The Policy Positioning and Strategic Expectations of Landscape-Scale Green Infrastructure in Japan’s National-Level Policies

Abstract

In recent years, landscape-scale green infrastructure (LGI) has evolved from academic discussions into a critical approach to achieving sustainable development in national strategies in many countries. Since 2014, Japan has proactively integrated LGI into various policy documents; however, there is still a lack of systematic research on its policy positioning and strategic expectations. This study employs text mining, qualitative comparative analysis, and policy integration analysis to establish a comprehensive analytical framework for examining 66 screened and validated national-level policy strategy documents related to LGI in Japan. The results reveal four common core themes, four potential innovative directions, and seven topics defining the policy positioning of LGI. Additionally, the study highlights thematic preferences across different departments and temporal evolution trends. The findings indicate that Japan’s policy positioning on LGI is transitioning from a technical tool to an institutionalized management framework. However, this shift remains precarious due to the influence of competing strategic priorities. The “core–periphery” departmental coordination structure exacerbates risks of policy fragmentation to some extent. Overall, while an LGI policy system has begun to take shape in Japan, further efforts are needed in cross-level linkages and collaborative governance mechanisms.

1. Introduction

In recent years, green infrastructure (GI) has emerged as a critical strategy for supporting sustainable development, enhancing ecological resilience, and advancing multi-level land governance [1,2,3]. Its influence has evolved from academic research into national policy frameworks [4,5]. Across multiple countries and regions—including the United States, Europe, and Asia—GI has been integrated into core policy agendas, such as land use planning, ecosystem restoration, and climate adaptation [6]. This also underscores GI’s role as a key component of nature-based solutions (NbSs) within the policy domain [7,8,9].

Although GI is frequently referenced in policy documents, these texts often fail to explicitly define its spatial scale. However, GI at different scales entails significantly distinct governance mechanisms and functional priorities [10] and manifests diverse operational characteristics in practice. Some approaches emphasize micro-scale green facility construction, such as rain gardens and urban greenways [11,12], while others focus on macro-scale ecological connectivity, regional spatial coordination, and cross-system integration [13,14]. This semantic ambiguity makes it difficult to interpret the policy intent and positioning of GI upon initial examination of policy texts. Particularly in national-level strategic policies, GI typically transcends specific facilities or localized projects, instead emphasizing a systemic and integrated spatial intervention approach at the landscape scale. To more accurately identify and analyze the policy positioning and strategic expectations associated with this type of GI, this study adopts the term landscape-scale green infrastructure (LGI), drawing on definitions proposed in previous research that emphasize spatial extensiveness, systemic governance functions, and multifunctionality [15,16,17,18].

The term landscape-scale has gained widespread use in ecological planning and landscape ecology. Its key characteristic—operating beyond administrative boundaries—makes it a suitable descriptor for spatial governance units encompassing diverse land uses, requiring the integration of ecological processes and spatial patterns [19,20,21]. Within GI research, “landscape-scale” is also widely employed in international contexts [15,17,22,23]. Therefore, we employ “landscape-scale” as a qualifying term to distinguish the GI addressed in this study from other forms. This aims to clarify the macro-level nature of GI encompassed within policy texts and prevent theoretical ambiguity and empirical bias arising from conflating strategies across different spatial scales.

It is worth noting that LGI has the dual attributes of guiding and being guided. On one hand, as a regional-scale green space strategy, it can guide local practices through spatial planning, facilitating the construction of ecological networks and optimizing land use structures [6]. On the other hand, the strategic direction, implementation pathways, and institutional integration of LGI are highly reliant on guidance from overarching policies (e.g., the EU Green Infrastructure Strategy) [24]. However, less attention is given to LGI itself as an object being guided—how it is positioned within higher-level policy frameworks and the ways in which it is shaped by their influence. The absence of such research may result in an incomplete institutional construction of LGI and obscure the fundamental mechanisms underpinning its policy stability and interdepartmental coherence [25,26,27].

As an early adopter of the GI concept, Japan officially introduced the term “グリーンインフラ(GI)” into its national strategic policies in 2014. Currently, discussions on LGI in Japan are predominantly concentrated on application-oriented themes such as watershed governance and flood management [28,29,30], ecological networks and regional green space planning [31,32], disaster prevention and mitigation [33,34], and urban green strategies [35,36,37]. While the number and scope of related policies have been increasing, there remains a lack of systematic analysis of how these policies define LGI, the institutional pathways through which they are embedded, the governance logic employed, and whether cross-departmental coordination mechanisms for LGI have emerged. Addressing these questions is crucial to understanding Japan’s concept of LGI.

To fill this research gap and clarify Japan’s LGI concept, this study systematically collected and analyzed 66 national-level policies related to LGI in Japan for the first time. Utilizing a methodological framework comprising text mining, qualitative comparison, and policy integration analysis, a comprehensive analysis of these policies was conducted. The analysis focused on three key questions:

• How do these policies define and position LGI? What are the main policy issues and strategic directions?
• How has LGI manifested in terms of temporal trends across these policies?
• What are the thematic preferences of different policy-issuing departments regarding LGI? Are there cross-departmental coordination structures in place?

Through this analysis, this research aims to reveal the overall strategic positioning and institutional embedding logic of LGI within Japan’s national policy system. This will provide theoretical support and empirical basis for understanding the scalability, collaborative governance pathways, and multi-level integration mechanisms of LGI in Japan.

2. Methodology

Based on text mining, qualitative comparative analysis, and policy integration analysis, we constructed a methodological framework (see Figure 1) to systematically analyze the collected Japanese policies related to LGI. The specific process is as follows.

