Collaborating for nature-based solutions: bringing research and practice together

ABSTRACT Nature-based solutions (NBS) is a relatively novel concept and real-world application has only started to proliferate in cities, which motivates addressing early attempts of cross-boundary collaboration for implementing NBS. The aim of this paper is to reflect about the process of transdisciplinary research-practice collaboration on NBS and its associated learnings, potentials and challenges. To do so, this paper reflects on one of the local urban-regional innovation partnerships within the Naturvation research project, which included urban planning practitioners, researchers and public and private organisations, and aimed to understand what NBS can achieve in cities and how to advance implementation through collaboration. This paper is based on embedded research and uses participant observation as methodological inspiration. It draws on two streams of literature to frame the reflections; (a) transdisciplinary research, to reflect on the collaborative process of research and practice engaging in learning and knowledge co-production and (b) boundary concepts, to capture the boundary-spanning nature of NBS. Observations, grey literature and the “network compass” [Schneider, F., T. Tribaldos, C. Adler, R. O. Biggs, A. de Bremond, T. Buser, C. Krug et al. 2021. “Co-Production of Knowledge and Sustainability Transformations: A Strategic Compass for Global Research Networks.” Current Opinion in Environmental Sustainability 49: 127–142. https://doi.org/10.1016/j.cosust.2021.04.007] were used ex-post to identify and map fields of action and associated potentials and challenges. The process included joint problem understanding and building relations, visioning and creation of roadmaps, targeted collaboration and horizontal learning. This paper suggests that future research-practice collaboration on NBS should focus on relational capacities and communicative skills, and integrating joint reflection and learning as central components for co-producing knowledge. Furthermore, transdisciplinary collaboration requires facilitation and management skills, which should be considered an area of expertise and not taken for granted.


Introduction
Solving real-world complex societal challenges has led to an increased focus on transdisciplinary (TD) approaches and collaboration across the research-practice divide and co-production of knowledge (Muñoz-Erickson, Miller, and Miller 2017;Norström et al. 2020;Schneider et al. 2021).This has been specifically addressed in the context of renaturing cities through the implementation of the recently introduced policy umbrella concept of nature-based solutions (NBS) (EC 2015;Nesshöver et al. 2017), which requires collaboration between stakeholders and bridging different types of knowledge for successful implementation (Wickenberg, McCormick, and Olsson 2021).Even though the demand for TD and boundary-spanning collaboration for implementing and managing NBS has been articulated in academia, the practice of such processes has so far only been sparsely covered in the literature (van der Jagt et al. 2019;Short et al. 2019 ;Wellmann et al. 2022).Substantial knowledge gaps still exist on implementation and action-oriented knowledge on NBS (Kabisch et al. 2016;Mendes et al. 2020;Wickenberg, McCormick, and Olsson 2021), including in-depth understanding of NBS implementation as a process (Dushkova and Haase 2020) for which research-practice collaboration is essential, but also challenging and lacking well-established methods.This warrants further engagement in, and reflection on, such collaborative processes of knowledge production for implementing NBS.This is relevant for future planning and governance of NBS, and more broadly for building transformative capacity for urban transformations (Frantzeskaki 2022).
NBS are currently being promoted as alternative solutions that can replace or complement conventional "grey" infrastructure (Eggermont et al. 2015;Keesstra et al. 2018), alternatively serve as "hybrid" blue-green-grey solutions (Cohen-Shacham et al. 2019;van der Jagt et al. 2020).NBS is an umbrella policy concept for similar green concepts (Dorst et al. 2019;Hanson, Wickenberg, and Olsson 2020), and can also be seen as a boundary concept (Hanson, Wickenberg, and Olsson 2020) with potential to span disciplinary, sectoral and knowledge boundaries.Earlier academic work has focused on various concepts for sustainable development as "boundary objects" (Star and Griesemer 1989), or "boundary concepts" (Gieryn 1983).As a boundary concept, the broad and open character of the NBS concept leaves room for interpretative flexibility (Dorst et al. 2019) which allows for experimenting and innovating with new forms of problem-solving and knowledge production aimed at advancing NBS in cities. Drawing on the same pool of literature, that is, on boundary objects (Abson et al. 2014;Opdam et al. 2015;Schleyer et al. 2017;Star and Griesemer 1989), TD partnerships or learning alliances (van der Jagt et al. 2019), for the translation and implementation of NBS, can be understood as boundary objects; the actual platforms for interaction across the research-practice divide which enable boundary-spanning reflection and learning.
This article seeks to provide reflections from within a research-practice collaboration on NBS as a TD boundary-spanning process.The aim is to reflect on the process and contribute with insights and learning lessons for future implementation of NBS, with a focus on the opportunities and challenges of local partnerships for collaboration, learning and knowledge production.This aim has been underpinned by the following inquiries: How can the TD process be described?What elements, steps and types of activities does a TD process include?What insights about collaboration and co-production of knowledge can be identified and reflected upon?What are the challenges and potential rewards of TD collaboration?What do these insights and lessons learnt imply for future practice and research?
I have a background as an urban planning practitioner, and now engage in research on NBS implementation and sustainable cities.As such, I see myself as a "reflective practitioner" (Schön 1984) with an interest in how cognitive, normative and practical knowledge perspectives can merge into action-oriented knowledge for urban transformations.Between 2017 and 2021, I participated in an Urban Regional Innovation Partnership (URIP) in Malmö, Sweden, which was part of the research project Naturvation, 1 and involved local stakeholders from public authorities (local, regional, national), public/private sector organisations and companies (e.g.consultants, housing companies) and various researchers from Lund University.The project sought to develop an understanding of NBS innovation and governance as a response to societal challenges.
This article focuses on the collaboration process and challenges around understanding NBS as a response to complex societal challenges and identifying pathways for advancing NBS implementation in a local context.It adopts a normative and pragmatic approach, that is, it regards co-production as a process of deliberate collaboration across actor and knowledge divides towards solving societal challenges, and reflects on the steps, actions and challenges in such a process.The objective is to learn through reflection.The methodological approach is inspired by participant observation (Spradley 2016) and "embedded research" to provide inside-perspectives and reflections on the process.This article found ample inspiration from Mattor et al. (2014) who analyse and discuss TD research based on experiences from a two-year process around initiatives to change environmental governance in the Intermountain West region in the United States.Like Mattor et al. (2014), I base the reflections on my own observations from within the process of a local partnership for innovating with NBS, which included, for example, project meetings, dialogues, workshops and site visits.To structure the ex-post mapping of the knowledge co-production process, and to support the analysis, I use the "network compass" (Schneider et al. 2021).

