Factsheet: Managing wildfire hazards while growing community canopies

Urban forests are vulnerable to wildfire and, when left unmanaged, they can even help wildfire spread. This factsheet explains how urban foresters, planners and their partners can create wildfire-resilient communities by assessing risks and addressing them in urban forest management. 

Wildfire hazards and urban forestry

Wildfire occurs naturally. It supports many grassland and forest landscapes across Canada to sustain their health, function and biodiversity over time. Many ecosystems depend on periodic fire to maintain community structure or to recirculate organic matter into the soil. In recent years, though, the frequency and severity of wildfires in Canada have increased. This is being caused by both historical land management practices and climate change impacts: hotter and longer summers, prolonged droughts and unpredictable winds.  

Severe fires can have numerous impacts on urban forests. These can range from biophysical impacts (e.g., tree death or damage, loss of habitat and forest structure, and soil degradation) to impacts on people and infrastructure in and around the urban forest. Severe fire not only directly threatens human health (both physical and mental) and safety, but it can also cause long-term changes to the tree canopy that worsen the urban heat island effect, increase stormwater runoff, prevent recreational use of the land and raise operational costs.

Identifying and managing wildfire hazards is an important part of urban forest management. It helps build community resilience and minimizes harm to people, trees, and infrastructure.  

Assessing wildfire risk 

Managing wildfire hazards begins with assessing risk. In urban forestry, wildfire risk assessments can help guide decisions around tree removal, pruning and other forest management activities. On the flip side, they can also help us to prioritize tree planting and avoid unnecessary removals in lower-risk areas.  

In emergency planning, risk is commonly framed as a combination of the probability (or threat) of a hazard and its consequences. To assess the risk of wildfire, we need to be able to: 

1. Accurately characterize the likelihood of wildfire occurring.
2. Identify the potential consequences of wildfire, so we can prioritize areas for protection and mitigation. 

Probability

The probability of severe wildfire is controlled by three factors—vegetation (fuels), weather and terrain—that make up the fire behaviour triangle. 

Fuels 

Fuels include all the combustible biomass in the environment, including trees, other plants and soil organic matter. Some plants are less susceptible to ignition than others. For example:  

• Deciduous species typically have higher moisture content in their leaves and needles during the growing season than evergreen trees, making them more fire-resistant.
• Broadleaf species are usually less susceptible than coniferous species, which often produce flammable resins and oils.
• Woody (hard-stemmed) plants take more energy to ignite than herbaceous plants, although they can burn longer and with higher severity.  

Weather 

Weather also affects fire potential significantly. For example: 

• Wind accelerates the spread of fire and increases its intensity.  
• Temperature, humidity and precipitation control fuel dryness and ignition susceptibility.  
• Storms bring lightning, which can cause ignition.  
• Changing weather conditions caused by climate change are helping to create longer fire seasons. Think increased summer drought, reduced winter snowpack and warmer temperatures. 

Terrain 

Terrain reflects how slope, aspect (the direction a surface faces) and topography influence the way wildfire spreads. For example: 

• On steep slopes, wildfire tends to pre-heat uphill vegetation, enabling faster spread.  
• Ravines, hillsides and other landforms channel fire and wind.
• Waterbodies and bare rock can act as fuel breaks. 

Consequences 

The consequences of severe wildfire refer to the scale of its potential impact. This includes impacts on the urban forest, as well as people, homes, businesses and critical infrastructure, like fire halls and water treatment plants.  

In the wildland–urban interface, i.e., where human development and natural areas meet on the landscape, the probability of ignition is higher, and the consequences of wildfire are likely to be more severe. Wildfire risk is therefore usually higher in these areas. Wildfire can spread rapidly in the wildland–urban interface, often because embers travel to building surfaces or adjacent materials, debris and vegetation. This usually occurs within 100 metres, but embers can sometimes travel across several kilometres. 

Tools for wildfire-ready urban forest management

Good urban forest management practices can help reduce the risk of wildfire. Activities around tree planting, landscaping, debris and waste management, ecological restoration, and forest health all impact vegetation (i.e., fuel) in the wildland–urban interface. Urban forestry activities may also overlap with community planning and emergency management decisions. 

Getting familiar with FireSmart™ 

FireSmart is the national program for wildfire preparedness and response planning. The program is co-ordinated by the Canadian Interagency Forest Fire Centre and used by partner agencies in each province and territory.

Key FireSmart resources include tools that can be used by local staff and homeowners to assess site-level ignition pathways and recommend appropriate landscaping (for example, see the FireSmart landscaping guide). Some provinces, such as British Columbia, have prepared their own FireSmart landscaping guidance. Communities with active FireSmart programs usually offer a variety of other services, often including assessments for homeowners. 

