What comes to mind when thinking of an urban forest? Street trees? Trees in containers on sidewalks? Forests in ravines? Backyard trees on lot lines? In fact, urban forests encompass all those things and more. 

Since the mid-20th century, urban areas in Canada have experienced significant growth and increased population density, which has brought many environmental, ecological, and social problems to the surface. These have underscored the importance of developing greener cities and heightened the need for the conservation and management of urban trees. Over time, urban greening attention has moved from a tree-by-tree management approach to one that recognizes the importance of all trees in urban areas (Konijnendijk et al., 2004).  Terms like "urban forest," "urban forestry," and "urban tree canopy" have emerged, and their definitions have developed over time. While these three terms are related and often used interchangeably, it is important to recognize the differences between them.

Key Terms in Urban Forestry

There are several detailed definitions of urban forest and forestry that have been used in Canada. In general, the urban forest is defined as a collection of all trees, woody plants, and vegetation within urban areas (Jorgensen, 1974). Broadly speaking, urban forestry is a specialized yet multidisciplinary branch of forestry focusing on forest and tree management techniques and practices that range from planning, planting, maintaining, and protecting trees to public engagement and education (Deneke, 1993). Urban tree canopy is a two-dimensional expression of an urban forest and a measure of the extent of tree canopies that shade the ground (CSLA, 2024; Vogt, 2020). Easily mappable using modern spatial technologies, the urban tree canopy is often used as a simple and general measure of urban forests, enabling urban forest quantification, comparison, and monitoring over space and time (Tree Canada, 2019).

The approach to thinking of trees in urban areas as a forest was prompted by the loss of American elms (Ulmus americana) due to the impacts of Dutch Elm Disease (DED) in North American cities in the 1960s. DED, a vascular wilt fungus, killed most American elms in urban areas and devastated the tree canopy cover in many Eastern American and Canadian communities. The sudden loss of tree canopy left streets and neighbourhoods without sufficient canopy cover and shade, leading to a significant public outcry for conserving and managing urban trees. The movement mobilized forestry professionals and scientists to recognize and value urban forests as critical natural resources in urban areas. Society had started to recognize that urban forests were critical for providing diverse environmental and social benefits and making urban areas livable. 

Subsequently, the importance of all trees growing in urban areas was recognized, and the terms "urban forest" and “urban forestry” were coined. The terms were defined in 1965 by Dr. Eric Jorgensen at the Faculty of Forestry, University of Toronto, Canada. Dr. Jorgensen first defined the term "urban forestry" as “a specialized branch of forestry and [it] has in its objectives the cultivation and management of trees for their present and potential contribution to the physiological, sociological, and economic well-being of urban society. These contributions include the overall ameliorating effect of trees on their environment, as well as their recreational and general amenity value." (Jorgensen, 1974). He also believed that urban forestry extends beyond "the city trees or single street management, but rather the tree management in the entire area influenced by the urban population." (Jorgensen, 1974).

Definitions Over Time

Dr. Jorgensen’s original definition of urban forestry was enhanced and developed over time. In 1993 at the first Canadian Urban Forest Conference, Frederick Deneke expanded on the term, stating: "Urban forestry is the sustained planning, planting, protection, maintenance, and care of trees, forests, greenspace, and related resources in and around cities and communities for economic, environmental, social, and public health benefits for people. The definition includes retaining trees and forest cover as urban populations expand into surrounding rural areas and restoring critical parts of the urban environment after construction. Expansion at the urban/rural interface raises environmental and public health safety concerns, as well as opportunities to create educational and environmental links between urban people and nature. In addition, urban and community forestry includes the development of citizen involvement and support for investments in long-term ongoing tree planting, protection, and care programs." 

Over the years, with growing knowledge and a better understanding of the significance and value of the urban forest, more foresters and professionals began working in the field of urban forestry, and urban forest definitions started to surface in professional documents and acts in Canada. For example, the Ontario Government's Professional Foresters Act of 2000 defines urban forests as "tree-dominated vegetation and related features found within an urban area, and includes woodlots, plantations, shade trees, fields in various stages of succession, wetland and riparian areas." In 2021, the Act's urban forest definition was enhanced, and the term "urban woodland" was added to include urban natural areas such as "woodlands found in an urban environment, including those in riparian areas, ravines and wetlands" (Professional Foresters Act, 2000).

Along with the definition of urban forests and urban forestry, the importance of strategic and planned urban forests and their management became apparent. Kenney (2003) pioneered the idea of strategic urban forest management planning and emphasized the importance of strategically managing all urban forest components and associated biotic and abiotic elements across a wide range of urban areas, from large to small communities, and in the areas between them. As such, strategic management of urban forests across a range of urban spaces, such as streets, parks, cemeteries, arboretums, private properties, and natural forest fragments, was implemented. All urban forest elements were recognized as the backbone of green infrastructure, and the contribution of urban forest to connecting urban and rural green areas and its contribution to improving the urban environment (GIOC 2015; NRCan and Canadian Forest Service, 2022).

Building on Kenney’s (2003) idea of the importance of strategic urban forest management and recognizing the ecological and social importance of urban trees within and outside the boundary of urban areas, the 2019-2024 Canadian Urban Forest Strategy (CUFS) defines urban forests more comprehensively as the "trees, forests, greenspace and related abiotic, biotic and cultural components in areas extending from the urban core to the urban-rural fringe" (Tree Canada, 2019). Additionally, the CUFS definition of urban forestry also includes "the sustained planning, planting, protection, maintenance, management and care of trees, forests, greenspace along with related resources in and around cities as well as communities for economic, environmental, social, and public health benefits for people." It also recognized "techniques associated with retaining trees in the context of densification, forest cover in the context of urban expansion into surrounding rural areas, and greening critical parts of the urban environment after development and urbanization." The CUFS acknowledges that "As the geographic and social distinctions between urban and rural become less clear, urbanization raises environmental and public health and safety concerns, thereby creating a need for educational and environmental links between urban people and nature. Urban forestry is multidisciplinary and multifaceted, comprised of many actors in research, policy, practice, and community engagement. Urban forestry includes the development of citizen involvement and support for investments in long-term on-going tree planting, protection, and care programs."

Defining Urban Areas

While definitions of urban forests use the term “urban” to describe the bounds of the urban forest, this raises the question of how to define the term "urban." In Canada, the definition of urban areas has evolved over the years. In the 1931 Canadian Census, an urban population is defined as a "population residing inside boundaries of incorporated cities, towns, and villages, regardless of size." After 1951, however, urban areas in Canada began to be defined by their population size and, later, by population density. The 1971 Canadian Census, based on population count and density at the time, stated, "An urban area has a minimum population concentration of 1,000 persons and a population density of at least 400 persons per square kilometre." In 2008, Statistics Canada recognized that there are two classes of populated areas in Canada: urban areas and rural areas, and they further define urban population specifically as "all population living in the urban cores, secondary urban cores and urban fringes of census metropolitan areas" (Statistics Canada, 2008). 

Consequently, as the definitions of urban areas and urban population have evolved spatially and structurally, the definition of urban forest also advanced to include trees and associated vegetation found in areas deemed metropolises, cities, towns or villages, and areas impacted by the urban population. It has also been recognized that urban forests and urbanization are interdependent and that urban forests extend beyond the city limits and are not constrained to municipal borders (Tree Canada, 2019). Urban areas and their populations benefit from the forests and woodlands outside urban boundaries. These forests and trees, between urban and rural areas, within the zone of urban influence often termed peri-urban forests (FAO, n.d.; Salbitano et al., 2016), provide recreational opportunities for urban dwellers, support biodiversity conservation, and, although outside urban areas, contribute to regulating urban climate and hydrology, improve air and water quality, and provide aesthetic and cultural value. However, the pressures from urbanization, development, and the urban population negatively impact forests and the natural environment in peri-urban areas, often resulting in fragmented forest patches and forests that are permanently lost or altered due to development (Puric-Mladenovic, Kenney & Csillag, 2000). Understanding and recognizing the interdependence of urban and peri-urban areas, as well as the similarities and connections between peri-urban and urban forests, is critical for strategic urban forest management and planning (Kenney & Rosen, 2003; Konijnendijk et al., 2004; Salbitano et al., 2016).

The history of urban forests and forestry in Canada and the relationships between people and urban trees are deeply rooted in the natural environment and diverse cultural values of Canadians. Land and forest stewardship that is based on a deep respect for the natural world and harmony with nature has been practiced by Indigenous peoples who have been stewarding the land and waters for millennia (Artelle et al., 2019). Canadian cities and towns have been established on the traditional ancestral territories of First Nations, Inuit, and Métis people, whose rights assert their authority to exercise their own jurisprudence and decision-making on these lands (Reo et al., 2017; Artelle et al., 2019; Dietz et al., 2021; Moola et al., 2024). 

However, these rights were not recognized by English and French colonizers, who brought their European land use values and drastically changed the land and forest. They stripped Indigenous people of their land, resources, rights, knowledge, governance, and their way of land stewardship (Youdelis et al., 2021; Mansuy et al., 2023; Townsend and Roth, 2023). European settlers perceived the land primarily as a resource for extraction and an opportunity for short-term profit. This mindset led to rapid changes and degradation of the forests and lands. What was once a lush landscape, rich with forests and wetlands, was permanently changed due to deforestation, resource extraction, and the establishment of permanent settlements, villages, towns, and farms.

European settlers established permanent villages and towns, introducing various new land use practices, including farms, residential areas, permanent roads, railways, parks, cemeteries, and industrial zones, to name a few. These changes in land use, coupled with a century of intensive deforestation and degradation, resulted in environmental problems such as erosion and stream sedimentation within a few decades of settlement (e.g. In Ontario by the late 1800s). Driven by the economic cost that environmental degradation and deforestation caused, the first government-led conservation movement started in Ontario at the turn of the 20^th century. Trees, once seen solely as timber value and revenue, were recognized as being important for stabilizing soils, sheltering homes from winds, providing shade, stopping stream sedimentation, and providing food and beauty around homes and settlements.  Due to poor environmental conditions in urban areas, city dwellers began to yearn for more green spaces and escape to natural surroundings outside the cities. This prompted the creation of some of the first parks within or in proximity to urban centres, such as Stanley Park in Vancouver, BC (1888), High Park in Toronto, ON (1873), Mont-Royal Park in Montreal, QC (1876), and Point Pleasant Park in Halifax, NS (1866). These early urban parks are now iconic and indispensable to the urban fabric of these cities. 

The creation of natural and manicured parks, urban tree plantings, and the practice of European-style gardening and beautification spread across towns and villages and expanded over time. Urban trees were planted and enjoyed for their shade, exotic properties, and beauty. As such, groups dedicated to ‘urban greening’ started to form in cities, such as the Toronto Parks, Forestry and Recreation group established in 1884 under the name "Committee on public walks and gardens", and the "Vancouver Park Board" in 1886. For Ottawa, the first municipal response related to urban trees was a bylaw passed in 1869 (Dean, 2005). 

In the early 1900s, a devastating fungal pathogen called Dutch Elm Disease (DED) reached Canada and decimated American elms (Ulmus americana), one of the most popular urban trees. Thus, the urban tree canopy of many cities in eastern Canada, at the time dominated by elms, was lost. Following the DED outbreak and tree canopy loss across eastern parts of the country, the public and decision-makers started to realize the gap left by the loss of many trees in their communities. The severity of canopy loss from one single pathogen also highlighted the risk of narrow tree selection and the vulnerability of overplanting one singular tree species. It also highlighted the need to strategically manage urban trees and parks to prevent such catastrophes in the future.

In the 1960s, this vulnerability was recognized by a forward-thinking forest pathologist named Dr. Erik Jorgensen, who was conducting research on tree diseases, including DED, at the University of Toronto. Prevention and tree-protection measures had been one of the main focuses of his work for nearly a decade. In the 1950s, he estimated that ninety percent of the trees on the University of Toronto St. George campus were American elms (Ulmus americana) vulnerable to DED (Dean, 2009). As a researcher, he witnessed the devastation that DED caused while recognizing that the problem could have been mitigated by proper tree management and care. Dr. Jorgensen and Brigadier J. F. Westhead lobbied municipal politicians and representatives to create a united front against DED, establishing the Dutch Elm Disease Control Committee for Metro Toronto in 1962. 

Eventually, the loss of elms and tree canopy in urban areas was so significant that Dr. Jorgenson coined the term "urban forestry" in 1974 and pioneered the first urban forestry program at the University of Toronto. Once defined, urban forests became more recognized and urban tree management and similar departments were created in larger cities, such as Toronto in 1965 and Montreal in 1977 (Jorgensen, 1974; Desbiens, 1998). While these departments were under various names, such as parks and recreation, they started to practice ‘urban forestry’ and related activities. In many cities, these departments have since been re-named and are now urban forestry departments, while some cities still practice ‘urban forestry’ under various municipal departments (Puric-Mladenovic & Bardekjian, 2023) or agencies within a city. For example, urban forests and trees in Ottawa are managed by several bodies, including the National Capital Commission, the Federal Ministry of Transportation, Hydro Ottawa, Planning, Infrastructure and Economic Development Department, and the Public Works and Environmental Services Department, to name a few (Bider, 2024). 

In the mid-1970s, with the expansion of urban forestry across larger municipalities, the Dutch Elm Disease Control Committee of Toronto (piloted by Dr. Jorgensen) expanded into the Ontario Shade Tree Council, a province-wide network with a broader mandate of managing trees in the urban area (Dean, 2009). About the same time, the first federal urban forestry program called 'A Forest for Man’ started. While it only lasted until 1979, the movement continued with the first International Conference on Urban Forests that same year, which was held at Laval University (Rosen & Tree Canada, 2015). 

In the next couple of decades, while many municipalities across Canada had developed urban forestry or urban forestry-related departments, there was still a lack of cohesion across provincial and national scales. To address this gap, an NGO called Tree Canada was established in 1992 (Tree Canada, 2024). Being the only national NGO with an urban forestry portfolio, Tree Canada partnered with the Ontario Shade Tree Council as well as professionals pioneering urban forestry in Canada to organize the first Canadian Urban Forest Conference (CUFC) in 1993 in Winnipeg, Manitoba. Tree Canada continued to organize bi-annual conferences, allowing professionals from across Canada to gather and share new innovations and knowledge regarding urban forestry practices, policies, and research (Tree Canada, 2024; Tree Canada, 1993). As an outcome of the 5th Canadian Urban Forest Conference in 2003, the Canadian Urban Forest Network (CUFN) Listserv for urban forestry was formed and the Canadian Urban Forest Network was established as a result (CANUFNET, 2024; CUFN, n.d.).

Urban forestry in Canada continued to evolve from the 1990s to the early 2000s. Another urban forest vulnerability wake-up call came in the early 2000s due to the impact of the Emerald Ash Borer (EAB) and the loss of ash trees across Ontario and Quebec. Once again, the loss of urban trees prompted increased interest in the conservation of trees, resulting in another jump in urban forestry programs across municipalities. In addition, urban forests and urban forestry were integrated for the first time into Canada's National Forest Strategy for 2003-2008 (NFSC, 2003). Since 2010, urban forestry as a field has grown across Canada, and about 50% of municipalities with a population greater than 3,000 are funding some form of urban forestry or urban greening department (Puric-Mladenovic & Bardekjian, 2023).

As new environmental and social issues arise in urban areas across Canada, public interest in urban forest conservation and community stewardship of trees is increasing. The goals and values of urban forestry are continually evolving. What initially started as a response to pest control has expanded to include various aspects of urban trees, their value, and management. New topics have emerged, such as green infrastructure, asset management involving trees, and natural climate solutions. Urban forestry in Canada has a rich history, and it continues to develop alongside the growth and intensification of urban areas as well as public awareness about trees and urban forests.

Urban trees, individually or collectively as urban forests, provide diverse ecological services, some of which can be monetized and provide economic value to society. Ecological services of urban forests, in general, include regulating, provisioning, supporting, and cultural services (Filho et al., 2020). Urban forest regulating services have the ability to moderate the environment via climate regulation, flood control, air pollution removal, and carbon storage. Provisioning services provide tangible products such as food, water, wood, and medicinal plants (Visentin, 2019). Supporting services are natural processes that sustain life, including nutrient cycling, soil creation, biodiversity, habitat, oxygen production, photosynthesis, biomass production, erosion control, and the water cycle (Przewoźna, 2022). For example, urban forests support biodiversity through pollination and seed dispersal, and provide wildlife habitats for birds, mammals, and invertebrate species (FAOUN, 2022; Pickett et al., 2016). Cultural services of urban forests benefit humans when they directly or indirectly interact with trees. Compared to regulating, provisioning, and supporting services, cultural services are often harder to quantify and monetize, yet they improve the quality of human life by providing aesthetic, recreational, and restorative values (NWF, n.d.). The practice of urban forestry, which includes management and planning associated with maintaining and protecting urban forests and green spaces, also supports a steady flow of ecological services to society (Tree Canada, 2019; Salmond et al., 2016). It also provides economic benefits in terms of job creation, reduced infrastructure maintenance, and other direct and indirect benefits (Filho et al., 2020).

Climate & Urban Sustainability

With rising concerns about climate instability and government commitments to environmental sustainability and biodiversity conservation, urban forests and urban green spaces are being recognized as natural climate solutions and integral tools for improving the quality of life in urban areas. With nearly 75% of Canadians living in urban/metropolitan areas (StatCan, 2022), integrated land use planning and urban forest management efforts are required to maintain the quality of urban life and city livability in the face of climate change and environmental challenges. 

As the negative impacts of climate change, urban sprawl, and intensified development continue to grow, public awareness of environmental issues is also on the rise. Many people recognize the importance of urban forests and the ecological services they provide. As a result, urban forestry has become a prominent topic in discussions related to municipal policy and decision-making across Canada. Recognizing these challenges and the need to increase urban forest cover to obtain the benefits that trees provide, Canadian cities have set some of the most ambitious urban forest canopy goals. For example, many major Canadian cities, including Vancouver, Halifax, Montreal, Ottawa, and Winnipeg, have pledged to increase urban tree canopy cover by more than 25% by 2030 (CCI, 2021), and Toronto has set an ambitious 40% target by 2050. For example, with over 11.5 million trees and around 1,500 urban parks and green spaces, Toronto has been integrating urban forest into urban land use fabric with an aim to become one of the most forested cities in Canada (City of Toronto, 2024; City of Toronto, n.d.). 

The benefits of urban forests across various land uses and green spaces are far-reaching in Toronto. According to multiple health indicators, notably cardiovascular and respiratory health (StatCan, 2019), Toronto is one of the healthiest cities in Canada. Other Canadian cities, such as Ottawa, Winnipeg, and Metro Vancouver, are also developing and implementing management, operations, maintenance, and protection strategies to manage urban green spaces and receive the full benefits of urban forests and green spaces. Ecological services provided by urban forests and green spaces have been shown to vastly improve the quality of life in urban areas by also improving mental health and promoting social cohesion (Tree Canada, 2019). Epidemiological studies have shown that even brief experiences in natural settings can reduce neural activity in the subgenual prefrontal cortex, indicating a reduction in feelings of stress and anxiety (Bratman et al., 2015). When congruent experiments were conducted in urban areas lacking nature, the same effects were not observed (Bratman et al., 2015).  Medical studies highlight urban naturalized areas and green space as essential for enhancing mental health in urban environments (Astell-Burt & Feng, 2019; Rugel, Carpiano, Henderson & Brauer, 2019). A direct link has also been drawn between tree canopy cover and social capital, where urban neighbourhoods with more tree cover have more social networks and a greater sense of cohesion, and also further benefit from improved mental health (Holtan, Dieterlan & Sullivan, 2014). 

When access to treed green spaces is available, Canadians tend to use them, increasing the likelihood of social interaction while encouraging diverse recreation activities across all demographic spectrums (Koley, Kuo & Sullivan, 1997). Proximity and availability of green space within urban areas encourage physical activity, which further benefits the mental health of urban residents while improving general indicators of physical health (FAOUN, 2022). Greener urban areas have shown a positive association with better cardiovascular health, lower blood pressure, reduced incidences of obesity, asthma and diabetes, and improved memory and attention span (Richardson et al., 2013; Pretty et al., 2006; Kim, Lee & Ramos, 2021; Tree Canada, 2024; Kardan et al., 2015). 

In addition, urban trees are also crucial biofilters because they capture atmospheric pollutants and particulates in city air, keep the air cleaner, and reduce the severity of respiratory-related conditions and illnesses (Wolf et al., 2020). Urban trees in Canada are responsible for sequestering and neutralizing around 2.5 million metric tonnes of atmospheric carbon every year (Steenberg et al., 2023). Trees can reduce ambient temperatures by 2-5 degrees Celsius in urbanized areas, combating negative health outcomes related to high temperatures in summer months (NRCan, 2016).   

Quantifying Urban Forest Benefits 

Urban areas with extensive and diverse green spaces and strong urban forestry practices benefit from increased urban forest ecological services (FAOUN, 2022). Overall, urban forests across cities in Canada provide various benefits, and many municipalities have quantified and mapped urban forest services (i-Tree, 2024; Town of Oakville, 2016). Urban forest inventory and monitoring are a foundational step toward quantifying urban forests and the benefits they provide. Depending on the method and tools used, it is possible to estimate and quantify urban forest services and track them over time by utilizing urban canopy mapping, tree species measurements, and tree health data. 

One such tool used for estimating ecological services is i-TreeEco, developed by the USDA Forest Service. i-Tree provides forestry analysis tools at the level of individual trees to entire stands, benefits assessment tools, and a database to support quantifying forest structure and guide decision-making (i-Tree, n.d.). i-Tree has been used across over 20 municipalities in Canada to estimate ecological services (i-Tree, n.d.).   

One of the many benefits of the urban forest is its ability to ameliorate urban microclimate, cool large or small areas, and benefit human health. Cities tend to have higher ambient air temperatures than rural areas due to the high heat absorption capacity of various building materials (GoC, 2022). Concrete, asphalt, and cement absorb sunlight and trap heat much more effectively than trees, parks, and fields, leading to higher air temperatures in built-up areas (USEPA, 2024). Cities also produce their own heat, which is released by vehicles, air conditioners, and machinery (Climate Atlas of Canada, n.d.). Trees and green spaces can improve urban climate, reduce surface and air temperatures, cool the environment, improve the comfort of citizens by providing shade, and mitigate the effects of urban heat islands through evapotranspirative cooling (Yin et al., 2024; Schwaab et al., 2021). The combined effects of evapotranspiration and shading can reduce summer temperatures by 1–5°C (USEPA, 2008).

The urban heat island effect in cities across the globe is amplified by climate warming. Urban forests and green infrastructure are recognized as nature-based solutions and natural capital investments for addressing climate change impacts (IFC, 2024). Canada, like many other urbanized countries, is facing challenges related to climate change and the urban heat island effect. These issues include the impacts of heat on human health, infrastructure, biodiversity, and wildlife. Urban areas in British Columbia and Quebec have experienced extreme heat, leading to an increase in heat-related illnesses and mortality during heat waves in recent years (Poitras et al., 2018; Beugin et al., 2023). The extent and distribution of urban tree canopy in Canadian cities can significantly benefit both human and environmental health, especially during the summer months. As a result, urban trees and green spaces are becoming increasingly valuable as climate change continues to drive extreme weather events, such as heat waves and temperature fluctuations (Health Canada, 2020).

UHI: Trees and Air Cooling

Many studies have documented across the globe that during the summer peak, air temperature in large cities with heat-absorbing surfaces and lack of green space could be as much as 10-15°C hotter than surrounding areas, while at night, the difference can be up to 12°C (Joint Research Centre, 2022; Mentaschi et al., 2022). This higher air temperature across urban areas is referred to as the urban heat island effect (UHIE). The UHIE phenomenon also impacts many cities across Canada. For example, it reached the highest daytime value of 7.25°C for Vancouver and the highest nighttime UHI intensity at 4.36°C for Toronto (Duan, Agrawal, Sanchez-Azofeifa, and Welegedara, 2024). When gray infrastructure absorbs heat from the sun, this heat is retained and slowly released even after the sun goes down, which keeps city temperatures higher during the night (USEPA, 2024).

Urban forests, trees, and urban greenery can help reduce UHIE by cooling city air temperatures through sunlight absorption, evapotranspiration, and interception of particulate matter. Evapotranspiration, the process that adds water to the air through evaporation from plants and surrounding soil, can reduce ambient air temperatures by 1-5°C (USEPA, 2024). Studies have found that greener urban areas are cooler on average than less-green urban areas, with urban forests having daytime temperatures about 1.5°C cooler than surrounding areas during summer months (Knight et al., 2021). Additionally, by intercepting greenhouse gases and particulate matter associated with air pollution from dust, car exhaust, and wildfires, urban trees use their leaves and needles to filter the air and reduce ground-level temperature by offsetting greenhouse gas emissions and reducing smog in cities (Knight et al., 2021).

Urban tree canopies provide much-needed shade and can reduce the amount of sunlight absorbed by gray infrastructure like buildings and roads (SFI, 2024). They help decrease the severity of this UHI effect by intercepting sunlight before it reaches buildings and roads. Additionally, the shade provided by urban trees can help decrease cooling-related energy costs by up to 7% in summer months by reducing the amount of sunlight absorbed by building exteriors, reducing cooling energy costs (Nowak, 2017). In addition to urban forests, green roof technologies can reduce roof surface temperature by up to 20°C, further asserting the benefits of vegetation and green spaces (USEPA, 2024). 

Canadian municipalities such as Kingston, Vancouver, and Surrey have successfully implemented diverse urban forestry initiatives to combat high temperatures and climate change. For example, Kingston’s urban forest has helped to combat the urban heat island effect by improving thermal comfort and reducing energy consumption associated with cooling (Guilbault, 2016). The City of Vancouver analyzed local climate zones to optimize tree planting locations, ensuring that urban trees contribute effectively to maintaining outdoor thermal comfort (Aminipouri et al., 2019); this approach highlights the value of local and site-specific urban forest planning strategies. Additionally, the City of Surrey has engaged residents in urban heat readiness by developing a conversation guide emphasizing the role of urban trees in mitigating heat waves and improving community resilience (City of Surrey, 2021). These are some examples of novel approaches to utilizing urban forestry as a tool to combat climate change and enhance human health in urban areas in Canada.

UHI: Human Health

As the climate changes in Canada, the role of trees in cooling urban areas and supporting human health becomes increasingly important. Urban forests serve as a crucial climate change mitigation measure. With rising summertime temperatures, the ability of trees to cool the air and provide shade is an essential resource for public health in Canada.

Heat waves and excessive temperatures yearly contribute to many illnesses and deaths in Canadian cities; these high temperatures can induce heat cramps, respiratory difficulties, heat stroke, and even heat-related mortality (GoC, 2020; Chen et al., 2016). By increasing daytime temperatures and reducing nighttime cooling, the urban heat island effect is responsible for over 45 deaths in Canada annually (StatCan, 2024). Young children under the age of 5, older people over the age of 65, people with chronic illnesses, homeless people, and low-income, low canopy cover communities are particularly at risk when it comes to heat-related illnesses and mortality (Climate Atlas of Canada, n.d.; Whittingham et al., 2022).  

Urban trees can reduce the severity of these health hazards through air cooling and shade provision, and the City of Toronto became the first Canadian municipality to develop a policy specifically related to urban trees and heat. In collaboration with many city departments and NGOs such as Parks, Forestry and Recreation, Child Services, Tree Canada, and LEAF, Toronto Public Health formed an interdisciplinary team to develop the first Shade Policy in Canada (City of Toronto, 2007, 2010). This initiative, led by the Toronto Cancer Prevention Coalition between 2005-2015, is the first of its kind. It represents an important step towards preparing for a warmer climate with increased frequency and duration of extreme heat events. 

The Toronto Cancer Prevention Coalition's shade policy initiative is a testament to the importance of shade in protecting against skin cancer. Integrating shaded areas, especially where the shade is created by trees, into urban parks, streets, schools, and facilities draws an important connection between urban forestry, urban planning, and public health (Sivarajah, Thomas & Smith, 2020). This policy officially recognized the value of shade trees in cities, especially large trees with dense canopies, in providing shade and lowering air temperatures, and created a policy framework to incorporate shade provision into planning, bylaws, and climate change and energy action plans (City of Toronto, 2010).  

Urban forests, providing multiple ecosystem services, offer a natural and sustainable solution for improving the environmental quality of urban areas through air purification, temperature regulation, and carbon sequestration. Trees, individually and collectively as part of urban forests, play a crucial role in enhancing air quality by filtering pollutants such as nitrogen dioxide (NO₂) and sulphur dioxide (SO₂). By absorbing these pollutants, trees metabolize and convert them into less harmful substances. They also trap particulate matter (PM) on their leaves, needles, and bark, effectively reducing their concentrations in the air. Research by Nowak et al. (2018) has shown that urban forests in Canada remove substantial amounts of air pollutants annually, leading to significant improvements in air quality and co-benefiting public health. An urban tree can absorb anywhere between 10 and 40 kg of CO₂ each year and can intercept up to 4.5 kg of pollutants such as NO₂, SO₂, dust, soot, and smoke (EcoTree, 2024; Vallet, 2005; Greener Seasons, 2022). 

Urban forests play a crucial role in helping communities deal with the impacts of climate change. In addition to their air-purifying functions, trees aid in mitigating the urban heat island (UHI) effect, which exacerbates air pollution levels. Trees cool down urban areas by providing shade and releasing moisture through transpiration, thereby reducing ground-level ozone formation (McDonald et al., 2016). These cooling benefits are significant as cities face warmer summers and more frequent and intense heat waves. Furthermore, the cooling effect of trees can result in lower energy usage in buildings, indirectly reducing greenhouse gas emissions. For instance, research conducted in Montreal demonstrated that planting more trees along streets could significantly reduce the UHI effect, leading to lower temperatures and improved thermal comfort (Wang & Akbari, 2016).

Urban forests also contribute significantly to climate change mitigation by sequestering carbon dioxide (CO2) from the atmosphere and acting as carbon sinks. Canadian urban forests already store significant amounts of carbon (Pasher et al., 2014; McGovern & Pasher, 2016; Steenberg et al., 2023). Moreover, urban forests, as a natural climate solution, have the potential to sequester and store more carbon if the existing trees are managed effectively and new trees are planted strategically (Drever et al., 2021). 

Carbon credit projects across Canada have promoted sustainable forest management, carbon sequestration, and biodiversity conservation. However, urban forest carbon credit programs are less prevalent in urban areas than in rural and boreal forest initiatives in Canada.  In urban forests, due to limited space for tree growth, soil compaction, and pollution, which impact tree longevity, tree mortality, and ongoing carbon maintenance, urban forest carbon sequestration and storage present unique challenges. Urban forests have a relatively small biomass for carbon sequestration compared to rural forests. Additionally, the diverse ownership of urban forests and the high cost of investments associated with certification further complicate the process of generating substantial carbon offset credits from urban trees. However, the importance of carbon sequestration has been recognized, and urban forest carbon programs offer an opportunity to enhance urban sustainability and contribute to climate change mitigation. The Sustainable Forestry Initiative's Urban and Community Forest Sustainability Standard and the Forest Stewardship Council (FSC) Certification standard can assist municipalities in developing frameworks that incorporate carbon storage into their urban forest management plans (SFI, 2024; FSC, n.d.). The City of Mississauga attained FSC® certification for its woodlands in 2024. In Canada, there are also localized, voluntary, and self-evaluated carbon offset programs for urban forests. These programs promote tree preservation and planting and carbon credits on a voluntary basis (University of Toronto, 2019).

Mitigation and Management Strategies

Maximizing these benefits requires effective urban forest management of the existing trees and strategic planning and implementation of tree planting. One critical component of planning future urban forests is appropriate tree species selection, as different species vary in their ability to contribute to air pollution removal and withstand changing climate conditions. Using climate analogues and vulnerability metrics to inform tree species selection ensures that urban forests remain resilient under future climate scenarios (Esperon-Rodriguez et al., 2022). Furthermore, integration of urban forest management into municipal climate policies can enhance the effectiveness of climate adaptation strategies. Aligning municipal climate change and urban forestry policies in Canadian cities can lead to more cohesive and robust adaptation frameworks that benefit both urban forest and climate change mitigation (Cheng et al., 2021).

Several Canadian municipalities have successfully implemented urban forestry initiatives to combat air quality issues and climate change. In Kingston, the impact of urban forests was critical in mitigating the UHI effect, improving thermal comfort, and reducing energy consumption for cooling (Guilbault, 2016). In Vancouver, local climate zones have been analyzed to optimize tree planting locations, ensuring that urban trees contribute effectively to maintaining outdoor thermal comfort (Aminipouri et al., 2019). This approach highlights the importance of local and site-specific strategies in urban forest planning. Moreover, the City of Surrey has developed a conversation guide to engage residents in urban heat readiness, emphasizing the role of urban trees in mitigating heatwaves and improving community resilience (City of Surrey, 2021).

Municipalities and industry professionals consider several vital recommendations to maximize the benefits of urban forests, including those related to air quality. Sustaining healthy large-stature trees and promoting a diverse mix of long-lived and low-maintenance tree species enhances resilience against pests, diseases, and thus climate change while providing a more comprehensive range of ecosystem services (Wood & Dupras, 2021). Moreover, identifying priority areas for tree planting, such as heat-prone neighbourhoods and high-traffic areas, can maximize air quality improvements and thermal comfort (Chan et al., 2007). Additionally, implementing more efficient tree care, such as watering during droughts, can support the health of trees and enhance their role in mitigating climate change effects. These efforts can be supported by involving local communities in urban forestry initiatives through education and participation programs; engaged residents are more likely to support and care for urban trees, which can supplement municipal tree care efforts and ensure urban forestry's long-term success and sustainability (Bourque et al., 2021).  

Finally, regular monitoring and maintenance programs are essential to ensure healthy and functional urban forests. Urban forests are indispensable assets for Canadian cities, offering significant benefits for improving air quality and mitigating climate change. By strategically managing and expanding urban tree cover, municipalities and industry professionals can enhance urban resilience, improve urban environments, and create more livable and resilient cities (Cheng et al., 2024).

Urbanization and intensive land development have significantly changed the permeability of urban landscapes and impacted their natural hydrological cycles and processes. Cities are becoming more vulnerable to heavy rainfall events that result in rapid runoff and flooding (Kaykhosravi et al., 2020). With fewer natural forests and less natural vegetation, any reduction in tree canopy cover results in increased runoff and urban areas becoming more prone to flooding. Urban forests, with adequate canopy cover, structure, and composition, have the potential to improve urban hydrology and reduce runoff (Berland et al., 2018; Kuehler, Hathaway & Tirpak, 2017; Xiao, McPherson, Simpson & Ustin, 1998).  However, to effectively manage urban forests for improving hydrology, many cities and towns globally lack appropriate areas for future tree planting. Canadian urban areas are no exception when it comes to these issues of urbanization, hydrology, and tree canopy. 

Trees, individually and collectively as urban forests, play a crucial role in stormwater management. Strategically conserved, managed, and enhanced urban forests can provide a sustainable solution for Canadian municipalities experiencing environmental challenges. Urban trees and their canopies manage stormwater through evapotranspiration and by physically intercepting rainfall via leaves, branches, and tree trunks, thus reducing the volume of water that reaches the ground (Carlyle-Moses et al., 2020; Dowtin et al., 2023). However, interception and evapotranspiration are determined by morphological characteristics of tree species, tree size and stature, leaf area density, branching structure, and whether trees are planted in groups or individually (Berland et al., 2018; Kuehler, Hathaway & Tirpak, 2017; Xiao, McPherson, Simpson & Ustin, 1998).

Additionally, tree roots stabilize the soil, improve soil structure and organic content, and increase the soil’s ability to absorb and filter water. This reduces the load on stormwater management infrastructure, streams, and ponds, and lessens flood risks while mitigating erosion and sedimentation in waterways (United States Environmental Protection Agency, 2023). Urban trees also improve overall water quality (The Mersey Forest, 2014) by reducing runoff and toxic chemicals like metals, fuels, solvents, and other pollutants (USEPA, 2013). Urban forests with hydrological functions help protect properties and gray urban infrastructure by reducing flooding and runoff during extreme weather events, which provides significant economic benefits (Nesbitt et al., 2017).

Many Canadian cities have created green development standards to incorporate trees and integrate urban forests into land use planning (see City of Toronto, 2023b; City of Mississauga, 2012; The Town of Halton Hills, 2019). By preserving and managing urban trees, municipalities reduce overall runoff from rainfall and increase soil absorption capacity, thus creating a more resilient urban environment, urban forest, and natural ecosystem (City of Mississauga, 2023; Ministry of Municipal Affairs, 2023).

Implementation Strategies

One of the most effective strategies for managing stormwater and reducing runoff is to increase both the coverage and quality of tree canopy. This can be accomplished by strategically planting trees in areas such as streets, parks, private properties, and various types of land use. To further enhance the advantages of urban forests, it is recommended to combine tree canopy conservation and planting with other forms of green infrastructure, such as rain gardens, green roofs, and permeable pavements. This integrated approach can significantly improve stormwater management and maximize the benefits provided by urban forests (Carlyle-Moses et al., 2020; USEPA, 2024).

More recently in Canada, various levels of government have been encouraging urban tree planting to increase canopy cover and improve urban environmental conditions, as well as to improve stormwater management (Green Infrastructure Ontario Coalition, 2016; City of Toronto, 2023a; City of Toronto, 2023b). To that effect, many Canadian municipalities have set goals or guidelines for stormwater management that utilize urban forests and increase tree canopy cover. For example, as per Toronto’s Green Standard Requirements, the City of Toronto aims to minimize runoff to at least 50 percent of its annual rainfall and, for some sites, retain at least 5 mm of rainfall (through rainwater reuse, on-site infiltration, and evapotranspiration) from each rainfall event (City of Toronto, 2017). Aside from the various ecosystem services urban forests provide, urban trees also enable the saving of resources for managing gray infrastructure. The City of Surrey, for example, saved $4.8 million/year on stormwater infrastructure due to the presence of trees (City of Surrey & Urban Systems, 2023). Some municipalities, such as the City of Mississauga and the City of Kitchener, have implemented stormwater fees to encourage private landowners to reduce the hard surface on their properties. The fees are based on a percentage of impervious surfaces to encourage property owners to use green infrastructure and permeable surfaces to reduce localized runoff (Environmental Commissioner of Ontario, 2016).

Urban forests provide numerous ecological and social functions that can be translated into economic value, financial benefits, and dollar value. Urban trees increase property values and reduce energy costs through natural cooling; also, treed and forested urban areas promote tourism and recreation, which can all be transformed into monetary value (Ewane et al., 2023; Nowak et al., 2017; Wolf et al., 2020). The economic value of trees can be assessed in several ways depending on the geography, purpose of the evaluation, and who is performing the evaluation. For example, trees can be valued for their intrinsic value (e.g., diversity, complexity, beauty, spiritual significance) or the objective value of the tree in and of itself (AWES, 2021). Alternatively, urban trees can be evaluated in situ, built on the monetary value they provide based on their ecological services (e.g., stormwater management, carbon sequestration), or appraised for the cost of replacing them based on their size, health, and species. 

Tree Appraisal

In addition to measuring, assessing, and quantifying urban forest benefits and ecological services, tree appraisal is conducted for numerous compelling reasons, including official and legal valuations of urban trees. Several appraisal methods have been developed and implemented to estimate the monetary value of trees (Watson, 2002). While tree appraisal results can vary between appraisal methods and appraisers (Watson, 2002), conducting tree appraisals remains an important way to convey the significance and value of urban trees (Komen & Hodel, 2015; Purcell, n.d.).

Several methods can be used for estimating tree replacement values, particularly when estimating the value of a tree for legal disputes, sales, urban planning, and infrastructure development needs, or insurance claims. Several tree appraisal methods are used across urban areas, and all of them assess the monetary value of trees based on several common variables: species characteristics, tree size, health condition, location, and contribution to the surrounding environment (Doick et al., 2018). For example, these methods are: the Trunk Formula Method (TFM), often used for large and irreplaceable trees; the replacement cost method, used for smaller and replaceable trees; the cost approach, used to evaluate lifetime maintenance and planting costs for trees; the market approach (comparable sales), to assess the value of a tree based on market prices of similar trees; the income approach, which focuses on economic benefits of trees such for example energy savings; the capital asset valuation which estimates a value that a tree contributes to property value; ecosystem service valuation which assigns tree value based on the environmental benefits it provides such example carbon sequestration and air quality improvement; and the CTLA Guide for Plant Appraisal, an ISA approach that combines multiple tree variables such as size, species, and condition into the valuation (Watson, 2002; Szaller et al., 2019; Doick et al., 2018). 

A tree appraisal's purpose is usually guided by specific clients' needs and often considers handling unexpected losses, tort claims (civil claims for compensation for wrongful acts or injury), insurance claims, tax deductions, real estate assessments, or proactive planning. Once all relevant tree information is collected, the appraiser selects an appropriate appraisal method and delivers an objective valuation as a dollar figure (Purcell, n.d.; Ponce-Donoso, Vallejos-Barra & Escobedo, 2017; CTLA, 2020; Grande-Ortiz, Ayuga-Téllez & Contato-Carol, 2012).

The Council of Tree and Landscape Appraisers (CTLA) Guide for Plant Appraisal is one of the most commonly used tree valuation methods in Canada and the United States, and is considered an industry standard (Cullen, 2007; Komen and Hodel, 2015). The appraisal process requires collecting site-level information, including tree measurements and assessment, to obtain all measurable variables effectively. Tree species characteristics and size, tree condition, damage, scarring, location factors, and many more criteria determine the value of a tree. Valuing trees and landscape elements requires specialized training, expertise, and experience. Tree appraisal material and courses are available through organizations such as the International Society of Arboriculture (ISA) and ISA Ontario. CTLA methods, endorsed by the ISA and local arborist organizations, are applicable for tree valuation in legal disputes, urban planning, environmental impact studies, and insurance claims. For example, the City of Ottawa, Edmonton, Guelph, and Mississauga use the CTLA approach to assess and evaluate the value of trees affected by construction and development projects (City of Guelph, 2019; City of Edmonton, 2024; AECOM, 2022).  Smaller municipalities may lack the resources needed for complete tree inventories; collaborating with consultants or universities can provide valuable support at the city level.

Economic Value of Urban Forests – Benefits Provided

Urban trees provide a myriad of ecological services that can be translated into economic value. For example, tree benefits include increased property values (Han et al., 2024), positive impacts on real estate consumer preference (Farr, 2017), reduction in energy costs by shading buildings and pavement, and lower ambient temperatures (McDonald et al., 2024). In 2014, a TD Economics Report found that urban forests in Halifax, Montreal, Vancouver, and Toronto had a combined value of $42 billion and provided $330 million per year in environmental benefits. Depending on the city, for each dollar spent on tree maintenance, about $1.88 to $12.70 was returned in various benefits (Alexander & DePratto, 2014). These values are likely to be lower estimates, as they do not include the value of tourism, recreation, or impact on property values, human health, and social wellbeing (Farr, 2017). Urban trees provide services akin to other urban infrastructure by reducing runoff and erosion, improving air quality, saving energy, and sequestering carbon, which increases over time as trees grow (Hotte et al., 2015; Farr, 2017). 

Technology such as remote sensing (e.g., multispectral images and LIDAR) and geographic information systems (e.g., GIS and Google Maps), combined with ground-based sampling methods (e.g., plot and tree sampling, as well as data collected through citizen science), play a vital role in estimating the extent, structure, and composition of urban forests and their benefits (Hotte et al., 2015). These technologies facilitate the mapping of urban canopy extent and the collection of measurements of urban forests and woodlots in both large and small municipalities. This spatial and field information is then further used to support the ecological and economic values of trees and the services they provide. 

For instance, field measurements, along with tools like i-Tree or other tree-relevant allometric formulas, can be employed to determine the carbon sequestration rates of urban forests. By utilizing field data alongside mapped tree canopy coverage, it becomes possible to estimate the amount of carbon dioxide sequestered from the atmosphere by the entire urban tree canopy, by individual trees, and by a unit (e.g., 1 ha) of the urban tree canopy. For example, a study conducted in Canada by Pasher et al. (2014) estimated that the average carbon sequestration capacity of urban tree canopies is 2.9 tonnes of CO₂ per hectare per year.

Benefits and Value of Urban Forests – Beyond Money

Estimating the value of an urban forest can be done by appraising forest structural components such as canopy cover, species composition, and age. The many benefits of urban forests, such as carbon storage, carbon sequestration, air quality improvement, and the moderation of urban heat island effects (Han et al., 2024), also create value via co-benefits. It has been shown that some of these benefits result in co-benefits, such as decreased power usage during a heatwave (McDonald et al., 2024), and a negative correlation between urban tree canopy cover and mortality and morbidity rates during heat waves (McDonald et al., 2020). Aside from providing refuge during summer, proximity to urban forests is positively correlated with shorter hospital stays for patients recovering from surgeries and better health outcomes for pregnancies (Ulrich, 1984; Hotte et al., 2015). While more challenging to quantify, the cultural, spiritual, visual, and sensory values of urban trees are often the aspects most highly valued by the general public.

The structure, distribution, and composition of an urban tree canopy greatly impact the benefits and services provided by urban green spaces in Canadian cities (Przewoźna et al., 2022). The foundation of an effective urban forest management program and the base information supporting ecological service estimates comes from a detailed tree inventory.  A tree inventory is a necessary urban forest management tool that provides information about trees, such as tree species, health, size, and location. There are diverse ways in which city authorities, professionals, and researchers can use tree inventory data. Inventory data can be used to identify and analyze tree species diversity and distribution, percentage of canopy cover, tree size/class distribution, functional group distribution, tree health and growth trends, and more (Nielsen, Delshammer & Ostberg, 2014). Tree inventory data can also be used to support various efforts such as strategic forest management plans, cost-benefit assessments of urban climate/pollution mitigation, creation of invasive species management plans, risk assessment, examination of social dimensions of urban forests, and much more (City of Toronto, 2013). Forest managers can also prioritize maintenance efforts and resources by knowing urban forest resources. As such, keeping an up-to-date inventory of urban trees, supplemented by routine tree inspection, is fundamental for effective urban forest management.  

Sample-Based Inventory

There are several different methods and scopes of tree inventory that a city can employ. The quickest and most minimal scope of inventory is a sample-based inventory, which contains information on a small subset of trees from a larger population. A sample with sufficient data enables urban foresters to extrapolate tree data across the city to represent an entire urban forest. This type of inventory is considered a cost-effective way to achieve a statistically valid representation of an urban forest when the scope of inventory and analysis does not require data on each tree for specific management applications (Sabatini, 2021). Similarly, partial tree inventories focus on certain areas of concern, such as specific tree species, land use categories, or geographic areas. This type of inventory is taken when dealing with a pest outbreak and species-specific pests and diseases, as with the Emerald Ash Borer. A partial inventory is also useful when assessing storm damage and when performing risk assessments (EFUF, 2018).

Individual Tree Inventory

When a more comprehensive analysis of urban trees is required to support tree management and daily maintenance, tree surveys/inventories at the level of individual trees may be conducted. Survey methods include direct inspection and measurement of individual trees to gather a complete record of species, age, size, health, location, and other qualities (Nielsen, Delshammer & Ostber, 2014; Morales-Gallegos et al., 2023). While this approach can be labour-intensive and time-consuming, it supports urban forest management and operations with the most thorough and accurate tree data. Individual tree inventories may be considered the most beneficial inventory method in situations when analyzing tree species diversity and distribution, tree size/class distribution, and monetary evaluation of individual trees/species are required, such as for preparing tree planting prescriptions or creating a baseline inventory for further assessment (Urban Forest Analytics, 2024). 

Tree Inspection

A tree inspection cycle, coupled with an updated tree inventory, is integral for proper tree maintenance and hazard management. Effective tree monitoring enables the evaluation of urban forest resources and the development of short and long-term plans and maintenance, which can provide substantial cost savings while also mitigating safety and tree hazard issues.  

Urban tree inspection, pruning, and removal are necessary components of urban forestry in Canada [see chapter: Tree Maintenance]. Up-to-date inspection of urban street tree condition and health, as well as recording previous and scheduled work, are the basis of effective street tree maintenance and management (City of Toronto, 2013). Regular inspection cycles are also important health and safety tools, where storm or construction tree damage, canopy dieback, limb damage, pest and disease presence, routine tree care and tree health decline can be assessed and managed in a timely manner to prevent hazards and risks to citizens (International Society of Arboriculture, n.d.). 

Tree health indicators at the individual tree level such as trunk damage, crown dieback, vandalism, pest/disease presence and root damage require on-the-ground inspection (Morales-Gallegos et al., 2023), while street- or stand-level health indicators such as crown density, stand age/size, vegetation indices, edaphic (soil-related) factors and climatic/environmental stressors can be inspected and observed using satellite imagery, sample inventories, proxy indicators and models (Haq et al., 2023). 

Aerial Urban Forest Inventory

Conversely, when general tree data is required for large areas, many Canadian cities create tree inventories using aerial photography and GIS (Esri Canada & City of Guelph, n.d.). By employing satellite imagery and scanning tools, cities can conduct an inventory of tree cover types and general stand qualities without inspecting each individual tree [see chapter: GIS, Remote Sensing and Other Spatial Technologies]. This type of inventory can be beneficial when considering the health and benefits of urban canopy cover, when assessing large areas where field surveys may be too costly/time-intensive, and when information about individual trees is not necessary based on the scope of data application (Wood, Norton & Rowland, n.d.; Nielsen, Delshammer & Ostber, 2014).

Community Science and Participation

When conducting tree inventories, Canadian cities may employ citizens and non-profit organizations to participate in data collection. Recruiting volunteers to record general observations about tree health in their neighbourhoods, such as cavity decay, crown dieback, and trunk damage, is a valuable and cost-effective way to build and maintain tree health inventories without performing constant field surveys (Sabatini, 2021). In Canada, community-based stewardship programs such as Neighbourwoods™ (Kenney & Puric-Mladenovic, 1995) can help community groups and volunteers contribute to tree inventories, which help inform foresters and planners about the state of urban forests while also encouraging community involvement in urban forest stewardship. This program has explicitly been employed in several municipalities across Ontario and has potential for application across Canada and beyond. Additionally, Canadian urban tree inventory data can be added to national and international databases (e.g., CIF Open Urban Forests (2024), i-Tree (n.d.), Making Nature's City ToolKit (n.d.), etc.), which support concerted management and planning efforts. 

It is important to recognize that many community involvement and volunteer-based outreach programs only reach a very targeted audience. There is often a lack of emphasis on place-based landscape design and engagement, which should vary based on the needs of individual neighbourhoods, communities, and municipalities (Eisenman et al., 2024). A place-based approach to community engagement in urban forestry requires understanding the issues, relationships, and needs of community members in any given place and specifically coordinating planning and resources to improve the quality of life for that community (Improvement Service UK, 2016). When place-based needs and goals are not well understood, the benefits of community involvement in urban forestry can be inequitably distributed (Kudryavtsev, Stedman & Krasny, 2012).  

For a successful and equitable place-based outreach program, it is necessary to allocate funds properly, meaningfully consult with target volunteers, co-develop participation opportunities with community members, and select performance outcomes based on place-based needs and goals (Eisenman et al., 2024). People from all communities should be equally able to engage in urban forestry, so public participation programs should reflect their specific needs and goals [see chapter: Equity Considerations in Urban Forestry].

Natural Area/Woodlot Inventory

Contents

• Urban woodlots and natural areas 
• Management goals: Determine the type of inventory that should be used.
• Inventory methods: Selecting inventory methods, scale, and sampling plan.
• Monitoring woodlots and natural areas: Ongoing process of tracking changes in forest communities over time and space.

Effective woodlot, natural parks, and area management rely on accurate knowledge of plant species composition, community structure, and how healthy its components are. Woodlot inventories differ from street tree inventories both in their spatial extent and in that a woodlot will have trees grown from naturally occurring seed, understory plants, wildlife, and other components not controlled by humans. Woodlot inventories can range from a basic timber cruise to a detailed inventory including soil, vegetation community, and wildlife inventory. The management goals for the woodlot generally determine the type of inventory chosen for a project. However, it is important to keep in mind that an inventory may bring to light new information (such as the presence of a species at risk or invasive plants) that might change management goals (Ma et al., 2021).

The first step in understanding what is in a woodlot is a survey of available aerial images and maps. Depending on when and why they were developed, existing maps may already delineate the different stand types, roads, and water bodies in a woodlot. Aerial imagery can be used to create these maps and to judge the accuracy of outdated or broad-scale maps when newer information is not available (Gougeon, 2014). Forest resource inventory maps are variably available across Canada and may be found through provincial open spatial data hubs [see chapter: National and Provincial Datasets]. LiDAR mapping may also be an option for stand delineation (Wang et al., 2004). 

After getting a basic idea of what stands and other features are present in a woodlot, a sampling plan can be developed to build a basic inventory. The simplest form of woodlot inventory sampling is a timber cruise. In this form of inventory, sample locations (plots of variable size) are selected where surveyors record tree species, diameter, and growth form, which are then used to estimate the number of each tree species and the amount of basal area and merchantable timber per hectare. There are many guides to timber cruising provided by provincial governments and woodlot associations. However, this kind of inventory does not provide sufficient information on forest structure, composition, plant diversity, non-tree plant species, soil condition, forest community, and other aspects of woodlots, which determine their ecological integrity, combined health, and classification. A more detailed inventory, often based on fixed area plots and which collects data on species besides trees as well as site characteristics, can better support tailored management for multiple purposes such as monitoring, habitat and species-at-risk protection, regeneration success, recreation, or carbon stock (Day and Puric-Mladenovic, 2012). One such inventory and monitoring program is the Vegetation Sampling Protocol (VSP) (Puric-Mladenovic, 2016), which can be adjusted to different spatial scales depending on landscape and management needs (Puric-Mladenovic & Baird, 2017). VSP is a sampling protocol that collects multipurpose, detailed information on trees and their size, but also a full species list, dead wood, and invasive species abundance (Sherman, 2015). VSP, as a strategic inventory, gathers information that is multi-functional and standardized (data collection and web-based portal for data entry), and gives a precise record of spatial extent and location, enabling field data to be transferred into diverse spatial formats and vegetation mapping products. It is also used for monitoring as it enables resampling and tracking changes in forest ecosystems over time and space. Detailed protocols such as this can be great resources when creating detailed inventories and flexible woodlot management plans.

Technologies like Geographic Information Systems (GIS), remote sensing, other web-based spatial technologies, and relevant software are widely used to support urban forest management, conservation, and planning. They allow the mapping, cataloguing, inventory, and monitoring of urban forest characteristics from the scale of individual trees, woodlots, and urban green spaces to an entire urban tree canopy (Ward & Johnson, 2007). Besides mapping trees, they also allow mapping of the urban environment and environmental conditions where urban trees grow. There is a diversity of GIS and remote sensing technologies in use and development, and a diversity of spatial and remotely sensed urban forest-related data. Some of the technologies have been designed for use in urban forestry, and some have been developed in other professions and adopted by the urban forestry sector (Green Municipal Fund, n.d.). This chapter briefly summarizes technologies used in urban forestry and provides a list of Canada's relevant examples.

Geographic Information Systems (GIS) 

Geographic Information Systems (GIS) have played a pivotal role in natural resources management, and thus urban forestry, for decades. Since the 1980s, particularly in 1990, with spatial technology and software development and growth, GIS has become a critical tool for urban forest management and decision-making. For example, GIS enables detailed tree and canopy mapping, analysis, and management of tree population data. GIS creates spatial tree inventories containing species, health, size, and more information. Such spatial tree data facilitates more effective and adaptive urban forest management and monitoring, critical for informing tree planting strategies and sustainable and evidence-based urban development. 

Additionally, GIS, combined with remote sensing, enables sampling of the entire urban area, supports timely urban forest monitoring, and detects urban forest decline and pest infestations, to name a few applications. Furthermore, by integrating urban forest spatial data with urban planning, GIS supports future urban forest planning and enhances urban forest conservation in the face of increased urban intensification and development. Moreover, GIS facilitates using other spatial data (e.g. Digital Elevation Models, infrastructure mapping, and soil zones) to provide context about a proposed planting site, potentially protect trees and green areas, and other urban forestry projects (Kip, 2022).

Numerous commercial and open-source GIS software exist and are utilized in urban forestry.  Commercial GIS programs like ESRI ArcGIS Pro are widely used across municipalities, governments, and larger NGOs. MapInfo Professional is another commercial software that has mapping and spatial analysis tools suitable for urban forest management and land use planning. In the open-source category, QGIS is certainly one of the most popular GIS platforms. It has a wide range of tools for mapping, geospatial analysis, and data visualization. GRASS GIS is an advanced open-source GIS, particularly for use with remotely sensed images. It has powerful analytical capabilities.  Each of these tools enables spatial database creation, data maintenance, mapmaking, analysis, and reporting. For example, they can be used to create and maintain databases of individual street trees, facilitate tree health risk and assessment, track tree removal and work planning, analyze and map woodland and urban forest characteristics, and more. 

Municipalities, provincial governments, and some larger NGOs typically use Esri software to manage their data, conduct analyses, and share the information with the public. By taking advantage of web mapping, Canadian municipalities share street tree inventories with the public. For example, Vancouver, Ottawa, Charlottetown, Oakville, Winnipeg, and Montreal have their tree inventory data online. GIS in combination with web mapping also supports specific interactive web applications and other forms of knowledge sharing, reporting, and science communication that allow the public and other interest groups to view and understand forestry data easily. Examples of interactive web applications include Nature Canada's 2022 report on tree equity and the associated Canadian Map of Adaptation Actions, the City of Toronto’s Tree Equity Map, and Calgary's urban forest management map.

Mobile and web-based GIS tools and applications are also used to collect urban forest information and engage the public in data gathering and urban forest monitoring. These platforms enable citizens, researchers, and the broader public to contribute to the inventory, monitoring, and management of urban forests and their biodiversity. For example, iNaturalist has been used to track urban biodiversity and upload photos and locations of observed plants, wildlife, and insects. The Neighbourwoods© program has been using mobile GIS applications to support inventory and monitoring trees on private urban lands by engaging community groups and graduate students in data collection. 

Remote Sensing

Collecting data and sampling the entire urban forest through field surveys alone would be challenging and not economically feasible. Remote sensing is a method of collecting spatial data across entire study areas without direct contact with the observed objects, and it plays a crucial role in urban mapping, management, conservation, and planning. Remote sensing provides critical insight into urban forest extent, structure, composition, and dynamics by capturing broad-scale, consistent, and repeatable data. Remote sensing products include multiple spectral imagery of forestry, such as remote sensing, airborne sensing, drone imagery and LiDAR (Staley, 2022). The advantage of remote sensing is that it frequently enables sampling of the entire urban forest and provides high-resolution data with diverse derivatives and multiple applications. For example, high-resolution satellite imagery and LiDAR allow for precise urban tree canopy cover mapping across entire cities.

Remote sensing technologies with hyperspectral and multispectral sensors help identify vegetation stress and even specific tree species. Remotely sensed images and their derivative tools also enable consistent monitoring that can help to detect the effects of environmental and climate changes, phenology change, and green space loss, and can even be used to evaluate the effectiveness of urban forestry programs (e.g., tree planting efforts). Through remote sensing technologies, urban foresters can evaluate health, distribution, and changes in vegetation, as well as the impacts of urbanization. Besides providing information about urban forests and trees, satellite and airborne remote sensing platforms also enable monitoring of environmental factors such as temperature, urban heat island effects, pollution, and soil moisture. 

Remotely Sensed Images Used in Urban Forestry

Satellite-based remote sensing collects and analyzes data about Earth's surface and atmosphere using satellite sensors. It enables large-scale, consistent, and repeatable monitoring of various environmental and urban features (Wulder et al., 2024; Latifovic et al., 2015). Images from satellite-based remote sensing are free or commercial. Both free and commercial imagery play complementary roles, with free data offering broader accessibility and commercial data providing greater detail and precision for specialized applications.

Free satellite imageries are openly accessible for public use and are widely used for research, education, and non-commercial purposes. While these datasets are free, they may have limitations in terms of spatial resolution. For example, Landsat Data has multispectral imagery with 30m resolution (15m panchromatic) and a temporal resolution of 16 days. Sentinel-2 (ESA) imagery is high-resolution imagery (10-60m resolution) with multispectral bands. Like Landsat, it is suitable for urban forestry and land cover classification, and tree canopy analysis. MODIS (NASA) is imagery taken daily and has moderate-resolution imagery (250m-1km) applicable for broad-scale monitoring of vegetation, land cover, and global change, with limited application to urban forests. 

Commercial imagery provides finer spatial, temporal, and spectral resolution specialized data products, but they can be cost-prohibitive, especially for large-scale or long-term projects. There are many commercial satellite imageries based on purchase or subscription, like PlanetScope (Planet) high-resolution imagery, which is taken daily. Older imagery has a resolution of 5m, while images taken by newer satellites have a resolution of around 3m. These images do not have a panchromatic band. They have 4 multispectral bands (Blue, Green, Red, and Near-Infrared). GeoEye-1 has one panchromatic band with a resolution of 41cm and four multispectral bands (Blue, Green, Red, and Near-Infrared) at a resolution of 1.65m. WorldView Series (Maxar) is high-resolution imagery up to 30cm and provides multispectral and high-resolution panchromatic images. The multispectral WorldView satellite images provide data in multiple spectral bands, which are useful for urban forestry. WorldView-2 imagery has 8 multispectral bands (coastal, blue, green, yellow, red, red edge, NIR1, NIR2) with a spatial resolution of 1.84m. Its panchromatic band has a resolution of 0.46m. WorldView-3 images (and WorldView-4 decommissioned in 2019) have 1.24m resolution for 8 standard multispectral bands, 8 shortwave infrared (SWIR) bands, and 0.31m resolution for a panchromatic band.

Airborne remote sensing is used to capture high-resolution data about urban forests. Airborne remote sensing requires aircraft or drones equipped with multispectral, hyperspectral, or LiDAR sensors. Similar to airborne remote sensing, UAVs (Unmanned Aerial Vehicles or Drones) are equipped with multispectral cameras and LiDAR or sensors. This makes airborne and UAV remote sensing especially valuable for monitoring and mapping urban forests and green spaces, detecting changes in forest cover, and using their outputs to support urban forest management and plan for sustainable urban development. 

LiDAR (Light Detection and Ranging) uses lasers to generate point clouds representing the real world as the lasers encounter obstacles such as buildings, tree branches, and vegetation cover. These point clouds can then be classified by what they represent in order to generate models of the real world used in these analyses. These datasets are becoming more available to the general public as their use increases (Natural Resources Canada, 2023). LiDAR provides detailed 3D topography and 3D models of tree heights and canopy density. Once processed for practical uses, this data offers detailed spatial information for specific uses, such as canopy height models to support tree inventory risk assessment and forest structure assessment. LiDAR analysis of an area can be used to estimate the leaf area and crown density of individual trees or entire regions, creating more accurate canopy cover estimates as technology evolves (LidarBC, n.d.). LiDAR is also commonly used as a tool for forest inventory (Natural Resources Canada, 2024; Ontario Woodlot Association, n.d.), and there has been an exploration of LIDAR as a tool for fire risk classification (Burns, 2012) and natural disaster impact assessment (Blackman & Yuan, 2020). 

Red, Green, and Blue (RGB) are basic spectral bands used to visually view, assess, and map vegetation in urban areas. Near-infrared (NIR) bands are sensitive to vegetation health and can be used to distinguish tree canopy from other land uses. For example, shortwave infrared (SWIR) is useful in detecting moisture content in vegetation and providing insights into tree health and stress. Depending on the available spectral bands and imagery used, a combination of spectral bands is possible to derive various vegetation indices that provide information about the urban canopy. For example, the Normalized Difference Vegetation Index (NDVI), widely used to assess vegetation density and health, is derived from NIR and red bands. Enhanced Vegetation Index (EVI, as a variation of NDVI) might be more sensitive to mapping dense vegetation. The availability of near-infrared (NIR) and red-edge bands is particularly valuable for vegetation analysis, canopy mapping, and detecting tree health in urban forestry applications. For example, Leaf Area Index (LAI) can be estimated from NIR and field survey LAI to create urban forest LAI across a wider area (Ren et al., 2018; Le Saint et al., 2024) using Lidar data (Alonzo et al., 2015). 

In addition, various airborne or satellite hyperspectral images can be used to map tree canopy health, detect vegetation stress, or classify vegetation. They can even identify species and leaf biochemical properties such as chlorophyll content, leaf area index (LAI), or water content. For example, AVIRIS is an airborne sensor with 224 spectral bands. HyMap has 126 spectral bands, and  SpecTIR offers hyperspectral data across hundreds of bands. The EO-1 satellite, Hyperion, has 220 spectral bands, while PRISMA, from the Italian Space Agency, delivers 239 bands that can be used to support and inform environmental monitoring and urban forestry management. While hyperspectral imagery has high spectral resolution and is complex, it creates a large volume of data, requiring specialized remote sensing software to manage data and extract meaningful urban forest information. 

Aerial Orthoimagery

Digital Orthophotography (Orthoimagery) is aerial or satellite imagery, typically RGB and geometrically corrected (orthorectified) to remove distortions caused by terrain, camera angles, and lens distortion. It is commonly used to visually represent landscapes and as a base map in GIS. The advantage of orthoimages is that they are publicly available and shared by provinces or municipalities, and they can have a pixel resolution of 16cm and an accuracy of 45cm, which allows for precise identification of tree locations within urban environments and makes them suitable for mapping tree locations.

These imagery-based maps are widely used in GIS applications. As high-resolution imagery, they are overlaid with vector or raster data to provide quick spatial context and verify spatial data accuracy. Imagery-based maps are image layers that display satellite or aerial photographs of the Earth's surface. For example, Esri has included a high-quality aerial imagery-based map that is part of Esri's Living Atlas of the World. Unlike Esri products, QGIS does not have a native-based map, but with adequate plugins, it can use Google Maps, Bing Maps, and other services as base maps. For example, though time-consuming for larger areas, digital orthophotography and base maps can be used to digitize tree canopy outlines for smaller areas (e.g. parcel).

Federal, provincial, municipal governments, academic institutions, and non-government organizations produce, maintain, and distribute several urban forest and urban environment-related datasets covering all or part of Canada. Many of these available datasets are helpful for urban forestry practitioners as they are standardized and have long-term update plans, ensuring their availability in the future. Most of these datasets are available online, publicly accessible, or available through data-sharing agreements. National and provincial data are listed below, as well as some individual national datasets made available by non-governmental organizations. Federal and provincial datasets generally contain remote sensing and spatial data, geological and soil data, census data, and other large-scale data types. 

Municipal datasets often include local landcover data, orthoimagery, and city-level spatial data. Many municipalities and cities across Canada develop and maintain open data portals specific to their geographic area. Some of these are: In Alberta, Edmonton, Calgary, Medicine Hat, Red Deer, and Grande Prairie. In British Columbia, the open data includes Vancouver, Kamloops, Langley, Nanaimo, North Vancouver, Prince George, Surrey, and the Regional District of North Okanagan. For Manitoba, there is open data for Winnipeg. In New Brunswick, for Fredericton. Ontario's open data municipalities include London, Ottawa, Toronto, Windsor, Niagara Falls, Mississauga, Burlington, York Region, Peel Region, Niagara Region, Guelph, Hamilton, City of Waterloo, and Waterloo Region. In Quebec, the cities are Montreal, Ville de Québec/Quebec City, and Sherbrooke. In Saskatchewan, open data is available for Regina and Saskatoon, New Brunswick for Fredericton, and Prince Edward Island for Charlottetown. 

For further information about any other municipality, visit the municipal site to determine if an open data portal is maintained by the appropriate governing authority.

Diverse urban forest management and tree maintenance practices play a vital role in keeping urban forests healthy, managing tree hazards, planting trees, and/or generally sustaining tree canopy in urban areas. However, these practices have often targeted public trees, focusing on street trees or specific management practices (e.g., pruning). Urban tree maintenance and management have often been implemented as reactive responses to natural disasters or invasive species impact rather than as proactive approaches. While the importance of urban forests was recognized in the 1960s, it took over 50 years to understand how this valuable natural resource should be managed in its entirety and more strategically. 

Strategic urban forest management in Canada emerged in the early 2000s, based on the idea that the entire urban forest and all its components need to be strategically managed through a carefully planned process (Kenney, 2003; Kenney et al., 2011). Such strategic and effective urban forest management ensures that the diverse benefits urban forests provide are maximized and sustained over time. As critical components of green infrastructure and urban land uses, urban forests and green spaces require careful planning and management that is adaptive and sustainable. Taking a proactive approach to urban forest management ensures that urban forests are not left unmanaged. It also ensures that an urban forest management plan addresses foreseen pressures and challenges such as urban development, genetic diversity of tree species, and tree age distribution. Additionally, it incorporates measures for unforeseen challenges that could occur due to pest outbreaks, invasive species impacts, or climate change. 

The leading objectives of urban forest management are to optimize the tree canopy leaf area by planting and maintaining a genetically diverse and site-appropriate mix of trees and shrubs, which should be achieved cost-effectively while maximizing public benefits and minimizing risks to public safety. Urban forest management planning begins by assessing the existing state of urban forests using the most recent data. If tree inventories are not available, new management plans should include a tree inventory that surveys tree species, size, overall health, and value. Urban forest inventories are prerequisite for measuring urban forest benefits and developing comprehensive urban forest management plans, and also serve as a base for developing natural asset management plans (GIOC, 2016). While natural asset management ideas related to natural areas emerged in 2017, the concept has also been applied to urban forests overall. Recently, Urban Forest Certification standards were developed to address the growing need for sustainable management of urban forests (SFI, 2024). All these approaches contribute to urban forest management and share many common objectives and components, namely tree inventories. 

Strategic Urban Forest Management Planning in Canadian Cities 

Urban forests and all their elements have been recognized as the backbone of green infrastructure in Canada, and as critical for connecting urban and rural green areas (GIOC, 2015; NRCan, Canadian Forest Service, 2022). Strategic management planning emphasizes the importance of managing all urban forest components and their associated biotic and abiotic elements across a wide range of land uses and areas, from large to small communities, as well as the areas between them. Moreover, the entire urban forest, including trees across a range of urban spaces such as streets, parks, cemeteries, arboretums, private properties, and natural forest fragments, is recognized by strategic management planning. 

The importance of strategic urban forest management planning was introduced to Canada by Kenney et al (2011), but the first Urban Forest Master Plan was developed for Prince George in 2003 as a response to the impact of fire that devastated the area. Following the principles of strategic urban forest management planning, urban forest strategic management plans were developed by many municipalities, such as the Town of Oakville (2008), the City of Guelph (2008), Town of Ajax (2011), and Halifax and the City of Toronto (2013), to name a few. While the development of urban forest plans in Canada peaked from 2010-14 within more urbanized mixed-forest regions (Ordóñez Barona, 2024; Puric-Mladenovic & Bardekjian, 2023b), new urban forest plans are still developing, while the early plans are being updated or prepared for renewal.

Urban forest management plans or strategies that provide a long-term, strategic approach to protect, preserve, and enhance the municipal urban forest are typically approved by city councils. Canadian municipalities are among the global leaders in terms of urban forest management planning, with over 80 urban municipalities having urban forest management plans.  For example, based on the 2023 study (Puric-Mladenovic and Bardekjian, 2023b), 89 out of 800 (11%) of the examined municipalities had an urban forest management strategy and/or urban forest management plan. Since that time, there has been an increase to 118 (14.7%) municipalities with urban forest management plans or strategies. For example, Saskatoon recently released its Urban Forest Management Plan 2022-2031, which emphasizes the importance of urban forest sustainability (City of Saskatoon, 2022); the City of Saanich (2024) followed close behind with a 10-year urban forest strategy published in 2024.

These urban forest management plans, though all aimed at maintaining and maximizing urban forest canopy and tree benefits, differ based on how they approach implementation, tree maintenance, increasing canopy coverage, diversifying species, or involving the community (Kenney et al., 2011; Ordóñez & Duinker, 2013). Urban forest management plans are also crucial for maximizing ecological services and resilience by guiding the long-term management of a healthy, biodiverse, resilient urban forest.

Not all of these plans are created equally; some are detailed plans with set goals and timelines, while some are more like strategies than plans. For example, the context of some plans is more like an outline of the importance of urban forests rather than a management plan. However, they are still valuable for setting the stage for developing a Strategic Urban Forest Management Plan (SUFMP), which is a long-term plan (typically 20 or 25 years) with a detailed roadmap of how to achieve the set long-term vision and goals. SUFMPs are based on measurable objectives that allow plans to move strategically from a baseline condition to a desired set target while prioritizing implementation and monitoring the implementation and success of the plan. These plans are based on understanding the existing state of the urban forest and then setting measurable objectives, criteria, and indicators, which are all crucial to developing an actionable management plan. Strategic urban forest management planning objectives, depending on the region, type of urban area, and state of the urban forest, can include increasing tree canopy cover, enhancing the longevity and health of urban forests, diversifying species, or fostering engagement from the community. Other common goals in SUFMP for urban forests across Canada include expanding species diversity, improving tree health, managing invasive species, increasing resilience against climate change and natural disasters, and improving canopy cover equity.  

SUFMP objectives are achieved through detailed operational plans, which might include reaching specific canopy cover percentage targets, plans for invasive species removal, followed by native species plantings, community stewardship initiatives, or hazard tree removals, to name a few (Kenney et al., 2011; Ordóñez & Duinker, 2013). For example, the urban forest plan for the City of Calgary aims to raise canopy cover to 16% by 2060, protect current forests, and engage the community in forestry projects (City of Calgary, n.d.), while the plan for the City of Toronto aims to achieve 40% canopy cover by 2050 (City of Toronto, 2023). Strategic goals in SUFMP are aimed to be achieved through specific operational plans that are typically at 4-5 year intervals. Furthermore, 4-5 year operational plans are implemented through Annual Operating Plans (AOPs). AOPs involve day-to-day decisions on things like planting, pruning, and felling trees, controlling pests and diseases, and ensuring optimal water and soil conditions. Annual operational planning also involves developing a budget, delegating roles and responsibilities, and establishing metrics to monitor progress. As an illustration, a strategic urban forest plan for the City of Calgary involves operational initiatives of caring for existing trees, planting 3,500 new trees each year, and prioritizing public safety and legal safeguards to protect new and existing trees through bylaws (City of Calgary, n.d.). 

Natural Asset Management  

Natural Asset Management (NAM) is an emerging approach to urban forestry in Canada where natural features are viewed as any other municipal asset or gray infrastructure that provides essential services. In this context, urban forests, as a natural asset, are placed into formal municipal asset management frameworks and plans. Several Canadian municipalities have implemented NAM strategies to enhance urban forest management; the Town of Gibsons, BC, was the first to implement NAM and recognize aquifers, forests, and wetlands as green infrastructures that need management. A monetary value was assigned to these natural systems, which enabled them to be incorporated into the town’s asset management plans and ensure their management and sustainable use (Town of Gibsons, 2018). Another example is the City of Edmonton, which developed an Urban Forest Asset Management Plan that focuses on the characteristics and conditions of publicly managed urban forest assets (City of Edmonton, 2021). It also provides a framework for achieving desired service levels at optimal life cycle costs. The City of Saskatoon also recently completed an inventory of its natural assets (wetlands, a portion of the South Saskatchewan River, grasslands, forest/shrublands) and completed their evaluation to support their own NAM (City of Saskatoon, 2020).  

Urban Forest Certification

Forest sustainability and good management certifications have existed in Canada for managed forests and woodlots since 2005 (PEFC, 2024), but recently the Sustainable Forestry Initiative (SFI) certifying body has developed certification standards for environmental, social, and governance challenges related to urban forests. The SFI certification standards for urban forests are grouped into 16 different objectives aimed at continual improvement of urban forestry programs. The 16 core objectives are: fostering community, people, and Indigenous participation; enhancing human health and well-being; conserving biodiversity; stewarding natural resources such as air, water, and soil; promoting tree health and vitality; protecting special sites, including natural areas; implementing climate-smart management; advancing urban forest planning; ensuring effective management and care of urban forests; preparing for and responding to disasters; building capacity; utilizing urban wood resources; strengthening communications; supporting science, research, and technology; adhering to legal and regulatory standards, including Indigenous rights, and maintaining transparent reporting (SFI, 2024). Achieving these objectives should be an end goal for any new SUFMP.

Urban Forests Monitoring

All urban forest management initiatives must be evaluated for their performance using both pre-determined criteria and adaptive judgments of the effect of management strategies on urban forests. As such, consistent long-term monitoring is crucial to supporting and evaluating any urban forest management plan. Monitoring may take the form of updated street tree inventories, canopy cover equity mapping and analyses, policy impacts, woodlands and natural areas monitoring, vegetation monitoring, or public opinion surveys (among a myriad of other monitoring approaches) (Green Municipal Fund, n.d.). Provisions for continued monitoring should be included in all steps of management plans.

Tree maintenance is crucial for ensuring the health and longevity of urban trees, which can directly support the sustainability of urban forests in Canadian municipalities. Depending on the geographic region, environmental conditions, tree age, and species, tree care can include a variety of practices. These include tree pruning, watering, mulching, fertilizing, cabling, bracing, and identifying and removing hazard trees. These practices not only enhance tree vitality but also help mitigate the stresses that urban trees face due to environmental stressors like drought, pests and pathogens, nutrient deficiencies, invasive species, and general damage due to physical stresses like weather or construction activities.

Maintenance Practices

Investment in the maintenance of newly planted and young trees pays off later by having healthy trees and reducing the cost of their management. Some of the most common maintenance practices used for young trees are watering, mulching, pruning to shape the tree for a strong structure, protecting the base of a tree and trunk from mechanical damage, inspecting for pests or diseases, and soil improvement like fertilization. Some of the most common practices to maintain older trees are regular pruning, protection of the root system from soil compaction, supplemental watering during drought conditions, and careful fertilization, which can enhance tree longevity and vitality (ISA, 2021a).

Tree pruning is one of the most common maintenance practices used to support the health, structure, and safety of urban managed trees. Pruning practices include structural pruning of young trees, removal of dead, diseased, or damaged branches, crown thinning, crown raising, pollarding, or in some cases, crown reduction to prevent tree conflicts with structure or utility lines. It is best to time pruning during the dormant season and avoid techniques like topping, which can harm the tree (see chapter: Hydro Lines and Corridors).

Cabling and bracing are structural support techniques used to stabilize trees with weak or multiple trunks, large limbs, or those subject to strong winds (Mayne, 1975; Vandergriff & Clatterbuck, 2005). These methods are particularly useful in urban settings where tree failure can pose significant risks to public safety and infrastructure (Purcell, 2017).

In urban growing spaces where natural water sources may be limited or inconsistent, regular and deep watering is essential for establishing young trees and the development of their root systems in the first few years (2 to 5 years). This is particularly relevant during drought periods, which are becoming more frequent due to climate change, and for newly planted trees, which are particularly at risk of drying out (Steil, 2022; Zuzek, 2018; UMC, 2023).

Mulching complements watering by conserving soil moisture, reducing weed competition, protecting trees from mechanical damage by mowers and trimmers, but also improving root development (Sun et al., 2023; Magditsch, 2021; Qu et al., 2019). Mulching also helps mitigate soil compaction, a common issue in urban environments that can impede root growth and water infiltration. Older trees might also benefit from mulching, which helps conserve moisture and improve soil health (ISA, 2021b).

Fertilizing urban trees is a targeted approach to addressing nutrient deficiencies often found in city soils. However, it is important to apply fertilizers judiciously, as over-fertilization can lead to water pollution and tree health issues (Appleton & Kauffman, 2021; Maine Forest Service, 2000; Bellis, 2023). In Canada, guidelines for urban tree fertilization emphasize soil testing and the use of slow-release fertilizers that match the specific needs of the tree species and site conditions (CFIA, 2024).

