Peripheral, Marginal, or Non-Core Areas? Setting the Context to Deal with Territorial Inequalities through a Systematic Literature Review

Abstract

Territorial inequalities are an issue of increasing relevance in the international scientific debate across different disciplinary fields, and their mitigation is a key challenge on the political agenda in many countries at the European and international level. An ongoing research project developed by the authors is investigating the phenomenon and possible strategies for rebalancing territorial development. In this framework, the present study provides an extensive review of the literature on the topic with the purpose of grasping the multiplicity of terms referring to areas affected by conditions of territorial inequalities. This paper describes the methodology adopted for developing a stand-alone Systematic Literature Review (SLR) protocol able to navigate both quantitative and qualitative insights on this complex topic. The SLR includes 347 records assessed for quantitative eligibility, 50 of which were included in the qualitative phase and studied through four categories of analysis (terms and phenomena, causes, models, and drivers) corresponding to the research questions. By tracing the evolution of the debate and the increasing scientific interest in the topic over time, the findings highlight the cross-disciplinary nature of the territorial inequalities that can be examined as complex and dynamic results of many spatial and aspatial issues at different territorial scales of investigation. Development models are benefiting from the evolution of the proximity concept from spatial to aspatial features—organizational, cognitive, and technological ones—changing the dependency between geography and innovation, especially with reference to entrepreneurship.

1. Introduction

In many countries, unpredictable global dynamics and short-sighted sectoral policies have affected places and communities, producing territorial inequalities due to the increasing polarization around central areas on the one hand and the spread of shrinking and marginalization processes in urban peripheries, small cities, sprawled settlements, and rural areas on the other [1,2,3,4,5,6,7]. These polarized development models resulted in decline, abandonment, aging, and depopulation of areas “left behind”, lacking technological innovation, economic catalysts, and, in general, the critical mass for attracting and keeping populations. The complexity and overlap of these phenomena determine the risk of progressive territorial degeneration processes [8]. The issues of inequalities between centers and peripheries are addressed through relationships of dependency, conditions of exclusion, and economic, social, spatial, and political implications closely interconnected, as highlighted by the scientific debate regarding several disciplines [4,9,10,11].

This relationship of dependency, based on inequality in terms of economic, political, and social power, was originally interpreted as a core-periphery model by Friedman [12] in his seminal contribution. Friedman’s definition identifies the core area as the most urbanized, with a high concentration of people and economic activities, while the periphery is characterized by an uneven population and lagging economic development. In this perspective, metropolitan cities are places of innovation, competition, infrastructure, and services, with decision-making functions, whereas declining areas suffer depopulation, reduction of essential services, lack of jobs and opportunities, as well as abandonment of built heritage, with negative impacts on the well-being and quality of life of the local communities. With regard to conditions of disadvantage, there has been a shift in theoretical approaches, including socio-economic performances and political dynamics as parameters for interpreting the marginalization phenomena instead of the mere localization and spatial dimension, i.e., the distance from and accessibility to the main services and opportunities [13]. According to these approaches, places not geographically remote could be intended as peripheral because of a lack of connectedness and weakness in interactions [7,14,15] and a lack of influence in the governance arena [2], highlighting the complexity of variables to be considered. Therefore, the issue of peripherality acquires a dynamic dimension linked to socio-economic factors that can make the process changeable and transitory [14,16].

In European policies, reducing territorial inequalities and promoting a more balanced development are themes approached under the umbrella concept of cohesion. This latter is first defined in the “Single European Act” (1987) through the economic and social dimensions, then in the “Lisbon Treaty” (2007), including the territorial dimension, as well as in the “Green Paper on Territorial Cohesion. Turning territorial diversity into strength” (2008), which emphasizes the need to increase cooperation and partnerships across regional and national borders by addressing questions of governance. Furthermore, “The Treaty on the Functioning of the European Union” (2012) underlines that “the Union shall develop and pursue its actions leading to the strengthening of its economic, social, and territorial cohesion. In particular, the Union shall aim at reducing disparities between the levels of development of the various regions and the backwardness of the least favored regions” (Title XVIII: Economic, social, and territorial cohesion—Article 174).

Since the 1980s, the growing inter- and intra-regional inequalities and the widening of territorial gaps have led to the implementation of cohesion policies for achieving more equitable and balanced development [17]. The reform of the EU Structural Funds in 1989 [18] confirmed the need for cohesion policies targeting the complexity of territorial imbalances among European regions. In the last programming period (2021–2027), almost a third of the total EU budget has been set aside for the Cohesion Policy to reach goals, such as job creation, business competitiveness, economic growth, sustainable development, and improving citizens’ quality of life, targeting differences among regions. Reducing the gross domestic product (GDP) gap is one of the cornerstones of the Cohesion Policy. Indeed, the European Union defines peripheral regions as those with a GDP per capita of less than 75 percent of the EU average.

The communitarian political agenda addresses the issue of rebalancing territorial inequalities through specific programs based on building partnerships among regional and local authorities, social actors, and organizations from civil society [19,20]. The European Spatial Planning Observatory Network (ESPON) was launched in 2013 within the framework of the European Cohesion Policy in order to “Support policy development in relation to the aim of territorial cohesion and a harmonious development of the European territory by (1) providing comparable information, evidence, analyses, and scenarios on territorial dynamics and (2) revealing territorial capital and potentials for development of regions and larger territories, contributing to European competitiveness, territorial cooperation, and a sustainable and balanced development” [21]. Regarding peripheralization processes, applied research programs, such as GEOSPECS (Geographic Specificities and Development Potentials in Europe) and PROFECY (Inner Peripheries: National Territories Facing Challenges of Access to Basic Services of General Interest), have been launched. In the latter, a specific reference is made to the Italian Policy to address the issue of the inner areas “subject to strong centrifugal forces—demographic decline, migration, abandonment of use and management of land, natural hazards, isolation, low accessibility to services and infrastructure, economic marginalization”, considering that these conditions “render the inner areas less able to sustain place-based development processes capitalizing on local territorial capital in order to enhance their competitiveness” [15]. These programs, based on cooperation among countries, allow us to map inequalities in different contexts by investigating recurrent conditions as well as specific territorial features and assets for enabling territorial policy and regional development. In the last decades, the scientific debate has also increasingly highlighted differences under the umbrella concept of peripheral areas. Rodríguez-Pose [22] identifies peripheral dynamic regions (in terms of localization) as those characterized by skills and high performance in strategic sectors of the global market, emphasizing that spatial and aspatial factors make generalizations impossible. This means that geographical remoteness does not necessarily cause marginalization, just as being central does not in every case determine prosperity [23].

This introduction shows the increasing efforts of the European agenda towards the reduction of territorial inequalities, as well as an extensive and vibrant international and multidisciplinary debate with deep connections to the principles of sustainable development, social equity, and territorial democracy. Right in the middle of this discourse, an ongoing research project developed by the authors is settled within the Institute for Research on Innovation and Services for Development (IRISS) of the Italian National Research Council (CNR). Starting with the Italian National Strategy for Inner Areas (SNAI) [24,25,26,27,28,29], the project aims at investigating possible strategies for reducing territorial inequalities and fostering a more equitable and balanced development in a systemic approach implementing an action-research protocol [30]. Consequently, the research is providing an in-depth study of policies and programs in the EU countries, as briefly described in the concluding section of this article about the research agenda, as well as the construction of a theoretical research framework that is the object of this article. This latter has been developed with reference to an international scenario through a preliminary screening of scientific literature and institutional documents to frame the context of territorial inequalities [31,32,33]. By exploring contributions from disciplines, such as regional and urban studies, economics, social science, and environmental studies, CNR-IRISS researchers found out that areas affected by conditions of territorial inequalities and peripheralization processes were labeled with multiple different terms, such as marginal areas, peripheral areas, inner areas, inner peripheries, and inland areas [11,34,35,36]. These remarks led the research group to start decoding the meanings and issues concealed behind each term in order to understand how territorial inequalities are addressed in different geo-political contexts and research fields and whether different terms are synonymous or identify different situations. According to these premises, the following research questions have been outlined:

• What is the phenomenon described by each term found in the literature referring to the topic?
• What are the causes behind these phenomena?
• Are there models to cope with the marginalization phenomenon?
• Do specific drivers emerge from the debate that can support development in contexts affected by territorial inequalities?

The researchers decided to approach these issues by developing a tailored Systematic Literature Review (SLR) protocol in order to analytically explore the terms that emerged from the preliminary screening, highlight possible connections with different scientific disciplines and/or geopolitical contexts, and analyze the evolution of the debate since 1990. The SRL protocol included both a quantitative analysis–observing the frequency of terms in time, disciplinary fields, and geopolitical contexts–and a qualitative analysis, selecting scientific contributions deemed relevant to the research goals, which were studied through four categories of analysis corresponding to the research questions: terms and phenomena, causes, models, and drivers. Through this protocol, by exploring and systematizing the literature, the study aims to contribute to setting the context for dealing with territorial inequalities.

Following this introduction, Section 2 describes the methodology for the SLR, the protocol, and the data collection; Section 3 presents the findings of quantitative and qualitative analysis; Section 4 regards the discussion; and Section 5 sets out the conclusion and research follow-up.

