MSPA was used to analyze the spatial patterns of terrestrial landscapes, producing a map of landscape types for the study area (Figure 4). The terrestrial cores covered 66,441.81 km², accounting for 12.83% of the total terrestrial area. They were concentrated in the northern Taihang Mountains, the Yanshan Mountains, and the Liaodong Hills, where topography limited human activity, resulting in large patch sizes and strong overall connectivity. However, in the Tai Mountains and the Jiaodong Peninsula, the number of landscape patches increased while patch size decreased, giving ecological sources a more scattered distribution.

At river estuaries, natural landscapes, such as extensive tidal flats and wetlands, dominated, with fewer internal patches. However, these patches exhibited high DPC values and elevated IIC scores and formed a belt-like distribution near the Yellow River estuary. The bridges covered 1,885.97 km², accounting for about 0.36% of the total area. Loops, branches, and islets together covered 274,137.47 km², or 27.41% of the terrestrial area, and served as components in the construction of the ecological network, indicating that ecological sources were relatively fragmented. Edges, situated between cores and major non-green landscapes, covered approximately 13,259.14 km², representing 19.96% of the core area. This suggested that the cores were relatively stable and had strong resistance to external disturbances.

Marine ecological sources were identified using marine functional zoning data and marine ecological redline data. These were overlaid with the terrestrial ecological sources. As shown in Figure 5, marine ecological sources covered 24,814.31 km². They primarily included the Dabijia Mountain Special Protected Island, the Shuangtaizi River Estuary Reserve, the Jinzhou Baishawan Tourism Area, the offshore fishery grounds at the top of Liaodong Bay, the Yalu River estuary, and the Dalian Spotted Seal Reserve.

Nearshore ecological sources were relatively limited, concentrated mainly on the northern and southern sides of the Yellow River estuary. These marine ecological sources provided a relatively favorable habitat for marine species. Across the study area, ecological sources were primarily distributed in forests characterized by high habitat quality and strong connectivity, and in areas with abundant water resources and high biodiversity. The identified ecological sources encompassed most of the region’s critical ecological functional zones, such as the Taihang Mountains, the Yanshan Mountains, the Yellow River, and the Liao River, indicating that the delineation of ecological sources in this study was consistent with actual terrestrial conditions, thus scientifically sound.

In this study, six resistance factors – land-use type, distance to roads, distance to rivers, elevation, slope, and marine functional zones – were integrated through weighted overlay to generate the spatial distribution of individual factors and a comprehensive land-sea resistance surface. The ecological resistance values ranged from 1 to 5. As shown in Figure 3, areas of high resistance were concentrated primarily in the northwestern mountains of the study area, including the outlying ranges of the Taihang Mountains and the Yanshan Mountains. Additional high-resistance zones appeared in scattered clusters across the North China Plain, the Liaohe Plain, the Shandong Peninsula, and the Liaodong Peninsula, and in the marine port and shipping areas, indicating that elevation and human activity were the dominant resistance factors. Low-resistance areas were distributed among plains, rivers, estuaries, and tidal flats, underscoring the critical role of rivers and water bodies in sustaining biodiversity and enhancing landscape connectivity.

Using the MCR model in combination with the circuit theory and graph-theoretic tools, land-sea ecological corridors were delineated, resulting in the ecological network of the study area (Figure 6). Terrestrial ecological corridors were primarily concentrated in the Liaoxi Corridor and the Taihang Mountains–North China Plain, and along the lower reaches of the Yellow River. Most occurred in forests, grassland, and other areas with strong natural ecological attributes, indicating that these regions provided multiple migration pathways capable of supporting diverse species habitats. Marine ecological corridors were mainly distributed in areas such as Lushun–Penglai, the Yalu River estuary, the Yellow River estuary, the Shuangtaizi River Estuary Marine Protected Area, and the aquaculture zone of Liaodong Bay. Although fewer in number, these marine corridors ran parallel to the coastline, linking major marine protected areas. Due to the influence of marine spatial utilization patterns, they were characterized by relatively simple functional structures and weak ecological connectivity. Future planning should incorporate additional ecological nodes and corridors to enhance the security and integrity of the regional marine ecological environment.

