Abstract
Urban forest management is crucial for supporting human well-being, ecosystems, and society, particularly with expanding global urban population and multi-uses of these urban greenspaces. This literature review examines the conceptualization and factors that contribute to conflicts and/or collaborations in urban forest management, including, but not limited to, diverse actors’ uses, needs, and perceptions. Using PRISMA methods, we systematically reviewed 176 scholarly articles published between 2013 and 2021 and found that most articles were primarily from the United States, Australia, and Canada. Findings highlight the need for clearer definitions of collaboration, emphasizing communication, operational tasks, planning, and shared beliefs among actors. Positive collaborations involved multi-level engagement and inclusive decision-making. In most cases, multiple issues contributed to conflict, including a variety of stakeholders with differing viewpoints on a given situation. Conflicts are commonly complex situations that do not lend themselves to a one-size-fits-all solution and tend to be a unique manifestation of the people, places, and perspectives involved. Our review can inform practitioners about more inclusive practices and adaptive management of urban forests. We conclude by providing lessons learned and suggestions for future research on stakeholder involvement, public education, governance, policy, decision-making, and the role of biophysical and ecosystem services in urban forest collaboration and conflicts.
Introduction
Urban forests provide a plethora of ecosystem services (Davies et al. 2018;Bonilla-Duarte et al. 2021). Urban forests also provide a critical space for nature interactions, as the majority of the world’s population lives in urban areas (United Nations 2018). Therefore, the socio-ecological nature of urban forest management engages with multiple actors across temporal and geographic scales. These diverse actors’ values and perceptions can incite conflicts or opportunities to collaborate on urban tree management, governance (Kirkpatrick et al. 2013), and the provisioning of ecosystem services and disservices (Kirkpatrick et al. 2013; Roman et al. 2021). Governance is the act of coordinating action towards accomplishing goals (Kjær 2004). Specifically, urban forest governance involves complex decision making and diverse actors. Actors are those individuals and collective groups that influence or make decisions about urban forests or individual urban trees (Lawrence et al. 2013). Actors can also influence urban forest decision making based on the resources and discourses they engage in and their collective engagements (Ordóñez et al. 2023). Although local authorities are important, urban forest governance also incorporates the values, priorities, and management pressures from the public and private sectors and civil society (Konijnendijk van den Bosch 2015).
Collaboration is recognized as a pivotal component of urban forest management (Doucet et al. 2024), but there are only a few studies that investigated the best strategies for collaboration (Vasquez-Brust et al. 2020). Governance that facilitates collaboration and reduces conflict is increasingly important as most of the world’s population lives in urban areas (United Nations 2018). Governance that facilitates collaboration has shared goals, relationships of trust, and information sharing (Lopes et al. 2020; Wirtz et al. 2021). Effective governance approaches, particularly in urban forestry, include financial resources, decisions driven by data, and setting goals, objectives, targets, and shared visions (Wirtz et al. 2021).
Human behaviors and decision making influence urban forest function through planning processes, tree species selections (Hilbert et al. 2023), maintenance, and removals (McPherson et al. 2003). Owing to the diverse uses, perceptions, and preferences surrounding urban forest management, conflicts can occur among actors, including (1) differing values between professionals such as municipal managers, developers, and arborists (Kirkpatrick et al. 2013; Kronenberg 2015; Ordóñez et al. 2019); and (2) differing priorities between forestry professionals and the public (Carmichael and McDonough 2019). For example, city planners and arborists may have contrasting perspectives about where to place trees and how to maintain them in the urban landscape (Kirkpatrick et al. 2013). Likewise, urban residents and forestry professionals may disagree about tree risk perceptions (Clark et al. 2020). Conflicts around urban trees and associated divisive values can foster a lack of community engagement and challenge stewardship initiatives (Kronenberg 2015). Likewise, conflicts can occur at diverse levels and scales of human-nature interactions. Urban forest management conflicts can involve (1) contrasting priorities between citizens and non-profit tree advocacy groups (Carmichael and McDonough 2019); (2) coordination challenges between municipal forest managers and urban development actors; and (3) general risk aversion attitudes of the public (Ordóñez et al. 2020b).
On the other hand, collaboration may be equally varied in urban forest management and may occur between the public and municipal tree managers and between local governments and civic organizations. Collaboration between the public and professionals can motivate stewardship and engagement (Nesbitt et al. 2019) and provide a way to overcome challenges faced by natural resource managers with limited resources and capacity (Nannini et al. 1998). For example, residents who have previously planted trees shared a willingness to partner with municipal urban forestry initiatives (Conway and Bang 2014). In a case study analysis of Boston (Massachusetts), Baltimore (Maryland), and Philadelphia (Pennsylvania), effective partnerships were established between the cities’ Parks and Recreation departments and nonprofit organizations that support urban tree initiatives (Foo 2018).
