From social media diet to public riot? Engagement with “ greenfluencers ” and young social media users ’ environmental activism

Many adolescents and young adults spend countless hours a day on social media, where they can engage with social media influencers and may establish parasocial relationships (PSRs) with them. Recently, “ green ” influ-encers ( “ greenfluencers ” ), who post content on the topic of sustainability, have emerged. Yet, it is unclear whether adolescents ’ and young adults ’ engagement with greenfluencers on social media may inspire them to low-and high-effort environmental activism. Besides direct associations, PSRs with greenfluencers may mediate the effect of engagement on both forms of activism. We address these questions in a quota-based cross-sectional survey of 16-to 25-year-olds in Germany ( N = 865), taking the moderating role of environmental knowledge into account. Results show that engagement with greenfluencers relates to low-and high-effort activism directly and as mediated via PSR. A young person ’ s environmental knowledge has no moderating effect on low-effort activism. However, having environmental knowledge amplifies the positive association between engagement and high-effort activism and decreases the positive association between PSR and high-effort activism. As such, the results indicate that engaging with greenfluencers may indeed inspire environmental activism. Limitations and implications are discussed.


Introduction
Total social media use has increased consistently over the last couple of years.The number of social network users worldwide is expected to rise from 2.86 billion in 2017 to 4.41 billion in 2025 (Statista, 2021).In Germany, young adults between 18 and 19 report spending an average of 306 min per day on online activities (JIM-Studie, 2020).Among the favorite online activities of 12-to 19-year-olds is spending time on the social platforms YouTube, Instagram, and WhatsApp (JIM-Studie, 2020).On these social networking sites (SNSs), young individuals are exposed to and potentially engage with social media influencers (SMIs), for instance by commenting on their posts or writing them private messages.Apart from their reach, SMIs can be characterized by the potential impact they have on their audience (Hudders et al., 2021).As such, SMIs are highly relevant for advertising, and scholars discuss them primarily in terms of their advertising value.But not all SMIs are alike.After all, Instagram content posted by Greta Thunberg differs drastically from Kylie Jenner's content.Given the advent of the climate crisis and increasing calls for sustainable politics and practices, promoting sustainability and a "green" lifestyle has become an important selling point for brands and businesses (Segev et al., 2016).At the same time, Fridays for Future and its popular spokespersons have shown huge mobilization potential among adolescents and young adults.Green influencers ("greenfluencers"), a subgroup of influencers who specifically post content related to sustainability, have occupied this green domain-be it advertising for sustainable brands, raising concerns about the climate crisis, or promoting environmental activism.
Scholars have already addressed the question of whether social media use can have an empowering effect and spark political interest and political participation in users (e.g., Jung et al., 2011;Park, 2013;Vitak et al., 2011).Taking a motivational approach, the social media political participation model (SMPPM; Knoll et al., 2020) describes the conditions and processes under which social media use may predict lowand high-effort political participation.We build on this distinction to shed more light on the associations of engagement with greenfluencers with low-and high-effort environmental activism.In the past, SMIs have been investigated in terms of their advertising value (Hudders et al., 2021) and, to a lesser extent, their political mobilization potential (see, for instance, Naderer, 2022).Yet it remains unclear to what degree engagement with greenfluencers on social media might relate to low-and high-effort environmental activism in adolescents and young adults and whether this relationship depends on the adolescents' and young adults' environmental knowledge.Differences in environmental knowledge among young individuals might affect their information-processing mode and thus moderate these effects.But there is more to the story.To SNS users, SMIs can be much more than entertaining strangers.The appeal of SMIs lies, among other factors, in the intimacy they convey (Hudders et al., 2021).Research indicates that social media users might establish complex parasocial relationships (PSRs) with SMIs (e.g., Breves et al., 2021;Su et al., 2021).While this affective component has been emphasized as an important factor for influencer marketing and advertising (e.g., Breves et al., 2021;Hwang & Zhang, 2018), it has yet to be determined how a PSR with greenfluencers may relate to low-and high-effort environmental activism and whether these associations are moderated by users' environmental knowledge.
We address these questions in a cross-sectional survey of adolescents and young adults in Germany aged 16 to 25.The contributions of this approach lie in 1) the focus on young people as the future generation of voters, consumers, and policymakers, 2) expanding research on SMIs beyond their advertising value, and 3) investigating the SMI-related drivers of environmental activism as active involvement in democratic processes and a possible means for combating the climate crisis.In the face of growing concern about sustainability in general and the climate crisis in particular, understanding the potential impact of greenfluencers on adolescents' and young adults' participatory efforts is crucial.

