Public policies on human rights to water in informal settlements: a bibliometric analysis

Informal settlements are a form of urban land use that, contrary to what would be desirable, continue to mark the landscape of many cities and metropolitan areas, especially in the Global South. As Gonçalves & Gama (2020) highlight, ‘Informal Urban Settlements (IUS) are, in a broad sense, the physical manifestation of the alternatives found by a vast and vulnerable population in response to the constraints on affordable housing supply’. This phenomenon is based on various factors such as the growth of the urban population due to the natural population growth and increasing migration, the deregulated market, property market speculation, and the high level of social asymmetries and political instability (Gonçalves & Gama, 2020). This picture is consensual, regarding the demand and supply of the housing market, and is a global research concern to identify triggers to avoid this type of urban settlement.

According to the United Nations (UN), in 2020 an estimated 13.8% of the global world population lived in such settlements, and 95.7% of them lived in Central and Southern Asia (38.4%), Eastern and Southeastern Asia (32.7%), and sub-Saharan Africa (24.6%) (United Nations, 2023). To broaden the scope of our research, the concepts of slums or slum-like, shantytowns, or squatter settlements were included in the IUS concept. That means this study encompasses densely populated urban areas characterized by substandard housing, poor infrastructure, and lack of basic services like clean water and sanitation (Programme, 2003).

From a policy perspective, the ‘human right to water’ is a fundamental principle recognized by the UN in 2010. It dictates that everyone has the right to sufficient, safe, accessible, and affordable water for personal and domestic uses. This includes water for drinking, personal sanitation, washing clothes, food preparation, and household hygiene, essentially all activities necessary for leading a healthy life.

While the right to water is universally recognized, it is far from universally realized, particularly in these IUS. Many residents in such areas lack access to clean water due to inadequate infrastructure, unregulated water pricing, or the marginalization of their communities. They often rely on informal water vendors who charge exorbitant rates, or on contaminated sources, risking their health (World Health Organization & United Nations Children's Fund (UNICEF), 2019). The Brazilian experience offers valuable lessons on the consequences of neglecting infrastructure in public policy formulation and the need for a human rights–centered approach to water accessibility (Guimarães et al., 2016). The lack of infrastructure exacerbates public health issues by increasing the incidence of waterborne diseases. These incidents can be mitigated with small investments in water supply and sanitation infrastructure (WSS), reducing the number of hospitalizations and, consequently, increasing productivity (Ferreira et al., 2021). Meanwhile, the reuse of treated wastewater presents a promising solution to alleviate water scarcity and enhance sustainability, and an integrated approach to water management in informal settlements is crucial (Rodrigues et al., 2024).

Global organizations like the UN and the World Bank promote participatory approaches including local communities in decision-making processes related to water access. This can be seen, for instance, in the World Bank's Water Supply, Sanitation, and Hygiene (WASH) program that aims to provide sustainable water and sanitation services to the poorest and most vulnerable groups (Andres et al., 2018).

While the human right to water in IUS is a complex issue, it can be significantly enriched through effective, inclusive public policies and active local and global collaboration. This complexity and the need for multidimensional solutions make crucial an exhaustive, multifaceted analysis of the existing literature on the subject. In this sense, in this study we want to answer the following two research questions: (1) What aspects are associated with the public policies on human rights to water in IUS? (2) How are the public policies on human rights to water in IUS related to the United Nations Sustainable Development Goals (SDGs)?

Due to the high disciplinarity and volume of studies in the field of public policies and/or human rights to water in IUS, a traditional literature review is not the most appropriate academic approach. Indeed, it is not possible to understand the overall scope of this research field within a set of chosen papers as the traditional literature review proposes. In contrast, we apply a holistic approach using two methods – bibliometric analysis (Zupic & Čater, 2015) and scientometrics (Chen, 2013). In addition, the literature presents the content analysis to promote an inductive approach to categorizing the themes within each cluster (Duriau et al., 2007; Mingers & Leydesdorff, 2015). Bibliometrics and scientometrics were the tools used to understand the insights from the academic literature, in a structured way, by analyzing key trends, influential authors and publications, mapping the intellectual structure of the field, and the interdisciplinary interactions as well as the evolution of the different academic fields of research analysis to promote new knowledge. The Bibliometrix R program was used to understand the evolution and trends, according to the different statistical data available using the biblioshiny() function. This function allowed us to analyze all the data in a web-based format, without the application of R software functions available in the R Studio Bibliometrix library (Aria & Cuccurullo, 2017).

