Urban Forests and Green Environments for Sustainable Cities: Knowledge Landscape, Research Trends, and Future Directions

Abstract

With the intensification of global urbanization and climate change challenges, urban green spaces and urban forests are playing an increasingly critical role in supporting sustainable urban development. Based on the Web of Science Core Collection, this study employed bibliometric analysis and visualization methods (VOSviewer 1.6.19 and Bibliometrix v5.0.1 (R package)) to systematically map the global knowledge landscape of urban green space and urban forest research from 2000 to 2025, identifying key thematic clusters and research fronts. The results show a shift in research focus from traditional green infrastructure and ecosystem service assessment to an integrated approach emphasizing multifunctionality, climate adaptation, public health, and governance innovation. Furthermore, research efforts are concentrated in rapidly urbanizing regions, and global spatial distribution remains a significant issue. Based on this, this paper proposes a strategic research agenda to promote the development of this field, including four key directions: (1) embedding social equity and people-oriented values into green space planning and management; (2) leveraging digital technologies and artificial intelligence to strengthen urban ecological governance; (3) promoting the transition of green infrastructure from fragmented to systematic ecological networks; and (4) deepening the role of urban green space in climate adaptation and sustainable urban transformation. By systematically combing through the knowledge system and governance logic of urban forests and greening, this article aims to reveal the key role of urban ecosystems in addressing climate change and promoting social well-being, and provide operational scientific basis and policy inspiration for the sustainable transformation of global cities.

1. Introduction

In recent decades, rapid urbanization has profoundly transformed urban environments, posing severe challenges to ecological sustainability and public health. The United Nations (UN DESA, 2018) projects that by 2050, 68% of the global population will reside in urban areas, intensifying pressure on urban land and ecological resources [1]. The rapid expansion of cities and high-intensity human activities have led to the degradation of ecosystem services, declining environmental quality [2,3], and the emergence of urban heat islands [4], frequent flooding [5,6,7], air pollution [8], and biodiversity loss [9,10,11], all of which severely undermine urban livability and resilience [12]. How to enhance ecosystem services and improve urban livability amid ongoing urbanization has thus become a critical issue in the fields of sustainable urban development and public health [13,14,15,16].

Urban planning and policy-making agencies increasingly regard Urban Green Spaces (UGSs) as essential infrastructure for fostering sustainable and healthy cities [17,18]. Early research primarily focused on the ecological benefits and environmental regulatory functions of urban green spaces—such as mitigating the urban heat island effect, improving air quality, and supporting biodiversity [19,20]. Subsequently, scholarly attention shifted toward the social and health effects of urban greenery [21]. Jabbar et al. [22] found that urban green spaces are closely associated with physical, psychological, and social well-being; Wolch, [23] from the perspective of environmental justice, proposed the “just green enough” strategy to prevent green gentrification; and Lee et al. [24] and Konog et al. [25].emphasized the importance of public demand and perception of green spaces in enhancing quality of life In recent years, research has further expanded to encompass climate adaptability and innovations in urban governance [26]. For instance, Lehmann [27] discussed “renaturalization” and “rewilding” as strategies for strengthening urban resilience, while Chen [28] proposed an integrated, multidimensional framework for sustainable urbanization. Overall, these studies reveal the multifaceted roles of UGSs in sustainable urban development [29,30]. However, from a research content perspective, existing literature largely concentrates on single dimensions—such as health effects, ecological performance, or green justice—lacking a systematic understanding of the multi-objective and multi-scalar coupling relationships among them [31,32,33]. From a methodological perspective, most studies rely on case studies or traditional reviews, with limited systematic quantitative analyses and knowledge-map visualizations based on large-sample data [34,35].This limitation constrains a comprehensive depiction of the field’s developmental structure and thematic evolution. In terms of research scope, despite the abundance of regional and national studies, systematic efforts to identify the global knowledge base, disciplinary networks, and frontier trends of UGSs and sustainable healthy cities remain scarce [36,37].

To fill this gap, the present study employs bibliometric analysis to examine 620 publications retrieved from the Web of Science Core Collection (2000–2025) and conducts scientific knowledge mapping using VOSviewer 1.6.19 and Bibliometrix v5.0.1 (R package) [38]. VOSviewer enables the construction and intuitive visualization of large-scale co-citation, co-word, and collaboration networks, facilitating the identification of thematic clusters and their structural relationships. Bibliometrix, in turn, provides a reproducible analytical workflow encompassing data cleaning, bibliometric statistics, thematic evolution, and strategic mapping, thereby enhancing the robustness and interpretability of results [39]. The main objectives of this study are as follows:

• Research landscape and collaboration network analysis: To systematically reveal the publication scale, disciplinary distribution, and evolutionary trends of research on urban green spaces and sustainability, and to identify the key countries, institutions, and authors occupying central positions and structural roles in the global collaboration network.
• Knowledge base and theoretical framework: Through co-citation analysis, to clarify the core knowledge base and key journals in the field, and to analyze the logical construction of theoretical systems, methodological frameworks, and disciplinary evolution pathways.
• Knowledge structure and thematic clustering analysis: By applying clustering and network analysis methods, to uncover major research themes, inter-cluster relationships, and interdisciplinary coupling characteristics, and to identify the knowledge structures of core and peripheral topics.
• Thematic evolution and frontier trends: Based on thematic evolution and burst analysis, to trace the temporal migration and diffusion of research themes, locate emerging hotspots and potential growth areas, and explore the evolutionary trajectories and implications of future research directions.