2.1. Policy Collection and Compilation

To ensure comprehensiveness, enhance retrieval efficiency, and maintain data quality, this study employed a combined approach of Python web scraping and manual verification for policy collection [38,39,40]. We initially conducted searches on the official websites of the Japanese national ministries for content related to “グリーンインフラ (GI)”. Recognizing that Japan lacks a clear distinction between LGI and other forms and that descriptions of GI vary across different policies, we developed the following inclusion criteria based on fundamental distinguishing features between LGI and others:

• Policy Effectiveness: Given the broad scope of LGI, which often requires inter-departmental and cross-regional cooperation, policy documents with legal force or formal strategic significance can provide more effective support for the normal development of LGI [41]. Therefore, we selected policy documents issued by national official institutions, including statutory plans, official strategies, and action plans, as the research objects to ensure the authority and effectiveness of the analysis conclusions.
• Policy Coverage Scale: Based on existing LGI practices and research experience, we found that scale is a crucial influencing factor differentiating LGI from other types of GI [42,43]. The judgment standard for “landscape-scale” is not the physical size of the site but the complexity and systematization degree of landscape elements within the site [44,45]. After discussion among all authors and considering Japan’s actual landscape distribution characteristics, we believe that the minimum applicable scale for LGI in Japan is at the prefectural level. Moreover, from a governance perspective, municipal governments, while responsible for implementation, tend to operate with greater autonomy and focus on the management of localized concerns within their own jurisdictions. This top-down planning structure makes the prefectural level more appropriate for examining LGI, which emphasizes inter-regional coordination and systemic spatial integration. Therefore, the policies included in this study’s analysis should have an administrative scope of at least the prefecture level or above.
• Policy Version Time Evolution: Since LGI was officially incorporated into Japanese policy documents, many policies have been updated multiple times. To better grasp the policy orientation, all research objects mentioning LGI will be included in this study’s analysis, regardless of whether subsequent updated versions still involve LGI.

2.2. Text Mining

This study employed text mining to analyze the expressions of LGI within Japanese national-level policy texts, focusing on both content and expression, aiming to systematically identify policy implications, compare expression differences, and explore structural differences between policy documents. This involved four specific steps:

• Preprocessing and Section Extraction: After retrieval and screening, we collected all policy strategy documents related to LGI issued by various ministries since GI first appeared in Japanese national-level policies. Using Python 3.12.9, the policy texts were cleaned, and based on punctuation marks and chapter titles, the text was divided into sections. We extracted parts containing “グリーンインフラ (GI)”, along with their context, and numbered and recorded basic information about their position in the file.
• Keyword and Topic Identification: Considering that the textual language is Japanese, this study utilized the MeCab tokenizer to parse the corpus, enhancing the accuracy of the conclusions [46]. However, MeCab has certain limitations in processing compound nouns and proper nouns. To mitigate these issues, we conducted manual verification and adjustment of key extracted terms. We first identified high-frequency keywords and distinctive core terms using Term Frequency (TF) and Term Frequency–Inverse Document Frequency (TF–IDF) methods [47,48] and visualized them through word clouds in both Japanese and English. Subsequently, we conducted a co-occurrence analysis to construct a co-occurrence matrix and network, further exploring policy concepts co-occurring with LGI and their structural relationships [49]. Finally, we introduced Latent Dirichlet Allocation (LDA) topic modeling [50,51] to extract potential topics from paragraphs, analyzing the internal thematic structure at the content level and identifying the core topics emphasized by each policy.
• Expression Pattern Clustering Analysis: Since the policy strategies involved in this study come from multiple departments, we used the K-Means Clustering method [38] to identify similarities and differences in expression patterns within policy texts and validate the results of LDA topic identification. This unsupervised clustering analysis categorized paragraphs based on their overall expression style, identifying potential types. By summarizing different policy narrative modes, this provides auxiliary support for the categorization of policy intent and thematic structure.

2.3. Qualitative Comparative Analysis

Building upon the text mining results, qualitative comparative analysis [52,53] was conducted to enhance the interpretability of semantic analysis. By tracing back and comparing typical paragraphs within their original context, we summarized the expression logic and core demands of policy language.

Specifically, we selected representative paragraphs from each topic, considering background information such as the issuing ministry and publication date of the respective document. We conducted a in-depth semantic analysis, summarizing their expression structure and policy intent. Simultaneously, we explored the thematic preferences of different publishers and the patterns of policy topics evolving over time, revealing similarities and differences in policy stances across departments. This helped address the limitations of quantitative analysis in understanding context and interpreting policy intent, providing semantic support for subsequent policy context classification and interpretation.

2.4. Policy Integration Analysis

To further explore the integration of LGI topics within Japanese national-level policies, this study employed policy integration analysis [54] based on the previous qualitative comparative analysis, systematically assessing the consistency of policy expressions across different ministries and identifying potential institutional fragmentation risks [55,56].

Specifically, this involved calculating vector similarity between topic preferences of different departments using cosine similarity to analyze their expression consistency and identifying departments with a high concentration in a single topic, departments with significant differences in topic distribution, and topics lacking departmental involvement. This helped analyze institutional fragmentation risks.

In summary, this study developed a multi-layered text mining framework that includes text preprocessing, keyword analysis, co-occurrence analysis, topic modeling, expression style comparison, and clustering analysis to systematically analyze the expression patterns and content structure of LGI within Japanese national-level policy texts. Based on this foundation, we further introduced qualitative comparative analysis and policy integration analysis to gain deeper insights into the similarities and differences in multi-departmental policy expressions, collaborative logic, and institutional integration status. By complementing quantitative and qualitative methods, this research provides a solid analytical foundation for comprehensively understanding the positioning and expectations of national-level policies toward LGI, offering a practical empirical approach for research on multi-departmental policy governance and providing methodological references for future studies.

3. Results

3.1. Distribution and Overview of Policy and Strategy Characteristics

Through a dual-pronged approach using Python 3.12.9 and manual review, we collected 66 policy strategy documents meeting the screening criteria, originating from various ministries: the Ministry of Land, Infrastructure, Transport and Tourism (MLIT); the Ministry of the Environment (MOE); the Ministry of Agriculture, Forestry and Fisheries (MAFF); the Cabinet Office (CAO); and the Cabinet Secretariat (CS) (see

Table 1. List of national-level policies and strategies in Japan involving LGI * (summarized from official websites by author).

