How is ‘Sámi tourism’ represented in the English-language scholarly literature?

ABSTRACT

‘Sámi tourism’ seems to be increasing, both as a practice as well as a focus of research attention. The present study illustrates a review of English language literature concerning Sámi tourism and discusses the specific perspectives in this. The study uses a systematic literature review approach to grasp these perspectives and summarize the findings of pertinent English-language publications. In total 37 relevant publications were found that focus clearly on both ‘tourism’ and ‘Sámi’ (28 articles and 9 book chapters, all published between the years 1998–2017). Our analysis identifies three central themes in the literature so far: (1) the roles and limitations of Sámi tourism, (2) conflicts regarding tourism development, and (3) the representation of Sámi in relation to tourism. Finally, these findings are discussed in relation to broader literature including literature published in regional languages.

KEYWORDS:

• Sámi
• tourism
• representations
• indigenous
• systematic literature review

1. Introduction

Tourism is often seen as a field that by necessity deals with the ‘exotic’ or ‘different.’ This means that groups conceived of as less modern, or perhaps as more connected to nature, such as indigenous or other ‘original’ groups, tend to be given a large role in tourism and to be framed within authenticity discourses. This type of conception has largely been based on a simplified modernist view of both society at large and the groups conceived of in this way (eg Latour, 1993). Although this force has been recognized in tourism studies, it still remains a strong dynamic in tourism discourse and practice. Thus, tourism seems to rely on simplified imagery allowing tourists to easily recognize specific cultures, while at the same time these simplifications and commodifications represent an issue to be examined critically (Olsen, 2003, 2016). Regarding ‘northern’ or ‘Arctic’ tourism in northern Europe, the primary indigenous minority group are Sámi, originating from the northern parts of Norway, Sweden, Finland and the Kola Peninsula of Russia, with an estimated population around 75,000 people, the majority of whom today live in Norway, and originally composed of several groups of different Sámi peoples (Jaeger & Olsen, 2017; Niskala & Ridanpää, 2016). Occupations such as reindeer herding in particular, as well as hunting or fishing are often seen as traditional to Sámi. However, as traditional industries have declined due to changes in modern society, today also most of those self-describing as Sámi have similar lifestyles as and are included in the majority populations; furthermore, most Sámi have mixed backgrounds and may have multiple identities that either include Sámi signifiers or not (Leu & Müller, 2016; Niskala & Ridanpää, 2016). In particular to those active in traditional nature-related livelihoods and perhaps especially in reindeer husbandry, tourism has become a significant supplementary or sometimes main income because tourism can be combined with such livelihoods (Leu & Müller, 2016; Niskala & Ridanpää, 2016; Pettersson, 2001). The conception of the indigenous as ‘exotic’ or ‘different’ may also support tourism attraction to specific sites (such as for instance the Siida Sámi Museum in northern Finland), resulting in potentially both financial and cultural support but also risking tendencies to use and exploit cultural heritage (Pettersson, 2001; Tuulentie, 2006). In particular, tourism representations that tend to use specific descriptions that unify and traditionalize different Sámi groups may thereby obscure the complexity of identities and cultural variations in the areas. In addition, work on the risks of collating complex areas and cultures under an ‘Arctic’ label have also signaled the risk of in particular international literature to simplify such complexities (Keskitalo, 2004; Keskitalo, 2017).

In that vein, it is relevant to gain an understanding not only of Sámi tourism and its representations per se, but also of the ways in which ‘Sámi tourism’ has been present and represented in the international scholarly literature to date. Hence, the present study undertakes a systematic literature review of international, English-language, literature to gain an overview and understanding of the ways in which ‘Sámi tourism’ has been represented there. Accordingly, the paper addresses two questions: What literature on Sámi tourism can be found in the English-language academic literature? What representations of Sámi are found in this literature?

The paper proceeds from a methodology section, including the selection of relevant literature and its analysis. Findings are introduced in relation to three themes: (1) the roles and limitations of Sámi tourism, (2) conflicts regarding tourism development, and (3) representation of Sámi in relation to tourism. The paper concludes by contextualizing these findings in relation to broader research in relevant areas, also published in regional languages (which is thereby unavailable to English language audiences), and noting some suggestions for further research.

