Ecosystem Services in Urban Blue-Green Infrastructure: A Bibliometric Review

Abstract

Urban blue-green infrastructure (UBGI) is a comprehensive solution that balances environmental, social, and economic development objectives and has emerged as a critical approach for fostering urban resilience and sustainable development. This paper conducts a systematic bibliometric analysis of 975 academic articles published between 2000 and 2023 in the Web of Science Core Collection, focusing specifically on the ecosystem services associated with UBGI. Employing CiteSpace visualization technology, this study elucidates the major research trends, thematic clusters, and international collaboration patterns shaping this field. The research delves into the diverse range of ecosystem services provided by blue-green infrastructure and analyzes their contributions to urban well-being. Findings indicate that regulatory services—particularly climate regulation, biodiversity enhancement, and water resource management—have become central research foci within the contexts of urban green infrastructure (UGI), urban blue infrastructure (UBI), and UBGI. Co-citation and keyword analyses reveal that nature-based solutions, hybrid green–gray infrastructure, and the application of urban resilience frameworks are gaining increasing scholarly attention. By summarizing the evolutionary trajectory and priority directions of UBGI research, this study provides significant insights for future interdisciplinary research aimed at enhancing the supply of urban environmental ecosystem services.

1. Introduction

Urban environments worldwide are facing unprecedented challenges due to rapid urbanization, climate change, and declining ecological health. To address these issues, urban planners and policymakers are increasingly turning to innovative and integrated solutions [1,2]. Urban blue-green infrastructure (UBGI) is considered a critical structural facility for nature-based solutions that increase urban resilience by providing multiple ecosystem services [3,4]. Among them, UBGI—comprising urban blue infrastructure (UBI) and urban green infrastructure (UGI)—has gained recognition as a sustainable alternative to conventional infrastructure systems [5], and is a vital component of sustainable urban planning and urban ecosystems. UBI encompasses all water bodies within a city, whether natural or artificial, flowing or static [6], that provide essential ecosystem services supporting urban functioning and sustainable development. UGI encompasses green spaces such as forests, parks, wetlands, lawns, green roofs, and urban forests. These systems form interconnected ecological networks vital for urban biodiversity and human well-being [7,8]. Although UBI and UGI consist of different components, growing evidence suggests their ecosystem services and spatial configurations may be interrelated and mutually reinforcing [9]. Consequently, recent studies increasingly examine UBI and UGI as an integrated system, investigating their combined environmental benefits and public services [3,10]. This study analyzes urban infrastructure through the integrated UGBI framework, whose core developmental logic lies in synergistic green-blue element interactions. These interactions create mutually reinforcing service provisions and spatial configurations [11] that simultaneously address environmental challenges, enhance ecosystem services, and sustainable enhance residents’ health and well-being within urban support systems [12].

The concept of ecosystem services offers a valuable theoretical framework for understanding how UBGI fosters health and well-being [13]. According to the 2005 Millennium Ecosystem Assessment, the ecosystem services refers to the benefits that humans can derive from natural ecosystems. These include provisioning, regulating, cultural, and supporting services [14]. UBGI has predominantly addressed regulating services (e.g., climate modulation, water cycle management) and provisioning services (e.g., water provision, food resources). Contemporary scholarship increasingly recognizes cultural services, evidencing UBGI’s contributions to mental well-being, landscape aesthetics, and environmental education [15].

The provisioning services of UBGI encompass food security, water provision, energy access, and poverty reduction [16]. The synergistic integration of UBI and UGI optimizes the combined benefits of their respective technologies and ecosystem services [17]. This integration not only sustains natural hydrological cycles but also enhances flood resilience through coordinated interactions with conventional gray infrastructure [3,18] as a sustainable and cost-efficient alternative [19]. UBGI has been evidenced to provide adaptive responses and regulating services for both acute climatic perturbations—including storm surges, and heatwaves—and persistent environmental pressures such as elevated atmospheric CO₂, deteriorating air, water quality, and biodiversity degradation [20]. Vegetation and water bodies mitigate urban heat through evapotranspiration and shading, reducing ambient temperatures [21] and consequently alleviating the urban heat island effect [22]. Through its high thermal inertia, evapotranspiration processes, and albedo modification capabilities, UBGI effectively modulates microclimatic conditions, achieving measurable temperature reductions of 1.7–3.4 °C during extreme heat events [23]. These characteristics establish UBGI as a viable nature-based cooling mechanism for urban heat stress adaptation [5].

Cultural services offer aesthetic, recreational, and biodiversity-related benefits [24]. Numerous studies confirm that blue-green spaces can lower blood pressure, reduce obesity, enhance psychological resilience, alleviate social isolation, and improve social cohesion [25,26]. A review by Georgiou et al. highlighted that blue spaces contribute to human health by influencing environmental factors, such as improving PM2.5 concentrations, enhancing air quality, and boosting subjective perceptions of regional ecological quality [27]. Urban agriculture, orchards, and green spaces can contribute to the provision of food and material resources [28], while supporting services such as soil formation nutrient cycling sustain broader ecological functionality. As a nature-based solution (NBS), UBGI serves as a critical foundation for urban ecosystems, supporting biodiversity conservation and ecological network connectivity [29]. Specifically, UBGI can create complex vegetative or aquatic habitats that expand ecological niches, acting as “stepping stones” or corridors for species dispersal while also serving as recreational spaces for urban populations.