2. Materials and Methods

2.1. A SLR Protocol Studying the Marginalization Items

This research has been developed through a mixed methodology in which data were collected according to a SLR protocol and processed quantitatively and qualitatively by a group of three researchers. The SLR has been designed according to the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA Statement) [37] to explore and systematize the multitude of terms referring to areas affected by peripheralization processes detected across different disciplinary fields and geopolitical contexts. As acknowledged in literature, indeed, the usage of the SLR appears to be appropriate, particularly in a domain that requires the connection of many academic disciplines [37]. In accordance with the literature regarding approaches and guidelines to pursue a SLR [38,39], and specifically in accordance with the PRISMA Statement [37], authors dedicated great attention to developing the review protocol. This latter represents a key asset of a SLR [40,41], and Xiao and Watson [39] recognize three major stages for the protocol together with eight common steps and also assess this process as iterative in nature.

Given the research objectives and premises concerning the method, the protocol adopted by the researchers is consistent with the PRISMA Statement (see Supplementary Materials), including the four steps of identification, screening, eligibility, and inclusion [37], and follows the main steps mentioned above. After setting the field of study and defining the research questions, the researchers drafted a protocol according to the need for both quantitative and qualitative insights into the results of data extraction. Considering Xiao and Watson’s study [39], based on Paré et al. [38] and Templier and Paré [42], it can be said that the protocol hybridized a purpose of description with one of extending knowledge within the field of research. Specifically, a Scoping Review [43] was intersected with a Thematic Synthesis [44] to identify the conceptual boundaries and size of the field of study, available evidence, and existing gaps, and at the same time extract and synthesize the data through a thematic analysis based on the research questions.

The protocol was derived from Xiao and Watson [39] and includes the following steps:

• Searching of records in the Web of Science, then transferred into Mendeley and then into Excel;
• Screening for exclusion of ineligible records based on match criteria (some words recorded acquiring a far meaning from the relevant disciplines or contexts analyzed were excluded);
• Evaluation of the quality of records based on their responsiveness to the research questions that leads to a cluster of records to be analyzed qualitatively;
• Snowball approach to the qualitative cluster (back and forward);
• Extraction of quantitative data;
• Extraction of qualitative data;
• Analysis and synthesis of collected data;
• Reporting.

The entire activity was carried out in the 2019–2022 period, considering the first year was dedicated to data collection and methodology testing, the 2020–2021 period focused on data processing and database updating, and the 2022 period was mainly aimed at completing the reporting activity. Researchers planned a testing activity of the adopted protocol for the first 100 valid records, for which they quantitatively observed the disciplinary scope, geographic scope, contribution type, and items encountered. This phase was shared with the international scientific community during the AESOP Annual Congress Venice 2019 “Planning for Transition”, during which the proposed SLR protocol was validated as an effective method for achieving the proposed objectives of the research [31].

After that, a quantitative analysis of all archived records (347) was developed, which included, according to a scientometric approach, analyses regarding the distribution of publications over time, analysis of disciplinary fields, geographic areas, and document type. Once the main items collected were identified, the analysis focused on the time span covered and the geographical area of reference of the published studies. Additionally, a detailed analysis was carried out by geolocating the archived case studies, which showed how the characteristics of the areas and, therefore, the processes vary depending on the context being considered. This activity was presented at the fourth edition of the International Symposium “New Metropolitan Perspectives” and at the XII Study Day of the National Planning Institute of Italy in 2020 [32,33] and, subsequently, updated and revised as presented in the following paragraphs (Figure 1).

The activities then proceeded with a qualitative analysis of the 50 selected records, considering the four macro categories of analysis corresponding to the research questions posed: (i) Terms and phenomena; (ii) Causes; (iii) Models; and (iv) Drivers. Specifically, the researchers proceeded with the study of the entire contribution, compiling the results into thematic appendices (Appendix B) and an extended presentation of the results set forth in the following paragraphs.

2.2. Data Collection

The data collection involved several phases of work in which the researchers worked both in groups and in parallel. At the beginning, two researchers individually extracted information from articles for cross-checking. After reviewing a few articles together, the researchers reached consensus on what to extract from the articles and split up the work, maintaining frequent communication during the data extraction process and screening for inclusion, quality, and eligibility assessment. Doubts about some articles were resolved by the researchers discussing them together. Starting with the qualitative phase, the team has benefited from the third researcher.

Initially, the three main databases in which these topics appear were queried: Web of Science (WoS), Scopus, and Google Scholar. The three platforms filter the advanced search with different levels of accuracy. In the case of this research, while WoS preserved the appropriateness of the search using Boolean indicators regarding the subject categories, the search via Google Scholar and Scopus remained very large and required a considerable amount of work to eliminate contributions not relevant to the search. For this reason, the database was built through searches on the WoS platform. WoS’s searching criteria were:

• English language;
• Maximum timespan covered by WoS (1965–2020);
• Typology of products: scientific articles, books, book chapters, and conference proceedings;
• All databases from the Web of Science Core Collection (Citation Indexes);
• Subject categories: Agricultural Economics and Policy, Regional and Urban Planning, Social Issues, Cultural Studies, Demography, Urban Studies, Development Studies, and Economics.

Regarding the period of analysis, all items identified by WoS were collected from 1965 onward to observe them as a whole. Furthermore, to guarantee the exhaustiveness of the sample, we analyze only contributions published after 1990, when the digital age started. This recommendation is coherent with Xiao and Watson’s suggestion [39], who considered the digital era consistent in terms of information retrieval and synthesis. Items were searched by forming the highest level of alternatives through the combination of all selected adjectives (inland, inner, interior, internal, marginal*, non-core, periphery*) with multiple substantives (area*, context*, territory*, landscape*), obtaining seven queries like this one:

Ts = (“inland area*”) OR (“inland context*”) OR (“inland territor*”) OR (“inland landscape*”)

Queries were crossed with all scientific items found in the selected eight disciplinary sectors (Appendix A,

Table A2. Matrix highlighting the presence of each query in specific disciplinary fields (authors’ elaboration).

Query/Disciplinary Field		Agricultural Economics and Policy (70,017)	Regional and Urban Planning (178,332)	Cultural Studies (90,009)	Demography (75,272)	Urban Studies (176,837)	Development Studies (89,400)	Economics (1,066,111)	Social Issues (214,001)	Total
		#1	#2	#3	#4	#5	#6	#7	#8
inland area*/context*/territor*/landscape* (1579)	A	4	18	0	0	36	7	42	0	107
inner area*/context*/territor*/landscape* (1070)	B	0	29	1	0	53	2	14	3	102
internal area*/context*/territor*/landscape* (869)	C	1	7	0	1	18	4	11	1	43
interior area*/context*/territor*/landscape* (440)	D	0	6	1	0	9	2	11	0	29
marginal* area*/context*/territor*/landscape* (2141)	E	25	43	8	4	48	20	58	10	216
non-core area*/context*/territor*/landscape* (38)	F	0	1	0	0	3	1	1	0	6
peripher* area*/context*/territor*/landscape* (3171)	G	9	139	4	22	195	44	134	7	770
Total		32	176	7	14	230	55	189	13	1273

). The 1273 records collected were imported into Mendeley Desktop (version 1.19.8 © 2008–2020 Mendeley Ltd., London, UK), a free reference management software that automatically discarded duplicates and archived 570 records, and then exported to Excel, where the working database was built. This database was constructed starting from the general information retrieved from WoS and adding four new filters related to disciplinary fields, geographic scopes, contribution types, and identified items (Appendix A,

Table A3. Categories of information processed within the database (authors’ elaboration).

Category	Collected Data	Possible Choice
General information	ID	From #001 to #570
	Typology of the product	Journal article/book/book section/ conference proceeding
	Date	From 1965 to 2020
	Title of the product; Abstract; Name and surname of the first author; Affiliation of the first author; Name and surname of the second author; Affiliation of the second author; Name and surname of the editor/s; Affiliation of the editor/s; Title of the journal/book/conference; Name of the conference; Volume; Issue; Keyword; Page; Publisher; City of the publisher; DOI code; and ISBN code	Free/specific choice
Specific information	Discipline scope	Urban and Regional Studies/Geography/ Social Studies/Economics/Transportation/Environment/Multidisciplinary
	Geographical scope	Europe/North America/South America/Central America/Asia/Africa/Australia/any
	Typology of the contribution	Theoretical approach/Case study/Methodological approach/Project-program-policy
	Collected items	Inland area*/context*/territor*/landscape* Inner area*/context*/territor*/landscape* Interior area*/context*/territor*/landscape* Internal area*/context*/territor*/landscape* Marginal* area*/context*/territor*/landscape* Non-core area*/context*/territor*/landscape* Peripher* area*/context*/territor*/landscape*

, Figure A1 and Figure A2).

Through screening and quality assessment operations, developed by reading the titles, abstracts, and, in a few cases to be verified, the full papers, 223 records were excluded, 347 records were confirmed for the quantitative analysis stage, following the criterion of congruence with the objectives and research questions, and 98 were assumed to be relevant for the qualitative stage. Of these latter, 76 were found online and in national libraries and analyzed by reading the full papers, which confirmed 50 records as eligible for the qualitative investigation.

