**1. Introduction**

The so-called sharing economy (SE) and overtourism are both coincidental and complementary phenomena. Since they have been simultaneously experienced by communities in the growing number of, mainly urban, destinations, academic studies as well as industry-related and governmental insights associate or join them together as disruptive, unsustainable forces undermining long-term tourism development and community well-being [1–10]. This recent wave of research has complemented the existing discussion on the sustainability of SE [11–15].

Nevertheless, although complementary, both phenomena are of a different nature and scope. SE refers strictly to social relations which are embedded in and also fuel and transmit social capital [16–18]. Accelerated by technological development, it develops globally and transforms even more spheres of human and economic activity, strongly emphasizing its presence in the tourism industry, especially

in accommodation, transport, catering and tourism experiences [19,20]. As the SE's impact is widely discussed through the prism of accommodation platforms [20–23] we mostly consider this sector of the tourism industry. Overtourism, in turn, is a place-specific and industry-related mechanism. As a temporary and 'explosive' phenomenon, it condenses all the aspects of visitors' activity and the tourism industry in affected destinations, including the experiences or services distributed or accessed by sharing. Thus, when these two phenomena are studied together, we can discuss tourism as a domain of the SE, and the 'sharing' aspects of overtourism.

Yet, due to an early phase of their evolution and the eruptive nature of their expansion, mutual relationships of both phenomena have not been fully recognized, leaving a gap for further research. Even so, many researchers claim that the SE contributes to overtourism by jointly pushing urban gentrification processes, depopulation of city centers and other processes of social exclusion [3,24–28]. In light of this, in this article we consider overtourism in the context of studying the impact of the SE expansion on local communities. The emerging overtourism syndrome may be one of first striking examples of the problems in which the SE is directly involved. Thus, the externalities resulting from the SE in (over)tourism context on the community level could be a laboratory for SE's influence in general.

Although sustainability issues involving the SE have been discussed quite often in the tourism development context [1,24,26,29], these studies were contextual, based on the case studies, and also related to various conceptual frameworks(or none, if not indicated by the authors). The majority of them identify and characterize the positive/negative impact of the SE on local communities by referring to respondents' opinions or figures indicating a certain stage or level of the phenomenon [3,4,30,31]. Theoretical studies investigating the process of the SE impact itself through the prism of concrete theoretical frameworks can hardly be found. Apart from the Social Exchange Theory (SET) [28], which is frequently utilized as a field research framework, the presence of other theories is very limited [32,33]. Thus, there is a need for conceptual studies which could explain the links between sustainability and the SE impact on the local communities in the tourism context in a complex way, framed by a clearly-defined theory which goes beyond tourism-specific concepts.

This viewpoint article addresses the gap in the theoretical discussion on the expansion of the SE in the urban communities affected by overtourism. As the SE refers to social relations, and well-being and quality of life are recognized as crucial indicators of the social dimension of sustainable development [34,35], the article aims to conceptualize the impact of the SE on urban destinations through the lens of Putnam's [18,36] approach to Social Capital Theory (SCT). However, both the SE and overtourism affect the density of social capital, thereby triggering calls for sustainable solutions. Discussing the impact of the SE on local communities in the tourism context would allow us to compare the prevailing discussion on the sustainability of the SE and propose a new perspective for interpretation and research on the subject. Thus, we argue that the SCT contributes to gaining a more complete picture of the conjunction of the SE, overtourism and a local community's (un)sustainable development.

The article contributes to the discussion on sustainability of the SE by adopting the SCT framework to expand explanations on in its role and scope of impact on local communities in relation to the overtourism syndrome. As the tourism industry is one of the spheres where the SE is diffusing, and it is estimated to expand into other market and social activities [7,13,20,37], one can argue that the overtourism context should be considered as a laboratory for studying the sustainability of its impacts in general. The article also contributes to the discussion on overtourism by focusing on the impact of the SE on local communities, instead of only identifying the effects of these changes.

