Corinne G. Bassett

Urban forests are multifunctional social-ecological systems that can contribute to both climate change mitigation and biodiversity conservation. However, management of urban forests for these objectives are often studied independently. Knowing which measures can be used to assess multiple objectives could enable integrated monitoring efforts and subsequently increase potentials for synergies in management. We compared the use of forest composition metrics in studies focused on carbon storage ( n = 109) and avian diversity ( n = 158) extracted from a published systematic literature map. Through qualitative content analysis, we developed a standardized set of 24 urban forest composition metrics spanning size, taxonomy, structure, tree characteristics, and presence of vegetation layer types. Analysis assessed frequency and co-occurrence of metrics for research assessing carbon or avian outcomes. Carbon-focused studies were dominated by a smaller and more restricted set of variables, with tree species composition and diameter measured in over 90% of studies. In contrast, avian studies used a broader and specialized suite of metrics, emphasizing different types of vegetation layers and diverse habitat features such as shrubs, cavities, and fruit resources. Co-occurrence analysis revealed tightly clustered measurement frameworks in carbon studies and somewhat more diffuse patterns in avian research. These results highlight how the same measures of urban forest composition have been and can be used to assess both avian and carbon management outcomes. Overlaps and gaps identified places where alignment in urban forest monitoring could improve the capacity to manage for multiple outcomes.

Urban forests support wildlife populations across North America and the world. Yet, challenges remain for research and practice to integrate wildlife habitat as a core component of the myriad objectives that urban foresters manage. Ecosystem services have been adopted as a dominant paradigm in urban forestry for both advocacy and management, yet accounting for contributions to wildlife habitat does not fit squarely within typical ecosystem service frameworks. The i-Tree program, a suite of urban forest ecosystem service models and tools developed by the US Forest Service, presented an opportunity to link widely used urban forest assessment field protocols with indicators of suitable habitat. In this reflection piece, we demonstrate how the i-Tree Wildlife project assessed whether urban forest structural assessment methods could be applied to assess wildlife habitat provision, operationalizing the fundamental question “How do urban forests support wildlife?” We describe the development process for integrating bird habitat suitability models for 12 species present in the northeastern US, ten native and two non-native birds, into the flagship i-Tree Eco tool. We offer reflections, challenges, and opportunities from this process. Ultimately, the improvement of ecosystem assessment tools like i-Tree can assist practitioners who aim to manage healthy and productive urban forests that benefit people and wildlife.

Background: For the past 20 years, approximately twice as many trees were removed annually from urban areas in the USA as were harvested annually from the US National Forest System. Yet, most of this wood is treated as waste instead of as a valuable resource to generate economic growth and sustainable cities. Residential landowners are key actors in the establishment of local urban wood economies as both sources of material and users of urban wood products, yet they remain a difficult to reach group compared with others, such as tree care companies, mill operators, and public landowners. Methods: We analyze a representative survey of urban residential landowners in 6 United States cities. We assess (1) status of participation in urban wood systems; and (2) interest in and perceived importance of urban wood products. Results: Overall, 15% of residential landowners reported purchasing or acquiring urban wood products in the past. Landowners were more likely to purchase—and were more interested in—lower value products like wood chips and compost than higher value products like lumber or furniture. Private sector actors, like landscaping and tree care companies, and social sources, like friends and family, were more often recognized as sources of trusted information for tree care advice than local or state government and nonprofit organizations. Conclusions: We present baseline results of, to our knowledge, the largest survey of urban wood perceptions and practices to date, which indicate a substantial group of landowners already engaged in urban wood economies, and discuss potential avenues to activate future participation.

Cities increasingly hope to mobilize nature-based solutions in urban sustainability planning because of their wide-ranging ecosystem services. In this critical moment, where failure due to poor implementation could lead policymakers to turn away from nature-based solutions, we investigate the case of urban forestry and ask: how do strategic-level sustainability goals influences site-level decision-making? We conducted semi-structured interviews with 20 urban foresters leading advanced programs at municipalities with adopted sustainability goals, framed as ecosystem services, across the US and Canada. Day-to-day, site-level decision-making focused on advancing a “more, bigger trees” paradigm with the justification that this would deliver increased ecosystem services in a general sense and thus contribute to city goals. Our analysis and results suggest that urban foresters are more guided by a shared sense of the greater purpose of their work to serve urban communities than city plans, which yields actions usually aligning but sometimes conflicting with specific strategic-level goals. Graphical abstract

City leaders are setting ambitious plans to achieve critical urban sustainability goals such as reducing urban heat, mitigating flooding during storms, and conserving biodiversity, and increasingly rely on urban forests as a key nature‐based solution to such challenges. Current paradigms of urban forest management typically prioritize goals like increasing tree canopy cover that are often viewed as proxies for increased ecosystem service provision, in a general sense. However, urban foresters, the professionals with responsibility to manage urban forests, are increasingly faced with the complex challenge of managing for new goals related to ecosystem services, biodiversity, or people–nature relationships, as cities increasingly set goals centered on such outcomes, without robust guidelines to follow. We ask: How can urban foresters align their street tree management actions with specific urban sustainability goals? We conducted a structured expert elicitation of urban forest professionals in three cities: Vancouver, British Columbia, Canada; Honolulu, Hawaiʻi, United States; and Washington, DC, United States. A socio‐ecological lens was used to examine urban foresters as agents of change in urban ecosystems. Participants assessed the impacts of 40 direct management actions on five goals: (1) canopy cover increase and tree risk reduction, (2) urban heat reduction, (3) people–nature relationships, (4) wildlife habitat, and (5) stormwater interception and infiltration. While certain actions (e.g., in the mature tree maintenance phase) were selected as needed to advance every goal, experts identified numerous actions which aligned with one or several goals, but not all. Preplanting actions, specifically site selection and species selection, presented the greatest opportunities to advance specific goals, suggesting that aligning this phase with city sustainability goals is critical. Participants were highly confident in being able to advance all goals through street tree management, but were more confident in being able to advance the goals of increasing canopy cover while reducing tree risk and of mitigating urban heat, possibly because these goals more closely align with traditional canopy cover goal setting. This research underscores the necessity of considering site‐level ecosystem management actions to advance strategic sustainability goals, while also revealing the complexity of the role and responsibilities of professionals who manage urban ecosystems.