Research Overview on Isolated Wetlands

Abstract

Isolated wetlands, as a unique type of wetland, play a key ecological role in hydrological regulation, carbon storage, and biodiversity conservation. Although many studies have been conducted on the monitoring and ecological function assessment of isolated wetlands, a comprehensive and critical review is still lacking. Through a systematic analysis of the literature from the past two decades, we found despite the large number of existing studies on isolated wetlands, direct comparison between them is often difficult due to differences in definitions. Second, human activities and climate change are the primary factors affecting wetland hydrology and leading to wetland isolation in the short term. Third, remote sensing and landscape models serve as basic tools for monitoring and analyzing isolated wetlands, but the low temporal and spatial accuracy of relevant data, along with the short research time spans, limit in-depth studies. Finally, isolated wetlands have multiple ecological functions that exhibit spatial heterogeneity and change over time. In summary, isolated wetlands have indispensable ecological functions that are currently underestimated. It is necessary to scientifically define the concept of isolated wetlands, improve the capability and accuracy of long-term dynamic monitoring, and conduct multi-functional coupling research in the future. Additionally, when formulating future wetland protection and management strategies, attention should be paid to isolated wetlands, and the temporal and spatial differences in their ecological benefits should be considered.

1. Introduction

Wetlands, as one of the most productive and diverse ecosystems on Earth, serve as critical ecotones connecting terrestrial and aquatic environments, occupying a central position in global ecosystems [1]. Their unique hydrological, soil, and biogeochemical characteristics enable them to provide multiple ecosystem services, including regulating regional hydrological cycles, storing and transforming carbon as important carbon sinks, maintaining biodiversity, and improving surface water quality [2,3,4]. These functions not only sustain the global ecological balance but also provide essential natural resources and environmental safeguards for human societal sustainability [5]. However, under the dual pressures of global climate change and intensifying human activities, wetlands face severe challenges of area shrinkage and functional degradation, threatening ecological security and human well-being [6,7,8]. Among various wetland types, isolated wetlands have long been overlooked due to their specific geographic locations and hydrological features. Recent research, however, has revealed their irreplaceable roles in ecosystems [9], such as hydrological connectivity nodes, important sites for biodiversity conservation, and so on. Thus, conducting in-depth research on isolated wetlands is crucial for comprehensively assessing wetland ecological values and informing scientific conservation and restoration strategies.

Isolated wetlands are generally defined as wetland types completely surrounded by terrestrial habitats, lacking direct connections to surface water bodies such as rivers and lakes [2,10]. They exhibit substantial hydrological independence, with the water supply primarily dependent on precipitation, groundwater, and surface runoff rather than direct inflow from surface water. Historically regarded as hydrological “islands” and undervalued ecologically due to the lack of continuous surface water connections [2], isolated wetlands have received insufficient attention in conservation policies and management practices. Recent studies, however, have shown that they interact with other landscape units through material, energy, and biological exchanges. For example, they participate in regional hydrological cycles via surface runoff and groundwater exchange, and facilitate biodiversity maintenance through species migrations such as amphibians and birds. Additionally, as “biogeochemical reactors”, isolated wetlands play important roles in cycling carbon, nitrogen, and phosphorus, effectively storing carbon and purifying water to mitigate climate change impacts and enhance ecosystem services [11,12]. Although it is called “Isolation” in its name, isolated wetlands are actually closely connected to surrounding environments, with their ecological functions being indispensable for regional ecological health and human well-being.

In recent years, scholarly interest in isolated wetlands has increased; however, research remains limited in comparison to non-isolated wetlands that are hydrologically connected to rivers or lakes, particularly in terms of long-term, large-scale dynamic monitoring and functional assessments. Current studies primarily focus on hydrological dynamics, biodiversity conservation, and carbon cycling in isolated wetlands, but research on their ecological services such as nutrient cycling, water quality improvement, and climate regulation remains underdeveloped. Furthermore, inconsistent definitions and classification standards for isolated wetlands across regions and countries, due to the absence of unified international criteria, complicate cross-regional research and restrict the comparability and applicability of findings [13]. To address these challenges, this study systematically reviews the latest advances in definitions, dynamic monitoring, and ecological service functions of isolated wetlands. It further critically analyzes current research gaps and explores future research directions and priorities. Through this work, we aim to provide scientific references for the scientific conservation, effective restoration, and sustainable management of isolated wetlands.

2. Research Review Based on Bibliometric Analysis

Bibliometric and knowledge graph analyses were conducted using CiteSpace 6.2 software. For the literature selection, we retrieved studies from the WOS database over the past two decades and applied a g-index with k = 25 to filter highly influential and core relevant publications, focusing on key research in the field. In terms of analysis methods, we performed keyword clustering, keyword burst detection, and timeline mapping of keywords across different years.

CiteSpace identifies co-occurring keywords and citation associations in the literature. Using keywords as nodes and co-occurrence/citation relationships as links, it constructs a knowledge graph. Node size reflects the keyword frequency/influence, while color coding indicates the temporal evolution of research. Additionally, the tool identifies “citation bursts”—keywords with sudden citation surges. We ranked the top 25 bursts by intensity, which represent emerging frontiers experiencing rapid popularity growth in the field.

Figure 1a,b illustrate the evolutionary trajectories of the top 25 keywords with surging citation intensity in isolated wetland research during 2009–2025, revealing distinct developmental characteristics across three research phases. In the early stage (2013–2016), research centered on “isolated wetlands” (6.29) and “wetlands” (5.76), focusing on the fundamentals of isolated wetland ecosystems. In the mid-stage (2017–2019), the focus shifted to ecological processes and spatial associations, such as “nitrogen cycle” (3.38) and “landscape connectivity” (3.43), indicating diversification toward spatial-scale research. In the recent stage (2020–2025), “Surface water” (4.29) emerged as the highest-intensity hotspot, signifying that studies now transcend superficial analyses to investigate the structural mechanisms of isolated wetlands. Overall, research themes span three core domains: wetland ecology (seven topics), hydrological processes (five topics), and land use (three topics).

Research on “nitrogen” has the longest span (2017–2021). It coexists with emerging hotspots such as “heterotrophic nitrification” (2020). This shows two development trends in the field: the continuous deepening of basic research and the gradual expansion of new technical hotspots to spatial scales.