From a global perspective, this study systematically maps the research landscape of “urban green spaces and sustainable healthy cities,” comprehensively revealing its disciplinary intersections, geographical distributions, knowledge networks, and thematic dynamics. By identifying critical research gaps and frontier hotspots, this paper provides new insights for constructing theoretical frameworks on the health effects of green spaces. The findings not only offer theoretical support for disciplinary development and interdisciplinary innovation but also provide quantitative evidence and decision-making references for urban green space planning, health policy formulation, and sustainable urban transformation—thereby holding significant academic value and practical relevance.

2. Materials and Methods

2.1. Data Sources and Search Strategy

To ensure the authority, systematicity, and comparability of the research data, this study adopts the Web of Science Core Collection (WoS) as the primary data source [40,41]. Provided by Clarivate Analytics, WoS is one of the most influential international academic citation databases, extensively covering disciplines such as natural sciences, social sciences, environmental sciences, and health sciences. The WoS Core Collection consists of multiple sub-databases, with strict inclusion standards that cover only peer-reviewed journal articles of high academic impact, thereby ensuring the reliability and reproducibility of the data [42,43,44]. For studies aimed at constructing global knowledge maps and identifying the evolution of interdisciplinary themes, the depth and standardization of WoS data serve as essential prerequisites for achieving core network analysis and thematic clustering. This approach effectively avoids the complex data cleaning procedures and inconsistencies in standards that may arise from integrating multiple databases [45,46].

To systematically retrieve English-language publications related to urban green space and sustainable healthy cities, this study designed a precise Boolean search strategy with logical depth. The search employed the Topic Search (TS) function and incorporated three core concepts: “urban green space,” “sustainable development,” and “public health.” The search query was constructed as follows: TS = ((“urban green space*” OR “urban greenery” OR “urban greening” OR “green infrastructur*” OR “blue-green infrastructur*” OR “blue green infrastructur*” OR (“greenspace*” NEAR/3 (urban OR city OR cities OR metropolitan)) OR “urban park*” OR “pocket park*” OR “community park*” OR “linear park*” OR “urban forest*” OR “street tree*” OR “urban tree*” OR “tree canopy” OR “urban canopy” OR “urban vegetat*” OR “urban nature” OR “green corridor*” OR “greenway*” OR “green belt*” OR greenbelt* OR “urban open space*” OR “public open space*”) AND (“ecological sustainab*” OR “environmental sustainab*” OR “sustainab* develop*” OR “sustainable city” OR “sustainable cities” OR “urban sustainab*” OR “ecological conserv*” OR “environmental conserv*”) AND (“public health” OR “health outcome*” OR “health impact*” OR “health effect*” OR “mental health” OR “physical health” OR “human well-being” OR “human wellbeing” OR “well-being” OR wellbeing OR “quality of life” OR “life satisfaction” OR “human happ*” OR “subjective well-being” OR “subjective wellbeing” OR “psychological well-being” OR “mental well-being” OR “social well-being” OR morbidity OR mortality)). The search period was set from 1 January 2000, to 10 August 2025, in order to capture research developments and evolutionary trends in this field over the past 25 years.

The initial search yielded 645 publications. After restricting the language to English, 637 documents remained, ensuring the comparability and international applicability of the dataset. Based on research relevance and document type, only “Articles” (522), “Review Articles” (67), and “Proceedings Papers” (44) were retained, while “Early Access” (9), “Editorial Material” (5), and “Corrections” (1)—which do not represent formally published or research-oriented content—were excluded. This refinement resulted in 631 formally published, research-oriented, high-quality documents.

Subsequently, by carefully reviewing the titles, abstracts, and keywords, unrelated documents were excluded, yielding a final dataset of 620 highly relevant publications. These documents formed the foundation for subsequent bibliometric analysis and knowledge mapping. The entire process strictly followed the PRISMA 2020 guidelines, ensuring both the authority of the data source and the scientific validity of the sample selection. The screening procedure is illustrated in Figure 1.

2.2. Data Processing and Analytical Methods

This study adopts bibliometric methods to conduct a systematic quantitative analysis of research outputs in the field. Bibliometrics applies statistical and mathematical approaches to objectively describe and comprehensively analyze the quantity, structure, distribution, developmental trends, and knowledge networks of academic literature. It has been widely used to reveal disciplinary evolution, research hotspots and frontiers, collaboration patterns, and scholarly influence [47,48]. Multiple mainstream analytical tools were employed in this study, each serving distinct functions across different data dimensions, as follows:

Microsoft Excel: Used for descriptive statistics and visualization of annual publication volume, disciplinary distribution, and core journals, providing a standardized data foundation for subsequent in-depth analysis.

VOSviewer 1.6.19: Applied to construct author collaboration networks, institutional collaboration networks, national collaboration networks, and keyword co-occurrence networks. VOSviewer allows intuitive visualization of connections and clustering among nodes, thereby uncovering collaboration patterns, research team distributions, and thematic clustering of knowledge structures within the field [49].

CiteSpace 6.2.R6: Employed for generating co-citation analysis maps. CiteSpace identifies highly influential publications, disciplinary frontiers, and the evolutionary pathways of knowledge structures. Key parameters include setting the time slice to one year, applying the g-index (k = 25) as the selection criterion, and using the Pathfinder algorithm for network pruning.

Bibliometrix v5.0.1(R package): Used for temporal analysis of keywords and visualization of thematic evolution trends. This tool supports batch data processing and automatic output of multiple bibliometric indicators, facilitating a systematic review of thematic development trajectories and hotspot distributions.