Issuing Ministry	Date of Publication	Policy Title (English Translation)
Ministry of Land, Infrastructure, Transport and Tourism (MLIT)	2014/3	Environmental Action Plan—Overcoming the Environmental Crisis and Achieving a Sustainable Society
	2014/7	Grand Design of National Land 2050
	2015/8	The 2nd National Spatial Planning (National Plan)
	2015/8	The 5th National Land Use Plan (National Plan)
	2015/9	The 4th Social Capital Improvement Priority Plan
	2015/11	Climate Change Adaptation Plan of the Ministry of Land, Infrastructure, Transport and Tourism
	2017/3	The 4th Basic Technology Plan of the Ministry of Land, Infrastructure, Transport and Tourism
	2018/11	Climate Change Adaptation Plan of the Ministry of Land, Infrastructure, Transport and Tourism
	2019/7	Green Infrastructure Promotion Strategy
	2021/5	The Fifth Social Capital Improvement Priority Plan
	2021/7	MLIT Green Challenge Toward the Realization of a Green Society
	2021/12	Environmental Action Plan of the Ministry of Land, Infrastructure, Transport and Tourism
	2022/4	The 5th Basic Technology Plan of the Ministry of Land, Infrastructure, Transport and Tourism
	2023/7	The 3rd National Spatial Planning Plan (National Plan)
	2023/7	The 6th National Land Use Plan (National Plan)
	2023/9	Green Infrastructure Promotion Strategy 2023
	2024/6	Disaster Prevention Work Plan of the Ministry of Land, Infrastructure, Transport and Tourism
Ministry of the Environment (MOE)	2015/11	Climate Change Adaptation Plan
	2018/4	Environmental Basic Plan 2018
	2018/11	Climate Change Adaptation Plan 2018
	2023/3	National Biodiversity Strategy 2023–2030 ~Nature-Positive Roadmap~
	2024/3	Nature Positive Economy Transition Strategy: Creating Corporate Value Based on Natural Capital
	2024/4	Disaster Prevention Operations Plan of the Ministry of the Environment
	2024/8	Strategy for Promoting Environmental Research and Technology Development
	2024/8	Basic Plan for Promoting the Formation of a Recycling-Oriented Society: Positioning Circular Economy as a National Strategy
	2025/2	Plan for Global Warming Countermeasures
Ministry of Agriculture, Forestry and Fisheries (MAFF)	2016/5	Basic Plan for Forest and Forestry
	2020/5	Agriculture, Forestry and Fisheries Research Innovation Strategy 2020
	2023/3	Biodiversity Strategy of Ministry of Agriculture, Forestry and Fisheries
	2023/12	Basic Plan for the Management and Administration of National Forests and Woodlands
Cabinet Office (CAO)	2021/3	6th Science, Technology and Innovation Basic Plan
	2021/6	Basic Policy on Economic and Fiscal Management and Reform 2021
	2021/6	Integrated Innovation Strategy 2021
	2022/6	Basic Policy on Economic and Fiscal Management and Reform 2022
	2022/6	Integrated Innovation Strategy 2022
	2023/6	Basic Policy on Economic and Fiscal Management and Reform 2023
	2023/6	Integrated Innovation Strategy 2023
	2023/6	Grand Design and Action Plan for a New Form of Capitalism, 2023 Revised Version
	2023/6	PPP/PFI Promotion Action Plan (2023 Revised Version)
	2024/6	Basic Policy on Economic and Fiscal Management and Reform 2024
	2024/6	Integrated Innovation Strategy 2024
	2024/6	Grand Design and Action Plan for a New Form of Capitalism, 2024 Revised Version
	2024/6	PPP/PFI Promotion Action Plan (2024 Revised Version)
Cabinet Secretariat (CS)	2016/5	National Resilience Action Plan 2016
	2017/6	National Resilience Action Plan 2017
	2018/6	National Resilience Action Plan 2018
	2018/12	National Resilience Basic Plan—Toward a Strong and Flexible Japan-
	2019/6	National Resilience Annual Plan 2019
	2019/6	Basic Policy on Town, People, and Job Regeneration 2019
	2019/12	Second Phase of the Comprehensive Strategy for Town, People, and Job Regeneration
	2020/6	National Resilience Annual Plan 2020
	2020/6	Basic Plan on Water Cycle 2020
	2020/7	Basic Policy on Town, People, and Job Regeneration 2020
	2020/12	Second Phase of the Comprehensive Strategy for Town, People, and Job Regeneration (2020 Revised Edition)
	2021/6	Growth Strategy Follow-up
	2021/6	National Resilience Annual Plan 2021
	2021/6	Basic Policy on Town, People, and Job Regeneration 2021
	2022/6	National Resilience Annual Plan 2022
	2022/6	Basic Plan on Water Cycle 2022
	2022/12	Comprehensive Strategy for the Digital Garden City Nation Initiative
	2023/7	National Resilience Basic Plan 2023
	2023/7	National Resilience Annual Plan 2023
	2023/12	Comprehensive Strategy for the Digital Garden City Nation Initiative (2023 Revised Edition)
	2024/7	National Resilience Annual Plan 2024
	2024/8	Basic Plan on Water Cycle 2024
Government of Japan (All Ministries)	2021/6	Green Growth Strategy Toward 2050 Carbon Neutrality

* The original Japanese title of policies and issuing ministry are in Appendix A.

). Notably, “Green Growth Strategy Towards 2050 Carbon Neutrality” was a policy document jointly formulated by all national-level government departments. While most other policies maintained their focus on LGI throughout evolution, two distinct patterns emerged:

• Policies omitting LGI in subsequent versions: MAFF’s “Basic Plan for Forest and Forestry” mentioned LGI in 2016 but excluded it from the 2021 update. Similarly, MAFF’s “Agriculture, Forestry and Fisheries Research Innovation Strategy 2020” included LGI only in the 2020 strategy; it was absent in the 2021–2024 version.
• Policies lacking updates or experiencing name changes: CAO’s “6th Science, Technology and Innovation Basic Plan” was renamed “Integrated Innovation Strategy” starting in 2021. CS’s “National Resilience Action Plan (2016–2018)” transitioned to “National Resilience Annual Plan” after 2019. “Growth Strategy Follow-up” remained the only policy strategy without subsequent updates.

Regarding policy quantity, the number of Japanese national-level LGI-related policies has shown an upward trend year by year, particularly since 2020, peaking in 2023 with a total of 13 policies (see Figure 2). This reflects the increasing emphasis placed on LGI by policymakers.

3.2. Text Mining Results

After cleaning and segmenting the 66 policy strategy documents, we extracted 614 segments containing descriptions related to LGI along with their context. Based on these data, we obtained the following results.

3.2.1. Keyword Extraction and Co-Occurrence Analysis

To understand the overall focus of policy and strategy on LGI, we constructed a stop word list to filter low-information words by combining common auxiliary verbs, function words, organization names, and policy jargon. Using TF and TF–IDF methods, we extracted the top 50 keywords respectively (see Appendix B) and visualized them in English and Japanese word clouds for comparison (see Figure 3). After refining the stop word list, we performed co-occurrence analysis on word pairs and generated a co-occurrence network to clarify the structural connections related to LGI (see Figure 4).