The latter parts of the article are organized as follows. First, we explain the method applied. Then, the SE is briefly introduced in the sustainability and the tourism contexts. After that, we focus on the relations between overtourism and the SE. Next, the review of the sustainability of the SE in the tourism context is presented. The following part discusses the principles and the evolution of the SCT. In the results section, we juxtapose the literature review results concerning the sustainability of the SE with the SCT perspective. We conclude by implementing a new configuration of social capital and its consequences for local communities in the context of overtourism.

#### **2. Materials and Methods**

Our considerations are based on a review of the existing literature on the subject. We adopted a two-step selective systematic review of the papers indexed in Web of Science and Scopus databases. It the first step, we conducted two separate procedures focusing on search terms 'overtourism'; and 'sharing economy' or 'collaborative consumption' indicated in the article titles, abstracts or keywords. The aim of the analysis was to recognize their definition range and the main research threads referring to both phenomena. No year limit was used. Because of the research aim and the large number of document results (98 records referring to overtourism and 2135 records referring to the sharing economy), we limited the review to the most frequently cited documents.

In the second step, we focused on the articles referring to overtourism/tourism development and the SE, both referring to sustainability. Thus, the following search terms were selected: 'overtourism' or 'tourism'; 'sharing economy' or 'collaborative consumption'; and 'sustainability' or 'sustainable development'. The search resulted in 25 documents. The selection procedure consisted of initial scanning in line with the criteria used in the second step. Moreover, the specification of the theoretical/conceptual framework of the study was an additional criterium. In effect, nine papers were omitted. The organized final list of selected 16 papers is specified in Appendix A. The review focused on an analysis of the content of each paper in order to synthesize different perspectives and identify the scope of the SE impact on the sustainability of local communities.

The selected papers were published in the years 2016-2019. They refer to various theoretical frameworks and concepts. Indeed, the Social Exchange Theory proved to be the most popular concept [3,28,38,39], in combination with neoclassical economics [32]. However, besides a single paper designed as a theoretical dispute on the regulation of the SE, they all use the theory for empirical reasons such as to measure residents' perceptions, and not to recognize the links between the SE and communities. According to SET, the attitude of the residents relies on the assessment "of the expected benefits or costs obtained in return for the services they supply". In general, the residents will support the development of a phenomenon or activity, if they perceive more positive impacts (benefits) than negative impacts (cost) from it [40]. The Social Representation Theory is an alternative concept, applied by von der Heidt et al. [31]. It refers to a system of symbolic representations—which could be conceptualised as "a history of mentalities" instead of objective reality—shared both by individuals and society. This system is the foundation of the individuals' building their perception of one's self as a part of a group [41]. The other works are based on tourism-specific concepts: tourism degrowth theories [42], the social carrying capacity concept [4], Doxey's [43] Irridex model and Butler's [44] Tourism Areal Life Cycle Model. Alternatively, they design their own research frameworks [25,30,45]. Two literature reviews conclude the set of literature.

Moreover, in the conclusion part, we used more general literature referring to both tourism development and social capital. A literature review on overtourism and the SE points to some attempts to recognize the relations between the SE and on local communities; however, it is performed without any reference to social capital. As social capital is the key adhesive of communities, we argue that it should be included in this discussion to gain a more complete picture of the conjunction of the SE, overtourism and local community (un)sustainable development.

#### **3. The Sharing Economy Interplay with Sustainability**

There is no agreement among scholars about what the SE is and how it refers to other types of modern forms of economic models [19,46,47]. In its narrow and primary meaning, the SE refers to the short-term use of less-frequently used assets by various actors within a network economy, enabled by the development of the Information and Communication Technologies (ICT). Nowadays, the SE has encompassed a variety of different products and services, which are distributed or accessed to by sharing or through collaborative practices [48].

