides different measures of hot, dry and/or windy conditions and their potential impact on wildfire.
The first three FWI System components are called the fuel moisture codes, because they describe the dryness of wildfire fuel at different layers of the forest floor based on weather conditions.6
The last three FWI System components describe how wildfires might behave, if started.
Each of the FWI System codes and indices become larger as the weather becomes drier, hotter, and/or windier – as fire weather gets worse. Due to differences in forest type (the wildfire fuel), FWI System values are interpreted differently depending on the region. For example, each Province and Territory uses the FWI System in slightly different ways to understand fire danger (e.g., different thresholds for “extreme” fire danger). Knowledge of regional characteristics is key for using FWI System values in local planning.
Environment and Climate Change Canada has used climate model projections to determine estimates of changing FWI System indices through the 21st century. The resulting data product, which may be accessed via the Fire Weather Projections application, is called CanLEAD-FWI.10
In CanLEAD-FWI, six FWI System components are estimated from 1950 to 2100 on a grid of approximately 50 km by 50 km. Standard metrics describing projected changes to high fire weather severity and frequency, as well as fire season length have been precalculated. These metrics, available in gridded format, describe how climate change will impact the severity, frequency, and duration of fire-conducive weather conditions. For users familiar with the FWI System, locally relevant thresholds can be used within the application to calculate customized metrics over the entire 1950 to 2100 period. These customizable metrics are only available for locations with historical station-based observations.
For more information on interpreting and using CanLEAD-FWI, as well as data limitations, see the Guidance tab in the application, including: