Urban forests are not merely green amenities; they support critical ecosystem functioning and services vital for healthy, resilient cities. Recognising urban forests as core infrastructure is essential to reversing the loss of mature trees, preserving biodiversity, and maintaining liveability amid increasing climate and environmental pressures. Although the benefits of urban forests for climate resilience, biodiversity, and public health are broadly acknowledged, policies to protect and enhance these vital ecosystems are often limited, underfunded, and inadequately enforced. As mature canopy loss today takes decades to be replaced (if ever), immediate and sustained investment is crucial to safeguard urban forests. This urgency reveals four interconnected gaps in current urban forest management and stewardship. First, urban forests require recognition, investment, and maintenance as essential infrastructure contributing to urban resilience, including biodiversity support, and to maximise the delivery of key ecosystem services such as cooling and carbon sequestration. Second, equitable access to greenspaces across all communities must be ensured to redress long-standing social and environmental injustices. Third, integrating urban forests into broader climate and biodiversity governance frameworks is critical to mainstreaming their management and protection. Lastly, resilience must be strengthened through evidence-based management practices responsive to evolving environmental changes and social contexts. These priorities must be complemented with strong legal protections, rigorous enforcement of legislation against illegal tree removal, and robust community engagement supported by integrated urban planning and improved monitoring. Without these, the ecological, social, and economic benefits provided by urban forests will remain threatened. By reframing urban forests as essential living infrastructure embedded in legal, financial, and planning frameworks, cities can become cooler, healthier, more biodiverse, and socially just. This framework offers timely guidance for policymakers to prioritise urban forests within climate resilience and sustainability strategies, securing benefits for current and future generations.

Urban tree cover (UTC) is a commonly used metric in policy and management activities, including urban forest resources assessment, equity and distribution, and ecosystem services modelling. Despite the well-established benefits associated with urban tree canopy, declining tree cover has catalysed many cities into setting UTC targets. In this short communication, we used an assessment of UTC targets set by 57 cities worldwide to discuss the merits and drawbacks of setting UTC targets and to inform recommendations for setting effective UTC targets. We found that UTC targets range in ambition, varying between 4 % and 50 %. To meet these targets, cities would have to increase their current UTC by between 0.47 and 23.3 percentage points within stated timelines of between 3 and 51 years. We found that cities with lower current UTC set ambitious targets, requiring relatively large annual increases in canopy cover. Moreover, cities in xeric or dry biomes set lower targets (< 20 %) than cities in temperate or tropical biomes (> 25 %). We found that setting UTC targets can provide a range of benefits, but achieving a UTC target at the expense of other indicators of urban forest structure and quality poses risks. We reflect on pathways to set specific, measurable, achievable, resourced, and time-bound UTC targets, while acknowledging the associated issues. This exploration of UTC targets will help ensure that UTC remains a useful metric for urban forest management and planning.

The application of ecosystem services (ES) and related ideas is believed to improve urban environmental planning processes and policy, but the uptake of ES ideas in urban planning is limited. The purpose of this research was to understand the tactics of policy entrepreneurs (PEs) to promote ES and related ideas in urban planning. PEs are persistent and resourceful public policy actors who advocate for ideas and policy proposals they favor with the goal of producing policy change. Research participants employed in urban planning in three Canadian cities were interviewed about their experiences in applying ES and related ideas. After narrowing the criteria for participation in the analysis for this research project, we identified 11 PEs among the participants who were applying a range of tactics to overcome resistance to policy change. Their tactics included framing issues (such as those presented by climate change) with ES to connect with politicians' concerns and convening cross-disciplinary discussions to bridge divides. We argue that PEs may play important roles in advancing the use of ES and meeting sustainability objectives in urban planning. Recommendations for research include evaluating the success of PEs in policy change and expanding the under-researched area of policy entrepreneurship in planning, including case study research to understand the role of organizational context in enabling policy entrepreneurship.

Urban forest management plans (UFMPs) are a key element of the planning process in urban forestry. While we can learn about management intentions by analyzing the content of UFMPs, less is known about happens after plan implementation has begun. This study fills this gap by exploring how is UFMP implementation advancing. To do this we asked municipal urban forest professionals working in Canadian municipalities with a UFMP to answer an online survey. The survey: 1) characterized UFMP development; 2) assessed the level of achievement of UFMP objectives; 3) assessed which municipal characteristics led to UFMP objective achievement; and 4) assessed professional views on the outcomes of having a UFMP. Based on n = 118 responses across Canada, we found that UFMPs have been published frequently in the last 20 years, with a peak during the period 2010-2014. On average, and as shared by the respondents, the level of achievement of UFMP objectives was over 50 %, indicating good progress in UFMP implementation. We found no statistically significant differences in the level of UFMP objective achievement by type of city or language of community (English/French), among other factors. There was a consensus among professionals that increasing financial resources for urban forests was an expected outcome of having an UFMP, although there were also diverse and complementary views about the outcome of a UFMPs. A key finding was that climate change objectives are not being implemented or included in UFMPs at high levels. While focused on Canadian cities, this study also provides guidelines on how to assess UFMP implementation across case studies, as well as insights regarding the management objectives that are being overlooked in plan implementation. This may enable future work by researchers and practitioners working in fields related to nature-based solutions, green infrastructure, urban climate adaptation, and sustainable cities worldwide.

Urban forests are a critical element of urban environmental planning. Greater awareness of the ecosystem services provided by urban forests over the last two decades has led to an increased interest in improving urban forest management. In Canada, the conditions of management are usually articulated by a municipal government in an urban forest management plan (UFMP). This study responds to previous studies on the content of Canadian UFMPs to provide a more comprehensive and updated comparison of UFMPs across Canada. While previous research has examined the content of UFMPs at a moment in time, and often when far fewer plans existed, in this study we consider changes in content over time and the influence of the social-ecological characteristics of municipalities on this content. We combined quantitative and qualitative content analyses, including topic modelling text analysis algorithms and interpretative thematic coding, to extract content, in the form of topics or themes, from 74 UFMPs. We assessed the distribution of these topics and themes by year of publication, and the influence of social-ecological characteristics upon this distribution using standard correlation and means differences analysis procedures. We found that Canadian UFMPs contain a broad number of themes and topics but are dominated by ideas referring to increasing tree abundance. Comparatively less attention is being paid to climate change and community stewardship. Mentions of increasing tree abundance and climate change rose over time. There was also a greater mention of administration, community education, and increasing tree abundance in smaller municipalities. Canadian municipalities may be well positioned to increase the abundance of urban forests given current management conditions. While abundance itself is beneficial, increasing abundance without addressing issues related to biodiversity, vulnerability of urban forests to climate change, and community stewardship, is a management trade-off that could, for example, increase abundance in the short term, but increase vulnerability in the long term. While focused on Canadian cities, this study also provides guidelines for possible cross-country comparisons and reflections on how UFMPs can be powerful management and planning tools for a climate-resilient and sustainable future.

Governments increasingly collaborate with residents and nongovernment organizations (NGOs) in urban forest management because of the underlying belief that these groups improve the delivery of local forest services. However, in practice, the successes, challenges, and outcomes vary drastically by collaborative arrangement; solely documenting positive outcomes in NGO-government collaborations may hinder the ability to mitigate their associated downsides rather than biasing collaborative behaviours towards success. This study draws on the experiences of urban forest professionals across nine Canadian cities who have participated in or observed NGOs and local governments engage in collaborative urban forest management. We employed semi-structured interviews with 32 participants from three groups: leaders of NGOs, municipal government officials, and urban forest experts who have observed the two parties interact. Our results demonstrate that the addition of NGOs in municipal forest management is associated with positive outcomes and the characteristics of relationships, individual personnel, and community support contribute to their success. We also characterize the barriers that collaborators are tasked with navigating in order to achieve positive outcomes, including high employee turnover, siloed departments, competing priorities, shifting politics, and precarious funding and contracts. Our recommendations for successful NGO-government collaborations include arming stakeholders with a thorough knowledge of civic processes, diversifying political relationships, fostering “champions” among a greater number of involved parties, and participating in longer-term contracts and funding agreements. Further, involved parties should ensure they work towards the equitable distribution of the benefits and outputs of urban forest collaborations. Moving forward, because of the insular nature of NGO-government collaborations and a low capacity among NGOs to share the outputs of these collaborations, we recommend researchers continue to study the successes and shortcomings under varying governance arrangements so that groups may benchmark their collaborative activities against others and determine the most effective means of participating in co-management.

While forest management commonly seeks to increase carbon (C) capture and sequestration, in some settings, a high density of C storage may be detrimental to other land uses and ecosystem services. We study a forested, drinking-water-supply watershed to determine the effects of forest management on C storage with the implicit understanding that greater storage of C will lead to increased quantity of carbon exported hydrologically into a source-water reservoir. Using a custom implementation of CBM-CFS3, a Canadian model to simulate C transformations and movement in forested systems, and a custom forest disturbance and management model, we simulate various management scenarios and their C outcomes. The largest forest C pool, mineral soils, is very slow to change and manipulating DOC export through this pool would likely not be feasible within human management timescales. Other pools, in which C has lower residence time and from which C is more readily mobilized, are a more promising area for future research into hydrologic DOC export under varying management regimes. Our findings indicate that management activities can serve to reduce forest C storage, but further research is required to connect these outcomes to hydrologic export.

Application of the ecosystem services (ES) concept in urban planning has potential for improving environmental and human health outcomes in cities. We aimed to narrow an identified ES implementation gap by identifying the criteria for the practical fit of the ES concept in urban planning. We found that local relevance and adaptability within current planning approaches were core criteria for practical fit. If not met immediately, these criteria may be met over time through policy entrepreneurship. Further research in different locations and planning systems would increase understanding of the enabling factors for applying ES in urban planning.

During a time of rapid urban growth and development, it is becoming ever more important to monitor the carbon fluxes of our cities. Unlike Canada's commercially managed forests that have a long history of inventory and modelling tools, there is both a lack of coordinated data and considerable uncertainty on assessment procedures for urban forest carbon. Nonetheless, independent studies have been carried out across Canada. To improve upon Canada's federal government reporting on carbon storage and sequestration by urban forests, this study builds on existing data to develop an updated assessment of carbon storage and sequestration for Canada's urban forests. Using canopy cover estimates derived from ortho-imagery and satellite imagery ranging from 2008 to 2012 and field-based urban forest inventory and assessment data from 16 Canadian cities and one US city, this study found that Canadian urban forests store approximately 27,297.8 kt C (- 37%, + 45%) in above and belowground biomass and sequester approximately 1497.7 kt C year-1 (- 26%, + 28%). In comparison with the previous national assessment of urban forest carbon, this study suggested that in urban areas carbon storage has been overestimated and carbon sequestration has been underestimated. Maximizing urban forest carbon sinks will contribute to Canada's mitigation efforts and, while being a smaller carbon sink compared to commercial forests, will also provide important ecosystem services and co-benefits to approximately 83% of Canadian people.

Urban forests are being threatened by rapid urbanization, biodiversity crises, and climate variability. In response, governments are increasingly collaborating with the public for solutions to these mounting challenges. Non-governmental organizations (NGOs) are dominant players in these collaborations because of their ability to supplement governments' expertize and resources and bring social and ecological issues to the forefront of civic agendas. Despite their growing visibility in urban forest management, there is a lack of attention directed to the forms and range of NGO relationships. This study focuses on addressing this gap and examining collaborations between local governments and NGOs in urban forest programming by characterizing their components including mandates, relationship ties, accountability, resource exchange, and power dynamics. We collected data using semi-structured interviews with three groups: leaders of NGOs, municipal government officials in an urban forest or public works departments, and urban-forest experts who have observed their interactions. The participants represent 32 individuals in nine Canadian cities. Our results indicate that NGO-government collaborations have relational ties and accountability processes that are both formal and informal in nature. Formality in collaborations is often associated with the amount of funding, proximity to government, or size of the NGO. In addition, our findings suggest that NGOs present an opportunity for local governments to supplement their resources and capacity. While the strength and formality of collaborations may be a product of NGO size and budgets, public servants should not hesitate to engage smaller, grassroots NGOs to realize their public service mandates. Characterizing the components of these governance processes provides a benchmark for practitioners participating in similar public-civic interactions and arms them with the knowledge to navigate collaborative decision-making.

