Sustainable Local Development : An Overview of the State of Knowledge

Since the eighties, the concern for sustainability has been increasing from several dimensions and depending on different socio-economic, political, geographical and cultural factors. In the last few years, local development has incorporated the concept of sustainability, as part of the United Nations’ Sustainable Development Goals strategy, highlighting the relevance of this process. The purpose of this research is to show the state of the art of this subject, for what a bibliometric analysis has been carried out based on the two most important online databases: Web of Science and Scopus. This article identifies the latest trends that characterize the concept of sustainable local development, where resilience is the new perspective to include in the variables that influence the development of territories. The results show a positive trend in this field of research, with both the number of articles published and citations increasing exponentially in the last ten years. In addition, the analysis of keywords has shown a tendency towards terms such as resilience, rural tourism or ecological agriculture. In essence, the concept has reached such a point that it is necessary to establish new mechanisms that soften and even negate the economic disruption caused by globalization.


Introduction
In recent years, local development has been integrated into the concept of sustainability, a term originally coined in the 1970s [1].An improvement in the standard of living and well-being of the current population to the detriment of the possibilities of future generations is a short-term development which, in short, cannot be considered local development as such.Sustainable Local Development (SLD) must have the capacity to feedback and maintain itself over time, respecting the constraints presented by the surrounding natural environment [2].Such is the importance of SLD nowadays that, in 2016, the United Nations Development Programme (UNDP) launched the Sustainable Development Goals strategy as a continuation of the Millennium Development Goals [3].Any field of study must consider the restrictions that guarantee the sustainability of the processes and, therefore, local development must include this variable when analysing the state of the territories and preparing initiatives.
Local development is understood as a process of improvement of the economic, social and environmental situation of a given area based on the use of endogenous resources in order to improve the well-being and quality of life of its population [4].The most characteristic element of the concept is found in endogenous resources [5,6], which take advantage of the economic and social dynamics of a specific territory, so that its past and future is intrinsically related to its use.Through research committed to the community, the agents involved in the process analyse the historical and socio-cultural context of a region, identifying the interrelations established between the knowledge, public and private sectors and the citizenry [7,8].In this way, the research is carried out in projects and activities, encouraging the local community to be more sustainable and resilient in a global context of constant change.
In order to identify the new trends that mark the processes of SLD, the literature on this holistic and integral concept is analysed.Previous studies [9] on sustainable development from a bibliometric point of view had omitted the local dimension in the concept of sustainable development.
The concept of SLD did not arise directly as such but rather as an aspect of local development in which the importance of the process of sustainability is portrayed [10].Local development, in turn, emerged as a response to the crisis experienced in the 1970s [11], marked by an increase in oil prices, the main engine of economic activity at a global level [12].
The present article is structured as follows.After an overview of the literature related to the concept of development and its different currents and interpretations, a brief explanation of the bibliometric methodology and the resources used in the research is given.Next, the main results are presented and the records of both databases are compared.The conclusion includes some final comments and proposals for new lines of work and research that can enrich the dimension of SLD by incorporating the concept of resilience as a tool that allows territories to soften the effects of high levels of globalized uncertainty.