To our knowledge, there is no comprehensive literature review on an international scale about conflict and/or collaborations related to urban forest use, governance, perceptions, and management. Previous research on urban forestry studied challenges and successes of collaboration between non-government organizations and local governments in 9 Canadian cities (Doucet et al. 2024), Latin America (Ordóñez et al. 2023), and the Caribbean (Devisscher et al. 2022). Previous literature reviews studied urban forest managers’ perspectives on governance and decision making (Ordóñez et al. 2019), the link between urban forest use, management, and social problems (Referowska-Chodak 2019), and the types of conflicts experienced in densifying greenspaces (Madureira and Monteiro 2021). Previous studies highlight that a key cause of conflicts in urban forest management include disputes between recreational users (Wilkes-Allemann et al. 2015b). Furthermore, there is a spectrum of perceptions about urban trees which may lead to conflicts because of the varied values and attitudes held about trees and depending on the type of forestry professional involved (Kirkpatrick et al. 2013). Collaboration presents an opportunity to include all interests and a shared vision (Elmendorf and Luloff 2001). Having shared aims and goals can facilitate collaboration in urban forest management. Shared goals might include securing natural spaces in and around urban environments (Ruliffson et al. 2002), collaborating around environmental stewardship through outreach, research, and sharing knowledge (Nannini et al. 1998; Driscoll et al. 2012), and developing opportunities for social learning between the public and government (Yamaki 2016). Collaboration among urban forestry professionals also creates opportunities for sharing resources and building relationships (Cadaval et al. 2024).
The purpose of this review is to assess: (1) how conflict and collaboration have been defined in previous studies about urban forests, including relevant socio-ecological contexts; (2) the actors involved in urban forest conflicts and collaborations; (3) lessons learned about conflict and collaboration in urban forest management; and (4) opportunities for future research on conflict and/or collaboration in urban forest management.
Materials and Methods
We searched ScienceDirect, SCOPUS, and Web of Science databases to find peer-reviewed journal articles, literature reviews, and perspective articles, excluding book chapters and editorials. The search was open to any time period and geographic location. We included literature in English and Spanish languages. We identified relevant articles using: (1) “urban” OR “cities” OR “metropolitan” OR “towns” OR “municipal” AND (2) “trees” OR “forests” AND (3) “collaboration” OR “cooperation” OR “partnerships” OR “coordination” OR “collabo*” OR “partner*” OR “conflict” OR “disagree” OR “dispute.” We used the PRISMA flow diagram to systematically document the search results (Figure 1)(Moher et al. 2009). The eligibility criteria for articles included studies that focused on one or multiple urban areas, research that focused on conflict and collaboration in urban forest management at the policy and/or stakeholder level, and excluded studies that did not specify an urban area.
PRISMA flow diagram of the resource-screening and article-selection process. Adapted from Page et al. 2021.
The initial search returned 4,409 articles from SCOPUS (2,284), Web of Science (1,537), and Pro-Quest (588). These articles were then imported into the Mendeley bibliography management software. After deleting 2,631 duplicate records, 1,778 were imported into Microsoft Excel to be screened by 4 reviewers against eligibility and exclusion criteria. At this phase, each reviewer screened the title and abstract and retrieved 345 articles for full-text review (Figure 1).
The final remaining articles were thoroughly analyzed qualitatively and quantitatively using codes deducted from our research questions (Table 1). To minimize bias, we conducted an intercoder reliability test where a selected reading was shared among the research team and separately coded by each. The final coding process was completed using a mix of QSR NVivo (Lumivero 2020) and a Qualtrics online form available through the University of Florida. Using a Qualtrics online form allowed multiple reviewers to code different articles and provided a way to organize the results. On the other hand, other review questions were coded qualitatively to get more in-depth responses such as lessons learned, definitions of conflict or collaboration, and opportunities for future research (Table 1). Following the PRISMA procedures (Figure 1), the final number of included articles for review was 176.
Codes stemmed from the research questions and study goals and the expected responses of each.
Results
Description of Literature
From the 1,778 screened articles, we included 176 papers for final analysis, the majority of which are research papers (134), reviews (13), opinions (6), and others, such as case studies (23). All articles were published between 1989 and 2021, although most of them were published in the last decade (Figure 2) in primarily Urban Forestry & Urban Greening (40), Forests (9), Landscape and Urban Planning (8), Journal of Arboriculture (7), Arboriculture & Urban Forestry (6), Cities (3), and Forestry (2). However, some papers (97) were published in journals specializing in other disciplines.
