Conserving urban biodiversity: Current practice, barriers, and enablers

Urban biodiversity conservation is critical if cities are to tackle the biodiversity‐extinction crisis and connect people with nature. However, little attention has been paid to how urban environmental managers navigate complex socio‐ecological contexts to conserve biodiversity in cities. We interviewed environmental managers from Australian cities to identify (1) the breadth of conservation actions undertaken and (2) the barriers and enablers to action. We found current practice to be more diverse, innovative, and proactive than previously described (318 actions across nine categories). Conversely, priority actions identified by the literature are yet to be “mainstream” in practice (e.g., designing for human–nature connection, securing space for nature in cities). Further, we identified a suite of levers to overcome barriers. Our research provides scientists and practitioners with an understanding of the multiple facets of conservation in cities and emphasizes the importance of interdisciplinary approaches in future research and practice.

conservation concern (Ives et al., 2016;Schwartz et al., 2013;Sweet et al., 2022). Many species benefit from novel resources and habitats (Kowarik, 2011;Spotswood et al., 2021;Valentine et al., 2020), while for others, cities represent the "last chance" to prevent extinction (Soanes & Lentini, 2019). Urban biodiversity also improves human health and well-being, enhances connectedness to nature, provides ecosystem services to the majority of the world's human population (Cox et al., 2017;de Bell et al., 2018;Shanahan et al., 2015), and provides a critical opportunity to acknowledge the sovereignty of First Nations knowledge systems (Cumpston, 2020;Hall et al., 2021). Consequently, there is widespread interest and investment in urban biodiversity by government and non-government organizations worldwide Perino et al., 2022).
Despite government and public enthusiasm, there are numerous social and ecological challenges to urban biodiversity conservation. Conservation actions must consider the needs and behaviors of the human population, be balanced against other objectives and land-uses, and be bound by constraints of landscape context Hostetler et al., 2011;Muñoz-Erickson et al., 2016). The evidence required to guide conservation action is often inconclusive, impractical or unavailable, and, in some cases, the societal and biodiversity benefits of an action may be in conflict (de Bell et al., 2018;Knapp et al., 2020;Shwartz et al., 2014). Moreover, conserving urban biodiversity may be perceived as a fraught endeavor, especially when effectiveness or feasibility is uncertain (Rega-Brodsky et al., 2022;. These challenges can create an implementation gap, where actions taken may not address goals, nor achieve conservation outcomes (Bush, 2020;Shwartz et al., 2014).
Urban environmental managers are at the forefront of biodiversity conservation in cities. These managers (including practitioners in biodiversity conservation, urban forestry and planning) implement policies that promote biodiversity while balancing the needs and values of a wide variety of stakeholders. However, while overarching "urban nature" initiatives set ambitious targets, they rarely provide guidance on (1) the specific actions that would best achieve these targets and (2) strategies to negotiate complex socio-ecological challenges of implementing actions (Bush, 2020;Nilon et al., 2017;Perino et al., 2022). Stakeholder objectives, community values, and institutional mandates are important to support conservation in a range of contexts (Rose et al., 2018;Walsh et al., 2019). Yet, in urban environments, biodiversity conservation is rarely prioritized and instead is hampered by a lack of resources and lack of engagement with the community Stokes et al., 2010). Further, ecologists wishing to guide action are often removed from on-ground practice and unfamiliar with the challenges and structures of governance, or how these affect implementation (Kay et al., 2022;Muñoz-Erickson et al., 2016). While there has been a shift toward incorporating biodiversity values in urban governance, this has been largely ad hoc or reactive, making it difficult for lessons to be shared beyond administrative silos (e.g., Kay et al., 2022;Muñoz-Erickson et al., 2016;Stokes et al., 2010). Conservation practice in urban environments could be improved by approaches that allow scholars to learn from practitioners, bridge compartmentalized fields of study, and frame knowledge using interdisciplinary approaches that can support further action and policy development (Acuto et al., 2018;Knapp et al., 2020). The aims of this study were therefore to identify (1) the breadth of conservation actions undertaken by urban environmental managers and (2) the barriers and enablers that affect the implementation of these actions. Our interdisciplinary approach is one of the first to provide insights into current practice-the experience of conserving biodiversity in urban environments. By synthesizing across multiple cities, organizations, and action types, we move beyond the case study approach of the current literature to focus on pathways and processes that reflect the typical context of actors in cities and towns worldwide, developing generalizable lessons to improve practice.