Identification and removal of hazard trees are critical for urban forest management practice. Hazard-rating systems, which assess the likelihood of tree failure and the potential impact on people or property, are employed by many Canadian municipalities to prioritize tree maintenance efforts (TRCA, 2006). By assessing key hazard identifiers such as limb damage, wood decay, and cankers, as well as situational conditions such as frequent use areas, proximity to infrastructure, and tree species failure potential, a decision can be made about the size of the hazard and the urgency with which action, such as pruning or tree removal, should be taken against the hazard. Taking a proactive approach in hazard tree management helps manage risks and allocate resources effectively (Gurney & Ward, n.d.; Pokorny et al., 2003; ISA, n.d.).

In addition to traditional maintenance practices, invasive insects and disease management is a growing concern in global and Canadian urban forestry (Sweeney et al., 2019). The spread of pests like the Emerald Ash Borer (Agrilus planipennis) has led to significant maintenance efforts to retain some trees and reduce tree loss, requiring municipalities to implement extensive monitoring, treatment, and removal programs. The City of Montreal, for example, has removed thousands of ash trees (genus Fraxinus) to manage this invasive pest.

Tree Maintenance and Relevant Guidelines 

Canadian municipalities follow national and provincial guidelines for urban tree maintenance, often supplemented by local bylaws and urban forest management plans. These frameworks provide a structured approach to tree care, emphasizing sustainable practices, climate resilience, and community involvement. For instance, the Canadian Urban Forest Strategy (CUFS) promotes best practices in urban forestry, including tree maintenance, and recommends that municipalities integrate urban forest management into broader city planning initiatives (Tree Canada, 2018).

At the provincial level, organizations like the Ontario Urban Forest Council, the British Columbia Urban Forest Network, and the Manitoba Urban Forest Council offer resources and guidance on urban tree care, while municipalities often have their own arboriculture standards and maintenance protocols. These include regular inspections, pruning cycles, and emergency response plans for extreme weather events.

Tree Maintenance and Human Resources

The effectiveness of tree maintenance programs depends on the availability of skilled professionals, including arborists, urban foresters, and municipal staff trained in tree care and management (Trees Are Good, n.d.). Continuous education and training are vital to ensure that the latest techniques and knowledge are applied in the field. In Canada, certification programs such as those offered by the International Society of Arboriculture (ISA) and other regional bodies are widely recognized and help maintain high standards in urban tree care.

Moreover, municipalities often collaborate with community groups and volunteers to support tree maintenance efforts, particularly in the context of tree-planting initiatives and public awareness campaigns. Canadian municipalities can effectively maintain and enhance their urban forests by engaging the broader public in tree care and maintenance, invasive species monitoring, and tree monitoring, contributing to healthier, more livable cities. For example, educating the public on how to prune and maintain their private trees contributes to urban forest health and the enhancement of tree canopy (Johnson et al., 2008; IUFC, n.d.). These partnerships are crucial in fostering a shared sense of responsibility for the urban forest and ensuring its more sustainable maintenance.

Hydro lines and hydro corridors are energy infrastructures within urban areas and Canadian urban forests. The location of hydro lines in Canada, above or below ground, depends on when the urban areas were developed and built. Aboveground hydro lines are found along city streets, sidewalks, and laneways in older subdivisions or neighbourhoods in Canada. One of the most common fixtures on Canadian streets is utility poles with hydro lines attached. Due to maintenance standards, this energy infrastructure interferes with trees and constrains tree canopy development, growth, and height (Appleton, 2006). In newer developments and subdivisions, hydro lines are buried underground, where they have the potential to restrict root growth and tree planting. In both cases, urban trees share limited growing space with these utility fixtures, restricting how many trees and which species can be planted under hydro wires. The design, planting, and maintenance of trees within or near hydro wires always requires careful considerations of factors such as available growing space, proximity to hydro wires, future risk of tree interference with electrical infrastructure, compliance with local regulations or utility guidelines, tree species selection, tree height and canopy spread at maturity, growth habit, long-term maintenance requirements, tree trimming or pruning, accessibility for maintenance crews, the potential for breakage during storms or high winds, visual aesthetics, and community impact  (Dupras et al., 2016; Appleton, 2006; Bloniarz, 1992; Browning & Wiant, 1997). 

Hydro Lines

In the planning and design phase, landscape and tree planting plans in areas under or close to hydro lines should consider tree height and canopy spread at maturity. It is crucial to carefully plan tree planting based on tree size at maturity, growing conditions (soil, nutrients), and distance from hydro lines to determine which species are suitable to plant under hydro wires. Choosing the right tree species can reduce pruning and maintenance intensity, leading to healthier, more aesthetically pleasing trees along streets and under hydro lines. More importantly, the right tree species can significantly reduce the risk of power outages and accidental fires, resulting in economic savings (Bloniarz, 1992). Power companies and many Canadian municipalities (see Canadian Online Resources section) have a list of recommended tree species that are suitable to plant adjacent to power lines (Appleton, 2006).

It is standard practice for utility companies across Canada to perform routine tree maintenance along power lines and corridors (Parent et al., 2019; Perrette et al., 2021). Utility companies also maintain street trees and park trees that are within range of hydro lines. To ensure safety and hydro wire clearance, trees under or near hydro lines are managed on an individual basis. Maintenance around power lines can only be done by trained and certified professional arborists. Canadian utility companies often develop and provide various tree resources, including tree pruning maintenance standards, hazards to watch for, and a list of certified arborists in the area on their websites (see Canadian Online Resources section). Trees along power lines are usually pruned at 5-6 years intervals, but some can be as frequent as 3 years (Perrette, Delagrange, & Messier, 2020; Browning & Wiant, 1997; Millet & Bouchard, 2003; Millet, 2012; Lecigne et al., 2018). A good understanding of tree species biology can help improve pruning practices, lessen its impact on trees, and reduce pruning costs (Perrette, Delagrange, & Messier, 2020; Millet, 2012). Additionally, consistently assessing the overall health of a tree can help determine the frequency of pruning and its suitability for extensive pruning (Perrette et al., 2021). This, in turn, can inform maintenance planning to optimize the allocation of time, human resources, and funding. 

Hydro Corridors

In addition to hydro lines, urban areas are often intersected by transmission corridors, commonly called hydro corridors. Hydro corridors are long and narrow linear spaces, covered by shrubs and grasses, used by hydro companies for high-voltage hydro transmission, which requires very tall transmission towers. These areas have strict regulations regarding the type of vegetation growing under transmission lines due to safety concerns. Trees are prohibited under and within a certain distance from the transmission lines because their height can pose safety risks. Electricity can easily arc out of transmission lines and jump into the taller tree branches. As a result, vegetation directly under hydro lines in hydro corridors should be low. Different hydro companies and municipalities may have different rules, but most guidelines indicate that woody vegetation over 6 meters is not permitted in these areas (Hydro Ottawa, 2025).

The hydro corridors themselves can support native plants and provide habitats for wildlife, insects, and birds. They often act as ecological corridors and serve as a landscape linkage between urban centers, rural communities, and beyond (Hydro Ottawa, 2010). There has also been a repurposing of how land under hydro corridors is used in urban areas, from providing recreational spaces and supporting urban gardening to strategically enhancing urban biodiversity and improving ecological connectivity in Canadian cities. For example, the Meadoway 16-kilometre-long hydro corridor in Toronto has been gradually transformed into a native meadow and will become a linear urban park when finished (TRCA, 2022). Hydro corridor lands have been incorporated into the urban green system to support recreation in Winnipeg (Sage Creek, 2023) and urban biodiversity restoration in Calgary (City of Calgary, n.d.). Similar efforts towards restoring hydro corridors and converting them to native plant communities and wildlife habitats are happening across many Canadian cities, such as Montreal, Guelph, and Ottawa, to name a few (Hydro Quebec, 2024; Milkweed Journal, 2016; OSC, 2024).

Appropriate tree species selection should be based on environmental, ecological, social, infrastructural, and tree maintenance considerations. For example, tree selection should ensure an urban forest that is resilient and that can endure challenging urban environmental conditions, including air and soil pollution, soil compaction, drought, and road salt. Tree selection and planting are also site-specific and should consider soil properties, moisture availability, wind, frost, and light exposure (Nowak et al., 2010). Species-specific characteristics such as tree growth rate, shade tolerance, and visual appeal also play a critical role in species selection. In addition, considering maintenance needs is critical as this can determine long-term sustainability of urban forests and reduce management costs (Almas & Conway, 2016; LSRCA, 2018; Nowak, 2000; Conway & Vander Vecht, 2015). 

Tree Selection and Sites

Tree species selection should be based on site conditions, location, species compatibility with local climate and species hardiness zone, tree size, form, and aesthetic/public appeal. Other factors to consider are tree growth rate, environmental suitability (soil characteristics, pH, moisture regimes, salt tolerance), and the tree’s function within the space (shade provision, aesthetic, etc.). Well-considered criteria for tree species selection can result in secondary benefits for the larger urban forestry program. Some of these benefits include reducing long-term maintenance costs, building an urban forest resilient to climate change, providing manageable urban forest solutions to neighbourhoods and communities, and maintaining a diversity of tree species that benefit wildlife in cities and towns (Almas & Conway, 2016). 

In the design and planning stage of tree selection, trees should be visualized at full functional size. This helps to minimize later conflicts between trees and structures and reduces maintenance needs that may arise from unexpected issues. Selecting a tree that is well-suited to the soil conditions, light availability, pedestrian traffic, drainage, space, and microclimate of the specific site is essential to the tree’s long-term survival and to public safety (Vibrant Cities Lab, n.d.). 

To make the decision process easier, Canadian municipalities often list species that can thrive in their specific urban context based on the tree selection considerations and their experience (see City of Markham, 2009; City of Kelowna, 2020; City of Toronto, 2021, 2024; Metro Vancouver, 2017; Ville de Quebec, n.d.). 

Climate Change 

When selecting tree species, their long-term climatic suitability is increasingly important for successful planting decisions. As climate change brings warmer weather to many Canadian cities, individual species’ suitability is expected to change over time (Khan & Conway, 2020). The composition of urban forests needs to adapt and shift in anticipation of this trend. Suitable climate conditions for many tree species are shifting northward much faster than trees can naturally migrate (Metro Vancouver, 2017). As a result, tree species selection must be based on forethought and consideration of changing climate regimes, rising temperatures, and levels of tolerance that individual tree species have for rising temperatures and shifting conditions.  

To determine a species’ suitability in the context of climate change, a combination of historical range, current suitable habitat, and climate projection models can be used as a basis for analysis (LSRCA, 2018). This process helps determine if a species is retreating northward, continuing to persist, or becoming a new suitable possibility. Trees and other species that are becoming increasingly unsuited to their location may experience stunted growth and shorter lifespans. Species that persist in urban settings tend to have a wider ecological amplitude and climatic range and are likely to continue to thrive in the future (Das, Ossola & Beaumont, 2024; Liang & Huang, 2023).

For species that may become more suitable as climate change progresses, testing their survivability in the new environment before widespread implementation by planting limited amounts can prevent large-scale tree mortality in the future (LSRCA, 2018). These assessments should be updated as more data for different species and new climatic models become available. Flexibility in modifying planting programs can help mitigate the risk of implementing new species.  

Since urban forest planning is a long-term vision and young trees take years to grow, active engagement with nurseries can ensure that sufficient planting stock of specific species is available. Coordination with nurseries can also lead to the sharing of knowledge, which can be a hugely beneficial source of information in implementing new planting programs or testing of new tree species (Khan & Conway, 2020; LSRCA, 2018).

Species Diversity and Composition

The diversity of tree species is critical in building and maintaining a resilient urban forest. Having a large variety of tree species allows an urban forest to better absorb shocks brought by pests, diseases, and climate change. For instance, the spread of Emerald Ash Borer put around 20% of Montreal’s urban forest at risk, and thousands of trees were cut down between 1999-2020 (Canadian Institute for Climate Choices, 2021). Many of the trees that were impacted were mature with wide-spreading canopies, which provided various benefits like climate regulation, air quality, and stormwater management benefits that a newly planted sapling could not immediately replace. Ash trees across North American cities were impacted at similar or worse rates. This highlights the importance of supporting tree diversity to strengthen urban forest resilience to a changing climate and environmental threats.

In addition to considering urban forest diversity, tree species that are dioecious (male and female trees), tree species sex and overall tree diversity should be considered when selecting trees to plant. Historically, male trees have been preferably planted in urban settings as they are considered less “messy” and do not produce fruits or seeds (Nowak & Ogren, 2021). While female plants produce fruits and nuts and provide food for birds and other urban wildlife, they require higher maintenance and upkeep. As a result, they have not been favoured for planting to avoid fruit cleanup in high human traffic areas. Studies have shown how the planting of mostly male trees across cities in North America has led to increased urban pollen concentrations, which has been correlated with increased seasonal allergies. Favouring male trees has a long-term impact on urban forest and tree species composition, as well as resilience against pests and overall city biodiversity. It also contributes to perceived tree disservices as overproduction of pollen can impact human health (Katz, Robinson, Ellis & Nowak, 2024).

Furthermore, urban trees planted along streets, parks, in residential and institutional areas often include many cultivars selected for their specific traits, such as growth rate, canopy shape, leaf and flower colour, the absence of fruit, visual appeal, or other features. The predictability of their growth and other characteristics, and how these trees eventually grow, make these cultivars desirable for some urban environments and landscaping. There are hundreds of cultivars, of which some have been planted more than others. However, cultivars are clones that share identical genetic material, reduce genetic diversity, and increase vulnerability to pests, diseases, and environmental stressors. Heavily relying on cultivars can lead to portions of the urban forest becoming monocultures, but also having monocultures across cities (Avolio, 2023; Sacre, 2020; Lohr, Kendal & Dobbs, 2016).

Tree Planting

Tree planting material should be inspected for damage and disease before being purchased from nurseries to ensure successful tree establishment and growth. Some common issues of tree planting materials are damage to the trunk, broken branches, or injuries to the root system (International Society of Arboriculture, 2021). The three common types of nursery trees are ball and burlap, container, and bare root stock. Each has its advantages and limitations when planting and should be selected based on the needs of the site or project (International Society of Arboriculture, 2021; Natural Resources Canada, 2023). The Arbor Day Foundation has a useful guide on how to plant each type of nursery tree. Planting under specific circumstances may have different requirements, such as when planting under power lines or for hard-surface planting in intensely urbanized areas. 

Depending on how trees are packaged and sold, their planting methods differ. Young trees often come in containers, as ball and burlap, or as bare root trees. One of the main concerns for trees that come in containers is root girdling. Root balls should be loosened on the bottom and sides to ensure no roots grow to choke the plant (International Society of Arboriculture, 2021a; Tree Canada, 2023). For trees that come in ball and burlap, it is important to cut away the burlap and wire basket, or the packaging will slowly strangle the tree as it grows (Tree Canada, 2023). For bare root stock, the most important thing is to ensure that the root does not dry out prior to and during the planting process (Virginia Department of Forestry, n.d.). The ultimate goal of urban tree planting is for the trees to reach maturity and provide maximum benefits, such as carbon sequestration, shade, and biodiversity. Therefore, monitoring and maintaining young trees so that they continue growing and thriving is an imperative part of urban forest management. 

With increased urbanization, environmental and climate changes, healthy, long-living urban trees are critical for providing ecological services such as air quality improvement, stormwater management, and energy conservation. However, these benefits cannot be fully realized when tree growth is limited by inadequate space and soil (Mullaney, Lucke, & Trueman, 2015a). One of the most persistent challenges in establishing and maintaining a healthy, resilient, and functional urban forest is the ongoing battle between tree roots, gray infrastructure, and various hard surface pavements. Due to the lack of ample growing space, trees are often planted in restricted soil spaces surrounded by pavement, asphalt, or concrete. As a result, such trees often have limited soil volume to support their growth, inadequate access to nutrients, and a lack of oxygen and water to support their basic physiological functions. 

Conflict with urban structures, limited growing space, and hard surface covering the root system can lead to root damage and root girdling. This often results in pavement lifting as roots of large trees try to access nutrients and water (Watson, Hewitt, Custic & Lo, 2014; Mullaney et al., 2015a). Pavement lifting creates safety hazards for street users, causes concern for property owners and residents, and significantly impacts the aesthetic value of public spaces (Watson et al., 2014). 

Recent studies reveal that surface paving also significantly affects the ability of trees to provide ecological services. Surrounding hard surfaces influences a tree's cooling effect more than species selection, highlighting the strong impact and restrictions pavements impose on urban trees' health and ecological functions. This underscores the strong impact and restrictions that hard surfaces impose on the health of urban trees and their ecological functions (Konarska et al., 2023). 

Planting trees on hard surfaces and as part of new developments can be very expensive, and without proper forethought, can bring few benefits and prove to be a liability. When tree planting is carefully designed, planned, and implemented, hard-surface tree issues can be avoided or minimized. Healthy tree growth and survival can be ensured by selecting appropriate tree species for the growing space available, using an adequate soil medium to encourage tree root growth, constructing continuous channels connecting individual planting pits, implementing pervious paving around trees, and providing sufficient irrigation. 

Land use and site planning decisions, combined with poor tree selection and planting practices, can generate problems down the road. However, past mistakes are learning opportunities for improving future practices. For example, studies on permeable paving with deep granular substrates have shown promising results in mitigating damage to the pavement and tree roots by allowing them to grow at greater depth. The permeable pavement supplies the soil with sufficient oxygen, nutrients, and moisture to allow for woody growth at greater depths without impacting the growth rate (Lucke & Beechman, 2019). Still, depending on the soil type of the underlying base layer, the effectiveness of permeable pavement may vary (Mullaney et al., 2015b). 

There are solutions to improve the existing trees' growth conditions, allowing them to extend their life and continue to provide ecological services. Management and maintenance of trees to support root growth within hardscapes include techniques such as de-pavement, soil aeration, soil improvements, building bridges over tree roots, and establishing root barriers. However, these interventions are often short-term solutions as tree roots continue to grow, and trees might decline, necessitating additional interventions. This also underscores the ongoing nature of tree management and the need for continuous tree care (Watson et al., 2014). There are less costly and site-specific techniques to improve the growing conditions. For example, planting flower beds and other vegetation around tree trunks or installing covers or grates over planting pits can reduce foot traffic around trees while also helping to improve soil conditions.

In places where soil volume and quality are lacking, structural soil can be implemented to ensure healthy root growth. These solutions are often used in highly urban environments such as parking lots and downtown streets with lots of pavement and traffic. This planting solution protects the growing medium from compaction and is formulated to provide the nutrients needed for tree growth. Structural soils are expensive to implement, difficult to maintain, and often provide limited years of tree growth and performance shorter than a tree's typical lifespan. However, it is usually the only viable solution in intensely urban areas with heavy pedestrian traffic.

Natural areas such as woodlots, ravines and other open areas with self-sustained vegetation make up a significant component of the urban forest and land-use fabric. They are composed of natural and semi-natural vegetation and managed for their multiple ecological and social functions. Natural areas are a component of the urban forest that are managed at a stand (i.e. group of trees) level. They are a vital part of urban green infrastructure and enable linking urban areas and regional networks (City of Ottawa, 2022; Ontario Nature, 2014). Due to their position near and within cities, urban woodlots and natural parks also face multiple anthropogenic challenges including pollution, contamination, and heavy recreational pressure which leads to soil compaction and invasive species proliferation. They also tend to have multiple groups of stakeholders who all carry different needs and management capacities (Duinker et al., 2017; Miller et al., 2015). 

As critical components of the urban forest, urban natural parks and woodlots hold native diversity and provide wildlife habitat, absorb and filter rainwater, and provide outdoor recreation opportunities to city residents. Urban woodlot and park management involves addressing several common issues, including ensuring safety via regular tree and risk assessments, mitigating the impacts of recreation such as soil compaction and garbage dumping, and monitoring and managing invasive species to limit their spread and negative effects on plant and wildlife communities. Efforts also focus on encouraging community use and stewardship by supporting involvement in tree planting, restoration, and other stewardship efforts and activities, as well as protecting and restoring ecosystems through ongoing monitoring and initiatives to strengthen forest health. Because of their many functions, pressures, and stakeholders, urban woodlots and parks should be managed with multiple goals in mind. Their management should be based on detailed knowledge and data about their structure, composition, and health, as well as the pressures of community use (Duinker et al., 2017). 