Number of articles published over time about conflict and collaboration in urban forestry.
Out of the 176 scholarly articles, 63 used qualitative methods (i.e., interviews, focus groups, participant observation, document analysis, etc.), 56 used quantitative methods (i.e., surveys, census data, or questionnaires), and 40 used a mixed methods approach, including a combination of qualitative, quantitative, and spatial, while 12 articles used spatial data only. The top 5 countries producing articles about conflict and collaboration in urban forests were the United States (57), Australia (10), Canada (9), the United Kingdom of Great Britain and Northern Ireland (8), and Germany (6)(Figure 3). Most articles focused on urban forestry issues at the city (81) and national levels (33), while the other papers addressed multi-national, regional, or smaller scales (54), like communities, neighborhoods, or college and university campuses (Table 2).
Geographic distribution of literature on conflict and collaboration in urban forestry. Darker shades illustrate where in the world more research is done that discusses conflict and collaboration in urban forestry. Count reflects how many articles were identified from each geographic region.
Research scale used in literature about conflict and collaboration in urban forestry.
Frameworks and Theories Used
Of all the papers reviewed, 73 articles explicitly used theories, models, or frameworks to guide their research on conflict and/or collaboration in urban forests. The theories and frameworks were organized into 5 broad categories, including: (1) theories of motivation, cognition, and reasoning; (2) morals, intuitions, culture, and identity-based theories; (3) trust, negotiations, and public involvement; (4) organizational theories; or (5) systems theories. Most articles that used a theory/ framework focused on trust and public involvement or systems theories (Table 3).
Theories used in articles describing conflict and collaboration.
Collaboration and Conflict in Urban Forest Governance and Management
Our literature review revealed various contexts, issues, and priorities regarding urban forest management, governance, and use that impacted collaboration and/or conflict. These discussions about conflict and collaboration revolved around the intricacies of urban forestry projects (Sipilä and Tyrväinen 2005; James et al. 2009; Young 2011), governance (Pinto et al. 2016; Kozová et al. 2018; van der Jagt and Lawrence 2018; Ordóñez et al. 2020a; Frantzeskaki and Bush 2021; Pinkerton and Rutherford 2021), or social concepts like values and attitudes (Tyrväinen et al. 2003; O’Brien 2005; Muller and Bornstein 2010; Stobbart and Johnston 2012). However, precise definitions of these concepts were absent from most of the literature reviewed.
Understanding Conflict
Overall, our results found that conflicts in urban forestry governance resulted in setbacks, unforeseen obstacles, mismanagement, and disengagement with relevant stakeholders. In addition, conflicts also delayed program initiatives, creating a need to reevaluate management priorities and activities and, in some cases, leading to certain management efforts being completely forgone. In the literature, the causes of such conflicts varied based on the diversity of people involved, geographic location, time, and constraints, such as legal, ethical, financial, and public health and safety. Overall, conflicts within urban forestry did not conform to a one-size-fits-all model. Rather, there were many potential causes.
Our results show that the top contributors to conflicts in urban forest management included: unaligned or differing goals (96 articles) and lack of or poor communication with the public (61)(Table 4). We found several smaller categories describing the factors contributing to conflict as planning and policy or political issues (20), management (16), land use and development (15), infrastructure and resource allocation (15), environmental concerns (11), climate change and sustainability (8), risk and disasters (5), and tree services and tree equity (10)(Table 4). Specifically, 37% of articles reported conflicts between professionals (Clark and Matheny 1998; Kuhns et al. 2002; Shapira et al. 2013; Pinkerton and Rutherford 2021), 62% reported conflicts between professionals and the general public (Ruliffson et al. 2002; Reams et al. 2005; Jankovska et al. 2010; McMillen et al. 2019), and 36% reported conflicts within the general public (Mattila et al. 2015; Wilkes-Allemann et al. 2015b; Kraxner et al. 2016)(Table 5). Lack of or poor communication was frequently cited as a cause for conflicts in urban forest management. These included conflicts that resulted from lack of or poor communication with other organizations (Wu et al. 2019; Madureira and Monteiro 2021), the public (Elmendorf and Luloff 2001; van der Jagt and Lawrence 2018), or internal conflicts within the institution (Pincetl 2010; Harper et al. 2018; McGrath et al. 2021). Lack of resources (Nannini et al. 1998; O’Callaghan and Skelly 2013), safety (Gasson and Cutler 1998; Conway and Bang 2014), unaligned or differing goals (Shapira et al. 2013; Davies et al. 2018), and maintenance issues also occasionally led to conflict (Breuste 2013).