For coastal ecological corridors, river estuaries acted as overlapping and transitional zones between terrestrial and marine ecosystems, with distinctive biological, physical, and chemical characteristics. In the study area, rivers, such as the Yellow River, the Hai River, the Daling River, and the Xiaoling River, were key in linking coastal ecological sources. Specifically, the coastal ecological corridors of the Bohai Rim formed a C-shaped pattern, extending southward along the coastline, from Wafangdian (Dalian) through the Liaoxi Corridor to the Yellow River estuary in Shandong. The Liao River estuary corridor cluster was jointly formed by the Daling River and the Daqing River, while dense intersections of corridors occurred in the municipal area of Jinzhou and Linghai (Figure 6b). On land, major corridors extended northwestward, from the Daqing River to the Daliao River, and from the Beiputuo Mountain in Jinzhou eastward to Nanshan and to the Daling River, facilitating terrestrial species migration. At sea, corridors extended southwestward, from the coastal waters near the Liao River estuary to the coastal waters off western Liaoning, connecting the Daling River estuary, the Shuangtai River estuary, the Shihe River estuary, and the Xingcheng Taili Marine Nature Reserve and Conservation Area. These corridors provided flood discharge pathways for the Liao River estuary (the Red Beach Wetland) and supported the migration of fish species, such as so-iuy mullet, Chinese tapertail anchovy, and flathead grey mullet.

At the Yellow River estuary, coastal ecological corridors consisted of terrestrial and marine components (Figure 6b). On land, extensive Chinese tamarisk forests, coastal wetlands, and tidal flats formed one of the most complete warm-temperate wetland ecosystems, extending southward from the old Yellow River course through the Yellow River Delta National Geopark to the estuary. At sea, the corridors linked the National Aquatic Germplasm Resources Conservation Zone in the Taoer River estuary waters of Binzhou with the waters of Dongying’s Kenli and Dongying Districts, forming a continuous coastal corridor. Along the northern Yellow Sea coast (Figure 6b), the ecological corridors extended from the Yalu River estuary to Dalu Island and further to Changhai County, consisting mainly of coastal islands that connected the major river estuaries of the northern Yellow Sea. With gentle shorelines and rich species diversity, this area served as an important stopover site for migratory waterbirds and held significant ecological potential. Nevertheless, ecological corridors at the land-sea interface traversed areas of intense human activity, where species migration faced greater resistance, with a high risk of fragmentation.

Building on the”source identification–resistance surface construction–corridor extraction “paradigm, this study systematically optimized the technical framework for coastal ecological network construction through targeted innovations designed to address key limitations in existing research. For ecological source identification, multiple influencing factors—including land-use type, patch size, habitat quality, landscape connectivity, and spatial distribution—were integrated, with terrestrial ecological redline data incorporated to delineate terrestrial ecological sources. Drawing on Ke et al. (2024) and Chen et al. (2023), the study further strengthened the identification of marine ecological sources—a significantly underrepresented aspect in prior studies—by integrating marine functional zoning and marine ecological redline data to establish a marine ecological sensitivity evaluation system. Marine ecological sources were defined as areas characterized by rich species habitats, critical importance for ecological security and sustainable development, and high marine ecological sensitivity. This approach aligns with established principles of ecological source selection, ensuring scientific rigor, rationality, and objectivity in source delineation.

For resistance surface construction, natural and anthropogenic factors were jointly integrated to develop a land–sea unified resistance surface. Additionally, small patches exhibiting high habitat quality and strategic locations were included as supplementary ecological sources to enhance the completeness and robustness of the network structure. Beyond these methodological refinements, the study achieved a fundamental shift from a “land-centric” to a “land–sea balanced integration” approach in both the scope and composition of ecological sources. While earlier studies (Jin et al., 2021) primarily designated national or provincial nature reserves and large forest patches in mountainous and hilly regions such as the Yanshan and Taihang ranges as core sources, this study systematically identifies marine ecological redline zones, key estuarine wetlands, and special protected islands (the Dalian Spotted Seal Reserve) as marine ecological sources for the first time, which account for 27.2% of the total ecological source area (Figure 5). These marine sources not only serve as essential habitats for marine biodiversity but also function as critical hubs linking terrestrial ecological processes with nearshore marine ecosystems, thereby addressing the long-standing oversight in coastal ecological planning where marine spaces were often treated as passive receptors or background elements.