2. Methodology

A systematic literature review is a structured approach focused on gathering, assessing, and synthesizing literature related to specific research questions (Dawson, van der Meer, Skalicky, & Cowley, 2014). The systematicity of this methodology is advantageous because publications are chosen based on specific search terms and criteria, while in other methods subjective judgment might lead to different, less comprehensive results (Haddaway, Woodcock, Macura, & Colins, 2015).

For the present paper, a systematic literature review approach was applied to reviewing English-language publications on ‘Sámi tourism.’ As key search terms were defined the words ‘Sámi’ and ‘tourism.’ To ensure that all relevant publications were retrieved, a search string was applied using various possible spellings: Sámi OR Saami OR Sámi OR Sámi OR saami OR sámi; and tourism.

While it was originally considered to also include the search term ‘indigenous,’ it was found that the overall sample was too narrow to set any further limitations. Moreover, the term ‘indigenous’ might have resulted in retrieving publications not related to Sámi per se. Data collection covered the period from 1990 to the present and took place between February 17 and March 8, 2017; hence, publications before 1990 or after the search dates were not included. To limit the risk of relevant publications being missed (Haddaway et al., 2015), the study included primary databases assumed as covering the areas for tourism-relevant research: Web of Sciences, Scopus, Ebsco (including the following secondary databases: Academic Search Elite, AMED, Business Source Premier and GreenFile), and supplemented with the university library’s search tool covering a number of secondary databases (UB Umeå University, n.d.). However, it is still likely that relevant publications exist in databases that were not included in the review. It remains a limitation of the study that it may not have included all relevant literature, and it does not include for instance reports or other types of literature beyond English language articles and book chapters identifiable in the above databases.

The literature search of the selected databases provided a search result of 141 peer-reviewed articles (after removing duplicates) and 51 book chapters. Seeking to determine the relevance of these publications, all abstracts and at a later stage the full publications were read and assessed in relation to specific criteria (Klassen, Jadad, & Moher, 1998). To be included in the literature review, the article or book chapter needed to have a clear focus on both tourism and Sámi, in conjunction, and in order to capture a field of mainly tourism-related research that focuses on Sámi. Accordingly, all articles with no clear focus on ‘Sámi’ and ‘tourism’ in conjunction were excluded, such as articles mentioning these words as examples only, or articles or book chapters focusing for instance on Sámi reindeer herding and only mentioning tourism briefly (or even discussing reindeer herding as well as tourism, but as separate categories that thus do not cover Sámi/reindeer herding tourism). Three articles included in the sample also had to be excluded due to unavailability.

As a result of these criteria targeted at attempting to define tourism-related research on what is in this body of research conceived of as Sámi issues, a final set of 37 relevant publications (mainly published between 2012 and 2016) was included. Based on inductive grouping, the following themes were identified and constitute the basis for the description in the results: (1) the roles and limitations of Sámi tourism, (2) conflicts regarding tourism development, and (3) representation of Sámi in relation to tourism. More than twice as many publications were focused on representations of Sámi in relation to tourism than those grouped under the other two themes. Articles encompassed numerous different types of research approaches, from the 4H approach (conceiving of indigenous tourism products through habitat, handicrafts, heritage and history) to discourse analysis, field research and surveys.

3. Results

3.1. The roles and limitations of Sámi tourism

Much of the literature discusses the nature of Sámi tourism from a broadly tourism industry oriented perspective, for instance in relation to being a valuable economic resource but also risking commodification, as well as in relation to possibilities for tourism development.

A shared perspective in several articles is that tourism can represent a valuable economic resource for Sámi peoples (eg Leu & Müller, 2016; Müller & Pettersson, 2001; Palomino, 2012; Tuulentie, 2006). The decline of traditional industries such as reindeer herding is considered one main reason for Sámi involvement in tourism (Palomino, 2012). In this way, as Pettersson (2006) describes, tourism can also be seen as sustaining culture, because it offers job opportunities and potentially higher income to the groups involved. Additionally, tourism is often seen as an accessible source of income requiring little specialized skill (Leu & Müller, 2016) and it can be based on traditional activities, primarily related to reindeer herding, but also for instance hunting or other outdoor activities. In that vein, Palomino (2012) suggests that Sámi identity possesses a competitive edge, particularly in the area of ecotourism; a natural linkage between Sámi people and traditional livelihoods, natural environments and indigenous knowledge is thereby sometimes somewhat taken for granted. Likewise, Sámi tourism has been portrayed as a possible contributor to raising awareness about environmental and sustainability issues (Pettersson, 2006). There are also discussions about whether tourism should be an alternative to traditional industries at all. Palomino (2012), for instance, suggests that tourism should be a complementary activity rather than an alternative to traditional industries (Müller & Pettersson, 2006; Palomino, 2012).