Factors that contribute to conflicts in urban forest governance.
Overview of general categories for different types of conflicts.
Furthermore, most articles presented multiple layers of conflicts. For example, 66 studies with defined conflicts highlighted that such issues often feature multiple overlapping variables (e.g., management, policy and planning, budget and staffing, and public and private stakeholders)(Muller and Bornstein 2010; Nesbitt et al. 2019; Köse et al. 2021). Similarly, 94 articles without clear definitions of conflict also featured multiple overlapping variables, which provided context to the conflict such as conservation, development, social characteristics, and political characteristics (Zinzani and Curzi 2020; Rodriguez et al. 2021). Furthermore, there was considerable overlap across studies, wherein 30% of studies described multiple categories of conflict. Examples include studies that expressed both internal conflicts between professionals along with external conflicts between professionals and the public (Nordström et al. 2010; Morgenroth et al. 2015; Ordóñez et al. 2020a), as well as conflicts within the general public and conflicts between professionals and the general public (O’Brien 2005; Aasetre et al. 2016; Svendsen et al. 2021).
A more detailed look at unaligned or differing goals as a source of conflict within urban forestry showed that management (13), development (7), and land use (6) were the highest-ranking factors that contributed to conflicts. Conflicts about lack of resources were primarily attributed to budget and staffing (12), financial costs (12), and environmental concerns (3). We also found that management (16)(e.g., Gundersen et al. 2006; Gutsch et al. 2019), land use (9)(e.g., Ballantyne et al. 2014; Pinto et al. 2016; Steenberg et al. 2019), and policy and planning (9)(e.g., Lawrence and Ambrose-Oji 2015; Brown et al. 2018) were frequently cited. Fifty-one (51) articles described conflicts centered on stakeholders and social factors.
Understanding Collaboration in Urban Forest Management
Definitions of Collaboration
Few papers specifically defined “collaboration” as a concept or within the context of a specific case or research question. Four research articles provided explicit definitions of collaboration as (1) achieving consensus (Shapira et al. 2013); (2) having “compatibilities” (Madureira and Monteiro 2021); (3) achieving interdependence and interaction by working through differences to find solutions while incorporating trust and shared visions (Elmendorf and Luloff 2001); or (4) when two parties have a vested interest in a public-private partnership (Nannini et al. 1998). In one perspective paper, collaboration meant sharing power to define problems and develop solutions by deconstructing barriers for participants (McGrath et al. 2021). On the other hand, 7 papers specifically discussed “partnerships” and their importance for effective governance (Kozová et al. 2018; Garrison 2019). Furthermore, developing and maintaining partnerships helped participants overcome challenges by relying on each other’s experiences (Bierzychudek 2020; Svendsen et al. 2021).
Who is Included in Collaborative Urban Forest Management?
Globally, partnerships supporting urban forestry management included: collaborations between residents, community-based organizations, public-private collaborations, and partnerships between municipalities and vulnerable groups (Kuchelmeister 2000; Ryu and Chi 2021). For example, effective partnerships in urban forestry initiatives like tree planting in New York City included community groups, non-profit organizations, and government agencies (Moskell and Allred 2013). Actors involved in collaborative management included: (1) policy and management actors at local to federal levels; (2) extension agents and researchers; (3) actors in the private sector; (4) professionals in urban forestry fields; (5) volunteers, non-profit actors, master gardeners, and other related interest groups: and (6) “residents” or the “public.”
Collaborations in urban forest governance happened at varying levels, including horizontally between legislative and executive institutions and vertically between institutions of land-use planning (Maruna et al. 2019). Non-profit organizations were also formed organically to support actors with diverse views about urban forest management actions, such as removing suburban recreational forests in Cape Town, South Africa (Day and Patel 2021). Through collaborative processes, communities and community-level actors are empowered to impact management actions, as exemplified in the development of a community forest and urban park in Migdal HaEmek, Israel (Gasul and Shmueli 2016), and the involvement of residents in monitoring to manage Dutch elm disease in California, USA (Nannini et al. 1998). Additionally, in the Midwestern and Eastern United States, collaborative tree planting efforts that included residents experienced increased neighborhood ties and positive resident perceptions about neighborhood beauty and place appreciation (Watkins et al. 2018).