Frames for reflectiontransdisciplinary research and boundary concepts
The reflections in this article draw on two streams of literature.Primarily, it draws on transdisciplinary (TD) research (e.g.Pohl and Hadorn 2008), to reflect on the collaborative process of research and practice engaging in learning and knowledge co-production and the associated challenges and potentials of that.Second, the article draws on recent literature on boundary concepts (e.g.Abson et al. 2014;Opdam et al. 2015), to capture the boundary-spanning nature of NBS as the policy concept which underpins the collaboration process; both in terms of boundary objects (the URIP platform) and boundary concepts (NBS).

Transdisciplinary research
TD research is understood in this article from the perspective of research-practice collaboration, and in relation to integrating and implementing NBS.Some of the main characteristics of TD research include the following aspects.It spans disciplinary, departmental and sectoral boundaries to overcome problems related to compartmentalisation (Pohl and Hadorn 2008).It is typically undertaken in the context of application (Lemos and Morehouse 2005) and focuses on the importance of collaborative and reflexive approaches across boundaries to commonly understand and address societal challenges, design a joint work process and co-produce knowledge (Hadorn et al. 2008;Lang et al. 2012;Wiesmann et al. 2008).In the context of NBS, it can promote implementation through generating actionable knowledge (Albert et al. 2019).In summary, problem-focus, collaboration, reflexivity, practice-orientation and applicability of the co-produced knowledge, are key words that describe the TD approach.
Furthermore, TD research integrates knowledge through iterative processes of mutual learning (Lemos and Morehouse 2005), thereby seeking to increase the capacity and ability to address real-world complex problems (Hadorn et al. 2008).Collaborative learning and reflexivity therefore lie at the heart of the TD research approach (Mascarenhas et al. 2021).Furthermore, it uses processes of social innovation as a basis for addressing human-nature linkages with the aim of increased resilience (Folke et al. 2005), which in turn can be related to the adoption and translation of NBS, as in the context of the process followed in this article.
From the literature, it is evident that TD research and working across research-practice divides also come with a number of challenges.For example, the application of TD approaches involve time-consuming processes (Wiesmann et al. 2008), and requires continuum among involved actors to avoid loss of momentum and disrupted learning (Kiss, Wickenberg, and McCormick 2021).Furthermore, it requires communication skills for translating key concepts and vocabularies across professional boundaries, as well as interpersonal skills and facilitation management to process and negotiate how problems are understood (Winowiecki et al. 2017).Other challenges relate to academic standards and traditional modes of quality control by and within established academic communities, for example, peer-review journals, publication standards, professional conferences (Lemos and Morehouse 2005), as well as lack of adequate, agreed-upon criteria to evaluate the impact of TD research processes (Hansson and Polk 2018).
Characterised by learning, knowledge production and action, TD research is thus more of an approach than theory.It is process-oriented and focuses on collaborative and reflexive approaches across boundaries to commonly understand and address societal challenges, design a joint work process and co-produce knowledge (Hadorn et al. 2008;Lang et al. 2012;Wiesmann et al. 2008).In that context, TD co-production of knowledge is seen as "iterative and collaborative processes involving diverse types of expertise, knowledge and actors to produce context-specific knowledge and [identify] pathways towards a sustainable future" (Norström et al. 2020, 183).In the specific case of this article, the TD approach involved a process of collaboration between research and practice to translate the NBS policy concept into knowledge and actions at the municipal level of urban planning.Here, as a reflecting practitioner and researcher, my intent is to describe what these concrete actions and activities entail and what can be reflected upon based on that.