The commodification of Sámi culture in relation to tourism is, however, a negative aspect discussed in several papers (Dlaske, 2014; Müller & Pettersson, 2006; Palomino, 2012; Pettersson, 2009). Yet these authors also describe the complexities of both the advantages and disadvantages of involvement with tourism. Tuulentie (2006), for example, maintains that the tourism industry can at least support awareness of Sámi culture and sometimes be seen as a way to keep Sámi culture alive. In that regard, she speaks of the ‘learning tourist’ as a positive dynamic in relation to Sámi tourism (Tuulentie, 2006).

Furthermore, the limitations of Sámi tourism are repeatedly discussed across the literature, which may also explain why some researchers prefer to discuss tourism as a complementary activity rather than an alternative one. Sámi tourism is said to face multiple limitations, one of them being a geographical one. Müller and Pettersson (2001) explain that a coordinated promotion of ‘Sámi destinations’ is limited by the geographical, operational isolation and dispersion, which often limits tourism venues to museums and handicrafts sales (Müller & Pettersson, 2001; Pettersson, 2003). Moreover, Sámi tourism involves high travel costs, covering large areas, different cultures and languages. It has been argued that most Sámi tourism has developed around existing service infrastructure, which allows tourists to reach many places considered relevant to Sámi tourism within a relatively short travel time from Scandinavian capitals (Pettersson & Viken, 2007). Yet, it has been suggested that may be precisely a perceived ‘remoteness' that is considered attractive from a tourist perspective (and as part of the ‘exotic’). Increasingly, snowmobiles or other means are used to bring tourists to more ‘remote' spots and limitations in relation to accessibility or seasonality are partly suspended (Müller & Pettersson, 2001).

Further limitations can arise from a reindeer herding perspective. Müller and Huuva (2009) discuss how some Sámi find it difficult to combine tourism with the requirements of actual reindeer herding practice, as the latter is highly dependent on current weather conditions as well as the natural cycles of the reindeer. Due to the migration cycles of the reindeer, tourism can only be developed for certain seasons, because the reindeer are not necessarily at the same locations as the tourists during certain times of the year (Müller & Huuva, 2009; Palomino, 2012). From this perspective, further development of tourism is sometimes thought to bring about negative outcomes; for instance, Pettersson argues that a small number of tourists might be appreciated and welcomed, as long as they do not interfere with other activities (Müller & Pettersson, 2006; Palomino, 2012; Pettersson, 2006).

3.2. Conflicts regarding tourism development

In relation to this type of broad tourism industry perspective often adopted in the literature, a recurring topic in the selected publications is the interaction between Sámi groups or representatives and tourists, as well as other stakeholders, in relation to tourism, which may include conflicts among Sámi and ‘non-Sámi’ stakeholders over multiple issues such as tourism development, land use, and power.

One main aspect noted in the literature is the different understandings of how Sámi tourism should be marketed, and what exactly should be promoted or developed (Kauppinen, 2014; Kelly-Holmes & Pietikäinen, 2014). Kauppinen (2014) argues that communities, such as in Inari in northern Finland, are debating how certain promoters view ‘Sáminess’ and reveals disagreement between Sámi and ‘non-Sámi' stakeholders’ perceptions of this identity. Kelly-Holmes and Pietikäinen (2014) identify tensions in the interaction between Sámi and tourists at a reindeer farm in Inari, Northern Finland. Concerning the ways in which Sámi culture is presented, their article suggests that Sámi operators in that case determine beforehand what they want to promote to tourists, with tensions in interactions arising when the content of the promoted product is challenged (Kelly-Holmes & Pietikäinen, 2014). (Further challenges regarding the representation and promotion of Sámi culture in relation to tourism are discussed in more detail in section 3.3.)