3. Results and Critical Discussion

3.1. Publication Output and Disciplinary Distribution Trends

The annual number of publications serves as a fundamental indicator for evaluating the research activity and scientific influence of a given field. It reflects the trajectory of scholarly development, the pace of knowledge accumulation, and the potential for future growth [50,51]. Figure 2 illustrates the annual variation in publication volume in this research domain from 2000 to 2025. As shown, between 2000 and 2010, the field was still in its infancy, with fewer than three publications per year. In some years, such as 2005, 2009, and 2010, no related articles were published at all, indicating limited research activity and minimal academic attention to the topic.

Beginning in 2012, the annual number of publications started to increase gradually, reaching nine in both 2014 and 2015. This marked the initial recognition of urban green space as an important subject within the framework of urban health and sustainable development. Notably, after 2016, publication output rose sharply: the annual number first exceeded double digits in 2016 (15 articles), increased to 34 in 2019, and surged to 44, 63, and 77 articles in 2020, 2021, and 2022, respectively. These trends demonstrate the rapid rise in scholarly interest in this topic. In 2023 and 2024, the number of publications reached 94 and 120, respectively, setting historical records and underscoring the emergence of this field as a research hotspot in urban sustainability and health. Although the number in 2025 shows a slight decline (102 articles), it should be noted that this figure was retrieved on August 10 and thus represents only part of the year’s output. The final total is highly likely to rise further by year-end.

In terms of cumulative publication volume, the total reached 620 articles by 2025, exhibiting a typical exponential growth trend. The fitted results indicate that the growth curve conforms to y = 0.2029x^2.0917, with a coefficient of determination R² = 0.7844, suggesting that research in this field has undergone exponential acceleration over the past decade. This trend not only highlights the significant academic position of urban green space in addressing urbanization challenges and promoting public health and ecological sustainability, but also reflects the deepening influence of global policy orientations and the increasing integration of interdisciplinary research [52,53]

Core journals serve as crucial platforms for disseminating scientific research, and their publication volume and citation frequency provide important indicators of academic authority and research influence within a given field.

Table 1. Top Ten Core Journals by Publication Volume.

Rank	Institutions	NP	NC	IF (2024)
1	Sustainability	99	1787	3.3
2	Urban Forestry & Urban Greening	43	1832	6.7
3	Land	40	425	3.2
4	Sustainable Cities and Society	16	554	12
5	Landscape and Urban Planning	15	5278	9.2
6	Forests	11	71	2.5
7	Ecological Indicators	9	366	7.4
8	Frontiers in Sustainable Cities	9	86	2.1
9	Frontiers in Public Health	7	34	3.4
10	GeoJournal	7	184	1.9

presents the top ten core journals ranked by publication volume. Among them, Sustainability ranks first with 99 papers, accounting for 15.9% of the total publications, highlighting its prominence and visibility in this research domain. However, its impact factor (3.3) is considerably lower than that of other high-impact journals, suggesting relatively limited academic recognition in terms of citation. In contrast, although Urban Forestry & Urban Greening ranks second in publication volume (43 papers), its citation count (1832) and impact factor (6.7) are substantially higher than those of Sustainability, underscoring its strong academic recognition in urban green space research. Similarly, Sustainable Cities and Society and Landscape and Urban Planning, despite having fewer publications (16 and 15 articles, respectively), exhibit very high impact factors (12.0 and 9.2) and citation counts (554 and 5278, respectively). These figures demonstrate their leading role in producing high-quality research outputs. Both journals emphasize depth and innovation, serving as important outlets for high-level scholarly contributions.

Overall, Sustainable Cities and Society, Landscape and Urban Planning, and Urban Forestry & Urban Greening stand out in terms of academic influence and subject relevance, representing the leading journals in this field. Researchers are advised to prioritize these high-impact journals when selecting publication venues, taking into account impact factor, thematic alignment, and citation potential, in order to enhance the visibility and academic influence of their work [54].

Statistical analysis based on the Web of Science classification reveals that this research field exhibits a pronounced interdisciplinary integration, primarily spanning environmental science, urban studies, and ecological health.

Table 2. Top 20 Research Areas.

Rank	Web of Science Categories	NP	Rank	Web of Science Categories	NP
1	Environmental Sciences	270	11	Geography Physical	31
2	Environmental Studies	265	12	Construction Building Technology	26
3	Green Sustainable Science Technology	167	13	Energy Fuels	24
4	Urban Studies	117	14	Biodiversity Conservation	21
5	Forestry	60	15	Engineering Civil	20
6	Ecology	56	16	Multidisciplinary Sciences	17
7	Geography	52	17	Engineering Environmental	16
8	Plant Sciences	52	18	Meteorology Atmospheric Sciences	16
9	Regional Urban Planning	46	19	Remote Sensing	13
10	Public Environmental Occupational Health	43	20	Geosciences Multidisciplinary	12

lists the top 20 research areas. Among them, Environmental Sciences and Environmental Studies are the most prominent, with 270 and 265 publications, respectively, underscoring the foundational role of ecological and environmental perspectives in supporting this research theme. Ranked third, Green Sustainable Science Technology has produced 167 publications, highlighting the critical importance of green technologies and sustainable approaches in building healthy cities. Following closely are Urban Studies (117 publications) and Regional Urban Planning (46 publications), both of which emphasize the central role of urban planning and spatial structure in the allocation of green spaces.

Overall, research on urban green space and sustainable healthy cities demonstrates not only a multidisciplinary synergy led by environmental sciences but also the construction of a systematic and intersecting knowledge framework across spatial planning, ecological functions, public health, and engineering technologies. This integrative research pattern suggests that the field will continue to expand its boundaries between theoretical advancement and practical application, providing a solid scientific foundation for urban sustainable transformation and the enhancement of human well-being.