Literature Review
At the end of the 1980s, the European Union introduced local development into the global economic context by using the term rural development [13] to resolve socio-economic differences between regions in Europe.In the communication The Future of the Rural Society [14], the European Union took a step towards the concept of local development with the delimitation of the concept of rural area.However, it was not until 1991 that the notion of local development was embodied in the first LEADER (Liaison Entre Actions de Développement de l'Économie Rurale) call [1,13], pioneering the use of a bottom-up approach to support local initiatives and collaborative projects [15].In fact, this notion is vital to build a theoretical framework for understanding the trajectories of rural communities based on the economic, social and environmental resilience and vulnerability of rural areas [16].
The main characteristic that differentiates local development from other growth models is the emphasis on the regional factor [17] and on the specific resources [18] contained within it.Faced with a vision in which growth initiatives originate from a central authority [19], local development promotes the drafting of locally based plans [20], which hinges on the experience of those who live the reality of the region and who best know its strengths and weaknesses.
However, if the improvement of a territory is not maintained over time, local development policies will have been in vain [21].For this reason, the academic community resorted to the concept of sustainability, which was first discussed at the United Nations Conference on Environment and Development held in Stockholm in 1972 [22][23][24].In the following decade, the International Union for Conservation of Nature championed the importance of this vision by integrating nature conservation and development factors by means of the World Conservation Strategy which it formulated with the United Nations Environment Programme and the World Wide Fund for Nature [25].
It was at the World Life Issues on Environment and Development Commission (also known as the Brundtland Commission), in 1987, that the concept of sustainability was incorporated into the question of how and why regions develop [26].The report sets out two key points.The first one was the urgency of addressing the needs of the weakest region and, the second one was the limitations imposed by technology and society [27][28][29][30] on the ability of the environment to meet present and future needs.
The first materialization of the union of these two strands in the term SLD is found in the pattern analysis in which the agricultural system is analysed by all disciplines involved [31].These guidelines are important for determining productivity, stability, sustainability and equity, leading to an agreed set of key questions for future research or, alternatively, a set of provisional guidelines for development.
From that year on, there have been different currents that link SLD to specific factors.Innovation, considered as a fundamental force, is applied in theoretical approaches and researches such as the theory of the innovative medium [32], the concept of "Smart Growth" [33] as well as theoretical line and develop a theoretical framework related to the relationship between innovation and endogenous development [34].In addition, some researches are oriented towards the construction of an integral socio-ecological framework to serve as a basis for the drafting [35], execution and control of rural development plans or a technological approach to the framework of territorial development based on innovation [36].However, innovation can be held back by administrative and political and legal barriers [37].Furthermore, the business sector is not the only source of innovation as the public sector and the knowledge sector also influence innovation processes through the management of public resources or the generation of knowledge [38][39][40].
Entrepreneurship is a form of innovation within the SLD field as studied by the authors in the field of social economy in rural areas [41][42][43][44][45][46].The concept of community-driven co-innovation could be successfully implemented to improve the situation of small farmers [47] but their innovative potential is limited by a systemic lack of access to finance, markets and knowledge networks [48].Green entrepreneurship, a process in which key actors facilitate SLD through a combination of fragmentation strategies, specialization and quality construction [49] has been proposed as solution.
Alongside the primary sector, tourism is one of the sectors in which endogenous resources are best combined in an innovative way.The agents involved in tourism must also have a proactive and positive attitude towards sustainability [50][51][52].They represent an innovative attempt to evaluate sustainability in a holistic manner, by defining specific objectives through the definition of appropriate indicators to measure and evaluate the temporal evolution of development policies, the integration of sustainability to reduce adverse effects on the environment and the promotion of the conservation of local and traditional values.This sector acquires special importance in those localities that suffer from a progressive depopulation [53] being indispensable the implementation of innovative actions that favour the attachment of tourist clients to the local territory [54] and that restructure and strengthen the social capital to improve the competitiveness of tourism and promote the socio-economic development of the region [55].
Another group of authors integrate SLD into the gender issue.For them, development that does not permeate the whole of society is not development.SLD initiatives improve the empowerment of women, making them owners of their work and participants in the evolution of society [56,57].
Participation of the citizenry is another factor to which SLD is usually linked, especially evident when dealing with bottom-up projects.Framed in this context is the concept of e-government [58], characterized by the use of Information and Communication Technologies (ICTs) in the functioning of public institutions.The report Latin America Puntogob: cases and trends in e-government [59] carries out an in-depth study of this phenomenon, as well as a description of experiences in Latin American countries.Among the many proposals, the e-Mexico program whose central idea consisted in the establishment of a connectivity network based on Digital Community Centres stands out.The presence of Internet facilities in rural areas, which offer government services to citizens, is positively associated with the rate at which inhabitants obtain some of these services [60].Along the same lines, some research results suggest that sustainability initiatives could best be implemented through a collaborative approach at the local community level involving local citizens working in partnership with local government [61][62][63].
Finally, other studies combine the elements of innovation and citizen participation to enrich the dimension of SLD [64][65][66].Not only is innovation linked to citizen participation but also to the empowerment of women.For example, some research study the impact of microfinance services on women's entrepreneurship or introduces cooperativism as a field of study, evaluating whether this form of association is a development tool that could tackle the current problems of rural regions: depopulation, low participation of women in the level of employment and a more promising future [67][68][69].