Forest bioenergy production can represent a renewable energy supply while benefiting the forest sector. However, greenhouse gas (GHG) reductions are often not immediate. The point of carbon parity where bioenergy starts delivering GHG benefits may be years to decades in the future. This study examined the life-cycle emissions associated with bioenergy production at combined heat-and-power (CHP) projects in Nova Scotia, Canada. We examined the effects and sensitivities of different feedstock mixes of chips from harvested roundwood and mill residues, the implementation of intensive and extensive silviculture strategies, and different market/supply-chain assumptions around additionality and product substitution. We found contrasting GHG outcomes for bioenergy, depending largely on additionality assumptions and biomass type. When primary biomass (roundwood) was used as the feedstock type, carbon parity was achieved within four to nine years when pulp and paper products were substituted, whereas carbon parity was achieved in 86–100 years or longer when biomass harvests were additional. Net GHG benefits were achieved in 10 years with the use of secondary biomass (mill residues) as the bioenergy feedstock, although they were delayed when at lower energy conversion efficiencies. Adoption of more intensive silvicultural practices (plantations) reduced the time to carbon parity because of increased yields, although uncertainties in long-term soil carbon storage exist. Study Implications: Our analysis shows that the use of forest biomass in local CHP facilities can deliver GHG benefits in the short term but there is substantial variability. Carbon parity times were the longest with the use of additional primary biomass feedstocks (i.e., roundwood) but were substantially reduced when biomass harvests substituted harvests for pulp and paper products and when secondary biomass (i.e., mill residues) was used. This study highlights the nuance of different forest management dimensions (e.g., silviculture) while also presenting novel findings on the importance of assumptions around biomass harvesting being additional to current practices or a substitution for declines in traditional forest products.

Urban forestry, as the name implies, is a branch of forestry that deals with trees and woodlands in urban areas. Practice in urban forestry may have its foundations in the nineteenth century, but the moniker of urban forestry launched in earnest in the 1970s largely through the contributions of Eric Jorgensen, a professor at the University of Guelph on Ontario, Canada. Urban forestry combines long traditions of science and management in the fields of arboriculture (management of individual trees), silviculture (management of stands of trees), and forestry (management of larger woodlands comprised of many stands). Urban forestry, according to Jorgensen (see Konijnendijk, et al. 2006, cited under Definitions) is “a specialized branch of forestry and has as 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” (p. 95). This bibliography concentrates on the ecology of urban forests. Given that ecology is the study of organisms and their relationships with the biotic and abiotic environments, one instantly recognizes the fundamental ecological nature upon which urban-forest studies must rest. No trees in the urban ecosystem—whether in the heart of downtown or in the peri-urban outskirts of the town or city, or indeed anywhere between—escape the influence of humans, especially their built infrastructure. So urban forestry as a science and practice cannot help but rest firmly on the foundation of urban forest ecology. However, scoping this domain of science is fraught with pitfalls because the boundaries are unclear, broad, and porous. Much of forest ecology in general pertains to all forests, not just hinterland forests nor timber-producing forests. Equally complicating the scoping problem are the numerous intense relationships between people and trees which justify the notion that urban forests are best understood as social-ecological systems with vital economic and technical dimensions. Hearty thanks to K. E. Turner and C. Ordóñez Barona for assistance in identifying relevant literature, and to an anonymous reviewer for revisions suggestions.

Old-growth forests are both rare and special ecosystems across most of the world. Policies to protect and possibly enhance and increase them are plentiful and diverse across nations and sub-national jurisdictions. Nova Scotia has had a policy on conservation of old-growth forests on public lands in the province since 1999. The second such policy dated 2012 was recently replaced by a revised policy in 2022. After presenting knowledge based on selected scientific literature about old-growth forests in Nova Scotia, the paper describes the improvements made in the 2022 policy. These include: (a) a more-nuanced set of operational definitions; (b) a commitment to protect all old-growth forest on public lands, whether currently identified or not; (c) robust replacement provisions in the rare event that the provincial government chooses to allow provincially significant infrastructure to be built on public land supporting old-growth forest; and (d) a renewed commitment to work with private landowners on their aspirations to conserve old-growth forest. The new pol-icy, adopted in August 2022, also contains a commitment to a public review and possible renewal by August 2027.