In relation to this, an area of conflict that is debated in the literature is that of land use in relation to tourism development, where groups such as Sámi people and other stakeholders are seen as having diverging interests. Several publications maintain that conflicts over land-use issues often arise and that attempts to manage these conflicts may for instance be made through agreements during the planning process. Ween and Riseth (2011) describe the dispute concerning increased opportunities through tourism development, on the one hand, and new pressures on reindeer herding areas, on the other. Likewise, Engström and Boluk (2012) discuss specific conflicts arising between stakeholders with reindeer husbandry interests and stakeholders seeking to improve the touristic attractiveness in the area surrounding Idre, Sweden. Jaeger and Olsen’s case studies (2017) in Jokkmokk, Sweden, and Kautokeino, Norway, have looked at attempts to address such conflicts through stakeholder collaboration.

With reference to Sámi as a minority group, several publications address the apparent lack of authority and power in decision-making (Engström & Boluk, 2012; Kauppinen, 2014). Although several articles suggest that tourism may be beneficial for Sámi, articles also suggest that outside agencies and other non-Sámi entrepreneurs are often in control, for instance over what is being marketed (Engström & Boluk, 2012; Pettersson, 2009; Ween & Riseth, 2011). Olsen (2010) suggests that a relationship between Sámi and the territory is difficult to inscribe, as few Sámi conform to the image of the ‘emblematic Sámi,’ rather they are categorized into the general nationalities (Swedish, Norwegian, etc.). A related issue discussed in some publications is the different legislative rights applied in the different countries; moreover, there are also diverse regional differences regarding Sámi culture, such as language or other practices, which affect the local prerequisites for tourism development (Kelly-Holmes, Inen, & Moriarty, 2011; Müller & Viken, 2017). Reindeer herding, for instance, is a right of the entire population in Finland, but exclusive to Sámi in Norway and Sweden (in Sweden with some few exceptions; Ween & Riseth, 2011). Tuulentie (2006) maintains that, in the case of Sámi tourism in northern Finland, power is mostly thought to lie in the hands of the non-Sámi, as ethnically Finnish people are in the majority in the area. In cases described by Pettersson and Viken (2007) in northern Norway, there are examples where local Sámi seem to be more empowered and more involved in tourism production. They also discuss national differences in the ways Sámi culture is being promoted and controversial tourism ventures in Finland that have been criticized for exploiting Sámi culture (Pettersson & Viken, 2007). Similarly, Müller and Viken (2017) also discuss national differences, for instance a more neo-liberal or directly market-oriented as opposed to a local development targeted approach to Sámi tourism development.

3.3. Representations of Sámi in relation to tourism

As could be assumed amongst other as a result of the type of conflicts discussed above, the major portion of publications on Sámi tourism related to the representation and promotion of Sámi culture with respect to tourism. The literature maintains that tourists may have a set of pre-defined images and expectations they bring to the destination, where often rather stereotypical views – possibly created through (social) media – persist (Olsen, 2006; Pietikäinen & Kelly-Holmes, 2011; Viken, 2006). Hence, what the tourists expect and want to experience is in part already established, and regional groups will thus need to confront external assumptions in attempting to define themselves, land use and representation in relation to tourism. The images tourists may be confronted with are often of traditional (sometimes past) Sámi livelihoods. Accordingly, as Müller and Viken (2017) suggest, tourists may search for well-known symbols of a model culture composed of people living in tents, herding reindeer and wearing traditional clothes in order to identify people as Sámi. Where these traditional symbols are not found or identified, tourists may not recognize people or places as indigenous ‘Sámi’ (Viken & Müller, 2006). Locally, such representations are often considered to represent historical Sámi culture, which is sometimes not representative of livelihoods today, rather than modern Sámi lifestyles (Müller & Viken, 2017). In an example given by Viken (2006), informants explain that tourists sometimes doubt they are Sámi because they are wearing modern clothes. This clash between tourist expectations and modern realities can sometimes lead to staged representations, where people for instance dress traditionally to represent the traditional/emblematic Sámi (Müller & Pettersson, 2006; Viken, 2006). Thus, in the context of indigenous cultural tourism, there is often pressure to conform to tourists’ ethno-spatial imagery of ‘otherness’ or ‘exoticism’ in order to be competitive (Maraud & Guyot, 2016; Müller & Viken, 2017).