The management of natural parks and woodlots involves several steps. First, determining clear management goals is essential to guide all subsequent actions. These goals may include enhancing biodiversity, promoting recreation and ecological values, ensuring safety, preserving culture, or storing carbon. Conducting a detailed and informative inventory that includes the entire vegetation community composition provides the base data necessary to develop an effective management and conservation plan. Detailed data collection enables assessing the current state of the woodlot or park, including its flora, fauna, soil conditions, water resources, and any existing human impacts or infrastructure (Tuckett, 2013; Puric-Mladenovic & Baird, 2017). Specific management and conservation strategies are developed by following set objectives and are based on inventory data and identified environmental and anthropogenic pressures. Management strategies may include controlling invasive plants, managing trails to reduce soil compaction, planting native species, or engaging the community in restoration projects. 

While similar problems and opportunities might be present across natural areas and woodlands, individual urban woodlands or patches of natural areas often need to be evaluated and managed according to their specific attributes, policy designation or role in the local urban ecosystem. For example, some of them might have a higher density of trails, deer browsing issues, and a decline in tree species. Some could provide wildlife or species at risk habitat or require fire to manage native biodiversity, such as High Park in Toronto (High Park Nature. 2019).

In terms of woodlot management activities, cities such as Guelph, Saskatoon, Winnipeg, and Halifax have focused management plans to manage the spread of invasive buckthorn using chemical strategies such as herbicides and physical methods such as tree cutting (ISC, n.d.). Other examples include municipalities that have prioritized biodiversity and conservation in these natural remnant woodlots (City of Toronto, 2019; City of Surrey, 2014; City of Edmonton, 2009). Some other Ontario municipalities are partnering with academic institutions or allied organizations with established vegetation monitoring and research to better understand and manage these natural areas (Puric-Mladenovic, 2015; Puric-Mladenovic & Baird, 2017). Urban woodlot management comes in many forms and must be based on detailed data, guided by set goals at an individual woodlot level, and updated regularly based on community needs and ecological health.

Dans le domaine de la foresterie urbaine, la préparation aux urgences est primordiale pour protéger les arbres et les boisés ainsi que les collectivités qui en dépendent. Les villes canadiennes sont confrontées à des menaces de plus en plus importantes de catastrophes naturelles (feux de forêt, inondations, chaleur extrême, propagation de ravageurs et de maladies). C’est pourquoi il est essentiel que les pratiques de foresterie urbaine se concentrent sur l’entretien de routine, mais aussi sur la préparation et la résilience.

La tempête de verglas dans l’est du Canada de 1998, les répercussions et la propagation de l’agrile du frêne, la tempête Derecho (Ontario, 21 mai 2022), l’ouragan Juan (Nouvelle-Écosse, 29 septembre 2003) et les feux de forêt de Colombie-Britannique de 2003 illustrent clairement la nécessité pour les municipalités d’intégrer la préparation aux urgences et la gestion des catastrophes aux plans de gestion des forêts urbaines. La préparation aux urgences contribue à limiter les dommages, garantit la sécurité publique et permet de planifier et mettre en œuvre les initiatives de rétablissement à la suite d’une situation d’urgence (Sécurité publique Canada, 2022a).

Incorporer la gestion des catastrophes à la gestion des forêts urbaines inclut plusieurs composantes essentielles à la fois préventives et réactives. Parmi les mesures préventives, on peut citer l’évaluation des risques, la planification et la prévention. L’évaluation des risques inclut l’identification des vulnérabilités et la cartographie des zones à haut risque à l’aide de données d’inventaire et de surveillance, tandis que les mesures de planification et de prévention comprennent les inventaires d’arbres, la surveillance de la santé, l’entretien proactif des arbres (par exemple, l’élagage) et la protection des infrastructures (par exemple, la gestion des arbres à proximité de lignes électriques). Les mesures réactives incluent l’application de plans d’intervention et la coordination de la réponse aux urgences et des efforts de rétablissement. Cela passe par la collaboration avec des agences d’intervention d’urgence et de gestion des terres, la communication avec le public et les évaluations après la catastrophe (par exemple, l’identification des arbres endommagés). Les efforts de rétablissement doivent cibler des stratégies pour replanter des arbres, pour restaurer les terres et affiner la préparation à l’avenir (US Forest Service, s. d.; Smart Trees Pacific, 2013a; Huff, E. et al., 2020). Des plans d’intervention complets en cas d’urgence doivent également inclure des mesures préventives et réactives qui donnent la priorité à la sécurité des équipes et du public pendant et après les urgences (The Arborist Safe Work Practices (ASWP), 2023).

Stratégies de gestion et d’atténuation

Les municipalités doivent allouer les ressources appropriées dans leurs budgets pour se préparer aux catastrophes, y compris en finançant des formations spécialisées pour le personnel en foresterie urbaine. La formation doit couvrir la gestion sécuritaire de situations dangereuses, comme des lignes électriques tombées à terre ou des arbres instables, et l’application de protocoles de santé et de sécurité. Par ailleurs, des exercices et des simulations réguliers permettent de s’assurer que le personnel est bien préparé pour répondre rapidement et efficacement en cas de catastrophe (Gouvernement du Canada, 2024b). Les villes devraient également investir dans des ressources humaines spécialisées dans la gestion des catastrophes au sein du secteur de la foresterie urbaine. Cela comprend des postes chargés de l’évaluation des risques, de la planification des urgences et de la sensibilisation du public à l’importance de l’entretien des arbres dans l’atténuation des catastrophes (Konijnendijk et al., 2021). La collaboration avec des agences locales, les services publics et les organismes communautaires est également essentielle pour garantir une réponse concertée en cas de situation d’urgence.

Les stratégies et politiques canadiennes soulignent par ailleurs l’importance de la gouvernance et de la coordination entre les différents ordres de gouvernement et services d’urgence. Par exemple, la Stratégie canadienne en matière de feux de forêt (Conseil canadien des ministres des forêts, 2016) présente une approche concertée de la gestion des feux de forêt, tandis que Sécurité publique Canada (Sécurité publique Canada, 2022b) fournit des lignes directrices pour la gestion des urgences qui ont des répercussions sur la foresterie urbaine. Les municipalités peuvent aussi bénéficier de programmes provinciaux comme le programme de protection de la santé des forêts de l’Ontario (Gouvernement de l’Ontario, s. d.), qui soutient la gestion des épidémies de ravageurs et de maladies [Voir le chapitre Insectes et maladies].

Il est indispensable d’intégrer la gestion des catastrophes aux plans de gestion des forêts urbaines. De nombreux plans de gestion municipaux des forêts urbaines comprennent une section sur la préparation aux urgences. Les municipalités doivent viser à adopter des stratégies, des politiques et des pratiques robustes pour que les villes puissent mieux protéger leurs forêts urbaines et, par extension leur population, des risques grandissants posés par les catastrophes naturelles.

Urban areas, though they make up about 1% of the land base in Canada, are home to over 80% of the population and taxpayers. Urban areas and their populations serve various national and provincial interests, yet there is no national urban forest legislation, and existing local-level policies are decentralized. As a result, urban forest policy in Canada is fragmented among municipalities and exists without significant involvement from upper levels of government (Kenney 2003; Barker and Kenney 2012). Thus, most urban forest policies are not determined by provincial or national governments, but by municipalities (Hudson, 2014). With decentralized governance across three levels of government, urban forest protection and management decisions are largely made at the municipal level. 

Urban forest policies and management are complicated due to the variety of land ownership in urban areas, the shifts in rights and responsibilities, and the intersection of land use policies and planning regulations. In response to public pressure, some municipalities take a proactive approach to protecting trees and urban forests, while others adopt a more reactive stance, prioritizing development over environmental preservation. Urban tree legislation and bylaws can vary greatly between municipalities and across geographic areas; these differing bylaws and levels of management have been captured in a 2018 project that measures the footprint of urban forestry in Canada (Puric-Mladenovic & Bardekjian, 2023a, b). This tool serves as a resource for small and large municipalities looking to start new or develop upon existing urban forestry programs.

Municipal urban forestry programs have a wide variety of management areas and responsibilities, such as managing street trees, removing hazardous trees, and planting trees in new subdivisions. There are various policies relating to trees and urban forests, all of which are adopted by municipalities as tools to aid in protecting trees and regulating the injury of trees. There are nine major areas of municipal policy related to trees and urban forests in Canada: (1) policy related to tree permit (e.g., tree removal permit, tree harvesting permit, and certificate of authorization), (2) policy related to standards of trees in new subdivisions (e.g., development specifications, landscape screening, shoreline buffer), (3) policy related to tree planting guidelines, (4) policy related to the choice of tree species (e.g., the list of recommended/prohibited tree species), (5) policy related to boulevard trees, (6) policy related to commemorative trees, (7) policy related to protection of heritage trees and natural heritage, (8) policy related to planting of native trees, and (9) policy related to planting of shade trees (Puric-Mladenovic & Bardekjian, 2023a).

Municipal Bylaws

Tree bylaws are created by municipalities and implemented within municipal boundaries. Tree bylaws support safe, sustainable, and legal tree-related activities in Canada and are often written in accordance with private property laws and city-curated forest management and land use plans. For example, tree bylaws state prohibited activities, exemptions, permit requirements, and rule enforcement through necessary processes, fixed fines and penalties (City of Guelph, 2010). Tree bylaws, depending on their implications, are under different provincial acts. Oftentimes, municipal plans also include provisions for public engagement in tree-related policy (CEN, n.d.). In British Columbia, the Community Charter acts as an “umbrella regulation,” and in Ontario, the Municipal Act of 2001 empowers municipalities to enact tree bylaws. In Newfoundland, the New Urban and Rural Planning Act is the enabling legislation that establishes the province’s land use planning system; it allows the preparation of a range of planning, grant approval, and implementation documents, and provides public input and appeal processes whereby development decisions can be subjected to independent review (De Santis, 2020). This Act serves as an umbrella regulation to manage urban and rural planning (Puric-Mladenovic & Bardekjian, 2023).

The study by Puric-Mladenovic and Bardekjian (2023b) shows that there is a wide range of bylaws pertaining to trees in Canadian municipalities. Over one-fifth (22.8%) of the surveyed municipalities in 2018 had enacted private tree bylaws in response to the municipal need to regulate the injury and removal of trees. Of the surveyed municipalities, 18.3% have public/street tree bylaws. As expected, most of the 146 Canadian municipalities that have enacted public tree bylaws are in the more urbanized provinces, such as Ontario (26%), followed by British Columbia (24%) and Quebec (17%). Of the 182 municipalities that have private tree bylaws, the majority are in Quebec (57.7%), followed by British Columbia (22%) and Ontario (13.7%). 

A recent study revealed that in Ontario, more populous municipalities tend to have more tree by-laws, suggesting the influence of various factors such as more available funding, stronger political will, higher capacity for compliance and enforcement, and increased public pressure (Yung, 2018). Additionally, the study highlighted significant variation in the types of tree bylaws and policies across municipalities in Ontario. This variability reflects a reactive and fragmented approach to tree protection, with each municipality adopting its own unique strategies and regulations.

Public tree bylaws control activities on public property and city operations, such as hydro utility practices, landscaping activities, pest management, construction, and residential, industrial, and commercial development planning (City of Edmonton, 2019). Private tree bylaws regulate tree-related activities on private property, such as tree-cutting, tree removal, tree topping (removal of large portions of a tree’s crown), and building practices (Conway et al., 2022). Some municipalities such as Prince George’s County in Maryland, USA, have tree canopy replacement bylaws, where several trees must be planted to supplement the removal of large amounts of canopy or large old trees (Dalke & Hawkins-Nixon, 2012), These “no net loss” or “net gain” bylaws help preserve and even increase urban canopy cover while still allowing regular tree maintenance and removal when necessary.

Municipalities are also increasingly acknowledging the value of woodlands, biodiversity, wildlife habitats, and ecosystem services through their tree bylaws. For instance, the City of Peterborough’s Tree Conservation Bylaw (By-Law Number 17-120) explicitly recognizes the environmental, aesthetic, and public health benefits of trees. The bylaw also regulates the destruction and injury of trees on private property. Similarly, the Town of Orangeville’s Urban Forestry Policy highlights the environmental, economic, and health benefits provided by urban trees (Yung, 2018).

In Quebec, many municipalities have adopted bylaws requiring permits and certificates for tree-related maintenance, which have explicit provisions regarding the “obligation of obtaining a certificate of authorization to fell a tree”. In Ontario, 23.2% of municipalities (103 out of 444) had specific tree policies in 2018. These policies cover a wide range of disciplines and municipal departments, such as Guidelines for Trees and Landscaping, Specifications for the Planting of Municipal Trees and Shrubs, and Tree Preservation and Clearing Guidelines for New Developments (Puric-Mladenovic & Bardekjian, 2023b). However, 74.5% of Ontario municipalities (331 out of 444) did not have tree bylaws in 2018.

In 2018, in Quebec, 44.2% of municipalities (106 out of 240) had tree bylaws (either private or public). The tree bylaw has been enacted as part of a zoning bylaw, which regulates tree cutting and plantation in both urban (e.g., residential areas) and industrial settings. Such bylaws set out the regulations and guidelines for tree felling or planting, which require owners to apply for a tree permit or certificate of authorization. In Quebec, a bylaw to stop the spread of Emerald Ash Borer has been passed in recent years, and about 8% of municipalities (19 out of 240) in Quebec had such bylaws in 2018. 

In Saskatchewan, about 26% of municipalities (6 out of 23) have adopted the Urban Forestry Bylaw or Urban Tree Policy Rules and Regulations Bylaw. There are provincial regulations regarding urban trees (e.g., Dutch Elm Disease Regulations in Saskatchewan), which result in more standardized urban forestry programs (such as Dutch Elm Management Programs across the province). All of these bylaws and regulations are essential to the maintenance and management of urban trees and forests in Canada. 

Tree Protection & Construction

In urban areas, there is often competition between development activities and trees due to a lack of available growing space. Urban trees are frequently impacted by infrastructural maintenance, underground utility expansion, or building construction. When construction is close to or within tree root zones, soil removal, trenching, heavy machinery, and repeated foot traffic cause soil compaction and root damage (Despot & Gerhold, 2003). Sometimes, unintended movements by heavy machinery can also result in mechanical damage to the above-ground tree parts. For example, common construction activities such as paving, sidewalk (re)installations, excavation, trenching, and roadway widening involve various machinery that can severely affect the existing trees (Despot & Gerhold, 2003).

Without adequate protection during construction, trees can be damaged, leading to a decline in tree health, which can be deadly. In worst cases, these injuries can lead to functional and structural damages that appear as weak foliage, canopy decline, rot and decay, or even tree death (Hauer et al., 2020; North et al., 2017). Damage to roots caused by compaction can impact tree access to water and nutrients, ultimately compromising its health, longevity, and ability to recover (Fini et al., 2020). In many cases, tree decline and death can take years to become apparent (Fini et al., 2020). It has been documented that trees in construction zones experience a higher annual mortality rate and have worse tree health than trees not impacted by construction (Hauer et al., 2020; Hilbert et al., 2019). Trees previously exposed to construction damage are also more vulnerable to other environmental and biological stressors. For instance, a tree stressed during construction may not exhibit obvious signs of decline until a period of drought occurs, causing crown defoliation and eventually other health problems like dieback, limb loss, and increased susceptibility to insects and disease (Fini et al., 2020). This might appear as a sudden decline, but due to root reduction from construction impacts, the already-stressed tree has limited access to water, oxygen, and nutrients and can no longer handle additional environmental stress. However, the rate of post-construction tree decline depends on many factors such as the age of trees, tree species, the extent and nature of damage, the health of the tree prior to construction, and care given after construction is complete (North et al., 2017; Fini et al., 2020). 

Evaluation of green space and trees, as well as implementing strategies to save and protect urban trees, should be a critical part of urban development. An assessment should be completed before starting construction to ensure the conservation and preservation of existing trees and, thus, maintain the urban forest canopy and its integrity. Studies have shown that investing in tree protection for mature trees positively impacts the overall tree canopy within urban environments (Benson, Koeser, & Morgenroth, 2019a). Urban forest studies continuously refine tree protection recommendations based on emerging root damage and tree health studies. For example, Benson et al. (2019a) recommend providing a protection zone 15 times the diameter of the tree in question to ensure tree health. Not only do mature trees add to the aesthetic value of public spaces, but they also provide ecosystem and infrastructural services that cannot be easily replaced (Hotte et al., 2015). However, questions always remain about the appropriate extent of the tree protection zone, and this type of research continues to advance relevant knowledge (Benson et al., 2019a; City of Toronto, 2016; Matheny & Clark, 1998). 

Best management practices to protect trees during construction include construction-specific tree protection bylaws, site plans that ensure adequate space for tree roots, and tree, soil, and root protection measures. Many large Canadian municipalities mandate these measures, which are reflected in protection bylaws, guidelines, and urban forest management plans (Yung, 2018). Tree-protection plans often include physical barriers at a certain distance around trees that typically restrict access to their root zone and stem. These barriers protect the soil around the tree from compaction and can also prevent damage from machinery. Construction documents often detail what can and cannot be done within set distances from each tree (Despot & Gerhold, 2003). Tree protection techniques and guidelines are backed up by research that tracked tree health for years and decades after construction (Hauer et al., 2020; Fini et al., 2020). In special situations where additional expertise is needed, a professional arborist or forester may provide recommendations related to protecting and preserving trees near construction projects. 

Trees and Building Foundations

Many urban trees are planted too close to buildings or other gray infrastructure. This could be due to lack of space, lack of knowledge of how trees will develop over time, planning designs that disregard trees as living and growing organisms, or an inappropriate species or cultivar selection for the given space. As a result, trees often grow in conflict with structures and have the potential to cause direct or indirect damage to urban structures. An example of direct conflict between a tree and structure is when a tree trunk or stem grows into a building or a tree root grows into the pavement (Overkeke, 2008; Day, 1991). When tree roots search for water, air, and nutrients, they can grow into undesirable places; intruding root growth is often prompted by existing cracks in the structures or pavement, which allows moisture to seep through. This can be avoided by considering the mature size of a tree prior to planting, including the extent of the root zone, and by selecting the right species for the space (Overkeke, 2008). 

Tree roots can contribute to the settling of substrates under and around building foundations. Studies show that a combination of clay soil, proximity of trees to structures, and quality of construction can lead to indirect damage to buildings over time (Navarro et al., 2009; Overkeke, 2008; Day, 1991; Vorwerk, Cameron, & Keppel, 2015). Clay soil is especially prone to shrinking and expanding, which can lead to more movement around buildings as they settle and create a space in which tree roots can develop (Overkeke, 2008; Vorwerk, Cameron, & Keppel, 2015). When trees are planted too close to the foundation, they can add to the amount of water extracted from the soil (clay soil in particular) and lead to more root movement over time. Since the water demands of trees are species-specific, the soil type and species should be considered when creating a planting plan. Planting far away from buildings or structures is a good preventative measure in areas with clay soil; the notable exception to this recommendation is for rail tracks and sloped embankments built on clay soils, where vegetation provides necessary stability (Vorwerk, Cameron, & Keppel, 2015). Lastly, as structures with shallow foundations are especially prone to damage, infrastructure solutions such as deeper perimeter foundations are also a helpful preventative measure (Day, 1991). 

Urban trees face numerous abiotic stresses that significantly affect their health, growth, and longevity. These stresses include limited soil volume, soil compaction, air pollution, road salts, heavy metals, drought, mechanical damage, light pollution, and the urban heat island effect, to name a few. The local conditions of urban environments intensify the magnitude of these stressors and their impact on trees. Understanding and managing these cumulative impacts is crucial for the sustainability of urban forests (Collins, 2007).

Soil compaction and inadequate soil volume are persistent challenges for trees in built-up areas. Unfavourable soil conditions and limited rooting space negatively impact sustained tree growth and physiological functions due to reduced oxygen, restrained water and nutrient availability. For example, soil compaction increases bulk density and reduces soil pore space, restricting the growth of fine feeder roots essential for absorbing water and nutrients. In turn, this makes trees more vulnerable to drought and other stressors, which can lead to the premature decline of urban trees over time and threaten the overall health and resilience of the urban forest (Cushing, 2009; Jim, 2023).