The in-depth study of the selected papers has been summarized within the bibliographic filing and retrieval of useful content to develop reflections regarding the following macro-categories: (i) Terms and phenomena; (ii) Causes; (iii) Models; and (iv) Drivers. The bibliographic record was designed considering ID, paper title, author affiliations, items encountered and possible definitions, and main topics addressed, and filed according to the same source IDs in a “Bibliographic Records” folder. Subsequently, the contributions were categorized according to the four macro-categories, and in parallel, a snowball search of the additional relevant contributions that emerged from the bibliographies of the contributions was initiated. For this phase, additional index sheets were produced and filed with the corresponding IDs in a folder “Emerged Theme Sheets” and a new archive in Mendeley “Literature from Snowball Analysis”, and finally an appendix summarizing the qualitative analysis was developed (Appendix B,

Table A4. Matrix synthesising the qualitative analysis by highlighting with an “X” the presence of macro-categories in the selected records (authors’ elaboration).

ID	Author (Year)	Title of Journal (J), Book/Book Section (B), and Proceeding (P)	Geographical Scope	Typology of Contribution	Macro-Categories of Analysis
					Terms and Phenomena	Causes	Models	Drivers
#004	Ruddle and Grandstaff (1978)	Technological Forecasting and Social Change (J)	-	Theoretical approach	X		X
#064	Portnov and Pearlmutter (1999)	Progress in Planning (J)	Multiple scopes	Theoretical approach	X	X	X
#079	Palang Alumae and Mander (2000)	Landscape and Urban Planning (J)	Estonia	Case study				X
#091	Kyrgiafini and Sefertzi (2003)	European Planning Studies (J)	Greece, Europe	Project/program/policy			X
#107	Labrianidis (2006)	European Planning Studies (J)	Europe	Theoretical approach		X	X	X
#122	Rodríguez-Pose and Fratesi (2007)	Growth and Change (J)	France, Greece, Italy, and Spain	Case study		X
#190	Fitjar and Rodríguez-Pose (2011)	European Planning Studies (J)	Norway	Case study			X	X
#206	Li (2012)	Growth and Change (J)	Beijing, China	Case study	X
#228	Rodríguez-Pose and Fitjar (2013)	European Planning Studies (J)	Norway	Case study			X
#230	Baumgartner, Pütz, and Seidl (2013)	European Planning Studies (J)	Europe	Case study	X		X	X
#237	Máliková (2013)	Mendelnet (J)	Czech Republic and Slovakia	Case study	X
#256	Halás, Klapka, and Tonev (2014)	XVII Mezinárodní kolokvium o Regionálních Vědách (P)	Czech Republic	Case study	X
#259	Bednářová and Laboutková (2014)	6th annual international scientific conference “Region in the development of society” (P)	Europe	Methodological approach	X
#271	Amara and Ayadi (2014)	Middle East Development Journal (J)	Tunisia	Case study		X
#272	Martín Martín, Aguilera, and Moreno (2014)	Tourism economics (J)	Spain	Case study				X
#321	Provenzano, Arnone, and Seminara (2016)	Procedia—Social and Behavioral Sciences (P)	Sicily, Italy	Case study	X			X
#325	Mudambi and Santangelo (2016)	Regional Studies (J)	Sicily, Italy	Case study			X
#328	Bohlin, Brandt, and Elbe (2016)	European Planning Studies (J)	Europe	Project/program/policy				X
#342	Las Casas, Murgante, and Scorza (2016)	Smart Energy in the Smart City (B)	Europe	Methodological approach			X
#344	Urso (2016)	Procedia—Social and Behavioral Sciences (P)	Italy, Europe	Project/program/policy			X
#346	Della Spina, Ventura, and Viglianisi (2016)	Procedia—Social and Behavioral Sciences (P)	Calabria, Italy	Methodological approach				X
#347	Calabrò, Cassalia, and Tramontana (2016)	Procedia—Social and Behavioral Sciences (P)	Calabria, Italy	Methodological approach				X
#349	Campolo, Bombino, and Meduri (2016)	Procedia—Social and Behavioral Sciences (P)	Calabria, Italy	Case study				X
#366	Dvoryadkina, Kaibicheva, and Shurova (2017)	Advances in Economics, Business and Management Research (P)	Russia	Case study	X
#379	Di Benedetto, Germanà, and Trapani (2017)	Procedia Environmental Sciences (P)	-	Theoretical approach	X
#404	Bertolini and Pagliacci (2017)	Bio-based and Applied Economics (J)	Europe	Methodological approach	X	X
#406	Guarino, Cutaia, Giacopelli, Menegoni, Pelagallo, Trotta, and Trombino (2017)	International Environmental Agreements (J)	Europe	Theoretical approach				X
#412	Di Ludovico and D’Ovidio (2017)	World Multidisciplinary Civil Engineering-Architecture-Urban Planning Symposium (P)	Europe	Methodological approach			X
#417	Chapman and Meliciani (2018)	Economics of Transition (J)	Europe (macro regions)	Theoretical approach		X
#429	Marques, Gerry, and Marques (2018)	European Planning Studies (J)	European frameworkcase study in Portugal	Project/program/policy and case study			X	X
#441	Oppido, Ragozino, Micheletti, and Esposito De Vita (2018)	Urbani Izziv (J)	Irpinia, Italy	Case study			X	X
#453	Calabrò and Cassalia (2018)	Smart and Sustainable Planning for Cities and Regions (P)	Calabria, Italy	Case study		X
#460	Scorza, Pilogallo, and Las Casas (2019)	Springer International Publishing AG, ISHT 2018 (P)	Basilicata, Italy	Case study				X
#461	Oppido, Ragozino, Icolari, and Micheletti (2019)	Springer International Publishing AG, ISHT 2018 (P)	Irpinia, Italy	Case study and theoretical approach	X		X	X
#462	Eder (2019)	International Regional Science Review (J)	-	Methodological approach, SLR		X	X	X
#471	Bassano, Barile, Piciocchi, Spohre, Iandolo, and Fisk (2019)	Cities (J)	Umbria and Campania, Italy	Case study—tool				X
#476	Meili and Shearmur (2019)	Growth and Change (J)	Switzerland	Methodological approach and case study	X		X	X
#491	Eder and Trippl (2019)	Growth and Change (J)	Austria	Methodological approach and case study		X	X	X
#493	Xu and Dobson (2019)	Journal of Entrepreneurship and Public Policy (J)	Guildford, UK	Methodological approach and case study		X	X	X
#499	García-Cortijo, Castillo-Valero, and Carrasco (2019)	Journal of Rural Studies (J)	Castilla-La Mancha, Spain	Case study	X			X
#517	Carpio, Fernandez, and Urbano (2020)	Applied Economics (J)	Spain	Methodological approach and case study				X
#529	Gallo and Pagliacci (2020)	Economia Politica (J)	Italy	Methodological approach	X
#539	Zullo, Marucci, Fiorini, and Romano (2020)	Environment And Planning B-Urban Analytics And City Science (J)	Italy	Case study		X		X
#545	Cotella and Vitale Brovarone (2020)	Tema. Journal of Land Use, Mobility and Environment (J)	Italy	Theoretical approach and case study	X	X
#548	Bachmann-Vargas and van Koppen (2020)	Journal of Environment andDevelopment (J)	Northern Patagonia, Chile	Case study	X	X		X
#550	Romagnoli and Mastronardi (2020)	Economies (J)	Italy	Methodological approach	X
#553	Capello and Cerisola (2020)	Growth and Change (J)	Europe	Methodological approach		X	X
#562	Dezio (2020)	Ciudades 23 (J)	Northern Italy	Case study				X
#566	Urso (2021)	Urban Geography (J)	Antola-Tigullio Valleys, Italy	Case study	X
#567	Cerquetti and Cutrini (2021)	European Planning Studies (J)	Italy	Case study				X

).

As can be seen from the diagram presented here (Figure 2), in which the flow and numbers of the protocol presented are shown, no literature products from outside the WoS query were included in the input. The researchers decided not to externally implement the database with Italian bibliographic sources, the basis of their preliminary study, to avoid the risk of unbalancing a study with an international dimension.

However, following the snowballing phase, those contributions found to be highly relevant were considered because they were cited by more than one contributor. These were considered only at the qualitative analysis stage. The circle was closed by ascertaining that these products corresponded to those studied by the researchers in the preliminary literature review phase.

3. Results

Results regarding the collected material are presented below in two stages, corresponding to the quantitative and qualitative analyses of the research.

3.1. Results from Quantitative Analysis

Quantitative analysis refers to the total sample of products found from 1965 onward. This material, while not exhaustive for quantification purposes, was very helpful in identifying the evolution of the debate regarding the selected topics starting from the year in which the first related papers were published (Figure 3).