3.2. Geographical Distribution of Publications

Analyzing the global publication landscape of urban green space and sustainable healthy city research at the national level helps to reveal the degree of international academic participation and the leading forces in this field. Figure 3 illustrates the number of publications and their geographical distribution across countries. As shown, China is by far the leading contributor, with 180 related publications, accounting for 17.9% of the global total. This indicates its international leadership in promoting the integration of green city construction and the healthy city concept. The United States ranks second with 79 publications (7.9%), reflecting its sustained focus on urban health and its strong capacity for multidisciplinary integration. The United Kingdom (48 publications, 4.8%), Italy (47 publications, 4.7%), and Germany (40 publications,4.0%) follow closely, suggesting that developed European countries also maintain a solid research foundation and policy-driven momentum in this area.

From a geographical perspective, the distribution of publications presents a pattern of “concentration in developed countries, rising prominence of Asia, and global expansion.” Western developed countries have accumulated extensive theoretical and practical experience in urban green space and healthy city research, while Asian countries, particularly China, have rapidly increased their research influence in recent years through policy initiatives and financial investment. Emerging economies such as Brazil in South America and South Africa in Africa have also joined this research domain, contributing diverse perspectives and regional experiences that enrich the development of global theories and practices in sustainable healthy cities. Nevertheless, some regions—such as Africa and Southeast Asia—still show limited publication output, reflecting uneven distribution of academic resources and research capacity worldwide. Strengthening international collaboration and knowledge sharing will be essential to promote more balanced global development in this field.

To further reveal the patterns of international academic collaboration in this research field, VOSviewer software was employed to conduct a visualization analysis of national cooperation networks. The results are shown in Figure 4. The United States, China, the United Kingdom, Germany, and the Netherlands occupy central positions within the network, characterized by strong connectivity and high betweenness centrality. These countries are not only the main contributors in terms of research output but also serve as key hubs of international collaboration. The United States maintains stable cooperative relationships with the United Kingdom, Germany, Australia, and Canada, reflecting its leading role in promoting global collaborative research on urban green space and health-related issues. Although China ranks first in publication volume, its collaboration network exhibits a more decentralized, multi-nodal pattern, with extensive connections to countries such as the United Kingdom, Australia, Malaysia, and Iran, indicating a gradual deepening of its international cooperation.

European countries have also formed closely knit regional collaboration networks. In particular, clusters led by the Netherlands, Sweden, Italy, and Poland maintain frequent partnerships with neighboring countries such as Belgium, Finland, Lithuania, and Ukraine, reflecting a typical EU research collaboration model. Spain, acting as a bridge between Southern and Central European countries, occupies a network position with distinct intermediary characteristics.

Overall, the current research network demonstrates a cooperative landscape centered on developed countries in Europe and North America, with broad participation and active North–South interactions. Looking ahead, strengthening collaboration across regions, cultures, and economies will be essential to foster global knowledge sharing and policy exchange on urban green space and healthy cities, thereby more effectively addressing the challenges of sustainable health under the pressures of urbanization.

3.3. Influential Authors

Analyzing author contributions helps to reveal the current state of academic development in this research field, identify core researchers and their scholarly influence, and provide deeper insights into collaboration networks among authors. A total of 2453 authors have participated in this domain.

Table 3. Top 10 Authors by Publication Volume.

Rank	Author	NP	NC	H-Index
1	Thomas Panagopoulos	7	498	29
2	Abdullah Addas	6	94	14
3	Haase, Dagmar	5	535	79
4	Adriano Bressane	4	23	10
5	Chen, Wendy Y.	4	25	1
6	Daher, Carolyn	4	112	12
7	Francisco de la Barrera	4	96	15
8	Loureiro, Anna Isabel Silva	4	23	6
9	Maghrabi, A.	4	84	7
10	Badiu, Denisa	3	242	11

Note: NP = Number of publications; NC = Total number of citations; h-index (Hirsch index) = measure of citation impact.

presents the top ten authors ranked by publication volume. As shown, Thomas Panagopoulos ranks first with seven publications, demonstrating his consistent research output in this area. He is followed by Abdullah Addas (six publications) and Dagmar Haase (five publications), while most other highly productive authors have published around four papers. In terms of total citations (NC), Dagmar Haase stands out with 535 citations, far exceeding other authors. Although her number of publications is not the highest, the remarkable citation count highlights the high recognition and broad dissemination of her research.

The H-index, as an important indicator of academic influence and sustained contributions, further reveals the hierarchical structure of author impact. Thomas Panagopoulos and Dagmar Haase lead with H-indices of 29 and 79, respectively, indicating the extensive breadth and depth of citations of their work in this field. By contrast, Anna Isabel Silva Loureiro and A. Maghrabi, despite having a comparable number of publications, show lower H-indices of 6 and 7, respectively. This suggests that their citations are more scattered and have yet to consolidate into a systematic scholarly impact.

To further uncover the patterns of scholarly collaboration within this research field, VOSviewer was used to visualize author publication networks and generate an author collaboration map (Figure 5). In the figure, nodes represent authors, while lines denote cooperative relationships between them. The analysis shows that Per Angelstam occupies a central hub position, linking multiple collaborative groups and serving as a key bridge between otherwise separate research networks. Together with Robert Axelsson, Pablo Garrido, and others, he forms the blue cluster, which demonstrates highly cohesive and extensive collaboration, representing a research community largely composed of Nordic scholars.

The green cluster, centered on Marine Elbakidze, includes scholars such as Olha Adamenko, Ruslan Gunko, and Victor Karamushka from Ukraine and Eastern Europe. This group is characterized by close cooperation and high network density, reflecting the collective scientific strength of this region in ecological governance and green space research. The red cluster, represented by Bogdan Jaroszewicz and Robert Kanka, primarily consists of researchers from Central and Eastern European countries and displays a dense, strongly connected network structure. Additionally, the yellow cluster, centered around K. Ingemar Jonsson along with Christine Wamsler and Thomas H. Beery, forms a relatively independent collaborative network.