The aim of this study was to find the insights to answer the research questions and is structured as follows: Section 2 describes the research methodology; Section 3 displays the materials and methods including the data collection, analysis, and data visualization; Section 4 presents the results and analysis, including annual scientific production; country scientific production; most influential sources; the research institutions; the collaboration analysis; and the most influential authors and words; Section 5 outlines the relevant findings using the keywords co-occurrence network and clustering, and the thematic map and evolution. The sixth section presents the main conclusions.

Bibliometrics is a technique in academic research that was first recommended by Otlet (1934) and recalled by Pritchard (1969). Alan Pritchard reinforced the bibliometrics terminology and techniques in 1969, despite the discussion on bibliometrics starting in the 1950s (Wallin, 2005). Pritchard proposed that bibliometrics could be used to study all aspects of scientific literature, from references in articles to the very language used in them, using statistical and mathematical methods.

Over time, bibliometrics has evolved to include more sophisticated techniques. One of these is bibliometric mapping, which shows the relationships between different pieces of academic work (Zupic & Čater, 2015). This helps understand the landscape of the study field. A bibliometric analysis starts with collecting relevant publications from research databases, like Scopus or Web of Science (WoS). These publications are then carefully processed to make sure the data are reliable (Waltman et al., 2010).

On the other hand, Nalimov & Mulchenko (1971) developed the concepts of scientometrics, defined as ‘the quantitative methods of the research on the development of science as an informational process’. The scientometric analysis uses mathematical models and algorithms in a way that gives the knowledge in visual statements, mapping, and clustering to enable a deeper understanding of the research fields (Mingers & Leydesdorff, 2015).

This study uses publications related to public policies on human rights of water in IUS, collected in the WoS platform, and the methodology used to construct this research study was based on the bibliometric workflow, using the R-package bibliometrix (Aria & Cuccurullo, 2017). This package includes a set of tools to elaborate quantitative research in bibliometrics.

According to the nature of this study, we have promoted a quantitative analysis using the collected data, from a timespan of 45 years. The first step was the definition of the keywords string related to our research scope. The combination used was ALL ((“public policies” OR “ governmental policies”) AND (“water”) AND (“informal settlements” OR “slums” OR “shanty towns” OR “informal housing” OR “squatter settlements”)).

Considering the evidence of Archambault et al. (2009), that ‘indicators of scientific production and citations at the country level are stable and largely independent of the database’, we have chosen the main research databases, Scopus and WoS to proceed with the search process.

The first experimental database search returned 2,292 documents from the Scopus database and 7 documents from the WoS platform, and this search included all the database fields.

For a refined search, we removed some non-interesting search content on the search fields of the Scopus database the second time. The restrictions are presented in the Appendix. Through this restricted search, we found 1,750 documents in the Scopus database. These were the experimental datasets of documents that we used for this bibliometric analysis and for setting up the Bibliometrix R Studio program (Aria & Cuccurullo, 2017).

The retrieved documents were saved in .bib format. All documents were merged, and duplicate documents were removed to construct a single file, using the R Studio version 4.3.0 commands, as presented in the Appendix. The final file uploaded to the Bibliometric analysis was converted to .xlsx format with 1,702 files, as presented in Table 1. The analyses of this study are based on citation topics, authors, publication years, document types, affiliations, publication titles, publishers, research areas, and countries.

Data visualization is the highest level of bibliometrics and scientometrics research, and the application of related techniques has been the subject of studies (Chen, 2013). This is the way to present the extracted data intuitively and according to statistical methods (Aria & Cuccurullo, 2017). In this layer, different techniques are used to represent the results.

The summary statistics of the database are included in Table 2. For a time span of 45 years, we have a total of 1,702 documents, with 36.57 citations per document on average, in 1,358 sources of information. Concerning authors and documents, the database had a total of 4,332 authors, 3,261 Keyword Plus, and an average of 36.57 citations per document. Regarding the type of documents, from a total of 1,702, 37.5 and 41.3% were articles and books, respectively.