Analysis based on the timeline map of the literature keywords reveals the associated characteristics of research hotspots and keyword evolution over time in this field. As research on isolated wetlands was relatively scattered before 2013, the time series analysis starts from 2013. The research boom mainly occurred between 2013 and 2016. During this period, scholars focused on basic ecological fields. The dense red nodes in the knowledge map indicate that in recent years, the research focus has shifted to systematic exploration. This reflects both a deeper understanding of the integrity of isolated wetland ecosystems and a substantial increase in interdisciplinary integration. Specifically, the core of research has moved from basic studies such as #0 bacteria and #3 vegetation to systematic research centered on #1 hydrologic connectivity and #5 wetland dynamics. Chemistry (#7) and climate change (#4) form interdisciplinary connections through dense links, revealing the coupled mechanisms of carbon–nitrogen cycling and climate impacts on isolated wetlands (Figure 2).

3. The Definition of Isolated Wetlands

As a unique type within wetland ecosystems, isolated wetlands have not yet formed a unified global academic definition due to their special geographic locations and complex hydrological characteristics [5,6]. This situation partly results from differences in research focuses among scholars, leading to varied perspectives in their definitions (

Table 1. Definitions of isolated wetlands from the perspective of various discipline areas.

Academic Field OR Disciplinary Perspective	Definition OR Category	Country	References
Hydrological connectivity	A wetland completely surrounded by upland.	USA	[14]
Surface water connection	Wetlands that are not connected by streams to other surface-water bodies are considered to be isolated.	USA	[17]
Multi-pond systems	Geographically isolated wetland constructed for collecting rainwater for irrigation of crops. The ponds are interconnected with each other by ditches lacking persistent surface hydrological connectivity.	Jiangsu Province, China	[18]
Geomorphology	Geographically isolated wetlands (GIWs) are commonly reported as having hardpan or low hydraulic conductivity units underneath that produce perched groundwater, which can sustain surface water levels independently of regional aquifer fluctuations.	Kentucky, USA	[19]
Hydrology	GIWs to simply represent single depressions embedded into the landscape and not permanently connected to stream networks.	Florida, USA	[20]
Hydrological perspective and spatial perspective	Wetlands that lack contact with other water bodies and are relatively isolated in the landscape.	China	[15]

). For example, from the perspective of hydrological connectivity, Tiner defined isolated wetlands as “wetlands completely surrounded by highlands and lacking obvious surface water connections” [14]. This definition particularly emphasizes the physical separation of isolated wetlands from the surrounding water systems at the surface level, and it is particularly suitable for evaluating the independence of regional hydrology. Tian et al. hold similar views to that of Tiner, defining isolated wetlands as “wetland units that are in an isolated state in the landscape and have interrupted hydrological connections” [15]. This definition highlights the key roles of spatial differentiation and hydrological independence in the process of wetland degradation or protection. At the same time, many scholars define isolated wetlands from the perspective of regional characteristics, such as regional classifications like circular wetlands, dish-shaped depressions [16], prairie pothole wetlands, and dry salt lakes [14].

Although definitions of isolated wetlands vary due to scholars’ research objectives, “isolation” has always been widely recognized as the core characteristic of isolated wetlands [15]. However, it is worth noting that this isolation is not absolute. There may be certain ecological interactions between isolated wetlands and non-isolated wetlands or other water bodies through non-permanent, irregular, or seasonal hydrological connections, such as surface runoff after heavy rain or lateral groundwater recharge [21]. Based on the above analysis, we define isolated wetlands as wetlands that lack stable connections with other openly connected water bodies and long-term or periodically remain isolated in the landscape. This definition not only emphasizes spatial isolation and hydrological characteristics but also attributes the formation of isolated wetlands to changes in landscape patterns, reflecting the dual influence of natural processes and human activities. For example, during the expansion of agriculture or urbanization, large areas of wetlands are divided into numerous small isolated units. Their hydrological recharge may only depend on rainfall or groundwater, thus losing direct connections with the original river or lake systems.

4. Major Factors in the Isolation of Wetlands

The formation of isolated wetlands is the result of a combination of natural factors, human factors, and their interaction, and the causes may vary significantly in different regions. Geological, climatic, and anthropogenic factors (Figure 3) are the primary drivers of wetland isolation [16].

4.1. Geological Factors

Geological forces are one of the most direct driving forces in shaping isolated wetlands. For example, the isolated wetlands formed after the New Madrid earthquake in 1812 fully demonstrated the process of how earthquakes shape the terrain and promote the formation of isolated wetlands [22]. The mainstream view on the origin of Playas also attributes them to geological forces, believing that this special type of isolated wetland is formed by wind-driven processes or land subsidence [23,24]. Special topographic conditions serve as a “natural hotbed” for the formation of isolated wetlands. Basins, depressions, etc., are ideal sites for the formation of isolated wetlands [25]. For instance, the small depressions formed by glacial action are the basis for the formation of Prairie Potholes [26]. Meanwhile, the surface composition materials also affect the formation of isolated wetlands. For example, clay-rich Quaternary sediments have created favorable conditions for the formation of isolated wetlands in the Sanjiang Plain [16]. Additionally, freeze–thaw processes in the permafrost wetland environment of this region generate new water-accumulation areas through ground subsidence, thereby facilitating the development of isolated wetlands [27]. However, due to the prolonged nature of geological processes, their impacts on isolated wetlands are negligible over short timescales, and research specifically addressing these factors remains limited to date.

4.2. Climatic Factors

Climatic factors strongly regulate the isolation process of wetlands. Wetlands commonly experience multi-temporal-scale wet–dry cycles [20], directly controlled by temperature and precipitation dynamics. Isolated wetlands exhibit high evapotranspiration rates combined with disrupted surface water connectivity, making their hydrological balance dependent on input–output flux variations. These unique hydrological characteristics typically originate from progressive hydrological degradation [20]. The sensitivity to climatic fluctuations causes ecosystem services (e.g., water purification, biodiversity maintenance) to display strong climate dependency [28], thereby reinforcing isolation trends.