3.2.2. LDA Topic Modeling

To further identify distinct thematic expressions of LGI within policy texts, this study employed LDA for topic modeling. To determine the optimal number of topics, this study evaluated the models from three perspectives: coherence score, perplexity (see Figure 5), and the inter-topic distance map (see Figure 6). While the 9-topic and 11-topic models showed slightly higher coherence scores, the 7-topic model also achieved a satisfactory score. In terms of perplexity, increasing the number of topics did not lead to a clear improvement, suggesting that model fit did not significantly benefit from additional topics. Moreover, the topic distribution in the 7-topic model displayed a well-structured layout with distinct, non-overlapping clusters, which facilitates interpretation. In contrast, models with eight or more topics showed blurred or overlapping boundaries, reducing overall interpretability. Therefore, we ultimately set the number of topics to seven and created English–Japanese bilingual word clouds for each topic (see Figure 7), where words with higher weights in the cloud are displayed in larger font sizes.

3.2.3. Expression Style Analysis

To visualize the clustering results, which involve high-dimensional sparse vectors representing text, this study utilized the UMAP dimensionality reduction method [57] combined with K-Means clustering to analyze the expression styles of the 614 segments. Comparing results from clustering schemes ranging from 3 to 10 classes, we found that the five-cluster solution yielded superior overall density structure, separability, and expression stability (see Figure 8). These policy expressions can be broadly categorized into five distinct styles. We further calculated the Adjusted Rand Index (ARI) coefficient to validate the consistency between expression styles and topic classifications (see Figure 7), but the results indicated that while the ARI showed an upward trend with increasing cluster numbers, the alignment remained limited, with all values falling below 0.03, indicating minimal correspondence between clusters and topics. This result suggests that expression styles and thematic content in policy texts may vary independently. In practice, even documents addressing similar topics may differ significantly in tone and rhetorical structure, depending on the issuing agency, institutional style, or intended audience.

3.3. Qualitative Interpretation of Findings

Combining qualitative analysis with the quantitative results from text mining, we draw the following conclusions.

3.3.1. Overview of Policy Content Based on TF and TF–IDF Results

This study first applied the Louvain method for community detection to the co-occurrence results, identifying three prominent semantic clusters (see Figure 9). However, the resulting classification remains coarse in semantic terms, with multiple heterogeneous topics grouped together. Some clusters contain diverse elements such as institutional design, implementation tools, and spatial governance, which are difficult to interpret as a single theme. To enhance analytical clarity, we further conducted a qualitative interpretation based on the clustering output, visual distribution, and policy context, and refined the categorization into six functionally oriented semantic groups (see

Table 2. Interpretation of semantic clusters identified from co-occurrence network (by author).

Visual Distribution	Thematic Cluster	Representative Keywords (Visual Cluster)	Interpreted Semantic Function/ Policy Implication
Semantic Core Clusters	Core Governance and Societal Structure	Green Infrastructure, Diversity, Public–Private, Platform, Actor, Local, Public, Implementation, Field	Highlights LGI as a central coordination mechanism and governance platform that enables cross-sectoral participation and multi-actor collaboration
	Disaster Response and Risk Control	Disaster Prevention, Disaster Mitigation, Earthquake, Risk, Evacuation, Earthquake Resistance, Damage, Prevention	Emphasizes LGI’s role as a key tool in disaster risk reduction and urban resilience, with frequent co-occurrence of terms related to earthquake prevention and emergency response.
	Ecological Protection and Environmental Restoration	Nature, Conservation, Ecology, Forest, Coastline, Watercourse, Sustainability, Regeneration	Reflects strong associations between LGI and natural systems, ecological recovery, and long-term sustainability, forming a pathway for interpreting GI as ecological infrastructure.
	Spatial Utilization and Development Optimization	Urban, Territory, Management, Development, Improvement, Design, Enhancement, Appropriate	Suggests a technocratic framing of LGI in relation to urban and territorial development, emphasizing its functional value in improving spatial layouts and planning efficiency.
Peripheral Scattered Clusters	Methodological and Policy Extension	Method, Model, Funding, Realization, Formulation, Strategy, Capital, Efficiency, Expansion	Indicates an emerging narrative of institutionalization, financialization, and systematization of LGI, possibly reflecting the policy push toward technical integration and implementation frameworks.
	Cultural and Social-Semantic Margins	Culture, Attractiveness, Thinking, Community, Residents, Self-Governance	Focuses on a small group of culturally embedded and place-based terms, suggesting the potential for community-level engagement and the socio-cultural integration of LGI practices.

). Building upon this, we combined TF and TF–IDF analysis to summarize and interpret the policy implications of each cluster. Considering that TF primarily focuses on the frequency of terms within the entire corpus, while TF–IDF emphasizes distinctive content and characteristic wording within documents, this study extracted both the common framework and potential innovation directions of policy texts based on these two methods. Specifically, common core themes related to LGI in Japanese national-level policies and strategies can be summarized as follows.

• Disaster Prevention and Emergency Management: LGI is viewed as a crucial tool for addressing various disaster risks and an essential component of building a disaster prevention system.
• Ecological Protection and Natural Resource Management: The introduction of LGI not only aims to protect ecosystems but also emphasizes comprehensive management of natural resources such as forests, rivers, and watersheds. Through NbS, LGI promotes the restoration of ecosystem services while enhancing resource sustainability and environmental resilience.
• Spatial Planning and Regional Governance: LGI is incorporated into the national land use planning system as a key tool for regulating land use and optimizing urban development. It plays a positive role in guiding green development, coordinating urban and rural construction, and promoting regional coordinated development.
• Public–Private Cooperation and Public Management: Policy documents generally emphasize public–private partnership as the core path for advancing LGI implementation, which is also a governance trend for addressing complex social and environmental issues.

Furthermore, representative distinctive expressions and potential innovative directions include:

• Environmental Transformation and Urban Resilience Orientation: Some policy strategies position LGI as a core driver of environmental transformation and enhancing urban resilience.
• Cross-sectoral Collaboration and Multi-stakeholder Governance: When addressing complex policy issues, some policies emphasize building horizontal coordination mechanisms to promote collaboration across departments, disciplines, and levels, integrating the expertise of government, enterprises, research institutions, and community organizations.
• Institutional and Mechanistic Extension Applications: Some policies explore incorporating LGI concepts into the design of laws, regulations, financial tools, and governance models, demonstrating its high adaptability and institutionalization potential from concept to operation.
• Cultural Embedding and Regional Characteristic Integration: Some policy texts begin exploring the possibility of integrating local culture and regional characteristics into LGI design and implementation, highlighting its social and cultural inclusiveness and adaptability.

3.3.2. Interpretation of Policy Topics Based on LDA

The LDA topic modeling results showed seven main semantic clusters, encompassing a multi-faceted thematic structure ranging from institutional integration to cultural fusion. Based on the representative keywords and qualitative descriptions for each topic (see

Table 3. LDA-derived topics and descriptions (by author).