Collected data show 1978 as the year when scientific production began and the years 1999, 2008, 2014, and 2017 as four peaks of interest on the topic. During the investigated time span (1965–2020), the first documents were published in 1978, following the institution of the European Regional Development Fund (ERDF), set up in 1975 to correct regional imbalances due to the predominance of agriculture, industrial change, and structural unemployment. Most of the documents are recorded after 1999, probably because of the interest gained by the subscription of the Maastricht Treaty in 1993, which introduced the Cohesion Fund, the Committee of Regions, the principle of subsidiarity, and the double novelty for structural and cohesion funds for the period 1994–1999 (ECU 168 billion). The second block of contributions is most likely related to the third block of cohesion policies (2007–2013), in which the budget was €347 billion focused on research, innovation, environmental infrastructure, and measures to deal with climate change. In 2014, the Italian Presidency of the EU Council promoted a vibrant debate about inner areas, resulting in the launch of the Italian National Strategy for Inner Areas (SNAI) and the fourth block of the cohesion policies (2014–2020). During the year 2017, there was a massive scientific production emblematic of the relevance of the topic within the political and scientific debate.

The second step of the quantitative analysis considers only items from 1990 onward, including 16 books/book sections, 65 conference proceedings, and 253 journal articles. A first data elaboration shows that the most document-rich disciplinary fields are Urban and Regional Sciences and Economics (Figure 4), the geographic contexts most populated by the research in question are Europe and Asia (Figure 5), and the most frequently encountered document type is the case study (Figure 6). Four items on eighteen emerge as dominant and are all terms consisting of the substantive area: peripher* area* (147), marginal* area* (60), inland area* (55) and inner area* (28) [33]. The term peripher* area* is the most present in the database, representing twice as much as the second term for frequency (Figure 7).

The research group conducted further analysis regarding the frequency of terms over time and in different geopolitical contexts. Moreover, a geolocation of cases across countries was developed to observe trends in the phenomenon of territorial inequality. Finally, a collection of new terms was retrieved that increased the narrative of the searched phenomenon in different geopolitical contexts and disciplinary fields.

The analysis of the most frequently used terms over time highlights the steady increase in the use of the term peripher* area*, a general increase in the use of marginal* and inner area*, and a similar increase in inner and inland area* until the period 2001–2005, when the term inner area* started to be more elevated (Figure 8).

Observation of the use of these terms in different geographical contexts shows that in Asia, the terms inland area* and peripher* area* are more frequent, in Africa, marginal* area*, and in Europe, peripher* area*. For the Europe case, the influence to use this term could be related to the promotion of ESPON’s GEOSPECS program, where the topics of this research are discussed under the “Inner Peripheries” umbrella concept. The term inland area* is more prevalent in Asia, while inner area*, marginal* area*, and peripheral* area* are more common in Europe (Figure 9). Considering the use of these terms in the two most populated disciplines—Urban and Regional Planning and Economics—new information emerges regarding the term inner area* that is used much more in Urban and Regional Studies than in Economics, and the cause could be related to the ESPON’s GEOSPECS program, which is more closely linked to this discipline (Figure 10).

The geolocation of the cases included in the selected papers shows the variability of the phenomenon in different geopolitical contexts, as shown in Figure 11 through the pins: in China, there is a concentration of studies on the east coast; in Spain, cases are mainly located in Catalonia and the Seville area; and in the UK, the phenomenon is showcased in both inland and coastal areas. A very different situation is found in Italy, where the areas of interest are scattered along the Apennines and far from urban centers, as recognized by the SNAI parameters.

A further result has been achieved in identifying other terms representative of the phenomenon of territorial marginalization, which are: resource peripheries, peripheral rural areas, marginalized communities, inland communities, peripheral centrality, fringe areas, less developed areas, less favored areas, lagging areas, inland locations, inland people, borderland regions, peripheral regions, peripheral cities, rural peripheriees, northern peripheries, and non-core regions.

In addition, this search permits identifying, albeit non-exhaustively, some key institutions that produce knowledge within territorial marginalization-related themes and some journals and conferences with specific aims dedicated to them. Regarding the research institutions with a significant production on the topic, the Gran Sasso Science Institute (GSSI) Social Sciences Research (Italy) is currently developing research tracks dedicated to “Inner Areas and Peripheral Development”, dealing with the socio-economic specificities and development trajectories of peripheral and marginalized areas, with a special focus on the Italian ones identified as inner areas. Within the context of the policy actions dedicated to them (as in the cited SNAI), specific attention is devoted to the urban-rural interactions, provision of public services, adaptation, and local development strategies of rural, mountainous, and remote areas. As anticipated in Section 1, CNR-IRISS (the research unit of the authors), based in Naples (Italy), is working on investigating the phenomena, causes, and models regarding territorial imbalances within an international framework, with a specific focus on Italy supported by empirical studies developed by action-research protocols. Among the others, papers and documents have been retrieved regarding the interdisciplinary project “Resettling Countries. Operational strategies for the valorisation and resilience of inland areas” (RI.P.ROVA.RE), which is aimed at creating resilient communities and territories and caring for landscapes and cultural heritage were developed by the University of Campania, Luigi Vanvitelli, the University of Salerno, and the University of Basilicata. The Center for Regional Economic Development (CRED) of the Universitat Bern is developing a core competence dedicated to “Urbanization and Periphery” through research and projects that observe the increasing growth of cities, the marginalization of peripher* areas, and the interdependence between cities and periphery. The Department of Geography and Regional Research of the Universitat Wien developed studies on new boundaries of innovation reflecting the potential of peripheral regions. At the London School of Economics (UK), regional growth and disparities, fiscal and political decentralization, regional innovation, and development policies and strategies are studied and transformed into policy practice, University of Stavanger Business School, and the Department of Working Life and Innovation at the School of Business and Law at the University of Agder, Norway, developed research and projects on Innovation and Regional Studies. The Department of Planning, Center for Mobility and Urban Studies, Land Management, and Geoinformatics of the Danish Center for Spatial Planning cope with the concept of Experience Economy (EE) as an economic innovation strategy in the periphery.

Among the conferences dedicated to territorial marginalization-related themes, the search recognizes as relevant in terms of number of products the Annual Conference of the Commission on Dynamics of Marginal and Critical Regions, the International Symposium on New Metropolitan Perspectives (Mediterranean University of Reggio Calabria, Italy), and the International Conference on Smart and Sustainable Planning for Cities and Regions (Eurac Research Institute for Renewable Energy). Regarding the journals and special issues dealing with these issues, the SLR protocol carried out identifies the following: European Planning Studies Vol. 15/4 special issue “Proximity, Knowledge, and Innovation in Peripheral Regions”, Vol. 14/1 “The Future of Europe’s Rural Periphery: Entrepreneurship, Employment, and Social Marginalization”, Landscape and Urban Planning Vol. 46/1–3 special issue “Rural landscapes in Europe: options for the future”, Local Economy Vol. 3/1–2 special issue “Regional and Local Economic Development in South Africa”, Growth and Change, Journal of Rural Studies, Population Space and Place, Regional Studies.

3.2. Results from Qualitative Analysis

In the following sections, the findings of the qualitative analysis of 50 contributions are reported and divided into four macro-categories that are related to the research questions set out in the introduction to this paper:

• Terms and phenomena;
• Causes;
• Models;
• Drivers.

3.2.1. Terms and Phenomena

The qualitative analysis recorded in 19 units dealt with terms and phenomena related to marginalization processes, which can be grouped under the following issues:

• Terms usage;
• Dichotomic visions;
• Spatial and aspatial features.

The complexity of the topic is represented by the wide range of terms used to identify areas affected by peripheralization processes that the research dealt with. The discussion regarding term usage to identify the phenomenon of peripheralization is complex and would merit much more focused studies. The following summarizes what the proposed research methodology has recorded.

On the terms periphery and peripheralization, researchers recommend reading Kühn [4], who comprehensively describes differences and correlations between them. Periphery or peripheric is intended as something situated on the fringe; the greater the distance from the center, the more peripheral is considered the location and something static that takes time to be changed. Moreover, the image of a pre-given space has social implications. Since 2000, this traditional conceptualization of peripheries has been enriched and completed by a process-centered perspective, peripheralization, which describes social relations with spatial implications and includes dynamism in terms of political, social, economic, and communicative processes. With this understanding, the phenomenon can be discussed from a microneighborhood scale to a macroscale that includes multiple countries, which unlocks the static nature of the process and the possibility of rapid change in which networks of actors play a key role [4].

Short distance links the concept of peripheralization to that of marginalization, understood as a multidimensional process referring to lack of integration, poor development, and economic, social, political, and cultural disadvantages. This latter could happen not only on the fringe, as witnessed by the conceptualization of the inner peripheries as a result of certain changes, but also in political and academic debate as well as in the socio-economic dynamics of the real world. Much has been written on this topic [14,16,45,46], and European projects have been developed under the ESPON 2020 program (mainly GEOSPECS and PROFECY). Beyond the ambiguity and overlap of the term inner peripheries with lagging regions, it seems common to trace some territories that, although centrally located, present (in relative terms) problems in accessing services of general interest and socio-economic deprivation, which cannot be explained solely through localization.

