Environmental and Health Benefits: A Bibliometric and Knowledge Mapping Analysis of Research Progress

Abstract

Urbanisation poses significant challenges to urban ecosystems and public health. Urban blue–green spaces are integral to urban ecosystems and play a crucial role in enhancing public health through ecological and social pathways. This paper systematically reviewed research progress on the health benefits of urban blue–green infrastructure from 2014 to 2024, using CiteSpace. By analysing 2346 publications, it revealed the development history and emerging trends in the field. Over the past decade, relevant publications have increased, with two major research groups dominated by China and Western countries but with less cooperation. This lack of collaboration may restrict diverse population inclusion, reduce research generalizability, and hinder bridging policy and cultural gaps. Findings focused on “Ecosystem services”, “physical activity”, and “residential green areas” and also highlighted a shift in research focus from foundational theories to investigating the health mechanisms of blue–green spaces, issues of environmental justice, and the impact of exposure levels on well-being. However, the synergistic effects of blue–green spaces and environmental justice issues require further investigation. Future research should prioritise interdisciplinary and international collaboration, advancing policies and applications to integrate blue–green spaces into health promotion and sustainable urban planning.

1. Introduction

Cities serve as primary spaces for human life, work, and leisure, and are critical environments for population health, cultural development, and social organisation in the 21st century [1]. However, urbanisation, a globally intensifying phenomenon, poses significant challenges to the physical and mental health of urban residents [2,3]. According to the 2014 Revision of the World Urbanisation Prospects Report released by the United Nations, the global urban population has grown significantly from 746 million to 3.9 billion since 1950, and projections suggest that this number will increase by more than two-thirds by 2050 [4]. Although urbanisation offers notable benefits in terms of improving healthcare, infrastructure, education, and employment opportunities [3], its negative effects cannot be overlooked. These include heightened disease transmission [5], increased urban flooding [6], deteriorated air quality [7], intensified urban heat island effects [8], and elevated noise pollution [9]. Moreover, urbanisation often leads to a reduction in blue–green spaces, limiting residents’ opportunities to interact with urban natural environments and posing serious threats to their physical and mental well-being [10].

The concept of ecosystem services provides a valuable theoretical framework for understanding how urban blue–green spaces contribute to health and well-being. According to the 2005 Millennium Ecosystem Assessment, ecosystem services refer to the benefits that humans can derive from natural ecosystems. These include provisioning service (e.g., food and water), regulating service (e.g., climate regulation and air quality improvement), cultural services (e.g., recreation and aesthetic value), and supporting service (e.g., biodiversity maintenance) [11]. Marcello et al. pointed out that human well-being depends on the ecosystem services provided by the Earth’s natural ecosystems and resource stocks. [12] As a vital component of urban ecosystems and a key element blending nature with cities, blue–green spaces can offer various ecosystem services that directly or indirectly impact residents’ physical and mental health. Consequently, they have gradually become the focus of research in the fields of urban planning and public health [13].

Urban blue–green spaces, a combination of water bodies (blue spaces) and green vegetation (green spaces) in a city, are vital components of sustainable urban planning and urban ecosystem [14]. Extensive studies have defined the types of urban blue–green space at the macro and micro levels: at the macro level, they include water, forests, coastal zones, farmland, parks, and other wide-area ecological areas; at the micro level, they cover smaller vegetation spaces, such as urban parks, courtyards, urban forests, and farms [15,16,17,18,19]. At present, the health-promoting effects of blue–green spaces have received extensive international attention, and a large number of studies have confirmed the benefits of blue–green spaces on urban community residents, such as lowering blood pressure, reducing obesity, enhancing psychological resilience, alleviating social isolation, and improving social cohesion [18,19,20,21]. Green spaces have always been a central focus of health-related research. The health-promoting effects of urban green spaces have been widely recognised from early comparative studies on the restoration benefits of natural and urban environments (such as forests and urban spaces) [22] to the recent exploration of the correlation between urban green spaces and population health [23]. Moreover, many studies have attempted to reveal the mechanism by which urban green spaces exert health benefits from different perspectives. Du and Li identified green exposure as an evaluation indicator of health services and investigated its mechanisms for promoting well-being [24]. Other researchers have proposed that urban green spaces stimulate multiple human senses, foster positive perceptions of the external world, and promote relaxation [25]. Furthermore, studies have shown that green spaces provide important places for outdoor activities and social interactions, not only enhancing residents’ physical health but also improving life satisfaction and social cohesion by promoting neighbourhood interaction [26]. Compared to green spaces, blue spaces have received less attention in environmental health research. However, recent epidemiological studies indicate that blue spaces are a growing focus of this field [27]. Blue spaces can significantly improve residents’ physical fitness by increasing the frequency, intensity, and diversity of physical activity [28,29,30,31]. Numerous reports have confirmed that the availability or visibility of blue spaces has a positive impact on alleviating emotional disorders such as anxiety [32,33,34,35]. A review by Georgiou et al. highlighted that blue spaces contribute to human health by influencing environmental factors, such as reducing heat stress and surface temperatures, improving PM2.5 concentrations, enhancing air quality, and boosting subjective perceptions of regional ecological quality [27]. Furthermore, in terms of the synergistic effects of blue–green spaces, Markevych et al. combined objective measurements and perceived evaluations of green and blue spaces to explore and reveal multiple mechanisms and interactions linking blue–green spaces with public health [36].

However, the current research perspective about health benefits of urban blue–green spaces is still relatively narrow, mainly focusing on green spaces [15]. Most studies consider blue space an inherent component of areas close to the natural environment within cities, such as parks, ignoring the unique function of blue space and its synergistic effect with green space [37,38]. In addition, owing to the compound influence of leading factors, such as socioeconomic status and medical resource distribution, the complexity of the causal correlation between blue–green spaces and residents’ health is often underestimated. At the same time, as a giant system with an extremely complex structure and function, research on the health benefits of urban blue–green spaces must continue to explore and deepen the key elements and paths of health intervention from an interdisciplinary and multi-objective perspective. Existing research methods in this field mainly involve qualitative analyses, lacking systematic bibliometric analyses and knowledge mapping techniques [39], which limits the comprehensive cognition of research dynamics and the evolution of hotspots. In contrast, bibliometric analyses are an objective and quantitative research tool that can be used to analyse collaboration networks, co-citation relationships, and burst words, as well as other aspects, through knowledge mapping. In recent years, bibliometric analysis has become a widely adopted approach in health-related scientific research. Given the multidisciplinary nature of urban health and sustainability, bibliometric methods are particularly valuable in identifying collaboration patterns across disciplines, tracking the evolution of research hotspots, and forecasting future research directions [40]. By offering data-driven insights, bibliometric analysis supports both the academic community and policymakers in making informed decisions.

Therefore, employing bibliometric methods to systematically review research progress on the health benefits of blue–green spaces, identify research hotspots and emerging directions, and explore their roles and mechanisms in addressing global challenges such as climate change and urbanisation holds significant theoretical and practical value. This paper is a bibliometric review, focusing on the research progress of urban blue–green spaces on health, aiming to analyse the research trends, annual growth rates of publications, and main contributors in the field of urban green–blue spaces and public health over the past decade (2014–2024), determine the research hotspots, and focus on the thematic areas such as ecosystem services, physical and mental health, environmental justice, and the synergy effects of green–blue spaces. It attempted to use CiteSpace 6.4.R1 to construct relevant knowledge maps and collaboration networks, conduct a comprehensive qualitative and quantitative analysis of the research status of the health-promoting effects of urban blue–green spaces, parse research hotspots and trends, and compensate for the methodological deficiencies and incomplete perspectives in existing research. Through multidimensional analysis, a more comprehensive knowledge system was constructed. The research results may provide scientific references for scholars to deeply understand the current research status and future directions in this field and offer important support for policymakers and practitioners, promoting the practical application of blue and green spaces in health promotion within urban areas.