Topic Number	Representative Keywords (Ordered by Weight)	Topic Description
Topic 1	Green Infrastructure, Implementation, Green, Development, Private Sector, Promotion, Introduction	Centered on “green infrastructure”, “implementation”, and “promotion”, this topic emphasizes institutional mechanisms that facilitate the introduction and application of LGI, particularly through public–private cooperation.
Topic 2	Land Use, Space, Management, Shaping, Design, Urban Development, Urban	These keywords highlight the spatial integration of LGI in urban and territorial planning, especially in areas related to design, land development, and spatial governance. The documents focus on spatial planning tools and ecologically oriented development strategies.
Topic 3	Flood Control, Watershed, Dam, Rainwater, Infiltration, Discharge, Water Cycle	This cluster emphasizes the hydrological and ecological regulation functions of LGI, with keywords focusing on water resource utilization and flood risk management. The texts reflect LGI’s application in basin-scale planning and urban water circulation through nature-based approaches.
Topic 4	Disaster Prevention, Disaster Mitigation, Earthquake Resistance, Evacuation, Tsunami, Resilience, Disaster	The high-weighted terms reflect LGI’s role in disaster response, especially in earthquake, flood, and evacuation contexts. LGI is framed as a “green disaster prevention infrastructure”, contributing to resilient urban development.
Topic 5	Nature, Ecosystem, Conservation, Forest, Regeneration, Coexistence, Diversity	This topic is focused on ecosystem protection and biodiversity. The high-weighted keywords convey a vision of an “ecological symbiosis society”, where LGI functions as a mechanism to support biodiversity restoration and ecosystem services.
Topic 6	Public–Private, Collaboration, Community, Diversity, Citizens, Actor, Self-Governance	The cluster highlights structural features of multi-actor governance, with emphasis on local autonomy, public–private platforms, and community collaboration mechanisms that facilitate broad-based LGI implementation.
Topic 7	Culture, Attractiveness, Local, Life, Tradition, Landscape, Tourism	These keywords reflect humanistic and cultural elements, indicating that LGI not only carries ecological and technical value but also serves to enhance local attractiveness and integrate historical, cultural, and scenic characteristics—representing a policy trend toward cultural embedding and soft governance.

), we summarize the LGI-related topics in Japanese national-level policy texts as follows.

• Topic 1: Institutional Promotion and Policy Implementation
• Topic 2: Land Use and Spatial Integration
• Topic 3: Water Resources and Ecological Regulation
• Topic 4: Disaster Prevention, Mitigation, and Resilience Building
• Topic 5: Ecosystem Protection and Nature Coexistence
• Topic 6: Multi-Stakeholder Participation and Collaborative Governance
• Topic 7: Regional Culture and Social Value Integration

These themes demonstrate LGI’s functional positioning and strategic embedding in various dimensions, including space, ecology, society, and culture, reflecting the policy discourse’s parallel narrative logic of “green transformation” and “collaborative governance”.

Based on the co-occurrence rate between sections related to LGI in each policy and different topics, we calculated the average co-occurrence rate of each policy with the seven topics and presented it as a heatmap (see Figure 10) to demonstrate the thematic affiliation of each document.

3.3.3. Interpretation of Topic Preferences and Evolution

Based on the seven identified topics, we qualitatively interpreted the policy topic preferences of different ministries and the trends in topic evolution over time, considering policy publication information such as the issuing ministry and publication date. Notably, six out of the 66 policies (one from MLIT, one from MOE, two from MAFF, and two from the Cabinet Office) exhibited a comprehensive probability score of zero across the seven topics in the LDA model. This indicates that these policies contained insufficient relevant information regarding LGI and were effectively removed during the LDA modeling process. Considering that these policies tend to be earlier and have been subsequently revised, we believe this phenomenon does not significantly impact the effectiveness of the LDA topic modeling results.

Due to the possibility of a single policy encompassing multiple topics, this study employed an unweighted arithmetic mean method to calculate each ministry’s preference for policy topics. This method assumes that each policy document contributes equally to the overall thematic inclination of its issuing ministry, providing a general overview of its average topic focus (see Figure 11).

The results indicate that different ministries demonstrate distinct topic preferences. Notably, the CS exhibits a relatively high level of engagement across all topics, showcasing a broad interest in multiple policy areas. The CAO displays the strongest emphasis on Institutional Promotion and Policy Implementation (average value: 0.659) while demonstrating comparatively lower involvement in other topics. MLIT demonstrates a more balanced distribution across various topics, particularly showing a notable preference for Institutional Promotion and Policy Implementation (average value: 0.359), Water Resources and Ecological Regulation (average value: 0.504), and Multi-Stakeholder Participation and Collaborative Governance (average value: 0.333). MOE similarly exhibits a high focus on Water Resources and Ecological Regulation (average value: 0.599). In contrast, MAFF’s thematic focus is more concentrated, primarily centered around Water Resources and Ecological Regulation (average value: 0.495) and Disaster Prevention, Mitigation, and Resilience Building (average value: 0.267). These findings reflect the diversity in policy agenda choices among different ministries, with potential contributing factors to these variations likely related to their respective responsibilities and policy objectives.

Analyzing the trend in Institutional Promotion and Policy Implementation preferences over time, we again employed an unweighted arithmetic mean method to calculate the results (see Figure 12). Notably, Institutional Promotion and Policy Implementation received almost zero attention in the early period (2014–2016) but gradually increased from 2018, peaking in 2019 and 2021 with values of 0.853 and 0.744, respectively. Land Use and Spatial Integration maintained a relatively low overall focus, experiencing only slight increases in 2014, 2019, and 2020. Water Resources and Ecological Regulation consistently remained the most prominent topic, maintaining a high weight from 2014 to 2025 and reaching its peak at 0.867 in 2025. Disaster Prevention, Mitigation, and Resilience Building saw a significant surge in 2016 and 2017 (0.736 and 0.708, respectively), subsequently declining but remaining at a moderate level. Ecosystem Protection and Nature Coexistence peaked in 2016 (0.795) before fluctuating downward. Multi-Stakeholder Participation and Collaborative Governance demonstrated stronger performances in 2015 and 2018, with a resurgence in 2020. Regional Culture and Social Value Integration reached its peak in 2016 (0.972), followed by an overall downward trend but maintaining a relatively high level between 2018 and 2020.