In this connection, several publications maintain that the branding used for Sámi attractions and Sámi destinations is often framed as ‘exotic.’ Accordingly, Sami culture is represented through exoticism, creating a distinction between the ‘strange’ and the ‘familiar’ (Niskala & Ridanpää, 2016). Tourist imagery needs to stand out as something unique, creating a sense of otherness (Müller & Viken, 2017). Olsen (2006) analyzes several tourist brochures and finds that images of Sámi are rather traditional rather than modern; in this way, Sámi are framed as ‘the last nomads of Europe’ and stereotypical images prevail throughout the documents (Olsen, 2006). Hence, branding through stereotypical images is a rather common strategy in Sámi tourism marketing (Müller & Pettersson, 2006; Olsen, 2006; Viken, 2006; Viken & Müller, 2006). The research contextualizes the situation, showing that such a stereotyping approach cannot simply be regarded as negative, but rather as the downside of the same (competitive tourism marketing) coin. As Müller and Pettersson (2006) argue, a certain amount of staged culture may be necessary in order to attract tourists.

Likewise, other authors suggest that tourism and indigenous culture lie at a fragile balancing point between ‘authenticity’ and stereotyping (Johansen & Mehmetoglu, 2011; Vladimirova, 2011). However, what is authentic is contested, as Viken (2006) pointedly remarks: in some sense, an authentic experience is what the tourist perceives as authentic. For example, Äikäs and Spangen (2016) describe the creation of Sámi sites for tourists. These have received criticism for their lack of authenticity, for being mainly sites for amusement and commercialism, but they have not necessarily been viewed negatively by tourists (Äikäs & Spangen, 2016). In contrast, there is an argument that the unique (and sometimes staged) imagery of Sámi culture attracts interested outsiders and thereby benefits Sámi indirectly as a platform for cultural expression as well as providing financial benefits, which is elaborated by Abram (2016) for the case of the Jokkmokk Winter Festival. Somewhat similarly, Pietikäinen and Kelly-Holmes (2011) suggest that if a product is not differentiated enough, it is not worth buying from a touristic standpoint. Their article illustrates how Sámi languages and well-known Sámi brands, such as the Duodji handicraft label, are used to authenticate something as Sámi (Pietikäinen & Kelly-Holmes, 2011). According to Olsen (2006), Sámi exotification also relies on spatial othering, through which the northern environment is framed as ‘wilderness’ and the existence of a cultural landscape is almost being erased (Olsen, 2006; Wall-Reinius, 2012). Wall-Reinius (2012) provides a controversial example: Even though reindeer are domesticated, from a tourism perspective they continue to be viewed within a wilderness imagery.

A few publications also question whether the stereotyping tendencies might be changing. One possible reason for this change is related to global mobilities and economic restructuring (Kauppinen, 2014). Based on interview material, Tuulentie (2006) suggests that tourists and Sámi, the global and the local, are no longer opposites, but rather fluid. This brings stereotyping to another level, where we are all stereotyping as well as being stereotyped – a level that could result in new viewpoints and understandings (Kauppinen, 2014; Tuulentie, 2006).

4. Discussion

A central discussion documented in the literature thus revolves around representations of Sámi that are used in relation to tourism. The contested question is basically: What should be represented and who has the right to represent it? A well-documented tendency is that Sámi are being represented in traditionalizing, stereotyping ways and as one unitary group, thus omitting cultural differences among Sámi as well as variation and relation to other groups. For instance, in a tourism context, in particular nature as well as some symbols used in relation to tourism can be considered more of a given with regard to past Sámi livelihoods than with regard to varied experiences at present. For tourists only visiting a short time – and visiting for instance Sámi museums with a focus on historical lifestyles, or drawing on images in marketing – this difference may not always be apparent and may result in conflict, or at least confusion over what ‘authentic’ Sámi culture(s) is/are. Accordingly, current tourism representations largely ignore modern Sámi lifestyles, modern occupations, their diversity and even the fact that many even self-acknowledged Sámi actually reside outside historical Sámi areas. Also, the common assumption that ‘Sámi experiences’ must happen within specific areas point to a traditionalizing, stereotyping character of Sámi tourism.

While some publications in this review elaborate critically on the seemingly ‘natural’ linkage made between Sámi identities and nature-related activities, in particular reindeer herding, other publications do not problematize these dynamics. A difference can here be seen in particular in relation to some literature in regional languages, where a larger variation from modern to traditional and also a larger internal variation in groups, including conflicts within what have often in the above been described as more unitary groups, are acknowledged. Some of that literature also discusses stereotyping also in relation to other regional categories. Examples here include Kramvig (1999), Drivenes (1985) (see also Olofsson, 1995) that take broader regional, historical, ethnic or legal perspectives, and even literature on the Nordic context that explain the historical development and construction of identities (eg Salvesen, 1995).

