The Corporate Social Responsibility (CSR) in the Travel Supply Chain: A Literature Review

Traditional travel agencies and tour operators are recognized as relevant stakeholders in the tourism distribution chain, even though their role as transforming agents in the achievement of more sustainable tourism is beginning to be accepted. This document collects the main topics and the most recent approaches from the academic literature in its analysis of Corporate Social Responsibility (CSR) practices developed by these intermediaries. The work has been structured around six recurring themes in most of the studies carried out: the new intermediaries that operate on the Internet; the role of travel agencies and tour operators in tourism sustainability; the influence of the size of the company; CSR as a disruptive innovation in this sector; the potential of the sustainable tourism supply chain; and the motivations and attitudes of the managers of these businesses when they engage with responsibility. This last topic is developed in greater detail since it is closely linked to the previous ones and dictates in most cases the meaning and function of the sustainable performance.


Introduction
As far as sustainability is concerned, it seems to be consensus appreciating it as a balance between economic, socio-cultural and environmental returns and impacts [1]. Concerning the enterprise level, one of the most prolific trends in the analysis of sustainability links it with CSR, understanding sustainability as the ultimate objective of maintaining indefinitely the viability of our economies, the societies in which they are immersed and the environment on which they depend, while CSR refers to business activities, particularly their contribution to achieving this economic, social and environmental sustainability [2]. Although the direct and close relationship of the tourism sector with its physical, economic and social environment is increasingly evident, the research production in the field of tourism and the management on CSR is still scarce compared to other sectors [3], even if a soaring interest in it is noticeable [4,5]. It is important to bear in mind that tourism is not a homogeneous productive sector, but rather a multisector made up of a great diversity of companies from various sectors -hotels, transport, travel agencies, tour operators, restaurants, activities providers, etc. -with very heterogeneous characteristics, which makes their study and holistic analysis difficult from a traditional microeconomic perspective, usually applied to the other economic sectors based on the goods they produce. To solve this obstacle, various authors advocate the separate study of these sectors, adapting the research to each of them and with different perspectives [6,7].
This paper aims to explore what has been studied related with CSR about one of the less investigated stakeholders in tourism: the intermediaries, and among them particularly the traditional intermediaries, tour operators and travel agencies. Intermediary tourism companies play a decisive role in promoting, supplying products and assisting in the exchange of information [8], where some of them can shape the travel volume and movements, combine and stimulate the thoughts and practices of tourism actors, and influence in the destinations and communities [9,10]. The Eurobarometer statistical analyses establish that 20% of the total travel bookings made by Europeans are contracted in an offline travel agency and that about 15% of the reserved trips were circuits planned by tour operators. And these figures are not only stabilized but even upwards in recent years [11]. Besides, figures are higher if we consider their economic weight since most of the reservations made through the offline intermediaries involve a greater outlay by the consumer, in such a way that it is estimated that 30% of tourism income flows through these intermediaries. In addition, it is also known that in certain countries, such as those in southern Europe or in developing countries, these percentages tend to amount to about 10 percentage points or even more [12]. Consequently, the decision of those intermediaries to become progressively involved in the use of CSR seems relevant, on the one hand, due to greater consumer awareness and receptivity towards ecologically and socially compatible behaviors [13], and on the other hand, on account of their central role in the distribution chain. These compelling reasons warrant why it begins to be considered important that these stakeholders are responsible and focused on the three pillars of sustainable tourism and CSR: the environment, socio-cultural aspects and the economy [14][15][16][17].
Additionally, during the last decades, the evolution of the Information and Communication Technologies (ICT) based on the Internet have questioned the structure of the existing tourism distribution channel and the role played by some of its stakeholders, mainly the traditional firms, leading to new processes such as reintermediation, disintermediation or hypermediation [18,19]. In this context, intermediary companies have made great efforts in innovating their processes and products, in achieving revenue growth, and in maintaining or improving their profit margins. However, innovations are often costly and time consuming, requiring considerable investment. In any case, it is understood that the innovation process in tourism intermediation must continue to advance in the use of new tools and, above all, in collaboration between all members of the value chain [20].
For many researches, CSR must be understood as an innovative key factor for competitiveness and development in all the tourism industry, including its intermediaries [21,22], especially in crisis situations. In contexts of economic and social crisis, business organizations are considered as one of the clues in their overcoming, in particular, given the evolution in society's expectations regarding the role of companies as citizens with obligations [23]. The current Covid-19 crisis has severely impacted on the tourism industry but also seems to offer an opportunity of innovation [12]. Then, it is not surprising that some authors argue that this pandemic depression may offer an opportunity to rethink and reset tourism towards a better path for the future [24,25]. Specifically, for the intermediaries to develop more than ever their ability to take advantage of their capacity to add value through their provision of security, guarantee, advice, personalization, proximity and access to proven information, all of them upward values among tourism consumers in the post-Covid era. Reliably, a reconfiguration of the sector is intuited, whether it would be desirable that it was done by equipping these stakeholders with sustainable strategies and tools than encouraging CSR. Given its central situation in the tourism market, an analysis turns out to be pertinent of why and how these enterprises are acquiring their responsibility in the actual crisis.