In some cases, the terms peripheral or rural may not correspond to the characteristics of some regions outside the metropolitan area, which may not suffer from serious problems of abandonment or marginalization [47], but simply be “regions with fewer opportunities for local external interaction because they are small (i.e., lack of critical mass), sparse (i.e., lack of physical proximity between actors), and/or lacking in diversity” [48] (p. 493). In these cases, the literature calls them non-core regions, using this umbrella term to consider the heterogeneity of regions across Europe [11,31,46,49]. In this regard, an interesting study by Baumgartner et al. [49] (p. 1097) declines the attributes of non-core regions based on the dichotomy urban-rural and center-periphery through the topics concerning economic environment, natural environment, social environment, human capital, settlement, accessibility, and aspatial distance.

In regional studies, these areas are often defined in contrast with core areas, highlighting a dichotomic vision of territorial development by setting urban center-periphery and urban-rural areas [1,49], such as the core-periphery paradigm [12,50]. A great deal has been said about these terms, to the point of considering it difficult, if not impossible, to analytically extract common elements from the variety of uses of the center-periphery metaphor. In this regard, the study on new industrialization processes in the old industrial regions of Russia is interesting, where numerous approaches to defining peripheral areas are recorded: geometric, ecological, social, economic, political, innovation, and historical [51].

This domain-dependency model is confirmed by the theory of Economic Geography, which highlights the incremental process in which central areas become increasingly attractive and peripheral areas increasingly disadvantaged [52,53]. “This paradigm links the interrelated gaps in demographic and economic conditions to the spatial fields over which they occur. Whereas the core is considered to be a highly urbanized region in which both population and economic actions are concentrated, the periphery is distinguished from the core by its contrastingly sparse population and lagging economic development [50]” [54] (p. 240). Mostly, the paradigm, which refers to both developed and underdeveloped countries, reflects on the interrelationship between the concentration of economic activities and population. In fact, the center is rich in activities, services, and people, while the peripheral areas present high rates of unemployment, educational deficits, migration flows, as well as income poverty and inequalities. More recently, studies have investigated these inequalities in different geographical contexts through quantitative analyses of socio-economic variables, such as per capita income [55,56] or goods and services [57]. The paradigm has evolved over time from a functional relationship between regions, where the less developed exported natural resources to the core areas on which they depended, to a relationship between inner cities and their hinterlands [49]. In addition, the domain-dependence relationship that influences the economic structure and exchanges between core and peripheral areas is reviewed, considering the new economic geography theory in which the main variables become the flow of resources between the center and the periphery and agglomeration economies. These variables are studied through the functional classification urban-periurban-peripheral, which represents the spatial clustering of resource flows that extend beyond the administrative boundaries and places greater emphasis on the urban-rural interface [58]. The latter is considered the place where multiple social, economic, and political factors interact in complex ways. Here, an array of networks connect urban consumers and rural producers, bringing periurban areas into a regional decomposition analysis [58,59,60], linking marginality and peripherality to rural areas, and highlighting that these attributes may not be applied exclusively to rural environments [61].

Over the past two decades, the debate on the urban-rural dichotomy has greatly increased by emphasizing the need to overcome the dichotomy itself by transforming it into a relational-systemic approach based on an ecological perspective [48,62,63,64,65,66,67,68,69,70,71,72], by considering the interfaces between urban and rural, and by codifying urban-rural partnerships. The ecosystem approach (see also Section 3.2.3) values nature as a means for the sustainable provision of goods and services in a developmental dimension, considering the environment “as the intersection between the sociocultural construction of nature and the natural components and ecological processes” [73] (p. 371).

Finally, the dual nature of the phenomenon, spatial and aspatial, can be considered a red thread through which to explore the different issues concerning the phenomenon. For example, Jauhiainen and Moilanen [74] are trying to synthesize, pointing out that there is a geographical and functional perspective. The first one is characterized by remoteness, which leads to few relevant development actors and low innovation capabilities as well as entrepreneurship, and the second is characterized by weak human capital, intended as weak institutional structures, poor quality of information and communication technology infrastructure, and poor market connections. The debate also includes socio-spatial patterns in order to analyze territorial inequalities. As Bachmann-Vargas and van Koppen [73] (p. 367) describe, “more recent spatial research thematizes the peripheralization process as a way to understand social dynamics with spatial implications, specifically related to mechanisms of out-migration, dependence, disconnection, and stigmatization [4]”, defining peripheralization as a multidimensional and dynamic process. A cornerstone of the literature on this topic is Copus [2]. From a traditional and conventional perspective, he defines spatial peripherality in conventional terms through three types of disadvantages that the phenomenon causes: causal, contingent, and associated. From a changed perspective influenced by economic and technological changes, Copus [2] recognizes the elements of aspatial peripherality as related to: technological infrastructure, human capital capable of using technological tools, local business networks, local embeddedness and civic society, local institutional structures/networks, links to European/global markets, and information networks.

A representative synthetic indicator of both spatial and aspatial issues is that relating to depopulation, by which is meant a low level of users, determining the reduction of basic services, such as schools and health services, as well as public transport services, fueling an overall spiral of decline and a dependence of rural areas on urban nodes. Talking about depopulation, the ESPON ESCAPE project (European Shrinking Rural Areas: Challenges, Actions, and Perspectives for Territorial Governance) distinguishes between active shrinkage, driven by migration and more typical in Central and Eastern European countries as well as in Southern Europe, and legacy shrinkage, driven by distorted age structures resulting from former migration processes and a recurrent phenomenon in Western European fringes [75].

3.2.2. Causes

The qualitative analysis recorded in 14 units dealt with the topic related to causes of marginalization processes, which can be grouped under the following issues:

• Spatial and aspatial factors;
• Cyclicality of the economy;
• Geopolitical changes;
• Lack of a city-region paradigm with a focus on innovation;
• Lack of urban-rural linkages.

The scientific debate is increasingly recognizing that peripherality and the reasons causing peripherality are both spatial and aspatial [62,76,77]. The awareness of the latter occurred around 2000, when major economic changes occurred in response to market, technological, and political interventions, which changed the transport and communication infrastructure, pushed the service sector and the light manufacturing sector against the heavy manufacturing sector, and produced rapid change regarding the information and e-commerce sectors. This meant that the economic potential of regions is not at all dependent on location, going beyond the agglomerative advantage occurring in core areas, that geographical remoteness is not a sufficient factor for delimiting peripheral regions, and that peripheral areas could also be considered innovative [73,78].

Focusing on the spatial reasons, Copus [2] recognizes two main families explaining the economic processes behind the peripheral disadvantage: the land economy and regional science regarding systematic changes in land value and economic activity with increasing distance from urban/industrial centers; and the high development economics that emphasizes the regional divergence in terms of levels and growth of economic activity. This last point is addressed by the literature review developed on processes of marginalization in European rural areas by Cotella and Vitale Brovarone [75]; they highlight that, since the second half of the last century, the active population has been attracted by urban centers. This caused a progressive depopulation process. Portnov makes it a mere question of distance from the centers, observing that “migration attractiveness and the settlements’ attractiveness to private investors occur when the distance to major urban centers exceeds 20 ± 30 km” [79] (p. 276) and pointing out that this absolute distance may vary from one context to another depending on transport conditions and commuting habits.

Regarding the aspatial reasons, studies developed by Copus [2] need to be considered, already useful for the description of the phenomena (cfr. Section 3.2.1); Labrianidis [76] (p. 5) who recognises “the lack of a critical mass to support development of specialized services, the lack of electronic infrastructures and people with the necessary skills to operate them and manage the information”; Copus and Skuras [80] who consider them as dependent from the quality of social capital, governance or business networks; Copus et al. [14] who identify the exclusion from institutional, decisional, economic and cultural networks; and Vaillant and Lafuente [81] who present the inappropriate socio-cultural traits of the informal institutional framework of regions far away from metropolitan areas.

Observing the scenario at a non-local scale and through a territorial system analysis, the relationship between the cyclicality of the economy and marginalization processes is widely discussed. First of all, it is deemed risky to directly link large cities with economic success by confusing correlation and causality [82,83] because “the relationship between inequality and growth is complex and highly dependent on the level, stage, and cyclical position of economic development, as well as on the spatial scale considered” [84,85,86] (p. 1443). Portnov and Pearlmutter [54] report that peripheral settlements are more vulnerable to negative changes in the national economy as a whole, such as recessions. Specifically, as Rodriguez-Pose and Fratesi [87] summarize, some authors affirm that regional disparities tend to act in a pro-cyclical manner, increasing in periods of economic expansion and decreasing in periods of slow growth. This pattern is identified for short-term growth processes regarding the EU as a whole [88] and, specifically, Greece, the UK in the period 1984–1993, as well as Spain in the period 1985–1999. Other authors evidence an anti-cyclical relationship between regional disparities and regional growth; that is, disparities diminish in periods of high growth and increase in periods of low growth. This pattern has been identified in Finland for the period 1988–1995 and in Spain for the period between 1955 and 1985. The study of Rodriguez-Pose and Fratesi [87] confirms the pro-cyclical pattern, underlining that sheltered economies [89,90] are emerging in Portugal, Italy, Greece, and Spain (the PIGS countries), “leaving many of their poorest regions progressively detached from the market and more dependent on factors such as public employment and state transfers and assistance than on viable entrepreneurial initiatives” [87] (p. 623).