The emergence of greenfluencers in the advent of the climate crisis
SNSs have established themselves as a cornerstone of the daily lives of adolescents and young adults.Apart from simple peer-to-peer communication, SNSs also made way for so-called SMIs.While definitions of SMIs are heterogenous, Hudders et al. (2021) emphasize reach and impact, which the authors further subdivide into expertise, authenticity, and intimacy as key components of most influencer conceptualizations.In short, SMIs have larger numbers of followers than ordinary SNS users and are thought to influence their audience in a particular way.Present research on SMIs mainly focuses on advertising and influencer marketing (Hudders et al., 2021;Naderer, 2022).But SMIs cannot be comprehensibly understood by merely reducing them to their value for advertisers.
Considering the dramatic scenarios that scientists are drafting around the impacts of the climate crisis (IPCC, 2021), it is not surprising that adolescents and young adults, in particular, see the need for drastic societal change.Nonetheless, it is important to keep in mind that the call for sustainability was not invented in the 2000s or 2010s.Large-scale environmental movements had already gained prominence in the late 1970s (see Rootes, 2004, for an overview).Yet the scope and the urgency of the debate have intensified.Scientists view a global warming of 1.5 • C, compared to pre-industrial temperatures, as a climate tipping point (Steffen et al., 2018).To prevent further global warming and avert dramatic ecological shifts, the member states of the United Nations signed the Paris Agreement in 2015, signaling a commitment to limit the extent of global warming to below 2 • C and preferably below 1.5 • C. While achieving this goal would save trillions of dollars (UN Environment, 2019) and is at the heart of successful maneuvering through the climate crisis, it is nearly unachievable now.Keeping in mind that it is not today's politicians who have to endure an unraveled climate crisis, it is understandable that younger generations raise their voices and demand change.The sustainability issue has also imposed itself on advertisers, who recognize it as an important marketing strategy.Segev et al. (2016) find a stark increase in green advertisements over the years.Analog to the rising salience of the climate crisis as an existential threat as well as trends toward a sustainable lifestyle and green advertising, specific kinds of SMIs have emerged.
Fridays for Future, for instance, is an environmental movement that orchestrates school strikes (i.e., physical protests) on social media.The young and mostly female faces of Fridays for Future have large numbers of followers on social media and can be considered SMIs. 1 But the general notion of greenfluencers is broader.Pittman and Abell describe greenfluencers as a "subset of specialized influencers […] who promote a sustainable lifestyle and eco-consciousness" (2021, p. 1).The concrete greenfluencer content may be diverse and span from promoting sustainable fashion or slow traveling to giving advice about waste reduction, promoting a vegan lifestyle, or initiating environmental activism-the overarching thematic frame is sustainability.Preliminary findings emphasize the role of (female) greenfluencers in the transformation toward more sustainable consumption patterns (Yıldırım, 2021).However, SMIs can also be (political) opinion leaders, and greenfluencers, in particular, may directly or indirectly inspire political activism in the form of environmental activism.The term opinion leaders was coined by Katz andLazarsfeld (1955/2006) and embedded in their Two-Step Flow Hypothesis, according to which the mass media are not the only potential influence on the wider public.Instead, they argue that so-called opinion leaders mediate and influence public perceptions (Katz & Lazarsfeld, 1955/2006).Additionally, SMIs may influence the attitudes and behaviors of other users via social learning (Bandura, 1977).

Can influencers sell activism?
Despite cultural pessimistic views on new technologies like the internet and SNSs, a meta-analysis investigating the effects of internet use on civic and political engagement did not find a generalized negative effect (Boulianne, 2009).Scholars have tried to narrow down the specific internet-and SNS-related usage characteristics that may spark engagement and activism.Research has shown that use of Facebook (Valenzuela et al., 2012) and general SNS use (Leyva, 2016) are associated with increased (environmental) activism in adolescents and young adults.Beyond specialized applications, the topical diversity on SNSs may in itself increase the probability of political content reaching politically uninterested or barely interested users (see Matthes et al., 2020).As such, it might give rise to political activism.Activism can be defined as a "process of collective, democratic, research-informed and negotiated problem-solving action on socio-environmental problems" (Reis, 2020, p. 140).Given the significance of collectivity in activist endeavors, a closer look at activism on SNSs is warranted.Treré (2015) highlights the role of SNSs in enabling collective identity formation among young Mexican activists and facilitating practices of playful activism in a digital comfort zone.The influence of social media became especially salient in the context of the Arab Spring, where it empowered oppositional movements and helped transform activism from the digital into the analog world (Lim, 2012).However, it is unlikely that SNS use in general increases political participation.
Participatory efforts depend, among other factors such as perceived goal-attainability, on perceived efficacy (Jung et al., 2011).Subsequently, the means to achieve a political goal can be characterized by the effort required (Kruglanski et al., 2015).Taking the motivational component behind participatory efforts into account, Knoll et al. (2020) theorize about the psychological processes driving the effects of social media use on political participation in their SMPPM.Most importantly for our case, the authors draw upon goal systems theory and distinguish high-effort forms of political participation from low-effort forms (Knoll et al., 2020).Although previous studies distinguish between online and offline political participation (e.g., Vitak et al., 2011), we align with this conceptualization (Knoll et al., 2020;Nanz et al., 2020)  distinguish low-from high-effort activism.Given the significance of motivational state and goal attainability in environmental activism, the distinctive feature effort seems to be appropriate for grasping political participation and facets of its subdimension environmental activism.Notably, Vitak et al. (2011) also report differences between activities that "require[d] more time and effort" (p.110), related to both online and offline participation.Forms of low-effort activism require and cost little time and energy (Knoll et al., 2020;Nanz et al., 2020); they may include conversations with strong ties to the issue at hand, sharing political information, or gathering information about a certain topic.In contrast, high-effort activism requires higher levels of commitment since the costs are generally higher (Knoll et al., 2020;Nanz et al., 2020).It may involve protesting, taking a public stance, or correcting misinformation online.
Taken together, greenfluencers can be regarded as opinion leaders who might inspire others to adapt their behavior via social learning (Bandura, 1977).An important precondition of this, however, may be engagement with greenfluencers.Engagement with opinion leaders can diffuse ideas and behaviors beneficial for combating "complex sustainability issues such as climate change" (Keys et al., 2010, p. 194).Yet it is unclear whether engagement with greenfluencers on social media, e.g., commenting on posts or writing them private messages, is associated with environmental activism.Based on the greenfluencers' status as digital opinion leaders, we hypothesize that such engagement will be associated with higher levels of environmental activism.