2. Materials and Methods

2.1. Data Sources

Data for this study were collected from the Web of Science (WoS) and Scopus databases, and the search was conducted on 18 December 2024. Keyword integration was carried out on the basis of the three studies of S.M. Labib [41], Wenfei Yao [42], and Rebecca M. Collins [43]. At the same time, we use OR concatenation for words within the same subject to ensure that only one of the terms matches can be searched, a strategy that reduces the impact of the sensitivity and specificity of search terms on search results and helps us to minimise missing relevant studies. Through literature retrieval, research on the health benefits of urban blue–green spaces began to show significant growth in 2014; therefore, the study focused on the literature published over the past decade (January 2014 to December 2024). By using search terms such as “urban green space”, “urban blue space”, “people”, and “health” (see Appendix A for the complete search string), a total of 15,583 publications were initially obtained. Synonyms for green space are as follows: urban green space, urban green infrastructure, neighbourhood greenness, urban tree, urban greenway, urban forest, urban greenery, residential green, urban park, garden. Synonyms for blue space are as follows: urban blue, urban lake, urban river, urban coastal, urban beach, urban seaside. Conference papers, conference reviews, data papers, editorials, errata, letters, and short surveys were excluded, retaining articles and reviews. To address irrelevant topics and duplicate records across databases, titles and abstracts were manually screened using EndNote and NoteExpress, reducing the dataset to 2350 publications. Finally, after removing duplicates from CiteSpace 6.4.R1, 2346 unique publications were selected as the final sample for analysis (due to the limitations of the CiteSpace software, 3.3 Analysis of Contribution of Institutions, as well as the subsequent 3.4 Analysis of Contribution of Countries and 3.5.1 Co-citation Analysis of Publications, are based only on the literature retrieved from the WoS database). Subsequently, these publications were used to explore the multidimensional health benefits of urban blue–green spaces and to identify current research frontiers.

2.2. Data Analysis Methods

Bibliometric analysis applies mathematical and statistical techniques to quantitatively assess the literature within a specific field; explore the respective connections of elements such as authors, institutions, countries, keywords, and co-citations; and visualise trends and research dynamics [44,45,46]. CiteSpace, a Java-based tool developed by Professor Chaomei Chen, is widely used to analyse and visualise trends and patterns in the literature. The results of these visualisations are known as scientific knowledge maps [47,48]. Despite the vast number and variety of studies based on bibliometric analysis methods, few have simultaneously focused on the health benefits of urban green spaces and the impact of urban blue spaces on physical and mental health. Therefore, this study used CiteSpace 6.4.R1 as the primary tool for bibliometric methods to conduct data mining and visualisation analysis of the health benefits of urban blue–green spaces, aiming to reveal the current research status, determine the overall trend, highlight recent progress, and provide guidance for future research directions.

This study aimed to explore connections among research outputs on urban blue–green spaces and human health from 2014 to 2024 and to attempt a comprehensive analysis of the field’s development trajectory and current status. First, publication counts over the decade obtained after removing duplicates in CiteSpace 6.4.R1 were imported into Excel for trend visualisation. Subsequently, CiteSpace 6.4.R1 was used for author collaboration network, institution contribution, and country contribution analyses. Finally, co-citation, keyword co-occurrence, clustering, timeline, and burst analyses were conducted using the same software to identify research hotspots and emerging trends in the health effects of urban blue–green spaces. Figure 1 illustrates the research framework.

The basic settings of this study include a time span set from January 2014 to December 2024, with time slice set to one year. The analysis network was constructed using the “pruning sliced networks” approach, while default settings were applied for other parameters. In the author collaborative network analysis, the threshold value was set to 8, with nodes having fewer than four publications hidden. The top 11 authors based on publication volume were listed. In the Analysis of the Contribution of Institutions, the threshold value was set to 30, with nodes having fewer than 16 publications hidden. The top 10 institutions based on publication volume were listed. In the Analysis of the Contribution of Countries, the threshold value was set to 2, and 16 countries with more than 100 publications were listed. In the Co-citation Analysis of Publications, the threshold value was set to 30, with nodes having a co-citation frequency lower than 30 hidden. Publications with betweenness centrality higher than 0.01 and among the top 20 in co-citation frequency were listed. In the keyword co-occurrence analysis, the threshold value was set to 30, with nodes having an occurrence frequency lower than 30 hidden. The top 13 keywords based on occurrence frequency were listed. In the Keyword Cluster Analysis, the clustering algorithm used was the log-likelihood ratio (LLR). In the keyword timeline analysis, the Max Number of Node Labels per Year was set to 1. In the burst word analysis, the top 25 keywords with the strongest burst intensity were listed.

3. Results

3.1. Overall Trend of Publications

From 2014 to 2024, 2346 publications on the health-promoting effects of urban blue–green spaces were analysed, including primary articles and reviews. Annual publication trends reflect the theoretical advancement and growth rates in this field. As shown in Figure 2, fewer papers were published between 2014 and 2016, and the number of papers steadily increased. Notably, there has been a significant increase since 2019, with 413 articles peaking in 2024. Although the number of publications in 2023 was slightly lower than those in 2022 and 2024, the overall trend over the decade showed a steady upward trend (index trend line R² = 0.9451), underscoring the growing scholarly interest and rapid development in this research area.

3.2. Author Collaborative Network Analysis

By employing CiteSpace 6.4.R1 to conduct an analysis of author collaborations, this study identified key contributors. The collaborative network consisted of 440 nodes and 745 links (Figure 3). To enhance the clarity of the analysis, the threshold value was set to eight, and nodes representing authors with only one to three publications were excluded. As shown in Figure 3 and

Table 1. Eleven authors of the highest number of publications on the health-promoting effects of urban blue–green spaces.

Sequence Number	Number of Publication	Centrality	Year	Author
1	28	0.07	2019	Liu, Y
2	22	0.04	2019	Dadvand, P
3	22	0.05	2020	Li, X
4	18	0.06	2016	James, P
5	18	0.1	2018	Nieuwenhuijsen, M
6	18	0.06	2019	P, White M
7	17	0.04	2014	Astell-burt, T
8	15	0.1	2019	Lu, Y
9	14	0.03	2020	Chen, Y
10	14	0.01	2022	Wang, Y
11	14	0.05	2014	J, Nieuwenhuijsen M

, 11 prolific authors emerged as prominent nodes in the network, Liu, Ye (Sun Yat-Sen University), Dadvand, P. (ISGlobal), Li, Xi (Sichuan Agricultural University), James, P. (The University of Manchester), Nieuwenhuijsen, M. (ISGlobal), White, P.M. (University of Exeter), Astell-Burt, T. (University of Western Sydney), Lu, Yi (City University of Hong Kong), Chen, Ye (Southeast University), Wang, Yuan (University of Helsinki), and Mark J. Nieuwenhuijsen (ISGlobal), reflecting their outstanding contributions to the research on the health promotion effects of urban blue and green spaces between 2014 and 2024. However, the links between nodes revealed that there were two distinct collaboration groups: one centred in China and the other comprising researchers from other countries; however, the level of collaboration between these two groups remained limited. In addition, node centrality, which measures the number of shortest paths passing through a node within the overall network, provides an indicator of a node’s influence and connectivity within a collaboration network [49]. In the Chinese collaborative group, Lu and Yi (City University of Hong Kong, centrality = 0.10) and Wang and Siqiang (Hong Kong Polytechnic University, centrality = 0.10) exhibited purple outer rings, signifying high betweenness centrality, indicating their substantial influence and importance within the network. The international collaborative group Nieuwenhuijsen (ISGlobal, centrality = 0.10) also featured a purple outer ring, highlighting its role as a critical bridge linking various author communities.