Air pollution, including particulate matter, ozone, sulphur dioxide, and nitrogen oxides, impacts urban trees by reducing their photosynthetic efficiency and growth. It has been shown that trees exposed to high levels of air pollution may exhibit symptoms like chlorosis, reduced leaf size, and premature leaf drop, which weaken trees, making them more susceptible to other stresses (Grote, 2016; Moore, 2023).

The use of de-icing salts is another stressor that poses a significant threat to urban trees in Canada. Road salts, primarily sodium chloride, accumulate in the soil, leading to osmotic stress and toxicity. Symptoms of excessive road salt on trees include leaf scorch, reduced growth, and even death, particularly in poorly drained areas (Equiza et al., 2017; Government of Canada, 2015). With regards to road salts, reducing salt application, using alternative de-icing materials such as sand, choosing salt-tolerant species, and designing landscapes to minimize salt runoff are effective strategies that help sustain urban forests (Government of Canada, 2015; Transportation Association of Canada (TAC, 2024). 

Urban trees, particularly those near traffic and industrial sites, often accumulate heavy metals in their tissues, causing toxicity and leading to impaired tree growth. These contaminants can reduce growth rates, cause leaf discoloration, stress trees and increase their vulnerability to pests and diseases. Studies have shown that heavy metals like copper, mercury, manganese, nickel, lead, and zinc are found in higher concentrations in the bark of trees growing closer to streets, contributing to long-term physiological stress and reduced growth (Nechita et al., 2021; Yousaf et al., 2020; Kargar, 2013). It is essential to monitor and manage soil quality regularly, remediate contaminated sites when necessary, and select tree species tolerant of pollutants (Nechita et al., 2021)

Drought is a common stress in urban areas, especially during summer when water availability is limited. Urban trees, already stressed by poor soil conditions and impermeable surfaces, are more vulnerable to drought, leading to reduced growth, dieback, and mortality. The urban heat island effect exacerbates these conditions by increasing temperatures within urban areas and accelerating water loss through evapotranspiration (Dale & Frank, 2022). This phenomenon is particularly concerning in the context of climate change, which intensifies heat waves and further stresses urban trees, weakening them and increasing their susceptibility to diseases and pests (Duinker et al., 2015; Ziter et al., 2019). Selecting drought-tolerant species, implementing efficient irrigation, and using mulching improve the water-holding capacity of urban soils and reduce the impact of drought (Saddle Hills County, n.d.).

Mechanical damage from construction, vehicular impacts, and improper pruning are also common in urban areas. Such injuries become entry points for pathogens, resulting in decay and structural weakness, which can significantly reduce a tree's lifespan (Krige, 2024). For example, mechanical damage has been identified as a significant threat to the urban forest in Toronto, requiring careful management and mitigation strategies like using physical barriers or fences around trees, pruning trees of concern, and post-construction soil/wound treatment (City of Toronto, 2017; Krige, 2024; Shinwary, 2021; Fraedrich, n.d.). When it comes to reducing mechanical damage, it is essential to implement protective measures, such as tree guards, and to educate the public and professionals about proper tree care practices. Regular inspections and maintenance can also help identify and address mechanical injuries before they lead to more severe issues (City of Toronto, 2017; Krige, 2024; Shinwary, 2021)

Some other overlooked stressors include artificial light and dog urine. Artificial light can disrupt the natural growth cycles of urban trees, interfering with photosynthesis and respiration. It has been shown that excessive light exposure can delay leaf drop, disrupt flowering, and reduce overall vigour, weakening trees and increasing their susceptibility to other stresses (Meng et al., 2022). Using shielded lighting, adjusting light timing, and selecting species less sensitive to light fluctuations can mitigate the effects of light pollution (Meng et al., 2022). Dog urine is an abiotic stressor linked to increasing urban population density and, thus, dog ownership. Studies have shown that though dog urine deposition and "fertilization" are localized due to their high nitrate, ammonium, and phosphorus concentrations, they have a negative impact on soils and trees. Soils impacted by dog urine also have significantly higher salt concentrations (lower osmotic potential), making it harder for trees, especially younger trees, to take up water (De Frenne, 2022). 

Strategies like increasing tree canopy cover, using reflective materials in urban design, and creating green infrastructure that cools the urban environment can be used to mitigate the impact of heat on trees. Green infrastructure solutions, such as rain gardens and permeable pavements, also help reduce heat stress (Dale & Frank, 2022; Ziter et al., 2019). These strategies benefit trees and improve overall urban livability by reducing heat and improving air quality (Dale & Frank, 2022). 

In addition, resilient species that can withstand a range of environmental conditions should be prioritized. Selecting tree species that tolerate urban conditions is crucial. For example, it has been observed that species like Ginkgo (Ginkgo biloba), Honeylocust (Gleditsia triacanthos), Oak (Quercus spp., and Elm (Ulmus spp.), as well as Kentucky Coffee-tree (Gymnocladus dioicus) and Northern Red Oak (Quercus rubra) might show higher resilience against urban stressors like drought, soil compaction, and pollution (Carol-Aristizabal, 2024; Credit Valley Conservation, 2022).

Considering the complex interactions between abiotic stresses and the health of urban trees, integrated management and planning approaches are necessary to maintain resilient urban forests. Regular monitoring and adaptive management ensure the long-term sustainability of urban forests. In addition, landscape designs combined with strategic species selection and tree planting standards can help to minimize salt leakage and soil contamination. 

Abiotic stressors on trees and tree management within such conditions are considered in urban forest management plans and actions in many Canadian cities [see chapter: Urban Forest Management Planning]. Well-planned management that includes regular maintenance activities, such as pruning, watering during dry periods, and monitoring tree health, is essential for managing the cumulative impacts of abiotic stresses. By implementing best management practices in urban forestry, Canadian cities can ensure that their urban forests continue to provide ecological, social, and economic benefits for a longtime.

Trees in urban environments face significant abiotic and climate change-related stresses, which make them particularly vulnerable to insects and diseases (Climate Atlas of Canada, n.d.). As climate change leads to warmer temperatures and drier conditions, the susceptibility of urban forests to these threats is expected to increase [see chapter: Air Quality and Climate Change]. While many native insect species contribute positively to urban biodiversity and ecosystems, some native and non-native insects can cause severe damage to urban forests. They can defoliate trees, suck sap, bore into bark, carry diseases, weaken trees, and lead to tree death and costly management consequences. 

Forest insects and diseases in Canada can be classified into three broad categories: native, alien, and invasive species (NRCan, 2023). Invasive species, whether native or alien, are species that spread beyond their known usual range and that are capable of causing environmental and/or economic damage. The mountain pine beetle, which has extended its range from British Columbia to Alberta, exemplifies a native insect behaving invasively (NRCan, 2024a). Native species outbreaks occur periodically and can be severe (e.g., spruce budworm (Choristoneura fumiferana), mountain pine beetle (Dendroctonus ponderosae)). Alien insects have been introduced into Canada and often become pests, invading new hosts and ecosystems. Notable examples are the emerald ash borer (Agrilus planipennis), which has significantly impacted populations of Ash trees (Fraxinus spp). Beetle species primarily spread Dutch Elm Disease (DED). DED, which includes fungal pathogens (Ophiostoma novo-ulmi, a more aggressive strain, and Ophiostoma ulmi), has already devastated elm trees (Ulmus spp) in Eastern North America and poses a threat to elms across Canada (Government of Saskatchewan, n.d.). 

Pests and diseases cause economic and ecological damage and affect the social fabric of communities by altering landscapes and reducing the aesthetic value of urban areas. Effective management and mitigation strategies, including monitoring, cultural practices, biological and chemical controls, public education, and promoting diversity, are essential to protect these valuable urban forests and ensure their continued contribution to the health and well-being of Canadian cities.

Insects

Historically, Canadian cities have faced significant challenges from various insects and diseases that have had profound economic and environmental impacts. The Emerald Ash Borer (EAB), first detected in Canada in 2002, is one of the most destructive pests in North America. It has killed millions of ash trees across Ontario, Quebec, and other regions, causing substantial economic losses (NRCan, 2024b) [see chapter: Economic Value and Appraisal of Trees]. For example, Windsor, Ontario had to remove over 10,000 ash trees, drastically altering the urban landscape and increasing municipal management costs (Arnberger et al., 2017). The City of Montreal has also faced severe impacts, with large-scale tree removals disrupting recreational areas and incurring high costs for tree treatment, replacement, and removal, highlighting broader social and economic impacts of pest infestations (Ville de Montreal, 2023). The economic impact of the EAB alone is expected to cost Canadian municipalities $2 billion in treatment, tree replacement, and removal over the coming decades (NRCan, 2018; Vogt, Hauer & Fischer, 2015).

The Asian Longhorned Beetle (ALB) (Anoplophora glabripennis), detected in Toronto in 2003, poses a significant threat to hardwood trees in urban areas (Haak et al., 2009). It kills trees by boring into their trunks and branches, leading to structural failure. Efforts to eradicate the beetle in Toronto have involved the removal of over 25,000 trees, affecting local biodiversity and the aesthetic value of green spaces (Wilson and Smith, 2017). These ALB populations have been successfully eradicated (NRCan, 2024a).

The Spongy Moth (Lymantria dispar) is another pest that defoliates various tree species, weakening them and making them susceptible to other stresses. In 2020, southern Ontario experienced one of the largest spongy moth outbreaks, leading to significant defoliation and stress on Oak (Quercus spp), Maple (Acer spp), and other tree species (Invasive Species Centre, 2024b). The Woolly Adelgid (Adelges tsugae), an invasive insect, threatens forests in eastern Canada and remnants of native forests in urban areas. It feeds on hemlock trees (Tsuga canadeanis ), causing them to decline and eventually die, which could have cascading effects on forest ecosystems (Dreistadt, Dahlsten & Frankie, 1990).

Diseases

The Dutch Elm Disease (DED), introduced to Canada in the mid-20th century, devastated elm populations across the east and continues to spread across the country (Government of Saskatchewan, n.d.). Winnipeg, known as the "City of Elms," has lost thousands of elms to this fungal disease. The loss of these trees has not only reduced urban canopy cover but has also affected the aesthetic and cultural value of the city (Hildahl, 1977). Chestnut Blight, caused by Cryphonectria parasitica, a fungus introduced from Asia, has eradicated native chestnut trees (genus Castanea) throughout the Carolinian zone. This has reduced biodiversity, changed forest communities, and impacted wildlife that once relied on chestnuts as a food source. Tree diseases also impact the Canadian economy, particularly in regions where these species are abundant (Invasive Species Centre, 2024a).

Although not yet widespread in Canada, Sudden Oak Death (SOD), caused by the invasive pathogen water mold (Phytophthora ramorum), poses a significant threat to Canadian urban forests. The potential introduction of SOD could lead to widespread oak tree mortality, significantly altering the landscape and biodiversity of urban forests in Canadian cities (Braddy, 2023). Another emerging threat recently detected in Ontario, Oak Wilt, is a fungal disease caused by Ceratocystic fagacearum that blocks the water-conducting vessels of oak trees, causing them to wilt and die. These diseases have the potential to cause widespread oak tree mortality, highlighting the need for thorough monitoring and rapid response strategies (Forest Pathology, 2024).

Management and Mitigation Strategies

The decline of native tree species across Canada due to pests and diseases has had many negative impacts and significant impacts on forests, biodiversity, ecological functions, and the Canadian economy. The decline of species populations like the American chestnut, black ash (Fraxainus nigra), and hemlock contributes to the loss of genetic diversity of urban forests, making them more vulnerable to future threats. Managing the impact of invasive species is costly ecologically and economically. Ecological cost is the loss of species, biodiversity, habitat, and ecological and cultural functions, while the economic cost of dealing with the impact, managing the impacts, and loss of ecological services is also significant (Crystal-Ornelas et al., 2021). For example, municipalities and conservation groups in Ontario spend approximately $50.8 million annually on managing invasive species (Invasive Species Centre, 2023). The cost of dealing with EAB's impact and management in urban streets could reach around $1.38 billion by 2035 (Hope et al., 2020). 

The management and mitigation of insect and disease infestations in Canadian urban forests require a comprehensive approach that includes monitoring, cultural practices, biological and chemical controls, public education, and promoting diversity (Hotte et al., 2015). Monitoring and Early Detection is one method that employs regular inspections and the use of traps, which are crucial for the early detection of pests and rapid intervention. This approach has been effective in managing pests like the ALB and EAB in Toronto and Montreal (NRCan, 2018; Ville to Montreal, 2023), as early detection and eradication stopped the spread of the invasive insect. The use of natural predators (biological control) and the judicious application of insecticides (chemical control) can also help manage pest populations. For example, Montreal's response to the EAB has included a combination of tree removal, biological controls, and public education to limit the spread (Les Amis de la Montagne, 2022). 

Urban forest management plans for Canadian cities have recognized invasive species issues, preventing and managing their impact. For example, the City of Calgary’s strategic management plan incorporates several invasive species strategies: early detection and response, research and development of new eradication strategies, inventorying, prevention, community outreach, and integrated weed management that uses biological, chemical and cultural control methods to eliminate or prevent priority invasive species (City of Calgary, 2020). Additionally, the plan recognizes that maintaining tree health through proper watering, mulching, pruning, and other cultural practices increases tree resilience against pests and diseases [see chapter: Tree Maintenance].

Removing and properly disposing of infected or infested trees and plant materials are vital to preventing the spread of pests and diseases. Federal quarantines and local initiatives, such as the "ash-free" zone in southwestern Ontario, have been slowing the spread of pests like the EAB (NRCan, 2018; MacFarlane and Meyer, 2005). Raising awareness about urban forest health and involving the community in monitoring efforts are also essential for effective pest and disease management. Public education campaigns in cities like Montreal and Toronto have been critical in controlling the spread of pests like the EAB and ALB (Les Amis de la Montagne, 2018). The Ontario Ministry of Agriculture, Food and Rural Affairs also emphasizes integrated pest management practices that focus on prevention and cultural methods (OMAFRA, 2012). Finally, promoting species and genetic diversity in urban forests reduces the risk of widespread damage from any single pest or disease. This strategy is important for mitigating the effects of invasive species like the spongy moth and sudden oak death, but also for other tree species and urban forest management in general (Braddy, 2023).

Invasive plant species pose a significant threat to urban forests across Canada, impacting biodiversity, ecosystem health, ecological functions and services of green spaces and natural urban areas while also causing significant economic impact. According to the 2021 national survey led by the Invasive Species Council, Canadian municipalities estimated annual expenditures on invasive plant species ranged from $95.8 million to $400 million (Vyn & Invasive Species Centre, 2022). Effective and integrated prevention and management of invasive plant species is crucial to maintaining the integrity and resilience of urban forests to ensure biodiversity conservation and a steady flow of economic and ecological benefits provided by urban forests. 

Due to the history of land use change (e.g., previously agricultural land or disturbed land converted to urban), the introduction of, and preferences for introduced plant species, urban areas tend to have numerous non-native plants, some of which are invasive. The introduced invasive species are either planted or spontaneously established across various land uses, threatening the biodiversity of natural areas. For example, some invasive plants such as Japanese knotweed (Reynoutria japonica), Garlic mustard (Alliaria petiolata), Dog-strangling vine (Vincetoxicum rossicum), European buckthorn (Rhamnus cathartica), Himalayan blackberry (Rubus armeniacus), and Tree of heaven (Ailanthus altissima) proliferate through urban areas, monopolizing natural areas while outcompeting native flora and disrupting local ecosystems and ecological functions (City of Toronto, 2013; Ministry of Forests, 2024; Ontario's Invading Species Awareness Program, n.d.; Stanley Park Ecology Society, 2013; Saskatchewan Invasive Species Council, n.d.).

Invasive plant species often alter soil biological properties (e.g., mycorrhizal properties), chemistry, and nutrient availability, which hinders the establishment of native species, promoting further expansion and establishment of invasive plants (Ehrenfeld, 2003; Kourtev et al., 2002). Invasive plants modify vegetation composition, growing conditions, and light conditions, and decrease water availability for native plants, making environments less hospitable for native species (Lamarque et al., 2011). Another risk from invasive plants involves the possibility of them hybridizing with native plants and eventually eliminating native genetic potential (Mooney & Cleland, 2001). These cumulative impacts ultimately change the composition and structure of natural vegetation in urban areas (Delavaux et al., 2023). It has been shown that non-native, invasive trees reduce the diversity of native insects and could facilitate the spread of non-native pests (Branco et al., 2019). Moreover, invasive plant species can significantly change ecosystem functions and negatively impact human health (Vila et al., 2011).

Some of the planted or self-established trees in Canadian cities are also listed as invasives and include: Black Locust (Robinia pseudoacacia), European black alder (Alnus incana), White mulberry (Morus alba), Scots pine (Pinus sylvestris), Norway maple (Acer platanoides), Manitoba maple (Acer negundo), Tree of heaven (Ailanthus altissima), Autumn olive (Elaeagnus umbellata), Japanese barberry (Berberis thunbergii), and European buckthorn (Rhamnus cathartica). However, many other invasive trees, shrubs, and grasses occur in Canadian urban areas and pose a threat to natural ecosystems. 

Managing Invasive Plant Species in Urban Forests

Invasive species management is multifaceted and includes various tools and methods ranging from policy, control, and eradication measures to public education and prevention actions. In Canada, different levels of government have introduced weed and/or invasive species control legislation prohibiting plant introduction and distribution. At the national level, provincial control measures with federal regulations can be adopted to control the spread of invasive species in Canada (Government of Canada & Environment and Climate Change Canada (ECCC), 2024; Sherman & Ontario Invasive Plant Council, 2015). For example, the government of Ontario prohibits and restricts the import, possession, transport, or release of 42 invasive species under the Invasive Species Act (Government of Ontario, 2023). Not all invasive species have the same impact; a few species cause most of the damage. In British Columbia, six invasive species alone caused an estimated $65 million in damage in 2008 (Invasive Species Council of British Columbia, 2024b). 

Invasive Plants Control

The control and eradication of invasive plant species range from mechanical and chemical techniques to burning, flooding, biological control, and other control methods. Mechanical removal methods such as hand-pulling, mowing, and cutting can effectively manage small infestations. More recently, controlled goat grazing has been used to manage invasive species in natural areas (Rathfon, 2021; City of Mississauga, 2021). 

Herbicides and other chemical controls may also be used selectively to control invasive species, mainly when mechanical methods are impractical. However, the application of these chemicals must comply with local regulations and be conducted by certified professionals (Invasive Species Centre, 2021; Wisconsin Department of Natural Resources, n.d.). Also, the use of certain chemicals to control weeds and invasive plants has been forbidden by many municipalities across Canada (The Ontario Pesticides Act, 2024; City of Vancouver, n.d.; Health Canada, 2024).

Biological control methods are also used to introduce natural predators or pathogens specific to the invasive species to manage its populations. This approach requires research and careful ecological risk assessment to avoid unintended ecological impacts (Invasive Species Centre, 2021). For example, after conducting over a decade of testing, the Canadian Food Inspection Agency, as part of a larger integrated management strategy for invasive Phragmites (Phragmites australis), approved the release of two stem-boring moths (Archanara neurica and Lenisa geminipuncta) to control the spread of this species. Phragmites is one of Canada's most disruptive invasive species (Ducks Unlimited Canada, 2024) that has been threatening wetlands' biodiversity, but has also been rapidly spreading along roads, including urban areas. However, biocontrol measures alone are not enough to eradicate invasive phragmites. They are expected to gradually reduce species dominance and habitat disturbances, allowing native plants and animals to recover (Ducks Unlimited Canada, 2024).

Early Detection and Rapid Response

Early identification and control of invasive species is another essential tool that is based on regular monitoring and community reporting of invasive plant observations. One such approach is early detection and rapid response (EDRR) of invasive species. In British Columbia, for instance, EDRR activities are conducted in partnership with the Canadian Food Inspection Agency and involve key land managers and stakeholders across B.C. and neighbouring regions (British Columbia Inter-Ministry Invasive Species Working Group (IMISWG), 2014). Moreover, invasive species monitoring and management through remote sensing, drone-based imaging, and data processing and analysis have emerged as practical solutions to map and detect large plant invasions in urban forests (Singh et al., 2024). 