H1.
Engagement with green influencers on social media positively relates to a) low-effort and b) high-effort environmental activism.

More than an influence: parasocial relationships with greenfluencers
For adolescents and young adults, engaging with greenfluencers can be more than just an entertaining or educational way to spend time.The concept of parasocial interactions (PSIs) and parasocial relationships (PSRs) was introduced in the 1960s by Horton and Wohl (1956) to describe feelings of intimacy between spectators and media personae.While PSI is restricted to periods of exposure, PSR captures a long-term emotional bond that can, in many aspects, be compared to an actual social relationship (Giles, 2002).As such, PSRs endure beyond exposures and specific parasocial interactions (Dibble et al., 2016).Importantly, the term was originally coined in the context of mass-mediated communication with a clear distinction between performer/persona and spectator(s).
Despite the fact that the formative component of SNSs implies intimacy and makes direct contact between users and SMIs possible, we argue that the relationships between them should be considered parasocial.Even though user-to-user interactions and user-follower interactions are theoretically enabled through SNSs, their dynamics differ drastically.User-user relationships are reciprocal (Baek et al., 2013), while user-SMI relationships are unidirectional.Put differently, whereas the user is well aware of the activities of the SMI, the SMI may be completely oblivious to the existence and online activities of the user.Thus, we conceptualize the influencer-follower relationship as parasocial.
Previous studies suggest that following an SMI on an SNS is associated with higher levels of PSR with that specific SMI compared to not following that SMI (Breves et al., 2021).The distinction between SMI followers and non-followers made by Breves et al. (2021) is highly appropriate for an experimental setting.However, the driving force behind the establishment of a PSR, as reported by Breves et al. (2021), may not be follower status but is associated with the increase in engagement with SMIs concomitant with follower status.Previously described network characteristics, or "perceived reciprocity" (Breves et al., 2021(Breves et al., , p. 1212)), may foster the transition from engagement with greenfluencers to establishment of a PSR.Therefore, we hypothesize that engagement with greenfluencers will be associated with PSR with greenfluencers.

H2.
Engagement with green influencers on social media positively relates to formation of a parasocial relationship.

The persuasiveness of parasocial relationships
Notably, PSR with SMIs is first and foremost researched in an advertising and marketing context, while the role of PSR in mediating politically relevant outcomes beyond consumer decisions is generally under-researched.It is well established that not all information is processed equally (e.g., Chaiken, 1980;Petty & Cacioppo, 1986).Apart from intraindividual factors (e.g., pertaining to motivational state), contextual cues shape affective, attitudinal, and behavioral outcomes.Put differently, contextual factors like perceived communicator characteristics can serve as heuristics, i.e., mental shortcuts, that may severely impact the processing of the communicated information (e.g., Chaiken, 1980).Recent research has extended these assumptions and, for instance, proposed a positive halo effect in online celebrity endorsements (Djafarova & Rushworth, 2017).Other empirical studies in the broader advertising context point in a similar direction and suggest that PSR predicts whether users are considering purchasing advertised products (Breves et al., 2021;Hwang & Zhang, 2018;Su et al., 2021).
However, little is known about the effects of PSR with influencers beyond the advertising and marketing perspective.A meta-analysis by Tukachinsky et al. (2020) further highlights the potentially persuasive role of PSRs throughout different domains.Su et al. (2021) find that PSR increases informational influence.In another study, PSR predicted repeated viewing of live-streamers (Lim et al., 2020).Persuasiveness research has well established that repeated exposure alters the elaboration of an argument (Cacioppo & Petty, 1979).Repeated exposure is associated with increased cognitive fluency, which may, in turn, make a favorable elaboration more likely (see Koch, 2017).This observation is highly relevant for content on SNSs in general and SMI engagement in particular.After all, engagement with an SMI on an SNS may affect the platform's algorithm and, as such, facilitate future engagement even more.Following the persuasion argument derived from influencer marketing research and studies investigating general effects of PSR, we hypothesize a positive relationship between PSR with greenfluencers and low-as well as high-effort environmental activism.

H3.
A parasocial relationship with green influencers positively relates to a) low-and b) high-effort environmental activism in adolescents and young adults.