Nature-based solutions (NBSs) are widely established as integrated frameworks addressing interconnected socio-environmental challenges: climate change mitigation, biodiversity conservation, and human well-being enhancement [30,31]. NBSs strategically leverage natural processes and ecosystem services to efficiently and adaptively confront these challenges while delivering co-benefits across environmental, social, and economic domains [32,33]. Within urban contexts, UBGI’s networked systems constitute fundamental spatial and technical implementations of NBS principles [34,35]. Through designed protection, restoration, and management of natural/semi-natural urban elements, UBGI harnesses inherent ecosystem functions to directly address urban climate risks, environmental degradation, and public health challenges. NBSs that incorporate blue and green infrastructure have demonstrated effectiveness in enhancing ecological resilience and urban livability [36]. These infrastructures not only deliver environmental benefits but also improve public service provision, social cohesion, and land value [37,38], especially in historic urban areas [39,40] and urban green spaces and wetlands, which can serve as a base for education and scientific research. Despite growing interest from researchers and practitioners, the implementation of blue-green infrastructure remains limited due to complex design requirements, practitioner hesitancy, and performance uncertainties [41,42]. Traditionally, rainwater management relies heavily on gray infrastructure (GREI). However, these traditional GREI systems are increasingly seen as lacking flexibility and efficiency, leading to ecosystem degradation and showing limited hydraulic performance under the pressure of urban growth and climate change [43]. Furthermore, it remains unclear whether current studies sufficiently address multi-scale urban applications of UBGI or are constrained to specific contexts [39].

While numerous reviews address green roofs [39,40], rain gardens [43], and bioretention systems [44,45,46], comprehensive examinations of UBGI remain scarce. Notably, ecological interconnectivity within blue-green systems is frequently underrepresented in the engineering literature. Despite evidence demonstrating its benefits for urban ecosystem resilience and functional enhancement [47], prevailing methodologies remain predominantly qualitative, deficient in bibliometric analysis and knowledge mapping techniques [48]. This limitation constrains holistic understanding of research evolution and emerging frontiers. Compounding this issue, 68% of IPCC-assessed adaptation plans indicate absent UBGI implementation roadmaps [49]. Consequently, our study identifies critical operational priorities to address these gaps.

Addressing these research gaps, this study poses a central question: to systematically reveal the developmental characteristics and future trajectories of UBGI ecosystem services research through bibliometric methods. Accordingly, this study employs bibliometric methods to systematically analyze the UBGI-related literature published between 2000 and 2023, reviewing advancements in ecosystem services and exploring UBGI’s mechanisms for addressing global challenges such as climate change and urbanization. Using visualization and co-citation techniques, the research aims to achieve the following: (1) trace the temporal evolution of UBGI ecosystem services research; (2) identify primary contributing countries, institutions, and scholars; and (3) highlight emerging research clusters and thematic trends. Utilizing CiteSpace 6.3.R1 to construct knowledge mapping and collaboration networks, we conduct comprehensive qualitative–quantitative analysis of UBGI’s four primary ecosystem service domains, addressing methodological limitations and perspective gaps in existing scholarship and establishing a multidimensional analytical framework for enhanced knowledge synthesis—yielding significant theoretical and practical implications.

2. Materials and Methods

2.1. Data Source and Screen Strategy

While recognizing the value of multi-database approaches, the data used in this bibliometric study were extracted from the Science Citation Index Expanded within the Web of Science Core Collection [50]. The reason lies in the optimal balance across three key dimensions: (1) historical coverage, capturing the research evolution of UBGI since its inception; (2) rigorous disciplinary indexing, ensuring analytical precision in this interdisciplinary field; and (3) robust citation tracking capabilities, which are crucial for network analysis. This methodological consistency aligns with mainstream practices in ecosystem services research.

To ensure the comprehensiveness and accuracy of the literature search, this study employed an iterative optimization Boolean search strategy. Initially, broad queries were constructed based on the core concepts. Subsequently, key terms were identified and incorporated through the analysis of high-frequency terms in the preliminary results, manual relevance checks of the literature, citation chaining of high-impact publications, and referencing relevant discipline-specific standard term databases (e.g., MeSH). The core concepts were systematically expanded by including synonyms and closely related concepts of “urban blue-green infrastructure” (e.g., “urban green infrastructure,” “nature-based solutions,” “ecological infrastructure”) and the four major categories of “ecosystem services” along with key specific types (e.g., “provisioning, regulating, cultural, supporting services,” “water resource management,” “biodiversity,” “climate regulation,” “urban heat island”). The iterative optimization based on term citation frequency and thematic relevance ultimately resulted in the final target search term set. The final Boolean search statement was formulated as follows: TS = (“urban blue-green infrastructure” OR “urban blue infrastructure” OR “urban green infrastructure” OR “nature-based solutions” OR “ecological infrastructure”) AND TS = (“ecosystem services” OR “provisioning services” OR “regulating services” OR “cultural services” OR “supporting services” OR “water resources management” OR “biodiversity” OR “climate regulation” OR “urban heat island”).

The search was conducted on 4 November 2024, covering the publication period from 1 January 2000 to 31 December 2023. Only peer-reviewed research articles and review articles were included in the dataset. Our analysis exclusively incorporated peer-reviewed English-language journal articles in the final synthesis. Initially, the query yielded 1074 documents. The titles and abstracts were then manually screened to exclude records that were not related to urban environments or were irrelevant or off-topic. Further filtration was conducted using CiteSpace 6.3.R1, which removed duplicate entries and non-target article types. After this multi-stage refinement, a final dataset comprising 975 documents was retained for bibliometric analysis.

2.2. Bibliometric Analysis

Bibliometric analysis has become a powerful tool for systematically mapping research landscapes, evaluating knowledge structures, and identifying intellectual trends in scientific domains [51]. This method organizes metadata from academic databases into quantifiable units, enabling researchers to uncover hotspots, knowledge gaps, and collaboration patterns. CiteSpace supports scientometric and informetric analyses and is widely used to map co-citation networks, keyword co-occurrence, and collaboration linkages [52,53]. Research dynamics and trends continue to evolve over time. For example, Waseem et al. [54] identified environmental science and SDG 13 (Climate Action) as the dominant fields but did not address the interdisciplinary analysis of UBGI. This study conducts an interdisciplinary bibliometric analysis of the UBGI ecosystem services literature, focusing on a tripartite framework of regulation, supply, and cultural services.

