How Sharing Can Contribute to More Sustainable Cities

<jats:p>Recently, much of the literature on sharing in cities has focused on the sharing economy, in which people use online platforms to share underutilized assets in the marketplace. This view of sharing is too narrow for cities, as it neglects the myriad of ways, reasons, and scales in which citizens share in urban environments. Research presented here by the Liveable Cities team in the form of participant workshops in Lancaster and Birmingham, UK, suggests that a broader approach to understanding sharing in cities is essential. The research also highlighted tools and methods that may be used to help to identify sharing in communities. The paper ends with advice to city stakeholders, such as policymakers, urban planners, and urban designers, who are considering how to enhance sustainability in cities through sharing.</jats:p>

section_content: Sharing can be viewed as a means to reduce the carbon and resource intensity of cities. As [1] points out, the more a resource is used or shared, the lower the environmental impact (e. g., car-pooling with four people is four times more efficient than four, single-occupant trips). In fact, scholars have suggested that, 'building a sharing infrastructure and culture is quite simply one of the most important things cities can do to contribute to a fair and sustainable world' [2] (p. 23). 

Despite this claim, the scholarly literature that examines how a city can achieve or facilitate sharing is fragmented and thin. Much exposure surrounds the sharing economy movement [3, 4], expounding its potential economic benefits on cities [5] alongside its legal implications. There also is an enormous amount of grey literature on the potential size, benefits, and disadvantages of the sharing economy, largely due to the emergence of Web 2. 0 initiatives that provide a platform to enable users to connect, contribute, and exchange content (According to [6], the sharing economy will be a $670 billion dollar industry by 2025). The UK government has welcomed the entrepreneurial output of the sharing economy, describing the 'emergence of the everyday entrepreneurs. They are the challengers, the innovators and the agitators-constantly seeking to shake up the market by solving other people's problems' [7]. 

While the sharing economy offers potential to cities and their citizens, we argue that it is only one mechanism through which sharing is, and could be, enacted in a city. The sharing economy presents a very narrow view of the potential of sharing to contribute to more sustainable cities. To that end, this paper proposes to do two things: (1) From a conceptual perspective, the background literature aims to outline how sharing as a principle could be utilized in different domains to enhance the sustainability of a city; (2) From a practical perspective, the use of co-design workshops aims to help explore the current state of sharing in cities and how it could be strengthened. The insights gained from these two perspectives enabled us to consider how the broader notion of sharing may be advanced by policy makers, urban planners, and urban designers.
section_name: Introduction

section_name: Background

section_content: Put simply, the sharing economy may be viewed as an economic model wherein people borrow or rent assets owned by someone else [8]. Inherent in this definition is that the sharing economy is a social and economic system, constructed around the sharing of human, physical, and intellectual resources [9]. In this respect, the sharing economy encompasses shared creation, production, distribution, trade, and consumption of goods and services by different people, groups, and organizations. Fundamental to how the sharing economy works is its use of online platforms, web-based services, information and communication technology, and 'social commerce' that give people shared access to things, such as resources, time, and skills [10] [11] [12] [13]. Emphasis also is placed on the potential for high-impact capital within a largely market-based approach that favors networks over centralized hierarchies and the blurring of lines between personal and professional, full-time and casual labor, and independent and dependent employment [14]. 

In explaining the different types of activities that encompass the sharing economy, [15] uses four categories:
section_name: Describing the Sharing Economy

section_content: Re-circulation of goods: taking unwanted goods and selling or giving them away via online marketplaces. Examples: eBay, Freecycle.
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section_content: Increased utilization of durable assets: taking durable goods or assets that are not being used to their fullest potential and utilizing them more intensively. Examples: Airbnb, tool libraries.
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section_content: Exchange of services: bartering sites in which services are traded for other things, such as time, money, or other services. Examples: Task Rabbit, time banks.
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section_content: Sharing of productive assets: involves sharing assets or spaces that foster production, rather than consumption. Examples: Skillshare. com, cooperatives. 