The moderating role of environmental knowledge
In recent years, it has become increasingly apparent that young adults are strongly concerned and worried about climate change and environmental degradation (Ipsos, 2021).However, adolescents' and young adults' general knowledge about environmental issues and their causes varies widely (e.g., Benton, 1994).While it is established that middle-aged adults with a college degree tend to have more environmental knowledge compared to other age groups, previous research does not provide consistent results on how environmental knowledge is distributed among young people (e.g., Robelia & Murphy, 2012).For instance, DeChano (2006) showed that young adults aged 17-19 years have rather low environmental knowledge.In contrast, Sousa et al. (2020) suggested that students aged 18 years plus are not only environmentally aware but also knowledgeable.This illustrates the fact that young adults' level of environmental knowledge depends on various factors and that it can vary depending on these factors (e.g., Goldman et al., 2015).Thus, adolescents and young adults should not be viewed as a homogenous group where everyone has the same level of environmental knowledge.
However, the level of young adults' environmental knowledge is crucial, as it may influence young adults' information processing of H. Knupfer et al. environmental messages and, in turn, may also influence their environmental behavior, i.e., their environmental activism (e.g., Michalos et al., 2009, p. 1;Petty & Cacioppo, 1986).In line with this, previous research has shown that, besides cognitive resource variables such as distraction and time pressure, knowledge could affect the mode of information processing, too (Petty et al., 1976;Wood, 1982).More precisely, prior knowledge about the content of a message positively influences individuals' ability to process, understand, and make use of a message's information (Petty & Cacioppo, 1986).
Drawing on the heuristic-systematic model (HSM; Chaiken, 1980), information is processed either systematically or heuristically, depending on the individual's prior knowledge (Todorov et al., 2002).Whereas high cognitive abilities to process information through high knowledge may foster systematic information processing, a lack of these knowledge-related cognitive abilities could lead to superficial heuristic information processing.When individuals process information in a systematic way, they tend to elaborate more deeply on the available information before they reject or accept it.In this mode, the effect of the message on the audience is influenced by individuals' understanding of, cognitively elaborating on, and scrutinizing of the message's content.In line with this, Chaiken (1980) showed that for individuals highly involved with the content of a message, the information was processed systematically: The effects of the message were stronger when it was based on a number of arguments compared to no arguments, independent of communicator characteristics.Accordingly, Chaiken and Eagly (1976) showed that systematic information processing due to high involvement could facilitate persuasion processes.
Since one key indicator for environmental involvement is environmental knowledge (Parguel et al., 2015), we argue that young adults high in environmental knowledge might understand environmental information better and might be better able to make use of it compared to individuals with low levels of environmental knowledge (Chaiken, 1980;Petty & Cacioppo, 1986).Further, young adults with high environmental knowledge might process content from greenfluencers with whom they engage in a systematic way, based on the quality of the message itself, i.e., the content of the message (Chaiken, 1980).Hence, if content from greenfluencers calling for environmental behavior is assessed by young adults as valid due to thoughtful evaluation based on high environmental knowledge, there might exist a positive association with young adults' intentions to engage in environmental activism.Thus, we hypothesize: H4.For adolescents and young adults with high environmental knowledge, engagement with green influencers is associated with higher levels of a) low-effort environmental activism and b) high-effort environmental activism compared to low environmentally knowledgeable adolescents and young adults.
As previously discussed, not all young adults are equally environmentally knowledgeable (e.g., DeChano, 2006;Sousa et al., 2020).Since knowledge might affect the mode of information processing (Petty et al., 1976;Wood, 1982), adolescents and young adults less environmentally knowledgeable could perceive content from greenfluencers with whom they engage differently than do highly knowledgeable young adults.Drawing on the HSM (Chaiken, 1980), individuals with low levels of knowledge might process information in a heuristic mode, where information processing is nonanalytic.In this mode, information processing is guided by "less important informational cues" such as the characteristics of the communicator (Todorov et al., 2002, p. 196).Chaiken (1980) empirically supported this notion by showing that less involved individuals were influenced more strongly by the likability of the communicator than the arguments used in the message.Similarly, Tortosa-Edo et al. (2014) reported that individuals who are not involved with environmental issues are more likely to engage in heuristic information processing than individuals who are highly involved.
In the context of environmental communication from greenfluencers, we argue that if individuals have lower levels of knowledge, they might assess the validity of the information based on heuristic communicator cues such as their quality of relationship with the SMI.More precisely, previous research has shown that besides experts and other trustworthy persons, individuals tend to "generally agree" with people they like or with communicators with whom they perceive interpersonal similarity (e.g., Chaiken, 1980;Stotland & Canon, 1972).In an experimental study, Naderer (2022) found that perceived similarity with an SMI increased intended political action taking in individuals who were not interested in politics and were exposed to an unlikely source of political information.Although this study did not explicitly include PSRs, it emphasizes the importance of affective components related to communicator characteristics in shaping persuasive outcomes.Since PSRs are based on likability, trust, or perceived similarity (e.g., Hartmann et al., 2008), we argue that adolescents and young adults with low levels of environmental knowledge rely more strongly on the PSR with greenfluencers as a heuristic cue when deciding to accept or reject their calls to environmental activism than more environmentally knowledgeable adolescents and young adults.Hence, we derive our hypothesis: H5.For adolescents and young adults with less environmental knowledge, a PSR with green influencers is associated with higher levels of a) low-effort environmental activism and b) high-effort environmental activism compared to highly environmentally knowledgeable adolescents and young adults.
A conceptual model including all hypothesized associations is displayed in Fig. 1.