Three primary analytical modules were adopted in this study: (1) collaboration network analysis—to investigate inter-institutional and inter-country collaboration patterns and intensities; (2) co-citation analysis—to identify clusters of highly cited publications, reflecting shared theoretical or empirical frameworks [55]; and (3) keyword co-occurrence analysis—to detect high-frequency and high-centrality terms, indicating emerging themes and evolving research orientations [56]. CiteSpace can reflects clusters of different time periods; the dominant colors of the clusters reveal years that were particularly active and structural holes. We can see in the scientometric analysis how one cluster connects to another almost completely independent cluster in which the literature played a key role in a paradigm shift. Kleinberg proposed an algorithm for detecting frequency bursts in 2002 [57]. If a paper suddenly and rapidly increases in citation frequency, the safest explanation is that the paper touches on a key part of the complex system of the academic field. The application of Kleinberg’s burst detection algorithm in this study serves a dual purpose: it not only identifies temporal spikes in UBGI research keywords (e.g., “biodiversity conservation” in 2013–2015) but also discriminates fashion-driven trends (decaying within 1 year, such as “water management” in 2020).

Citespace’s clustered views include default views and the automatic clustering label view [58,59]. According to the network structure and the clarity of clustering, CiteSpace provides two indicators: the module value (referred to as Q value) and the average silhouette value (referred to as S value), which can be used as the basis for us to judge the effect of graph drawing. Generally speaking, the Q value is generally within the interval (0,1); Q greater than 0.3 means that the community structure is significant. When the S value is above 0.7, the clustering is efficient and convincing; if it is above 0.5, the clustering is generally considered reasonable; and if the S value is infinite, the number of clusters is usually 1, so the selected network may be too small to represent only one research topic [59].

Prior to running these modules, a set of CiteSpace parameters was calibrated, including the following: (1) time slicing (one-year intervals from 2000 to 2023), (2) node type selection (e.g., keyword, author, institution), (3) pruning method (Pathfinder, pruning sliced networks), and (4) threshold settings (e.g., top 50 items per time slice).

Collaboration networks capture the intensity of academic partnerships, co-citation patterns reveal intellectual linkages, and keyword co-occurrence identifies semantic trends. The integration of these analyses provides a multidimensional understanding of the UBGI research landscape. The framework for this methodology is illustrated in Figure 1.

3. Results

3.1. Annual Publishing Trend

A total of 975 publications related to UBGI ecosystem services were published between 2000 and 2023. The temporal distribution of publications reveals three distinct developmental phases (Figure 2).

Phase I (2000–2013): This initial stage was characterized by low research output, with only 0.9% of total publications. A significant publication gap was observed between 2004 and 2011, indicating limited academic attention during this period.

Phase II (2014–2018): This period marked the beginning of steady growth in research interest. Annual publications exceeded ten for the first time, reflecting increased scholarly engagement. Notably, 7 of the 20 most highly cited papers emerged during this phase, laying a foundational base for subsequent expansion.

Phase III (2019–2023): Research activities significantly intensified, accounting for 86.1% of the total publications. Of the 20 most cited articles, 11 were published during this period, reflecting the maturity of the field. This explosive growth period is the result of multiple factors, including policy demands, environmental crises, technological advancements, and interdisciplinary integration. Global attention to climate change and biodiversity loss, particularly after the 2019 UN Climate Summit, elevated the prominent role of national statistical bureaus in urban planning discourse. Following China’s “carbon peak by 2030, carbon neutrality by 2060” target in 2020, blue-green spaces as urban carbon sinks became a research hotspot. The COVID-19 pandemic in 2020 further highlighted the value of accessible urban green and blue spaces for public health and resilience. The surge in UBGI research has been driven by the need to address urban challenges related to the pandemic, emphasizing the role of green and blue spaces in enhancing mental health and providing cultural ecosystem services [60,61].

3.2. Cooperation Network

Analysis of author affiliations revealed that the 975 publications originated from 3512 institutions across 285 countries and regions. The international collaboration network indicates that countries such as the United Kingdom, the United States, Germany, and China are the most prolific contributors. The UK leads with 163 publications, followed closely by the US (153), Germany (153), and China (125). China, as the only developing country in the top group, has experienced rapid urban transformation and environmental pressures, which likely stimulated strong research output (Figure 3).

Countries such as Germany, The United Kingdom, the Netherlands [62], and Australia focus on researching complex UBGI systems, including floating communities, SUDS multi-objective optimization, and decentralized stormwater management. Although these technologies are advanced, their high costs present barriers to widespread implementation. In contrast, Southeast Asian countries like the Philippines, Vietnam, and Indonesia, which face urgent needs, have innovated local solutions such as community-based rainwater harvesting cooperatives and mangrove–dyke hybrid systems [63]. However, these countries experience severe research marginalization, with their UBGI publications accounting for less than 6% of the global total, and 90% of their research relies on international collaboration.

In terms of ecosystem service categories, UGI-related studies accounted for 368 papers (37.7%), UBI for 32 papers (3.3%), and UBGI for 271 papers (27.8%). Research focused predominantly on regulating services, particularly climate regulation, biodiversity, and water management. UGI studies were most abundant in regulating services (266 papers), followed by cultural (42), provisioning (35), and supporting services (25). UBI studies primarily addressed regulating services (32), while UBGI studies showed similar patterns: regulating (210), cultural (23), provisioning (20), and supporting services (18). The increasing emphasis on cultural and valuation-oriented studies since 2020 reflects a broadening scope of inquiry.

The top contributing institutions include the Helmholtz Association (43 papers), Humboldt University of Berlin (33), Wageningen University & Research (32), Helmholtz Centre for Environmental Research (30), French National Centre for Scientific Research (28), and Chinese Academy of Sciences (26).