Our review revealed other methods to engage the community in collaborative urban forest management, such as: public trainings and inclusion in tree-monitoring efforts (Nannini et al. 1998), shared planting and maintenance of city trees (McGrath et al. 2021), knowledge co-production and informationsharing (McGrath et al. 2021), community events and grassroots initiatives (Young 2011; De Smet and Van Reusel 2018), integrating collaborative decision making (McMillen et al. 2019), and designing collaborative structures into management programs and recruiting and empowering community actors to influence urban forest management activities (Gasul and Shmueli 2016).
Factors that Contribute to Collaboration in Urban Forest Management
Most articles described aspects of collaboration, including communication, process, and shared beliefs and desires (Table 6). Most papers (67) discussed communication with the public as central to collaboration and shared goals. Communication with the public about tree planting initiatives in community greening programs varied and sometimes resulted in resistance to partner with urban greening efforts, for example, when residents are not effectively consulted or supported (Carmichael and McDonough 2018). Likewise, research revealed a need to further engage with and inform the public about urban forestry and tree planting (Moskell and Allred 2013) to avoid disruptive interactions and improve the efficacy of urban forestry planning (Wilkes-Allemann et al. 2015a).
Factors that contributed to collaborative processes in urban forest management.
Sixty-five articles described other factors contributing to collaboration in urban forest management, including resources, inclusion, and leadership. Among the 12 papers that identified resources as a key component of collaboration, 3 types of resources were highlighted: people (Kuchelmeister 2000; O’Brien 2005; Brown et al. 2018), information and data (Gutsch et al. 2019; Alexander et al. 2020; Dupéy et al. 2021), and financial resources (Pincetl 2010; Dupéy et al. 2021). Various studies highlighted the importance of inclusion, accessibility (Ugolini et al. 2015; Nesbitt et al. 2019; Ordóñez et al. 2019), understanding (Nordström et al. 2010; Nguyen et al. 2017; Sotirov et al. 2017; Dupéy et al. 2021), and diversity (Elmendorf and Luloff 2001; Zinzani and Curzi 2020; Köse et al. 2021; Pinkerton and Rutherford 2021) in collaboration.
How Collaboration Is Categorized and Suggestions for Incorporating Collaborative Processes
Collaboration in urban forests was generally categorized as occurring (1) between professionals and the general public (70); (2) between professionals (97); or (3) other observations (102). Among the papers that discussed collaboration, several key themes describe how professionals engaged with the general public, such as (1) tree planting programs and public engagement; (2) urban forest management challenges, like public views about urban trees or management practices, risk aversion, and increased demand for green spaces; and (3) inclusive decision making and governance. Residents could be engaged in urban tree planting and retaining trees through bottom-up planning and place-making (De Smet and Van Reusel 2018) or through providing data and feedback that informed attitudes towards trees and preferred planting behaviors (Dilley and Wolf 2013).
Twenty-two papers studied some aspects of collaborative planning in urban forests and focused on resident or public inclusion or inter-institutional cooperation. Several papers highlighted contexts where resident participation was valued and incorporated, thereby leading to fewer conflicts throughout planning processes (Sipilä and Tyrväinen 2005; Stobbart and Johnston 2012; Dilley and Wolf 2013; De Smet and Reusel 2018). In some cases, goal setting with residents about urban forests and early inclusion in planning reduced conflicts (Sipilä and Tyrväinen 2005; Stobbart and Johnston 2012; De Smet and Reusel 2018). Additionally, understanding and collecting social data about residents informed the development of public outreach programs at more local scales (Dilley and Wolf 2013). Specifically, understanding perspectives held by diverse actors informed the acceptability of urban trees, planting, and their diverse characteristics. For instance, older residents were more likely to view larger trees as having greater potential to cause property damage versus younger residents (Fernandes et al. 2019). Residents who lived on streets lined with certain species, like black poplar trees (Populus nigra), were less likely to “like” trees and associated trees with increased litter (Fernandes et al. 2019). Understanding local perspectives helped develop resources to inform residents’ acceptability of street trees and provided contexts for why the public may be reluctant to or challenge tree planting. Likewise, understanding the negative relationship between people and urban forests guided management strategies (Referowska-Chodak 2019), as trees occupied different meanings in various cultural spaces over the course of residents’ lives (Shimada and Johnston 2013). Trees that require little ongoing maintenance (i.e., conifers that minimize leaf clean up) and those that are smaller in stature, as well as low-cost planting material and subsidies for tree pruning also increased the number of willing participants or improved tree acceptance (Conway and Bang 2014).