Corporate Social Responsibility in the tourism industry
Tourism is, perhaps, the industry that shows the most significant growth rates, in relation to the contribution to the GDP and employment of many countries. It involves both benefits and tensions and conflicts [26], which is why it is key to mitigate the negative repercussions that occur in it, not only for the good of the environment and the society but also for the survival of the industry itself [27]. In this sense, although the relationship between tourism and sustainability has been extensively outlined [28], the same has not happened with the approaches of the tourism industry to the challenges of this sustainability. Nevertheless, there is a general agreement that the answer in this analysis of the tourism companies must be given by CSR [29].
Due to the comparatively recent pursuit of this field, there are still no clear standards on how to implement CSR in the firms related to tourism activity [29,30]. The studies continually present inconclusive or contradictory findings regarding the financial impact [31], often with meaningless CSR reports [32] and causing consumer cynicism about proposals perceived as a facelift [33]. The problem derives from the same definition of what CSR is or should be in the tourism sector, applying indistinctly the numerous definitions of the term existing in the generalist literature, as well as its models and indicators, which denotes a lack of critical conceptualization for the sector, especially because its own peculiarities are not taken into account [30].
Overall, the hotel sector monopolizes most of the carried out analyses to date, followed far behind by aviation [34]. Therefore, the rest of the tourism sectors are relegated to sporadic studies, although with an increasing presence in the literature [5,17]. Likewise, the researches on CSR in tourism are focused, for the most part, on certain aspects such as environmental measures or the communication of the undertaken actions [35], and not on a comprehensive application of the concept in the sector [36]. From the review of the state of the art, it can be deduced that the actions carried out in CSR are mainly focused on the environmental dimension [31,[37][38][39], with little disclosure of these policies [40], where those aspects that reduce costs and have repercussions in economic profitability, such as saving water or energy efficiency, are predominant [41].
Given the predominance of environmental issues, a large part of the published studies has been focused on the impacts produced by the tourism industry and on the creation and development of sustainability indicators for their management and control. In this line, several studies assess the use of energy in the sector and the advances in the commitment to the use of renewables, as well as the reduction of waste generation and water consumption [42]. To a lesser extent, although increasing in recent years, the researchers' agenda has been incorporating topics such as technology for sustainability [38], stakeholders participation [5], gender equality [43], business ethics [44,45], tourism in favor of poverty alleviation [46], certifications of sustainability [47], marketing [48], consumer perceptions [49,50] or the perspectives and intentions of employees [51]. Meanwhile, there is a growing academic interest in topics such as the role of the industry in promoting the sustainable consumption of tourism, the opportunities in the face of changing social habits, sustainable industrytourist communication, or the motivations and sustainable behaviors of the entrepreneurs [42].

Main academical discussions
For clarifying which were the major topics, a collection of articles on CSR and travel supply chain was obtained by querying the ISI Web of Knowledge (Web of Science) and Scopus databases, seeking research publications in the period between the years 2000 and 2020. These databases were chosen given its comprehensiveness of papers including titles from Emerald, Elsevier, Springer, Willey, Taylor & Francis, JStor, among others. After an exhaustive reading of the existing literature, six are the topics considered the most studied or relevant: a) the role of tourism intermediaries towards sustainability; b) the firms´ size factor; c) the online intermediaries´ commitment; d) the use of the CSR as an innovative strategy; e) the sustainable tourism supply chain; f) and the behavior and motivations of the managers facing CSR. In order to confirm the relevancy of these topics a content study has been carried out with the qualitative analysis software Nvivo, which has analyzed the 500 most mentioned words in all the articles, manually excluding the connecting words (prepositions, etc.) (see Figure 1). The results of this test offer clear coincidences with the assessments obtained from the reading of the articles, where words such as product, sustainability, operators, impact or consumer(s) (topic a), large, small, local or brand (topic b), online, media, global or Internet (topic c), innovation, future, quality, change, process (topic d), value, supply, community, suppliers (topic e), and behavior (topic f) confirm the relevance of the issues. As noted, CSR studies in tourism have focused mostly on hotels, and mainly on environmental elements, rather than on the intermediaries [14], despite the fact that these companies are key players in the tourism industry. Notwithstanding the tough competition due to the irruption of the ICT and the Internet, the evolution of the tourism industry has consolidated travel intermediaries in recent decades [52]. Nowadays, not only the traditional offline intermediaries and the online intermediaries live together in the tourism distribution channel, but each one takes advantage of their comparative assets and their market niches [53]. The review of the research in the field of CSR among these stakeholders, whatever the distribution channel is, reflects an imbalance between online and offline intermediaries´ studies, where traditional actors almost get all the weight of the literature, revealing a gap in the knowledge of how the commitment of the online intermediaries with CSR is. Nonetheless, an incipient interest is emerging in the academy trying to analyze this emptiness.