Furthermore, regarding the construction logic and spatial configuration of ecological corridors, this study advances from a “single optimal path” to a “multi-path probabilistic network.” Traditional approaches based on the Minimum Cumulative Resistance (MCR) model (Yan et al., 2021; Gong et al., 2024) typically generate a single least-cost corridor, which in the highly urbanized plains and coastal zones of the Bohai Rim is vulnerable to fragmentation due to built-up expansion and other anthropogenic pressures. By applying circuit theory—widely recognized for its ability to reflect realistic species movement patterns—and using the Linkage Mapper tool, this study models multiple probable dispersal pathways for species (Figure 6). Comparative analysis reveals that in key human–ecological conflict zones such as the Liaohe Plain and the Yellow River Delta, MCR-derived corridors often appear as narrow, linear features confined to residual natural vegetation. In contrast, the corridors identified in this study exhibit more complex, network-like, and parallel structures, uncovering previously overlooked “stepping stone” patches and alternative routes. This multi-path configuration enhances the resilience and redundancy of the ecological network, improves its stability under local disturbances, and better accommodates the fragmented landscape dynamics characteristic of the Bohai Rim region.

Coastal zones, as integrated spatial-geographical systems comprising the two core components of land and sea, host diverse natural resources, complex ecosystems, and multifunctional spatial uses. They serve as vital areas for both ecological conservation and socioeconomic development. However, accelerated coastal urbanization has led to increasingly severe ecological challenges, including marine environmental pollution, degradation of ecological functions, resource scarcity, and intensified fragmentation of ecological patches. These issues are particularly acute at the estuaries of major rivers such as the Liaohe, Haihe, and Yellow Rivers, where intense human activities intersect with critical ecological networks. Compounded by the persistent mindset of “valuing land over sea” and the entrenched model of “separate land-sea governance,” current management practices and research often focus on optimizing isolated elements. This approach fails to achieve the holistic integration of terrestrial ecological spaces and marine protected areas within unified planning concepts and technical standards.

The constructed Bohai Rim Coastal Ecological Network—featuring integrated land–sea ecological sources (terrestrial: 66,441.81 km²; marine: 24,814.31 km²), a hierarchical corridor system, and key interaction nodes—provides actionable scientific support for integrated land–sea governance. Its core contribution lies in bridging the traditional “land–sea divide” in ecological network research by establishing functional connectivity between fragmented terrestrial and marine habitats. This includes ecologically critical areas such as the Taihang–Yanshan mountain ranges, the Dalian Spotted Seal Reserve, and the Yellow River Estuary. By incorporating both natural and anthropogenic resistance factors into a unified land–sea resistance surface and applying circuit theory to delineate multi-path corridors, the network realistically captures species dispersal dynamics. It directly addresses the region’s most pressing ecological challenges, notably habitat fragmentation driven by intensive human activities—exemplified by coastal urbanization rates exceeding 70% and nearshore pollutant loads approaching twice the national average. This integrated structural and methodological framework ensures the network’s scientific rigor and enhances its operational relevance for biodiversity conservation and ecosystem management.