3.4. Analysis of Policy Integration

Based on the topic preferences of different ministries, we analyzed the consistency of preference structures between departments using cosine similarity (see Figure 13). The analysis reveals that MLIT and CS exhibit a very high degree of similarity (similarity = 0.948), as well as MLIT and MOE (similarity = 0.934), indicating a close alignment in their policy topic structures. Furthermore, the similarity between CS and MOE is also high (0.865), further supporting the notion that these three ministries form a relatively cohesive “policy coordination core group”. Such high consistency provides a solid foundation for cross-departmental policy integration and facilitates the implementation of unified strategies and collaborative governance mechanisms. In contrast, the similarity in topic preferences between CAO and MAFF is the lowest, at just 0.226, suggesting significant differences in their policy focus. Additionally, the similarity between MAFF and other ministries (e.g., MLIT, CS) is notably lower than the overall average, indicating that its policy orientation is relatively independent within the horizontal policy structure.

4. Discussion

4.1. Evolution of Japan’s LGI Policy Positioning and Institutionalization Challenges in the Global Context

Looking at the overall development trend, three key periods have significantly shaped Japan’s LGI policy positioning: 2014, when Japan first incorporated LGI into national policy; 2021, a pivotal year marked by a notable increase in the number of policies; and 2023, when the number of policies reached its peak. These key time points coincide with major international developments that have influenced Japan’s LGI policy trajectory. We construct a macro-contextual backdrop of LGI policy development and its interaction with global agendas around these critical nodes (see

Table 4. Macroscopic background of LGI development in Japan’s national policies in relation to global dynamics (by author).

Key Milestone	Year	Organization	Policy or Action
Starting Point	2014	Intergovernmental Panel on Climate Change (IPCC)	IPCC Fifth Assessment Report (AR5)
	2014	European Commission	European Union (EU) Green Infrastructure Strategy (implementation phase)
	2014	United Nations International Strategy for Disaster Reduction (precursor to United Nations Office for Disaster Risk Reduction)	Preparation for the Sendai Framework for Disaster Risk Reduction
Turning Point	2020	Multiple (United Nations Environment Programme, EU, national governments)	Global Green Recovery Policies post-COVID
	2022	Convention on Biological Diversity (CBD)	Kunming–Montreal Global Biodiversity Framework (“30 × 30” Target)
Critical Point	2023	United Nations Framework Convention on Climate Change (UNFCCC) 28th Conference of the Parties to the UNFCCC (COP28)	COP28 highlights: Nature-based Solutions and Adaptation
	2023	United Nations	UN Water Conference—emphasis on urban water resilience and GI
	2023	Taskforce on Nature-related Financial Disclosures (TNFD)/global financial sector	Expansion of Environmental, Social, and Governance (ESG), Nature Capital Accounting, and TNFD disclosure frameworks

).

Between 2013 and 2014, the Intergovernmental Panel on Climate Change (IPCC) released its Fifth Assessment Report (AR5), which clearly underscored the ongoing trend of global warming and its significant impacts on ecosystems, water resources, and urban resilience [58]. During the same period, the European Union formally launched the EU Green Infrastructure Strategy, marking the first global policy initiative to systematically integrate the concept of LGI into its institutional framework [24]. The strategy’s focus on “fully leveraging nature’s multifunctionality to address environmental challenges” aligned with the emerging global consensus on policies such as “Ecosystem-based Adaptation (EbA)” and “NbS” [59,60,61,62]. These international events have been discussed and examined in relevant policy-making meetings and research studies [63,64]. In this context, Japan, as a developed nation, began to gradually incorporate LGI into its policy discourse, signaling the official beginning of LGI’s integration into Japan’s national policy framework.

Since 2020, global policy attention toward GI has seen a significant surge, particularly in the aftermath of the COVID-19 pandemic, during which “Green Recovery” emerged as a critical pathway for nations to address multiple crises [65]. Many countries have incorporated GI into their green new deal and recovery policies, accelerating the mainstream adoption of urban green spaces, ecosystem services, and NbS [66,67,68,69]. As a key form of NbS implementation, LGI has consequently benefited from both policy promotion and increased financial support. Furthermore, the adoption of the Kunming–Montreal Global Biodiversity Framework in 2022, with the introduction of the “30 × 30” target, has reinforced global consensus on the importance of ecological connectivity and green infrastructure development, aligning seamlessly with the core principles of GI [70,71]. This influence has led to the frequent incorporation of LGI into national policies in Japan, marking the beginning of a prosperous phase in its policy development.

The year 2023 marks another critical juncture in LGI policy development. Both the United Nations Water Conference and the Climate Change Conference of Parties (COP28) held in this year highlighted nature-based adaptation strategies, with LGI consistently emphasized as a vital tool for addressing complex risks such as extreme climate events and water resource crises [72,73,74,75]. In addition, the rapid advancement of new global governance and financial mechanisms in 2023, driven by natural capital accounting and ESG investment frameworks [76,77], is expanding the scope of LGI beyond its traditional environmental domain, moving into the realms of governance and capital markets. In the policy discussion meetings in Japan, these international events were thoroughly discussed [78].

At the same time, structural challenges have emerged during this policy evolution, particularly in terms of longitudinal policy continuity and institutionalization. For example, the renaming of the CAO’s “6th Science, Technology and Innovation Basic Plan” to “Integrated Innovation Strategy” and the transition of CS’s “National Resilience Action Plan” to “National Resilience Annual Plan” presents a challenge for text tracing and quantitative analysis. While these changes maintain the core policy objectives, they introduce significant obstacles, particularly in research methods relying on keywords and document titles, potentially leading to “breaks” and misinterpretations in the policy chain. This underscores that policy evolution is not a linear process but rather a dynamic one characterized by restructuring, transformation, and repositioning.

Moreover, the omission of LGI in subsequent policy versions highlights its lack of firm integration into the structural logic of the policy system, exhibiting a phenomenon of issue decoupling. Therefore, to ensure LGI’s sustained presence and stable embedding within Japan’s policy framework, it is crucial not only to leverage the traction provided by global agendas but also to strengthen its institutional foundation and policy vitality through domestic mechanisms such as legislative support, standard setting, and inter-departmental collaboration.

In conclusion, the development of Japan’s national-level LGI has been significantly propelled by global environmental governance agendas while simultaneously facing dual challenges of internal institutionalization and policy continuity. From its nascent stage marked by concept introduction, through an expansion phase fueled by green recovery initiatives, to a crucial period characterized by deepening governance mechanisms, LGI has gradually transitioned from a marginal discourse to a vital component of the national policy framework. However, its instability in longitudinal policy transmission and relatively shallow embedding within the institutional framework remain concerns. To further solidify LGI’s position within Japan’s policy system, it is crucial to build upon global agenda alignment by strengthening domestic policy mechanisms’ continuity, institutionalization, and traceability. This will enable green infrastructure to play a lasting role in addressing multiple crises and promoting sustainable development.