This exponential increase in publications points out the high level of interest and research resources in studying the implementation of the SDGs, specifically regarding the Rio + 20 in June 2010, the agreements of the Sendai Framework in March 2015, the 2030 Agenda for Sustainability Development in September 2015, and the Paris Agreement in December 2015 (THE 17 GOALS | Sustainable Development, n.d.).

From the 1,358 sources of information, which includes all types of sources as described in Table 2, the 20 with the highest influence are presented in Table 3. We ranked the sources using the h-index (Egghe, 2006; Hirsch, 2010). This index provides a balance between productivity – the number of papers and impact – and the total number of citations (TC).

Considering this index, The Lancet was found to have a score of 9, with 7,467 TC and ranking in the first position. It was followed by the Current Opinion in Environmental Sustainability (6), Managing the Risks of Extreme Events and Disasters to Advance Climate Change Adaptation: Special report of the Intergovernmental Panel on Climate Change, and Annual Review of Sociology (4).

The country's scientific production for the timespan is presented in Table 4. The 10 most relevant contributors regarding scientific research in the field of this study are the United States (527), the United Kingdom (229), Australia (89), Canada (81), India (58), Brazil (41), South Africa (36), China (35), Germany (31), and the Netherlands (29).

Of the top 10 countries, 3 had internal problems with informal settlements and with the human rights of water. India, Brazil, and South Africa are not avoiding the problems; they are trying to provide solutions to this humanitarian problem, and they are top contributors to scientific production.

Combining the productivity and the cited countries, we infer that the United Kingdom, the United States, and Australia are the most impactful and relevant countries in this field of research. Within the same rationale, we verified that with less scientific production, the United Kingdom is the leading country in terms of the countries cited, which means a high relevance and impact of the scientific contribution of this country. This reasoning is also mainly valid for the Netherlands, Switzerland, Italy, and Spain.

Combining the word tree map and the trend topics, we can conclude that sustainable development, vulnerability, climate change, urban planning, and WSS are trending topics related to the public policies on human rights to water in IUS.

In this section of our study, a thematic analysis was performed. This section aims to understand the research landscape considering our study goals. We started with the keyword co-occurrence analysis and the clustering analysis, followed by the thematic map to understand the position of each topic concerning relevance and density, finishing with the thematic evolution.

The keyword co-occurrence network is a statistic expression and does not consider the temporality of the field of research. The frequency and centrality of which the keyword occurs reflect the co-occurrence of each keyword. These keywords are important for identifying the word clusters and connecting the major branches of knowledge.

The three main clusters are the blue, red, and purple ones, and they are interconnected. This reflects a relationship between the keywords of each cluster. Considering the blue community, the keyword climate change is the highest, regarding frequency, and the same relationship is evident in the red cluster with sustainability and water and sanitation in the purple cluster. Between clusters, it is observed that climate changes are highly connected with cities, sustainability with climate changes and water, as well governance with public policy and sanitation.

The remaining three clusters, the green, yellow, and brown ones, are constituted by four, and two nodes in the case of the brown one. Nonetheless, each of them has some relationship with the main clusters. The 50 keywords of the network and the corresponding distribution by clusters are given in Table 5.

In addition to the usage of the keywords co-occurrence network, more broadly, we enriched our knowledge about our research study using the thematic map (Cobo et al., 2011). With this science mapping technique, we display the main trend themes and the corresponding documents by themes. This approach seems more profitable to structure a content analysis. According to the most cited documents by theme presented in this research, some insights are presented, and they represent future research areas. Nevertheless, this research does not intend to present a content analysis of these documents.

The strategic diagram clarifies the state of the art, regarding the main research topics enabling us to infer that there is enough space to deeply research some of these topics, such as climate change, sustainability, poverty, and urbanization. To provide a deep understanding of the main insights in those research areas, we have chosen the then (10) most cited documents concerning climate change in Table 6, sustainability in Table 7, urbanization in Table 8, and urban poor in Table 9.

Concerning climate change, the analysis of the most cited documents highlights the necessity for adaptive planning approaches that can accommodate uncertainties and foster inclusivity. Urban agriculture emerges as a critical component for enhancing food security and urban resilience. However, further research is necessary to explore the feasibility and potential impacts of vertical or in situ farming within these contexts (Martellozzo et al., 2014). Furthermore, there is a pressing need to address the gendered dimensions of violence related to WASH services. This underscores the request for systematic studies to inform policy interventions (Sommer et al., 2015). Future research should integrate adaptive planning, socio-technical innovations, and gender-sensitive approaches to develop sustainable, resilient, and equitable urban environments. This should be supported in studies to assess long-term impacts (Sommer et al., 2015).