Selecting participants
We used purposive, snowball sampling to recruit interview participants who were involved in implementing actions for biodiversity conservation in the urban environment. Twenty-seven participants were interviewed from three organization types across five major cities in Australia (state governments, n = 5; local governments, n = 15; and not-for-profit organizations, n = 7; across Brisbane, Canberra, Melbourne, Perth, and Sydney; see Supporting Information 1 for further details). Our sampled participants were selected to reflect the broad spectrum of actors, governance structures, and urban spaces that contribute to urban biodiversity conservation and therefore allow generalizations beyond the individual contexts Nilon et al., 2017). Their roles included "Biodiversity officer", "Project manager", "Program coordinator", and so on. Data collection ceased once the urban biodiversity conservation actions raised in interviews had already been discussed in previous interviews, suggesting that responses had reached saturation, in accordance with best-practice sampling methods for qualitative interviews (Guest et al., 2006). Organizational and individual details were de-identified for reporting. This project was carried out under approval number 1851835.1, granted by The University of Melbourne Faculty of Science Human Ethics Advisory Group.

Interview schedule
We used semi-structured interviews to encourage unexpected topics to emerge while ensuring that key questions or topics were raised (Bryman, 2012). Interviews were indepth and detailed, ranging 40−106 min (average 1-h). Three researchers (Caragh G. Threlfall, Kylie Soanes, and Cristina E. Ramalho) conducted the interviews between June 2018 and January 2019 as part of a broader project investigating urban biodiversity conservation (see Threlfall et al., 2019). Pilot interviews, post-interview debriefs, and the co-development of questions and prompts ensured consistent approaches among interviewers (see Supporting Information 1). The interview questions relevant to the research aims presented here were as follows: 1. We are interested in understanding the range of things you do for urban biodiversity. Can you tell me some of the things you are doing that you are most proud of? 2. We are trying to understand the costs or barriers to implementing urban conservation. Can you give me an example of a project that couldn't go ahead and why? What is preventing you from doing more of these actions? 3. What do you think would enable you to carry out further actions or initiatives for biodiversity conservation?

Thematic coding
All interviews were digitally recorded, transcribed verbatim, and analyzed with the qualitative data analysis software NVivo 12 (QSR, 2012). The three interviewer researchers (Caragh G. Threlfall, Kylie Soanes, and Cristina E. Ramalho) first coded the transcripts into two question nodes: "actions" and "enablers and barriers." Any actions, barriers, or enablers mentioned outside of their specific questions were also coded into the relevant nodes. A fourth researcher (Lucy Taylor) performed detailed thematic analysis as follows (see Supporting Information 1 for further details): ⋅Actions were classified into "action types." These were developed iteratively and captured the broad range of actions being described (Supporting Informa-tion 2). Each action was classified once, based on the detail, granularity, and overarching intention stated by the interviewee. Visual inspection of the data did not reveal differences among the three organizational groups, so these data were pooled (Supporting Information 1). ⋅Enablers and barriers were first catalogued into 16 types (e.g., lack of data, insurance risks, engaged community, policy and legislation, serendipity; Supporting Information 3), which were then organized around five key themes.