The concentration of leading institutions in Germany and Sweden, along with growing contributions from China, highlights the global distribution and significance of UBGI research. Figure 4 illustrates the collaborative relationships among countries. Node size indicates the number of publications, while line thickness denotes the strength of international cooperation. A prominent example is the strong collaboration between Germany and France (purple cluster), reflecting a well-integrated European research network.

3.3. Keyword Co-Occurrence Analysis

Keyword co-occurrence analysis was conducted using CiteSpace, with “keyword” set as the node type and a one-year time slice from 2000 to 2023. The threshold was set to k = 5. The resulting network (Figure 5) reveals keywords of high frequency and centrality, highlighting research hotspots and emerging areas.

The top keywords by frequency were “ecosystem services” (342 occurrences), “nature-based solutions” (334 occurrences), “biodiversity” (254 occurrences), “green infrastructure” (175 occurrences), and “climate change” (172) (

Table 1. High-frequency keywords in UBGI ecosystem service research (2000–2023), sorted by count and centrality.

Rank	Keywords (by Frequency)	Count	Centrality	First Appearance
1	Ecosystem services	342	0.13	2013
2	Nature-based solutions	334	0.11	2016
3	Biodiversity	254	0.3	2012
4	Green infrastructure	175	0.18	2013
5	Climate change	172	0.26	2014
6	City	153	0.19	2012
7	Management	148	0.09	2013
8	Conservation	92	0.09	2014
9	Urban green infrastructure	85	0.05	2016
10	Framework	84	0.15	2015

, tAB). The highest-ranking keywords by intermediary centrality—which reflects their bridging role in the research network—were “carbon” (centrality = 0.32), “biodiversity” (centrality = 0.30), “soil” (centrality = 0.30), “climate change” (centrality = 0.26), and “city” (centrality = 0.19) (

Table 2. High-centrality keywords in UBGI ecosystem service research (2000–2023), sorted by count and centrality.

Rank	Keywords (by Centrality)	Count	Centrality	Appearance
1	Carbon	11	0.32	2021
2	Biodiversity	254	0.3	2012
3	Soil	7	0.3	2003
4	Climate change	142	0.26	2014
5	City	153	0.19	2012
6	Green infrastructure	175	0.18	2013
7	Framework	84	0.15	2015
8	Land use	40	0.14	2014
9	Ecosystem services	342	0.13	2013
10	Nature-based solutions	334	0.11	2016

). The prominence of “carbon” suggests an increasing research interest in carbon-related ecosystem services, including carbon storage [64]. The frequent and central role of terms such as “soil,” “city,” and “climate change” indicates a convergence toward sustainability-oriented, urban-scale research integrating ecological processes and policy relevance.

3.4. Most Frequently Cited Literature

A co-citation analysis was conducted to identify the foundational literature shaping the development of UBGI research. Thirteen key publications were cited more than 40 times, indicating their significant influence within the academic discourse (Figure 6;

Table 3. Most highly cited studies related to UBGI.

ID	Title	Author	Source	Citation Count	Centrality	Type
1	“Understanding the value and limits of nature-based solutions to climate change and other global challenges”	Seddon [65]	Philosophical Transactions of the Royal Society B	93	0.06	Review
2	“The science, policy and practice of nature-based solutions: An interdisciplinary perspective”	Nesshöver [66]	Science of the Total Environment	81	0.15	Article
3	“Core principles for successfully implementing and upscaling Nature-based Solutions”	Cohen-Shacham [67]	Environmental Science & Policy	77	0.05	Review
4	“A framework for assessing and implementing the co-benefits of nature-based solutions in urban areas”	Raymond [35]	Environmental Science & Policy	66	0.08	Article
5	“Summary for policymakers of the global assessment report on biodiversity and ecosystem services of the Intergovernmental Science-Policy Platform on Biodiversity and Ecosystem” Services	Bongaarts [68]	Population & Development Review	62	0.01	Article
6	“Seven lessons for planning nature-based solutions in cities”	Frantzeskaki [69]	Environmental Science & Policy	57	0.06	Review
7	“Nature-Based Solutions in the EU: Innovating with nature to address social, economic and environmental challenges”	Faivre [70]	Environmental Research	57	0.36	Article
8	“Getting the message right on nature-based solutions to climate change”	Seddon [71]	Global Change Biology	53	0.06	Article
9	“The superior effect of nature-based solutions in land management for enhancing ecosystem services”	Keesstra [72]	Science of the Total Environment	44	0.04	Article
10	“Nature-based solutions to climate change mitigation and adaptation in urban areas: Perspectives on indicators, knowledge gaps, barriers, and opportunities for action”	Kabisch [73]	Ecology&Society	43	0.03	Article
11	“Mapping the effectiveness of nature-based solutions for climate change adaptation”	Chausson [74]	Global Change Biology	41	0.03	Article
12	“Nature-Based Solutions for Europe’s Sustainable Development”	Maes [29]	Conservation Letters	41	0.01	Article
13	“Nature-based solutions to address global societal challenges”	Cohen-Shacham [75]	Nature-Based Solutions	40	0.04	Article

). In the existing literature analysis framework, the relationship between NBSs and UBGI is primarily reflected in the integration of concepts and practical applications. From a theoretical perspective, an NBS provides systematic design concepts and methodological support for UBGI, particularly in urban environmental applications. Typical NBS technical elements, such as green roofs, urban forests, and ecological water management systems, essentially form the core components of UBGI. These nature-based engineering measures are systematically integrated into urban development strategies through spatial planning, not only enhancing the ecosystem services of cities but also significantly improving the sustainability and climate resilience of urban environments. It is worth noting that while some of the literature does not explicitly use the term UBGI, the research content has substantively covered the specific forms of NBS applications in urban spaces.