Having in mind terminological controversies, the variety of the SE concepts and related terms [19,20,49], we follow Acquier et al. [50] and Netter at al. [48] to adopt a broad understanding of the SE term. We consider the SE as an umbrella construct that encompasses business-to-business, business-to-consumer and peer-to-peer initiatives—driven both for-profit and non-profit motivations—which are based on and combine at least three following foundation cores [50]: (1) the platform economy, in terms of intermediating decentralised exchanges among peers through digital platforms; (2) the access economy, in terms of sharing under-utilized assets to optimize their use, offering services instead of products; (3) the community-based economy, in terms of coordinating initiatives through non-contractual, non-hierarchical or non-monetized forms of interaction. We elaborate on each of these cores below.

The SE networks are strictly associated with digital technologies, which are both a driver towards and the essence of the SE [51–54]. The ICT has made sharing convenient and transparent as well as open to many individuals and businesses, regardless of their size and location. The term "platform" refers to an intermediary acting to create access or to manage exchanges, payments and evaluations among peers or companies [13]. The platforms are the structures which enable transactions by connecting two contracting parties for the purchase of commodities or the provision of services [55].

The SE is rooted in social relations, as the access economy and the community-based economy are among the foundation cores of the SE. Thus, the issue of its sustainability in general (not only in the tourism context) has been raised as a characteristic of the SE phenomenon. Originally, the SE has been popularized as a more sustainable form of consumption [56–58]. However, with the development and proliferation of the SE models and platforms, the debate around their impacts on sustainability has been growing and critical voices have become more sound [13,47,50,59,60]. Moreover, because of the newness of the SE concept, descriptive and explanatory studies dominated literature and report reviews [1,12,37,61–63] or the internet and social media monitoring [13], supplemented by research projects based on the primary sources analysis and case studies of selected industries or platforms [33,56,64,65]. On the basis of the transition theory, Martin [15] claims that the SE can have positive impacts on sustainability because it creates economic opportunities, but it can also increase unsustainability by reinforcing the forms of neoliberal capitalism. Similarly, Geissinger et al. [13] stress that sustainability impact of the SE is hard to operationalize and measure objectively because of the ambiguous and diverse nature of the SE. This fact allows some marketers of the SE platforms to conduct 'share-washing' of their activities on official and social media [13,61].

Because of its specific characteristics and systemic problems—in particular, its functioning in the global-local nexus [66–68]—tourism is an industry that is particularly exposed to sharing practices [19,20,47,69]. Dredge and Gyimóthy [19] identify the existing collaborative opportunities in the food, travel services, health and wellness, currency exchange, travel companions and support, accommodation and work space, transport and education industries. Based on the object of exchange, Gössling and Hall [20] grouped the sharing market in tourism into three building blocks: asset, services and opinion. They refer to accommodation, transport, food, information, advice and evaluation, travel visualization, virtual travel and advocacy. Their common characteristic is the exchange process being facilitated by an app or website intermediary. Palgan et. al. [70] classify the sharing platforms operating in accommodation industry according to a type of exchange. They distinguish between a commercial exchange (business-to-customer exchanges), rental (peer-to-peer flats rented directly from owners or managed as timeshares), reciprocal exchanges (home swaps) and free accommodation (guests are accommodated without commercial interest). However, Airbnb is the most eminent and discussed example of the sharing economy business model in tourism, which has changed the global value chain's logic and has become a symbol of the disruptive power of the global economy and local communities living in popular tourism destinations [21,69,71–73]. As the impact of the SE on the accommodation sector has opened the widest and the most lively discussion among scholars [20–23], our considerations refer mostly to this area of the tourism industry.