One of the main investigation lines followed by the research involves the role and possibilities that the intermediaries have (or should have) confronted the challenges of CSR, including the dealt barriers and the accomplished actions, as well as accepting and acknowledging their central role towards sustainability [9,10]. Generally, the major outbound tourism market structures are configured with a few large tour operators and travel agencies groups who control a high percentage of these markets and a large group of small and medium enterprises (SME) that try to survive them through product and quality differentiation [54,55]. Many studies have been focused on the different approaches that companies perform in their approach to CSR depending on their size. With that in mind, aligned with what happens in other well studied sectors, the differentiating factors for large companies were based on the nature of their structure and objectives, and for SMEs on their underlying motivations [56].
In addition, as indicated above, those traditional intermediaries that operated in the 1990s have taken advantage of the Internet and ICTs in recent decades to survive, where their main concern has been how to adopt and assimilate these innovations to obtain and maintain a competitive advantage [117,118]. Similarly, the adoption of CSR has been studied from its link with the innovation and these companies´ proven capacity for embracing it. Thus, intermediary managers can take advantage in change scenarios to use their CSR initiatives in an innovative way [88]. This can be induced through the design of strategies and the formulation of new forms of work, which in other sectors have led many companies to redefine their business models [119]. Undoubtedly, one of the most prolific fields of research between CSR and intermediaries has been to gain a clearer understanding of the specific sustainable requirements, opportunities and constraints at each point in the tourism supply chain in order to identify common success criteria, barriers and opportunities to sell more responsible tourism [100]. Furthermore, travel intermediaries have the ability to influence traveler´s choice, other supply chain member strategies, and destination development plans, so it has seemed to be useful in the understanding of their contribution to the sustainable tourism supply chain through CSR [57]. Finally, a last and really prolific line of research has identified a series of managers' motivations that may lead them to adopt CSR, all of them in accordance with the motivations set out for the industry in general and the tourism sector in particular [14,71,109]. Typically, these motives include responding to stakeholder pressure, gaining a competitive advantage, adhering to government regulation, avoiding fines and other regulatory actions, and improving the image. In addition, managers may also have internal ethical values to guide business decisions. This may involve a responsible conscience that prompts owners and managers to do "the right thing" [47]. For a summarized view of the topics and the related bibliography see Table 1.

Management behavior and motivations
The literature indicates that in recent years there has been a nascent trend among tourism intermediaries to be increasingly involved in the implementation of CSR measures, precisely due to the growing awareness and sensitivity of consumers towards ecological and social behavior. These tourism actors face extraordinary challenges when implementing CSR in their businesses as they not only have to evaluate CSR measures within their own company, but also throughout the value chain [13]. The development of CSR in this subsector of the tourism industry has particularly responded to issues related to the promotion of sustainable tourism practices, with very few initiatives for full integration of responsible policies in organizations. Although interest in responsible tourism is high and currently a recurring debated topic, it is not very widespread among intermediaries and coherence in CSR policies, programs and practices are still sought [59]. So much so that the factors that shape the adoption of sustainability practices by intermediaries show how sustainability strategies, practices and standards seem to be conceived primarily as a means of risk management (to prevent a negative public image), as a competitive advantage (brand equity and reputation), and as a strategy to manage regulation [52], rather than as a means to provide better customer services, cost savings, or business opportunities [60]. Research suggests that the incorporation of intermediary companies in a process of setting the CSR agenda is primarily a response to customer concerns, NGO activities, or due to negative publicity from their activities [57].
There seems to be an agreement that among intermediaries a relevant part of their conception of what is responsible is directly related to the need to source and sell more sustainable products. Yet, despite growing product offerings, supported by apparently strong business cases, sustainable tourism still accounts for only a remarkably small proportion of the total tourism supply [61], with a sense of lost opportunities and low involvement faced with a demand for distinctive and sustainable experiences without translation into additional sales [58]. In this sense, it is known that tourism companies that integrate sustainable practices tend to find it difficult to effectively communicate their commitment to sustainability and the derived benefits for the client [62,63]. Nevertheless, there is little evidence to support these companies in communicating their sustainable actions in a more persuasive way, although some studies have provided evidence in this direction [120,121].