The most frequently cited work is by Seddon et al. [65], with 93 citations and a centrality value of 0.06. The article explores the value and limitations of NBSs in addressing climate change and other global environmental challenges while emphasizing the need for evidence-based implementation strategies. The high citation frequency reflects its pivotal role in bridging ecological science and climate policy.

Following closely, Nesshöver et al. [66] (81 citations, centrality = 0.15) offer an interdisciplinary overview of the science, policy, and practice of NBSs. Their work defines conceptual linkages between NBSs, sustainability science, and urban governance, laying a theoretical foundation for integrating NBSs into urban infrastructure systems. Other frequently cited contributions include Cohen-Shacham et al. [67], who articulate guiding principles for scaling NBSs in diverse urban contexts; Raymond et al. [35], who propose an evaluative framework for assessing co-benefits of NBSs in urban environments; as well as Frantzeskaki [69] and Faivre et al. [70], who advance strategic planning and policy integration for NBSs, particularly within the European Union.

Several of these works emphasize the synergistic potential between UBGI and NBS, viewing UBGI not only as a physical infrastructure system but also as an operational arm of the broader NBS paradigm. For example, Keesstra et al. [72] demonstrate the comparative effectiveness of NBSs in delivering multifunctional ecosystem services, including carbon sequestration and hydrological regulation. Similarly, Kabisch et al. [73] and Chausson et al. [74] evaluate the challenges, knowledge gaps, and metrics for climate adaptation through nature-based urban design.

Collectively, these high-impact publications reflect a shift in UBGI research toward transdisciplinary, systems-oriented thinking. Co-citation mapping reveals strong intellectual cohesion around themes such as climate resilience, biodiversity enhancement, and socio-ecological integration. Furthermore, the alignment between frequently cited studies and recent keyword bursts—such as “biodiversity conservation,” “climate change,” and “urban resilience”—highlights the dynamic interplay between theoretical advancement and practical application in UBGI research.

3.5. Cluster Analysis

Co-citation analysis is a powerful method for identifying the internal structure and intellectual foundations of a research field. In this study, clusters of frequently co-cited references were generated using CiteSpace to visualize thematic convergence and divergence. These clusters reveal not only the core concepts of UBGI ecosystem services but, more importantly, the key themes, theories, methods, or application contexts that are closely related to the core concepts and collectively support the development of the field. Each node in the network represents a cited article, with node size reflecting citation frequency. Links between nodes indicate co-citation relationships, and clusters are color-coded and numbered based on modularity. CiteSpace’s clustering label extraction algorithms—Latent Semantic Indexing (LSI), Log-Likelihood Ratio (LLR), and Mutual Information (MI)—were evaluated, with LSI selected for its higher alignment with practical research semantics.

Figure 7 illustrates the resulting cluster map, and

Table 4. Major co-citation clusters identified through CiteSpace, based on the Latent Semantic Indexing (LSI) method.

Number	Cluster	Size	Silhouette	Representative Themes (LSI)
#0	Nature-Based Solution	60	0.871	Nature-based solutions; climate change resilience; urban water; wastewater treatment; innovation systems; green infrastructure; ecosystem services; green space governance; boundary objects; natural risks
#1	Ecosystem Services	47	0.97	Ecosystem services; green infrastructure; nature-based solutions; green space governance; boundary objects; urban green infrastructure; provisioning ecosystem services; edible plants; cultural ecosystem services; urban gathering
#2	Green Infrastructure	34	0.982	Green infrastructure; social ecological systems; urban green space; lay-people comparison; lawn vegetation; lawn vegetation; urban meadow; biotope type mapping; patch connectivity
#3	Climate Change Adaptation	33	0.878	Nature-based solutions; climate change adaptation; ecosystem-based adaptation; biodiversity conservation; ecosystem health; climate change; systematic map
#5	Urban Planning	20	0.994	Ecosystem function; tree planting; experimental restoration

summarizes the top five clusters, including their thematic labels, size, and representative keywords.

3.5.1. Cluster 0: Nature-Based Solution

Cluster 0 is the largest cluster, comprising 60 co-cited documents. High-frequency keywords include “nature-based solutions,” “green infrastructure,” “climate change resilience,” “urban water,” and “ecosystem services.” The central theme revolves around the strategic use of NBSs for regulating ecosystem services in urban environments.

Key contributions include Seddon et al. [65], which highlights the opportunities and political appeal of NBSs in climate mitigation and adaptation; Nesshöver et al. [66], presenting an interdisciplinary synthesis of science, policy, and practice dimensions of NBS; as well as Raymond et al. [35] and Faivre et al. [70], who propose frameworks for assessing co-benefits and integrating NBSs into EU innovation policy. This cluster emphasizes the growing recognition of the NBS as a central framework for UBGI planning and the operational synergy between ecological systems and urban infrastructure. Wang et al. [76] proposed that the remarkable effect of hydrometeorological factors (such as MHR and TDR) confirms the complex relationship between rainfall patterns and flood risks and emphasizes the urgency of incorporating future climate forecasts into urban recovery plans.

3.5.2. Cluster 1: Ecosystem Services

Cluster 1 contains 47 documents and focuses on the application of the ecosystem services framework to urban environments. Extracted terms include “urban green infrastructure,” “green space governance,” “provisioning ecosystem services,” and “cultural ecosystem services.”

The most cited study in this cluster is by Kremer et al. [77], which conducts a comparative analysis of urban biodiversity and ecosystem services across seven global cities. The cluster also includes Norton et al. [78], who proposed a prioritization framework for urban heat mitigation through green infrastructure. Regarding cultural ecosystem services—defined as non-material benefits derived from ecosystems [79,80]—Hartig et al. [81] demonstrated their psychological benefits via urban biodiversity. Distinct from other ecosystem services, cultural services exhibit strengthened significance with national economic development [82], consequently informing landscape planning policy formulation [83]. However, this elevated policy priority does not necessarily translate into physical expansion of green infrastructure. Global empirical studies reveal that Gross National Product (GNP) growth over the past four decades has frequently coincided with ecological land loss. As demonstrated by Seto et al. [84], urban expansion consistently consumes green spaces, highlighting the fundamental disconnect between policy advocacy and economic practice. This paradox stems primarily from the exclusion of ecosystem service valuation from national accounting systems [85], which perpetuates decision-making dominated by conventional GDP-growth paradigms. This cluster integrates urban planning paradigms with ecological valuation methodologies, progressively incorporating socio-cultural valuations of UBGI as a critical dimension.