3.3. An Analysis of the Contribution of Institutions

An institutional contribution knowledge map was generated by adjusting the node type settings in CiteSpace. The network consisted of 410 nodes and 2126 links (Figure 4), but for a clear presentation of the analysis results, the threshold value was adjusted to 30, and the nodes with fewer than 16 publications were hidden. Figure 4 and

Table 2. Ten institutions of the highest number of publications on the health-promoting effects of urban blue–green spaces.

Sequence Number	Number of Publication	Centrality	Year	Institute
1	155	0.23	2014	Chinese Academy of Sciences
2	96	0.21	2014	University of California System
3	86	0.07	2014	United States Department of Agriculture (USDA)
4	70	0.06	2014	United States Forest Service
5	69	0.03	2014	University of Chinese Academy of Sciences
6	54	0.06	2015	Helmholtz Association
7	53	0.06	2014	University of Exeter
8	52	0.04	2014	CIBER—Centro de Investigacion Biomedica en Red
9	52	0.03	2014	University of London
10	51	0.04	2016	University of Hong Kong

show that research on the health benefits of urban blue and green spaces was primarily conducted by research institutions and universities. Among them, the Chinese Academy of Sciences stood out as the largest node and the most prolific institution, with 155 publications. The University of California System closely followed with 96 publications, while the United States Department of Agriculture (USDA) ranked third with 86 publications. This highlights the significant research capacities of these three institutions in this field.

In terms of interagency cooperation, there was a high level of collaboration among different research institutions, and nodes representing the Chinese Academy of Sciences (centrality = 0.23), University of California System (centrality = 0.21), and University of British Columbia (centrality = 0.12) showed significant intermediate centrality. This indicates a strong sense of collaboration among institutions and high mobility of research results, as well as the outstanding academic influence of the above three research institutions in the field. Further analysis of node colour revealed that most institutions began publishing papers in this domain after 2018, indicating that the health benefits of blue–green spaces in cities have received increasing attention in recent years, and the importance and research efforts in this field have significantly increased.

3.4. An Analysis of the Contribution of Countries

First, country names were standardised by merging similar entries into unified categories (e.g., “PEOPLES R CHINA” and “TAIWAN” were standardised as “CHINA”, while “ENGLAND”, “SCOTLAND”, “WALES”, and “NORTH IRELAND” were consolidated as “UK”). Subsequently, by adjusting the node type in CiteSpace, a country contribution knowledge map was generated. This map comprised 130 nodes and 1000 links, with an overall network density of 0.1193 (Figure 5). Sixteen countries with more than 100 publications are listed (

Table 3. Sixteen countries with the number of publications above 100 on the health-promoting effects of urban blue–green spaces.

Sequence Number	Number of Publication	Centrality	Year	Country
1	1085	0.08	2014	China
2	948	0.34	2014	USA
3	515	0.18	2014	UK
4	307	0.18	2014	Australia
5	256	0.12	2014	Germany
6	207	0.12	2014	Italy
7	193	0.05	2014	Canada
8	183	0.09	2014	Spain
9	128	0.03	2014	Japan
10	124	0.01	2014	Poland
11	121	0.09	2014	France
12	121	0.05	2014	The Netherlands
13	120	0.03	2014	Brazil
14	111	0.07	2014	Sweden
15	109	0.08	2014	Belgium
16	107	0.05	2014	India

).

According to Figure 5 and Table 3, in terms of publication volume, CHINA, the USA, and the UK ranked as the top three contributors with 1085, 948, and 515 publications, respectively. Furthermore, the USA (centrality = 0.34), UK (centrality = 0.18), AUSTRALIA (centrality = 0.18), GERMANY (centrality = 0.12), and ITALY (centrality = 0.12) exhibited high centrality in the network structure, indicating their significant contributions to research on the health benefits of urban blue and green spaces from 2014 to 2024. Notably, the USA was the most prominent contributor, highlighting its overall research strength in this field.

However, research on urban blue–green spaces and public health has been predominantly concentrated in high-income countries (e.g., USA, UK, Germany, and Australia) and middle-to-high-income countries with high research output (e.g., China). In contrast, low-income and lower-middle-income countries—particularly those in Africa, Latin America, and South Asia—are underrepresented in the literature. Among countries with more than 100 published papers, only a few middle-to-lower-income nations (e.g., Brazil and India) are represented, yet their central position within the global research network remains relatively low. This regional disparity suggests that much of the existing knowledge on this field has been shaped by the perspectives, urban planning approaches, and policy frameworks of high-income countries. The limited research from lower-income countries may lead to gaps in understanding how blue–green spaces function across different socioeconomic, climatic, and policy contexts. Future research should prioritise greater inclusion of studies from Africa, Latin America, and South Asia to ensure a more comprehensive understanding of the global health impacts of blue–green spaces.

3.5. Analysis of Hotspots and Trends

3.5.1. Co-Citation Analysis of Publications

To further identify the core literature on urban blue–green spaces and health research and reveal the research focus, and because of the limitations of the CiteSpace software, this study used CiteSpace 6.4.R1 to conduct a co-citation analysis only on the literature retrieved from WoS. A total of 894 co-cited documents were identified, and their citation frequencies and centralities were analysed. To present the results clearly, the threshold value was set to 30, and nodes with citation frequencies below 30 were hidden (Figure 6). In addition, publications with a centrality of more than 0.01 were selected and ranked by citation frequency, and the previous 20 core publications were used as the starting point (

Table 4. Core literature on urban blue–green spaces and health.