Collaborative processes also occurred among institutional actors. Specifically, urban planning for city trees required greater inter-institutional coordination (Muller and Bornstein 2010; Bonilla-Duarte et al. 2021; Cheng et al. 2021), and conflicts could be reduced when interested parties felt included in the planning process (Wilkes-Allemann et al. 2015b). Neighboring municipalities that coordinated and shared governmental contracts reduced staff time, streamlined operations, cut expenses, shared data and information, and prevented competition for a limited number of available contractors at the municipal level (Alexander et al. 2020). Other research noted that urban forest management is enhanced by involving differing needs or perspectives based on sociodemographic factors and differences (Fraser and Kenney 2000; Jorgensen and Anthopoulou 2007).
Discussion
Our systematic literature review provided insights about the factors that contributed to conflict and collaboration in urban forest management, including opportunities for better governance. Overall, there was little to no universal definition of conflict and/or collaboration used in the literature. The majority of papers published about conflict and collaboration in urban forests came from English-speaking countries, despite the global increase in urban populations and importance of urban forests for urban nature interactions. Additionally, the diversity of journals in which papers on urban forest conflict and collaboration are found suggested that research on this subject is widely relevant and interdisciplinary. Our research was limited to only articles on urban trees and forestry; future research could investigate conflicts and collaboration in other urban greenspaces or natural-resource contexts.
After examining the various contexts presented in these articles, we defined conflict and collaboration based on several conditions. The challenges that lead to conflicts included disagreement over goals, especially management, development, and land use. Additionally, conflicts stemmed from procedural and operational challenges, such as lack of resources, maintenance, safety, and communication within and with other groups or actors. Collaboration processes could support governance of urban forests by incorporating conflict-management actions. Through a cycle of interaction, developing trust, and interdependence among actors, participants could identify barriers, challenges, and differences, and begin processing conflicts and develop solutions. Feedback in the collaboration cycle strengthened the development of trust and encouraged continued engagement among actors.
Collaboration and conflict could occur in different phases of urban forest management, including defining management priorities (including the design/planning phase), management goals, maintenance activities (tree planting and removals, etc.), and how urban trees or forests were perceived and used. Each phase presented conditions and feedback that informed whether conflict or collaboration was present or possible, including a range of factors that contributed to collaborative/ conflictive outcomes.
Urban forest managers believed urban forest management is successfully supported by including (1) sufficient financial resources; (2) data-informed decision making; and (3) clearly identified goals, objectives, and targets (Wirtz et al. 2021). However, urban forest management could be challenged by (1) lack of funds or insufficient resources; (2) lack of support from internal and external actors; (3) the pressure to develop urban areas; and (4) barriers to developing laws and policy (Wirtz et al. 2021). Through enacting collaborative processes, many challenges could be addressed, and actors could develop a shared sense of responsibility and leverage resources to ensure support for shared visions and goals (Wirtz et al. 2021).
The conflict and collaboration literature paints a complex picture of how people and trees interact in cities, highlighting the relationships that shape urban landscapes. Collaboration emerges as a critical element in responding to widespread urban forest challenges, such as invasive species (Alexander et al. 2020). For example, the Emerging Pests in Colorado (EPIC) working group and the associated Colorado EAB Response Team (CORT) acknowledges interagency collaboration as key to their success in preparing for the arrival of emerald ash borer (EAB), Agrilus planipennis Fairmaire (Coleoptera: Buprestidae). Preemptive response and education was expedited by organizational interactions rooted in professionalism and characterized by open communication and clearly defined agency roles, responsibilities, and limitations (Alexander et al. 2020). System-wide impacts could be addressed by involving multiple agencies and emphasizing resources, action, and knowledge sharing (Alexander et al. 2020).
The literature emphasized interconnected collaboration through community-engagement actions and inclusive decision making. To combat conflicts related to urban forest use, Wilkes-Allemann et al. (2015b) emphasized that communication played a pivotal role. Furthermore, response strategies should reflect local contexts and include all relevant actors. As beneficiaries to the services provided by urban trees, input by urban residents can be valuable to planners and managers, informing decision makers about use, preferences, and perspectives. Previous studies showed collaborative processes between citizen organizations and government agencies (Yamaki 2016) and the attitudes and perceptions of diverse actors toward professional collaboration opportunities and knowledge transfer (Ugolini et al. 2018). Collaboration with urban residents played a crucial role in shaping urban forestry programs. However, diverse actors may hold differing experiences, perceptions, and values about trees, and may lead to urban tree resistance.