Methodology
Bibliometric analysis is a research method based on the citation network, from which the sub-methods of citation analysis and scientific cartography, essential for the evaluation of research performance, are derived [70,71].This bibliometric study is based on a systematic bibliographical analysis of the literature related to the central study theme, following a sequence of steps [72] shown in Figure 1.The methodology has been already used to study the literature about economic growth, development and sustainability [73][74][75][76][77], providing researchers with essential information about the state of this area of knowledge.Without the application of any filter on the databases, 1103 documents were retrieved from the WoS and 1488 files were saved from the Scopus database.After the temporary and documentary filter indicated above, the sample was reduced to 774 results in the case of WoS and to 1054 results in the case of Scopus.

Discussion and Results
The results obtained from the introduction of the selected keywords in the WoS and Scopus databases are presented below.They have been analysed from different perspectives: subject matter, language of publication and countries of origin of the articles, most influential authors, most prominent journals and evolution of the number of articles published and citations.

General Overview
Below is a series of data that reveals the status of the research activity about SLD with reference Different bibliometric indicators were also used in this research to analyse the scientific output: the impact of papers, indicated by the number of references received from other subsequent publications (number of citations); frequency: Hirsch index (h-index and averages) [78] and the indexes of publications in WoS Core Collection and Scopus online databases are considered.
Regarding the definition of the search criteria, keywords and period, "local development" and "sustainability" and, on the other hand, "rural development" and "sustainability" have been searched on the databases.The emergence and use of the two terms as synonyms by agencies such as the World Bank or the United Nations Department of Economic and Social Affairs (UNDESA) [79] has led to use a double root of the concept into local and rural.
The choice to study only articles published in research journal is due guarantee the academic quality of the publications and the homogenization of results.Indexed journals ensure academic quality, which is backed by blind peer review.Although there are books and proceedings of very high academic value, the inclusion of this type of publication (not included in impact indices) do not allowed a proper process of data for this research.On the other hand, the indexes and rankings of quality such as Journal Citation Report (JCR) or SCImago Journal Rank (SJR) only refer to scientific journals.
The study period coincides with the registration of articles in each of the databases.For WoS this starts in 1991 and ends in the first half of 2018.For Scopus, the period runs from 1984 to the first half of 2018.
Without the application of any filter on the databases, 1103 documents were retrieved from the WoS and 1488 files were saved from the Scopus database.After the temporary and documentary filter indicated above, the sample was reduced to 774 results in the case of WoS and to 1054 results in the case of Scopus.

Discussion and Results
The results obtained from the introduction of the selected keywords in the WoS and Scopus databases are presented below.They have been analysed from different perspectives: subject matter, language of publication and countries of origin of the articles, most influential authors, most prominent journals and evolution of the number of articles published and citations.

General Overview
Below is a series of data that reveals the status of the research activity about SLD with reference to the results of the WoS and Scopus databases.
The first fact to be highlighted is found in the sample analysed: 774 articles extracted after the application of the filter from WoS versus 1054 documents from Scopus.The difference between the two figures is due to the time period in which the first relevant records on SLD appeared in the databases.In the case of Scopus these dates are from 1984 to 2017, while on WoS, the first record appeared in 1991.
The trend in the number of articles published in WoS in this regard is positive, growing slightly since 2000, falling in 2012 and picking up again until 2017.Thus, it is observed that this field of research is thriving and the trend is expected to continue in the following decade (Figure 2).The trend in the number of articles published in WoS in this regard is positive, growing slightly since 2000, falling in 2012 and picking up again until 2017.Thus, it is observed that this field of research is thriving and the trend is expected to continue in the following decade (Figure 2).
Since 1991, when the first SLD article was registered in WoS, the trend of citations of this concept follows the dynamics of peaks and valleys, reaching its highest point in 2010, a time that coincided with a period of economic crisis.In fact, it was in 2007 when the citation of articles related to the SLD began to increase.There is a relationship between the world economic crisis of 2007/2008 and the number of citations of this type of work (Figure 3).
Furthermore, the evolution in the number of articles in Scopus follows a similar trajectory to that of WoS, with a boosted take-off from 2002 and a similar behaviour in the evolution in the number of citations.The first article registered in this database is the 1984 document entitled From research to implementation: the country boats of Bangladesh and strategies for development assistance to an indigenous transport sector (Norwegian aid) by Alf Morten Jerve and Erik Jansen [79].
If we compare the evolution in the number of articles and citations in each database, it can be seen that throughout the period in question, the Scopus database contained a greater number of entries than the WoS database until the year 2015, when the trend was reversed.
In both WoS and Scopus, the variables that refer to countries and journals increase over time.The evolution of the number of references has greater significance, indicating that as we enter the twenty-first century there has been an increase in the theoretical basis of the scientific articles on SLD.Consequently, there has been an increase in their theoretical quality, although this is also explained by the increase in the quality standards demanded by journals.Likewise, both databases present a similar trend in the number of references per article, homogenizing at the end of the study period (Table 1).Since 1991, when the first SLD article was registered in WoS, the trend of citations of this concept follows the dynamics of peaks and valleys, reaching its highest point in 2010, a time that coincided with a period of economic crisis.In fact, it was in 2007 when the citation of articles related to the SLD began to increase.There is a relationship between the world economic crisis of 2007/2008 and the number of citations of this type of work (Figure 3).