Freq	Centrality	Label	Name	Research Content	Research Method
152	0.07	Markevych I (2017)	Exploring pathways linking greenspace to health: Theoretical and methodological guidance [50]	Evaluates the impact of green and blue spaces on mental health.	Theoretical and methodological guidance
93	0.08	Hartig T (2014)	Nature and Health [51]	Explores how reduced human–nature interaction due to urbanisation affects health.	Literature review, conceptual model, and method summary
91	0.01	Twohig-Bennett C (2018)	The health benefits of the great outdoors: A systematic review and meta-analysis of greenspace exposure and health outcomes [52]	Quantify evidence of the impact of greenspace on a wide range of health outcomes.	Literature review
85	0.12	Bratman GN (2019)	Nature and mental health: An ecosystem service perspective [53]	Nature experience and mental health.	Conceptual model and hypothetical application
79	0.01	Kondo MC (2018)	Urban green space and its impact on human health [54]	Assess the possibility of causal relationships between nature and health in urban settings.	Literature review
75	0.01	Venter ZS (2020)	Urban nature in a time of crisis: recreational use of green space increases during the COVID-19 outbreak in Oslo, Norway [55]	Explore how social distancing measures affected recreational use of urban green space during the partial lockdown in Oslo, Norway.	STRAVA and Google mobility data with geospatial analysis
72	0.02	Wolch JR (2014)	Urban green space, public health, and environmental justice: The challenge of making cities “just green enough” [56]	The importance of urban green space for public health.	Literature review and case studies
67	0.04	van den Bosch M (2017)	Urban natural environments as nature-based solutions for improved public health–A systematic review of reviews [57]	Evaluate the evidence on public health benefits of exposure to natural environments and explore how this knowledge could be framed within the NBS concept.	Literature review
65	0.06	Ekkel ED (2017)	Nearby green space and human health: Evaluating accessibility metrics [58]	Emphasis was placed on evaluating the types of existing green space accessibility indicators and their applicability to health impact studies.	Literature review and related empirical research
60	0.02	Gascon M (2016)	Residential green spaces and mortality: A systematic review [59]	Systematically review the available evidence on the association between long-term exposure to residential green and blue spaces and mortality in adults and make recommendations for further research.	Literature review following PRISMA protocol and meta-analysis
59	0.07	Frumkin H (2017)	Nature contact and human health: A research agenda [60]	Propose a research agenda on nature contact and health, identifying principal domains of research and key questions.	Literature review and research agenda
58	0.02	Gascon M (2015)	Mental health benefits of long-term exposure to residential green and blue spaces: a systematic review [61]	The health benefits of residential green and blue spaces.	Literature review and meta-analysis.
55	0.03	Gascon M (2018)	Long-term exposure to residential green and blue spaces and anxiety and depression in adults: A cross-sectional study [62]	Evaluate the effects of long-term exposure to residential green and blue spaces on anxiety and depression and intake of related medication and explore potential mediators and effect modifiers of this association.	Questionnaires and logistic regression models
51	0.01	Geng DH (2021)	Impacts of COVID-19 pandemic on urban park visitation: a global analysis [63]	Analyse the impacts of COVID-19 and government response policies to the pandemic on park visitation at global, regional, and national levels and assess the importance of parks during this global pandemic.	Correlation analysis, ANOVA analysis, and stepwise regression analysis
51	0.04	Nesbitt L (2019)	Who has access to urban vegetation? A spatial analysis of distributional green equity in 10 US cities [64]	A spatial analysis of distributional green equity in 10 US cities.	Spearman’s correlations and spatial auto-regressive models
49	0.03	Jennings V (2019)	The relationship between social cohesion and urban green space: An avenue for health promotion [65]	Discuss how positive interactions in urban green space can catalyse social cohesion, social capital, and critical health-promoting behaviours that may enhance psychological health and well-being, summarise the strengths and limitations of previous studies, and suggest directions for future research.	Literature review, conceptual model, and method summary
49	0.04	Helbich M (2019)	Using deep learning to examine street view green and blue spaces and their associations with geriatric depression in Beijing, China [66]	Compare street view indicators from street view images with street view indicators from satellites assessing green and blue spaces and examine the relationship between green and blue space exposure and depression in older adults in Beijing, China.	Questionnaires and multilevel regressions models
49	0.04	Fong KC (2018)	A review of epidemiologic studies on greenness and health: updated literature through 2017 [67]	Summarise the latest research in the field of health benefits of natural vegetation and green environments.	Literature review
46	0.03	Labib SM (2020)	Spatial dimensions of the influence of urban green-blue spaces on human health: A systematic review [41]	Learn how spatial scales, datasets, methods, and analyses are currently applied to research investigating the relationship between green and blue spaces and human health in urban areas.	Literature review following PRISMA protocol
43	0.01	Livesley SJ (2016)	The urban forest and ecosystem services: impacts on urban water, heat, and pollution cycles at the tree, street, and city scale [68]	The role of urban trees in urban biogeochemical cycles.	Literature review

) to summarise the research content.

Centrality is a critical metric for measuring the importance and influence of the literature within a co-citation network. The literature with higher centrality represents the main knowledge base in the research field. Based on Figure 6 and Table 4, “Bratman, Nature, and Mental Health: An ecosystem service perspective” by Gregory et al. (centrality = 0.12) had the highest intermediate centrality, indicating that it is a cornerstone of research in this field. Moreover, through this analysis, three research emphases in this field can be drawn, including exposure assessment—the spatial differentiation of exposure levels and environmental justice from a multiscale perspective, mechanism exploration—multiple pathways of action and synergistic effects of urban blue–green space on public health, and law disclosure—the dose–response relationship between exposure levels and health promotion effects.

3.5.2. Keyword Analysis

Keyword Co-Occurrence Analysis

Keywords are concise extractions and summaries of the literature content, directly reflecting the core themes and main topics of the literature. By constructing a keyword co-occurrence network, the co-occurrence frequency and association patterns of keywords can be analysed, thereby uncovering key issues and developmental trends in research on the health effects of urban blue–green spaces. Figure 7 shows the results of the keyword co-occurrence analysis with the time slice set to one year, from 2014 to 2024. There were 484 nodes and 2901 links with a density of D = 0.0248. However, to present the results clearly, the threshold value was adjusted to 30 and nodes with frequencies below 30 over the ten years were hidden. According to Figure 7 and

Table 5. Thirteen keywords that appear most frequently on the health-promoting effects of urban blue–green spaces.

Sequence Number	Number	Centrality	Year	Keyword
1	275	0.02	2014	green space
2	263	0.05	2014	mental health
3	226	0.01	2014	urban green space
4	216	0.01	2014	ecosystem services
5	209	0.05	2015	recreational park
6	198	0.06	2014	urban area
7	177	0.01	2014	public health
8	167	0.05	2014	physical activity
9	142	0.01	2014	green spaces
10	137	0.04	2015	urban planning
11	135	0.03	2014	human health
12	114	0.03	2014	urban green spaces
13	109	0.01	2015	environmental justice

, “green space”, “mental health”, “urban green space”, “ecosystem services”, “recreational park”, “urban area”, “public health”, “physical activity”, “green spaces”, “urban planning”, “human health”, “urban green spaces”, and “environmental justice” appeared more frequently, forming prominent nodes within the network. The research topics of these high frequency keywords ranged from 2014 to 2024. Further analysis shows that these 13 keywords can be roughly categorised into three groups: one focuses on urban space and planning, especially the design and function of green spaces; the other is concerned with human physical and mental health; and the third is closely related to environmental justice issues. These three aspects constitute the focus of the present study. Additionally, as shown in Figure 7, although blue spaces (e.g., number of “blue spaces” = 55; number of “blue spaces” = 46) received some attention, their research prominence was notably lower than that of green spaces. The research subjects in this field encompassed middle aged groups (number of “middle aged” = 81), young adults (number of “young adults” = 60), and older adults (number of “older adults” = 44), but studies on older adults and children were relatively less prevalent. Meanwhile, issues such as climate change and pollution (number of “air pollution” = 51; number of “particulate matter” = 35; number of “climate change” = 35), environmental exposure (number of “environmental exposure” = 57; number of “long-term exposure” = 45), and pandemics (number of “coronavirus disease 2019” = 33) also emerged as key areas of focus in this research domain.