Using FireSmart for urban forestry 

FireSmart is organized around seven “disciplines”, several of which overlap with common urban forest management activities. The following strategies complement FireSmart and may help urban foresters and other community members increase wildfire awareness. 

Emergency management and preparedness 

Although they’re not directly responsible for emergency management, urban foresters can contribute to this area in important ways. You can:

• Seek out relevant information about your community’s context and hazard exposure, such as a local hazard, risk and vulnerability analysis or community-scale wildfire hazard mapping.
• Advocate to council for a local wildfire risk assessment if one does not already exist. This is often done together with emergency services staff and provincial/territorial wildfire agencies.
• Develop inventories of the at-risk trees, natural spaces and infrastructure that you manage (e.g., significant or heritage trees, rare and legally protected habitats, park infrastructure) as well as common ignition hazards (e.g., unauthorized fires, smoking, vehicles).  
• Prepare emergency procedures for post-fire clean-up and damage assessment. Following a wildfire, some trees may be damaged and unsafe, requiring pruning or removal to reduce risks to workers and the public. 

Day-to-day urban forest operations

Day-to-day urban forest management practices can increase your community’s wildfire resilience. In high-risk areas, you can:

• Promote the use of fire-resistant species (e.g., deciduous trees) and reduce planting density within 30 metres of homes and buildings.
• Avoid using combustible mulches within 1.5 metres of at-risk buildings and infrastructure and reduce the amount applied within 30 metres of them. Apply mulch in the fall and use smaller pieces to encourage decomposition.
• Prune strategically to create vertical and horizontal separation between vegetation and infrastructure. Strategic pruning can help you avoid unnecessary tree removal.
• Collect or manage debris from operations, such as woodchips, and consider techniques like xeriscaping or low-water landscaping around trees to reduce water demand.
• Enact policies or practices to limit higher-risk activities, such as burning green waste or lawnmowing, during periods of greater fire danger.  
• Consider offering field staff basic training in firefighting and ignition control using hand tools to put out any small fires encountered during regular operations.
• Integrate wildfire mitigation principles in forest health, integrated pest management and invasive species programs. In general, practices to promote forest health are already aligned with reducing wildfire hazards (e.g., reducing overall tree mortality and removing fine debris), but they should include careful monitoring and debris management to further address hazards.
• Plan strategically for vegetation management in high-risk natural areas with a qualified professional. For more on this type of project, see our wildfire resilience toolkit for small communities.

Community and development planning

Urban forest management is intrinsically linked with community and development planning decisions. It is important to consider connections between wildfire risk and urban forest management within long-range plans, development controls and the planning of natural areas/parks. You can:

• Include guidelines on wildfire risk in community-wide plans and encourage their consideration in neighbourhood and site planning, park management or general landscaping.  
• Consult with your planning department about available mechanisms to require submissions from qualified professionals (e.g., registered foresters, landscape architects) for development approvals, like rezoning or subdivision. Submissions could include FireSmart assessments, landscape plans, or documentation of vegetation management/hazard mitigation, as relevant.
• Enact regulations or offer voluntary guidelines for landscaping on private property, particularly in areas of high or extreme risk. These could include recommendations on tree species, spacing and maintenance, adapted from FireSmart guidelines for the local context.
• When planning natural areas, complete wildfire hazard assessments as an early part of the design process. These assessments can influence decisions related to park facilities and planting, as well as preserving access to natural areas for firefighting and vegetation management. 

Engagement

Community members have safety and wildfire risks top of mind, so they may come to urban foresters and planners with questions related to tree management in their neighbourhoods. It’s important to be able to effectively communicate strategies for planting, species selection and vegetation management when representing urban forestry activities to the public. You can:  

• Tag planted trees with wildfire resilience information. For example, FireSmart BC has a plant program that local governments can use to tag suitable species. Similar tagging could be done for tree planting in parks. Or you can place signage at natural restoration sites to explain that planted trees are relatively low-hazard.  
• Share relevant wildfire hazard findings during park or planting plan consultations.  
• Host public education in areas where vegetation management has been implemented to demonstrate the outcomes.  
• Use digital media to explain changes in landscaping practices, like mulching, that may be made in public places to promote wildfire resistance.  
• Link to local government or FireSmart landscaping guidance in posts on social media. 

Further reading

• Natural Resources Canada, Fire management
• Tree Canada, Fire and the urban–rural interface
• Canada Wildfire, Wildfire facts
• Government of British Columbia, Hazard, risk and vulnerability analysis guides and worksheets
• National Research Council Canada, National guide for wildland–urban interface fires
• FireSmart BC, Find fire-resistant plants for your climate 

This resource was created in partnership by Tree Canada and FCM’s Green Municipal Fund for the Growing Canada’s Community Canopies initiative, which is delivered by the Federation of Canadian Municipalities and funded by the Government of Canada.