Overall, the author collaboration network in this field exhibits the characteristics of “core leadership, multiple parallel clusters, and regional synergy.” A few key authors with high centrality play a vital role in integrating dispersed resources and fostering international collaboration. At the same time, the distinct regional characteristics of the clusters reflect differences in research foci and collaborative strategies across the globe. Looking ahead, greater emphasis should be placed on promoting cross-team collaboration and joint innovation, thereby enhancing the overall integration and global impact of urban green space research.

3.4. Influential Institutions

Institutional analysis helps to reveal the research landscape and core forces in this field, providing valuable insights into the academic influence and collaboration networks of key organizations. Such analysis also offers guidance for future research and cross-institutional cooperation. In the domain of urban green space and sustainable healthy city research, a total of 1118 institutions have participated.

Table 4. Top 10 Institutions by Publication Volume.

Rank	Organization	NP	NC	AC
1	Chinese Academy of Sciences	25	452	18
2	University of Chinese Academy of Sciences	15	226	15
3	Humboldt University	10	665	67
4	Swedish University of Agricultural Sciences	10	1805	181
5	UFZ Helmholtz Centre for Environmental Research	10	356	36
6	Stockholm University	9	1051	117
7	University of Algarve	9	572	64
8	University of Hong Kong	9	118	13
9	Peking University	8	188	24
10	Beijing Forestry University	7	57	8

Note: NP = Number of publications; NC = Total citations; AC = Average citations.

lists the top ten institutions ranked by publication volume, presenting a clear picture of the research distribution and the scholarly impact of leading organizations.

The results show that the Chinese Academy of Sciences ranks first with 25 core publications, underscoring its remarkable research activity and sustained investment in this area. Closely following is the University of Chinese Academy of Sciences, with 15 publications, reflecting its prominent role in advancing research within this field. By contrast, the Swedish University of Agricultural Sciences, though contributing only 10 publications, has achieved a total of 1805 citations, with an average of 181 citations per article. This demonstrates the exceptionally high impact and wide dissemination of its research outputs. Similarly, Humboldt University is noteworthy, with 665 total citations and an average of 67 citations per paper, highlighting its strong knowledge contribution to urban green space and health research.

Overall, European institutions—particularly universities in Nordic countries such as the Swedish University of Agricultural Sciences and Stockholm University—may not dominate in terms of publication volume but excel significantly in citation impact, reflecting their emphasis on high-quality and high-impact research outputs. In contrast, Chinese research institutions demonstrate a clear advantage in terms of publication quantity, representing the rapid rise in research capacity in this field.

To further reveal the patterns of scientific collaboration in the field of urban green space and sustainable healthy cities, this study employed VOSviewer to construct an institutional collaboration network (Figure 6). Overall, the network demonstrates a multi-core and tightly coupled structure, with several institutions forming regional and international research clusters, underscoring the global and cross-regional nature of collaborative activities in this field. At the center of the network, the Chinese Academy of Sciences occupies a pivotal position with very high betweenness centrality, linking multiple high-output institutions such as Humboldt University, UFZ Helmholtz Centre for Environmental Research, and Stockholm University. This has resulted in a multinational collaborative cluster led by the Chinese Academy of Sciences, indicating not only its strong research productivity but also its crucial role as a bridge in international cooperation.

Another significant cluster is formed by Arizona State University, Swedish University of Agricultural Sciences, Tsinghua University, and the US Forest Service. This cluster highlights the research strengths of North America and Northern Europe in areas such as green infrastructure and urban ecosystem services. In particular, Arizona State University maintains extensive collaborations with multiple institutions, demonstrating a wide-reaching network and strong international influence.

In sum, the current collaboration network reflects a “multi-core, multi-cluster” structure, with certain institutions emerging as key nodes in cross-national cooperation. Future research should further enhance deep collaboration among high-output institutions, strengthen knowledge flow and sharing across regions, and promote the systematic development of sustainable healthy city research on a global scale.

3.5. Research Knowledge Base

Co-citation analysis is employed to uncover the knowledge structure and research hotspots within an academic field. By examining the frequency with which documents are cited together, this method identifies core literature and major research themes. It provides valuable insights into the developmental trajectory of the discipline, helps detect emerging trends, and assesses scholarly influence. In this study, CiteSpace 6.2.R6 was used to generate a citation network map (Figure 7). The analysis covered the period from 2002 to 2025, with a time slice length of one year. The g-index (k = 25) was selected as the threshold. The resulting network comprised 712 nodes and 1917 citation links, with a network density of 0.0076. To optimize the structure of the map, the Pathfinder pruning algorithm was applied, and 1.0% of the nodes were labeled.

Among the most frequently cited works, one of the most influential nodes in the network is the article by Wolch, J. R. et al. [23], published in Landscape and Urban Planning in 2014: Urban green space, public health, and environmental justice: The challenge of making cities ‘just green enough’. This study has been cited 3379 times across all databases, underscoring its significant academic status in the field. By examining the complex interrelationships among urban green space, public health, and environmental justice, the authors highlight that while green space planning can generate health benefits, it may also exacerbate social inequality, particularly through the marginalization of vulnerable groups under “green gentrification.” They propose the concept of “just green enough,” stressing that green space development should avoid accelerating land commodification, and instead promote equitable distribution of urban green space through community-led and justice-oriented approaches. This work laid a crucial theoretical foundation for subsequent studies on green infrastructure and social equity.