Distribution by Research Area
The research areas in both databases are not coincident, so it is necessary to study them separately.The main research areas of the SLD term are Social Science in Scopus and Environmental Sciences Ecology in WoS database (Table 2).
From the point of view of the WoS database, Economy is relegated to fourth place, with less than half of the articles compared to the aforementioned research areas, followed by Agriculture and Geography.As can be seen, in light of this data, there is a tendency towards the environmental aspect of SLD studies to the detriment of the political trend, represented by the knowledge area of public administration.
With regards to the Scopus database, it can be seen that the Social Sciences, along with the Environmental Sciences, monopolize the field of local development.Economics obtained the same ranking as in WoS, while the link between SLD and business is relegated to sixth place.In addition, Biology, Medicine, Computer Engineering or Chemistry are at the bottom of said ranking.
In conclusion, it could be said that SLD is closely linked to environmental sciences, agriculture and, to a lesser extent, to the economy, which, if the Scopus perspective is applied, has a high social element.
Overall, the prevalence of agricultural and environmental issues is evidenced in a trend towards promoting primary sector activities with a strong sustainability component, such as ecological agriculture or the use of renewable energy sources within a purely family or small business environment.The economic aspect, on the other hand, is found in articles that focus on activities such as rural tourism to indicate new lines of research.Finally, the social sciences group all these thematic lines within the framework of resilience.SLD calls for multidisciplinary collaborative work between the different branches of knowledge to improve the capacity of territories to adapt to changes in the global economic situation.Furthermore, the evolution in the number of articles in Scopus follows a similar trajectory to that of WoS, with a boosted take-off from 2002 and a similar behaviour in the evolution in the number of citations.The first article registered in this database is the 1984 document entitled From research to implementation: the country boats of Bangladesh and strategies for development assistance to an indigenous transport sector (Norwegian aid) by Alf Morten Jerve and Erik Jansen [79].
If we compare the evolution in the number of articles and citations in each database, it can be seen that throughout the period in question, the Scopus database contained a greater number of entries than the WoS database until the year 2015, when the trend was reversed.
In both WoS and Scopus, the variables that refer to countries and journals increase over time.The evolution of the number of references has greater significance, indicating that as we enter the twenty-first century there has been an increase in the theoretical basis of the scientific articles on SLD.Consequently, there has been an increase in their theoretical quality, although this is also explained by the increase in the quality standards demanded by journals.Likewise, both databases present a similar trend in the number of references per article, homogenizing at the end of the study period (Table 1).