The relevant challenges and opportunities for collaboration showed a need for more adaptive management and a cultural shift towards greater inclusion by managing ecological, social, and economic dimensions of urban forests. Collaboration is crucial for the sustainable and effective management of urban forests and trees and could enhance social learning and networks (Yamaki 2016). Conflicts among diverse actors could be reduced by including greater public participation in the planning process, increasing public education and engagement, and incorporating local dimensions and contexts into tree management (Referowska-Chodak 2019). Similar and overarching goals about urban forest management created opportunities to collaborate (Stobbart and Johnston 2012). Studies about coordination included various entities like government agencies and private actors (Pincetl et al. 2013). Tree planting initiatives where residents and non-profit organizations or municipal governments collaborated increased neighborhood ties among participating residents (Watkins et al. 2018).
The literature presents a need for mutual understanding and cooperation among different actors. Understanding cultural values and histories is crucial in shaping public attitudes towards urban forestry, emphasizing the need for culturally sensitive approaches in planning and management. Cultural backgrounds influence perceptions of urban trees, and the education and engagement of leaders is critical for developing multileveled partnerships (Fraser and Kenney 2000). Conflicts surrounding urban forests involve emotional, moral, and territorial dimensions (Kirkpatrick et al. 2013).
Engaging residents in decision-making processes and addressing conflicting views regarding risk, danger, or nuisance may shift negative perceptions about trees. For example, by working collaboratively with urban homeowners for the Residential Trees Survey program in Seattle (Washington), managers engaged with communities directly, understood their perspectives, and incorporated resident input into urban forest management (Dilley and Wolf 2013). Tools like Volunteer Geographic Information (VGI) could enhance participatory planning in urban forests (Foster et al. 2017). Despite VGI’s opportunities for collaborations between urban forestry managers and residents in mapping trees, technologies such as VGI can result in uneven community participation and misrepresent data about who engages with this tool, emphasizing the need for careful data consideration and inclusivity in planning processes.
Opportunities for Future Research
Our systematic literature review highlighted challenges, contexts, and factors associated with conflicts and collaboration with urban forest management. The analysis also revealed numerous opportunities for future research to better understand conflict and collaboration regarding (1) stakeholder involvement and public education; (2) governance, policies, and decision making; (3) collaboration; and (4) biophysical assessments and human interactions and conflicts.
Stakeholder involvement and public education about urban forest management could shape the effectiveness of urban forest management. More research is needed to identify stakeholder needs in urban forestry, including more multidisciplinary research on pressures and threats related to human activities in urban and suburban forests (Živojinović and Wolfslehner 2015). It is important to understand the most effective ways to educate the public and provide stakeholder involvement opportunities (Moskell and Allred 2013; Wilkes-Allemann et al. 2015b; Davies et al. 2018; Day and Patel 2021). Although the public impacts policies, there is limited understanding of how the public can impact complex urban politics and forest management (Ryu and Chi 2021). More research is needed on recognitional equity, or the ability of practitioners and urban residents to influence governance and decision making (Nesbitt et al. 2019). Although professionals are pivotal to urban forest management, there is a need to study how knowledge is transferred between stakeholders in the fields of urban forestry and green infrastructure (Ugolini et al. 2015). There is limited research about the perspectives of professionals (Kirkpatrick et al. 2013) and the roles, development, and impacts of intermediaries on urban forest policy and management (Frantzeskaki and Bush 2021).
Stewardship activities present an important way to engage with the public and for the public to interact with urban trees. However, there was limited research about whether legal training programs impact the efficacy of volunteer-led urban forest tree committees (Harper et al. 2018), including whether stewardship on public or private lands impacts local environmental outcomes (Romolini et al. 2013). In addition, although there is increasing research about resident perceptions of urban forests and urban trees, including perceptions about conflicts, studies were usually missing details about the types of recreational participants (‘passing through groups’) or perspectives on forest pest management and strategies in urban forests (Gutsch et al. 2019).
Tree planting programs are often promoted as an effective way to increase urban tree canopy and reduce inequities in urban greenspaces. However, only a handful of research focuses on people’s acceptance of tree giveaway programs and aftermaths, including the dynamic between urban greenspaces like urban forests and gentrification (Garrison 2019). More research is needed to assess residents’ perceptions of urban trees, including their attitudes and behaviors (Tyrväinen et al. 2003; Nguyen et al. 2017), local ecological and human/social conditions and how this interacts with tree planting (Pincetl et al. 2013), and strategic governance of large-scale urban afforestation (Yao et al. 2019). In addition, resistance to street tree planting programs is not well understood, particularly for younger adults (Carmichael et al. 2019), including the behaviors and attitudes of renters, multi-family homeowners, and commercial property owners about large-scale tree plantings (Dilley and Wolf 2013), and differences in beliefs about responsibility and tree stewardship (Moskell and Allred 2013). A better understanding of public perceptions/awareness of preserved urban forests is needed as well as how to install, manage, and protect such green spaces (Jankovska et al. 2010). Urban forests serve a variety of people. However, there is little understanding of differing views on natural areas and challenges pertaining to development, preferences, activities, and current/future social conflicts (Aasetre et al. 2016). Scholars suggest using more qualitative, nonlinear, and non-written approaches to interact with people and collect data about urban trees, including key informant interviews, focus groups, stakeholder mapping, vision galleries, and sacred place mapping (Elmendorf and Luloff 2021).