Education

Educating the community about the impacts of invasive species and encouraging the use of native plants in landscaping can significantly aid in prevention and control efforts. Across Canada, different levels of government, non-profit organizations, regional groups, and conservation authorities have been educating the public and eradicating or preventing invasive plants from spreading in urban areas (Government of Alberta, 2014; Invasive Species Council of British Columbia, 2024). These groups often initiate and engage in developing invasive species strategic management plans and best management practices (BMPs), as part of urban forest management (Ontario Invasive Plant Council, 2024). Community members and the public are also actively involved in controlling invasive species and removing them from natural areas. Examples of community efforts in coordination with municipalities, NGOs, or on their own exist from the east to the west coast (Invasive Species Centre, 2024). 

Collaborative efforts between municipalities and academia and the continuous adaptation of best management practices based on current research and local conditions also enhance invasive species control effectiveness and contribute to urban forest sustainability (Sherman & Ontario Invasive Plant Council, 2015).

Municipalities have integrated invasive plant management strategies into their urban forest management plans to preserve the ecological health and resilience of urban green spaces and natural areas (City of Toronto, 2024a; Government of Alberta, 2024; Patterson, 2015). Many municipalities started prioritizing planting native and non-invasive and introduced tree species to lead by example and stop the spread of invasive species (Patterson, 2015). However, some invasive species, such as Norway maple (Acer platanoides), are still planted and produced by tree nurseries.

Forest fires in the boreal forests of Canada are a natural disturbance that drives vegetation dynamics by increasing the diversity of trees and vegetation. However, over the last few decades, the frequency, intensity, and severity of wildland fires have been increasing due to a confluence of factors. Common forestry practices of fire suppression have led to a sizable accumulation of dead wood and debris, as there are no natural fire regimes to reduce debris buildup (Stocks & Martell, 2016). The increased fuel load allows fires to reach higher into the canopy and burn much hotter. These conditions are compounded by anthropogenic climate change, which has led to drier and longer summers that create an ideal environment for intense and sustained fires. Some Canadian urban and Indigenous communities have traditionally been embedded within forested landscapes, while some new urban areas have also expanded into these areas. These urban-rural interfaces are at risk of experiencing forest fires as fire intensity and frequency increase in Canada.

While wildfires occur year-round, the fire season in Canada is generally concentrated from May to September. For Canada, 2023 was the most destructive wildfire year on record. In June 2023, more land was burned in Quebec than in the last 20 years combined (Natural Resources Canada, 2024). The impacts of severe wildfires extend beyond the loss of forests. They destroy communities, displace people, tear down buildings, and displace large groups of people from their homes. Additionally, wildfire weather and smoke can extend well beyond the wildfire area and have long-lasting human health impacts (UNDRR, 2024).

Fires can also severely impact urban forests by destroying large numbers of trees and green spaces, reducing overall tree canopy and forest diversity. Such impacts leave communities within this interface with little to no tree canopy cover. The severe reduction in canopy cover can intensify summer heat and exacerbate heat-related issues associated with urban heat islands. Tree loss in urban areas also impacts wildlife and plant species that rely on them for food and shelter, while simultaneously decreasing the aesthetic appeal and recreational value of these communities. Additionally, the sudden and large-scale tree canopy losses have long-term implications for community resilience and environmental health. The recovery process requires subsequent tree replanting and forest restoration efforts in urban areas, which can be a costly and time-consuming process.

Fire Management 

Fire management involves appropriate forest management techniques, public education, and updating landscape management plans and methods at the individual and community level. Individuals in high-risk areas can reduce fire risk to dwellings by clearing flammable materials around the home, creating fire breaks at the building scale, and incorporating fire-resistant material into building construction. Studies have shown that many buildings catch fire through embers landing on or near the property and spreading out to another adjacent dwelling (BC Wildfire Service, n.d.), and it is common for wind to carry embers hundreds of meters away (Partners in Protection, 2003). As such, maintaining a clean gutter, removing wood piles from the property, and creating a fire break between wooden structures and the house can reduce the chances of ignition. For instance, decks attached to houses and wood furniture can be sources of ignition. Choosing fire-resistant plant species, clearing low branches of adjacent trees to prevent crown fires, and clearing plant debris help to reduce the chance of fire spreading (Beverly et al., 2020). These preventative measures can reduce the risk of dwellings catching on fire and reduce fire spread through communities.

On a community or regional level, larger-scale initiatives such as conducting a wildfire assessment, identifying factors that increase the risk of wildfire in the urban area, and carrying out plans to reduce this risk can better prepare communities for the annual fire season. A review of studies in the Pacific Northwest has shown that a combination of forest thinning and burning is the most effective at decreasing fire severity (Copes-Gerbitz et al., 2022). Thinning lower branches helps to deter the upward spread of fires into the canopy and the spread of fire through the canopy. However, thinning alone has been documented to increase the severity of fires as the overall fuel load at ground level has increased; therefore, a combination of thinning and surface treatments makes the most significant difference, whether prescribed burning or pile burning, in decreasing the intensity of future fires (Davis et al., 2024). Post-treatment wildland fires are less intense and show higher tree survival rates (Davis et al., 2024). These managed landscapes are also easier for fire control personnel to traverse, leading to more effective control of wildland fires (Davis et al., 2024). Over time, treatment effectiveness declines, making long-term forest fire management crucial.

Fire and Indigenous Communities 

Over the past decades, wildfires with the most extreme intensity and spread have often happened in remote areas of Canada. As a result, smaller towns and Indigenous communities have been disproportionately impacted by wildfires. Smaller towns and Indigenous communities have fewer resources and are less likely to have a developed community wildfire plan (Copes-Gerbitz et al., 2022). Even though Indigenous communities are actively concerned about wildfire risks to wildlife, water quality, and biodiversity, unequal access to fire prevention resources is a systemic barrier that must be overcome to reduce the impact of wildfire (Copes-Gerbitz et al., 2022). Compared to larger municipal and regional districts, Indigenous groups also have a more limited social capacity and have been historically excluded from the planning process; therefore, they often cannot take advantage of government-sponsored programs. Outreach and community-centered approaches should be considered in implementing wildfire prevention plans, and traditional knowledge from Indigenous communities should be included in the discussions (Government of British Columbia, 2022).

Prescribed Burns

Indigenous people have historically used fire to manage the land and sustain their culture, values, and practices, but modern fire suppression forest management techniques have often prevented these cultural prescribed burns in many areas of Canada (Lambert, 2021; FireSmart Canada, 2022; FireSmart Canada, 2024). This absence of fire on the landscape results in a loss of biodiversity – remnants of native prairie-savannah ecosystems found in Canadian cities (City of Toronto, 2002; District of Saanich, 2023) are testimony to this. Prairie-savannah ecosystems are one of Canada's most threatened vegetation and habitat types due to land conversion and the absence of fire. Prescribed burns help to manage these ecosystems in cities and maintain their biodiversity. Controlled fires help remove dead vegetation, control invasive species, and recycle nutrients back into the soil to prompt the growth of native grasses and wildflowers. For example, with a better understanding of fire ecology, the City of Toronto introduced annual prescribed burns to maintain the native black oak savannah in one of the most iconic city parks: High Park. The practice started in 2000 and has continued every year since. The annual prescribed burn resulted in many positive ecological and social benefits, which include public education and the incorporation of traditional knowledge and practice into managing vegetation in urban areas (Martin, 2024; Prescribed Fire, n.d.). 

Importance of Equity in Urban Forestry

Urban forest equity is crucial to addressing the systemic and historical disparities of greening while supporting future environmental resilience. From a social perspective, urban forest equity is crucial to ensuring that marginalized and underserved communities receive fair investments in green spaces, that all communities have access to the health benefits of trees and greening, and experience equal opportunity to foster strong social connections, recreate, and thrive within urban green spaces. From an ecological perspective, urban forest equity is important for supporting biodiversity and overall ecosystem functioning, which improves climate resilience, provides wildlife habitat, and mitigates pollution.

Trends

The importance of tree equity issues in Canada is gaining attention locally and nationally (Watkins & Gerrish, 2018). Urban forestry conferences, action plans, management strategies, and research are more intentionally integrating equity into their work across sectors in all regions. Some key research hubs contributing to knowledge advancements are: The University of British Columbia, The University of Toronto, Carleton University, Concordia University, UQAM, and Université Laval – to name a few. Researchers at these universities focus on social, environmental, or technological (such as AI) equity considerations.  

Key knowledge includes:

• Access to tree canopy: There has been a significant shift in Canada, with more attention being paid to planting projects in underserved areas through the 2 Billion Trees program. 
• Integrating a lens of environmental justice, for example, considering how temperature regulation can mitigate health risks due to extreme heat, particularly in low-canopy, health-vulnerable communities.  
• Inclusive decision-making involving residents and ensuring their voices shape design, priorities, and practices.
• Equitable funding for tree planting and long-term maintenance to ensure disadvantaged areas are not overburdened with tree care post-planting. 
• Community engagement to provide education, jobs, and training opportunities to foster long-term stewardship: A critical part of this is recognizing the role of Indigenous knowledge and Indigenous-led greening in community engagement to achieve equitable green spaces in planning and operations; in addition, increasing diverse group representation in urban forestry career pathways to support recognitional justice – they need to see themselves in the profiling of the field to feel welcome (Vabi & Konijnendijk, 2021)
• Lastly, there is emerging interest in credentials for urban forest professionals to support the "legitimization" of their role and skillsets (O'Herrin et al., 2023). 

Defining Equity in Urban Forestry

The common definitions of urban forest equity in Canada center on the fair distribution of tree-related benefits, particularly in marginalized or underserved areas. Urban forest equity strives to ensure that all residents, regardless of income, race, or location, have equal access to the environmental, social, and economic benefits that urban trees provide.

Emerging research has shown that equity in urban forests goes beyond access to green space and should be broader to address three areas: distributional, recognitional, and procedural equity and/or justice (Nesbitt et al., 2019). These are not mutually exclusive. Distributional equity refers to the fair spread of urban forest resources and benefits across communities. Recognitional equity acknowledges and respects diverse identities, histories, and perspectives within communities. It is about understanding who lives in a community: where they come from, their unique needs, and the barriers they face in accessing green spaces. Lastly, procedural equity focuses on the fairness of decision-making processes, ensuring that all community members have a voice in urban forestry projects and that their voices influence outcomes.

Urban Tree Canopy Distribution and Access to Green Space 

Urban forests are the first and only experience of nature for many, and these forests shape the experiences of nature for millions of Canadian residents, making access to urban green spaces a crucial topic in urban forest strategies; a national poll indicates that 95% of Canadians agree that access to green spaces is important to their quality of life (Environics Research, 2017). However, not all urban residents benefit equitably from the ecological services that urban forests and green spaces provide. 

To date, urban forests have been distributed inequitably in Canadian cities. On average, lower-income neighbourhoods (below 50% of median household incomes) and marginalized neighbourhoods (disempowered or lacking the capacity to participate and gain full respect in society) have less green space and canopy cover than wealthier, predominantly white neighbourhoods (GoC 2022; Public Health Ontario, 2021; Cusick, 2021). In many Canadian cities, neighbourhoods with lower-income households and larger Black, Indigenous, and people of colour (BIPOC) populations were found to have up to 20-30% less canopy cover (Wittingham et al. 2022). When considering the physical and environmental health benefits that urban forests provide, the disparities in tree canopy distribution and inequitable access to these benefits raise a question of social equity (Schell et al., 2020). Moreover, in areas suffering from poverty and racialization, women have been found to use green spaces less frequently if they perceive them to be 'unsafe' due to poor lighting, maintenance, or cleanliness (Braçe, Garrido-Cumbrera & Correa-Fernández, 2021). 

These findings show that low-income neighbourhoods, marginalized communities, racialized groups, and women do not equitably enjoy the benefits provided by quality green spaces. Addressing these issues and the equitable distribution of tree canopy and environmental benefits is essential for building just and sustainable treed urban communities and a healthy society. Community well-being, social inclusion, gender equity, environmental health, and climate resilience in racialized and low-income neighbourhoods will all benefit from equitable and strategic urban forest planning (Bikomeye et al., 2021). 

Canada is not immune to the issues of urban forest equity in its cities and towns. For example, in major cities such as Toronto, Ottawa, Montreal, Vancouver, Calgary, Surrey, and Quebec City, the lower tree canopy cover has a significant negative correlation with poverty and racialization (Wittingham et al. 2022). In an effort to address the problem, municipalities like the cities of Ottawa and Toronto have made equitable access to urban forests a guiding principle in their urban forest plans and strategies (Engage Ottawa, 2024). However, despite the efforts, urban forest planning (meaning their development and planning) and tree canopy equality implementation in Canadian cities are still lacking, and equity strategies or engagement plans to assist specific to marginalized communities still have a minor impact (Mullenix, 2022).

Immigration and Multicultural Considerations

How Canadian citizens feel about their urban forest matters in terms of what they receive and benefit from, and whether and how they are willing to engage in urban forest conservation and management. Researchers often measure residents' attitudes toward green spaces through public surveys, and the information obtained can help municipalities better manage their urban forests (Jennings et al., 2016). However, people living in different regions may have different attitudes and preferences related to urban forests or may face unique barriers to their ability to participate in public referendums, surveys, and engagement opportunities (Avolio et al., 2015). Language barriers to new immigrants and people of various cultures can go unconsidered when municipalities conduct public surveys or hold open public participatory meetings (Ornelas Van Horne et al., 2023). 

Additionally, low-income communities may lack time, funds, and access to the technology required to participate in events- time off work, childcare, internet, and computers/smartphones are more accessible in higher-income communities, but to many low-income Canadians, these things are luxuries that prevent participation (Chianelli, 2019). Meaningful public discourse cannot be achieved without considering barriers to engagement when discussing urban planning and environmental issues, especially in marginalized communities where sustainable and equitable planning is that much more significant. 

Moreover, participation and inclusion of new Canadians, BIPOC, and multicultural individuals are also vital to building equitable urban forestry. Due to its far-reaching benefits, urban forestry involves multidisciplinary teams with diverse skills and knowledge. Foresters, urban planners, landscape architects, arborists, scientists, and community leaders help create healthy and sustainable urban forests, and this multidisciplinary field can greatly benefit from the inclusion of people from diverse backgrounds and experiences. 

Labour and Gender Equity

Labour and gender equity are also crucial issues in the fields of urban forestry and arboriculture in Canada, where both sectors have traditionally been male-dominated. Labour equity focuses on ensuring fair representation, remuneration, and career advancement opportunities for individuals from all backgrounds. This issue is particularly important as the urban forestry profession seeks to diversify its workforce and attract more varied talent. Gender equity, on the other hand, specifically addresses the persistent underrepresentation of women in urban forestry and arboriculture, where women often occupy lower-level roles and encounter obstacles to career advancement due to systemic biases and discrimination (Bardekjian et al., 2019; Kuhns et al., 2004).

Recent efforts, such as mentorship/training programs and workshops aimed at reducing barriers to entry, are working to create more inclusive environments for women and other underrepresented groups in the field of urban forestry (City of Toronto, 2023; FSC, 2022). The biennial Canadian Urban Forest Conference, coordinated by Tree Canada in partnership with a host city, along with initiatives like Free to Grow, Women in Forestry, and Women in Wood networks, are helping to bring professionals together and advocate for a more equitable, diverse, and inclusive workforce (Free to Grow in Forestry, 2021; Women in Forestry, n.d.; Women in Wood, 2017). These initiatives are critical as urban forests play an increasingly vital role in the climate resilience and social well-being of Canadian cities, necessitating a broader range of voices and perspectives for their sustainable management. 

As the field of urban forestry continues to evolve, addressing labour and gender equity within the profession will be essential for ensuring that all professionals, regardless of gender or background, can contribute meaningfully to the design, planning, and management of urban forests (Bardekjian, 2016; Bardekjian et al., 2019). 

Solutions and Strategies

An equity-based approach to urban greening should be adopted to ensure that Canadian cities can work towards canopy cover goals without propagating further social and economic disparity (Angelo, MacFarlane, Sirigotis & Millard-Ball, 2022; Bassett, 2024; Puric-Mladenovic, 2024). Increasing canopy cover/tree planting goals are part of many Canadian cities' urban forest management plans, and urban greening in low-income/racialized areas presents an opportunity to address two issues at once. However, increasing canopy cover in underserved areas faces some challenges, such as a lack of funding, the absence of a planning process that values trees and long-term tree survival, and weak public engagement with communities that need trees the most (Mullinex 2022). Additionally, a lack of physical space to plant trees and sometimes environmental contaminants can lower chances of tree survival (Danford et al., 2014; Wattenhofer and Johnson, 2021).

Where to Start

There are several tools and methods that already exist for addressing inequality in urban forestry. For example, Statistics Canada created a tool to address the need to understand gentrification in a Canadian context. The tool is called GENUINE, which stands for Gentrification, Urban Interventions, and Equity (see Team INTERACT, 2016), and it automatically populates maps for several Canadian cities across four separate measures (Firth et al., 2021). In addition to assessing what is already there through available tools, there are recognition and certification programs such as the Arbor Day Foundation's Tree Cities of the World (TCOW) program and the Sustainable Forestry Initiative's (SFI) Urban and Community Forestry standards that offer structured guidelines and criteria for successful management. The first step is identifying a community’s equity-related goals; once goals are established, these kinds of tools can be helpful, staged approaches for planning and review. 

Funding

To address the lack of funding for urban forestry activities, some municipalities, including Toronto and Winnipeg, support urban forestry grants and incentive programs (City of Toronto, 2021). Integrating urban forestry funding into yearly municipal budget planning is another way to ensure funding allocation to urban forest management. Alternatively, federal funding programs such as the 2 Billion Trees Program (GoC, 2023) and the Forest Innovation Program (NRCan, 2023) should work to enhance equitable access to urban forests and sustainable management of urban green spaces, while the Natural Infrastructure Fund (GoC, 2024) should improve natural infrastructure in underserved communities, which can reduce heat stress, limit extreme weather damage, and support stormwater management (Wittingham et al., 2021). Additionally, the federal government should increase funding availability for municipalities to protect and maintain existing trees and expand urban tree canopy equitably and fairly. One success story is the Growing Canada's Community Canopies (GCCC) program delivered in partnership between Tree Canada and the Federation of Canadian Municipalities (FCM), where there are two broad streams of funding: the first is for increasing canopy and getting trees planted, the second is for capacity building in all other areas that are required for urban forest sustainability. 

Planning

Planning processes need to prioritize equity by using evidence-based decision-making informed by tools such as current tree inventories and the Tree Equity Index, income data, and immigration and BIPOC data (Ordonez et al., 2024). Additionally, municipalities must assess current canopy cover data compared to canopy goals while supplementing urban greening decisions by identifying areas with lower canopy cover, which have low Tree Equity Index values (Fleming and Steenberg, 2023). Integrated and intersectional planning processes for urban trees should be created, with adequate municipal and provincial funding allocation towards increasing urban tree cover equity across municipalities in racialized and marginalized communities (Jennings et al., 2019). Furthermore, these planned urban forests/green spaces must be accessible (within 300m of residences) and be of good enough quality to sufficiently supply benefits to underserved communities (Wittingham et al. 2022). 

Engagement

Finally, fostering public engagement by building stakeholder relationships between governments, academia, industry, community organizations, practitioners, and citizens is vital to sustainable and equitable urban forest management (Campbell, Svendsen, Johnson & Plitt, 2022). Community members should be engaged from the beginning stages of planning processes and consulted throughout the planning and execution process. Nurturing ongoing relationships with existing neighbourhood associations and stewardship programs (or creating them where they do not exist) is an important step in starting discourse with residents. Consulting community leaders on equitable and accessible suggestions for building community interest and participation should be part of the beginning stages of public engagement strategies. Outreach efforts should be the predominant recipients of allotted urban greening budgets for target neighbourhoods in the beginning stages to ensure consideration of diverse perspectives, proper community consultation, and meaningful community engagement. Relationship-building with the people impacted by urban forest inequity can help make sure community needs are considered and responded to while building programs that are sustainable, successful, and robust (Wittingham, 2022).