4.2. A Multidimensional Expansion of Japan’s LGI Policy Positioning

Japanese LGI policy demonstrates a trend toward multidimensional expansion, extending beyond its core thematic commonalities to encompass broader governance frameworks and explore innovative directions.

First, in disaster risk reduction, LGI is explicitly incorporated into core frameworks of “disaster risk management” and “resilience enhancement”. For instance, the Environmental Basic Plan 2018 repeatedly emphasizes the utilization of “green infrastructure to enhance resilience”, specifically noting its contribution to comprehensive response capabilities against various natural disasters such as floods and earthquakes. In natural resource management, LGI extends beyond ecosystem protection, becoming integrated into comprehensive governance mechanisms for regions like forests and river basins, demonstrating a holistic understanding of “ecosystem services”. As exemplified in the Disaster Prevention Operations Plan of the Ministry of the Environment, policy documents emphasize the promotion of “green infrastructure and Eco-DRR”, clearly linking it to collaborative advancement with basin-wide integrated management and unified water resource management.

Second, the policy functions of LGI are increasingly extending to fields of national land-use planning and regional governance. Multiple policy documents propose integrating LGI into spatial policies such as land-use planning, urban renewal, and local regeneration, establishing it as a core mechanism for regulating urban development, coordinating urban–rural construction, and balancing regional development. This discursive embedding not only enhances the operational feasibility of LGI in hardware planning but also demonstrates its governance potential in addressing regional disparities and population issues.

More crucially, recent policy documents have witnessed a marked increase in references to public–private partnership and multi-stakeholder governance, reflecting a shift in LGI from a focus on physical construction toward comprehensive management. For instance, numerous policies emphasize the roles of enterprises, communities, and academia in the design and implementation of LGI, leveraging platforms, promoting public–private partnerships (PPP), and refining financial mechanisms to enhance collaborative governance capacity. Keyword co-occurrences within the provided text data, such as “civil society”, “collaboration”, “local community”, and LGI, further solidify this discourse as a crucial underpinning of LGI’s governance model.

It is noteworthy that “institutionalization”, “regional culture”, “resilience design”, and “transverse collaborative systems”—cutting-edge expressions—reflect an attempt within certain policies to extricate LGI from a purely infrastructure-based logic and embed it within broader institutional frameworks and societal consciousness. These emerging terms suggest that LGI is evolving from a mere ecological/spatial strategy into a governance paradigm and strategic platform, with its degree of institutionalization and internalization becoming crucial topics for future policy research.

In summary, the discursive practices of LGI within Japanese national-level policy have expanded from a focus on natural ecological foundations and physical infrastructure development to encompass its integration into comprehensive policy tools encompassing disaster risk management, resource governance, spatial planning, and social collaboration. This trend in discursive extension not only demonstrates the diversification of LGI’s policy functions but also reflects a reconfiguration of its role within governance systems, foreshadowing the increasingly central strategic role that LGI will assume within future national governance structures.

4.3. Trends in Topic Evolution and Policy Agenda Shifts

A temporal analysis of seven categories of LGI-related policy topics reveals significant fluctuations in their respective attention levels. These dynamic shifts not only illuminate adjustments within the policy content itself but also reflect strategic shifts in national priorities regarding LGI functions across different developmental stages. Policy topics do not advance synchronously within the policy framework but rather exhibit phased intensification under specific contexts, demonstrating the sequential nature of policy agenda setting.

First, the topic “Institutional Promotion and Policy Practice” has experienced a rapid ascent since 2018, peaking in 2019 and 2021, reflecting LGI’s gradual transition from a peripheral concept into a formalized component within the policy regulatory system. This upward trend correlates closely with the Japanese government’s recent emphasis on green growth strategies, digital infrastructure, and cross-sectoral policy integration, signifying that LGI is evolving from a practical initiative to a standard element within national policy frameworks.

In contrast, the topic “Water Resources and Ecological Regulation” has maintained consistent and relatively high levels of attention throughout the time series. This indicates that it has become the most fundamental and enduring functional dimension within LGI policy. This sustained stability may suggest that water–ecological-system governance has achieved relative maturity both technically and institutionally to a certain extent.

Furthermore, the topic of “Regional Culture and Social Value Integration” exhibited significant activity between 2016 and 2020, peaking in 2016, after which it gradually declined. This period of heightened attention likely aligns with Japan’s policy orientations toward “local revitalization”, “beautiful national land creation”, and “cultural resource utilization”, emphasizing the integration of regional characteristics and historical culture into LGI promotion to enhance policy locality adaptability and social recognition. However, this topic’s marginalization in subsequent policies suggests that the cultural dimension has yet to achieve institutional stability and may still be in an exploratory phase.

The topic “Land Use and Spatial Integration” has received comparatively lower attention overall, experiencing only minor upticks in 2014, 2019, and 2020 while remaining relatively weak in other years. This trend may indicate that this topic currently exists more as a supplementary element within existing policies rather than a primary focus. Although LGI is inherently intertwined with land-space governance, its institutional articulation as a spatial planning tool remains insufficient. This suggests the need for further emphasis on LGI’s spatial attributes in future policy agendas concerning land formation and urban regeneration.

The topic “Disaster Risk Reduction and Resilience Building” experienced a notable surge in attention in 2016 and 2017, followed by a slight decline but maintaining an overall moderate level. It exhibits a pattern of strategic intensification during periods of heightened disaster risk, demonstrating its strong mobilizing capacity within acute policy agendas. However, its institutional sustainability during calmer periods requires further strengthening.

The topic “Ecosystem Protection and Nature Coexistence” reached its peak in 2016 and has since experienced an overall downward trend. This trajectory may indicate that it received heightened attention for a period, particularly during phases in which concepts of ecosystem services and nature coexistence gained significant traction. However, subsequent policy focus shifts toward institutionalization, collaborative governance, and other priorities have led to a relative dilution of attention for this specific agenda. Nevertheless, as a foundational core value of LGI, the topic’s institutional integration retains long-term significance.