The reviewed documents provide valuable insights into the sustainability and adaptive planning of IUS. As Wyborn et al. (2019) emphasise, the concept of co-production has a significant role to play in the field of sustainability science. They advocate for a more profound engagement with public administration and the interdisciplinary field of science and technology studies in order to enhance the practical implementation of sustainability initiatives in informal settlements. They argue for a deliberate design of societal transitions, addressing critical weaknesses in power and governance structures that often marginalize these communities (Wyborn et al., 2019). Rauws & De Roo (2016) identified the necessity for informal settlements to develop a comprehensive understanding of their development trajectories, considering the dynamic and nonlinear nature of urban systems. Their work suggests a shift from predetermined urban configurations to enhancing the adaptability of informal settlements to their environments (Rauws & De Roo, 2016). Moreover, the papers discuss the intersection of energy transitions and social justice within informal settlements. In their examination of the integration of smart energy systems and renewable energy technologies in developing countries, Vanegas Cantarero (2020) emphasise the necessity for inclusive and equitable energy transitions that address energy poverty and promote democratic participation within informal settlements (Vanegas Cantarero, 2020).

Concerning the urbanization research pillar, the integration of complexities into IUS requires an interdisciplinary approach to fully address their challenges. Adaptable legal frameworks are essential to incorporate the realities of these settlements, enhancing stability and development (Pérez-Suárez & López-Menéndez, 2015). Health outcomes in informal settlements are significantly influenced by social capital, with strong community ties improving healthcare access (Meyer, 2018). Rapid urbanization and the expansion of informal settlements contribute to environmental degradation, demanding sustainable urban development policies (Pérez-Suárez & López-Menéndez, 2015). Informal settlements are particularly vulnerable to global environmental changes, highlighting the need for targeted resilience strategies (Lutz et al., 2017). Social capital within these communities can drive positive change, improving governance, economic opportunities, and social cohesion. Practical applications of social capital theories can address specific challenges faced by residents, leveraging different forms of social capital to improve living conditions and socioeconomic status (Bhandari & Yasunobu, 2009).

From the perspective of the urban poor theme, the potential and risks of digitalization, emphasizing the requirement for equitable access to digital resources to prevent digital exclusion among the urban poor are discussed. Research on credit utilization patterns recommends improving financial education and designing accessible credit schemes to alleviate poverty (Singh et al., 2023). Studies on land use dynamics have highlighted how policies often neglect informal settlements, leading to displacement and further marginalization. In response, there has been a call for inclusive planning that integrates these areas into urban development (Hirsh et al., 2020). Finally, the concept of urban ownership is examined, with the argument being made that the urban poor are often excluded from the benefits of urban development. The paper calls for the implementation of policies that recognize the rights of the urban poor in the city, emphasizing the importance of inclusive governance and equitable access to urban resources (Guimarães et al., 2016; Nahar Lata, 2021).

With the thematic evolution, we can understand the temporal trajectory and development of the key themes identified. Considering the scientific production presented in Figure 2, the total timespan of this research was divided into three periods, from 1978 to 2002, from 2003 to 2013, and from 2014 to 2023.

The field of healthcare emerged as a predominant research focus between 1978 and 2002. This emphasis transitioned seamlessly into human studies from 2003 to 2013, as well as from 2014 to 2023, indicating sustained research in human-related domains. The persistent significance of urban planning and the economic and social effects throughout these years underscores their foundational importance. These themes evolved into more specialized areas, such as land use planning and sustainable development, reflecting a natural progression and deepening of research in these fields. Areas of study that have a foundation dating back to 1978, such as health care, comparative studies, and urban planning, have provided the basis for numerous related topics in subsequent periods. For example, research on the economic and social effects has expanded to encompass governance approaches, public policy, and sustainable development, which emerged between 2003 and 2013.

The period from 2014 to 2023 is particularly notable for the emergence of climate change as a significant research area engaging interests from economic and social effects and governance. This shift highlights a clear reorientation of research priorities toward addressing global environmental challenges. The importance of climate change in recent research underscores its criticality and receives increasing attention from researchers.