Ecosystem services (ES) researchers have recognized the important role of urban planning decisions in influencing the quantity and distribution of ES in cities. However, knowledge about ES among planners is still modest, and more research is needed about planners' experiences with ES. For this qualitative study, interviews and focus groups were conducted with actors with roles in urban planning in three Canadian cities. The aim was to understand participants' knowledge of ES and how they use it. These early adopters were creative, practical, and politically astute in using ES ideas, rhetoric, and tools to build the case for natural urban ecosystems. ES was used in multiple and intersecting ways for awareness-raising, to justify the protection and restoration of natural ecosystems, to provide direction to plans, and to support and supplement existing planning approaches. The strategic use of ES was notable. As a boundary object, ES helped to bridge perspectives and to integrate policies. The ability of ES to facilitate policy coordination is promising. Further research on the effectiveness of ES to improve urban policy is needed.

Urban trees provide people with a range of ecosystem services. Trees planted along streets have been a large focus of urban forest research and practice, and municipalities invest significant resources in their survival. However, the optimal spacing of street trees is not addressed in the scientific literature, and existing municipal street tree spacing standards are highly variable and poorly enforced. In this study, we examine variability in crown shape and size for street trees to test for possible interaction effects at closer spacings. We measured variability in crown diameters both parallel and perpendicular to street tree rows to test whether changes in crown dimensions can be explained by interaction effects with neighbouring trees, and whether crown interactions lead to a reduction in total crown projection area (i.e., canopy cover). We measured the crown dimensions and diameter at breast height of 1,338 street trees in Halifax, Canada. We used two-way analysis of variance to test whether crown shape and crown projection area were affected by crown interactions and spacing. We found that the effect of narrower spacing and interactions (i.e., crowns touching/overlapping) among trees translated to crowns extending away from the direction of interaction. We also found that these changing crown dimensions were associated with increases in canopy cover. Urban forest ecosystems are a vital resource for the increasingly urban population. There is a need for empirical research on spacing standards and practices that investigate their influence on the supply of ecosystem services, such as stormwater retention, air pollution removal, and cooling.

Frameworks of ecosystem services (ES) are promoted as a new and important way to recognize, understand, and account for nature's benefits. We questioned assertions of the novelty of ES ideas and conducted a comparative analysis of approaches in planning, landscape architecture, and sustainable forest management against the Millennium Ecosystem Assessment ES framework. We conclude that the newer Millennium Ecosystem Assessment ES framing may assist planners in connecting local land-use change to human well-being, assessing trade-offs, and accounting for future uncertainty. Analogous approaches such as sustainable forest management offer practical insights, for example, about gauging, guiding, and reporting on sustainable use of ecosystems. We encourage environmental planners to engage with ES researchers to develop the approach and advance planning practice.

Two forest soil B-horizons were amended with alkaline-treated biosolids (ATB), powdered agricultural lime, and wood fly ash under controlled conditions to compare initial ion availabilities over a 10-week period. ATB was most effective in supplying available Ca2+but least effective in supplying available Mg2+, for which lime was most effective. Availability of K+and SO42–-S was greatest in fly ash amended soils because of high K and S loading rates and the high electrical conductivity of this amendment. Mineral N (NO3–-N + NH4+-N) availability increased in ATB amended soils, stayed the same in lime amended soils, and decreased in fly ash amended soils. Availability of PO43–-P was low in all soils but slightly enhanced in ATB amended soils. Fluxes of Cu2+, Pb2+, Zn2+, and Mn2+in amended soils generally decreased over time in association with increased soil pH. Fluxes of Cd2+were not affected by any treatment. Results suggest that ATB is equally as effective as or more effective than lime and fly ash at immediately supplying Ca2+, but less effective at supplying Mg2+because of low inputs and cation competition. This suggests that ATB amendments could be an alternative means of quickly adding available Ca2+to Ca-depleted forest soils as long as potential impacts on other nutrient base cations are considered.