Boundary concepts
Boundary work as a theory (Gieryn 1983) has been typically used to describe demarcations between science and practice or other social systems (Barth 2000).In contrast, recent academic work has focused on various green concepts for sustainable development as boundary objects (Abson et al. 2014), or boundary concepts (Opdam et al. 2015;Schleyer et al. 2017), and their ability to make sense to actors across different disciplines and/or sectors (on the distinction between these related terms see also Hanson, Wickenberg, and Olsson 2020, 2-3).A boundary concept is characterised by being "a loose concept, which has a strong cohesive power" (Allen 2009, 35), for which "cohesive" refers to the ability to unite diverging views and create agreement (Pollitt and Hupe 2011).However, the NBS literature also highlights the fragmenting power of the NBS boundary concept (Hanson, Wickenberg, and Olsson 2020) which can lead to competing narratives (Melanidis and Hagerman 2022).
Against this background, it is interesting to notice that the NBS concept has been described in terms of a boundary concept, in that it may be more accessible for actors less familiar with ecological and nature-based thinking (Dorst et al. 2019;O'Sullivan, Mell, and Clement 2020).In Dorst et al. (2019, 5) own words, "NBS offers interpretive flexibility with scope for reflection yet provides a solid enough foundation for different actors previously lacking a common language to work together."Seeing NBS as a boundary concept having an open and "loose" character, with potential to bridge stakeholders across disciplinary and sectoral boundaries (De Vreese et al. 2016;Hanson, Wickenberg, and Olsson 2020), it can also be described as a concept that implicitly "mandates" transdisciplinary approaches (Nesshöver et al. 2017) for translating and implementing NBS in local contexts.
In the context of this article, the local partnership (URIP) which I observed, can be described in terms of a boundary object, that is, a platform for collaboration between research and practice for learning and gaining knowledge on NBS as a new policy concept and intentional urban planning approach (Connop et al. 2016;Kabisch et al. 2016;Pauleit et al. 2017) for just and equitable naturebased transformations (Cousins 2021;Sekulova et al. 2021), while not necessarily representing new "technology" (Pathak et al. 2022).Consequently, the process that this article reflects on, embodies boundary (i.e.bridging) qualities in two ways: (a) through the URIP platform for learning across disciplinary and sectoral boundaries, and (b) through NBS which open up for collaboration and interpretation across different types of knowledge (cognitive, normative and practical).
To summarise these frames for reflection, NBS has boundary characteristics which "mandates" the use of TD approaches that aim to span cognitive, normative and practical knowledge boundaries across disciplines and sectors.This entails challenges with regard to cross-boundary collaboration, and more specifically, how to achieve a collaborative process for overcoming barriers to NBS implementation and solve societal problems.Since NBS is a relatively novel concept and planning approach, and real-world application has only started to proliferate, it is relevant to reflect on this type of collaborative process.These reflections can be used as input to future TD efforts when implementing NBS and, more broadly, to support urban nature-based transformations towards sustainability.

Methodology and approach
This article adopts a qualitative research approach inspired by participant observation (Spradley 2016).In the vein of ethnographic research, I take the position of the "embedded researcher" who takes an active part in the process while simultaneously making observations from within the process (Mattor et al. 2014).Observations and grey literature have been used to map and understand the process, which then served as a basis for analysis and reflection.