Other scholars have developed typologies and taxonomies to help make sense of the sharing economy and related terms, including collaborative consumption and peer economy [10] ; mesh economy [16] ; functional-or access-based economy and asset-light lifestyles [10, 13, 17, 18] ; solidarity economy [19] ; moral economy [20, 21] ; alternative economies [22, 23] ; and gift economy, gifting, and altruism [24, 25]. For example, [10] uses collaborative consumption as an umbrella term that covers three distinct areas of sharing and which mostly overlap the sharing economy categories of [15] :

Product service systems: occurs when people pay to benefit from a product but they do not own it outright. Example: hiring a floor sander. 

Redistribution markets: these use social networks or the Internet to redistribute things either for a fee or for free. Example: eBay. 

Collaborative lifestyles: happens when people come together to share things. Example: co-housing. 

In both of these typologies, the mechanics of how things are shared remain unaddressed. Further detail is provided by [2] to consider different methods of production and consumption (i. e., communal and collective production, or co-production and co-consumption; through individual, organizational, and peer-to-peer networks). They also acknowledge that sharing requires both inputs (e. g., water) and outputs (e. g., wellbeing), and provide information about what gets shared in exchanges (e. g., materials, products, services, wellbeing, capability). Additional typologies and taxonomies may be found in the collaborative economy within the business sector [26], the public goods literature [4], spectrum sharing in the telecommunications industry [27], and food sharing [28]. These latter categorizations have introduced concepts like rivalry, or the use of a product that removes availability of that product to other consumers, and exclusivity, which involves accessing a product that can be controlled and restricted because of specific criteria placed on a group of consumers [4] ; notions of geography, temporality, and coordinated and uncoordinated rule-based sharing [27] ; and the importance of considering the modes of exchange alongside the overall mission, goal, and intended outcomes of sharing [28].
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section_content: While the sharing economy is viewed as part of a larger social system, its focus is narrow and primarily concentrated on economic transactions [29], using online platforms. Examples of the sharing economy in cities also tend to focus on global, international, or national initiatives, with little attention paid to smaller, more grassroots and hidden examples of sharing. This section examines the notion of sharing and demonstrates that sharing in cities is broader than just the sharing economy; it encompasses non-economic and communal forms of sharing as well. 

One of the most-cited definitions of sharing comes from [30] : 'the act and process of distributing what is ours to others for their use and/or the act and process of receiving or taking something from others for our use' (p. 126; see also [31] ). Implied by this definition is that sharing is a social act that takes place between at least two people. The act does not need to involve an economic exchange, but may be shaped by cultural, political, and social norms and motivations [29]. Moreover, the definition incorporates a distributive element in which something that is owned by one person may be dispersed for use by someone else [32]. 

What this definition suggests is that sharing can involve a hugely diverse set of things, services and activities or experiences that may be co-produced and co-consumed at the same time or at different times [29]. Sharing can be informal or mediated through digital or other means, and may have communal and/or commercial benefits. Sharing also can be viewed as being more than the commercialisation or marketization of assets; it involves alternative ways of knowing, valuing, and living that promotes social and spatial equality, and regards all assets as priceless (Opponents of the definition by [30] suggest that trust, willingness to collaborate, and motivation to share are not always the same and should not be assumed for those involved in an exchange (see [29, 33, 34]. Moreover, [2, 24, 29] suggest that discussing the dimensions of sharing beyond basic dichotomies might have greater utility).
section_name: Sharing is Broader than the Sharing Economy

section_content: To explore the diversity of sharing in cities, the authors, who are part of the Liveable Cities team, found examples from within their thematic research areas of aspirations, governance, and finance, ecosystem services, energy, futures, metabolism of flows, mobilities, resource use, and wellbeing (see liveablecities. org. uk for more details about the project. ). Three sets of examples are discussed below, which are situated in different themes: energy provision (energy), wellbeing (wellbeing), and food (mobilities). (A co-produced research blog of grey literature and five, thematically-based discussion papers with our examples may be found here: shareableandliveable. wordpress. com. ) The examples are illustrative of the different kinds of non-economic and communal forms of sharing that may be found in cities, ranging from smaller, more grassroots initiatives, to larger-scale, formal ones.
section_name: Examples of Sharing Alongside the Sharing Economy

section_content: Three, internationally-progressive, energy sharing examples are used to illustrate the radical business approaches that address the current challenge of reducing CO 2e emissions and utilising the latest technological advancements to create low-carbon energy infrastructure paradigms (e. g., combined heat and power, photovoltaics). Doing so has meant moving from a centralised, static model with the consumer at the heart to more decentralised, dynamic models where individuals or businesses contribute to shared resources as the 'prosumer'. 