Another highly influential work is the article by Reyes-Riveros, R. et al., published in Urban Forestry & Urban Greening in 2021: Linking public urban green spaces and human well-being: A systematic review [55], which has been cited 335 times across all databases. Through a systematic review of 153 empirical studies, this research investigates how the characteristics of public urban green spaces affect human well-being. The findings reveal that features such as structure, biodiversity, and naturalness generally have positive impacts on dimensions of well-being including health, safety, social relationships, and freedom of choice and action, with health effects being the most prominent. The study also notes that most existing research relies on subjective perception measures and emphasizes the need to combine subjective and objective methods in the future to enhance the accuracy of evaluations and their policy relevance. This work provides important theoretical insights and practical guidance for urban green space planning and the promotion of human well-being.

3.6. Knowledge Structure and Clustering Characteristics

To systematically uncover the core themes, research hotspots, and the evolutionary characteristics of the knowledge structure in this field, a keyword co-occurrence analysis was conducted using VOSviewer 1.6.19. The co-occurrence threshold was set at 10, yielding 116 high-frequency keywords out of a total of 2863. After merging synonyms and standardizing terms, 101 keywords were retained for analysis. Based on the modularity optimization method of the Louvain algorithm, these keywords were classified into five thematic clusters according to semantic similarity. Each cluster was marked with a distinct color, thereby generating a well-structured knowledge network (Figure 8).

• Cluster 1: Green Infrastructure and Climate Adaptation

This cluster primarily includes keywords such as green infrastructure, climate change, air pollution, and urban heat island, reflecting the critical role of green infrastructure in addressing climate change and environmental risks. Related studies highlight its environmental regulatory functions, including mitigating the urban heat island effect, improving air quality, and regulating urban temperatures, while also emphasizing its strategic importance in urban renewal and sustainable development. Methodologically, the application of remote sensing, modeling, and risk assessment tools has become increasingly prevalent, enabling more precise quantification of the contributions of green infrastructure to climate adaptation [56].

• Cluster 2: Public Health and Well-being

This cluster centers on keywords such as urban green space, health, public health, mental health, and physical activity, underscoring the close relationship between green space and public health. A substantial body of research demonstrates that green spaces significantly enhance residents’ physical and mental health by promoting physical activity, alleviating psychological stress, and improving social interaction environments. Meanwhile, environmental justice has emerged as a key topic in this domain, with scholars stressing disparities in accessibility and usage rights of green spaces among different social groups, and calling for health equity to be fully addressed in green space planning. Particularly in the context of the COVID-19 pandemic, the health benefits and social value of green spaces have become increasingly evident, positioning them as vital resources for cities in responding to public health challenges.

• Cluster 3: Quality of Life and Perception

This cluster includes keywords such as quality of life, sustainability, perception, urban park, and landscape, highlighting the cultural value and socio-psychological effects of green spaces. Research emphasizes that green spaces not only enhance residents’ life satisfaction and happiness but also strengthen place attachment and social cohesion, thereby improving overall urban livability. Importantly, this cluster addresses differences in the perception and use of green spaces across social groups. Methodological approaches have also expanded, evolving from traditional surveys to big data and social media–based information mining, reflecting increasingly diverse and dynamic perspectives. Consequently, the value of green spaces has extended beyond tangible ecological benefits to encompass psychological, cultural, and social dimensions.

• Cluster 4: Ecosystem Services and Biodiversity

This cluster centers on keywords such as ecosystem service, biodiversity, management, and framework, underscoring the centrality of ecosystem services and biodiversity in green space research. Studies not only focus on material services such as air purification, climate regulation, and water resource management but also increasingly address non-material services such as spiritual well-being and cultural identity. At the same time, green spaces are regarded as critical carriers for biodiversity conservation, with ecological connectivity and functional diversity attracting significant scholarly attention.

• Cluster 5: Urbanization and Planning Challenges

This cluster is associated with keywords including urbanization, urban planning, land use, sustainable cities, and city, reflecting the pressing need to protect and plan green spaces amid rapid urbanization. As urban construction land continues to expand, green spaces face growing spatial conflicts and utilization pressures. Thus, balancing urban development with ecological conservation has become a key issue. Research highlights the importance of integrating green space into comprehensive urban planning and land use policies to promote the coexistence of compact city development and green ecosystems. Against the backdrop of climate change and social risks, resilience-building has emerged as a new agenda in green space research. Here, GIS, spatial modeling, and related technologies are widely applied to provide scientific evidence for sustainable urban planning.

In summary, the five clusters collectively construct a thematic framework across five dimensions—climate adaptation, public health, quality of life, ecosystem services, and urban planning—reflecting the multidimensional coupling of nature–health–society–governance. Future research should further integrate the ecological, health, and planning dimensions to advance both the theoretical depth and practical transformation of sustainable healthy city development.

3.7. Thematic Evolution and Trend Analysis

To reveal the thematic evolution and future trends in the research field of urban green space and sustainable healthy cities, we employed the Bibliometrix package (R) to conduct a time-series visualization of author keywords from the core literature, producing both a keyword heatmap (Figure 9) and a thematic trend map (Figure 10). The heatmap illustrates changes in keyword frequency over time, with darker colors representing higher frequencies. The thematic trend map integrates the time of first appearance, duration of activity, and intensity of frequency to depict the temporal dynamics and evolutionary pathways of research themes.