Embedded research
Participant observation has been described as interactionism, with pragmatist emphasis on practice (Rock 1979), and involves, for example, spending time working with people to understand their actions in a specific context (Laurier 2010).The method departs from my own role as a researcher embedded in the process.My observations focused on actors and the components, themes and challenges encountered in the collaboration process.My role as a participating researcher included different tasks and activities: taking an active part in the URIP process as any other participant; taking part in the local research team and discuss other research tasks related to the overall project (e.g.case studies, progress reports, outreach); act as local researcher coordinator, a role which rotated between a handful of the involved researchers and consisted mainly in coordinating research activities to ensure process alignment with the other five URIP platforms (Barcelona, Györ, Leipzig, Newcastle, Utrecht); taking meeting notes and writing reflection reports.I participated in the URIP process (almost) throughout the whole duration of the project (2017-2021).Within the context of the Naturvation project consortium, informed consent was obtained from all project partners, acknowledging participation in research activities and associated outputs.The manuscript does not include any sensitive personal data as defined by the EU General Data Protection Regulation (GDPR), nor causing harm or burden to the research participants following the Swedish Ethical Review Act (2003:460).To ensure anonymity, individual participants are only mentioned by their function in the project.

Empirical material
Participant observations and notes from within the process, along with the use of grey literature, for example, formal meeting reports, meeting notes, URIP-related project reports and guidance documents, and presentation and workshop material, have been used to retroactively map the URIP process and identify fields of action and their sub-actions/activities.The project included four meetings per year; each meeting planned by the city URIP leads with support from the local research partners.A total of 13 meetings were organised, some of which included site visits to various locations in the city.The meetings lasted between three and five hours each and convened between 5 and 18 participants (11.5 on average).

Data analysis
The empirical material was analysed through applying the "network compass" (Schneider et al. 2021) as an ex-post method to map and understand a process.The compass defines generic fields of action for fostering co-production of knowledge for sustainability transformations.The authors (2021) apply their compass on a global scale to investigate the ways in which sustainability-oriented research networks engage in co-production of knowledge.Here, the compass is applied on a European project network, more specifically on the local URIP as a sub-network.For the purpose of this article, "supporting the network community in co-production" (action field 2 in Schneider et al. 2021), was used to visualise the network and participating actors.Then, the compass was used as inspiration to identify fields of action and subactions within the URIP process.These were framed around the main phases and steps of the mapped process.Finally, based on literature and observations, the associated potentials and challenges related to each sub-action were identified (see Table 1).This served as a basis for the concluding reflections which go beyond the compass method and focuses on what needs to be addressed in future research-practice collaboration on NBS; reflecting the broader discourse in the TD research literature.

Background and process
The Naturvation project (funded through Horizon2020) sought to develop an understanding of what NBS can achieve in cities, examine how innovation can be fostered in this domain, and contribute to realising the potential of NBS for responding to urban sustainability challenges by working with communities and stakeholders.The project involved 14 institutions across Europe in the fields of urban development, geography, innovation studies and economics, including 6 cities (Barcelona, Györ, Leipzig, Malmö, Newcastle, Utrecht) which were all convening urban-regional innovation partnerships (URIPs) which included further local/regional partners and sought to provide local insights on working with NBS (Figure 1).
Here, ICLEI (Local governments for sustainability; a global network for local and regional governments) acted as a network support entity and coordinated all URIPs.An additional support entity was PBL (autonomous research institute/environmental assessment agency) which coordinated the streamlining and evaluation of the TD research process at the project level through providing specific guidelines and report templates for process reflection to all URIPs.It should however be noticed that these support functions were not added until after the project had already started and thus not part of the process from the beginning.The template reports included the evaluation criteria inclusiveness, equity, consistency and flexibility, specifically tailored to capture the TD research process (cf.Basta et al. 2021).These evaluation criteria are not in focus in this article, which is primarily interested in how the activities of the local TD process and the associated opportunities and challenges with regard to research-practice collaboration were experienced.
In the URIP, two planners from Malmö municipality acted as local URIP leads which convened and coordinated the local network, with support from the local research coordinator.The URIP convened researchers from Lund University, and various local urban practitioners representing public/private organisations and companies (at local, regional and national levels), knowledge institutes, consultants and experts.In total, the network included around 20 participants.

Joint understanding and building relations
The URIP process can be described through four main fields of action and related activities.The first field of action consisted in building relations and jointly understanding challenges, which included establishing the partnership, connecting the actors and hosting a series of workshops for a joint understanding of NBS, and associated implementation challenges in relation to the specific local context.