Local authority as a charitable energy provider. Woking Council (UK) established a not-for-profit, local authority-owned energy company (Thamesway) to distribute combined heat and power to Council buildings and local customers, offering a range of business-to-business (B2B) and business-to-consumer (B2C) arrangements [35]. They also share heat and the pipes used to transport energy via a small, local grid in a defined neighbourhood. Although sharing is set up on a formal basis, the model of sharing is both top-down and bottom-up, allowing customers to engage with the local authority about the service. 

City of Sydney master plan. In Sydney (Australia), the City Council brought together a limited number of organisations that own the majority of the central business district to develop a strategic master plan to reduce drastically the city's emissions. A tri-generation (electricity and thermal energy) network formed a central element to this plan in which heat and cool air pipes would be shared via a small, local grid in a defined neighbourhood. Sharing of energy would be formal, but also bottom-up. To progress this B2B plan requires multiple changes to state and federal legislation to enable decentralised energy production and B2B sharing within the city [36]. 

Smart local grids. In Rose Hill (UK), Oxford City Council and Bioregional have experimented with storing and trading solar-generated electricity within a 30-strong, local community using rooftop-scale photovoltaics (PV), batteries, direct current (DC) appliances, and 'smart DC' technology to control the flows of power. Locally-generated energy can be stored and consumed locally within the neighbourhood, circumnavigating complicated grid upgrades and bureaucracy associated with feeding renewable energy back into the grid for an increasingly low tariff [37]. Decision-making is bottom-up and involves the whole community. 

The energy provision examples illustrate the critical role of managing stakeholders, the importance of governance and the role that new business models may play in enabling a transition to sharing resources. While sharing seems inherently positive, the disruptive nature of the 'prosumer' model needs to be managed carefully to ensure that it does not compromise outcomes that are valued from the centralised energy system, such as equity of access to energy across the population and a resilient source of reliable and safe energy able to meet demand.
section_name: Energy Provision

section_content: One example of 'sharing wellbeing' may be found in the One Brighton (UK) development, which builds on the lessons of BedZED and espouses the principles of One Planet Living [38]. (Wellbeing can be viewed as an indirect consequence of a number of opportunities that involve using shared space for different purposes, such as active commuting [39] [40] [41] [42] ; sharing work to increase economic wellbeing [43] ; and sharing experiences to increase or improve social interactions. ) Here, a range of spaces and artefacts are shared across and between residents, including rooftop allotment gardens, car club membership, and a café. While some schemes within One Brighton involve formal sharing (e. g., car club), other initiatives are more informal, such as sharing common space in the community centre. To help with general governance issues, the development has a bottom-up, appointed panel to work with the developer. Anecdotal evidence suggests that One Planet Living communities know more neighbours than in standard communities and that crime and fear of crime may reduce as a result, with suggestions of better health outcomes [38]. One Brighton demonstrates that, at the scale of the local neighbourhood or large block, concepts of sharing have been integrated via urban planning and are designed to facilitate positive lifestyles and wellbeing.
section_name: Wellbeing

section_content: Three examples of food sharing offer different ways of considering the important role of food in our lives and our mobilities (For a discussion of mobilities, see [44] ). One of the examples, Claver Hill Community Farm, was mentioned in the workshop. Urban Harvest. This example sees members of a local community in Birmingham (UK) pick fruit from trees in people's gardens. The produce is shared among pickers and growers, often for the production of jams that are circulated and shared among members. The bottom-up, largely informal process of sharing occurs at the neighbourhood-city scale and is limited to residents who have land and fruit trees, people who want to pick fruit, and the seasons. 