Hence, travel intermediaries also must play the role of information intermediaries, or professional infomediaries [64], particularly when exclusive and specialized experiences are involved. Consequently, they can have significant power to shape the relationship between tourism products and services and tourists themselves, preferentially selling and targeting some of them in particular. Despite this, little research has been done on their role as potential responsible tourism actors, although there are studies that demonstrate a resistance of the subsector to understand and integrate the concept of sustainable tourism [65]. More specifically, little is known about their role in developing ethical considerations in sustainable tourism supply chains that ultimately shape the development of this sector [66], although the studies have outlined the relevant fields of action for the development of a correct CSR policy within these companies: the internal management, the product development, the supply chain, the customer relations and the cooperation with the destinations [9].

The firm´s size factor
When the literature related to sustainability has made reference to a subsector as relevant as this, it has focused especially on large international tour operators, ignoring generally travel agencies [74], which not only are basic in the sectoral structure of most international destinations, but are also leading the major transformations in the sector, both in disintermediation and reintermediation processes [19,122]. This uneven analysis can be extrapolated to each stakeholder separately, thus, tour operators have been mainly studied by large corporations while travel agencies have a priority focus on SMEs [57,71]. Early researchers highlighted the disparity of business approaches in this regard depending on small, medium and large companies [75]. In CSR performance, even though worse than in other tourism subsectors, large firms were more advanced than medium and small ones, while medium-sized companies, in turn, did better than small companies [72]. In contrast, previous and pioneering research already showed that small-scale specialized intermediaries were more interested in protecting the environment and tended to be more active, encouraging policymakers at destinations to develop viable long-term strategies [123].
Latest studies have delved into the different performance between SMEs and large companies when CSR is concerned. In fact, among large corporations, given how their priorities are established, the main practices towards CSR are internal policies that are oriented with codes of conduct and certification systems that serve as a marketing tool [57]. On the contrary, those who stand out for their CSR practices and policies are the smaller organizations [74,77,124], which emphasizes that having small operations can be a success factor for the development of sustainable tourism [125], implicitly excluding the possibility that large organizations can adopt it. While examples of responsible small-scale practices flourish, the lack of empirical evidence in mass tourism suggests that charitable actions, the adoption of codes of conduct and environmental measures are the applicable improvements for large-scale operations [126], expanding its conceptual dissociation from sustainable tourism. The limited adoption of sustainable product development procedures by large companies indicates the possible existence of deeper organizational barriers, causing that only a few large intermediaries have formal sustainable product development procedures, sometimes justified by its managers unfamiliarity with the concept of CSR or the erroneous idea that it is not a profitable product for them if not for smaller companies [60].
As Budeanu indicated [78], large companies, and their own retail subsidiaries, were the first to adopt a more proactive attitude and who have begun to develop responsible policies and plans in recent years. However, the viability of their structural adjustment has proven to be very low since most of these groups are not innovative enough in this field to consider it in all its breadth and to be able to face the presumed expenses and investments that it would entail [79]. The other two models of tourism intermediaries linked to large networks, franchisees and associates, have little place in tourism research, much less in specific topics such as CSR, with few exceptions in which these two models are analyzed as a brand of the large companies with which they are related, without taking into account their own characteristics and specificities [80].
As in the rest of the tourism sector, in the specific case of SME intermediary companies they do not usually have complex management structures and are generally managed by their owners, oriented towards solving the day-to-day business, establishing informal and close relationships with their interest groups and living in a reality dependent on the dynamics of the sector, determined on many occasions by the action of larger companies [81]. These largely independent small-scale companies position their value propositions [127] through their presence on the Internet to reinforce their differential factors, including sustainability, making ICT a basic element of tourism marketing [128]. The perception within these travel agencies in this matter is coincident and they think that their possibility of sustainable actions is limited within the sector as a whole. They adduce how the size of the company can be a determining factor, but warn that they can become decisive in this area, particularly with regard to its environmental aspect. Consequently, they have to improve their knowledge and information in this regard, at the same time that a more active role from agency/tour operators´ associations and the management groups to which they belong is indispensable.
Small and medium-sized tour operators can respond to their own challenges through CSR, although their proposals are often reduced to suit their own capabilities [73]. This happens because, typically, most are too focused on short-term goals to maximize profits, with a penchant for being tactical in their strategy, with their primary focus on customers who are their direct source of immediate information and short-term income, considering secondarily other objectives such as competitive advantage, branding, etc. Consequently, economic subsistence is the first and foremost goal among tourism intermediaries, regardless of size [129]. Along these lines, there is an academic discussion which sustains that the size of the tourism intermediary company does not seem to be related to the desire to develop responsible practices since the vast majority of the managers report receptivity towards more sustainable models. This development would seem to be related to price, where companies for which this is the most important factor would be less willing to bet on CSR, while those that attach greater importance to responsible practices, even taking into account price, show a higher interest and knowledge of CSR, which makes them more inclined to implement it [47].