Visioning and creation of a roadmap
The second field of action, visioning and creation of a roadmap, consisted in activities to create a storyline and a common narrative to capture the why/what/where/who/how of integrating NBS.To concretise the work, a roadmap with three thematic priorities was created: mapping of existing ecosystem services, using NBS as a compensation for lost ecological/natural values, and valuation of existing and compensational NBS.For some of these steps, knowledge was available, while some can be considered more innovative, that is, looking to test new ideas to advance new knowledge.Further activities included the selection of specific NBS cases, where the city made the choice of addressing two large-scale development districts, which were in the planning pipeline at that moment, and for which land allocation agreement contracts were seen as a "window of opportunity" to integrate NBS at an early stage of planning.

Targeted collaboration
The third field of action concerned targeted collaboration, which could be described in terms of targeted spin-off activities involving the URIP lead and a selection of network partners.This phase of the project saw the creation of a process mapping tool, which was required for the thematic priorities identified earlier in the process, and was done in collaboration between the municipality and some of the network members.Further, a local exhibition on NBS was developed along the planning of outreach and communication activities.Another activity consisted in (additional) stakeholder inclusion and establishing relations with a large developer in one of the selected cases.The aim was to engage the developer in different activities for learning and knowledge exchange, to prepare the ground for implementation of NBS when the property was to be developed.

Horizontal learning
The fourth field of action included horizontal/cross-URIP learning, for example, a workshop in Bonn for testing an NBS business model puzzle, learning about public participation methods and coworking on a concrete NBS case from one of the other URIPs.Another example includes the convening of all six URIPs in Malmö to test the puzzle together with local stakeholders of the Malmö URIP, as well as exchange knowledge and practitioner perspectives across the URIPs, for example, through study visits and workshops.
The Covid-19 pandemic then put a halt to planned activities for the final year (e.g.exhibition, outreach, further targeted collaboration with the developer), with a resulting loss of momentum.A few online meetings, including the final project conference, were organised for the remainder of the project, but did not reach the same level of interaction (Figure 2).

Joint understanding and building relations
At this first step of creating joint understanding of the societal challenges in Malmö, it was easy to relate these to self-experienced problems and impacts from climate change due to recent flooding events in the city (the Arvid storm on 31 August 2014) and associated societal costs.However, it was more difficult to define and address challenges related to internal organisational structures of the project and the roles of both researchers and practitioners in relation to the wider project context.At this early stage of the process, the URIP was focused on how to integrate NBS into the planning process, that is, it was largely perceived as a planning problem.This can be seen as a natural result of the municipality leading the process and their own perceived knowledge gaps at the time (e.g.lacking indicators for assessing ecosystem services, difficulty of identifying needs).It can also be seen in light of other recent NBS-related projects in the city, that is, there was a lot of prior knowledge and understanding from previous projects on ecosystem services (ES) and blue and green infrastructure (BGI); a knowledge legacy which was quickly incorporated into the project.From the perspective of TD process and the relevance of opening up the process of inquiry, setting the scene for long-term commitment and collaboration, and exploring various stakeholders' perspectives in the problem formulation, this continuation of earlier processes to keep momentum can however be seen as a challenge.While it saved a lot of time, the focus on physical planning and solutions may have impeded important questions/discussions, for example, around needs (who's needs?) and potential benefits (benefits to whom?) which has been highlighted by Cousins (2021), and costs (who will/should finance?), as well as deeper considerations of the URIP process itself, for example, from the perspective of collaborative learning and knowledge production.
It was also clear from this first phase of the process and initial workshops, that there was uncertainty around how to define NBS.What type of solutions should count as NBS? Was it to be seen as yet another concept for green space planning, and in what way did it then differ from other concepts used in urban planning (e.g.ES and BGI)?These definitional problems partly resulted from researcher perspectives, and the eagerness to define and understand a novel concept lacking a clear definition.In retrospect, one could argue that the name of the concept, with its focus on "solutions", may have skewed a wider discussion of the concept, i.e. not only around types of solutions but also including aspects relating to just governance and implementation of green space through social inclusion and participation processes (cf.Sekulova et al 2021), even if some of these aspects were touched upon (e.g.challenge-orientation, cost-efficiency, user groups, health, NBS as concept to attract the business sector).Much later in the process, this conceptual confusion came to an end, at least partially: "The ecosystem services concept can be used to analyse the need for NBS, and vice versa, NBS provide the answer to, and the concretization of, ecosystem services."(Local URIP lead, cross-URIPs workshop in Malmö, 2019)