Claver Hill community farm. Established by local activists in Lancaster (UK) to preserve surrounding farmland and provide access to local food. Knowledge and food are exchanged for volunteering from community members. Although this is a bottom-up example, the terms of sharing are formal, between a formal trust who owns the land and community members who share time. 

Incredible Edible Lancaster (UK). A local chapter of Incredible Edible, which is a local food movement that encourages community building through growing, food education, and support for local commerce. The Lancaster branch has established, community-managed gardens in town and on the Lancaster University campus that are open for anyone to harvest. Like the previous two food examples, this one also is bottom-up; however, the arrangement is largely informal in that anyone can join and anyone can pick the food grown in the gardens and common spaces. 

The food examples broach a diverse range of concerns about the current state of the food system, such as loss of growing skills, limited access to affordable local produce, nutrition and the loss of farmland for alternate developments. The examples also illustrate the multiplicity of approaches to food sharing, with some viewed as quite niche and hidden from mainstream food practices.
section_name: Food

section_content: As can be seen from the above examples and the background literature, sharing can span a range of foci, from local to national. Sharing also involves a spectrum of bottom-up, top-down, and hybrid processes, and contains elements of digital, physical and 'phygital' [45, 46] platforms. These examples reflect the non-economic and more communal aspects of sharing [29] and sit alongside those typically discussed in the sharing economy, which tend to focus on more national, international, and global organisations that use more top-down/less bottom-up approaches (e. g., Uber, Airbnb, TaskRabbit) and to achieve a financial return on investment. They also highlight two issues about sharing in cities worth considering. 

First, sharing is not always an issue of ownership, which is central to the making and understanding of contemporary, individualistic consumer societies [47]. For example, a group of people may share a train journey, yet the train does not belong to any of these passengers. Likewise, sharing may relate to communication that is not always reciprocal: a person may share an emotion with someone else on the train, but the sharer does not, necessarily, own that emotion, nor should the receiver feel pressured into sharing an emotion in return [32]. 

Second, sharing can involve two people or many people. Sharing has a community-based orientation as well as a macro-scale orientation in the form of sharing the commons [24]. Thus, different scales of sharing occurs in cities: 'sharing in', which happens between close kin; 'sharing out' which happens outside close kin and involves other individuals, groups, or communities; and 'commoning', which involves sharing what is owned by the public or that no one owns. 

The above discussion helped us create a more nuanced picture of sharing in cities, suggesting that both the sharing economy and non-economic or communal sharing can co-exist alongside one another. We were interested in seeing if this held true in practice by exploring the landscape of sharing in two UK cities. The next section outlines our approach to the research that we undertook on sharing in cities.
section_name: Background Summary

section_content: To better understand how sharing occurs with 'on-the-ground' experts who could bring knowledge about their day-to-day sharing experiences to the research team, we conducted two workshops with local residents of the city of Lancaster and the Moseley and Kings Heath ward within Birmingham (UK). We recognise that holding only two workshops might be viewed as a limitation. However, we feel that strong messages emerged clearly from both workshops and that the findings make a valuable contribution to the scant academic literature to-date. Moreover, our research offers other researchers innovative tools and methods to take the work further. 

The workshops had two aims: (1) To map current examples of sharing to reveal what sharing looks like and how it functions in cities; (2) To consider what needs to done in cities to develop and encourage sharing whilst also improving sustainability. In order to achieve these aims, we undertook two co-design workshop activities, which are explained in the next section.
section_name: Methodology

section_content: We chose to conduct our day-long workshops in local community centres in Lancaster (in March 2015) and Moseley and Kings Heath (in September 2015) because this is where the Liveable Cities project team focused their research efforts within the UK. For Birmingham in particular, we selected a smaller area than the city scale because it would have been difficult to comprehensively map examples of sharing and consider what needs to be done to encourage sharing. Moseley and Kings Heath was chosen because Birmingham City Council was hoping to regenerate the area and considered sharing as one approach to achieving their goal.
section_name: Co-Design Workshops

section_content: Workshop participants were recruited via a locally-relevant flyer that was distributed within each city, via email and online advertisements on Facebook, Twitter, and the Liveable Cities website. The flyer invited people to a 'thought experiment' in which sharing would be debated and discussed, including an exploration of whether the boundaries of sharing could be expanded to ensure sustainability. Participants did not need to be involved in a sharing project or initiative to attend the workshops. 