Distribution by Research Area
The research areas in both databases are not coincident, so it is necessary to study them separately.The main research areas of the SLD term are Social Science in Scopus and Environmental Sciences Ecology in WoS database (Table 2).From the point of view of the WoS database, Economy is relegated to fourth place, with less than half of the articles compared to the aforementioned research areas, followed by Agriculture and Geography.As can be seen, in light of this data, there is a tendency towards the environmental aspect of SLD studies to the detriment of the political trend, represented by the knowledge area of public administration.
With regards to the Scopus database, it can be seen that the Social Sciences, along with the Environmental Sciences, monopolize the field of local development.Economics obtained the same ranking as in WoS, while the link between SLD and business is relegated to sixth place.In addition, Biology, Medicine, Computer Engineering or Chemistry are at the bottom of said ranking.
In conclusion, it could be said that SLD is closely linked to environmental sciences, agriculture and, to a lesser extent, to the economy, which, if the Scopus perspective is applied, has a high social element.
Overall, the prevalence of agricultural and environmental issues is evidenced in a trend towards promoting primary sector activities with a strong sustainability component, such as ecological agriculture or the use of renewable energy sources within a purely family or small business environment.The economic aspect, on the other hand, is found in articles that focus on activities such as rural tourism to indicate new lines of research.Finally, the social sciences group all these thematic lines within the framework of resilience.SLD calls for multidisciplinary collaborative work between the different branches of knowledge to improve the capacity of territories to adapt to changes in the global economic situation.

Most Influential Institutions
The main research centre working in the field of SLD is Wageningen University & Research in the Netherlands, with 31 articles registered in WoS and Scopus.It is followed, in the WoS database, by the Universities of Cardiff, Newcastle, London (United Kingdom), California (United States) and the National Institute of Agronomic Research (France) with around ten records each.From this it can be deduced that the English-speaking universities monopolize this field of research from the point of view of WoS.The Wageningen Environmental Research Centre is the institution with the highest number of citations per article, followed by Cardiff University (Table 3).The first of these is a research centre with three fundamental areas of focus: food production, healthy lifestyles and the environment.The second, on the other hand, is one of the most prestigious universities in the United Kingdom, reaching 5th place amongst UK universities in the 2014 Research Excellence Framework for quality and 2nd for impact.In contrast, Scopus shows a preponderance for Chinese institutions, which rank second and third in terms of article production.Both deal with issues related to environmental sciences and geographical and territorial resources, in a similar way to Wageningen University & Research.This database also includes two South American institutions: The University of São Paulo (Brazil) and the University of Zulia (Venezuela).The institution with the highest number of citations per article is the University of Colorado, an extremely important fact if one considers that it is the institution with the lowest number of articles published on SLD.
The reason for this is found in the geographical concentration of WoS institutions versus those included in Scopus.While the former includes European institutions (with the exception of the University of California, USA), Scopus also covers South America and Asia.In addition, its research focus also includes the only Spanish-speaking institution, the University of Zulia (Venezuela).These results are therefore consistent with those obtained in the distribution by country analysis, with institutions in the United Kingdom, the Netherlands, the United States and China being particularly noteworthy.On the other hand, the cluster analysis shows that Wageningen University & Research is the main centre of SLD studies, while the universities of Perugia (Italy) and Florida (United States) have been spearheading the latest trends since 2016 (Figure 4).In addition, the prevalence of Dutch and Chinese institutions is perfectly in line with the high level of participation in the agriculture and environment themes presented in the corresponding sections.

Most Influential Journals
The journal with the largest number of articles published in the SLD field is, for both WoS and Scopus, Sustainability, with 25 and 33 retrieved documents respectively.This is followed by the Journal of Rural Studies and Land Use Policy, with 20 articles in each of the databases.Alongside these, the most influential journals or in other words, with the largest number of citations and H indexes, are the Journal of Rural Studies, Agricultural Systems, Sociologia Ruralis and the Boletín de

Most Influential Journals
The journal with the largest number of articles published in the SLD field is, for both WoS and Scopus, Sustainability, with 25 and 33 retrieved documents respectively.This is followed by the Journal of Rural Studies and Land Use Policy, with 20 articles in each of the databases.Alongside these, the most influential journals or in other words, with the largest number of citations and H indexes, are the Journal of Rural Studies, Agricultural Systems, Sociologia Ruralis and the Boletín de la Asociación de Geografos Españoles.This is perfectly in line with what is specified when dealing with the subject, highlighting the relationship between the concept of SLD, the environment and agriculture (Table 4).
In both bibliographic platforms, the Agricultural Systems journal stands out as the one with the highest number of citations per article, while the Journal of Rural Studies has the highest H index in WoS and Scopus has the same number as Sociologia Ruralis.The latter, in turn, is the oldest, starting its research activity in 1960.Despite Sustainability being one of the newest publications, it contains the highest number of SLD articles under its scope of publication.
Of all the publications grouped in the following tables, both databases differ only in three journals.In the case of WoS, these journals are the International Journal of Agricultural Sustainability, the Journal of Cleaner Production and New Medit.While on Scopus they are Wit Transactions on Ecology and the Environment, the International Journal of Sustainable Development and World Ecology and Quality Access to Success.
The country of origin of each journal also supports the results obtained from the distribution of the concept by country, with a high presence of the United Kingdom and, to a lesser extent, the Netherlands.