Online intermediaries´ commitment
Given their prominent role in the present society, online intermediaries are increasingly expected to act according to current social and cultural values, which raises questions as to what kind of responsibilities should bear, and which ethical principles should guide their actions [130]. There is a large specialized literature that has studied the implications of online distribution in the tourism supply chain, mainly attending to cost, price and service level [131,132], to the effects in the traditional intermediaries [55,[133][134][135] and to the trust and quality achieved by the companies operating in this channel [136,137]. In contrast, few studies have analyzed the development of CSR in the online tourism intermediaries [17,80,83], but findings show that the acceptance of the new channel by consumers and the cost advantage it brings to these intermediaries, together with the profit sharing rate and the distributor's CSR behavior, jointly influence the choice of the sales channel and prices, showing that CSR behavior of online intermediaries could benefit the tourism supply chain and a greater acceptance of this channel among tourists [84].
The few researches that have been published on online intermediaries and their responsibility have followed the general trend of the sector of an environmental approach, prioritizing the websites of these intermediaries as relevant in attracting consumers to low-carbon trips. In other words, the web would not only provide travel information resources for tourists, but would also motivate them to participate in more responsible travel [85]. These authors indicate that environmentally responsible travel promotions can hardly be found, concluding that online wholesale and retail travel agencies have not been generically implementing actions related to CSR. In addition, these few researches have basically focused on the case of large tour operators [86], paying marginal attention to the case of retailers.
However, one of the most notable aspects in tourism intermediation regarding online marketing, and thus researchers have pointed it out, is the transition of the traditional companies to the online world, combining both sales channels. A clear example of resilience of this subsector. Most of them have been digitized by using e-marketing to reach customers instead of printing brochures, which come with a considerable amount of greenhouse gas emissions. In this sense, almost all the intermediaries use various online platforms to communicate with customers, ranging from Facebook, Twitter, YouTube, blogs, websites and other web-based applications, instead of traditional marketing methods, thereby increasing their market share [87].

CSR as an innovative strategy
There is unanimity among academics that innovations represent a key factor for competitiveness and development in all areas of activity, including the tourism industry and its intermediaries [21,22]. On the contrary, there is no such consensus regarding the contents and typology of innovations in the tourism intermediation sector since traditionally these have been associated with the need to identify and solve technical problems. Another important and controversial problem from the point of view of innovation research in the activity of intermediation agencies, is related to the link between innovation and the size of the company [89], aspect that would influence the sale of sustainable tourism products and its impact on the efficiency of the activity of intermediaries and their responsibility, according to the latter authors. Many researchers affirm that innovation is associated with an entrepreneurial spirit characteristic, mainly, of new companies, of small dimensions, which is why it is suggested that the innovative activities of SMEs are the most important determinant of their success [90]. On the other hand, large companies maintain the advantages that their size gives them to support the commercial development of new ideas by having the necessary financial resources to carry out experiments and prototypes or pilot operations.
Although CSR is not the panacea or the only measure to ensure the success of a business, even in crisis outlooks, the literature shows that many of the actions that are proposed to overcome the challenges derived from the innovative conception of CSR and are directly related to factors that are integrated into the responsibility of the companies [91]. Above all, they have a lot to do with investment and innovation strategies that allow the integration of analysis criteria based on the sustainability of companies, with strict accountability measures and on regulated business transparency frameworks, with the analysis of social and environmental impacts integration in the risk management, and, finally, with the adoption of responsible structures for corporate governance and independent and external supervision [92]. As a result, the access to knowledge and innovation increases their capacity for internationalization, reduces their costs, increases their competitiveness and encourages the creation of work and support networks [93].
Moreover, unlike a few decades ago, tourists demand innovation in services and products, a requirement that must be adequately answered by intermediaries, which requires sustainable innovation, both in the development of processes and in products, to achieve sustainability in business [94]. To meet this demand and promote sustainability, the exchange of information is considered necessary in order to reduce inefficiency and waste of resources [95]. However, sustainability is not just about innovation and technology adoption, but also about taking customer behavior into account when offering more sustainable products or services. Nevertheless, the studies coincide in highlighting that the adoption of responsible practices and innovations by the tourism intermediaries seems to go relatively unnoticed by their customers It is a fact that many tourism intermediaries operate with small profit margins and the resulting pressure from suppliers to lower prices may limit their ability to invest in quality improvements and innovation or other strategies that do not have a relatively immediate return [96]. But there is a vanguard of companies that understands the concept of CSR innovation as applicable to their business initiatives, creating de facto a specific market niche, which consider a social awareness work and offer services aimed at changing social practice of the trip [97], appealing to both individual and collective responsibility. For these, the responsible tourism middleman must be exemplary, with everything and everyone. Its responsible policies list evidences of its good behavior with the environment (use of recycled paper, free software, etc.), with its employees (reconciliation of work and family life, fair wages, etc.), with travelers, with the rest of the companies in the sector, and with the destination and its population. Its credibility is based on the manifestation of a close commitment to responsible tourism [98].