Based on our recruitment, 40 participants attended the Lancaster workshop and 22 participants attended the Birmingham workshop. Given that the workshops took place over two weekdays, we acknowledge that our participants may not be representative of all residents in these areas (e. g., schoolchildren, people working during the day). Moreover, because the workshops related to sharing, we may have unintentionally excluded those people who felt as though they did not share.
section_name: Recruitment and Participants

section_content: Using co-design [48], futures [49], and social innovation discourses (e. g., [50, 51] ), both workshops involved the same two sets of activities:

1. 

Mapping current initiatives of formal and informal sharing. Upon entering the workshop space, participants were given a card and asked to write down an example of sharing. Participants then attached their card to a large piece of paper on a wall that already contained categories of sharing (e. g., sharing food, sharing knowledge); the idea was to place their card next to the category that best reflected their sharing example (see Figure 1 ). Once completed, participants shared their examples with 4-7 other participants at tables, providing more detail such as who shares, what and how is being shared, and so forth. Participants then were encouraged to make connections between their sharing examples. The research team, seated at each table, facilitated this discussion by probing for existing, missing, and potential connections.
section_name: Workshop Activities

section_content: Envisioning sharing city scenarios. This section of the workshop began with an opportunity to quickly remove negative thinking ahead of the final design activity. Participants were asked to think what could be the worst-case scenario affecting sharing in their area. They wrote their concerns down, shared it with those at their tables and put the concerns in a box, which then was hidden out of sight. Subsequently, participants were tasked with designing a future city or neighborhood that encouraged sharing. To help them out, participants were given an array of materials and tools, including colored tissue, maps, wooden blocks, miniature people, pens, and string. We also equipped participants with small signs containing the words, 'create', 'amplify', or 'destroy', inspired by the position that design for sustainability requires consideration for what futures we choose to sustain, create, or destroy [49], and the desire to 'use what exists' in amplifying promising solutions that offer potential [52, 53] (It can be argued that the notions of creating, amplifying, and destroying overlaps with the three different approaches to creating system change in cities, respectively: re-invention, subversion, and revolution [29] ). These terms were to be used when they wanted to produce something that was not currently available (create), they wanted more of something (amplify), or they wanted to remove something they currently did not like (destroy) in relation to sharing. 

amplifying promising solutions that offer potential [52, 53] (It can be argued that the notions of creating, amplifying, and destroying overlaps with the three different approaches to creating system change in cities, respectively: re-invention, subversion, and revolution [29] ). These terms were to be used when they wanted to produce something that was not currently available (create), they wanted more of something (amplify), or they wanted to remove something they currently did not like (destroy) in relation to sharing.
section_name: 2.

section_name: Results

section_content: The mapping of sharing examples from the Lancaster and Birmingham workshops is provided in Tables 1 and 2. Participants identified 41 different sharing examples that cover a diversity of themes, including: allotments, art, care, clothes, energy, food, friendship, knowledge, language, material, parks, sheds, spaces, 'stuff', time, and transport. Many of the sharing examples identified also pass as examples of creative communities [54] or social innovations [51], which have emerged through grassroots efforts (Social innovation is 'a complex process of introducing new products, processes or programs that profoundly change the basic routines, resource and authority flows, or beliefs of the social system in which the innovation occurs' [55] (p. 2)). When reviewing Tables 1 and 2, the tangible and physical nature of the sharing examples was noticeable: of the 41 examples, 33 depend on physical assets. Many of these examples are run via word of mouth, often informally and communally, and without economic exchange. In contrast, three examples identified were dependent on digital platforms to enable sharing activities to take place: Digital Schools, Freegle, and Borroclub. Of these, Borroclub-alongside Lancaster Arts City and Fair Trade Towns International-could be viewed as examples of the sharing economy, as they adopt economic models that allow people to borrow or rent assets from them. Other organisations mentioned, such as the Ethical Small Traders Association, Lancaster Community Car Club and Food Forest Brum, are Community Interest Companies; as such, they adopt a business model with primarily social, rather than purely economic, objectives [56], making them more like social innovation examples, rather than sharing economy examples. 