Sample and procedure
A cross-sectional online survey among adolescents and young adults (16-25 years old) in Germany was administered to test our hypotheses.Data was collected between mid-July and mid-August 2021.Participants had to be smartphone users and current or former users of social media.These preconditions were necessary so we could draw inferences about engagement with greenfluencers on SNSs.We refrained from using "following greenfluencers on social media" as an inclusion criterion, given that SNS users do not necessarily have to follow greenfluencers to engage with them on social media due to, for instance, incidental exposure (e.g., Scharkow et al., 2020).In order to reach a substantial sample size in our targeted age group, two professional sampling agencies were employed to recruit participants (n 1 = 440; n 2 = 425). 2To ensure sufficient quality of the data, three attention check items were included (e.g., "My birthday is on February 30"; Dunn et al., 2018).Respondents who failed to respond to these items correctly were excluded.Additionally, speeders, defined as respondents who completed the survey faster than one-third of the median total duration, were excluded from further analyses.To sufficiently represent the targeted population, the sample was quota-based regarding gender (53.9% female, 0.7% diverse) and age (M = 21.14 years old, SD = 2.73).Additionally, a soft quota for education was applied (36.4% without degree, with elementary or secondary school degree, 50.3% with high school degree, 13.3% with university degree).The final sample included N = 865 respondents.The data set is stored online and publicly accessible: https://osf.io/5e3a8/?view_only=4fe5ac3f6d2349d59bc23cb961b c1ad8.Before starting the data collection, we sought approval of the Institutional Review Board of the Department of Communication, University of Vienna (ID: 20210602_039).

Measures
If not indicated otherwise, all items were measured on 7-point Likert-2 Sample provider was included as a control variable in all analyses.
H. Knupfer et al. type scales ranging from 1 ("strongly disagree") to 7 ("strongly agree").All measures can be found in Appendix A. Before answering the questions related to greenfluencers, participants were provided with a short introductory text including a definition of SMIs 3 and green influencers. 4

Engagement with greenfluencers
Engagement with greenfluencers was gauged with three selfdeveloped items (e.g., "When my favorite green influencers are asking their followers about something, I message them or comment.").The items showed sufficient internal consistency (Cronbach's α = 0.90) and were merged to a mean-based index (M = 2.95, SD = 1.64).In the questionnaire, the items were preceded by an introduction that instructed participants who did not follow greenfluencers on social media to respond based on what they generally think about greenfluencers (see Appendix A).Based on this introduction, no separate answer option was provided for non-followers.

Environmental activism
Environmental activism was measured with 17 items that covered participating in different facets of environmental activism in the past two months, including online corrective effort against climate misinformation, researching about climate change, or protesting.The items were partly based on the pro-environmental activist behavior scale developed by Schmitt et al. (2019).Principal component analysis with oblique rotation revealed a two-factor solution with low-effort environmental activism (seven items; e.g., In the past two months, I have "reminded older generations of their responsibility when it comes to climate change" and "[…] actively engaged with scientific findings on the subject of climate change") and high-effort environmental activism (ten items; e.g., In the past two months, I have "participated in radical protest on the subject of climate change" and "[…] I have participated in discussions on the internet on the subject of sustainability").The factor loadings and the wordings of all environmental activism items are provided in Appendix A. The factorial structure proved to be reliable for low-effort environmental activism (Cronbach's α = 0.93) and high-effort environmental activism (Cronbach's α = 0.96).Analog to engagement with greenfluencers, both factors were combined to mean-based indices (M low = 3.29, SD low = 1.54;M high = 2.87, SD high = 1.59).

PSR and environmental knowledge
We used parts of the parasocial relationship scale developed by Hartmann et al. (2008) and adapted the items to fit the purpose of this study.The original 13-item scale was cut to three items that covered amicable feelings toward greenfluencers and general approval of them (e.g., "I miss my favorite green influencers when I haven't seen them on social media for a while").The scale showed good internal reliability (Cronbach's α = 0.87).Again, the items were combined to a mean-based index (M = 2.96, SD = 1.59).PSR was measured right after engagement with greenfluencers, ensuring that the instructions provided for individuals not following greenfluencers were still salient.Again, we chose not to include an answer option for non-followers, since following facilitates PSR development (Breves et al., 2021) but is not a necessary precondition for establishing a PSR.
Based on Geiger et al. (2019), environmental knowledge was assessed using five single-choice knowledge items with a total of four answer options each.Among the four answer options, three options were always incorrect, and one was always correct.The chosen items covered the environmental knowledge subtopics climate, consumption behavior, and society/politics.The items were separately dummy coded into "correct" and "incorrect" and then combined to a sum score indicating overall environmental knowledge.On average, respondents were able to correctly answer 2.37 out of the five questions (M = 2.37, SD = 1.43).

Control variables
Environmental activism can be influenced by factors besides PSRs with greenfluencers and/or engagement with greenfluencers on social media.Therefore, a number of potentially confounding variables were statistically controlled for.Namely, we controlled for age (in years), female gender (dummy-coded), diverse gender (dummy-coded), sample provider (dummy-coded), low education level (dummy-coded), medium education level (dummy-coded), political ideology, and environmental concern.Past studies indicate that political ideology might influence outcomes related to environmental support in young adults (e.g., Harring & Sohlberg, 2017), thereby potentially interacting with our hypotheses.To control for this, participants were asked to position themselves on a 10-point scale of political ideology, ranging from left (1) to right (10) (M = 4.55, SD = 1.93).Environmental concern was gauged with a scale developed by Schuhwerk and Lefkoff-Hagius (1995) and adapted to the purpose of this study.The scale consisted of three items (e.g., "The state of the environment greatly affects my quality of life").
That proved to be reliable (Cronbach's α = 0.82).Thus, the items were combined to a mean-based index (M = 4.02, SD = 1.45).Additionally, following a greenfluencer on social media was assessed with a dummy variable, with n = 378 (43.7%) participants indicating following a greenfluencer and n = 487 (56.3%) not following a greenfluencer.This 3 "On social media channels such as Instagram or YouTube, there are socalled influencers.These are social media users who usually have more than 10,000 followers and express their opinions on certain topics, brands or products in posts, pictures and videos." 4 "These are social media users with a wide reach who specifically focus on topics such as sustainability and environmental awareness." H. Knupfer et al. dummy variable was included as a control variable to account for differences related to greenfluencer following.