Most Relevant Authors and Cited References
Table 5 shows the authors with the highest number of articles published on the subject of SLD.According to the WoS database, the data shows that, among the most published authors, the maximum number of articles published per author is four.Among them, Bebbington is the author with the most influence, far surpassing the rest of authors with the same number of published articles.This is due to the fact that one of the works published by this author is the most cited article in this area of knowledge.On the other hand, it is worth mentioning the case of authors Giovanni Quaranta and Rosanna Salvia, who are co-authors of the same articles (i.e., [55]).If we take into account this consideration, we can reduce the list of authors with the highest number of published articles to nine.
The distribution of articles according to authors is similar in WoS and Scopus.However, the maximum number of published papers per author on Scopus is five, which is higher than the figure shown for WoS.This is due to the fact that Scopus, in this subject, has a wider collection than WoS.It is worth noting the case of the author Anthony Bebbington who on WoS is the most influential author with four articles.Meanwhile, on Scopus he has twice as many registered articles.His most cited article in both databases is Capitals and capabilities: A framework for analysing peasant viability, rural livelihoods and poverty [69], cited 711 times.In it, the author analyses rural livelihoods according to their sustainability by building an analytical framework, drawing their implications for rural poverty.It is followed by the article by Edward H. Allison and Frank Ellis, The livelihoods approach and management of small-scale fisheries [80], cited 433 times, wherein they apply a sustainable livelihoods approach to analyse the strategies of local fishermen in the face of limited fishery resources.
The distribution of authors by country is also a reflection of the results obtained in terms of the distribution of SLD studies by country, highlighting the United Kingdom and Italy as the places of origin of the most influential authors in this area.

Most Influential Countries
Table 6 represents the main countries in terms of SLD publications in both databases.From a WoS perspective, the United Kingdom leads the list along with Italy, the United States and Spain.Both the United Kingdom and the United States have the highest number of citations and the highest H-index followed by the Netherlands.It is observed, therefore, that English-speaking countries have the greatest influence compared to Spanish-speaking countries such as Spain or Mexico which, despite being one of the countries with the highest number of published articles, has fewer citations and a much lower h-index.In terms of distribution by country, on Scopus, Italy leads the list of countries that publish SLD articles with 41 articles.It is followed by Spain, the United Kingdom and the United States with around 30 documents.This is a similar scenario to the one presented in WoS, with Greece being the main differentiator between the two.The Netherlands, in turn, has the highest number of citations per article, while the United Kingdom continues to monopolise the H index.In fact, the predominant language in the SLD articles is English with almost 90% of all works published in both the WoS and Scopus registers.It is followed by Spanish and Portuguese with 8% and 1% respectively.This is also reflected in the analysis of the countries that publish the greatest number of articles.In addition, the cluster analysis shows the time line of SLD studies, initiated by the United States and the Netherlands, later incorporating the United Kingdom as the driving country of the concept and finally followed by Spain and Italy, the latter being the country that marks the trend of the future (Figure 5).