Finally, examples that focused on food were popular, with 23 of the 41 examples relating to, or encouraging, food sharing in some capacity, through food production or consumption. The food sharing examples broach a diverse range of concerns about the current state of the food system, such as loss of growing skills, limited access to affordable local produce, nutrition and the loss of farmland and peri-urban areas for alternative developments. The examples also illustrate the multiplicity of approaches to food sharing, with some viewed as quite niche and hidden from mainstream food practices.
section_name: What Examples of Sharing Exist in Cities?

section_content: When participants were asked what they would create, amplify, or destroy to facilitate a 'sharing city' in the future, a number of ideas emerged. Workshop participants stated that new social, business, and governance models to promote primarily non-economic, communal sharing should be created. In Lancaster, it was identified that values should be created through trust and transparency, particularly in models to govern the sharing city. Policies and practices should enable civic engagement and reward people for working with the community. Participants also discussed trust in relation to who would be the most 'trusted' host of a potential sharing network: for Lancaster-based participants, they wanted an apolitical person or group. In Birmingham, an exemplar model of sharing was identified in Birmingham City Council's Active Parks initiative, which provides a platform to allow communities to utilise parks and streets for their own events (see beactivebirmingham. co. uk/active-parks). 

Amplifying and improving existing initiatives and spaces for sharing, alongside greater civic participation and new social and business models, were identified in Lancaster and Birmingham. In both workshops, an appeal was made for both economic and non-economic and communal sharing to be made visible and tangible. In Lancaster, it was desired that existing activities and places of sharing should be recognised and valued, such as corner shops, markets, libraries, and food growing projects. In Birmingham, a desire existed to coordinate the activities that already take place in the community, and to foster a better network involving communities that are currently hard to reach. To do so, it was felt that informal sharing should be prioritised over formal models: a sharing city should be a platform that enables informal encounters in shared spaces. Unstructured ways of meeting and collaborating should be promoted in key places for sharing alongside spaces that are naturally conducive of sharing, including streets, green spaces and cafés. 

Furthermore, participants from the Lancaster workshop suggested that amplifying local, more non-economic and communal sharing initiatives was important and needed to be better connected to local economies, services, and projects, rather than relying on traditional models of consumption and big retailers. This, again, would require a fundamental shift in values as well as a reconceptualization of our narrow understanding of value as primarily economic [57]. As social connections are the foundations of the sharing city, communicating and sharing values become extremely important. 

Finally, participants talked about 'destroying time', as it was viewed by some as a key barrier to the uptake of sharing initiatives, both for users and for potential volunteers. Several participants expressed a desire in the future sharing city to value and prioritise the time spent contributing in the community over strict working hours. Once again, this alludes to a shift in values in contemporary society, and supports the perspective that changing consumer mindsets is one key to the success of sharing efforts [3]. 

There also was a discussion about removing (or destroying) cars from roads and creating alternative solutions. Participants in Lancaster desired better connections through safer bike access, walkable neighbourhoods, and affordable public transport. Together, these could bring the benefit of the sharing city to the whole area, particularly in more deprived areas within the neighbouring town of Morecambe. In Birmingham, participants wanted to discourage car ownership and transform today's busy roads into places where people could meet up. They also identified and promoted slow, more sustainable mobility solutions. In both cases, the management of transport by government was heavily critiqued, with current governance models perceived to be inadequate to meet the needs of the sharing city.
section_name: What Could Be Developed to Facilitate a Sharing City?

section_content: The Liveable Cities team synthesized the above findings from the workshops, developing the following proposition: to facilitate the 'sharing city' in which both non-economic and communal sharing and the sharing economy can sit alongside each other, three sets of things are needed: (1) physical and digital hubs; (2) physical and digital bridges; and (3) the wider promotion of sharing in cities. 

Regarding (1), hubs act as a centre for activity. Thus, having both a physical space and a digital network where sharing activities can be focused is important. Physical hubs are places, from very public (e. g., a library) to very private (e. g., living room in a house), where people can come together and share things. Digital hubs provide an online space that facilitates sharing that may be akin to Web 2. 0 sharing economy movements. 