The sustainable tourism supply chain
The study of the sustainable supply chain in tourism has focused mainly on understanding the adoption of sustainability governance mechanisms [57,78,138] and on the resource efficiency and cost savings [10,103]. Other lines of research have also exposed the exercise of power and unequal control over providers by tour operators [139,140]. In this sense, some authors point out several fields in which a more detailed analysis of CSR in the tourism supply chain would be beneficial, such as the role of the different actors in the sustainable supply chain [58,101,141], or to obtain a clearer understanding of the specific sustainability requirements, opportunities and limitations at each point of the tourism supply chain [100,142]. However, a very important factor, and not sufficiently recognized in the tourism literature, is the complex set of corporate and contractual international agreements that characterize tourism intermediators, a factor that adds difficulties in achieving a sustainable supply chain since it is difficult to verify the commitment to CSR of each and every one of the companies with which it collaborates [57]. The problems and difficulties in persuading external contractors and small tourism providers to jointly commit to CSR are also emphasized. Given the large number of SMEs, as well as their importance for the socioeconomic viability of many destinations, studies that investigate how to overcome these troubles and support these SMEs in their commitment to sustainability are referred to be essential [10].
Similar conclusions are reached by other researchers who highlight how tourism intermediaries have limited potential to achieve sustainable management of the supply chain caused by a lack of understanding of sustainability by their managers, lack of values at the company level with respect to the sustainability, budget constraints, supply chain conflicts, lack of personnel trained in sustainability and lack of planning [100]. On the contrary, it seems undeniable that the relationship between the two traditional travel agency models, tour operators and travel agencies, is aimed at mutual collaboration and associationism, where the ideal would be a useful relationship in which both companies could create added value, share information and increase market opportunities [102]. These authors suggest that interpersonal behavior in their relationships, the offer of support, and the mutual search for customer satisfaction motivate managers to increase the quality of the relationship between travel wholesalers and retailers, where the duration of the relationship and importance of the product would affect this relational behavior.
Therefore, a supportive organizational culture is a prerequisite for the success of companies that want to increase the volume of sustainable products they source and sell. Sustainability is only sold when it contributes to an organization's ability to meet its service quality requirements, especially in relation to the suitability of products for its target markets and the strengthening of professional and trustworthy relationships. Business-to-business marketing requires suppliers to understand the relative importance of sustainability to each of their providers and, in response, develop appropriate arguments to explain the importance of sustainability within the organizational needs of their buyers [58]. In this sense, literature underscores the lessons to be learned from tourism supply chain research on how tour operators and local suppliers can collaborate effectively to foster sustainable tourism. Based on the literature review in this regard [52,100,[103][104][105][106][107][108], these lessons can be grouped into six areas: a) Collaborative vision that includes well-coordinated communication (including shared values), exchange and joint planning of information, "socialization" (for example, meetings, conferences, or visits to the destination) and establishment of cross-functional teams to maximize opportunities for information transfer and collaboration related to sustainability; b) training and advice, including awareness-raising interventions, targeted training, well-designed sustainability manuals and support for internal auditing, certification, monitoring and reporting; c) contractual and procurement incentives, including preferred partner status, fair purchase and contractual conditions; d) financial support including soft loans; e) rewards and incentives; f) and promotional opportunities.

Management behavior and motivations
In their role as intermediaries for tourism consumption, the perceptions, opinions, beliefs, attitudes, and work practices of these stakeholders make important contributions, negative and positive, to the sustainable development of tourism. Despite this, studies on tourism intermediaries and managers are fairly recent and limited in quantity and quality, especially in the non-Western world. In this subsector, the degree of behavior based on opinions and attitudes in daily business practices is barely known, since the structural environment of economic and political decisionmaking is marked by personal and organizational objectives, power relations and dominance. There are numerous variables, internal and external, that intervene in the form of an adequate and improved CSR performance when translating their responsible attitudes and principles into concrete operational changes [115].