Statistical analysis
Since our data did not meet the requirements for latent path analysis, we have not hypothesized reciprocal effects, and because it is uncommon in our research field to do moderated mediations within a latent framework, we conducted our statistical analysis within a manifest variable framework (e.g., Little et al., 2006).As the lavaan package in R can be used for both latent frameworks as well as manifest ones, all analyses were estimated using the lavaan package in R involving 5000 bootstrapping samples (Rosseel, 2012).Continuous variables included in our theoretical model were mean-centered prior to the analyses.In order to account for non-normality, we used a robust maximum likelihood estimator.

Results
Results indicated that engagement with greenfluencers on SNSs was positively associated with both low-effort environmental activism (b = 0.14, SE = 0.04, p < .01)and high-effort environmental activism (b = 0.29, SE = 0.04, p < .001).Hence, H1 was supported.Further, results showed that H2 was supported.Engagement with greenfluencers on social media was positively associated with the formation of a PSR with greenfluencers (b = 0.74, SE = 0.02, p < .001).H3, stating that the PSR with greenfluencers is related to low-effort environmental activism as well as high-effort environmental activism in adolescents and young adults, also found support.Results showed that PSR with greenfluencers was positively associated with low-effort activism (b = 0.41, SE = 0.04, p < .001) as well as with high-effort environmental activism (b = 0.44, SE = 0.04, p < .001).H4 was only partly supported.While the positive relationship between engagement with greenfluencers and low-effort environmental activism was not moderated by environmental knowledge (b = 0.04, SE = 0.03, p = .15),the moderating effect of environmental knowledge on high-effort environmental activism was positive and significant (b = 0.07, SE = 0.03, p = .03).This significant interaction indicates that with higher levels of environmental knowledge, the positive association of engagement with greenfluencers with high-effort environmental activism becomes stronger.Although the positive association of engagement with high-effort activism is present for adolescents and young adults with lower levels of knowledge as well, the effect is weaker.The interaction effect of engagement and environmental knowledge on high-effort environmental activism is plotted in Fig. 2.
Similarly, we found only partial support for H5.Results indicated that environmental knowledge did not moderate the association between PSR with greenfluencers and low-effort environmental activism (b = − 0.01, SE = 0.03, p = .86).In line with H5b, environmental knowledge moderated the association between PSR with greenfluencers and high-effort environmental activism negatively (b = − 0.07, SE = 0.03, p = .03).Thus, although PSR with greenfluencers is positively associated with high-effort environmental activism, the strength of the relationship depends on environmental knowledge.The relationship is weaker in individuals with higher levels of environmental knowledge compared to those with lower levels of environmental knowledge.As such, the positive association between PSR and high-effort activism is strongest for adolescents and young adults with lower levels of environmental knowledge.The interaction effect of PSR and environmental knowledge on high-effort environmental activism is shown in Fig. 3.A table of the main results is provided in Appendix B.

Discussion
Social media provide a vast opportunity for adolescents and young adults to be exposed to and engage with greenfluencers.In contrast to general SMIs, greenfluencers focus their online efforts on sustainability and may promote sustainable consumption and/or incite environmental activism.Applying a moderated mediation model and controlling for a number of potentially confounding variables, we found that engagement with greenfluencers is associated with higher levels of low-and higheffort environmental activism.Apart from this direct association, the indirect path via PSR with greenfluencers, a distinctive feature of SMIs as media personae (Horton & Wohl, 1956), was also significantly positive.Thus, engagement with greenfluencers on social media is associated with higher levels of low-and high-effort environmental activism both directly and mediated through PSR.
Previous research has emphasized the role that environmental knowledge might play in instigating environmental activism (e.g., Michalos et al., 2009, p. 1).The HSM (Chaiken, 1980) establishes that preexisting knowledge fosters systematic elaboration and processing of relevant new information, thereby reinforcing a potentially persuasive argument.Our results clearly indicate that environmental knowledge affects outcomes in low-and high-effort environmental activism in different ways.These results also underline the previously established distinction between low-effort and high-effort activism (see Knoll et al., 2020;Nanz et al., 2020).
For low-effort environmental activism, we could not find significant moderating effects of environmental knowledge.Although contrasting our initial hypothesis, these null findings may be explained by revisiting how low-effort activism is conceptualized.Adolescents and young adults in our sample reported rather high levels of environmental concern, indicating that they are generally aware of the threat posed by sustainability issues like the climate crisis.Thus, young individuals who already engage with greenfluencers online (and have developed a PSR with them) might not need the cognitive component of environmental knowledge to adapt their behavior and speak up on behalf of sustainability, as long as these activities require little effort.
In line with our hypothesis and the HSM (Chaiken, 1980), we found that environmental knowledge positively moderates the association of engagement with greenfluencers and high-effort environmental activism.This suggests that higher levels of environmental knowledge are associated with a stronger positive relationship between engagement with greenfluencers and high-effort activism.This may be explained by the fact that highly knowledgeable young individuals are better able to understand the environmental information provided by greenfluencers, and thus, they are better able to apply it in the form of high-effort environmental activism.In contrast, the interaction of PSR with greenfluencers and environmental knowledge was negative, meaning that the positive effect of PSR on high-effort environmental activism was stronger for adolescents and young adults with lower levels of environmental knowledge.
These findings point to the distinctive function that greenfluencers may carry out for adolescents and young adults who are not (yet) knowledgeable in environmental matters.While it seems that knowledgeable users profit from the engagement with greenfluencers more strongly by systematically processing the content and responding to it with higher levels of high-effort environmental activism, less knowledgeable users profit more strongly from the affective component captured in PSR and rely more heavily on heuristic processing.In other words, since less knowledgeable adults are not able to analytically process the information provided by greenfluencers due to lacking information structures, they might process the information via heuristic cues such as characteristics of the communicator or the quality of the relationship with the greenfluencer (Chaiken, 1980;Todorov et al., 2002).To sum it up, greenfluencers may positively influence young individuals with high environmental knowledge and young individuals with low environmental knowledge via two distinct routes of information processing, the systematic route via engagement and the heuristic route via engagement and PSR.
Previous research has shown that, especially for young adults, environmental knowledge is an important predictor of engagement in environmental behaviors (e.g., Michalos et al., 2009, p. 1;Thathong & Leopenwong, 2014).For instance, young adults with high environmental knowledge are more willing to vote for "green" parties than are young adults with low environmental knowledge (Goldman et al., 2015).However, we found a negative direct association between environmental knowledge and high-effort activism.Hence, young adults Fig. 3. Plotted interaction effect of parasocial relationship with greenfluencers and environmental knowledge on high-effort environmental activism.
high in environmental knowledge in our sample tended to engage to a lesser extent in high-effort activism than young adults low in environmental knowledge.It could be that environmental knowledge, including awareness about the environmental benefits of high-effort environmental activism, might hinder young adults from engaging in it because the individual costs of engaging could be seen as too high compared to the collective benefits.Put differently, high environmental knowledge alone might not be sufficient for young adults to engage in high-effort environmental activism.This is in line with previous studies showing that besides environmental knowledge, environmental attitudes and perceptions of moral obligations are crucial to enhancing young adults' engagement in environmental activism (Piyapong, 2020).