New Trends
A fractional counting is conducted to identify which terms are most commonly used and which trends are currently shaping new aspects of SLD studies.For this purpose, the study is based on trend graphs produced by VOSviewer (version 1.6.10,Leiden University, Leiden, The Netherlands), where a gradual scale of colours indicates the novelty of the term: purple pertains to concepts from the beginning of 2010 and yellow corresponds to the final study period.In both databases the terms sustainability and rural development are the most prevalent in SLD articles (Figures 6 and 7).
The terms tourism, territory, resilience and family farming mark the latest trends for understanding SLD.It is followed, chronologically speaking, by terms such as bioenergy, biofuel or alternative food networks.It can also be seen that the new SLD trends are focused on specific locations: Spain, Italy, China, India and Brazil.With the exception of India this is consistent with the distribution by country shown above.
A closer look at keyword clusters reveals a link between the terms that accompany SLD and geographical location.On the one hand, Africa, China and Asia are related to biofuel use, food security, land management, poverty and climate change.On the other hand, Mexico and Spain are related to issues of sustainable rural tourism, forest management and cultural heritage.Finally, Italy and Australia are in two different clusters, the first being linked to concepts such as agroecology and ecotourism and the second to community action and sustainable social development.In light of this data, it can be deduced that there is a double aspect of SLD depending on the countries to which it refers: climate change and poverty for Africa and Asia, while tourism and sustainable rural development for Europe, Central America and Oceania.
This new resilience trend is thus linked to the concepts of corporate social responsibility, governance, livelihoods and vulnerability.Thus, the authors who have introduced this term include it as one more variable to be taken into account by authorities and companies when carrying out their activities to reduce the vulnerability of territories and thus improve the livelihoods of families.
As a whole, the concept of SLD is currently linked to the primary sector in the rural family

New Trends
A fractional counting is conducted to identify which terms are most commonly used and which trends are currently shaping new aspects of SLD studies.For this purpose, the study is based on trend graphs produced by VOSviewer (version 1.6.10,Leiden University, Leiden, The Netherlands), where a gradual scale of colours indicates the novelty of the term: purple pertains to concepts from the beginning of 2010 and yellow corresponds to the final study period.In both databases the terms sustainability and rural development are the most prevalent in SLD articles (Figures 6 and 7).
The terms tourism, territory, resilience and family farming mark the latest trends for understanding SLD.It is followed, chronologically speaking, by terms such as bioenergy, biofuel or alternative food networks.It can also be seen that the new SLD trends are focused on specific locations: Spain, Italy, China, India and Brazil.With the exception of India this is consistent with the distribution by country shown above.
A closer look at keyword clusters reveals a link between the terms that accompany SLD and geographical location.On the one hand, Africa, China and Asia are related to biofuel use, food security, land management, poverty and climate change.On the other hand, Mexico and Spain are related to issues of sustainable rural tourism, forest management and cultural heritage.Finally, Italy and Australia are in two different clusters, the first being linked to concepts such as agroecology and ecotourism and the second to community action and sustainable social development.In light of this data, it can be deduced that there is a double aspect of SLD depending on the countries to which it refers: climate change and poverty for Africa and Asia, while tourism and sustainable rural development for Europe, Central America and Oceania.
into a whole set of mechanisms aimed at improving the position of territories against sudden and negative changes in the international economic scenario.into a whole set of mechanisms aimed at improving the position of territories against sudden and negative changes in the international economic scenario.This new resilience trend is thus linked to the concepts of corporate social responsibility, governance, livelihoods and vulnerability.Thus, the authors who have introduced this term include it as one more variable to be taken into account by authorities and companies when carrying out their activities to reduce the vulnerability of territories and thus improve the livelihoods of families.
As a whole, the concept of SLD is currently linked to the primary sector in the rural family business environment where the resilience of the territory is the objective by using elements such as bioenergy, biofuel and organic farming.It is therefore observed that SLD studies are now integrated into a whole set of mechanisms aimed at improving the position of territories against sudden and negative changes in the international economic scenario.