### **4. Overtourism as a Context of the SE's Impact**

Overtourism is a recent syndrome experienced in a growing number of destinations, prominently affecting towns and city centers with well-known cultural assets and popular amenities [26,29,74,75]. Milano et al. [76] define it as the excessive growth of visitors leading to overcrowding in areas where residents suffer the consequences of temporary and seasonal tourism peaks, which have enforced permanent changes to their lifestyles, access to amenities and general well-being. In a narrow context, overtourism refers to the physical characteristics of cities and is just about managing tourist flows to stop them from increasing above the maximum carrying capacity thresholds in time and space, in central or in historic quarters. However, its complex and disruptive nature has led researchers and governance practitioners to perceive overtourism in a wider context and through a more sophisticated lens. Goodwin [77] notes that the destinations experience overtourism not only when "hosts or guests, locals or visitors, feel that there are too many visitors", but also when they feel "that the quality of life in the area or the quality of the experience has deteriorated unacceptably". Koens et al. [26] coined a much more comprehensive definition, specifying that overtourism is "an accumulation of different impacts and perceptions that relate both to tourist behavior as well as actions by, and encounters with stakeholders as well as changes to the social, economic and physical environment" (p.5). In this wider meaning, overtourism refers not only to the tourist number, but to the wide range of over-developed tourism impacts, including supply side and boosterism policies based on tourism functions. Thus, it is the quality of the residents' life which is at stake in the overtourism struggle, discussed in the literature in the wider context of sustainability [45,77,78].

Resultantly, calls for mitigating the negative consequences, conflict management, more sustainable tourism development strategies or even degrowth proposals have been raised in tourism academic discourse [79–81]. Nevertheless, researchers stress that overtourism as a destination-specific phenomenon is resistant to "one-size-fits-all" solutions [26,77].

In general, the changes which effect overtourism and the sharing economy are generated by various megatrends [82]. It is the cities where the strongest intensity and impact of the megatrends on tourism can be observed. In particular, it refers to the factors evoked by both the technological (eg. digital transformation) and economic megatrends (eg. globalisation) [83,84]. Despite complex, multifaceted and dynamic nature of both phenomena that makes them slip out of clear definitions and objective measurement, we can state that overtourism and the SE are complementary phenomena (Appendix A). As tourism is a spatially-concentrated phenomenon—as evidenced sharply in the destinations affected by overtourism—the impacts of the SE, also an uneven dispersal activity at the community level areas are one of the most frequently discussed topics in relation to the development of tourism. Researchers mostly agree that the relationship between overtourism and the SE is not only spatial; this relationship is also causal. However, the academic papers can be divided into three perspectives of that causality (see Table 1). The first one consists of works which consider the SE as an enabler or component of overtourism, i.e., as a factor contributing to overtourism. In this context, the SE is perceived in an oversimplified way, contributing to selected dimensions of overtourism defined in a wider meaning or accelerating them, like the spatial saturation of overtourism, the shortage of available living space and the increase in rents. The soundest thread of the studies in this perspective deals with the measuring of residents' perceived impacts of overtourism and/or the proliferation of the SE and their attitudes towards tourism and the tourists associated with these impacts. The second perspective presents a two-way nature of relationships, indicating that both phenomena are not only coincidental but also fueled by a feedback loop mechanism, leading to a more comprehensive phenomenon, i.e., gentrification. The third perspective, which deals with the SE as an effect of overtourism, is not strongly represented in the literature. The studies link overtourism to a growing number of tourists or international party-goers, fueling the expansion of non-institutionalized forms of tourist accommodation. Nevertheless, there are also studies which do not fit in only one category as they take a multi-view approach. Additionally, there are papers which present literature overviews of the existing approaches and concepts on the subject.


**Table 1.** Perspectives of the sharing economy (SE)—overtourism relationship.

Due to the multidimensional nature of both phenomena, and their early level of evolution, it is hard to verify the validity of classifications presented in Table 1. Consequently, it is necessary to adopt one of these three perspectives to carry on with considerations by allowing for a more in-depth study of the phenomenon. Therefore, taking the above into account, this article adopts the second perspective, although it is not the most frequently used one. First, this approach partially overlaps with the first one, implying a much broader range of consequences. We perceive the SE as being rooted in the social relations among individuals and within neighborhoods and, thus, as being endowed with the ability to leave a deeper and longer lasting mark on communities which could not be easily—if there is any easy issue at all in the overtourism syndrome—mitigated or inverted. Second, the SE is a trend that is not only spreading in tourism, as this industry could just be a transfer platform to other sharable and collaborative activities. In this context, we situate our article in a sociologic study, adopting the city as a spatial scope of research, and tourism as a research context within the dynamic framework of overtourism in which social relations occur and social capital is changing.