Limitations
Although the results are mostly in line with our theorized assumptions, it is important to keep a few important limitations in mind.First, we applied a cross-sectional study design, which does not allow for inferring causality.Further longitudinal and experimental studies are needed to shed light on the effects of greenfluencer engagement on lowand high-effort environmental activism.It would be especially important to assess impacts on environmental activism in a longitudinal study to draw conclusions about the persistence of persuasion effects of greenfluencers on adolescents and young adults over time.Second, although we defined greenfluencers in the online questionnaire, it is possible that the respondents held different perceptions about what constitutes a greenfluencer.Hence, we need experimental studies that directly manipulate greenfluencer exposure to break down the effects of specific types of greenfluencers.More generally speaking, this also relates to the paradoxical nature of greenfluencers, who occupy a gray area with fluid transitions between consumption and mobilization, advertising, and activism.To clarify the distinctive features of different SMI types, including greenfluencers, careful theoretical conceptualization and empirical testing should be considered and implemented in future research.Another crucial point of concern is that in our young sample, fewer than 50 percent of the participants indicated following a greenfluencer.Arguably, this makes assessing PSRs with greenfluencers difficult.Still, we believe that our approach is valuable because, first, individuals do not need to follow greenfluencers to engage or establish parasocial bonds with them.While following an influencer on social media is associated with higher exposure to this influencer's content and may give rise to more engagement with this influencer, following is not a necessary precondition to exposure.In a similar vein, users do not need to follow influencers to get in touch with them and engage, for instance by commenting.Greenfluencers are very prominent on social media, and thus, users from very different backgrounds can be exposed to greenfluencers and their content without actively following them.As pointed out before, many greenfluencers in Germany have a large following base, increasing the likelihood of their content dispersing to users who are not per se interested in the topic of sustainability.Second, since our sample is homogenous regarding age but diverse in terms of other characteristics, we anticipated possible variation in following greenfluencers.Thus, we not only defined greenfluencers in the introduction of our questionnaire, we also provided instructions on how to proceed for individuals who do not follow greenfluencers (see Appendix A).Last, we included "following greenfluencers" as a control variable in our statistical analyses.While future studies should address the establishment of a PSR in depth regarding followers and non-followers of greenfluencers, we sought to circumvent bias by statistically controlling for following greenfluencers.
Third, we looked at only one dimension of environmental knowledge, namely system knowledge (e.g., Frick et al., 2004).According to Frick et al. (2004), action-related knowledge and effectiveness knowledge are additional dimensions of environmental knowledge that could provide deeper insights when investigating environmental behavior.Future research should therefore take moderating effects of different dimensions of environmental knowledge into account.

Theoretical implications
Although the limitations are important to acknowledge, the current study advances the theoretical debate about possible associations between engagement on SNSs and environmental activism as a specific form of political participation.The results are generally in line with the HSM (Chaiken, 1980), indicating that topical knowledge can shape high environmental activism in young individuals.As such, the study further attests to the crucial distinction between low-effort and high-effort political participation proposed by Knoll et al. (2020) and Nanz et al. (2020) in the social media political participation model (SMPPM).In contrast to scholars who distinguish offline from online participation, the SMPPM takes a motivational approach to account for differences in political participation.Since environmental activism constitutes a specific form of participation, the general accordance of our results with the SMPPM speaks for a broader applicability of the model.