The US Environmental Protection Agency pointed out that inland non-tidal wetlands, such as isolated wetlands, are typically located in dry depressions. Their water sources mainly rely on precipitation, groundwater, or moisture in saturated soils. In arid and semi-arid regions, precipitation serves as a primary water source, substantially affecting the water levels, periodicity, and ecological functions of isolated wetlands. Precipitation is not only a key driving factor for the periodic water accumulation in these isolated wetlands but also directly participates in the formation and maintenance of wetland ecosystems [29,30]. For example, most Playas develop in wetland environments only when spring storms cause fresh water to collect in circular depressions [31]. Vernal Pools form through a similar process, usually filled by precipitation and snowmelt in spring, and are commonly found in Mediterranean climate areas and glaciated regions, such as California’s Central Valley and forested areas in the northeastern United States. By contrast, Peat bog wetlands rely more directly on precipitation for water and nutrients. Especially under arid conditions, changes in precipitation substantially impact the carbon sequestration function of Peat bog wetlands. It should be noted that precipitation not only drives the formation of isolated wetlands but also affects their hydrological functions, size, and shape by altering water pathways and soil permeability [32]. During periods of abundant rainfall, isolated wetlands may overflow their surface boundaries and connect with adjacent water bodies, temporarily enhancing their ecological connectivity [17].

Temperature factors and precipitation jointly affect wetland isolation through a synergistic mechanism. Taking the wetlands in the Sanjiang Plain as an example, from 1955 to 1999, the increase in temperature and the decrease in precipitation created favorable conditions for the formation of isolated wetlands, leading to an aggravation of the fragmentation of non-isolated marsh wetlands and a small increase in the area of isolated wetlands [33,34]. Similarly, the study on the fragmentation of wetland landscapes in the middle reaches of the Heihe River in China shows that from 1975 to 2010, the rise in temperature promoted wetland isolation directly or indirectly by enhancing evaporation and changing hydrological conditions, increasing the shape complexity of wetland patches and making them more fragmented, with the core wetland area decreasing by 42.54% [35]. Research on Pothole wetlands in the prairie regions of Canada also shows that in the future, temperatures will continue to rise, evaporation will increase, and the precipitation pattern will be characterized by an increase in winter (especially in December and January) and summer drought. This seasonal hydrological imbalance will further increase the isolation degree of isolated wetlands that rely on spring snowmelt for water replenishment [28], forming a positive feedback loop of “increased evaporation–decreased recharge–enhanced isolation”. In addition, intermittent streams and small-scale isolated wetlands (such as prairie potholes) are particularly sensitive to the peak flow time and the variation range of flow in spring [36], further highlighting the key role of climatic factors in isolated wetland ecosystems.

4.3. Anthropogenic Influencing Factors

Many wetlands that are geographically isolated are, in fact, the product of human activities [14]. Activities such as agricultural development, urbanization, and infrastructure construction have artificially fragmented the natural connectivity of wetlands. As one of the primary drivers of wetland isolation, human impact has continued to intensify over time.

Agriculture is one of the leading causes of wetland isolation. This includes activities such as livestock farming, crop cultivation, irrigation systems, groundwater extraction, and drainage projects [14,37,38]. For instance, in the 1980s, about 43% of Playas wetlands in the United States were damaged due to land clearing and drainage [39]. In the Dong Thap wetlands of the Mekong Delta, the mean patch size of wetlands dropped by 74.5% between 1990 and 2022. This change simplified complex ecological structures into regular-shaped, isolated patches and increased fragmentation [40]. Similar trends were also observed in China’s Naoli River Basin. Research shows that with the expansion of farmland, the proportion of isolated meadow wetlands rose from 49.4% in 1983 to 98% in 2000, and the isolation level of shrub wetlands reached 92.9% [41]. In the Prairie Pothole Region of North America, agricultural drainage is considered the primary cause of wetland area loss [42]. These examples show that agriculture promotes the shift of wetlands toward isolation through physical separation.

In addition to agriculture, urbanization has also accelerated the isolation of wetlands. With rapid socioeconomic development, urban construction and infrastructure projects—such as dams, river channel realignment, reservoir construction, and regulated water releases—have exerted significant pressure on various types of wetlands [14]. For instance, China’s Baiyangdian Wetland experienced a dramatic reduction in area from nearly 1000 km² in the 1960s to only 200 km² by 2013 due to urban expansion and agricultural development. The shrinkage of wetland areas can easily lead to habitat fragmentation and may eventually result in complete isolation of the wetland. A study in the Concepción region of Chile found that the Los Batros wetland lost 73% of its original extent over the past 40 years due to urban sprawl, becoming increasingly fragmented as a result of infrastructure and residential development [43]. Similarly, a study conducted in Orlando, USA, reported a 43.2% degradation rate in isolated cypress wetlands located within high-density urban zones [44]. Moreover, urbanization tends to exacerbate the isolation of already isolated wetlands. Those located on elevated terrain and surrounded by other land use types are more vulnerable to urban development and drainage modifications compared to wetlands near rivers, leading to alterations in their spatial structure [14]. These examples illustrate that urbanization not only contributes to the formation of isolated wetlands but also emerges as a critical driver of their ecological degradation over time.

5. Isolated Wetlands Monitoring Methodology

Traditional ground-based monitoring is the most direct method in wetland studies and provides accurate field data. However, it has several limitations. These include limited spatial coverage, poor temporal continuity, high costs, and potential disturbance to ecosystems. For example, Bayley et al. conducted a study in Jasper National Park, Canada, by setting fixed plots and measuring plant biomass through harvesting and weighing. The results were close to actual values. Yet, this method can damage vegetation and soil structure [45]. Frequent sampling may reduce local plant cover, disturb soil, or alter small-scale hydrological processes, affecting the natural environment of the wetland. Moreover, ground monitoring heavily relies on human labor. Sampling site selection is limited by the terrain, transportation, and available personnel. As a result, the data often lack sufficient spatial and temporal representativeness. These factors limit the efficiency and cost-effectiveness of traditional methods, especially for large-scale and multi-temporal wetland studies.

In contrast, remote sensing has become an important tool for monitoring isolated wetlands due to its wide spatial coverage, timely data access, and lower cost (

Table 2. Isolated wetlands monitoring methods.

Method	References
GIS and RS Methods	[49]
Multi-temporal Sub-pixel Landsat ETM+ Classification	[48]
Three-way combination of NWI, SSURGO, and DRGs	[50]
Geographic object-based image analysis	[51]
A Machine Learning Approach	[52]

). For instance, Frohn et al. used time series Landsat-7 images and spectral analysis to map isolated wetlands in the southeastern United States. Their results showed clear boundary detection [46]. Teferi et al. combined multi-source remote sensing data with NDVI and Tasseled Cap humidity indices to analyze wetland changes in the Choke Mountains, Ethiopia [47]. Recently, researchers applied a Multi-temporal Sub-pixel method to classify isolated wetlands in Cuyahoga County, OH, USA. The overall accuracy reached 92.8% (Kappa coefficient = 0.86). This was 13.8% to 27.8% higher than traditional single-date classification methods such as maximum likelihood or minimum distance classification [48]. These case studies show that remote sensing largely compensates for the spatial and temporal limits of traditional monitoring. It also reduces field interference and saves labor, improving efficiency. Remote sensing thus offers strong data support for the long-term management of isolated wetlands.