As shown in the keyword heatmap (Figure 9), the thematic landscape of urban green space and sustainable healthy city research demonstrates clear chronological evolution. Between 2003 and 2017, keyword distribution was relatively scattered with generally low intensity, and the research focus centered mainly on foundational themes such as sustainable development, green space, and ecosystem services. Since 2018, keyword intensity has increased significantly, with research themes becoming more focused and diversifying in scope. After 2020, driven by global public health events (e.g., COVID-19) and rising urban health concerns, high-frequency and high-intensity keywords such as COVID-19, public health, environmental justice, and urban sustainability have emerged. This indicates a clear shift in research hotspots toward integrated directions encompassing health, resilience, and equity.

Thematic trend analysis (Figure 10) further reveals the evolutionary trajectory of research themes and the shifting academic focus in this field over the past decade. Along the timeline, early themes were dominated by ecological and spatial terms such as spatial distribution, species richness, sprawl, and open space. After 2018, topics such as urban sustainability, ecosystem services, and green infrastructure gradually emerged as research hotspots and have continued to attract sustained attention. Since 2020, keywords reflecting urban resilience, health, well-being, and digital technologies—such as health, remote sensing, and machine learning—have appeared with increasing frequency, indicating that the field is becoming deeply integrated with smart technologies and healthy city development. More recently, emerging themes such as pattern, urban greenspace, and machine learning suggest that frontier research is paying greater attention to multi-scale spatial patterns, data-driven approaches, and their applications in evaluating the health effects of urban green spaces.

In summary, research on urban green space and sustainable healthy cities has evolved from an initial focus on ecological conservation toward a more integrated emphasis on health, intelligence, and equity. Future studies may further concentrate on the synergistic effects of urban green space on mental health, social equity, and smart city development, thereby supporting the deeper integration of healthy city initiatives with sustainable development goals.

4. Synthesis and Conceptual Implications

4.1. Structuring the Knowledge Ecosystem: A Data-Driven Framework

Research on urban green spaces spans multiple disciplines, including environmental science, urban planning, public health, and the social sciences, characterized by strong interdisciplinarity and complexity [57]. To assist researchers in quickly grasping the developmental structure and thematic evolution of this field, this section aims to elucidate how the knowledge framework diagram (Figure 11) was systematically derived from bibliometric analysis results, thereby transforming it from a descriptive summary into a data-driven conceptual model. This model divides the domain knowledge into four progressive structural layers, illustrating the evolutionary trajectory of research themes and indicating potential directions for future studies.

(1)

Core Intersection Layer

This layer originates from the high-frequency and strongly interconnected core themes identified in the keyword co-occurrence network. Together, these themes define the central research domains: urban green space, public health, and sustainable cities.

(2)

Research Foundation Layer

The second layer focuses on the knowledge base and developmental trends of the field. This layer directly integrates descriptive statistical results, including publication volume, disciplinary coverage, geographical distribution, and author/institutional influence. Overall, research in this domain has experienced a transition from slow growth to rapid expansion, with a marked increase in publications after 2016, indicating a continuously rising level of scholarly attention. The disciplinary distribution centers on environmental science while extending toward sustainability science, urban studies, and urban planning, reflecting a distinct interdisciplinary character. At the national and institutional levels, China and the United States occupy leading positions, while Europe and Asia exhibit a multi-centered collaborative network. Institutions such as the Chinese Academy of Sciences and Humboldt University have made notable contributions, establishing the foundational driving forces of the field.

(3)

Hotspot Research Layer

In the third layer of analysis, the knowledge base identified through co-citation analysis and the thematic clusters revealed five major core research areas: green infrastructure, public health and well-being, human quality of life and perception, ecosystem services and biodiversity, and planning challenges in the process of urbanization. These clusters collectively represent the current research hotspots within the knowledge structure of the urban green space field.

(4)

Future Trends Layer

The fourth layer of analysis derives from the thematic evolution map (Figure 10) and the burst keyword analysis, which reveal emerging frontier directions such as digitalization, artificial intelligence, social equity, and the systemic transformation of ecological infrastructure. These emerging themes provide guidance for the future practical pathways of the core research domains.

4.2. Future Transformation Trends

Research on the urban ecological environment is transitioning from single-factor analysis to a comprehensive stage characterized by multi-objective, multi-scale, and multi-tool collaboration [58]. Based on the bibliometric analysis results and conclusions of this study, the future development of urban green space research can be advanced in the following four directions (Figure 12).

(1)

Systematic Transformation of Ecological Infrastructure

Urban green infrastructure is entering a new stage of systemic integration and cross-scale coordination [59,60]. The research focus is expected to expand from single ecological functions to multidimensional integrated benefits, including climate regulation, water resource management, biodiversity conservation, and public health promotion [61]. A key task lies in exploring the organic integration of green infrastructure with urban systems such as transportation networks, building systems, and public spaces, thereby constructing resilient and multifunctional ecological networks. At the same time, biodiversity conservation should be incorporated into urban planning frameworks, ensuring continuity of landscape and ecological processes through the establishment of ecological corridors and the restoration of local species. This approach will facilitate the transformation of green spaces from landscape elements into core components of urban systems [62].

(2)

Deep Integration of Social Equity and Human-Centered Values

The distribution and accessibility of green spaces embody the core issues of social equity. Future research will place greater emphasis on equitable access to green resources for vulnerable groups, the evaluation of environmental justice, and the construction of resource allocation models for sustainable development, thereby promoting a fair distribution of ecological benefits among different social groups [63]. At the same time, urban design principles are evolving from ecological restoration toward social inclusion and the promotion of mental well-being. Green spaces are increasingly recognized as vital vehicles for enhancing quality of life and strengthening community cohesion. Their health-promoting effects should be incorporated into public health systems, fostering an ecologically based urban structure centered on human well-being and care.