3.5.3. Cluster 2: Green Infrastructure

Cluster 2 includes 34 co-cited articles centered around “urban green space,” “social ecological systems,” and “lawn vegetation.” The main theme is the perception, functionality, and integration of green infrastructure in urban design. The key article in this cluster is by Hofmann et al. [86], which assesses public perceptions of urban parks and derelict lands, underscoring the planning relevance of informal green spaces. Fischer et al. [87] revealed significant trait divergence between successful and failed target species in urban brownfield grassland restoration, demonstrating that high competitive capacity is critical for successful species establishment. Opdam et al. [88] proposed the concept of ecological networks as an appropriate basis for incorporating biodiversity conservation into sustainable landscape development. All top-cited works in this cluster focus on the regulating services of specific green infrastructure types and their empirical validation. Compared to other clusters, this one is more case-specific and grounded in site-level assessments and public perception studies.

3.5.4. Cluster 3: Climate Change Adaptation

Comprising 33 documents, Cluster 3 explores the use of UBGI for ecosystem-based adaptation. Representative keywords include “biodiversity conservation,” “climate resilience,” “ecosystem health,” and “systematic mapping.” This cluster places strong emphasis on the role of the NBS in addressing biodiversity loss and climate change. The most cited paper is by Qi et al. [89], which discusses China’s international role in advancing NBSs through multilateral environmental governance. Girardin et al. [90] propose that nature-based solutions can play a powerful role in long-term temperature reduction. Świerkosz et al. [91] define the scope of an NBS, which is crucial for decision-makers on how to choose solutions that can be defined as an NBS. Cluster 3 can be seen as a more targeted extension of Cluster 0, with greater focus on specific regulatory outcomes such as species conservation and resilience.

3.5.5. Cluster 5: Urban Planning

Cluster 5 includes 20 papers and is primarily concerned with practical urban interventions such as “tree planting,” “experimental restoration,” and “ecosystem function.” It aligns with applied urban planning perspectives on green and blue infrastructure implementation. The most cited work is by Bowler et al. [92], which uses a systematic review to evaluate the temperature-regulating effects of urban greening interventions (e.g., parks, trees, and green roofs). Other studies explore the capacity of greening strategies to enhance urban livability, environmental quality, and public health. This cluster illustrates the translational bridge between ecological theory and design practice. Ecological theory and engineering practice are integrated with each other. For example, canopy shading models inform street tree layouts to deliver urban cooling services; whereas hydrological regulation theory guides rain garden design while field monitoring data refine the theory. This synergy exemplifies evidence-based ecological design.

3.6. Keywords with the Strongest Citation Bursts

In addition to co-citation and cluster analysis, keyword burst detection provides insights into the temporal dynamics of research trends. CiteSpace’s citation burst function identifies terms that have experienced a significant surge in academic attention during specific time intervals. These bursts reflect emerging research priorities and evolving thematic shifts in the field.

Figure 8 presents the top 12 keywords with the strongest citation bursts based on burst intensity and duration (γ = 1). The visualization reveals both long-standing and recently emerging research hotspots. The keyword with the highest burst strength and longest duration was “biodiversity conservation”, which remained a dominant theme from 2013 to 2019. This sustained attention reflects increasing global concern over biodiversity loss, particularly in the context of rapid urbanization [93]. UBGI has been increasingly recognized for its capacity to deliver diverse ecosystem services and support ecological sustainability. Other high-burst keywords include “landscapes,” “ecological infrastructure,” and “carbon storage”, indicating a strong focus on ecosystem service quantification and integration into spatial planning; “plant diversity” and “physical activity”, signifying growing interest in the intersection of ecological health and human well-being; as well as “services” and “land surface temperature”, highlighting the relevance of climate-related metrics in UBGI assessments.

Notably, “nature-based solutions” and “water management” have emerged as recent burst terms since 2021, suggesting a paradigm shift toward integrated, multifunctional strategies in urban resilience and infrastructure design. Accurate and reliable flow estimation is crucial for effective water resource management, especially in mitigating extreme climatic events such as drought and floods [94]. The NBS, in particular, has gained momentum as a comprehensive framework that blends ecological systems with engineering interventions, often referred to as “blue-green-gray” infrastructure [95]. In urban water management, UBGI systems are now being systematically incorporated into mainstream planning rather than being treated as supplementary or experimental strategies [96]. In 2020, global flood losses surged by 215% (EM-DAT data) [97], driving the outbreak of emergency research; After 2021, the focus shifted to implementation cases, with a decline in basic research but a surge in the applied literature. The water management keyword is replaced by a subdivision term. Green and blue spaces, including permeable landscapes and retention basins, play a pivotal role in alleviating pressure on stormwater systems and restoring natural hydrological cycles. The growing burst intensity of “physical activity” reflects the health co-benefits of UBGI, particularly in light of the COVID-19 pandemic. Recent research has underscored the role of urban green and blue spaces in promoting outdoor activity, mental well-being, and physiological health [98,99]. For example, street tree canopy cover has been associated with reduced incidence of asthma and dementia [100,101], while forest exposure has been shown to enhance immune response [102]. The emergence of these keywords signals a shift from infrastructure-focused studies to a more holistic evaluation of UBGI as a multifunctional urban system. The convergence of ecological, climatic, and public health concerns positions UBGI as a critical research frontier in urban sustainability science.