With rapid advances in remote sensing and geographic information system technologies, landscape dynamic change models have become increasingly important tools in landscape ecology [53]. These models are now core methods for analyzing wetland landscape pattern dynamics and their evolutionary mechanisms [54]. Landscape fragmentation creates isolated wetland patches [35], and these models offer scientific approaches to study fragmentation processes, isolation effects, and their ecological consequences through the quantification of spatial configurations and temporal changes in landscape elements. Based on functional differences, landscape dynamic change models can be grouped into two categories [55]. The first category includes landscape dynamic characterization models that describe static pattern features and change trends. Specific models in this group are the landscape dynamic degree model [56,57], relative change rate model [58,59], patch spatial centroid model [60], landscape gradient distribution model [61,62], and vector landscape direction index [63,64]. The second category contains landscape simulation models for predicting future landscape evolution, including Markov models [65,66] and cellular automata models [67].

Despite their wide application in forest, urban, and agricultural landscape studies, these models face greater challenges in isolated wetlands monitoring due to the small spatial scale and complex hydrological dynamics (e.g., seasonality) of such ecosystems. These characteristics demand higher-resolution data and more precise parameter settings [68], resulting in limited current applications primarily focused on spatial structural changes in isolated wetlands. For example, in the Sanjiang Plain of northeast China, Liu et al. applied a landscape metrics model combined with optimal grain size analysis to systematically investigate dynamic patterns of landscape spatial structure, revealing trends of shrinking wetland patch sizes and declining connectivity [69]. Zhang et al. integrated annual change rate analysis, standard deviation ellipse modeling, and the Integral Index of Connectivity to analyze dynamic patterns and patch importance values of isolated marsh wetlands from 1975 to 2020, demonstrating intensified isolation processes and substantial reductions in ecological connectivity among key patches [34]. These studies validate the applicability of landscape dynamics models for isolated wetland research while providing quantitative foundations for understanding degradation mechanisms and developing conservation strategies.

Current research on predicting isolated wetlands has made notable progress. A study using the WETSIM 3.1 model in North America’s Prairie Pothole Region found that a 3 °C temperature increase would raise wetland drought frequency, lower water levels, and densify vegetation. Combined with a 20% reduction in precipitation, this would accelerate core wetland degradation. However, a 20% increase in precipitation could partially mitigate the negative effects of warming, indicating that temperature and moisture jointly regulate wetland ecosystems [70]. Research on Canadian prairie wetlands further revealed that future climate warming will alter precipitation patterns: winter precipitation will increase (especially in December–January); however, the proportion of snowfall has decreased, and it has mostly turned into rainfall; the snowmelt period has advanced, with a 200% surge in winter runoff; and there is an 11% decrease in summer flows. This seasonal hydrological imbalance weakens the water storage capacity of isolated wetlands dependent on spring snowmelt, intensifying the isolation of highly enclosed systems [28]. Studies in both regions show that a climate-driven positive feedback mechanism—”increased evaporation–decreased recharge–enhanced isolation”—dominates the evolution of isolated wetlands. Additionally, methods like machine learning and spatial stream networks have been applied to simulate and predict isolated wetlands. For example, Riley et al. used a random forest algorithm to predict the flooding dynamics and hydrological cycles of small isolated wetlands. Their machine learning approach achieved substantially higher accuracy than previous methods, with the median balanced accuracy improving by 3–10% [52,71,72,73]. Golden et al. proposed the Spatial Stream Network model combined with the SWAT hydrological model, and after spatial autocorrelation correction, it passed the significance test with p < 0.05 (when the traditional SWAT model did not correct for spatial autocorrelation, it could not capture these relationships) [74]. This provided crucial support for dynamic wetlands monitoring.

Long-term dynamic monitoring of isolated wetlands currently faces multiple technical challenges, mainly in insufficient identification accuracy and lagging monitoring methods. These limitations directly hinder a comprehensive understanding of wetland dynamic change patterns. Current research mainly relies on landscape index analysis, field surveys, and remote sensing techniques. However, due to the spatial isolation of isolated wetlands (usually less than 1 hectare in area), their detectability is constrained by factors like the resolution of digital resources (e.g., 1 m resolution struggling to capture small wetlands) and obstruction from complex terrains. For example, in the identification of isolated wetlands in South Carolina’s Piedmont and Blue Ridge regions, true-color and near-infrared images only detected eight isolated wetlands. The remaining 36 cases (81.8%) showed no distinct features in aerial photos or supporting data (such as DEM layers) [75]. Combining traditional methods with emerging technologies has now become a key approach to address data and methodological gaps. Pitt et al., for instance, integrated local ecological knowledge with remote sensing to fill the detection gap for hidden wetlands in areas lacking high-resolution data [75].

6. The Ecological Services of Isolated Wetlands

Recent years have seen isolated wetlands emerge as a focal area in global ecological research. Numerous scholars have conducted valuable studies from diverse perspectives (

Table 3. The isolated wetlands ecological service functions.

Area OR Angle	Functions	References
Ecological	(1) Hydrologic and water quality functions (2) Habitat function	[77]
Landscape Connectivity	(1) Hydrological connectivity (2) Biogeochemical connectivity (3) Biological connectivity	[2]
Ecological	Maintain the biodiversity of many plant, invertebrate, and vertebrate groups (such as amphibians)	[76]
Centered Around Amphibians	(1) Hydrology (2) Vegetation (3) Ecological processes (4) Landscape-level restoration	[88]
	(1) Climate function (2) Hydrology and water quality functions (3) Habitat function	[15]
	(1) Hydrologic function (2) Habitat function (3) Geochemical cycle function	[9]

), with a steady rise in related publications [9]. Semlitsch et al. empirically demonstrated that small isolated wetlands serve as critical breeding grounds and habitats, playing an irreplaceable role in sustaining plant, invertebrate, and vertebrate populations [76]. Their ecological value should not be overlooked due to the limitation of their spatial extent. Leibowitz proposed a binary classification framework, categorizing isolated wetland functions into hydrological water quality regulation and habitat maintenance for biodiversity, emphasizing their distinctive landscape ecological niche [77]. Building on this, Tian et al. introduced climate regulation as a third dimension, establishing a three-dimensional functional framework [15]: climate regulation, hydrological water quality functions, and biodiversity conservation. Expanding to broader spatial scales, Cohen et al. applied statistical modeling to reveal the critical role of isolated wetlands in landscape connectivity, identifying three core functional modules [2]: hydrological connectivity [5,74], biogeochemical connectivity [3,17,21,78,79,80], and biodiversity support [81]. Liu et al. aligned with Cohen’s framework while highlighting substantial correlations between wetland functionality and spatial patterns, as well as hydrological dynamics [9], such as hydrological functions [36,82,83,84,85], habitat functions [86], and the geochemical cycle functions [87].

