1. Introduction
Wetlands are intricate natural assemblages resulting from the reciprocal interaction between water and land [
1]. Sustaining their position as fundamental constituents of significant ecological systems, wetlands perform a myriad of multifaceted functions [
2]. These encompass the regulation of climatic conditions, the provision of freshwater resources, and the preservation of biodiversity [
3]. Notably, wetlands assume a pivotal role in augmenting the caliber of urban ecosystems, upholding ecological equilibrium, enhancing ecological attributes, and fostering the advancement of urban sustainability [
4,
5]. Since the inception of the Ramsar Convention on Wetlands, there has been a growing global acknowledgment of the paramount importance and pressing need to strengthen the ecological optimization, restoration, and sustainable utilization of marsh wetlands [
6]. Furthermore, the international focus on marsh wetlands has transcended the singular emphasis on their role as waterfowl habitats, growing to encompass diverse areas, including wetlands’ optimization, restoration, conservation, and judicious utilization [
7]. This expanding perspective reflects the collective recognition of the multifaceted value and potential of marsh wetlands in fostering ecological integrity and the harmonious coexistence between human activities and natural systems [
8].
During the process of rapid urbanization, wetland resources in China have been excessively exploited and encroached upon [
9], leading to a significant degradation of ecosystem services. Pressing issues, such as fragmented wetland patches, reduced freshwater storage, and diminished flood regulation capacity, have emerged [
10], rendering wetlands incapable of meeting the requirements for sustainable urban development [
11]. Since China’s accession to the Ramsar Convention in 1992, research and conservation efforts pertaining to wetland ecosystems have gradually gained attention [
12,
13]. However, owing to the inherent complexity and dynamic nature of wetland systems, further exploration is necessary to establish a scientifically sound approach towards their protection [
14]. In light of these circumstances, China has undertaken a series of systematic planning initiatives for wetland regions, encompassing strategic planning, overall planning, detailed planning, and special planning [
15]. In practical terms, the establishment of wetland parks has preceded wetland-planning theory, a testament to the Chinese government’s renowned commitment to wetland conservation [
16,
17]. Consequently, the creation of national wetland parks in China has yielded remarkable achievements. At present, the predominant model for constructing national wetland parks prioritizes protection as the fundamental objective, while also promoting rational utilization and placing a significant emphasis on the ecological service value that surpasses mere economic gains [
18,
19]. From a planning standpoint, conducting wetland research that is rooted in spatial planning enables the allocation of physical space for wetland restoration purposes during urban development, thereby safeguarding wetland areas from encroachment by urbanization [
20,
21]. Nevertheless, the prevailing challenges in wetland planning encompass issues such as singular planning approaches [
22], spatial functional conflicts [
23], and inadequate coordination [
24]. The absence of a comprehensive mechanism to harmonize and coordinate spatial planning severely impedes the optimization of wetland spaces.
Wetland restoration plays a critical role in achieving ecological security and promoting sustainability. Pioneering the integration of macroscopic ecological principles with the optimized spatial allocation of land use, I. McHarg provided a comprehensive exploration of the application of spatial optimization to marsh wetlands in his seminal work
Design with Nature [
25]. Since the 1960s, numerous researchers and relevant governmental organizations have further advanced this theoretical framework, conducting practical investigations into marsh-wetland spatial planning using suitability analysis methods [
26,
27]. Notably, Forman’s 1995 publication
Land Mosaic exemplified a holistic optimization of marsh-wetland landscape patterns while systematically summarizing the approaches for the spatial optimization of these landscapes [
28]. Early studies primarily focused on optimizing artificial marsh wetlands to enhance their ecological environments [
29]. In recent years, scholars have also employed various optimization algorithms to spatially optimize small to medium-scale marsh wetlands from a landscape-pattern perspective. Connolly et al. explored the spatial optimization and restoration of marsh wetlands from a landscape-pattern perspective, using a simple weighted approach based on the principles of holistic planning [
30]. Qasaimeh et al. employed fuzzy mathematical theory to optimize the spatial design of artificial marsh wetlands, demonstrating the effectiveness of this method in artificial marsh-wetland optimization [
31]. Using a multiobjective approach, Meghna et al. optimized the spatial distribution of marsh wetland restoration results, with marsh-wetland landscape patterns as the objective function [
32]. By integrating landscape-ecology theory, regulating hydrological processes, and optimizing landscape spatial patterns and configurations based on the principles of landscape structure–process–function integration, Cai et al. enhanced landscape functions, such as water purification and biodiversity, in wetland parks [
33].