To understand the evolution and state-of-the-art public policies on human rights to water in IUS, we used a holistic approach that includes a bibliometric literature analysis, between 1978 and 2023, and a scientometric analysis through the thematic evolution over the timespan, identifying the research hotspots and trends.

The research methodology was structured in three phases: stage 1 was related to the data collection and data extraction; stage 2 was associated with the bibliometric analysis; and stage 3 with the scientometric analysis.

From an initial database search with 2,299 documents, we finalized stage 1 of our research methodology with 1,702 documents of the overall types, but mainly articles and books with 78.8% of the literature extracted. The findings of the bibliometric analysis indicate that publications in these fields of knowledge have increased from 2002 to 2013, with an exponential escalation after 2013. We found that Sustainability (Switzerland), the Land Use Policy, and Water Policy are the main sources of publishing the research results. Furthermore, the United Kingdom, the Unites States, and Australia are the most influential countries concerning scientific production, and the three relevant research institutions are the University of California (USA), the University College of London (UK), and the Australian University of Monash. The most recent researchers in the fields of this study are Bartram J, Faust K, Marques R, Capon A, Ceschin F, Chirisa I, Islam M, Kammen D, and Matamanda A, and we concluded that the collaboration between authors can be improved.

The most frequent words used in the literature are sustainable development, climate changes, urban planning, and WSS, directly related to our first research question. Therefore, the sustainable development, climate change, urban planning, and WSS are the aspects related to the public policies on human rights to water in IUS research. In stage 3 of our study, the keyword co-occurrence network showed us that climate change is the highest, regarding frequency, and the same relationship is evident with sustainability, and water and sanitation. In addition, it is verified that climate change is highly connected with cities, and cities with informal settlements and the poor.

Consequently, to achieve effective public policies on human rights to water in IUS, it is essential that adaptive and inclusive planning is adopted to ensure equitable access to clean water for all residents. In addition, gender-sensitive approaches are crucial to addressing the specific challenges faced by women and girls, including gender-based violence related to inadequate WASH services. Moreover, engaging local communities in the planning and implementation of water services fosters co-production and addresses power and governance weaknesses. Significant investments in infrastructure, fair regulation of water pricing, and addressing socioeconomic marginalization are essential for bridging the water access gap. Furthermore, policies must ensure environmental sustainability and the adoption of innovative technologies to enhance water service access.

In this sense, to achieve the SDGs, these policies must focus on adaptive and inclusive planning, gender-sensitive approaches, and community engagement to ensure equitable access to clean water (SDG 6). Investing in infrastructure, regulating water pricing, and addressing socioeconomic marginalization also contribute to sustainable cities (SDG 11) and reduced inequalities (SDG 10). In addition, integrating environmentally sustainable practices and innovative technologies supports climate action (SDG 13) and clean energy (SDG 7). These comprehensive strategies enhance the resilience and well-being of IUS communities.

The contribution of this paper is manifold. First, it highlights the research pathway in this humanitarian and social inequity, presenting the evolution and the state of the art in scientific research. Second, the applied methodology can serve as a guide for the development of research involving extensive and varied literature supporting but not replacing the literature review phase. Concerning the context of each study, the explanations presented for our research goals can be applied to other research fields.

It is crucial to recognize that while bibliometric analysis is an effective method for summarizing and synthesizing literature, it is not without limitations. This bibliometric study utilized data from the scientific databases Scopus and WoS, which may have resulted in the exclusion of valuable literature from other sources, such as Google Scholar and PubMed. Moreover, the quantitative nature of bibliometric methodology frequently results in ambiguity concerning the relationship between quantitative and qualitative results.

PMR conceptualized the idea and methodology of the research presented; carried out the data collection, investigation, software, and analysis; and wrote the first draft of the article. JG supervised the research, reviewed, validated, and edited the first draft. RCM reviewed and validated the final draft. All authors contributed to subsequent drafts, which gave the manuscript its final form. All authors have read and agreed to the published version of the manuscript.

The authors are grateful for the Foundation for Science and Technology's support through funding UIDB/04625/2020 from the research unit CERIS.

All relevant data are included in the paper or its Supplementary Information.

The authors declare there is no conflict.