In general, current research primarily emphasizes isolated wetlands’ roles in hydrological regulation, material cycling, and biodiversity maintenance. Based on these findings, this study adopts a geographical perspective to comprehensively review their ecological services from five aspects (connectivity, runoff regulation/water storage, water purification, carbon cycling, and biodiversity functions) while considering interconnections among these functions.

6.1. The Hydroconnectivity Service Functions

For a long time, isolated wetlands have been viewed as hydrological “islands” due to their lack of obvious surface water connections. This traditional understanding stems from their apparent absence of direct runoff relationships with surface water systems like rivers and lakes; but this appearance does not mean they are functionally isolated [2]. Increasing research evidence shows that isolated wetlands are not completely disconnected from surrounding hydrological systems. Instead, they maintain dynamic hydrological connectivity with other landscape units through complex surface processes such as seasonal overflow and groundwater mechanisms like seepage and lateral recharge [89,90]. Take the geographically isolated wetlands in North America’s Prairie Pothole Region as an example. Model studies show their hydrological connectivity is not fixed but changes substantially with factors like rainfall intensity, terrain slope, and soil permeability [89]. Meanwhile, Thorslund et al. used an innovative chloride mass balance method to systematically quantify local runoff in 260 geographically isolated wetlands in North America. They found the average runoff of these isolated wetlands reached 120% of the basin average level, indicating they are not hydrologically isolated but important hydrologically active nodes in the basin [90]. This research strongly challenges the long-held assumption in laws and policies that isolated wetlands have low hydrological connectivity, highlighting their ecological value as key nodes for runoff generation and hydrological regulation. These studies demonstrate that the hydrological connectivity of isolated wetlands not only forms the basis of their ecological functions but also has a profound impact on the dynamic balance of basin hydrological processes.

6.2. The Runoff Regulation and Water Storage Service Functions

The hydrological regulation function of wetlands refers to the ability of wetland ecosystems at the basin scale to maintain efficient regulatory capacity. This is achieved through their special hydrological and physical properties, such as high soil porosity and strong soil-saturated water capacity, using the water cycle as a link to modify basin hydrological process [91,92]. In this process, isolated wetlands not only reduce flood peaks and maintain base flow during droughts but also regulate regional water balance and local climate conditions through interactions between surface and groundwater and evapotranspiration processes.

Studies show that isolated wetlands play a substantial role in regulating local and regional river flows, primarily by reducing high flows and supporting low flows [93]. For example, in the Chesapeake Bay Basin, the water storage and overflow mechanisms of isolated wetlands effectively regulate extreme precipitation during storms, substantially reducing flood peak intensity [32]. Small isolated wetlands located upstream can delay and reduce flood peaks through short-term water storage [21]. These wetlands respond rapidly to precipitation events, providing short-term retention of local storm runoff [32]. The effectiveness of reducing high flows and supporting low flows depends on the wetland water storage capacity [94]. Small isolated wetlands can effectively disperse and intercept daily rainfall runoff, substantially reducing peak flood flows by 11–12%. Large isolated wetlands play an important role in cumulative groundwater recharge due to their long water storage cycles [95]. Further analysis reveals notable spatiotemporal heterogeneity in the regulatory roles of isolated wetlands across different basin positions. Wu et al. indicated that upstream isolated wetlands play a substantial role in reducing flood peaks, capable of decreasing peak flood flows by 8.42%. Due to their weaker connectivity with rivers, downstream isolated wetlands have slightly less effectiveness in flood peak mitigation, reducing peak flood flows by only 6.92%. However, they play an important role in regulating the total flood volume [96]. Theoretical studies based on distributed hydrological models also indicate that there are substantial differences in the regulation of river flow by isolated wetlands at different locations within the watershed [93]. Additionally, recent studies found that runoff generation in isolated wetlands is generally 20% higher than the basin average [90]. This indicates that isolated wetlands act not only as hydrological “sinks” but also as active “sources” in regional runoff generation, further highlighting their key role in basin water balance and ecological services.

The hydrological regulation function of isolated wetlands is also substantially evident in water storage and groundwater recharge. A study of isolated wetlands in northcentral Florida using LiDAR data shows that isolated wetlands there have an average water storage capacity of 1619 m³/ha, with some isolated wetlands exceeding 2000 m³/ha [97]. Although lateral hydrological exchange in isolated wetlands is limited, they maintain the water supply for ecosystems through internal water cycles and regulate local runoff via vertical water infiltration and evapotranspiration [98], which is crucial for regional water balance. For example, isolated wetlands with strong storage capacity convert surface water to groundwater through soil infiltration, effectively recharging regional aquifers [17]. Especially during the dry season, these wetlands slowly release stored water, providing critical water sources for surrounding ecosystems and human activities. Additionally, evapotranspiration plays an important role in regulating local atmospheric moisture and the water cycle. In isolated forest wetlands with high vegetation cover, transpiration plays a dominant role; high transpiration regulates the local temperature through latent heat exchange [99].

6.3. The Water Quality Improvement Service Functions

Wetlands have unique advantages in removing nutrients and pollutants because of their high hydrological connectivity with various water bodies and inherent ecological functions [100]. They play a vital role in maintaining the ecological balance of the watershed and the stability of the water environment. However, overly strong hydrological connections can increase the input and exchange of pollutants but shorten the residence time of water in wetlands. This weakens some water quality improvement functions and reduces the ability to retain and transform nutrients [98]. Compared with wetlands with strong hydrological connectivity, isolated wetlands can enhance the retention and transformation of nutrients due to their longer hydraulic residence time. Although isolated wetlands seem relatively separated from the surface water system, they maintain dynamic interactions with surrounding water bodies through groundwater exchange, seasonal overflows, and surface runoff [89,90]. Although the treatment efficiency per unit area of isolated wetlands may be lower than that of riparian wetlands [3], their wide distribution and large number make their overall ecological contribution substantial. Therefore, isolated wetlands are important participants in water quality improvement.