Keyword Cluster Analysis

By employing the log-likelihood ratio (LLR) clustering algorithm in CiteSpace, cluster analysis was conducted on all keywords to further explore the promoting effect of urban blue–green spaces on human health (Figure 8). A cluster map of keywords indicates different research concerns in this field [69]. Using the g index (k = 25) as the selection criterion, the resulting network had a modularity of 0.37 and an average profile score of 0.500. The network contained nine clusters from 2346 studies, with clusters numbered by size. The largest cluster, designated as #0, is labelled “ecosystem services”, and the label sequence numbers from smallest to largest are as follows: #0 ecosystem services, #1 physical-activity, #2 residential green, #3 climate change, #4 human health, #5 benefits, #6 quality of life, #7 subjective well-being, and #8 tree cover. In addition to links within clusters, there are also links among different clusters, especially cross-cluster connections among #0 ecosystem, #1 physical-activity, #3 climate change, and #5 benefits. This indicates that the degree of co-citation among these research directions was high.

By further analysing the keywords included in cluster #0 from

Table 6. The specific content of nine clusters of relevant keywords on the health-promoting effects of urban blue–green spaces. Due to the large number of keywords, for clear presentation, the table only shows keywords with a frequency above 10.

Cluster ID	Size	Silhouette	Mean Year	Keywords (freq > 10)
0	90	0.746	2018	green spaces, land use, middle aged, environmental exposure, air pollution, environmental factor, psychological well-being, regression analysis, particulate matter, atmospheric pollution, social status, health risk, cardiovascular disease, neighborhood greenness, risk factor, environmental health, normalized difference vegetation index, self report, risk assessment, air pollutant, household income, socioeconomic status, structural equation modeling, sensitivity analysis, blood pressure, environmental parameters, traffic noise, child health, residential location
1	66	0.737	2018	recreational park, older adults, health status, horticultural therapy, coronavirus disease 2019, population density, very elderly, 80 and over, social interaction, mental stress, social behavior, physiological stress, decision making, prospective study, park design, young population
2	63	0.781	2018	green space, built environment, residential green, blue spaces, blue space, long-term exposure, natural environments, cultural ecosystem services, urban green, urban forest, outdoor recreation, therapeutic landscapes, residential greeness, social environment, social support, healing garden, nature connectedness, natural environment, body-mass index, urban green-space, landscape planning, depressive symptoms
3	60	0.691	2020	health impact, city planning, health promotion, climate change, spatial analysis, nature-based solutions, urban development, urban greenery, urban green infrastructure, air quality, social media, public space, urban greening, urban heat island, deep learning
4	58	0.744	2017	urban green space, ecosystem services, human health, environmental justice, urban parks, green infrastructure, urban park, urban greenspace, urban forestry, urban ecosystem, ecosystem service, urban forests, stress recovery, health benefits, psychological restoration, human well-being, forest therapy
5	56	0.824	2016	mental health, urban area, public health, physical activity, urban planning, urban green spaces, residence characteristics, urban population, human experiment, young adult, urban health, environmental planning, environmental design, urban design, remote sensing, socioeconomic factors, body mass, statistics and numerical data, health survey, social cohesion, machine learning
6	35	0.849	2020	quality of life, life satisfaction, health care, thermal comfort, physical health
7	21	0.889	2020	subjective well-being, qualitative analysis, public parks, natural experiment
8	7	0.948	2022	mediation analysis, tree cover, mental disorder

, ecosystem services emerged as the primary focus of this research field because they integrate the relationships among the ecological environment (e.g., environmental exposure, air pollution, air pollutants, particulate matter, atmospheric pollution, traffic noise, green spaces, neighbourhood greenness, normalised difference vegetation index), socioeconomic factors (e.g., social status, household income, residential location), and public health (e.g., psychological well-being, cardiovascular disease, blood pressure, risk factor, child health, health risk). It also provided a scientific basis and evaluation method for how urban blue and green spaces affect human health in various ways (regression analysis, structural equation modelling, sensitivity analysis, risk assessment, self-reporting, and environmental parameters). According to a number of studies combined with Table 6, physical activity could become the second most important concern in this field, mainly because aesthetically attractive environments are more likely to attract people to participate in physical activities, such as cycling and walking [70]. Moreover, research proved that physical activity is one of the direct paths through which blue–green spaces promote human physical and mental health [71,72]. The third cluster (cluster #2) was “residential green”, which can become a hot spot in this research field because green space in residential areas is not only an important way for people to get in touch with nature [73] but also directly affects mental health [61], physical health [74,75,76,77], and the quality of social interaction [78].

Keyword Timeline Analysis

To further explore the temporal evolution of research priorities on the health-promoting effects of urban blue–green spaces between 2014 and 2024, this study analysed the distribution of keywords within the nine clusters based on their first appearance years. Within each cluster, the evolutionary trajectory of the keywords was visualised along a timeline according to their year of occurrence (Figure 9). This method facilitates the depiction of dynamic developments within clusters and highlights the changes in the significance of keywords over time, thereby providing a foundation for identifying research hotspots and trends [79]. As shown in Figure 9, since 2014, researchers have been actively conducting studies related to “ecosystem services”, “physical-activity”, “residential green”, “climate change”, “human health”, and “benefits”. Particularly, keywords related to green spaces (such as “green spaces” in #0, “recreational park” in #1, “green space” in #2, “urban green space” in #4) and health (such as “health status” in #1, “mental health” in #5) have high frequency, early emergency, and long temporal spans. This indicates that research on the health benefits of urban blue–green spaces has multidimensional directions and continuous core themes. In addition, studies on “quality of life” and “subjective well-being” started relatively early, while research on “tree cover” only began to rise in 2021.

Burst Word Analysis

Burst word analysis is an effective tool for predicting dynamic evolution and emerging trends within a specific research field [80]. By detecting the significant growth of keywords or literature citations within a given period, burst word analysis reveals the formation and shifts in research frontiers, reflecting research hotspots and the latest advancements. As crucial benchmark indicators, the appearance intensity (strength), duration, and time distribution of burst words can intuitively reflect the attractiveness of an information explosion to the academic community while capturing the characteristics of new discoveries and directions in the field. In burst word analysis, “Year” represents the year when the keyword first appeared, “Begin” and “End”, respectively, indicate the starting and ending years when the keyword became a research focus, and the red bar chart shows the specific time periods when the keyword became a research hot spot. By examining these burst words, researchers can gain deeper insight into the dynamic changes and frontier directions in the study of the health benefits of urban blue–green spaces.

According to the intensity, duration, and temporal distribution of the burst keywords presented in Figure 10, research hotspots in this field from 2014 to 2024 can be divided into three phases. The earliest phase focused on topics such as “statistics and numerical data”, “environmental planning”, “environmental design”, “very elderly”, “80 and over”, “mental stress”, and “horticultural therapy”. In the mid-phase of this given period, “developing countries” emerged as a new research hot spot. In recent years, the top five burst keywords with the highest strength were “normalised difference vegetation index”, “structural equation modelling”, “urban greening”, “urban environment”, and “urban forest”. This trend indicates a shift in the research focus from foundational topics, methods, and therapies to global issues, particularly the health benefits of landscapes in developing countries. Since then, emphasis has gradually shifted to the application and evaluation of urban green spaces and ecosystem services, with increasing reliance on quantitative methods and data analysis. This evolution reflects the changing themes in the field over time and the evolving interests of researchers, and hints at current research prospects and future directions.