(3)

Technology-Driven Ecological Governance

The rapid advancement of digitalization and artificial intelligence provides new opportunities for urban ecological governance [64]. The integration of remote sensing, big data analytics, and geographic information modeling enables ecosystem forecasting, dynamic monitoring, and decision optimization [65,66]. The fusion of deep learning and spatial modeling is reshaping the configuration of green infrastructure, while digital twin platforms and ecological monitoring systems within the framework of smart cities are promoting the refinement and intelligent management of green spaces [67]. This trend will significantly enhance the responsiveness and service capacity of urban ecosystems.

(4)

Deepening Climate Adaptation and Sustainable Transformation

Against the backdrop of climate change and the increasing frequency of extreme events, urban green spaces, as a form of Nature-based Solutions (NbS), are becoming a key component in enhancing urban climate resilience [68,69]. Future research should focus on quantifying the comprehensive benefits of different types of green spaces in regulating thermal environments, managing stormwater runoff, and improving air quality, as well as exploring their integrative roles in disaster prevention and mitigation, carbon sequestration, and ecological security systems. The development of green spaces is shifting from environmental restoration toward serving as core infrastructure that supports low-carbon development and long-term resilience, highlighting the strategic role of ecosystems in sustainable urban transformation.

In summary, future urban ecological research should move beyond concerns limited to the quantity or technological aspects of green spaces and place greater emphasis on building systemic resilience and responding to societal needs. Achieving this goal requires strengthening interdisciplinary collaboration by integrating knowledge from ecology, urban planning, sociology, and data science, thereby promoting the practical application of research outcomes and providing theoretical foundations and policy guidance for the creation of sustainable, human-centered urban ecosystems.

4.3. Challenges and Limitations

Although the aforementioned research trends demonstrate promising prospects, multiple challenges remain in advancing the integration of urban green space research and its practical application.

A significant gap persists between methodological innovation and practical implementation. Despite continuous progress in digitalization, artificial intelligence, and system modeling, the translation of these technological achievements into planning and governance practices remains constrained by methodological disparities and the lack of standardized frameworks across disciplines [70]. On the one hand, different research fields often lack systematic theoretical foundations and comparable evaluation indicators; on the other hand, some research outcomes are insufficiently applied at the policy level, exhibiting limited operability and adaptability [71].

The long-term and uncertain nature of urban and environmental dynamics increases the complexity of research. Climate change, social transformation, and urban expansion are continuous and unpredictable processes, yet existing studies often focus on short-term effects or localized case studies, lacking long-term monitoring and dynamic evaluation mechanisms. This not only undermines the continuity of research outcomes but also limits the ability to anticipate changes in urban ecosystems.

To address these challenges and enhance the practical value of research, it is imperative to establish interdisciplinary collaboration and knowledge-sharing mechanisms, and to develop comprehensive indicator systems that balance scientific rigor with practical applicability. Furthermore, cooperation between research institutions and policymakers should be strengthened to develop evidence-based urban ecological decision-making systems, while gradually improving long-term monitoring and data-sharing platforms. Public participation in the monitoring and governance of green spaces should also be encouraged, fostering citizen science and environmental education [72]. Through these measures, research outcomes can be more effectively translated into practice, bridging the gap between theoretical inquiry and urban governance, and ultimately enhancing the real-world impact of urban green space research [73,74].

5. Conclusions

Over the past two decades, research on urban green spaces has undergone remarkable growth and expansion, a trend closely linked to the rise in the global sustainable development agenda, climate action initiatives, and the concept of healthy cities. The widespread use of remote sensing data, machine learning, and open science tools has greatly enhanced the operational feasibility and spatial scalability of research, facilitating the shift in green space studies from local experiences to global comparative analyses. This transformation has provided new technological support for understanding the complexity of urban ecosystems.

With the increasing number of studies and expanding disciplinary participation, urban green space research has gradually evolved into a knowledge structure that interweaves ecological science, urban planning, and the social sciences. This cross-disciplinary integration has driven a shift in research perspectives—from the “optimization of the natural environment” toward the “co-evolution of society and ecosystems.” Scholars have moved beyond focusing solely on the ecological benefits of green spaces to exploring their roles in health promotion, social inclusion, spatial justice, and urban planning. This expansion of perspective signifies a paradigm shift from the analysis of singular ecological functions to a comprehensive framework that emphasizes the interactions within socio-ecological systems.

Within this evolving intellectual context, the present study proposes an integrative framework highlighting the interactive effects among four dimensions—technological, ecological, social, and institutional. It identifies key directions for future research, particularly in advancing interdisciplinary integration and establishing long-term, dynamic evaluation mechanisms. This framework provides a theoretical foundation for a deeper understanding of the role of green spaces in sustainable and healthy cities, offering evidence-based insights for urban planning, health promotion, and ecological governance, and contributing to a more scientific and human-centered urban green transition.

Although this study employs bibliometric and visualization methods to systematically reveal the knowledge structure and evolutionary trends of global research on urban green spaces and urban forests, certain limitations remain. The data used in this study rely solely on the Web of Science (WoS) Core Collection. While WoS is characterized by rigorous quality control and a standardized citation system that ensure data reliability and comparability, its coverage is primarily focused on leading English-language journals. This may result in geographic and linguistic biases due to its relatively limited inclusion of regional, localized, and non-English literature.

Future research can further enhance robustness and interpretability by integrating multiple data sources such as Scopus, JSTOR, and CNKI, and by conducting cross-database comparisons and sensitivity analyses to verify the consistency and reliability of conclusions. Moreover, the incorporation of multilingual literature and text-mining techniques could facilitate the construction of a more inclusive and dynamic knowledge system, thereby deepening our understanding of the evolutionary mechanisms underlying global urban ecological research.