Isolated wetlands show great potential in sediment retention and solute interception [32]. Their water purification function depends on a series of physical processes (such as sedimentation and filtration), chemical reactions (such as adsorption and redox), and biological mechanisms (such as plant uptake and microbial decomposition) [2,101]. For instance, after agricultural runoff flowed through an isolated wetland in the Dougherty Plain, the median values of nitrate, phosphate, ammonium, and E. coli decreased by 90.3%, 68.2%, 47.6%, and 71.3%, respectively. This fully demonstrates the strong purification function of wetlands in intercepting suspended particles, fixing nutrients, and transforming pollutants [102].

The water purification function of isolated wetlands exhibits obvious spatial heterogeneity [103]. Research shows that upstream wetlands mainly purify water by intercepting sediment particles in surface runoff. Midstream wetlands focus on retaining phosphates and reducing the migration of phosphorus through soil adsorption and plant uptake. Downstream wetlands perform excellently in denitrification due to the anaerobic environment and high microbial activity. Additionally, wetlands of different sizes also show disparities. Under transient hydrological conditions, small isolated wetlands (with an average of 88%) have a substantially higher nitrogen retention capacity than large isolated wetlands (with an average of 71%). The high evapotranspiration of small isolated wetlands temporarily interrupts their hydrological connection with the upstream watershed during the dry season, prolonging the residence time of nitrogen in the system and increasing the opportunities for microbial denitrification and plant uptake of nitrogen [104]. This mode of water loss further concentrates the nitrogen concentration and enhances its ecological function as a nitrogen retention terminal. Research in the agricultural development area of the Midwestern United States has confirmed that restored low-lying isolated wetlands can effectively adsorb phosphorus and remove nitrogen through the microbial denitrification process, substantially reducing the eutrophication threat of agricultural runoff to downstream water bodies [105]. Therefore, from the perspective of water quality protection, isolated wetlands of all sizes provide important service values for watershed ecosystems [3].

As important nodes in the terrestrial water cycle system, the hydrological connectivity and purification functions of isolated wetlands are highly susceptible to human activities, including agricultural drainage, urbanization construction, and excessive extraction of water resources. These disturbances not only weaken the hydrological connectivity of wetlands but may also alter soil structure and vegetation cover, reducing their capacity to remove pollutants [77]. Without effective management, these threats may cause regional water quality deterioration and endanger the long-term stability of watershed ecosystems.

6.4. The Carbon Cycle Service Functions

Wetlands, as important carbon pools on Earth, play a crucial role in the global carbon cycle [1,106]. Through plant photosynthesis, wetlands absorb carbon dioxide from the atmosphere. They convert the carbon elements into organic matter such as humus and plant residues, which are stored long-term in the soil [1,107]. These carbon sequestration processes not only help mitigate the greenhouse effect but also provide stable carbon reserves for global ecosystems. Although individual isolated wetlands are relatively small in area, their wide distribution makes these systems of non-negligible importance at regional and even global scales. Studies indicate that the relatively stable hydrological conditions of isolated wetlands, characterized by minimal water-level fluctuations and extended flooding periods, substantially reduce the decomposition rate of organic matter, thus promoting carbon accumulation [95]. For example, the carbon storage of isolated freshwater wetlands in temperate and tropical biomes accounts for more than 20% of the global peatland carbon storage [108]. In the middle reaches of the Magdalena River, the soil carbon concentration of isolated wetlands is substantially higher than that of riverine wetlands, with the average value being approximately five times that of the latter [109]. Similar findings were reported in wetland studies in Ohio, USA. Within the 0–24 cm soil surface layer, the carbon storage of isolated forest wetlands reaches 10.8 kg C/m⁻², much higher than that of riverine flowing wetlands (7.9 kg C/m⁻²) and slow-flowing marsh wetlands (8.0 kg C/m⁻²). This difference is mainly cause by the low oxygen diffusion rate and weak water scouring effect in isolated wetlands, which effectively slow down the mineralization and loss of organic carbon [110].

It is particularly important to note that wetlands serve not only as important carbon sinks but can also transform into carbon sources under changing environmental conditions. Wetland hydrological conditions directly influence the decomposition rate of organic matter, a process that determines both the long-term storage of carbon and the emission characteristics of greenhouse gases such as methane (CH₄) and carbon dioxide (CO₂). Due to their gentle hydrological fluctuations [109], isolated wetlands often remain in long-term water-saturated anaerobic environments. Under such status, the responses of isolated wetlands and wetlands are the same; though this condition restricts massive CO₂ release, it may enhance the activity of methane-producing bacteria, thereby increasing CH₄ emissions [111]. When the area or number of isolated wetlands decreases, their regulatory role in regional and global carbon cycles may change substantially. This may trigger a functional shift from carbon sinks to sources, exerting far-reaching impacts on the global greenhouse gas balance.

6.5. The Biodiversity Service Functions

Although isolated wetlands are limited in small areas and relatively isolated from surface water systems, their unique hydrological environments and habitat conditions make them important biodiversity hotspot areas [2,112]. Isolated wetlands play an irreplaceable role in maintaining regional biodiversity [113]. Geographic isolation is a key factor influencing species richness in specific habitats [114]. Due to long-term flooding or seasonal waterlogging, isolated wetlands combine the characteristics of aquatic and terrestrial habitats. They provide crucial shelters and breeding grounds for amphibians, waterbirds, wetland plants, and other organisms that depend on wetland environments [112]. This clearly demonstrates that isolated wetlands hold a significant position in the protection of regional ecosystems.

The relatively closed hydrological conditions of isolated wetlands can effectively block external pollutants and invasive species. They provide stable ecological refuges for specialized species that are water-quality sensitive or competitively disadvantaged. For example, a study in the Cilento Natural Park showed that invasive fish populations are increasing in non-isolated wetland systems, affecting the survival of amphibians. In contrast, no invasive species were detected in isolated wetland samples [115]. Additionally, isolated wetlands serve as important sites for the genetic exchange of certain species, acting as “natural protective barriers” in fragmented habitat networks. Take regions with typical isolated wetlands like Carolina Bays as an example. Their total species richness is substantially higher than that of mountain habitats lacking such wetlands [113]. This fully confirms the significance of geographic isolation in protecting native endemic biological communities.