Visioning and creation of a roadmap
Although the first phase of the process emphasised the use of tools and indicators for assessing NBS, that is, a rather technical focus, the second phase can be understood as influenced by the project guidelines for creating local visions, storylines and roadmaps.This envisioning phase saw joint study visits in the city, high level of commitment and interaction at the URIP meetings and finally led to a "window of opportunity": the idea to work with NBS in the planning process by integrating them in new development plans.Through joint brainstorming, the idea was for the URIP to generate inquiries and help specify requirements to be used in the planning process.The URIP thus served as an innovative, transdisciplinary support forum outside the formal planning process.
To concretise the testing of the NBS concept, a roadmap with three thematic priorities was created.However, this part of the process was largely owned by the municipality, and the role of the partnership collaboration was more actively reflected upon and discussed here.The challenge was how to create a balance between the expectations on an innovative process and the realism of planning, that is, how to keep momentum in the collaboration and innovation efforts while moving closer to the formal (and more closed) planning process.Here the solution was to tie continued innovation efforts to concrete tasks needed for the process ahead, that is, demanded by the thematic priorities (mapping of existing ES, using NBS as compensation for lost ES values as a consequence of new development plans, valuation of existing and compensational NBS), thus leading to a new phase in the process.

Targeted collaboration
This phase of the process was marked by tangible action towards real impact.However, participants engaged in parallel activities, meaning that all URIP members were not involved in the same process(es).Collaboration momentum was lost at some ends, while gained at other ends.For example, some of the city partners focused on specific geographic areas and current detailed plans to concretise experimentation and implementation of NBS, including how to best integrate these in established planning processes.At the same time, (we) researchers engaged in, e.g.collecting material to develop a database with NBS cases from different European cities to find inspiration and good examples to learn from on the social, environmental and economic benefits of NBS, as this was perceived as valuable yet lacking knowledge by the city.Other collaboration activities related to, for example, developing exhibition and outreach materials.The most prominent example of targeted collaboration involved the city and some of the urban practitioners/ experts in developing a process mapping tool to improve the integration of NBS in the planning process.
Thus, in terms of research-practice collaboration, this phase was challenging.The local network process had started developing its own context-specific rationale, which was not always coinciding with the planned research process at the general level of the project.As a whole, the URIP process can be seen as productive and providing room for knowledge exchange and networking.However, the question on what common learning and knowledge outcomes were generated, remains largely unanswered.

Horizontal learning
The inclusion of a variety of different stakeholders in the URIP had been a known and discussed challenge from the start, when a majority of the participants were either city partners or researchers.Inputs from the business sector and NGO's were identified as missing in the group.The roadmap and focus on development plans for NBS integration, provided an opportunity to expand the partnership and include a new stakeholder: the land-owner/developer who was identified as a key stakeholder to implement NBS.Here the idea was to make constructive use of the URIP to advocate the NBS concept as a potential for creating multiple benefits, for example, through a joint URIP meeting hosted by the developer, and through inviting the land-owner to a cross-URIP workshop to discuss and exchange experiences with other European network partners.This included the testing of an NBS business model puzzle (developed by researchers in the project) to engage with NBS and learn more about benefits and costs of NBS, and what potential further stakeholders to include.An interesting outcome of this step, was that it resulted in what could be called "spin-off co-production" with the developer, which led to outreach and communication events in the selected city district (on the property to be regenerated).However, a reflection here, is that the focus on, and inclusion of, a new stakeholder may have resulted in a decreased interest and commitment by other network participants as their roles became less clear in this phase.

General challenges
TD collaboration is demanding.It requires a balance between flexibility and clear roles and ownership, while continuously including reflexivity and learning in the process (Knickel et al. 2019).Throughout the URIP process, these components were sometimes unclear.In part as a result of a large-scale research project with many stakeholders and functions/tasks to be fulfilled and difficult to overview, with challenges related to balancing the needs and objectives of the larger project versus those of the local URIPs.Here, the coordinating work by the network support entity (ICLEI) was important to support internal project alignment and balancing these different needs.Hence, in this case, the success of the local collaboration process is thus also dependent on the capability of the larger network to structure and govern the TD research process, e.g. through providing a framework and guiding criteria for the process, for example, flexibility, reflexivity, inclusiveness, transparency, yet being flexible enough to cater for the needs of the local networks.Another general challenge relates to process ownership and the high expectations on clear communication and level of inclusion which follows from that.Thus, communicative skills and relational capacities are essential, especially considering the already high degree of complexity and uncertainty involved in urban planning and development (Table 1).

Reflections and conclusions
The point of departure for reflecting on the URIP process is that NBS "mandates" a TD approach, which aims to span diverse types of knowledge and disciplinary/sectoral boundaries to solve societal challenges, yet being a challenging process.The key conclusions from this reflection article are that research-practice collaborations require new competences; soft skills are hard to measure but vital; blurred and flexible roles calls for continuous reflection; and, education and hiring for transformation can pave way for building transformative capacity.