Actions for urban biodiversity conservation
Environmental managers described 318 actions which we grouped into nine, non-mutually exclusive types: (1) managing threats, (2) restoring, (3) greening, (4) adding structures, (5) acquiring land, (6) promoting connection, (7) data and publication, (8) policy and governance, and (9) coordination and outreach (Figure 1, full list in Supporting Information 2). These reflected the range of spatiotemporal scales, land tenures, and taxa reported in the broader literature, including public and informal green space; private land; terrestrial, freshwater and marine systems; and common and "threatened" species and ecosystems. Some actions were small, discrete changes, for example, adding woody debris or removing weeds to increase the habitat value of a park (i.e., "managing threats" or "adding structures," Figure 1). Others were complex, involving multiple actions and stakeholders to achieve a bigger change, for example, converting a neglected drainage ditch into a chain of biodiversity-friendly wetlands (i.e., "restoring," Figure 1). Many of the actions focused on managing stakeholders, such as coordinating events, running educational programs, or developing best-practice guidelines.
The actions aligned with the global literature on urban biodiversity conservation, which typically promotes improving vegetation cover and connectivity, reducing threats, reinstating key habitat elements, and community outreach (Apfelbeck et al., 2020;Beninde et al., 2015;Ikin et al., 2015;MacGregor-Fors et al., 2020;Nilon et al., 2017). However, we found current practice to be more diverse and proactive than previously described, including novel approaches (e.g., mature tree relocation, translocation of native mistletoe onto non-native street trees, 3D-printed wildlife habitat), a focus beyond remnant vegetation, major restoration projects, and landmark policy initiatives. While our analysis is not a quantitative inventory, it provides an opportunity to observe gaps and future research needs. Designing spaces for human-nature interaction was relatively rare, representing less than 5% of all actions described. These actions include deliberate efforts to invite human-nature connection or mindful engagement, as opposed to simply "using" a greenspace (Lumber et al., 2017;Macaulay et al., 2022). Examples included engaging First Nations peoples to inform the design of new parks to support continued stewardship of the country and installing public art features that also provided habitat. The low number of actions was surprising given that improving human-nature connection is frequently highlighted as a motivation for conserving urban biodiversity and that community support is crucial for implementation (Puskás et al., 2021;Taylor et al., 2021;Turo & Gardiner, 2019). Similarly, few actions involved creating new space for biodiversity in cities, with most instead focused on managing and improving existing habitats. Securing land tenure through acquisition or covenants ("acquiring land," Figure 1) was uncommon despite being a mainstay of traditional conservation. This is not surprising: urban managers must compete with high land costs and opportunities to secure large reserves or intact habitats in urban environments are scarce (Kay et al., 2022;Soanes & Lentini, 2019). To that end, achieving gains through alternative approaches, such as improving the capacity of informal green spaces to support biodiversity must play a major role in urban conservation (e.g., de Bell et al., 2018;Nagendra & Ostrom, 2014). Yet, projects to restore or convert urban spaces into biodiversity habitat were also rare-only nine actions within the "Restoring" category represented a net gain in land for conservation. Restoring ecological function to highly degraded, informal green spaces while simultaneously supporting human-nature connection will be key to improving urban landscapes for biodiversity and people and achieving global targets to "live in harmony with nature" (Perino et al., 2022).

Pathways to urban conservation action
The barriers and enablers to action were grouped into five themes: project management, capacity, stakeholder values, organizational support, and ecological context (Table 1,  Table S3). These aligned with the broader literature, including the importance of data and resources, policy and organizational support, and expertise (Kay et al., 2022;Muñoz-Erickson et al., 2016;Ordóñez et al., 2020;Stokes et al., 2010). Enablers were described in response to a particular barrier (e.g., project management to reduce risks), or simply as the optimum conditions to support action (e.g., serendipity, having a good-quality site).

TA B L E 1
The 16 perceived barriers and enablers to urban biodiversity conservation (in italics), as described by urban environmental managers in Australian cities, organized around five themes (in bold)