In the same way that occurs in other sectors, the motivations and responsible behaviors tend to differ notably between large companies and SMEs intermediaries, and even the behavior of managers of small and medium-sized companies with regard to CSR is far from being homogeneous [71]. In large corporations there are usually coercive and regulatory pressures from the top down, so the managers of the delegations and sales offices have little room for maneuver to implement their own CSR initiatives, although there may be lines of business that are not passive recipients of these pressures and small responsible practices can be carried out outside the institutional guidelines [57].
In SMEs, on the other hand, the difficulties have been considered more than the advantages of introducing CSR, although the literature is modifying this vision. As a rule, the lack of resources [143] or information about market requirements, and the opportunities for change related to these practices [144] is recurrent in most discussions. Researchers also point out the existence of differences between large tourism companies and SMEs, sometimes key for the development of CSR policies, especially in economic, financial and information resources [145]. These academic contributions also tend to refer to the strengths of SMEs, such as the advantage of reacting more quickly and flexibly to certain aspects (including those related to CSR) and the closer relationship with their stakeholders [146]. In addition, in this business model, decision-making in this regard results in many cases an extension of the owner's personality [147] and in the case of entrepreneurs this can be decisive to stimulate a responsible culture and to ensure that it is related to values other than profit maximization as the sole criterion [124]. These considerations justify the fact that in the context of small and medium-sized intermediate firms a wide degree of divergence is observed in the introduction of responsibility practices depending on the different company profiles [74].
Finally, several of these studies have identified a series of managers' motivations that may lead them to adopt CSR, all of them in accordance with the motivations set out for the industry in general and the tourism sector in particular [14,71,109]. These typically include responding to stakeholder pressure, gaining a competitive advantage, adhering to government regulation, avoiding fines and other regulatory actions, and improving the image. Moreover, managers may also have internal ethical values to guide business decisions. This may involve a responsible conscience that prompts owners and managers to do "the right thing" [47].

The business case
A first type or category of intermediary is described with a markedly opportunistic profile and aimed at gaining market share with sustainability. These companies, normally large groups and also some medium-sized ones, have a high technological capacity, introduce sustainability as a market strategy and "image washing", so their mission, in relation to sustainability, responds more to the achievement of finalist objectives than to a certain vision of the world [74]. When addressing the motivations underlying their adoption of CSR, improving the company's image is considered the most important factor [52], followed by public relations, both motivations related to marketing programs. In fact, the construction of a positive public image is the most important motivator that drives large intermediary companies to adopt more responsible strategies, even more than responding to the demand of customers, which would rank secondly [9]. Therefore, a greater commitment to CSR for instrumental reasons can be expected from larger and more structured corporations than from SMEs [112].
The implementation of CSR programs for the managers of these firms is supported by an expected direct, positive and significant impact on the financial results of the company [148]. Any practice that improves the performance and business competitiveness of these businesses (image, customer satisfaction, employee satisfaction, etc.) has a positive impact on the company's results [149][150][151]. This relationship of CSR with results and competitiveness is relevant and motivating for these managers, proven proactivity in sectors especially affected by crises and in which there is a continuous movement, such as in tourism intermediation [152]. The presumed competitive advantage, tax advantages, fashion, mandatory compliance from the parent company, or external pressure (media, NGO, public, government, etc.) are, consequently, additional motivations highlighted by the existing literature [59].

The stakeholders´ rationale
The second profile is the tourism intermediary who tries to consider and reconcile the interests of the consumer and the variables that condition their purchasing decision processes, the supplier and its profitability strategies, and the destination territory with the local population and its sustainable development from an environmental, social and economic point of view [153]. This type of manager is open to sustainability as an element of improving its competitiveness through business differentiation in relation to competitors. It is a profile that can respond to any type of intermediary, but above all affects conventional medium-sized agencies which have a business structure that facilitates the introduction of sustainability practices as a competitive factor [74]. Studies in this area have understood that the commitment of tour operators and travel agencies to sustainability gives them a competitive advantage through added value [154]. Certainly, their proposals are based on a responsible policy, understanding that environmental, socio-cultural, economic and quality aspects must be covered in the definition of where they want to go, how and why [155], with the main purpose of achieving strategic competitiveness and success in the formulation and implementation of value creation from this strategy [156].
In this group of businesses concerned with justifying themselves to their stakeholders among the methods to increase their competitiveness, seeking the trust of the customers and the improvement of their image in the market, it is in those who more normative use of the implementation of quality requirements standards and the attainment of quality management system certifications are carried out [113]. Likewise, more and more travel intermediaries give a relevant role to suppliers and, in fact, it is more frequent that retailers require certificates or documents proving good practices. It seems to be related to recognizing exemplary corporate behaviors around this issue and being able to identify CSR policies related to those developed in the organization itself.