The topic “Multi-stakeholder Participation and Collaborative Governance” exhibits a pattern of cyclical fluctuations, with notable prominence in 2015 and 2018, and a resurgence in 2020. This topic is often closely tied to institutional design and governance mechanism innovation, indicating that the exploration of public–private collaboration and multi-level governance plays a significant role in driving LGI policy implementation. However, its sustained attention has not yet materialized, suggesting ongoing challenges in institutionalizing collaborative mechanisms and a need for further refinement of policy tools and participation frameworks.

To conclude, the evolution of LGI within Japanese national-level policy processes has gradually revealed its multifaceted roles and complex functions, with its policy positioning continually adjusting in accordance with shifts in national strategic priorities. From a technological tool for addressing climate change and ecological degradation to a governance instrument guiding institutional transformation, and further to a symbolic carrier of regional culture and social values, the policy significance embodied by LGI exhibits stage-based variations. These evolving trends simultaneously illuminate that the institutional embedding strength of certain topics remains unstable, with their policy vitality potentially constrained by external strategic focus, exhibiting inherent volatility and ephemerality.

4.4. Pattern Differentiation of Inter-Departmental Coordination Structures

Based on the cosine similarity analysis of policy topic preferences, we identified a distinct “core–periphery” distribution of collaborative patterns among national government departments regarding the LGI agenda. MLIT, MOE, and CS form a highly concentrated cluster with similarity scores exceeding 0.86, demonstrating significant convergence in their policy attention to LGI. This high level of consistency reflects not only their similar policy orientations but also the overlapping responsibilities within their respective domains, particularly in cross-departmental issues such as land use, watershed management, and disaster risk reduction, which foster the potential for structural collaboration. Notably, these departments have already exhibited collaborative behaviors, including joint document releases, shared policy concepts, and harmonized legal clauses, forming a formalized collaboration axis that provides a stable foundation for horizontal integration and strategic coordination.

In contrast, MAFF demonstrates significantly lower similarity within the LGI policy framework. Its cosine similarity with other core departments is generally low, with a particularly low score of 0.226 with the CAO. This structural heterogeneity highlights a gap between its policy focus and the prevailing governance logic, suggesting its marginalization in cross-departmental policy design. Textual analysis reveals two main aspects contributing to this heterogeneity: First, LGI is not explicitly addressed in the MAFF’s current agricultural management policies, although it has surfaced in informal discussions and local-level practices. Given the critical role of farmland as a semi-natural space in ecological regulation and social infrastructure, this policy gap warrants attention in future institutional designs. Second, forestry policies exhibit a high degree of autonomy and lack semantic alignment with other departments on issues such as ecosystem protection and land-use planning, which could contribute to potential institutional fragmentation.

Furthermore, while national-level policies do not explicitly distinguish GI scale types, the issues discussed tend to implicitly reference LGI. This scale preference is more pronounced among the core departments, reflecting the strategic expectation of LGI being viewed as an institutional coordination tool at a broader level. However, due to the relatively late onset of systematic research on LGI in Japan, which only gained momentum after 2022, the delayed discourse in departments like agriculture and forestry may exacerbate collaborative barriers with the mainstream policy framework.

Overall, the LGI policy system displays structural axes of collaboration and peripheral nodes. The former offers potential for strategic integration, while the latter risks evolving into isolated institutional islands without effective embedding mechanisms. A key challenge moving forward is enhancing the integration capacity of low-coordination departments within a diverse policy system, which will be crucial for advancing the horizontal integration of LGI through targeted mechanism design.

5. Conclusions

This research employs a multi-faceted approach, combining text mining, qualitative comparison, and policy integration analysis to systematically examine LGI-related content within Japan’s national-level policy strategies. This comprehensive investigation unveils the characteristics and evolution trends of LGI across various dimensions, including themes, timeframes, distribution, and collaboration within relevant Japanese policies. By leveraging TF and TF–IDF methods to extract keywords and analyze their co-occurrence relationships, we identified four core themes and four potential development directions for LGI within Japan’s national-level policy landscape. Further analysis using LDA topic modeling categorized discussions related to LGI into seven overarching topics encompassing institutional promotion, water resource regulation, disaster risk reduction, ecological coexistence, spatial integration, multi-stakeholder collaboration, and cultural fusion. Building upon this foundation, we qualitatively interpreted topic preferences across different departments and their temporal evolution based on policy publication dates and departmental information. We further explored the consistency in preference structures among various departments, elucidating the connections between topics and national strategies, as well as highlighting the high degree of collaborative engagement between MLIT, MOE, and CS.

Through our discussion, we identified three crucial nodes in the development of Japan’s LGI policy positioning, along with the global thematic drivers behind each. We observed an evolving trend toward embedding LGI as a comprehensive management approach, shifting from its initial manifestation as concrete physical construction technology. This evolution is further illuminated by the influence of other strategic policies, revealing inherent instabilities in the LGI framework. We also clarified the “core–periphery” collaborative structures among relevant departments and identified fragmentation risks within the agricultural and forestry sectors. Notably, we found that while most policies do not explicitly differentiate GI scale types, their practical content often points toward large-scale LGI, reflecting the government’s strategic expectation of LGI as a tool for institutional coordination at a broader level.

It is worth noting that while the analytical framework employed in this study supports the core objectives and arguments, further methodological expansion will be necessary as more policy data become available. Future research should incorporate additional analytical approaches to deepen and broaden understanding of LGI’s policy positioning and to better connect theoretical insights with practical implementation.

In addition, although this study identifies structural fragmentation within Japan’s LGI policy system, it does not address the design of specific institutional tools or operational mechanisms. Future research could focus on institutionalizing cross-departmental coordination, such as through inter-ministerial consultation mechanisms, shared performance indicators, and joint policy development processes. These efforts would facilitate the translation of analytical findings into actionable strategies and strengthen the institutional embeddedness of LGI within complex governance systems.

In summary, Japan’s national-level LGI policy system has established a structured framework with diverse themes. However, risks persist in cross-departmental coordination and the stability of institutional embedding. Future policy development should prioritize strengthening communication mechanisms between departments, enhancing integration pathways for low-coordination sectors, and promoting higher levels of strategic integration and institutionalization of LGI within the national governance system. Given this study’s focus on national-level policy strategies, we did not delve into the specific transmission mechanisms between national and local policies. The practical implementation and spatial guidance of LGI often rely heavily on the execution of local-level policies. Therefore, future research should investigate the structural alignment and policy coherence between national and subordinate LGI frameworks, analyzing how key concepts and objectives are maintained, adapted, or reinterpreted across governance levels. This will provide a more comprehensive understanding of LGI’s multi-layered interaction mechanisms and governance efficacy.