Marginalization processes regard geopolitical changes as well, causing disparities, especially across regions within Central and Eastern European Countries (CEECs) over 1991–2011. Starting from the factors identified by Rodríguez-Pose [22] to explain disparities in EU original member states in the 1980s, Chapman and Meliciani [91] analyze increasing regional disparities in newcomer regions after the end of Socialism, also by introducing a new category, that of “successful Foreign Direct Investment (FDI)-based restructuring”, in order to understand catching-up/falling behind processes in CEECs. Among factors influencing regional growth, they single out regional specialization, the ability to attract FDI flows, and geographical position. In newcomer regions, the variability in per capita GDP highlights that peripheral regions are generally located on the eastern borders of each country and are the farthest from the core of Europe; capital regions are the great winners of transition; all peripheral regions specialize in agriculture, both in 1991 and in 2011. By contrast, successful FDI-based restructuring regions were specialized in either industry or services in 2011, raised their specialization in one of the two sectors over 1991–2011, and attracted a share of FDI that is above the country average (without the capital). In a different geopolitical context, such as Tunisia, since the mid-1980s, institutional policies addressed towards privatization and economic opening have increased regional inequalities, with a concentration of infrastructure, private investment, competitive poles, companies, and jobs along the coastal areas. The consequences in terms of economic and employment inequalities were among the issues of the Tunisian revolution [92].

Moreover, the lack of a solid city-region paradigm is recognized as one of the reasons for territorial marginalization [69,70,93]. Harrison and Heley [94] highlight that the established center-periphery dichotomy emphasizes the role of the metropolis as locomotives of economic competitiveness and rural areas (here intended as peripheral) as the carriages, residual players in the growth of the region [71], with a debilitating effect on rural representatives’ empowerment [68]. This underestimation of the role of peripheral areas for competitiveness is also highlighted by Eder [95], referring to the literature in geography of innovation that “focuses on successful core regions, implicitly assuming that there is no innovation in peripheral areas” [95] (p. 119). This can probably be attributed to the dominance of territorial innovation models (TIMs) that assume “spatial proximity and urbanization economies are beneficial or even mandatory for innovation; this would mean that firms in peripheral settings could not innovate” [95] (p. 120). As Eder reports, reasons that may hinder innovation in peripheral regions include lack of financing [96], poor governance [97], and the challenges of such regions in becoming integrated in knowledge-based commodity chains [98]. Tödtling and Kaufmann [99] (p. 1215) generally note for peripheral regions “a low level of R&D and innovation due to a dominance of SMEs in traditional industries, weakly developed firm clusters, few knowledge providers, and a weak endowment with innovation support institutions”. Instead, Kühn [4] tries to summarize by linking the reasons for peripheralization processes to the lack of innovation (in terms of economic polarization theory), the production of socio-spatial disadvantages (in terms of social inequality theory), and conditions of dependency and exclusion (in terms of political theories).

One more research line regarding causes of peripheralization could be the concept of urban-rural linkages [100], in particular the different uses of and links between them [75]. For example, the proliferation of second homes and accommodation facilities for tourism and leisure affects the importing economy (in positive and negative ways), political and cultural models, and transforms rural areas from places of production to places for consumption for tourism and leisure, neglecting the value of the natural capital [101]. These conditions generate a lot of rural civitas, i.e., the set of social ties, functions, services, and institutions capable of offering citizens the advantages of a civilized life [102], and a widespread feeling of abandonment in rural communities, belonging to places that do not matter [103].

3.2.3. Models

The qualitative analysis recorded in 19 units dealt with the topic related to models to contrast marginalization processes, which can be grouped under the following issues:

• Spatial and aspatial proximity;
• Agglomeration economies and archipelago economies;
• Entrepreneurial ecosystem.

The debate on development models is already argued in Ruddle and Grandstaff [59], underscoring the unsuccessfulness of transferential development based on technology transfer from the most developed to the most disadvantaged areas. They propose a transformational model “suited to marginal areas and to the implementation of equity policy” because it aims at working “initially at small-scale, processional transformations of existing traditional systems in order to link them, eventually, to international systems” [59] (p. 121). It does not exclude the transfer of technology, but it emphasizes the need to adapt to the context. The issue of differentiation of models in peripheral contexts is still widely debated, especially within the geography of innovation, to deepen spatial conditions, but not only those that favor an innovation environment.

The transition emerging within the scientific debate is from a model based on agglomeration theory and physical proximity for innovation to a model based on cognitive and organizational proximity [104,105]. Portnov and Pearlmutter [54] (p. 301) argue that “compact development clusters linking urban settlements of different sizes may help to sustain the growth of initially underdeveloped regions”, still emphasizing the physical proximity. In this perspective, a large body of literature argues that the city is the place of innovation (one among all: [106]) that is most likely to be generated by large agglomerated economies, prioritizing spatial conditions for development processes. Actually, “approaches like Territorial Innovation Models (TIMs) with their emphasis on spatial concentration [107] are still influential and widely used” [78] (p. 1512). This spatial and economic concentration in many European contexts has contributed to a territorially polycentric development, excluding areas and contributing to inequalities [108]. In some cases, this phenomenon is supported by infrastructure networks, particularly transport [109]. In fact, scholars think that the remoteness of non-core areas is a physical condition that makes them disadvantaged because of their relative shortage of agglomeration economies and their geographical distance to the hotspots of innovation [86]. The recent debate about the geography of innovation is trying to overcome this model of metropolitan areas as the only ones able to produce innovation. It investigates how peripheral territories can innovate, highlighting aspatial features that can lead to innovation. Indeed, peripheral contexts capable of innovation are observed, and current theoretical developments provide insights about the conditions that make it possible, rethinking the connection between geography and innovation through conceptual and empirical works [48,78,95]. Some authors argue for this capability to innovate through a systemic approach to regional innovation development based on collaborations, networks, and learning processes among actors [110,111], especially referring to the entrepreneurial sector: some firms are able to combat the disadvantages of a peripheral location and a small population size by developing cooperative relationships with relevant global networks. Networking is a relevant topic in the debate both in spatial and aspatial proximity approaches, and the importance of business networks for entrepreneurship in rural and peripheral areas is underlined, distinguishing between horizontal networks (mainly with local linkages) and vertical networks (mainly with non-local linkages) [76].

In this perspective, regional hubs settled in the periphery can successfully produce innovation and economic development through extra-regional knowledge linkages [112]. “For example, peripheral areas can be linked via organizational, cognitive, and technological proximity to other (core) areas and use these forms of proximity in their innovation process. Consequently, geographical distance is no longer the whole story” [95] (p. 121). An alternative perspective to the local buzz perspective, which suggests that geographical proximity between actors fosters unintended exchange as well as intended exchange by virtue of face-to-face interactions [113], contributes to the prevailing “understanding that dense, highly urbanized regions are more likely to produce innovations than non-central regions” [48] (p. 496). While not denying the role of urban agglomerations and clusters for development and innovation, this approach is based on the model of the archipelago economy or global pipeline, which considers the sources of knowledge available on a global scale as enabling even a lagging or spatially peripheral region to become innovative. This process involves the interaction with networks of actors beyond the region and the identification of alternative solutions to specific problems related to the physical context [48,95,112,114,115,116]. This model implies a transition from a closed regional environment to an open interregional system, considering that “in such a dynamic system, technological learning, entrepreneurial strategies, coordination systems and institutions, and overall regional conditions are factors that determine firms’ attitudes to innovation” [76] (p. 6). The role of digital technologies is highlighted as strategic for addressing open innovation processes in peripheral regions, as well as open data, because geographic isolation no longer implies isolation from cultural, scientific, and technical changes [48,117]. However, as already argued about reasons for territorial inequalities (see Section 3.2.2), the issue of the digital divide was already discussed in 2006 by Labrianidis et al. [118], who linked it not only to a lack of ICT supply but also to a lack of ICT demand. As already cited by Copus [2], this issue is relevant when reflecting on how human capital is able to manage this ICT heritage.

As previously highlighted within the debate on the geography of innovation, many authors discuss entrepreneurial-driven local economic development [119], underlying that entrepreneurs play a role at the local, regional, and national scale, encouraging economic diversification, and enhancing the social wellbeing of their community by supporting community activities. In dealing with case studies of small enterprises, opportunities generated by social and spatial proximity are combined with economic and knowledge networks outside the region [49,120]. A more holistic approach proposes a model based on building an entrepreneurial ecosystem as “an interconnected group of actors in a local geographic community committed to sustainable development through the support and facilitation of new sustainable ventures” [121] (p. 3). More recently, Autio et al. [122] (p. 74) have emphasized the importance of digitalization defining the ecosystem as “a digital economy phenomenon that harnesses technological affordances to facilitate entrepreneurial opportunities pursued by new ventures through radical business model innovation”. In literature, the ecosystem is mainly addressed as a spatial concept, characterized by various actors and resources involved and located in close proximity, but in recent years it has acquired non-geographical characteristics thanks to digitalization, as argued by Xu and Dobson [77]. Although the more notable entrepreneurial ecosystems are reported in major urban centers thanks to high levels of institutional and infrastructural support, peripheral places can take advantage of digital technology and build an entrepreneurial ecosystem through a holistic collaborative approach to address challenges, such as finance, talents, socio-cultural environment, infrastructure, markets, and policy. Low population concentration implies that not all the desired players (e.g., investors and marketing) are located in the same area, but resources can be accessed globally if the appropriate infrastructure and support mechanisms are set up. These conditions are strongly related to the capabilities of governments and policies in shaping the ecosystem, grounding interventions in the local context, and building with a long-term vision.