Practical implications
Despite the outlined limitations, we believe that this study has taken an important first step in disentangling the role that greenfluencers can play in inspiring adolescents' and young adults' environmental activism.Given that environmental movements like Fridays for Future have shown impressive mobilization potential among adolescents and young adults, the investigation of predictive factors associated with adolescents' and young adults' social media diet (i.e., engaging with greenfluencers on SNSs) is essential.Since adolescents and young adults are among the first to adopt new technologies, including new SNSs (Perrin, 2015), understanding the conditions and processes of SMI persuasiveness related to political participation will certainly continue to be a concern for researchers and practitioners in the years to come.Some scholars argue that engagement of the broader public is necessary to fight the climate crisis efficiently (Ockwell et al., 2009).Despite the ecological threat attributed to the climate crisis, it may also threaten wellbeing and mental health.Especially for adolescents and young adults, environmental activism may be a constructive way to foster perceived efficacy (Bandura, 1977) and ultimately cope with the psychological impacts of the climate crisis.Additionally, engaging in environmental activism may foster democratic processes and, as such, may in itself be beneficial to societies.SNSs can be a low-barrier entrance point for young individuals to develop such interests and get in touch with greenfluencers as environmental opinion leaders.Our results clearly indicate that engaging with greenfluencers on social media relates to low-effort as well as high-effort environmental activism, even in young individuals who have little environmental knowledge.

Conclusion
Overall, the present study tested associations between engagement with greenfluencers, PSR with greenfluencers, and low-and high-effort environmental activism in young individuals from Germany.Building on the HSM (Chaiken, 1980), environmental knowledge was included as a moderator.The results indicate that engaging with greenfluencers on SNSs is positively associated with both forms of environmental activism.This emphasizes the potential of greenfluencers as emerging communicators of sustainability issues to positively influence young people's environmental activism.
Apart from the direct relationship between engagement and environmental activism, affective bonds to greenfluencers, i.e., PSRs, mediate this path.Whereas environmental knowledge does not moderate outcomes related to low-effort environmental activism, it moderates the relationship between PSRs and high-effort environmental activism negatively and the association between engagement and high-effort environmental activism positively.These findings suggest that, in H. Knupfer et al. particular, less knowledgeable young individuals may profit from the parasocial bond they establish with greenfluencers.As such, engaging with greenfluencers on SNSs and establishing a PSR with them may be a means for spreading awareness about sustainability and possibly a gateway to environmental activism for users who so far have shown little interest in the topic.
Despite noteworthy limitations, this study has taken an innovative and important step in shedding light on young people's environmental activism and influencer-related characteristics, which can be regarded as particularly important given young individuals' highly SNS-driven media diet.It is also important to emphasize that sustainability concerns are likely to increase in the years to come.While detrimental effects of the changing climate are already palpable in many countries, the IPCC (2021) suggests that the impact and frequency of extreme weather events, for instance, will rise dramatically if the climate goals are not met.As such, broadening the knowledge on SNS usage-related factors that might foster environmental activism in young individuals and thereby increase public pressure on policymakers and companies is an important means to constructively navigate the climate crisis.
What does the carbon footprint of a product mean?☐ The typical staining of the sky that is caused by high CO2 concentrations.☒ The amount of all greenhouse gas emissions that is emitted over the lifecycle of a product.☐ The amount of CO2 a product emits when it corrodes.☐ The chemical change that is caused by CO2 in the atmosphere.
In which of the following domains is the most water consumed in everyday life?☒ Flushing the toilet.☐ Eating and drinking.☐ Washing dishes.☐ Doing laundry.
Compared to a calorie-equivalent amount of vegetables, the production of meat is … ☒ Ten times more environmentally detrimental.☐ Equally environmentally detrimental.☐ Five times more environmentally detrimental.☐ Half as environmentally detrimental.
Engagement with greenfluencers (1strongly disagree, 7strongly agree).In this section, we would like to know how you relate to green influencers that you particularly like.When answering the questions, please think about the green influencers you like.
If you don't have a favorite green influencer, then simply answer in terms of what you think about green influencers in general.
When my favorite green influencers ask their followers something, I write them a message or comment.I like to participate in the online campaigns of my favorite green influencers.I interact with my favorite green influencers through my likes, messages, or comments.
Please indicate again how the following statements apply to you personally.
I feel like my favorite green influencers are like old friends to me.I miss my favorite green influencers when I haven't seen them on social media for a long time.I agree with most of the actions of my favorite green influencers.
I am willing to make large sacrifices to protect the environment.I deeply care about the environment.The state of the environment greatly affects my quality of life.
Appendix B

Fig. 2 .
Fig.2.Plotted interaction effect of engagement with greenfluencers and environmental knowledge on high-effort environmental activism.

Table B .1
Pattern matrix of a principal component analysis on mediator and dependent variables using oblimin rotation to false messages on the internet that cast doubt on man-made climate change.when someone on the internet has questioned man-made climate change with false information.involved with groups/movements whose main goal is to preserve or protect the environment.In the past two months … I specifically searched for further information on the topic of the environment.

Table B .
1 (continued ) I have encouraged my family and friends to reduce greenhouse gases and energy consumption.older generations aware of their responsibility in the area of climate change.to older people what responsibility they bear in the matter of climate change.Note.N = 865; Factor loadings ≥ 0.65 are shown in bold.