The insufficient recognition of ecological interdependencies has hampered the implementation of targeted measures and posed challenges to the conservation and optimization of wetlands. The accurate scientific identification and demarcation of wetland resources at the regional level are essential for effective wetland conservation [
34]. Furthermore, the rapid pace of urban expansion exacerbates the conflict between regional ecological conservation and development. Thus, it becomes crucial to proactively anticipate future urban-development scenarios, prioritize the protection of ecological spaces, and establish a harmonious relationship between wetland conservation and development through strategic planning [
35]. In summary, the current research on wetland spatial optimization largely centers around wetland evolution [
36], kernel density analysis [
22], distribution types [
37], and influencing factors [
38] to propose strategies for wetland spatial planning based on the analysis of spatial distribution characteristics. However, limited attention has been paid to the spatial relationships between wetlands, encompassing their interconnectivity, correlation, and a number of interconnected paths. This study aims to address this gap by conducting a comprehensive analysis of the spatial relationships between wetlands, utilizing Tianjin City as a case study, and leveraging the existing knowledge on wetland spatial distribution patterns. The objective is to present wetland spatial planning strategies and attempt to provide methodological insights for a useful exploration of spatial planning decision support for urban wetland systems.
5. Conclusions
In this study, we employed various methods to analyze the spatial issues related to wetlands in Tianjin City and proposed corresponding planning strategies to facilitate sustainable urban development in Tianjin. (1) Different analytical approaches were utilized to deepen the analysis beyond a single method. For instance, the nearest neighbor analysis identified the spatial distribution type of wetlands as dispersed, while the geographic concentration index revealed the uneven distribution of wetlands in Tianjin. Moreover, the Gini index indicated a high degree of imbalance in the distribution of wetlands within the city. These methods provided quantitative insights. Additionally, kernel density analysis visually represented the clustering patterns, offering spatial guidance for planning strategies. (2) Wetlands are not isolated entities in spatial terms; they exhibit varying degrees of interdependence. Spatial autocorrelation analysis can be employed to uncover the spatial relationships among wetlands across the entirety of Tianjin City, as well as to identify hotspots and cold spots in terms of wetland distribution. Such an analysis aids in identifying focal areas for wetland spatial planning. For instance, if there exists a spatial correlation among wetlands within the entire Tianjin City region, wetlands tend to exhibit either a “high–high” or a “low–low” clustering pattern. Expanding wetlands in proximity to existing ones can be considered by leveraging the spatial autocorrelation of wetlands. Furthermore, connectivity analysis can be used to assess the integrity of the wetland network in Tianjin City and evaluate the shortcomings associated with different wetland types. This analytical approach is instrumental in formulating spatial planning strategies tailored to the diverse wetland categories. Notably, medium-to-large-sized wetland patches in Tianjin City assume a pivotal role in preserving wetland connectivity and, therefore, necessitate targeted conservation initiatives. Consequently, wetland classification efforts should underscore the conservation significance attributed to medium-to-large wetland patches. (3) Subsequent to the implementation of the spatial planning strategies, the optimized spatial distribution of wetlands in Tianjin City was substantiated through the employment of spatial distribution analysis and spatial relationship analysis methods. This validation process resulted in the addition of a total of 294 wetland patches, leading to a significant increase of 4.63 percentage points in terms of wetland coverage. Notably, the previously clearly prevalent inequitable distribution of wetlands underwent a transformative shift towards a comparatively balanced configuration. The spatial extent of “high–high” wetland aggregation zones expanded, thereby amplifying wetland interconnectivity. Moreover, when considering the distance thresholds of 2.5 km, 5 km, 7.5 km, and 10 km, the wetland ecosystem in Tianjin City exhibited respective enhancements in the IIC of 0.0228, 0.0315, 0.0395, and 0.0531, respectively. These cumulative improvements collectively contributed to an overall enhancement in wetland connectivity.
In the broader context of wetland conservation research, it is evident that many studies have overlooked the recognition of ecological relationships among wetlands, resulting in limited spatial applicability in their planning efforts. This study, in contrast, incorporates spatial distribution correlations, connectivity metrics, and pathways among wetlands into its framework. This comprehensive approach enhances the basis for strategic decision-making and augments the practical guidance for wetland planning. It is important to note that previous research [
17] has underscored the close linkage between human wellbeing and the surrounding environment, emphasizing the significant impact of wetland quality on the physical and mental health of nearby residents. While this study did not consider the ecosystem services provided by wetlands and their implications for human wellbeing, it acknowledges the need for future investigations into the ecological valuation of wetland resources and the development of planning methodologies aligned with value-conversion pathways. This stands as a key agenda for future research endeavors. In the future, we also plan to conduct research on multitemporal data using the future multiscenario simulation method based on historical data validation to develop more comprehensive spatial planning strategies for wetlands. Furthermore, the validation of these planning strategies is crucial to ensuring their accuracy and scientific rigor. Overall, this study’s findings can be extrapolated to other cities or regions and can serve as a foundation for investigating spatial planning strategies pertaining to additional ecological elements, such as forest ecosystems.
Some limitations of this study should be acknowledged. The primary focus of this paper lies in examining the ecological attributes of wetland spaces and analyzing their ecological spatial distribution and relationships. However, the concept of spatial planning has evolved to encompass a holistic approach that incorporates multiple elements, including social, economic, and ecological factors. To address these limitations in future research, we recommend incorporating additional attributes, such as the social characteristics of wetlands. Concurrently, network analysis techniques can be employed to assess the accessibility of wetlands for the population. By integrating these diverse aspects, a comprehensive wetland spatial planning strategy can be developed that not only maximizes ecological benefits but also takes into account social advantages, thus achieving a win–win outcome through nature-based solutions.