These topics are also linked to regional innovation systems (RISs) and regional innovation-oriented policies, which also represent the theoretical framework for many studies investigating innovative activities in peripheral regions [95,110,123]. “According to Asheim and Gertler [124], RISs can be thought of as interacting constellations of firms, organizations, and institutions that collectively mold innovative behavior, thereby influencing regional economic performance” [125] (p. 2220). However, recent studies on RIS highlight the requirement for a variety of knowledge bases and knowledge-generating organizations to support development processes, conditions that are scarcely available in peripheral areas. Therefore, these territories should rather develop innovation paths based on endogenous characteristics and resources than import models that have been successful elsewhere [125].

Discussion on regional innovation systems and the promotion of place-sensitive innovation highlights the role of formal institutions as well as social capital for more sustainable and socio-territorially empowering forms of innovation [116,125]. Therefore, the debate includes discussion on territorial capital in terms of material, human, cognitive, social, and relational assets for facing place-specific socio-economic challenges [126,127,128], in line with the principles of the Smart Specialization Strategy adopted by the EU. The concept of territorial capital highlights the richness of these territories, opposing the codification of them as non-competitive areas and also pointing out the need to enhance the ties between communities and local resources by involving key actors in collaborative and co-design processes [30,46].

3.2.4. Drivers

At last, the qualitative analysis recorded 26 units dealing with the topic of the main drivers for territorial development in peripheral areas. The literature highlights entrepreneurship as the crucial sector, together with specific focuses on the role of the natural capital and tourism sectors for enhancement initiatives in these contexts. A large part of the selected articles addresses the entrepreneurial sector as a driver of innovation and development through the analysis of literature and case studies, as already shown in the models’ section, from a different perspective. By investigating how enterprises in peripheral contexts can contribute to territorial competitiveness, the authors mainly focus on two issues: (i) what kind of enterprise can be successful and competitive in these contexts; and (ii) how entrepreneurship influences regional development, deepening what kind of relationships it can have inside and outside the context to trigger territorial competitiveness.

The most exhaustive research works collected through the application of this SLR protocol are Baumgartner et al. [49], referring to the period 1999–2011, and Eder [95], referring to the period 1960–2016. By analyzing 46 European cases, Baumgartner et al. [49] evidence three types of entrepreneurship: immigrant entrepreneurship, that is, immigration from the city to non-core regions, often with a wider range of managerial experiences, a broader social network than local counterparts, and greater knowledge of the outside view; community entrepreneurship and social entrepreneurship, in which a key role is played by social capital “considered as being created and enhanced by local initiatives which foster mutual trust within a community [129,130,131,132] or which might create social value such as public goods and services” [49,133,134] (p. 1103). Furthermore, the extended analysis shows that all kinds of entrepreneurship in European non-core regions aim to create added value locally, thanks to the ability of individuals to identify windows of locational opportunities, coupled with personal risk-taking [49]. The issue is strongly linked with constraints/barriers in peripheral/remote contexts to be faced (see Section 3.2.2) in terms of weaknesses and challenges to highlight successful features and performance of enterprises that can be strategic for compensating some disadvantages. The role of public entrepreneurship is highlighted for assuring permanent renewal of governmental structures even in non-core regions, as well as the role of local facilitators for entrepreneurial activities and linking private entrepreneurial initiatives to the institutional framework. Research and policy recognize entrepreneurship as an essential element of growth-oriented regional policies for turning peripheral weaknesses into core business assets [49].

The relevance of public institutions and policies in supporting change as well as the need for institutional change are underlined by some authors with reference to a more territorial or place-based approach to developing tailor-made regional policy instruments and identifying conditions under which the entrepreneurial potential in non-core regions can develop in a productive way [49,76,78]. Some studies dealing with this challenge also aim to outline options for policymakers and suggest avenues for future research, as Eder [95] states in his systematic literature review. In this work, innovation is understood as firm-level economic innovation, predominantly observed in the manufacturing sector. Among the preconditions to triggering or maintaining innovative activities, the review refers to the presence of a critical mass of actors and organizational and/or institutional thickness, such as the support of tailor-made innovation policies and regional actors like universities. In this SLR, most studies evidence the role of building networks for innovative SMEs in the periphery, including public institutions, extra-regional networks, as well as external linkages that are essential in order to get access to the latest research or to specialized service providers and to gain knowledge about markets, and the presence of foreign workers to establish such international ties. Peripheral firms seem to be predominantly innovation followers and not leaders; however, this evidence may be obtained using investigation categories designed for the analysis of central areas that may not be appropriate for intercepting innovation in peripheral areas. Peripheral regions might be able to provide an innovative environment for small and medium-sized enterprises (SMEs), but widespread opinion is that one cannot generalize because of the wide variety of contexts referring to peripheral conditions. Finally, the results highlight that “the implicit assumption often found in the literature that innovation can only be found in central areas and that peripheral areas exhibit no innovative activity at all is therefore not confirmed empirically” [95] (p. 130).

As Eder highlights and the present study confirms, the state of the art is dominated by exploratory investigations and case studies of successful regions, so the identification of crucial factors for innovation might be biased. Some favorable features and conditions inside and outside the enterprise are highlighted by some authors, such as the capacity to attract skills from other territories, also through technological infrastructure and marketing tools [135,136], open-mindedness, and individuals able to lead a change of mentality [112], as well as the interplay between endogenous and exogenous entrepreneurship for compensating peripherality [76].

Single case studies are carried out by some authors through the engagement and listening campaigns of entrepreneurs and employees to address successful factors and/or limits. In the case of firm innovations in Southwest Norway, trust and open-mindedness are identified as key managerial values, and “the most innovative companies appear to be combating the disadvantages associated with a peripheral location and a small population size through developing strong cooperative relationships with relevant global production networks within their industries” [112] (p. 570). Developing a propensity for networking represents a factor in the success of the business initiatives in the Tua Valley Sustainable Entrepreneurship Programme (TVSEP) in the North Interior of Portugal, also highlighting the role of the public administration (Municipality) in informing and supporting participants [125]. In seven successful firms in Swiss small towns, three features are identified: internal diversity, obtained through many specialists as well as internal mobility within multinational firms; multiplexed interactions between workers at different hierarchical levels; and external diversity as firms reach beyond the region to overcome deficiencies in local knowledge sources. These conditions must be supported by improving adequate conditions in the context, such as transport connections, high-capacity internet, and adequate levels of services such as education and health [48]. In the case of innovative firms in the Austrian periphery, compensation and exploitation strategies have been identified, such as high levels of internal competence, global pipelines, global and virtual buzz, the establishment of branch offices in major cities, and employer branding activities [78]. Authors also highlight some benefits of a peripheral location, e.g., proximity to natural resources, as well as the remoteness that is helpful for the high levels of secrecy required in some activities. Moreover, in small contexts, innovative companies can obtain support from stakeholders, and “if regional policy makers recognize the significance of the few innovative firms in their regions, this should increase the likelihood of tailor-made policies” [78] (p. 1515). In a more systemic view, Xu and Dobson [77] describe challenges for building entrepreneurial ecosystems in peripheral places, reporting the case of a digital gaming cluster in Guildford, a town in the UK, exploring a fully digitalized industry. Ecosystems represent an opportunity to achieve critical mass and implement appropriate conditions for enterprises, but the theoretical and empirical frameworks are still to be improved, as are the capabilities of governments and policymakers to plan investment programs and incentives to attract talents and businesses with a long-term evolutionary view.

Entrepreneurship is also addressed in the agro-food sector by Baumgartner et al. [49], linked with the issue of natural capital in peripheral areas, both in terms of agricultural production and innovative enterprises [64], considering multiple interactions of landscape with economic, social, and cultural contexts [137] and often overlapping with the issue of rurality. Some authors highlight the urgency for a diversification of socio-economic activities and services related to agriculture, including terms such as multifunctional agriculture, smart land, and high-natural value farmlands [138]. In an exploratory study of small food processing firms in 11 European peripheral regions, De Noronha Vaz et al. [139] highlight the importance of regional cooperation and networks to stimulate innovation in SMEs [49], the potential role of social media to mitigate the unfavorable location of agribusiness firms in rural peripheral areas and to reduce the distances between firms and users [135], as well as opportunities from smart specialization strategies [65]. The debate about natural capital is also linked with the contribution of agriculture to ecosystems and with the broader issue of ecosystem services, underlining that “inclusion of measures to assess and protect existing ecosystem services [140,141,142] in territorial governance processes could be an incentive for local economies” [101,143] (p. 728). The need to overcome the dualism between environmental protection and innovation is highlighted by integrated synergies between environmental discourses and development discourses [73].