4. Discussion

This study systematically analyzed 975 scholarly publications on UBGI ecosystem services from 2000 to 2023, utilizing bibliometric and visualization methods. The results reveal not only the evolution of this research field but also the emerging themes and structural dynamics that have shaped its development.

A key finding is the temporal segmentation of UBGI research into four distinct phases, with an explosive increase in publication volume after 2020. This surge can be attributed to the escalating urgency of climate change, urban resilience planning, and, more recently, the COVID-19 pandemic, which emphasized the importance of accessible and multifunctional urban green-blue spaces for public health.

4.1. Geographical and Institutional Trends

The bibliometric analysis identified the United Kingdom, Germany, the United States, and China as the primary contributors to UBGI research. The dominance of European countries—particularly Germany and the UK—can be attributed to their early policy initiatives on NBSs and sustainable urban planning. Germany’s leadership aligns with its national and EU-level environmental directives, including pilot programs for climate-adaptive infrastructure. In contrast, China’s rising contribution reflects its growing emphasis on UBGI as part of the “sponge city” initiative and broader ecological civilization framework. Since becoming a major advocate of NBSs in 2019 [86], China has rapidly expanded UBGI research and practice, particularly in climate resilience, stormwater management, and biodiversity conservation. Institutionally, the Helmholtz Association and Humboldt University lead in publication volume, followed by Wageningen University, the French National Centre for Scientific Research, and the Chinese Academy of Sciences. This widespread distribution highlights the global relevance and collaborative potential of UBGI research.

Different types of UBGI in Asian countries are based on regional agricultural and architectural characteristics [103]. In flood adaptation applications of UBGI, Thailand’s Pak Nam Pran Buri case [104]—featuring community-led water conservation initiatives (community participation networks)—and Yemen’s Ibb City case [105]—utilizing a four-dimensional water security index (multidimensional assessment framework) covering drinking water and disaster management—collectively demonstrate critical implementation pathways for Global South regions. In African countries, policies for blue-green solutions vary by region, focusing on ecology, climate change adaptation, and biodiversity. However, they share a common goal of promoting economic development and ensuring social equity in access to basic resources. This is exemplified through initiatives such as the creation of green job opportunities [106]. In recent years, there has been an increase in reported UBGI solutions in Europe. In the United Kingdom, water management solutions include permeable sidewalks and reservoirs [107]. Denmark is renowned for its advanced environmental initiatives, with Copenhagen being a prime example as a climate change leader [108]. Notable strategies implemented in Copenhagen include the “C2C-CC Project” and “Soul of Nørrebro.” Furthermore, the academic literature has detailed existing UBGI solutions, such as rainwater roads, street detention, retention avenues, green streets, and central retention areas [109,110]. Germany has implemented various innovative UBGI solutions, including green roofs, bioretention ponds, and water tanks. Engineers continue to propose new designs and solutions, such as the KURAS project, aimed at enhancing Germany’s climate change adaptation capacity [111]. In North America, UBGI is often referred to as Low-Impact Development (LID) or Best Management Practices (BMP). In the United States, an interesting phenomenon has been observed regarding the creation of BGI: as the number of such areas increases, housing costs also tend to rise, potentially leading to reluctance in their creation [112]. Nevertheless, the government has implemented policies to promote UBGI, with the United States having enacted 40 policies, making it one of the countries with the largest number of initiatives globally [113].

4.2. Thematic Clusters and Research Gaps

Co-citation and cluster analyses revealed five dominant research clusters: Cluster 0 centers on NBS frameworks and planning strategies; Cluster 1 focuses on ecosystem service classification and valuation; Cluster 2 emphasizes site-scale green infrastructure studies; Cluster 3 highlights biodiversity and climate adaptation, and Cluster 5 links ecological function with urban planning practices. These clusters demonstrate the multidimensionality of UBGI research, encompassing both conceptual development and applied practice. Notably, profound interdependencies exist among research clusters. Clusters 0 and 5 constitute the strategic planning nucleus, with Cluster 0 providing conceptual foundations that underpin implementation frameworks across other clusters. Cluster 5 operationalizes Cluster 0’s framework by explicitly coupling ecological functions (Clusters 1–3) with planning protocols, policy instruments, and implementation tools—demonstrating inherent integration. Cluster 1 provides value indicators for justifying and prioritizing specific interventions studied in Cluster 2, such as which green infrastructure types provide the best cooling effect per unit cost. Conversely, empirical data on site-scale green infrastructure performance can complement and refine assessment models and classifications.

Significant progress has been made in the ecosystem services of UBGI, but some gaps remain. The lack of quantitative comparability standards for mixed methods of cultural services in this study suggests the use of physical data, social media data, and questionnaire surveys. Moreover, the literature screening reveals a lack of integrated frameworks bridging biophysical processes and social systems theory. At last, the overwhelming majority of empirical research focuses on cities in the Global North, neglecting innovation in cities in the South.

4.3. Emergent Themes and Citation Bursts

Keyword burst analysis reveals a shift from technical and engineering-focused terms toward interdisciplinary and outcome-driven themes. Long-term burst keywords such as “biodiversity conservation” and “carbon storage” reflect the ongoing importance of regulating ecosystem services. More recent bursts—such as “water management,” “nature-based solutions,” “land surface temperature,” and “physical activity”—suggest a transition toward health, climate adaptation, and integrated urban governance.

This thematic evolution aligns with global sustainability agendas, including the Sustainable Development Goals (SDGs), particularly SDG 11 (Sustainable Cities and Communities) and SDG 13 (Climate Action). Moreover, the increased frequency of terms related to physical and mental health—especially during the pandemic—underscores a growing recognition of UBGI’s role in enhancing urban livability. The health and well-being of humanity are intrinsically linked to the health and well-being of the ecosystems [114].