Thus, one important context that is less discussed in the material may pertain to an understanding of the variations in this area that result from long historical interactions between groups, and that mean that many groups – not only Sámi – may have a relation to the environment, as well as that identities may be fluid and mixed, and can also be modern rather than traditional. Literature outside the field highlighted in this review thus discuss a traditional linkage to nature amongst population in much of the areas, and not only regionally but in the nations at large (eg Vepsäläinen & Pitkänen, 2010 on Finland; Cruickshank, 2009 and Hidle, Cruickshank, & Mari Nesje, 2006 on Norway; cf. Keskitalo, in prep.).

While a more strictly Sámi tourism-focused literature could not necessarily be assumed to relate to such a much broader context, thus, framings and concerns voiced in such literature could serve to problematize and place into context issues of representation and power.

In addition, another issue that is not discussed in detail in the context of Sámi tourism described here, is that what researchers place under the umbrella ‘Sámi tourism’ may in reality be ‘Arctic’, ‘Lapland’ or ‘North Cape’ tourism in the mind of the tourist (that is, tourism related to alternative larger, more abstract, regional or specific conceptions, see also Müller & Viken, 2017). The ‘Sámi experience’ may, hence, only be part of the larger product. Consequently, it is important to question whether the role and development perspectives of Sámi tourism would not benefit from being equally contextualized in such a way. This may also be valid when it comes to the managerial challenges tied to the geographical and operational limitations of Sámi tourism.

5. Conclusion

The present study has reviewed existing literature on ‘Sámi tourism’ and presented several recurring themes found throughout the selected, English-language publications. While the study is limited in what data bases, types of literature and time period it relies on, as well as in categorizing literature into three themes that highlight commonalities in the literature rather than potential variation at more specific article level, the study constitutes a (first?) attempt at reviewing perspectives on Sámi tourism expressed in international literature.

The study illustrates that Sámi tourism as a field, often supplementary or in other ways related to traditional resource industry, was indeed conceived of in a selection of English language literature. The role of Sámi tourism seems widely described as an economic opportunity in the context of the decline of traditional industries and in particular reindeer herding in northern Europe. It is contested whether this engagement with tourism should represent an alternative or complementary occupation and income, which may have both ideological and practical causes. The further development of Sámi tourism is said to be partly constrained by the relative remoteness of areas considered ‘Sámi’ as well as the dispersed nature of Sámi tourism opportunities. Furthermore, some publications document local resistance to tourism development and disagreement among different stakeholders as well as industries. In this context, there are, for instance, conflicts regarding land use rights or tourism in relation to the interests of primary industries. In relation to such conflicts, the study has also shown upon representations of Sámi tourism as a major field of discussion and contestation, crucially related both to the problems of defining and stereotyping a particular group in relation to historically formed understandings, and to the way that competitive tourism marketing may support or even create or enforce such representations and may in that highlight power discrepancies. Potential benefits of tourism are thus seen as needing to be balanced against a potential cost of commodification, with attention to winners and losers in such a tradeoff, and the potential risks of simplifying what are in reality very diverse situations.

Generally, the publications show that, across the different countries, areas, groups and individuals, there are greatly differing opinions and strategies regarding Sámi tourism. This would seem to suggest a direction for further research, to continue to address the differing, complex and individual opinions as well as situations regarding tourism in relation to various groupings, identities and areas. In this connection, while tourism might essentialize ‘Sámi'/‘non-Sámi' as given, unitary groups, it is crucial that researchers not simply reproduce these categories (as a sort of ‘methodological nationalism’, cf. Brubaker, 2014). Rather, research would need to approach tourism studies by taking into account individuals’ varying identities and self-ascribed ethnicities, the potential variations in types and labels applied to tourism experience, as well as the localization and enablement of varying groups and sub-divisions of these in relation to power over development.

Acknowledgements

We gratefully acknowledge funding from the FORMAS SÁMI call.

Disclosure statement

No potential conflict of interest was reported by the authors.

Additional information

Funding

This work was supported by the Swedish Research Council FORMAS.