However, this kind of isolation also reduces the frequency of species exchange among wetlands, limits genetic diversity and population dispersion, and may even lead to the extinction of some species [115,116]. Monitoring data show that although the number of amphibians in isolated ponds along the Baltic Sea coast increased substantially, the species richness index only rose slightly (a 16.7% increase from 2018 to 2022), which indicates limited introduction of new species and genetic flow [115]. Studies in the United States and China both reveal obvious limitations of isolated wetlands in species quantity and population genetic exchange. For example, a wetland study in Illinois forest reserves showed that the species richness of isolated ponds was about 60% lower than that of clustered ponds [117]. Comparative research in China’s Sanjiang Plain also found inconsistencies in the seed bank diversity between isolated wetlands and ground vegetation [118]. This duality reminds us that when evaluating the ecological effectiveness of isolated wetlands, we must balance their protective value against the risks posed by insufficient connectivity.

In recent years, many scholars have conducted in-depth research on protecting isolated wetlands to better maintain biodiversity. For example, the research by Heitmann et al. in South Carolina, USA, showed that blocking drainage ditches and restoring hydrological conditions can rebuild the ecological functions of wetlands [119]. The population dynamics models constructed by Harper et al. focusing on the Rana sylvatica and Ambystoma maculatum found that the buffer zone of appropriate width can significantly reduce the risk of regional species extinction and highlighted the critical role of overall landscape connectivity in maintaining the genetic diversity of amphibian populations and other species [112].

Studies on the Farancia abacura found a significant positive correlation between its habitat range and precipitation in isolated wetlands. Increased precipitation extends the flooding period of wetlands, thereby expanding the foraging and breeding spaces for this species [120]. These findings collectively confirm that the protection of isolated wetlands must follow the “core area–buffer zone” system principle. Protecting only the water body itself is insufficient to maintain population genetic diversity and long-term survival. Relevant studies agree that the conservation of isolated wetlands needs to shift from single waterbody management to landscape-scale integrated strategies to maximize their support for biodiversity.

6.6. The Service Functions Coupling

Ecological functions of isolated wetlands do not exist independently but form a tightly coupled ecological network through dynamic interactions (Figure 4). Within this network, different functional modules influence each other through hydrological, chemical, and biological processes. They maintain the wetland’s ecological stability and service functions together. These interactions can produce synergistic effects, but they may also trigger negative chain reactions under external disturbances. For example, in environments with low hydrological connectivity, extended water retention time enhances pollutant sedimentation and plant absorption. This improves the efficiency of water purification [104]. Meanwhile, prolonged water residence promotes the decomposition of organic matter under anaerobic conditions, contributing to carbon storage [11]. However, this process may also result in the accumulation of salts or pollutants, posing potential threats to local biodiversity. This reflects the coexistence of positive and negative effects within the ecosystem. Therefore, the key to protecting isolated wetlands is to maintain their natural hydrological fluctuations, strictly control external disturbances, and achieve a sustainable synergy of ecological functions through multi-objective management measures such as native vegetation restoration.

7. Discussion and Outlook

Isolated wetlands, as important ecosystems, play a key role in nature. They are not only unique types within wetland systems but also perform irreplaceable functions in maintaining ecological balance, supporting biodiversity, and promoting sustainable social development. However, with the intensification of global climate change and the expansion of human activities, isolated wetlands are facing increasingly serious threats of ecological damage. Although current research on isolated wetlands has made significant progress in areas such as hydrological functions, carbon cycling, and biodiversity, a comprehensive and systematic scientific framework has not yet been established. Facing the complex challenges of global environmental change, the protection and management of isolated wetlands still need to overcome many theoretical and practical bottlenecks. Therefore, future studies should strengthen the systematic and theoretical development of isolated wetland research to address the dual pressures of degraded ecological functions and increased conservation needs.

7.1. Harmonized Definition of Isolated Wetlands

Currently, definitions of isolated wetlands are diverse. There is still a lack of a universal standard that can meet the needs of multiple disciplines, such as hydrology, ecology, and management. This conceptual divergence not only limits in-depth academic research on isolated wetlands but also leads to insufficient public understanding of this ecosystem, thereby weakening conservation awareness. For example, the survey of private land users in rural areas around Charleston by Prochaska et al. (2021) showed that over 60% of land users were unaware of the negative impacts of their activities (such as drainage and landfilling) on wetland hydrological conditions and habitat quality [121]. This lack of awareness has also caused issues in legal practice. In the USA cases of SWANCC (2001) and Rapanos (2006), ambiguous definitions of “isolated wetlands” led to judicial disagreements on whether they should be protected under the Clean Water Act, resulting in ineffective implementation of conservation policies [122].

Definitions and classifications of isolated wetlands vary substantially across studies, leading to inconsistent trans-regional monitoring standards and making the direct comparison between different research endeavors difficult. Take the 10 regional types of isolated wetlands in the United States as an example: natural ponds are briefly defined as “natural water bodies fed by precipitation or snowmelt without surface runoff outflow”, while non-active floodplain wetlands in the same region emphasize their natural formation process but also note characteristics of human interference [14]. This shows that even within the same country or region, different definition and classification criteria lead to vastly different typological divisions. Such incompatibility has become a major bottleneck in scientific understanding and management practices. When research expands to other countries with different geomorphic features, hydrological conditions, and human impacts—or to a global scale—the development of unified definitions and classifications for isolated wetlands faces enormous challenges.

Future research should focus on developing a comprehensive definition system for isolated wetlands. This will promote systematic research and provide a standardized basis for classification and function assessment. Traditionally, definitions of isolated wetlands relied mainly on the single criterion of “surface hydrological isolation”. However, as the significance of surface hydrological isolation decreases, this approach becomes no longer suitable. The new definition system must break free from traditional limitations and instead be based on groundwater hydrological systems. By establishing hydrological threshold values and objective quantitative criteria, it can achieve multi-dimensional classification, thereby integrating hydrological dynamics with ecosystem services. For example, Zhang et al. identified isolated wetlands by setting a buffer zone threshold (10 m) centered on rivers and lakes. If a marsh wetland does not intersect with the rivers and lakes within the buffer zone and is not connected to any river wetland [34], it is determined to be an isolated wetland, that is, define and identify isolated wetlands in a quantitative form. While maintaining unified core concepts, the definition system must allow for adaptive adjustments according to differences in ecological zones (such as temperate and tropical regions). This will ensure the comparability of cross-regional data and coordination in management practices.