Barrier
Themes Enabler Overcoming barriers is critical to improve the practice of urban conservation; however, approaches are currently siloed, reactive and inconsistently applied. Many interviewees recognized the need for greater knowledge sharing, expressing curiosity at how other managers had overcome barriers. Indeed, cities research emphasizes the need for flexible solutions and generalizable processes that can be applied across contexts, and the absence of a "one size fits all" solution in urban environments (Knapp et al., 2020;Muñoz-Erickson et al., 2016;Nilon et al., 2017;Ordóñez et al., 2020). To bridge this gap, we synthesized the interactions between barriers and enablers, treating the themes as leverage points to map possible pathways to urban conservation action (Figure 2). Mapping barriers and enablers in this way reveals the pathways used to navigate complex decision-making and implementation contexts. The pathways reflect the experiences of our interviewees and those described in case studies of urban conservation efforts globally (Figure 3). Furthermore, many levers were also described within the inventory of actions-coordination and outreach (Project management and Stakeholder values), data and publication (Capacity), and policy and governance (Organizational support)-showing that these are real opportunities currently used to enact change. These pathways are therefore relevant, accessible solutions that reflect the practical and political landscape within which urban environmental managers operate.
The leverage points of capacity and stakeholder values may be the most tractable for urban environmental managers (Figure 2). Our interviewees used partnerships with external stakeholders and a supportive community of volunteers to source the required expertise and resources to implement an action and overcome a lack of organizational support. The strength of these lever-F I G U R E 2 Pathways to enable actions for conserving urban biodiversity organized around key leverage points and typical barriers. age points is telling in their absence. For example, the successful restoration of highly degraded urban lakes in Bangalore, India, was hampered by a lack of communitygovernment partnerships-the community had the local knowledge and volunteer capacity to support action but could not undertake complicated remedial works without the technical capacity and organizational support of local government (Nagendra & Ostrom, 2014). Similarly, the conversion of vacant lots into biodiversity habitats in Cleveland, USA, was ultimately unsuccessful due to community opposition and vandalism, with researchers noting that they would have benefited from partnerships with organizations with expertise in community outreach and co-design (Turo & Gardiner, 2019).
No single leverage point is a silver bullet, and the most appropriate levers will be highly context dependent. Organizational support, through the establishment of a clear mandate for urban biodiversity actions, is a powerful enabler when present ( Figure 3) but a formidable barrier when absent, and difficult for managers to shift. Many interviewees instead circumvent this barrier using partnerships to improve capacity (e.g., with universities to gather expertise, or other land managers to pool resources), or rely on community and stakeholders to support action (e.g., through volunteers, advocacy, or community groups).
Further, many levers come with costs. For example, the need for data to resolve uncertainty or community outreach activities to improve engagement may place a strain on resources that renders these enablers unusable for some managers (e.g., Figure 3, Aronson et al., 2017). However, by focusing on generalizable processes, the levers and leverage points described here allow urban environmental managers operating in different landscape and governance contexts to influence action using the tools, skills, and resources that best suit their unique circumstances.

CONCLUSION
Our research sheds light not only on what urban environmental managers are doing to conserve biodiversity, but also on how they are doing it. An increased focus on the key barriers and enablers experienced by practitioners is essential for urban biodiversity conservation to address social and ecological challenges and contribute toward global conservation efforts. The urban environmental managers interviewed here were innovative and practical, both in the range of actions they undertake and their approaches to overcoming challenges. This suggests that current practice reflects not only the best-practice proposed by the F I G U R E 3 Case studies of urban biodiversity conservation, the barriers they faced and the pathways to action. These were selected from: our interviews in Australian cities, the Gardens for Wildlife Program (https://gardensforwildlifevictoria.com) and recycling of habitat trees (Hannan et al., 2019); and, international examples, the Urban Monkeys Project (Printes et al., 2010)  scientific literature, but goes beyond, demonstrating an appetite for ambitious and novel restoration works. By documenting current practice, our research gives scientists insights into the daily practice of urban environmental managers, allowing them to better tailor research and recommendations. In particular, research that better supports the restoration of degraded, informal green space and the intentional design of spaces that facilitate human-nature connection will be particularly important for improving both biodiversity conservation and human-nature connection in urban environments (Rega-Brodsky et al., 2022). Our proposed suite of levers and leverage points provides managers with tools and processes to overcome common challenges to urban biodiversity conservation. By synthesizing and sharing generalizable principles, this study can guide governance of urban biodiversity that is both more proactive and effective. Best-practice suggestions for action must be paired with best-practice suggestions for implementation-only then can we bridge the gap between global policy, science and local action that will enable broader restoration goals to be achieved (Perino et al., 2022).

A C K N O W L E D G M E N T S
We thank the urban environmental managers who participated in our study and were so generous with their time and knowledge. We are grateful to the editors, anonymous reviewers, Margaret Stanley and Dieter Hochuli, who provided valuable comments to improve this manuscript. This research was funded by the Clean Air and Urban Landscapes Hub of the Australian Government's National Environmental Science Program.Kylie Soanes was also supported by a Melbourne Research Fellowship through the University of Melbourne. Caragh G. Threlfall was also supported by an Australian Research Council Discovery Early Career Researcher Fellowship (DE200101226).

D ATA AVA I L A B I L I T Y S TAT E M E N T
The data that support the findings of this study are available on request from the corresponding author. The data are not publicly available due to privacy or ethical restrictions relating to human participants.