Research-practice collaboration requires new competencies
Boundary concepts as a probe serve to understand the need for collaboration across disciplinary and sectoral boundaries, and across different types of knowledge (cognitive, normative and practical).Thus, what NBS as a boundary concept "does", is that it requires actors to convene in a TD process.However, it mainly captures research-practice collaboration as static.Here, TD research helps to understand the iterative nature of learning and knowledge production processes.
In many respects, the URIP process aligns with how the TD research approach is depicted in literature (e.g.Hadorn et al. 2008;Lang et al. 2012;Wiesmann et al. 2008).The process included four fields of action: joint problem understanding and building relations, visioning and creating a roadmap, targeted and action-oriented collaboration activities, learning and knowledge co-production.The partnership actors engaged in joint translation of conceptual ideas into planning and governance practices, through creating an understanding of how these fit with the local context and how they can be integrated in existing processes of urban planning.Consequently, at large, the URIP process has followed what Westin et al. (2014) call an inquiry-based process with cycles of action and reflection, enabling participants to critically engage with ideas, conceptions and assumptions.The process aims to create activities that "open up", that is, broaden the perspectives, and "close down", i.e. selecting, prioritising, coordinating and making decisions about directions.This indicates that the TD process needs to follow a method, which in turn requires specific facilitation skills to enable reflexivity and ensure that the learning process is a collaborative effort (Pohl et al. 2010).
As highlighted by Oliver et al. (2021), sustainability challenges give rise to new competence needs, for example, the need to increase the capacity for TD learning and knowledge production.Thus, reforms are required in both research and practice to meet these needs.This highlights that research-practice collaboration around NBS is, ultimately, a question of having adequate competency and skills, which must be acknowledged and addressed to work effectively towards TD collaboration on sustainability-oriented transformation processes.

Soft skills are hard to measure
The cross-boundary collaboration between a sub-set of the partnership actors to create and experiment with a process mapping tool, demonstrates the concrete value of the platform collaboration.It paved way for a process (within the process) of inquiring the standard planning process and opening up for new ways of seeing and doing things.In other words, it generated a "seed of transformative learning" (Wickenberg et al. 2022).Alternatively, from a boundary object perspective, the URIP thrived on the potential to create a collaborative and discursive space for actors with different knowledge (Opdam et al. 2015).Similarly, Xie et al. (2022) highlight the importance of private-public partnerships and creating intermediaries to transgress institutional silos and generate knowledge on how to integrate and implement NBS.
While this exemplifies a direct impact of the TD process, it is important to be aware of the different types of output created, that is, the difference between tangible/direct output in the short term (e.g.tools, events) versus less tangible/indirect output with potential impact in the longer term (e.g.learning, knowledge exchange, openness and flexibility).These outputs are more difficult to measure, but constitute important practical TD skills and capabilities (O'Donovan, Michalec, and Moon 2022) which comprise essential building blocks in processes of transformations; these are outputs that are hard to measure, but help create conditions for future cross-boundary collaboration (cf.Hansson and Polk 2018).In the URIP, this became evident through local partnership actors continuous engagement in knowledge sharing, discussing examples of NBS projects across public/private sectors and jointly reflecting on the challenges and potentials for advancing knowledge and implementation of NBS.This relates to the broader perspective of urban transformations and the potential role of engaged research-practice partnerships for catalysing change; "co-production is one pathway to develop spaces for learning and cross-institutional reflection" (Perry and Atherton 2017, 2), and also, for building long-term capacity for urban transformation.