Beyond its structural innovation, the network delivers specific value for ecological protection and coordinated spatial planning. The identified ecological sources and corridors encompass approximately 90% of the key habitats for endangered species in the Bohai Rim, offering clearly defined spatial guidance for upgrading the regional protected area system. Core terrestrial patches in high-value mountainous and wetland regions—such as the Shuangtaizi River Estuary Reserve, which serves dual terrestrial and marine ecological functions—can be designated as “ecological protection redline core areas.” Within these zones, strict prohibitions on reclamation, industrial development, and other habitat-disrupting activities are essential to maintain ecological integrity. Marine ecological sources provide a strategic basis for expanding marine protected area coverage and formulating species-specific conservation plans, including the protection of spawning grounds for anadromous fish such as the so-iuy mullet. In spatial planning, the network’s “C-shaped” coastal corridor pattern and land–sea integrated nodes (the Yellow River Estuary and Jinzhou Linghai) offer practical guidance for siting coastal development projects (e.g., ports and industrial zones) away from ecologically sensitive corridors. This spatial optimization helps preserve the continuity of material and energy flows between land and sea, thereby aligning with the objectives of the Coastal Zone Protection and Utilization Plan (2021–2035) and improving the feasibility of land–sea coordinated governance.

Furthermore, the network strengthens the implementation of land–sea coordinated governance policies and provides precise, evidence-based guidance for ecological restoration. From a policy perspective, its outputs supply measurable indicators that respond directly to national strategic priorities for integrated coastal management. For instance, the finding that marine ecological sources constitute only 27.2% of the total source area highlights the systemic underrepresentation and inadequate protection of marine ecosystems within the current governance framework. This offers empirical justification for revising the Bohai Rim Ecological Environment Protection Plan to elevate the priority of marine habitat conservation. The hierarchical classification of corridors—based on gravity strength (≥800 for important corridors; 0–800 for general corridors)—enables differentiated governance: high-priority corridors require mandatory legal protection, while general corridors can be managed through incentive-based ecological compensation mechanisms that encourage restoration actions by local governments and enterprises. Moreover, the network pinpoints human disturbance hotspots, such as the coastal zones of Bohai Bay and Liaodong Bay where corridor fragmentation is severe. This enables targeted interventions, including the regulation of aquaculture practices and promotion of ecological relocation for industrial facilities, to reduce resistance to ecological flows and improve landscape connectivity. For ecological restoration, the network clarifies intervention priorities to enhance investment efficiency. Fragmented terrestrial corridors in the Taihang–North China Plain can be rehabilitated using “stepping stone” tactics, such as restoring small wetland patches and forest belts, to improve functional connectivity. Meanwhile, weakly connected marine corridors (within Liaodong Bay’s aquaculture zones) require focused measures like aquaculture zoning, water quality remediation, and tidal flat habitat conservation. Integrated restoration projects—such as the Yellow River Estuary wetland initiative, which links terrestrial Chinese tamarisk forests with offshore germplasm resource conservation zones—can maximize the cost-effectiveness of restoration investments and accelerate the recovery of integrated land–sea ecological functions, thereby supporting the long-term sustainable development of the Bohai Rim coastal region.

This study offers a feasible reference framework for constructing an ecological network in the Bohai Rim. Nevertheless, limited data availability and gaps in management systems prevented a comprehensive assessment of the region’s overall land-sea environment, internal ecological conditions, or the ecological networks of biological communities and species at finer spatial scales. Future research should take into account geographical variations across the study area, differences among ecological communities, and the socioeconomic conditions and ecological needs of terrestrial areas. This would help identify the factors influencing the complexity of ecological networks across linkages and interspecific relationships, select resistance factors appropriate to different communities and species, assign resistance values with greater scientific rigor, and build ecological networks at multiple scales. This, in turn, would enable detailed classification and targeted analysis, improving the feasibility and practical applicability of coastal ecological networks.

In assessing the importance of ecological patches, this study considered a limited set of factors, namely, morphology, area, positional importance, and overall habitat quality, leaving the evaluation incomplete. The choice of area thresholds involved a degree of subjectivity (Hou et al., 2022). Additionally, the resistance values assigned to ecological sources were composite values, which may not fully reflect the movement characteristics of particular species populations (e.g., amphibians), introducing potential errors into the simulation results. While ecological corridors were extracted using the circuit theory, their widths require careful consideration. Future research should account for species composition, traits, distribution, and actual conservation needs in the study area, enabling detailed classification and targeted analysis. Field surveys and observation data should be integrated to support parameter settings, and strategies for determining corridor width warrant a comprehensive study.