4. Discussion

The distinction between environmental benefits and health benefits is crucial for understanding the multifaceted role of urban blue–green spaces. Environmental benefits, such as improved air quality, reduced urban heat island effects, and enhanced biodiversity, are foundational to the overall health of urban ecosystems [51,52]. These benefits create a healthier environment that indirectly supports human health. Health benefits, however, are more directly related to human well-being and include improvements in mental health, physical fitness, and social cohesion [53,54]. Studies have shown that blue–green spaces can enhance physical fitness by increasing the frequency, intensity, and diversity of physical activities [57,58]. For example, access to urban parks and water bodies encourages walking, cycling, and other forms of exercise, which contribute to better cardiovascular health and reduced obesity rates. The psychological benefits of blue–green spaces are well documented, with evidence suggesting that exposure to natural environments can reduce stress, anxiety, and depression [59,60]. The presence of green and blue spaces in urban areas provides residents with opportunities for relaxation and mental restoration, which are crucial for maintaining mental well-being. Blue–green spaces also play a role in fostering social cohesion and community interaction. These spaces serve as venues for social activities, promoting social support networks and reducing social isolation [61,62]. This aspect of health benefits is particularly important in urban settings where social fragmentation can be a significant issue.

Extensive studies have confirmed the health benefits of urban green spaces, such as lowering blood pressure [18], reducing obesity [19], enhancing psychological resilience [20], alleviating social isolation [21], and improving social cohesion [26]. Green spaces have been widely recognised for their role in providing important places for outdoor activities and social interactions, thereby enhancing residents’ physical health and life satisfaction [26]. Recent epidemiological studies indicate that blue spaces can significantly improve residents’ physical fitness by increasing the frequency, intensity, and diversity of physical activity [28,29,30,31]. Additionally, numerous reports have confirmed that the availability or visibility of blue spaces has a positive impact on alleviating emotional disorders such as anxiety [32,33,34]. Blue spaces also contribute to human health by influencing environmental factors, such as reducing heat stress and surface temperatures, improving PM2.5 concentrations, enhancing air quality, and boosting subjective perceptions of regional ecological quality [27]. Recent trends indicate a shift toward quantitative analysis of urban ecosystem services and health promotion mechanisms [81,82]. Future research should focus on developing robust methodologies to assess the health benefits of blue–green spaces, including the use of advanced spatial analysis tools (e.g., GIS) and health risk modelling methods. Future research should prioritise strategies to reduce inequities in access to natural spaces within urban areas, ensuring that vulnerable populations benefit equally from these resources. This includes understanding the roles of public and private land in the distribution pattern of urban vegetation to promote more equitable and greener cities worldwide [64].

Although there has been a growing body of research on revealing the positive effects and mechanisms of urban blue–green spaces in promoting public health, there are still obvious deficiencies in the existing studies. Most studies have predominantly focused on the health benefits of green spaces while overlooking the unique functions of blue spaces and the synergistic effects between blue and green spaces. Furthermore, there has been a lack of systematic exploration of the mechanisms by which urban blue and green spaces promote public health. Field reviews based on bibliometric analyses are also relatively scarce, limiting a comprehensive understanding of research hotspots, academic networks, and developmental trends. This study employed a combination of bibliometric methods and knowledge mapping to analyse the literature on the health benefits of urban blue and green spaces over the past decade. The findings revealed a consistent increase in research activity in this field over the last ten years. The global academic network is dominated by two main collaborative groups, one centred in China and the other in Western countries, although the academic connections between these groups remain weak. Through multidimensional analysis, this study highlighted previously overlooked aspects of the mechanisms by which blue and green spaces promote public health and identified key directions for future research in this field. These conclusions not only address existing research gaps but also provide theoretical support and scientific evidence to facilitate the practical application of urban blue and green spaces in health promotion.

4.1. Analysis of Research on Health Benefits of Urban Blue–Green Spaces

A systematic review of studies on the health-promoting effects of urban blue–green spaces from 2014 to 2024 can help us comprehensively understand the development process, current situation, and future trends in this field. Since 2014, research on the impact of urban blue–green spaces on the physical and mental health of residents has significantly increased. These studies not only summarise the development trends in this field but also provide important theoretical support and practical implications for future research paths and directions.

In 2014, there was a significant increase in the publication of literature on the health-promoting effects of blue and green spaces, which may be related to the deepening of the concept of healthy cities, driven by relevant international policies and agendas. The 2014 Revision of the World Urbanisation Prospects Report updated the latest data and analyses of global urbanisation levels, trends, and projections, emphasising that successful urban planning agendas must focus on urban settlements of all sizes [4]. Meanwhile, in the 2010s, the World Health Organization (WHO) and countries around the world continued to promote the Healthy Cities Initiative, highlighting the importance of building healthy cities and aiming to improve the health of urban residents through multi-sectoral cooperation and community participation [16,83,84]. Specifically, the sixth phase of the European Healthy Cities Network (2014–2018) focused on neighbourhood design, land development, and green space construction, among others [75]. In October 2014, the Sixth World Conference on Health Promotion in Cities was held in Hong Kong, bringing together leaders, policymakers, and scholars to share knowledge and experiences on improving the quality of life, setting common goals for community health, and strengthening international cooperation [85]. Additionally, in the same year, global “Healthy Cities” were selected, such as Copenhagen, Okinawa, Monte Carlo, and Vancouver, which have made significant progress in building healthy cities and promoting the development of health promotion policies [86]. These activities and ongoing initiatives indicate that the international community’s attention and investment in building healthy cities have deepened, leading to a significant increase in the related literature since 2014.

Notably, since 2014, the number of papers in this field has shown a continuous upward trend, and the growth rate has significantly accelerated since 2019. This phenomenon can be attributed to multiple factors. First, the urban lockdown caused by the 2019 COVID-19 pandemic has further exacerbated residents’ mental health problems [87]. At the same time, the widely recognised health benefits of blue and green spaces, as well as the continuous development of science and technology related to the acquisition and processing of spatial data and research methods of health effects [88], have contributed to research enthusiasm and academic output in this field.

This study also reveals that scholars such as Nieuwenhuijsen, M, Lu, Yi, Wang, and Siqiang, and institutions like the Chinese Academy of Sciences and the University of California System, with high centrality nodes in the scientific map, demonstrate the important “bridge” role of these key individuals and institutions in academic collaboration, reflecting their leading position in the global academic network. The global academic network and cooperation patterns regarding the health benefits of urban blue–green spaces have gradually formed two major research groups, China and Western countries. This indicates that research in this field is developing rapidly worldwide. However, there are limitations to China’s international cooperation. Although the intercountry cooperation network shows a certain density, the nodes with higher centrality are mainly concentrated in developed countries (USA, UK, Australia, Germany, and Italy), with limited participation from developing countries. Only China, Brazil, and India had publication volumes exceeding 100, but their intermediate centralities were all below 0.10. This suggests an uneven distribution of global research resources, which may limit the sharing and application of related knowledge. Conversely, although China’s publication volume and the academic influence of the Chinese Academy of Sciences are prominent, the research networks of its authors are mainly limited to domestic collaborations, with weak connections to research groups in other countries.