Conclusions
This paper has reviewed more than 30 years of international research on the concept of SLD through a bibliometric analysis based on the two most important online databases: WoS and Scopus and, the last having a broader database than the first.
The results show that the evolution in both the number of SLD articles published and citations is positive, increasing exponentially over the last ten years.However, the comparative evolution of both databases shows that, despite having a large collection of SLD articles, WoS outperforms Scopus in both variables from 2012/2013, with a progressive replacement of the former by the latter.
The main thematic categories linked to the concept of SLD correspond to environmental sciences, agriculture and social sciences such as economics.However, the diversity of topics with which this concept is linked is so great that it demonstrates its multidisciplinary nature, which manifest itself in a holistic vision of knowledge in favour of the sustainable evolution of society.Therefore, the ultimate goal of achieving territorial resilience must be achieved with a holistic view of the capacities and resources of the territories, which requires a cooperative effort: collaborative work between the branches of knowledge to improve the competitiveness of the territory and, therefore, its resilience in the face of external disturbances.Something similar occurs with the institutional analysis of the issue, highlighting institutions in the United Kingdom, the Netherlands, the United States and China, while the universities of Perugia and Florida being the ones that are setting the latest trends from 2016 onwards.
The distribution by country shows a hegemony of the United Kingdom followed by Italy and the United States.The prevalence of the English language is evident not only by the fact that it is the most widely used language (88% in WoS and Scopus) but its influence is much greater than that of other languages in terms of number of citations and H indexes.
The cluster analysis of the distribution by countries shows that, from 2016 onwards, the future path of SLD is led by Italy, Germany, Finland and Romania, where a geographical decentralisation of the concept can be observed, expanding to other European countries.This fact enriches the composition of the concept by involving more territories and, therefore, including new theoretical-practical contributions that mark the future.In addition, most journals have their centre of operations in the United Kingdom despite the fact that Sustainability, a Swiss journal, is the most recent and the one with the highest number of SLD articles.This makes it the principle means of fostering new lines of research which have emerged in the last few months and which revolve around the theme of resilience.
Almost half of the most representative authors are from Italy, which is in line with the results of the distribution by country.In fact, Italy is the leading country in terms of developing new lines of research in SLD studies.
The analysis of keywords shows that the concept of SLD is currently linked to the primary sector in the rural family business environment where the resilience of the territory is the objective using elements such as bioenergy, biofuel and organic farming.There is also a double aspect of SLD depending on the countries to which it refers: climate change and poverty for Africa and Asia and tourism and sustainable rural development for Europe, Central America and Oceania.
The inclusion of the term resilience in the scope of SLD studies is an example of the adaptability of the term.It is linked to other terms such as corporate social responsibility, governance, livelihood and vulnerability.
Authors consider that governments must be the ones in charge of guaranteeing a decrease in the vulnerability of territories by creating new sources of employment so that families have sufficient means to have a decent quality of life.It is no longer sufficient to merely improve the quality of life in the relevant territories but rather, it is also necessary to enable mechanisms that soften or even annul the disruptions caused by globalization.This is the most important trend that marks the future of SLD studies and that defines a triple objective: social justice, environmental justice and resilience.To this end, local development strategies should be oriented towards an environment of citizen participation that generates close links between the community and the institutions of knowledge, all under a Citizen Science approach.
In short, the consolidation of a globalized and constantly changing world in which uncertainty is growing, makes SLD studies a mechanism to be used for the survival and resilience for the most vulnerable territorial units, which have to compete with the rest of the world starting from limited resources.This work is a compilation of what has been studied to date on this issue and even contemplates the new perspectives that have marked the research work of recent months.Thus, the agents involved in the SLD processes can benefit from the most up to date revision on which to base the planning, management and control of projects aimed at the quality of life of the most vulnerable territories in the face of the disruptions of a world in constant change and evolution.
According to the results obtained, the future of SLD studies revolves around the concept of resilience, in which Italy, with the University of Perugia at the forefront, is positioned as the driving country of this trend and journals such as Sustainability are the main drivers to influence the research effort of the scientific community of institutions with a great research capacity in the field of agriculture and the environment.Rural tourism and ecological agriculture could be also interesting issues to be considered for future research.
About the limitations of this research, firstly, the field of study has focused on the most influential academic databases (WoS and Scopus).It could be interesting to include also different data sets in future research, such as Google Scholar.Secondly, only articles have been analysed.Therefore, it would be also interesting to open a broader line of research that includes other types of publications, such as books or conference proceedings.

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Figure 2 .
Figure 2. Evolution in the number of articles.

Figure 2 .
Figure 2. Evolution in the number of articles.

Table 2 .
Distribution of articles by research area.
W/S: WoS/Scopus; A: Number of articles; JCR: Journal Citation Report; SJR: SCImago Journal Rank; TC: Total cites; TC/A: Total cites per article; H: H Index.
W/S: WoS/Scopus; A: Number of articles; TC: Total cites; TC/A: Total cites per article; H: H Index; 1st: year first article.Last: year last article.