7.2. Long-Term Dynamic Monitoring of Isolated Wetlands

At present, there are several problems with the monitoring of isolated wetlands, such as short monitoring periods, difficulty in achieving continuous monitoring, and low accuracy. The combined application of multi-scale and multi-method approaches can effectively address these shortcomings. For example, an unmanned aerial vehicle remote sensing monitoring system with sub-decimeter spatial resolution (better than 5 cm/pixel) can be established [123]. This system should integrate with an artificial intelligence-driven data processing system to synchronously perform image correction, feature extraction, and anomaly detection during data transmission, enabling fully automated analysis throughout the process. Such technological integration not only enhances the efficiency of traditional wetland surveys but also effectively reduces subjective biases in manual interpretation through machine learning algorithms. It can substantially improve the accuracy of ecological parameter inversion, the ability to capture dynamic processes, and the continuity of long-term monitoring.

7.3. Integrated Evaluation and Multi-Functional Coupling of Isolated Wetlands Functions

Isolated wetlands, as unique ecosystems, are most notably characterized by their “isolation”. This characteristic makes them more sensitive to external disturbances such as pollution, climate change, and land use changes. However, most current functional assessment methods still use frameworks developed for non-isolated wetlands, focusing mainly on single functions like water quality purification or carbon storage. These methods overlook the integrity of isolated wetlands as a complete ecosystem, and due to their single-focused perspective, fail to reflect the coupling effects between their various functions [9].

To address the above issues, future research should take “isolation” as the core entry point to enhance the systematic and comprehensive nature of assessment frameworks. It is recommended to develop a multi-dimensional indicator system that covers key functions such as hydrological regulation, carbon cycling, and biodiversity support. Additionally, the assessment process must focus on the internal correlation mechanisms between these functions. For example, water level fluctuations may affect soil anaerobic conditions, thereby regulating both methane emissions and plant diversity simultaneously. Furthermore, isolated wetlands should be studied within broader landscape contexts to analyze their interactions with surrounding farmland, forests, or urban landscapes. Such a comprehensive and macro-level consideration will help more accurately reveal the interaction mechanisms among isolated wetland functions.

7.4. Biological Characteristics and Biological Connections

Isolated wetlands are key sites that support biodiversity and ecological functions. They host plant, animal, and microbial communities adapted to waterlogged environments. These communities are closely connected through food webs, symbiotic relationships, and gene flow. Despite geographical isolation, isolated wetlands can interact with broader ecosystems through groundwater flow and biological migration.

The biological characteristics and biological connections (such as gene flow) of isolated wetlands are affected by their “isolation” and “connectivity”. Increasing the regional wetland density by 30% can significantly promote the development of biodiversity [124]. Optimizing the wetland layout can enhance the connectivity of amphibian species [125] and facilitate biological connections. For example, the dispersal resistance of small mammals will decrease, which in turn increases the frequency of species exchange in communities. Meanwhile, the area of isolated wetlands should not be ignored. It changes the biological flow and distribution characteristics of other water bodies through cumulative and edge effects [2,126]. Their microclimatic conditions (such as light, temperature fluctuations) have a more significant impact on biological distribution patterns, often forming unique edge-dependent communities.

7.5. Ecological Restoration and Adaptive Management of Isolated Wetlands

Isolated wetlands have extensive ecological functions, including carbon sequestration, hydrological regulation, and biodiversity maintenance. These functions play a crucial role in regional ecological security and human well-being. Against the backdrop of the intensifying global climate change and ecological damage caused by human activities, isolated wetlands are facing increasingly severe degradation and loss. Although countries have achieved many remarkable results in the research of isolated wetlands, a complete and systematic scientific theoretical system has not been established yet. Climate change has brought many challenges to the protection and management of isolated wetlands, and there is an urgent need to explore effective solutions at both the theoretical and practical levels.

Future research should focus on exploring and applying ecological restoration techniques for isolated wetlands, especially restoration strategies based on natural processes, such as reconstructing the hydrological environment of isolated wetlands and reintroducing suitable vegetation. Additionally, dynamic monitoring data should be incorporated, and machine learning methods should be used to predict the response trends of wetlands, thereby optimizing the restoration priorities. For example, upstream wetlands can be restored first to enhance the regulation and storage capacity of the entire watershed. To ensure that restoration measures can achieve good ecological benefits while meeting social needs, interdisciplinary cooperation must be substantially strengthened. Integrating research perspectives from multiple disciplines, such as ecology, hydrology, and socioeconomics, will help establish a scientific and systematic theoretical framework for the protection and restoration of isolated wetlands, enabling more effective responses to the complex challenges posed by human activities and climate change.

Isolated wetlands have extensive ecological functions, including carbon sequestration, hydrological regulation, and biodiversity maintenance. These functions play a crucial role in regional ecological security and human well-being. Against the backdrop of the intensifying ecological damage caused by human activities, isolated wetlands are facing increasingly severe degradation and loss. Although countries have achieved many remarkable results in the research of isolated wetlands, a complete and systematic scientific theoretical system has not been established yet. Especially in the context of climate change, the protection of isolated wetlands is confronted with many challenges, and it is urgent to explore effective solutions at both theoretical and practical levels.

8. Conclusions

As a distinctive component of the wetland ecosystem, isolated wetlands have significant research value and play an important role in regulating the local microclimate and maintaining regional biodiversity. However, due to their characteristics of concealment and small size, there is no unified consensus on their definition at present, dynamic monitoring is limited, and there are still significant deficiencies in the in-depth analysis of the ecological processes and functional mechanisms of isolated wetlands. In the future, the research and protection of isolated wetlands urgently need to make breakthroughs in multiple dimensions. Firstly, systematically reveal the ecological functions and internal mechanisms of isolated wetlands to provide a solid theoretical basis for scientific protection. Secondly, establish a standardized and long-term ecological monitoring network as soon as possible to dynamically track the evolution trend of isolated wetland ecosystems. Finally, formulate corresponding protection strategies based on local actual conditions while coordinating the relationship between protection and development in accordance with the natural geography and socioeconomic conditions of different regions, so as to achieve sustainable utilization of isolated wetland resources.