From the keyword timeline and burst analysis, it can be seen that the research hot spots on the health benefits of urban blue–green spaces show a dynamic evolution process. In the early stage of the research field (around 2014–2016), the focus was on basic themes such as “statistics and numerical data”, “environmental planning”, and “environmental design”, reflecting the initial exploration of methodology and urban planning and design [89,90]. As the research deepened, the research direction gradually shifted to topics such as “developing countries”, “climate change”, and “physical-activity” in the middle stage (around 2017–2020), indicating that the research began to focus on global issues and the influence mechanisms of individual health behaviours [54,91]. Recently (2021–2024), keywords such as “normalised difference vegetation index (NDVI)”, “urban greening”, and “urban forest” have shown a high degree of attention to the quantitative analysis of urban ecosystem services and health promotion mechanisms [81,82]. This evolutionary trajectory indicates that research is gradually shifting from broad theoretical exploration to multiscale mechanism revelation and application-oriented practical research. This transformation aligns with the practical need for health promotion in the context of urbanisation and climate change. Such transitions from the small to the large and from the superficial to the profound contribute to the better development of cities into health-friendly urban environments, providing theoretical support for the construction of healthy cities. Furthermore, the analysis of the keyword timeline also reveals that urban green spaces have long been a major research focus, whereas keywords related to urban blue spaces only began to emerge around 2019. This time lag may be attributed to several factors. First, blue spaces have often been considered part of green spaces (e.g., water bodies within parks) rather than being studied independently. Second, the rise in the Green Prescription concept has driven more refined research on health benefits, leading to increasing recognition of the health advantages of blue spaces [37]. The Green Prescription concept emphasises the integration of public health research with studies on the natural environment [92], stimulating researchers’ interest in exploring whether different types of natural environments exert distinct health effects. This, in turn, has encouraged a focus on the independent health benefits of blue spaces. Moreover, the mechanisms and effects through which blue and green spaces influence health outcomes may differ [93], making it necessary to expand the research focus from a singular emphasis on green spaces to a more comprehensive examination of the combined effects of blue and green spaces.

Based on the co-citation of published literature and the co-occurrence and clustering analysis of keywords, the mechanism by which urban blue–green spaces affect public health involves direct and indirect coupling of ecological and social factors at different temporal and spatial scales [94]. Previous theoretical studies have pointed out that urban blue–green spaces can influence public health through potential pathways, such as improving air quality, promoting physical activity, enhancing social cohesion, and relieving stress [51], and the impact on health outcomes can be summarised into three knowledge domains: injury reduction, recovery capacity, and building capacity [50]. Bratman’s latest research integrated the olfactory pathway into a conceptual framework for the impact of the natural environment on human well-being. The potential role of the olfactory pathway may have been underestimated in this field of research [53]. Currently, physical activity, stress relief, and social support have been extensively studied and confirmed as important mediating factors for the health benefits of urban blue–green spaces [52], while ecosystem service-related research focuses on analysing the impact of the distribution, form, composition, and configuration characteristics of blue–green spaces on natural processes, such as climate regulation [68] to enhance urban resilience and improve the sensory comfort of the environment. Additionally, the pathways through which urban blue–green spaces affect public health may have synergistic effects. For example, physical activities carried out in community gardens not only restore physical vitality but also contribute to psychological healing and repair of social relationships [95]. Combining multiple pathways can leverage the health benefits of natural contact.

A critical aspect of the relationship between urban blue–green spaces and public health is the issue of environmental justice, which is deeply intertwined with the social determinants of health. Environmental justice refers to the fair distribution of environmental benefits and burdens across different social groups, particularly in relation to access to resources such as blue–green spaces. The social determinants of health, as defined by the World Health Organization, include factors such as socioeconomic status, education, occupation, and access to healthcare, which influence health outcomes and well-being. In terms of exposure levels and environmental justice, excessive spatial differentiation of blue–green space exposure levels often raises issues of environmental justice (green space equity). In the context of the current research, the right to exposure essentially represents the right to health, and its imbalance reflects damage to the health rights of certain groups, which may be a global phenomenon [62,96]. Accessibility is a key factor in the equitable use of urban blue–green spaces. As Lorien et al. have pointed out, access to opportunities for interaction with nature in cities is closely linked to higher education levels and income, while low-income and minority communities often face inadequate accessibility to blue–green spaces [64]. This lack of accessibility not only limits the ability of socially vulnerable groups to benefit from the blue–green spaces but also exposes them to higher risks, such as air pollution, noise pollution, and the urban heat island effect [97], exacerbating environmental injustice. Attractiveness (the quality of blue–green spaces) is another key factor in environmental equity. The quality of blue–green spaces directly affects their appeal and usage rates. However, in cities of Western developed countries, the construction and maintenance costs of blue–green spaces are often tied to local tax revenues, which means that residents with lower rental affordability are constrained to living in areas with a lack of or poor-quality blue–green spaces, while high-quality urban blue–green spaces are often concentrated in high-income communities [98].

Environmental injustice is not merely a matter of the uneven distribution of blue–green spaces; rather, it is the result of the combined influence of multiple factors, including socioeconomic conditions, urban planning, and market-driven forces [99]. Due to the inadequate allocation of blue–green resources, limited accessibility, and lower attractiveness in low-income communities, residents face significant challenges in equitably enjoying the health and social benefits provided by these spaces. More importantly, many blue–green space redevelopment projects have instead exacerbated green gentrification, forcing low-income residents to relocate due to rising housing prices [100]. This not only undermines environmental justice but also disrupts the existing community structure. Therefore, urban blue–green space planning must adopt more inclusive and equitable strategies, enhancing community participation to ensure that all social groups can benefit from blue–green infrastructure.

However, in some highly urbanised areas, growth in the quantity of urban blue–green spaces has become very limited [101], making it urgent to study the specific regulatory mechanisms of urban blue–green spaces on public health and to reveal the relationship between exposure levels and the optimal health benefits of blue–green spaces to achieve an efficient translation of green space exposure and health promotion effects [51,102]. Therefore, exploring the dose–response relationship between exposure levels and health promotion effects is also worthy of attention. In terms of exposure levels, the “just green enough” urban planning concept proposed by Wolch et al. avoids the gentrification of green spaces caused by excessive greening [56]. In terms of exposure duration, other studies have shown that the immediate effects of green space exposure are most significant within 10 min compared to 30 min [103]. However, there is a threshold effect between long-term health benefits and the duration of natural exposure, with a recommended lower limit of 120 min/week and a peak benefit range of 200–300 min. Beyond this duration, the health improvement effect tends to level off [104]. Clarifying the optimal values of exposure duration, frequency, and intensity will provide a scientific basis for the formulation of healthy city policies and the efficient utilisation of blue–green spaces.

While bibliometric metrics such as citation frequency provide valuable insights into the impact and influence of research, it is important to recognise their limitations. Citation counts can be influenced by various factors, including the age of the publication, the size of the research community, and the visibility of the journal. Emerging topics, in particular, often have lower citation counts due to their novelty and the time required for the research community to fully engage with and recognise their significance. For instance, the role of blue spaces in promoting physical activity and mental health has gained increasing attention in recent years, with studies highlighting their unique contributions to well-being [28,29,30,31]. Additionally, the impact of blue–green spaces on environmental justice and the distribution of health benefits across different socioeconomic groups is an area that requires further exploration [74]. These themes, while not yet dominating the citation landscape, represent important directions for future research and policy development.