Blurred and flexible roles call for continuous reflection
From a researcher perspective, TD research means balancing the roles of the researcher and the committed participant in the co-production process.It is easy to get carried away in either direction, and it can be challenging to stay true to the role of the researcher, especially as sustainability-oriented research is normative and action-oriented.In my case, this was further challenging considering my prior experiences as a solution-focused urban planner.According to TD research literature, flexibility is a key criteria in these processes, which is useful to remember also for researchers.The sometimes "blurred" roles in the process, which may occur when common goals and the collaborative process override the disciplinary/sectoral interest of individual participants, require flexibility, individual and collective reflexivity, and interest in contributing towards social learning, although the benefits for the individual might be unclear at any given point in the process.Navigating complex urban planning processes may be perceived as "messy" and difficult.Here, flexibility is helpful.However, this also emphasises the need to have a structured TD process in place, which ensures reflexivity to handle the "messiness" and uncertainty.Ensuring that these TD qualities (i.e.flexibility and reflexivity) are included and balanced in the process, requires a solid foundation of TD research skills and capacities.Here it can be useful to take on different roles for the researchers involved; the facilitator, the intermediator/knowledge broker and the self-reflexive researcher (Mascarenhas et al. 2021).This will likely make both researchers and practitioners feel less disoriented, and more willing to invest time and resources in collaborative partnerships.
Collaborative learning and knowledge production are the potential that resides in TD processes; the key to unlock transformative power.However, without a clear focus on the process, and explicitly including the learning component and continuous reflection (including self-reflection) along the process, TD may become a "blind" and less valuable process.TD learning and knowledge production are argued to depend on the personal and disciplinary flexibility of the stakeholders involved (Lemos and Morehouse 2005).However, it is equally dependent on skills, capacities and methods for facilitating and managing the TD process, thus providing a common structure and direction.
In future TD processes, it seems important to address these methodological challenges as early as possible, before the TD process starts, and continuously, and collectively, reflect about the opportunities and challenges of the process to foster a learning process (cf.Knickel et al. 2019;Mascarenhas et al. 2021;Ness and Wahl 2022).This reflexivity should be considered a key "process in the process" to support participants navigating the challenging but potentially rewarding waters of researchpractice collaboration.

Education and hiring for transformation
Challenges still remain concerning the legitimacy and "normalisation" of TD research (and associated methods) as a valuable approach for advancing urban planning and governance, and the skills and capacities needed to facilitate and manage TD processes, for example, increased relational and cognitive/emotional capacity (cf.Wamsler et al. 2020).Here, a relevant question is whether we can simply expect from urban actors and planners, with valuable expertise in diverse fields, to be "natural borne" and have these capacities and skills, or, if these competencies must be acknowledged as an area of expertise in itself, which universities and cities need to increasingly educate and hire for.Based on the URIP experience, and the challenges around facilitating and managing a "good" TD process, i.e. transparent, flexible, reflexive and equitable, with direct/indirect transformative impact, I strongly argue that this is an area of expertise in its own right.Thus, we need further training, education and experimentation to continue developing specific skills and capacities for facilitating and managing transdisciplinary and transformative learning and knowledge production processes (cf.Frantzeskaki 2022;Hölscher and Frantzeskaki 2021;Wolfram et al. 2019), which can translate into real shifts in practice (e.g.O'Sullivan, Morell and O'Connor 2016).Continuing developing capacity for cross-boundary learning and co-production of knowledge thus seems essential for scaling up the integration and implementation of NBS in cities, and for urban transformations more broadly.

Recommendations for research and practice
In conclusion, the URIP served as a platform for exchange of knowledge and experiences between different stakeholders.It provided a "safe space" to explore NBS and its potential application, challenge existing planning norms and routines, and, through an innovative planning tool, integrate it into the complex process of urban planning and development.Though, this last part of the process became less clear due to Covid-19 which resulted in a loss of momentum regarding network activities, continued reflection and learning and potential societal impact.Here, TD literature has highlighted the relevance of the point of closure (cf.Pohl et al. 2017) which is important for learning purposes; the final self-reflection, both from individual participants and jointly on the impact of the URIP, which was left hanging in the air.In future collaboration on NBS, it may seem even more important to further integrate the TD research approach, throughout the whole duration of the process, e.g. by emphasising continuous reflection around the collective learning process (see Figure 2 and Table 1).
I have been embedded in a process of research-practice collaboration on NBS and learnt about some of the associated challenges and potentials.As a reflective practitioner and researcher with an interest in how to advance NBS and urban sustainability transformations, I suggest that the following aspects of TD collaboration need further attention to bring research and practice closer in future collaborations on NBS: Building relations for TD collaboration through trust, good communication and flexibility requires relational capacities and communicative skills; learning needs to be explicitly acknowledged as a central component for co-producing transformative knowledge, and as such, deserves due consideration and continuous joint reflection throughout the whole collaboration process; and, specific skills and methods for facilitating and managing the process of TD co-production of knowledge are required and should be considered an area of expertise and not taken for granted.

Figure 1 .
Figure 1.Fostering the network community in co-production.Schematic illustration of the local URIP network and its actors in relation to network support entities and other local URIPs.Adapted from Schneider et al. (2021).

Figure 2 .
Figure 2. Overview of the Malmö URIP process: fields of action (white boxes), sub-actions (grey boxes) and the cyclic reflection and learning (bold arrows).

Table 1 .
Fields of action, activities and potentials and challenges.
Schneider et al. (2021)ider et al. (2021).Reflexivity and learning as a cross-cutting theme throughout the process.