Conflicts in urban forest management often result from different approaches to governance and decision making. There is a need to assess how tree canopy cover is affected by various coordination processes, how municipalities prioritize management (Ordóñez et al. 2020a), and how governance structures and policies affect the management and planning of urban forests (Wilkes-Allemann et al. 2015a, 2015b).
Policy impacts the funding, outcomes, actors, and directions of urban forestry. However, there are limited assessments about how science and data influence the planning, funding initiatives, and outcomes of urban forestry and public-private partnerships (Young 2011), along with assessments of more efficient means of integrating ecological research into the decision-making process (Driscoll et al. 2012). Furthermore, future research can assess the difference in capacities of municipal managers, including their operations (budgets, personnel, etc.), management processes, public engagement, and governance frameworks, and how these in turn impact conflicts and urban forest management, especially beyond the continental US (Ordóñez et al. 2019). Future research can also assess whether social media can influence local policies on urban forest management (Gillespie and Nguyen 2019), and which policies are most effective at preserving urban forests (Wu et al. 2019). In addition, although land use impacts urban conservation outcomes, including potential conflicts and collaboration efforts, there is limited understanding about the interplay between land-use policies, climate actions, and urban forest management, impact, outcomes, and planning processes (Cheng et al. 2021).
Owing to the diversity of stakeholders, uses, and policies involved in urban forestry, collaboration is usually a key aspect of its effective management and stewardship. On the other hand, ineffective collaboration efforts can also lead to conflicts. Therefore, there is a need to improve understanding about the success and failures of the participatory governance and urban forestry (Kozová et al. 2018), including investigations about how representative participatory and collaborative planning is (Sipilä and Tyrväinen 2005), and how the theory of social networks impacts collaborations of urban forest management (Yamaki 2016) and publicprivate partnerships that may impact responses to complex disturbances (Svendsen et al. 2021).
Forest management, ecological conditions, and design can impact users’ perceptions, experiences, and interactions within space. Conflicts and/or collaboration may occur based on biophysical conditions. Therefore, more research is needed to assess urban forests’ carrying capacity, including biophysical and social carrying capacity (Wilkes-Allemann et al. 2015b); research on tree growth/longevity; production and sales (Leibowitz 2012); and resulting impacts on conflicts and/or collaboration. Future research could further elucidate whether biological effects of different trail types/activities, recreational use, and trail-based fragmentation may impact surrounding ecosystems and potential conflicts (Ballantyne et al. 2014). In addition, more research is needed to assess how landscape design and management can better serve local ecosystems and urban residents. Invasive species management in urban areas may also be contentious for some stakeholders. However, there is limited research about invasive species management in urban ecosystems and whether it instigates stewardship and collaboration activities around urban forest management (McMillen et al. 2019). Human activities in urban ecosystems also have ripple effects on urban forests. More research is needed to assess what percent of tree damage is caused by lawnmowers (Morgenroth et al. 2015). Communication about urban forest management and conditions may also impact the development or dissolution of conflicts.
Conclusion
Overall, much remains to be studied about conflict and collaboration in urban forest management. As urban population increases globally, a better understanding of conflict and collaboration is critical for effective urban forest management to enhance human wellbeing and the provisioning of ecosystem services, as well as the functioning of urban forest ecosystems. The majority of the research that is available comes from more developed or industrialized countries, although urbanization is a global phenomenon. In several cases, across geographies, local contexts were highlighted as influencing or being impacted by different types of conflict or collaborations. While our systematic review highlights factors that enhance collaboration and reduce conflicts in urban forest management, our review also acknowledges that there are multiple opportunities for future research to improve collaborative decision making for the sustainability of urban forests.
Acknowledgements
This research was made possible by funding from the University of Florida and the Science and Research Committee (SRC) of the International Society of Arboriculture (ISA). The authors would also like to thank Dr. Lara A. Roman, Dr. Andrew K. Koeser, and Dr. Theodore Eisenman for providing feedback on the development of this research, and Laurel Kaminsky and the University of Florida’s Marston Science Library for their support in the literature search phase.
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