The lifestyle and personal values
Lastly, there is a third intermediary profile that fits with the conscientious small entrepreneur, with less symbolic sustainable initiatives and more convincing than those of large corporations [15]. They are highly specialized SMEs with a commitment that supports relationships beyond the competitive reinforcement of the company based on win-win acquaintances with destinations, society and the clients themselves [74]. In these businesses, managers´ altruist attitudes, further than the appreciation of the benefits for the company, motivate CSR practices, beside their decisions used to be shown and informed due to their understanding of subjective norms, their personal perceptions and their own abilities to be successful [14]. Despite this, the understanding of which role ethics plays in tourism has been largely neglected regarding the function of intermediaries within the tourism supply chain [116]. The results show that smaller intermediaries are more committed to sustainability, which demonstrates that many socio-economic initiatives and certain environmental practices do not necessarily require massive investments (those that only large companies can afford), but rather derive from a different business philosophy, where the personal sense of obligation, the values and the formal engagement of the manager are crucial to adopt CSR policies and measures [112].
The strong belief in values and in the possibility of a change is usually what has led to the creation of these companies, there is a high degree of commitment acquired by the intermediary and consistent with its own ethical principles. In fact, these entrepreneurs often reverse the sense of the purpose and the means: sustainability becomes the final objective, while the trip is reduced to the condition to achieve it (tourism is used as a tool to meet sustainable development). The intermediary minimizes the commercial component and puts their vocation, values and principles ahead [97]. Similar studies have been based on the assumption that relational networks play an important role in the value chain of the altruistic behavior of tourism brokerage managers, key to the development of the company and its partners. If the interaction between businesses is strengthened, factors such as emotion, trust, reliability and reputation become indispensable. In this way, the altruistic behavior of managers plays an important role in creating commercial value [109].
These innovative projects, apart from being of interest to the market, above all satisfy personally the entrepreneur. The motivation towards the incorporation of sustainability in these business models, represented by small and medium specialized intermediaries, is especially associated with a personal factor, motivation linked to a vital business project rather than to the search for new markets or economic results in the short term. However, the organizations that are committed to sustainability rely on the vital and innovative nature of their project to obtain benefits, to improve their competitiveness and to access new markets, in such a way that the business case also appears, albeit implicitly [74].

Conclusions
Despite the relevance of tour operators and travel agencies in the distribution of tourism products, their role within the supply chain has been scarcely studied, and even less with regard to their performance towards more sustainable practices. In this sense, the development of CSR in these companies seems to be the best way to achieve more responsible goals. After an exhaustive review of the literature, this work has collected the most recent lines of research on tourism intermediaries and CSR, among which could be noteworthy the evolution or emergence of current issues such as online intermediaries, the tourism sustainable supply chain or the underlying managers´ motivations in their commitment to sustainability. Likewise, throughout this review, various gaps have appeared, for the most part due to the barely existing literary production, which are likely to be studied in future research. In this sense, researches could delve into the approaches to CSR of very widespread intermediary business models in tourism such as the franchise and the company associated with a large corporation, the practices in sustainability of OTAs and other new online intermediaries, or the role that each actor in the tourism value chain must assume in order to achieve a more responsible tourism.
Most of the research highlights how tourism intermediaries have only just begun to develop CSR policies in their companies, and those that are committed to their implementation mostly opt for actions aimed at the environment, generally because they are the simplest and the most noticeable. However, it seems clear that, given its relevant position in the distribution channel, its commitment can be improved highly, beyond the creation and promotion of sustainable tourism products. That is why researchers have pointed out the relevance of the supply chain and the necessary collaboration between all its stakeholders, a very incipient measure in the subsector, where very competitive commercial policies are still being carried out, inherited from market structures that are already distant in time. In connection with this aspect, the studies highlight the innovative nature of CSR as a crucial factor in the survival of these intermediaries, not only in relation to possible internal control and process management measures but also in a clear commitment to the co-creation of value throughout the supply chain. Today more than ever, the use of new technologies and sustainable innovations seems to be the necessary bets for this intermediation sector to be able to overcome the crisis to which the Covid-19 pandemic has led it.
Furthermore, and as in other tourism subsectors, the view on CSR of the owners and managers of travel intermediary organizations is far from being homogeneous, detecting factors that explain the different views and behaviors. In the first place, it should be noted that corporate factors related to business management processes or the search for markets are also present when explaining the positioning of these companies in their approaches to CSR, but that they are other types of factors, such as altruism and lifestyle, which explain more accurately the differences in motivations and behaviors. In this case, altruism has not so much to do with the maturity of the companies in their approach to sustainability but with a personal factor applied to a specific intermediation business model. Altruism as an explanatory factor is related to a specific intermediary profile (SME and specialized) but also to the owner profile, and what is quite convincing, with the use of information technologies and social networks.