The relatively weak collaboration between Chinese and Western research communities may be attributed to differences in research progress, variations in research focus, language barriers, differences in citation practices, and the underdevelopment of international collaboration networks. In terms of research progress, Li et al. pointed out that, compared to the solid research foundation established by Western academia on the impact of the built urban environment on public physical and mental health, studies in China are still in the exploratory stage. In terms of research focus, there are significant differences in the topics between Chinese and Western scholars [105]. Chinese research tends to highlight the relationship between environmental issues (e.g., air pollution and the urban heat island effect) under the context of rapid urbanisation and public health [106,107], and to often be influenced by policy-driven factors [83,108]. In contrast, Western studies are more inclined to explore issues, such as environmental justice [56], mental health [50], and the multidimensional benefits of ecosystem services in the health domain. These differences in research perspectives may, to some extent, limit the potential for collaboration between the two sides [109]. Additionally, language barriers are among the key factors restricting academic cooperation [110]. Montgomery pointed out that English, as the dominant language of international academic communication, holds a central position in the global research system [111]. However, although the number of publications by Chinese scholars in SCI/SSCI journals has increased significantly in recent years, the readability and language quality of these articles may still affect their international dissemination.

4.2. Limitations and Future Research

This study conducted a quantitative and qualitative investigation of research trends and development in the association between urban blue–green spaces and human health using NoteExpress, Endnote, CiteSpace, and Excel. Although some conclusions that are helpful for deepening research in this field were obtained, this study has some limitations. Because only the literature included in the WoS and Scopus databases was analysed, some relevant studies were excluded, especially the exclusion of non-English literature, which may lead to a bias toward Western perspectives. At the same time, the screening of literature formats other than article and review may further result in this study not covering all the literature related to the health benefits of urban blue–green spaces. Furthermore, this study mainly reflects research from high-income and upper middle-income countries (e.g., USA, UK, China), with limited representation from low- and lower-middle-income countries. This imbalance may stem from database biases, funding disparities, and uneven academic collaboration networks. Additionally, although CiteSpace has powerful functions in bibliometric analysis, it has some inherent limitations. For example, the analysis results of CiteSpace are highly dependent on thresholds (such as co-citation frequency and centrality); however, there are no accurate rules for threshold interpolation [112]. Different threshold settings may lead to significant changes in the network structure and hot topics, thereby affecting the interpretation of the results. Additionally, this study did not explore the independent effects of green space or blue space on urban residents’ health. Therefore, the findings reflect the combined impact of both. Future research should further differentiate these effects to obtain more accurate and in-depth conclusions.

In future research, it will be crucial to evaluate the continuous impact of urban blue–green spaces on physical and mental health. This involves accurately assessing residents’ exposure levels to blue–green spaces. Exposure measurements from a two-dimensional aerial perspective should be fully combined with the three-dimensional perception of blue–green spaces in the real world, thereby actively building a multidimensional exposure assessment system that combines aerial and human perspectives.

Simultaneously, it is necessary to determine the exposure indicators that significantly contribute to residents’ health and set their optimal threshold standards. However, this involves improving the inequality of urban blue–green infrastructure, which is related to the development of healthy, resilient, and high-welfare urban communities. According to Nesbitt et al., this requires a thorough understanding of the roles of public and private land in the distribution pattern of urban vegetation to promote more equitable and greener cities worldwide [64].

Furthermore, this study also identifies the need for more in-depth interdisciplinary collaboration in research on the health benefits of urban blue–green spaces. One potential approach is to establish public databases that integrate data from different disciplines (e.g., health data, environmental pollution, and blue–green space distribution) and utilise spatial analysis tools (e.g., GIS) and health risk modelling methods (e.g., exposure assessment models) to comprehensively evaluate the health benefits of blue–green spaces. Additionally, disciplines (e.g., public health, environmental science, and urban planning) could collaboratively develop research frameworks to quantify the impact of blue–green spaces on residents’ physical and mental health. Moreover, according to the “Adapting to Climate Change to Protect Public Health: Vulnerability and Adaptation Assessment” guideline, formulated by the World Health Organization in 2013, under the backdrop of global climate change, the monitoring and assessment of health risks associated with climate change have been incorporated into planning and implementation [39]. Therefore, at the policy-making stage, urban planners could work with environmental scientists and public health experts to incorporate health impact assessments into legal and regulatory frameworks, ensuring that environmental justice and relieving potential risks that cities bring are considered in subsequent planning and design processes. By implementing these strategies, future research can effectively integrate public health, environmental science, and urban planning, advancing both theoretical knowledge and practical applications in the field of urban blue–green spaces and health.

In addition, future research should also strengthen collaboration between Chinese scholars and scholars from Europe and America to promote cross-cultural perspective research, especially exploring the differences in the health benefits of blue–green spaces in different urban settings in the context of globalisation. It is suggested that international research foundations and relevant policymakers design dedicated cooperation mechanisms to enhance the contribution of different countries and regions to blue–green space research and promote the practical application of research results.

In conclusion, a substantial amount of research has found that urban blue–green spaces are associated with health benefits. For instance, studies have found that increased greenspace exposure was associated with decreased salivary cortisol, heart rate, diastolic blood pressure, HDL cholesterol, low frequency heart rate variability (HRV), and increased high frequency HRV, as well as decreased risk of preterm birth, type II diabetes, all-cause mortality, small size for gestational age, cardiovascular mortality, and an increased incidence of good self-reported health [52]. Urban green space is positively correlated with attention and mood [54]. Green space has potential protection for adult mental health (depression and anxiety) [62]. Street view green and blue space can protect Chinese elderly people from depression [76]. These studies form a substantial body of evidence supporting the health-promoting effects of urban blue–green spaces. Future research should focus on several key areas to address the gaps identified in the current study. Firstly, there is a need to explore the dose–response relationships between exposure to blue–green spaces and specific health outcomes, such as reduced stress levels and improved cardiovascular health. Secondly, the unique health benefits of blue spaces should be investigated more thoroughly, given their potential to enhance physical activity and reduce emotional disorders. Thirdly, the synergistic effects of blue and green spaces on diverse populations should be examined, considering factors such as age, socioeconomic status, and cultural background. This will help to ensure that the health benefits of blue–green spaces are accessible to all segments of the population.

5. Conclusions

The field of urban blue–green spaces and health has seen significant progress, but gaps remain. Research has largely focused on green spaces, with blue spaces and their synergistic effects on health still underexplored. Recent studies have started to address ecosystem services, environmental justice, and health mechanisms, but these areas need deeper investigation. Future work should examine dose–response relationships, the unique health benefits of blue spaces, and the combined effects on diverse populations. Strengthening interdisciplinary research and international collaboration, especially involving low- and middle-income countries, will be crucial to deepen the knowledge and inform effective policies.

Exploring the potential health-promoting effects of urban blue–green spaces offers a vital opportunity to address the global challenges brought about by urbanisation, climate change, and the post-pandemic era. As cities around the world continue to grow, the integration of blue–green infrastructure into urban planning is not just a local issue but a global imperative. By fostering international collaboration, sharing best practices, and prioritising equitable access to these spaces, we can create healthier, more resilient cities for all. Future research should focus on deepening our understanding of the synergistic effects of blue–green spaces, including their comprehensive impact on mental and physical health. At the same time, interdisciplinary research—integrating urban planning, public health, and environmental science—is crucial for revealing the complex pathways through which they exert their effects.

In addition, addressing disparities in access to blue and green infrastructure remains a pressing issue. Future research should prioritise strategies to reduce inequities in access to natural spaces within urban areas, ensuring that vulnerable populations benefit equally from these resources. Therefore, strengthening international collaborations is urgent and important. Initiatives to establish global data sharing systems, standardised methodologies, and cooperative policy development are critical.

Ultimately, integrating evidence-based blue–green space design into urban planning and public health strategies is essential for creating sustainable, resilient, and healthy cities.