Indeed, in some marginal territories, such as Italian inner areas, the landscape is a specific asset of local identity, a cultural heritage of tangible and intangible resources [144] that should be enhanced to trigger development and achieve local attractiveness and competitiveness, involving local key actors to support territorial strategies [30]. On the one hand, the recognition of the value of natural capital in environmental terms emerges both in terms of biodiversity goals and of economic opportunities; on the other hand, the cultural and social value of the landscape is highlighted, also from a tourism development perspective [46]. Thus, a sector with many connections to enterprise and natural capital regards tourism. A relevant contribution comes from some authors who reflect on how tourism policies and practices can contribute to reducing disparities between regions by triggering place-based regeneration processes built on the enhancement of natural and cultural resources and ecosystem services related to cultural and recreational dimensions [73,145,146,147,148]. Tourism destinations are also designed as participatory processes and public/private partnerships in which local governments and cultural organizations can involve stakeholders in a multilevel process for improving regional service systems [149,150]. In this perspective, tourism is investigated not only as a set of economic activities but as a multidimensional cultural practice, bringing together resources such as food, nature, and culture [151] with social capital, highlighting the role of cultural and creative industries, horizontal and vertical integration of cultural industries with other local productive sectors, and a combination of bottom-up and top-down approaches [152].

4. Discussion

The results of the qualitative-quantitative analysis, on the one hand, highlight the non-exhaustive nature of the study and, on the other hand, open up the debate on relevant issues for addressing territorial inequalities. The non-exhaustiveness of the work lies in: (i) the limitations of the choice of a single citation database (WoS), which, although necessary to obtain the refinement of the results achieved, restricted the field of investigation; and (ii) the selection of terms deduced from the initial screening of the literature. Regarding this second point, as emerged from the quantitative findings (see Section 3.1), the phenomenon of territorial inequalities is studied and narrated through a richer multiplicity of terms than those selected at the outset due to the dynamic nature of the process. For example, the findings highlight that adjectives such as regional and rural should have been included in the search because of their deep connections and overlapping with the topic, the policies, and the scientific debate. As for the opportunity to address processes, the qualitative analysis led to the identification of peripheralization and marginalization as highly discussed items. In fact, the study includes their definitions, despite not having considered them in the research in WoS. The evidence encouraged us to explore terms referring to processes in order to overcome a static approach to phenomena, recognizing a dynamism [4] that may be incremental but does not exclude reversibility.

Regarding the exploration of terms and meanings, the SLR implementation allowed the researchers to identify the definitions of terms such as peripher*, marginal*, inner, and non-core area*, whereas no definitions have been acknowledged for terms such as inland, interior, and internal. The characterization of the different terms used worldwide to address the topic is the first useful contribution to setting the context for understanding a multifaceted phenomenon by proposing a tentative scheme of definitions. However, the analyzed terms refer to very heterogeneous phenomena, from the micro-neighbourhood scale to a macro-scale encompassing several countries, also including territories centrally located but with problems of access to services and situations of socio-economic deterioration, such as the inner peripheries, and varieties of the center-periphery metaphor from which derive dichotomies underlying umbrella terms, such as non-core regions as well as a domain-dependency model.

Regarding the maturity of the topic, the prevalence of case studies within the literature can be interpreted from different perspectives. As highlighted by the Systematic Literature Review carried out by Eder [95], it suggests that the topic is still in an exploratory phase. This recurrence of fieldwork regarding issues, practices, and projects, paired with the lack of generalization and systematization, can be considered a consequence of the early stage of studies in the field. Nevertheless, it can also be linked to the specificity of the topic and the difficulty of reaching generalizations useful for theorizing about the characteristics of the phenomenon and possible strategies for dealing with it. The site-specific nature of the marginalization processes as well as the strategies implemented to reverse these processes have been highlighted by the case-study protocols. The low number of books/book sections, which emerged from the quantitative analysis and was confirmed by the qualitative one, also suggests both an exploratory phase of the topics as well as publishing trends and requirements in the different disciplines.

Therefore, the research evidences an evolution of the concept of the peripheral, which is not investigated only through spatial causes related to the geographic location of remoteness or distance from the centers but also includes the analysis of aspatial factors that contribute to territorial inequalities. These latter could also be useful to implement new models to measure the phenomenon of territorial inequalities. Spatial and aspatial issues—widely discussed in understanding causes for marginalization processes—also characterize the debate on models for supporting development in peripheral territories. On this last point, Copus [2] highlights the role of both issues in developing EU policies in order to replace a core-periphery pattern with a more balanced polycentrism. Indeed, more recent literature addresses proximity from not only a spatial perspective but also cognitive, organizational, and technological ones, while not denying the role of urban agglomerations and clusters [120], switching from Territorial Innovation Models (TIMs) to a model of an archipelago economy, and rethinking the trade-off between competitiveness and cohesion.

In the last decade, the issue of development and innovation in peripheral contexts has received increasing attention, especially in the field of the geography of innovation [95]. The rising number of papers, special issues, and edited volumes on innovation outside of core areas is confirming the potential of peripheric territories in terms of innovation and the increasing interest in studying it [153,154,155,156]. Accordingly, most of the contemporary literature tends to demonstrate that some peripheral regions are endowed with expertise and specific performance in strategic sectors for the global market, generating catalyst effects despite their marginal special positioning [22].

In this debate, the topic of entrepreneurship emerges as a key factor for growth-oriented regional policies, addressed, on the one hand, in terms of territorial barriers and a lack of favorable conditions and, on the other hand, in terms of conditions/features/performances that can determine successful cases [49]. The main constraints discussed are related to physical disadvantages as well as socio-economic, cultural, and institutional inadequacy that leads to considering them entrepreneurial laggards, with a low level of R&D due to the dominance of SMEs in traditional industries and weakly developed clusters, a lack of a critical mass to support the development of specialized services, and a lack of skills [49,76]. As the review of Baumgartner et al. [49] (p. 1215) underlines, the “distance from markets or limitations in financial or human resources may be a reason why entrepreneurship in non-core areas often does not lead to the high-risk and hence high-growth businesses with which entrepreneurship is often associated [157] but rather to other types of entrepreneurship such as, for example, social entrepreneurship”.

The debate is focused on identifying the features and performance of enterprises in peripheral contexts in order to be successful but also to be able to drive regional development [49]. Even in this field, the prevalence of case analysis provides an interesting overview of examples, but it does not allow for generalizations because of the wide diversity of territories considered peripheral, with different conditions and challenges to be faced. However, cooperation and networking emerge as effective compensation strategies for internal and external disadvantages and for mitigating inequalities in the territorial distribution of innovation. The role of networks in fostering innovation is emphasized by authors with respect to both territorial scale and stakeholders involved, as well as from an entrepreneurial ecosystem perspective, linking actors. At the same time, institutional change is highlighted as necessary to create a favorable environment for development and innovation.

5. Conclusions and Research Follow-Up

This paper contributes to setting the context for better understanding territorial inequalities and building a robust interpretation of strategies leading towards more equitable and balanced city-region relationships. The protocol enabled researchers to explore: (i) phenomena grouped under recurrent definitions referred to as territorial inequalities; (ii) causes embedded in these phenomena, overcoming the traditional spatial approach; (iii) development models applied in those contexts; and local resources playing the role of (iv) drivers for regeneration. The CNR-IRISS study confirms the complexity of the theme examined by scholars worldwide at different territorial scales of investigation (continental, national, regional, urban, local), in different geopolitical contexts, with a cross-disciplinary nature, and regarding both spatial and aspatial matters and tangible and intangible values [1,2,3,4,49,51].

The results of the exploration confirm the need for flexible, adaptable, complex, and place-sensitive planning approaches to be implemented at the regional level in order to include, within balancing processes, the different forms of marginal areas and central areas under pressure. Those entities of different natures act as communicating vessels, asking for a systemic approach able to reach a dynamic equilibrium and a more equitable development. In order to achieve the critical mass for activating regeneration processes without imposing models developed for central areas and/or highly specialized innovation contexts, a change in perspective is needed. Designing the planning process according to the peculiar conditions of non-central areas asks for a tailored set of approaches, models, and tools able to transform local characters into drivers for sustainable development. Network-based approaches guarantee relevant results in different contexts, offering the opportunity to reflect on the power of partnering among site-specific initiatives. This aspect is in line with trends regarding social innovation and civic engagement in promoting regeneration processes based on inclusive and environmentally awareness.

Consistent with the complexity of the topic and in order to strengthen the study, the researchers intend to: (i) implement the literature study by applying the SLR protocol in reference to both the new terms that emerged (see Section 3.1), which identify areas subject to inequalities, and terms referring to processes; (ii) deepen the study of innovation processes in areas subject to territorial inequalities, also using new interpretative categories different from those used for core areas; and (iii) activate a survey protocol to investigate and compare policies aimed at reducing territorial inequalities in different EU contexts. The latter requires a tailored methodology for collecting and addressing EU, National, and Regional policies and their impacts on the territorial system of interdependencies. This goal suggests combining the desk analysis of EU policies and their implementation at the national level with the consultation of key players and observers in European countries. To do so, a preliminary research protocol has been shared within the scientific network of the researchers in order to validate a survey protocol. The engagement process will start with the scientific networks already activated by the CNR-IRISS group and the institutions identified by this study, proceeding in a snowball manner.