Several recent studies illustrate this linkage: As a composite ecological system, blue-green spaces together form the patch–corridor–matrix complex ecological system pattern [115]. Forest exposure and tree canopy cover have been linked to reduced risks of asthma, dementia, and chronic stress [100,101,102]. Urban blue-green spaces have been shown to promote physical activity and improve mental well-being during periods of lockdown [116,117]. And it is crucial to reduce energy consumption, improve residents’ comfort and alleviate the urban heat island effect [118]. The potential energy savings analysis for buildings with UBI, UGI, and UBGI shows that UBI results in the highest average cooling energy savings (8.12%), followed by UBGI (6.73%) and UGI (4.78%) [119]. Additionally, greater water coverage leads to an increase in potential energy savings. Vegetation management of urban temperatures and the establishment of urban gardens for growing vegetables help maintain a balance between water and energy consumption [120]. UBGI enhances natural landscapes and biodiversity [121,122] by creating favorable habitats for plant and animal communities and supporting the ecological continuity of urban environments [123,124]. An illustrative example is the restoration of the Wandle River in Carshalton, which has facilitated the migration of various fish species, including wild trout, which had not been observed upstream for 80 years [125]. These findings reinforce the need to integrate a place-based approach to UBGI design, considering geographic, social, and cultural contexts. Research should aim to optimize co-benefits across environmental, social, and economic domains while incorporating community engagement and equity concerns. An increasing number of international policies are aimed at alleviating the pressure that urban densification and expansion place on green and blue spaces and their biodiversity [126].

4.4. Limitations

This study employed scientific methods to qualitatively and quantitatively analyze the development patterns of UBGI. Bibliometric methods are particularly valuable in identifying interdisciplinary collaboration patterns, tracking the evolution of research hotpots, and predicting future research directions [127]. While this study provides valuable insights, certain limitations should be acknowledged. First, bibliometrics (e.g., citation counts) tend to favor research areas or classic papers that were published earlier, are already very mature, and are widely cited and recognized. Newly published, niche, or disruptive research can be undervalued or ignored.

Second, this study’s findings primarily reflect patterns in the mainstream English-language academic literature, potentially underrepresenting significant contributions from non-English publications. Consequently, assertions regarding the dominance or influence of specific research domains—particularly emergent fields or those centered in non-Anglophone regions—require judicious interpretation.

Third, the citation burst and clustering methods depend heavily on the parameters selected in CiteSpace; results may vary with different thresholds and algorithms. Although this analysis captures the knowledge structure of the field, it does not fully address the qualitative dimensions of how UBGI is implemented in practice. This study relies exclusively on Web of Science literature, introducing selection bias that may exclude practice-oriented innovations like locally characteristic blue-green infrastructure designs from co-citation analysis. Geographical resolution is compromised, limiting city-scale spatial clustering accuracy, while cross-border collaborative research weights multi-institutional addresses equally regardless of actual contribution shares, potentially overstating regional mediating roles. Finally, the interrelationships among ecosystem services—and their trade-offs—require deeper exploration beyond bibliometric techniques.

5. Conclusions and Future Perspectives

UBGI presents a transformative pathway for enhancing urban resilience, sustainability, and livability. As cities confront escalating climate change and urbanization pressures, UBGI implementation becomes imperative for developing robust urban systems. For policymakers, keyword emergence and centrality analysis can help identify priority areas and support investment decisions; planners can optimize and multifunctionally design cities through clustering symbiotic relationships; and for communities, knowledge gap visualization supports fairness demands. Concerted action among these three stakeholder groups is imperative to fully realize the potential of UBGI and secure sustainable urban futures.

This study, through bibliometric mapping analysis, reveals that blue-green infrastructure (UBGI) ecosystem services research has evolved from a nascent concept to a core knowledge tool for addressing global urban sustainability challenges. Since 2014, scholarly attention to this topic has notably increased, particularly with a surge in research in 2020, marking UBGI’s transition from a peripheral issue to a key area in urban resilience building. This shift not only responds to the urgent demands posed by climate change and biodiversity crises but also reflects a profound transformation in urban planning concepts, moving from “gray infrastructure” to “blue-green integration.” International collaborative networks, exemplified by those in the UK, US, Germany, and China, act as “photosynthesis systems” for knowledge dissemination, driving the concurrent development of five major themes: utilizing nature-based solutions to address climate change, assessing the value of ecosystem services, redesigning urban spatial planning, protecting biodiversity, and addressing practical challenges in implementation. These research directions collectively form an interconnected urban system framework of “environment-health-infrastructure.”

Notably, there has been a significant shift in research focus, with social factors such as “physical activity,” “mental health,” and “water management” becoming central topics. This indicates that the recognition of UBGI’s value has transcended ecological aspects, extending into broader fields such as public health, social equity, and urban governance. This shift, from singular environmental assessments to interdisciplinary applications, represents an academic revolution—transforming blue-green infrastructure from mere landscape decoration into a vital urban life support system, turning nature-based solutions into quantifiable, actionable, and manageable resilience elements.

Future innovations will focus on strengthening the integration of the “social–ecological–technological” dimensions, utilizing intelligent algorithms to simulate benefits, designing equitable governance frameworks, and integrating cross-scale policies. This will transform UBGI from a theoretical concept into a practical tool for advancing urban health and sustainable development, ultimately achieving a win-win outcome for natural resources and social well-being. Studies indicate that future efforts should enhance international cooperation and establish a global data-sharing system and a standardized methodological framework. Establish the following goals: realize a comprehensive assessment of the multifunctionality of UBGI by integrating biophysical and socioeconomic indicators; construct a multi-scale monitoring network spanning communities, cities, and metropolitan areas; combine the Internet of Things and remote sensing technologies to track benefit gradients; and develop an artificial intelligence-driven digital twin system, thereby promoting UBGI research towards more efficient and resilient ecosystem design.