Concerning (2), a bridge may be viewed as a structure that connects two separate parcels of land, as desired in the Lancaster workshop to reduce boundaries between physically isolated communities. It also could refer to bringing together two separate, yet potentially related, ideas or groups together. Here, the bridge could be physical, but it also could be digital by enabling the exchange of knowledge between sharing initiatives that may seem disparate. For both (1) and ( 2 ), the concepts of physical and digital hubs and bridges can be viewed as enablers, which assist sharing in proliferating in cities. 

Finally, with (3), the notion of sharing in cities needs to be promoted so that people will know it exists, they will know how to get involved, and they can begin to ask questions of government and other important stakeholders about how to ensure that sharing is an integral part of their cities. While many companies and organisations involved in the sharing economy will, no doubt, have marketing budgets to make potential and existing customers aware of their products and services, more local, non-economic, and communal sharing initiatives do not. The latter often are smaller, more traditional/institutional (e. g., sharing meals in religious spaces), more informal or hidden (e. g., sharing chickens) and more grassroots (e. g., Incredible Edible). One way to ensure visibility is to map both economic and non-economic and communal sharing schemes in cities. 

Systematically mapping the 'sharing assets' is as a key principle to governing the sharing city [58]. The mapping activity in Lancaster and Birmingham identified a very rich diversity of existing initiatives that are potential examples of sustainable practices for resource use, health, and wellbeing in cities. The initiatives identified also may be somewhat hidden and disconnected from the broader community. The authors of [53, 59] identify the importance of recognising social innovations, then potentially 'scaling out' or 'scaling up' networks to make them more sustainable. 'Scaling out' refers to growing small initiatives into large ones, preferably by multiplying the many small initiatives and projects so more people may participate, rather than making the initiative a large, homogenous organisation. Incredible Edible is an excellent example of 'scaling out' food growing initiatives, as it has been replicated from a few, to a network of many. 'Scaling up' refers to the challenge of making niche initiatives a central consideration in mainstream governance models.
section_name: Discussion

section_content: This paper started by looking at the concept of sharing in cities, noting that sharing does not necessarily need an economic imperative or a digital platform to be successful. From a practical perspective, we then investigated sharing on the ground in Lancaster and Birmingham, mapping sharing activities and understanding what needs to be created, amplified, and destroyed if sharing in cities is to be sustainable. Based on these perspectives, we reiterate that the sharing economy and non-economic and communal sharing in cities can co-exist; however, further research is needed to provide more nuance to the comprehensive and complex conceptual landscape of sharing. 

We also believe that for sharing to flourish in cities and to contribute to the economic, environmental, and social sustainability of these urban environments, mapping of sharing initiatives is an essential first step. This involves identifying what currently exists and promoting it, recognising who is involved, and what schemes might benefit from scaling up and out. We posit that creating physical and digital hubs and bridges could assist with the promotion of sharing schemes in cities and provides a voice to currently hidden sharing initiatives. Policy makers can help this process by developing policies and regulations that recognise and foster non-economic and communal forms of sharing that need not benefit from economic incentivisation. This also may involve changes in governance structures and models to prioritise sharing practices that bring communities together (e. g., providing small pots of funding to encourage, enable and maintain grassroots examples of sharing). Likewise, as many examples of sharing depend on physical space and assets, both urban planners and designers need to think more carefully about how to design new and existing developments and infrastructures-and the important spaces in between-to inspire sharing (e. g., designing innovative cohousing [60], institutional and vertical mixed-use buildings with shared kitchen spaces). By working in tandem with one another, both non-economic and communal sharing and the sharing economy offer significant potential to assist in the transition towards a more sustainable society within cities.
section_name: Conclusions

section_content: Acknowledgments: This work was supported by the Engineering and Physical Sciences Research Council [ EP/J017698/1 ].

section_name: Conflicts of Interest:

section_content: The authors declare no conflict of interest. The founding sponsors had no role in the design of the study; in the collection, analyses, or interpretation of data; in the writing of the manuscript, and in the decision to publish the results.
section_name: Conflicts of Interest: