Yancheng Coastal Wetland Research Articles

Classification of plants based on time-series SAR coherence and intensity data in Yancheng coastal wetland

ABSTRACT Investigating coastal wetland plant communities is of great significance for wetland monitoring due to the important functions of coastal wetlands, such as maintaining biodiversity and mitigating global climate change. Current studies on wetland plants mostly rely on optical data, with few utilizing synthetic aperture radar (SAR) data. Moreover, these studies often analysed single temporal SAR data, which limited the exploration of the valuable information present in time-series SAR data. Therefore, in this paper, we proposed a technique for mapping coastal wetland plant types based on time-series SAR coherence and intensity data to fully utilize the information from these data. We utilized Sentinel-1 Single Look Complex (SLC) images covering the Yancheng coastal wetland for the entire year of 2021 to investigate the effectiveness of using dual-polarization interferometric coherence and intensity-derived information from time-series Sentinel-1 data as features for classification. Plant classification was conducted using support vector machine (SVM) and random forest (RF) methods. Our results demonstrated that integrating time-series dual-polarization coherence and intensity-derived information resulted the best classification accuracy, with an overall accuracy (OA) of 89.79% and a Kappa coefficient of 0.858. This highlights the effectiveness of combining coherence and intensity data from time-series Sentinel-1 for monitoring plant cover in coastal wetlands.

Blue carbon storage of tidal flats and salt marshes: A comparative assessment in two Chinese coastal areas

Coastal wetlands are blue carbon (C) reservoirs and play an important role in mitigating climate change by efficiently capturing and storing organic carbon (OC). However, assessments of blue C sequestration focus primarily on soil organic carbon (SOC) inventories of vegetated coastal ecosystems and often neglect the potential of tidal flats to sequestrate C. To address the issue, a comparative assessment was carried out for two representative coastal wetlands in China: the Yellow River Delta and Yancheng coastal wetlands. The study focused on distinct types of coastal ecosystems including unvegetated tidal flats and three types of salt marshes vegetated by either Spartina alterniflora, Suaeda salsa, or Phragmites australis. We combined field sampling and data synthesis to assess the OC stock of different coastal areas and evaluate the regional OC storage. The results indicated that vegetated salt marshes exhibited higher OC stocks per unit area compared to unvegetated tidal flats in both regions. Interestingly, tidal flats in the Yellow River Delta displayed comparable OC stocks to S. salsa marsh on the Yancheng coast. The regional OC storage was estimated to be 5.64 ± 0.61 Tg C for the Yellow River Delta and 9.96 ± 1.52 Tg C for the Yancheng coast. Tidal flats with low SOC stock per unit area were the primary contributors to regional OC storage, accounting for over 75 % of the total. This predominance was attributed to the extensive distribution of tidal flats along China's coast, indicating their significant potential as blue C sinks. Overall, this study provides insights into the OC storage potential of various wetland types in China and highlights the importance of considering tidal flats in estimates of blue C sequestration.

Contamination status, source analysis and exposure assessments of quinolone antibiotics in the south of Yancheng Coastal Wetland, China.

Yancheng coastal wetland, the largest coastal wetland in the west coast of the Pacific Ocean and the margin of the Asian continent, has significant environmental, economic and social effects on local human beings. The extensive contamination and potential risk of quinolone antibiotics (QNs) on local aquaculture and human health are still not clear until now. In this study, 52 surface sediment samples were collected to investigate the contamination status and polluted sources, and evaluate ecological risks of QNs in the south of Yancheng coastal wetland. The total contents of QNs ranged from 0.33 to 21.60ng/g dw (mean value of 4.51ng/g dw), following the detection frequencies of QNs ranging from 19.23 to 94.23%. The highest content of QNs occurred around an aquaculture pond dominated by flumequine. The total organic carbon contents of sediment were positively correlated with sarafloxacin and lomefloxacin (p < 0.05), indicating the enhanced absorption of these QNs onto sediments. Partial QNs, such as lomefloxacin, enrofloxacin, sarafloxacin and flumequine, presented the homology features originating from the emission of medical treatment and aquaculture. There was no potential risk of QNs to human beings but a potential risk to aquatic organisms (algae > plant > invertebrate). Totally, the management and protection of Yancheng coastal wetland should be of concern with aquaculture as the important industry.

Vegetation Classification and Evaluation of Yancheng Coastal Wetlands Based on Random Forest Algorithm from Sentinel-2 Images

The identification of wetland vegetation is essential for environmental protection and management as well as for monitoring wetlands’ health and assessing ecosystem services. However, some limitations on vegetation classification may be related to remote sensing technology, confusion between plant species, and challenges related to inadequate data accuracy. In this paper, vegetation classification in the Yancheng Coastal Wetlands is studied and evaluated from Sentinel-2 images based on a random forest algorithm. Based on consistent time series from remote sensing observations, the characteristic patterns of the Yancheng Coastal Wetlands were better captured. Firstly, the spectral features, vegetation indices, and phenological characteristics were extracted from remote sensing images, and classification products were obtained by constructing a dense time series using a dataset based on Sentinel-2 images in Google Earth Engine (GEE). Then, remote sensing classification products based on the random forest machine learning algorithm were obtained, with an overall accuracy of 95.64% and kappa coefficient of 0.94. Four indicators (POP, SOS, NDVIre, and B12) were the main contributors to the importance of the weight analysis for all features. Comparative experiments were conducted with different classification features. The results show that the method proposed in this paper has better classification.

Study on the impact of reclamation and development of Yancheng coastal wetlands on the spatio-temporal evolution of wintering Anatidae habitat

As a World Natural Heritage Site primarily focused on protecting migratory bird habitats, the Yancheng coastal wetland is also an important land resource reserve area in China. With a long history of reclamation, the impact of reclamation on waterbird habitats has attracted widespread attention. Therefore, this study was based on the distribution data of wintering Anatidae from 1987 to 2020 and coastal land reclamation data. The landscape development intensity (LDI) index and MaxEnt model were used to reveal the spatiotemporal changes in reclamation development intensity and identify the spatiotemporal evolution characteristics of Anatidae habitats. A geographical weight regression (GWR) model was used to analyze the local differences for the impact of changes in reclamation development intensity on the spatiotemporal distribution of Anatidae habitats. The results showed that the area of land types with higher reclamation intensity in the study area increased rapidly from 1987 to 2020, and the overall reclamation intensity showed a pattern of low in the northeast and high in the southwest. The high-intensity range in 1987 was 5.01 ∼ 6.00, and the reclamation intensity in the western area of Dafeng to Tiaozini was generally greater than 8.01 in 2020. From 1987 to 2020, the population of Anatidae first decreased and then increased, with a clear southward shift in spatial distribution. The evaluation results of suitable habitats revealed that the most suitable area significantly declined from 1280.76 hm2 in 1997 to 60.19 hm2 in 2020, which indicated that the patch space of high-quality habitats was further compressed. The area with the greatest positive impact for the intensity of reclamation and development on habitat suitability from 1987 to 1997 was concentrated near the Beihuanchong area, while in 2007, the negative impact was mostly distributed in the northern and western Hexin area. The regression coefficient ranged from −0.665 ∼ -0.513. The negative impact of reclamation and development further deteriorated in 2020, with a negative correlation coefficient ranging from −1.642 ∼ -0.699. There were significant differences in the impact of environmental variables on the distribution of Anatidae habitats in different periods. In this study, a habitat protection and restoration pattern for Anatidae is proposed, which may provide an important reference for the protection of wintering Anatidae populations and the structural restoration of habitats in Yancheng coastal wetlands.

Research on Grus japonensis habitat requirements for developing restoration plans

As an endemic species in Asia, Grus japonensis reproduction and survival rely on natural wetland resources. In the Yancheng coastal wetlands, the wintering habitat of Grus japonensis had been destroyed due to rapid social and economic development. At the same time, its population also declined leading to land use changes. Therefore, it was urgent to conduct scientific restoration and management of the winter habitat. Based on the structural habitat demand for Grus japonensis, traffic light warning analysis and landscape structure index system were used to guide habitat restoration. The main conclusions were as follows: the population of Grus japonensis in Yancheng coastal wetlands reached its highest recorded number of 952 in 2000. The population showed a tendency to concentrate in the core area (CA) of the Yancheng National Nature Reserve (YNNR). The locations of restoration areas under yellow, green and peak historical state were determined by the traffic light warning analysis. Landscape indicator thresholds were set based on the landscape conditions of the habitat in 2000. After restoration, the habitat should contain at least two landscape types: Phragmites australis (P. australis), Suaeda salsa (S. salsa) and ponds, with a minimum patch area of 5.22–19.11 km2 and 5–17 patches. Habitat should be located at least 500 m from roads and farmland and 1000 m from residential areas. From the perspective of improving landscape diversity, “P. australis-pond habitat”, “P. australis-S. salsa habitat”, “Continuous P. australis habitat” and “Continuous S. salsa habitat” were constructed by landscape patterns. Finally, according to the land use situation around the habitat, the “Friendly” land use layout of “Salt marsh wetland--Low intensity ecological aquaculture pond--Farmland--Construction land” from sea to land was developed. This mode provides a reference for the habitat restoration of coastal wetlands.

From separation to incorporation: Development of a unifying framework that integrated bird habitats with public recreation spaces within the wetland park system

The Ramsar Convention places central emphasis on the protection, restoration, and utilization of wetlands. Wetland species and their habitat protection is an important embodiment of wetland system protection. Simultaneously, the importance of recreation as a form of human activity within wetlands should not be underestimated. Wetland parks, as a mode of rational wetland use, provide the public opportunities for leisure and entertainment, exemplifying China's commitment to the Ramsar Convention on Wetlands. However, With the acceleration of urbanization, the degree of fragmentation of the wetland system is increasing. The wetland park and its surrounding landscape elements are separated from each other, resulting in the phenomenon of islanding, which is not conducive to the protection and utilization of wetland biodiversity. This study focuses on Yancheng coastal wetland, a UNESCO World Heritage site in Jiangsu, China, as its research area. It integrates habitat birds, a core component of wetland biodiversity, into the development framework of wetland parks. The study proposes the use of composite habitat corridors to connect fragmented bird habitats with public recreational areas, establishing a collaborative wetland park system. The methodology involved three key steps: (1)Spatial Modeling. Utilizing Maxent, the spatial distribution of birds and public recreation areas was modeled, and suitable patches for both were extracted. (2) Corridor Identification. Linkage Mapper was employed to identify bird and recreational corridors, while the MCR model was used to pinpoint composite habitat corridors. (3) Network Development. Corridors generated in the previous step were superimposed on the ArcGIS platform to create a network of interconnected bird habitats and public recreation areas within the wetland park system. The study's results demonstrate: (1) There are obvious spatial distribution differences between the current core bird habitat and public recreation areas in Yancheng coastal wetland. (2) The establishment of a composite corridor network realizes the interconnection between bird habitats and public recreation areas，among them, the corridor network in the southern region is short and dense, with higher stability. (3) The areas passed by the composite corridor network are mainly productive landscapes such as cultivated land and aquaculture ponds, and therefore, certain protection and restoration measures should be taken to create suitable habitat conditions for birds and humans. This study provides a novel model for wetland protection and sustainable utilization, particularly relevant to many developing countries facing similar challenges.

Monitoring Spartina alterniflora Expansion Mode and Dieback Using Multisource High-Resolution Imagery in Yancheng Coastal Wetland, China

Spartina alterniflora (smooth cordgrass), China’s most common invasive species, has posed significant challenges to native plant communities and coastal environments. Monitoring the invasion and dieback process of S. alterniflora by multisource high-resolution imagery is necessary to manage the invasion of the species. Current spatial analyses, however, are insufficient. As a result, we first extracted S. alterniflora by integrating multisource high-resolution images through the multiscale object-oriented classification method, then identified the expansion patterns of S. alterniflora on the seaward side by the landscape expansion index, and conformed the main drivers of S. alterniflora dieback on the landward side in the Jiangsu Dafeng Milu National Nature Reserve. The findings revealed that the area of S. alterniflora decreased in size from 1511.26 ha in 2010 to 910.25 ha in 2020. S. alterniflora continues to grow to the sea and along the tidal creek on the seaward side, with a total increase of 159.13 ha. External isolation expansion patterns accounted for 65.16% of the total expansion patches, with marginal expansion patches accounting for 24.22% and tidal creek-leading expansion patches accounting for 10.62%. While the landward side showed a declining trend, the total area decreased by 852.36 ha, with an annual average change rate of 8.67%. S. alterniflora dieback was negatively related to the number of tidal creeks and positively related to the number of wild Elaphures davidianus and the length of artificial ditches. Our findings provide a scientific foundation for the ecological control of S. alterniflora. Its presence in coastal wetlands inspires evidence-based protection and management strategies to protect the coastal wetland ecosystem.

Semantic Segmentation of China’s Coastal Wetlands Based on Sentinel-2 and Segformer

Concerning the ever-changing wetland environment, the efficient extraction of wetland information holds great significance for the research and management of wetland ecosystems. China’s vast coastal wetlands possess rich and diverse geographical features. This study employs the SegFormer model and Sentinel-2 data to conduct a wetland classification study for coastal wetlands in Yancheng, Jiangsu, China. After preprocessing the Sentinel data, nine classification objects (construction land, Spartina alterniflora (S. alterniflora), Suaeda salsa (S. salsa), Phragmites australis (P. australis), farmland, river system, aquaculture and tidal falt) were identified based on the previous literature and remote sensing images. Moreover, mAcc, mIoU, aAcc, Precision, Recall and F-1 score were chosen as evaluation indicators. This study explores the potential and effectiveness of multiple methods, including data image processing, machine learning and deep learning. The results indicate that SegFormer is the best model for wetland classification, efficiently and accurately extracting small-scale features. With mIoU (0.81), mAcc (0.87), aAcc (0.94), mPrecision (0.901), mRecall (0.876) and mFscore (0.887) higher than other models. In the face of unbalanced wetland categories, combining CrossEntropyLoss and FocalLoss in the loss function can improve several indicators of difficult cases to be segmented, enhancing the classification accuracy and generalization ability of the model. Finally, the category scale pie chart of Yancheng Binhai wetlands was plotted. In conclusion, this study achieves an effective segmentation of Yancheng coastal wetlands based on the semantic segmentation method of deep learning, providing technical support and reference value for subsequent research on wetland values.

Coastal wetland restoration framework based on hydrogeomorphic units of the coastal wetland of Yancheng, China

Effective implementation of restoration projects is essential to solving the degradation of coastal wetlands. Due to the lack of systematic guidance or unsuitable engineering measures, some coastal wetland restoration projects have suffered from lower-than-expected results and poor sustainability. Therefore, it is necessary to construct a regional-scale wetland restoration framework from a macro perspective prior to project implementation, which can guide pre-study and follow-up restoration practices. In this study, the hydrogeomorphic units (HGUs) of Yancheng coastal wetlands were delineated according to the regional hydrogeomorphic conditions, and the changes in land use/cover and hydrological connectivity of each HGU from 1980 to 2019 were analyzed. The results showed that the area of natural wetlands in the study area declined rapidly, with a decline of 48.38%, and was mainly converted to aquaculture ponds or farmland during the 40 years. The structural complexity and transport capacity of tidal creeks decreased significantly, which indicated that the hydrological connectivity decreased. The main problems of degradation in the region were the reduction of large areas of natural wetlands, the rapid expansion of exotic species, and the decline in hydrological connectivity, etc. Combining the degradation problems and the restoration objectives, feasible strategies and methods were selected for different types of HGUs from both active and passive restoration categories, thus forming a coastal wetland restoration framework for the Yancheng coastal wetlands based on HGUs. This study takes regional hydrogeomorphology as the antecedent context condition, and the idea of a systematic restoration framework constructed by combining landscape perspectives can provide scientific support for wetland restoration practice.

Coastal Aquaculture Extraction Using GF-3 Fully Polarimetric SAR Imagery: A Framework Integrating UNet++ with Marker-Controlled Watershed Segmentation

Coastal aquaculture monitoring is vital for sustainable offshore aquaculture management. However, the dense distribution and various sizes of aquacultures make it challenging to accurately extract the boundaries of aquaculture ponds. In this study, we develop a novel combined framework that integrates UNet++ with a marker-controlled watershed segmentation strategy to facilitate aquaculture boundary extraction from fully polarimetric GaoFen-3 SAR imagery. First, four polarimetric decomposition algorithms were applied to extract 13 polarimetric scattering features. Together with the nine other polarisation and texture features, a total of 22 polarimetric features were then extracted, among which four were optimised according to the separability index. Subsequently, to reduce the “adhesion” phenomenon and separate adjacent and even adhering ponds into individual aquaculture units, two UNet++ subnetworks were utilised to construct the marker and foreground functions, the results of which were then used in the marker-controlled watershed algorithm to obtain refined aquaculture results. A multiclass segmentation strategy that divides the intermediate markers into three categories (aquaculture, background and dikes) was applied to the marker function. In addition, a boundary patch refinement postprocessing strategy was applied to the two subnetworks to extract and repair the complex/error-prone boundaries of the aquaculture ponds, followed by a morphological operation that was conducted for label augmentation. An experimental investigation performed to extract individual aquacultures in the Yancheng Coastal Wetlands indicated that the crucial features for aquacultures are Shannon entropy (SE), the intensity component of SE (SE_I) and the corresponding mean texture features (Mean_SE and Mean_SE_I). When the optimal features were introduced, our proposed method performed better than standard UNet++ in aquaculture extraction, achieving improvements of 1.8%, 3.2%, 21.7% and 12.1% in F1, IoU, MR and insF1, respectively. The experimental results indicate that the proposed method can handle the adhesion of both adjacent objects and unclear boundaries effectively and capture clear and refined aquaculture boundaries.

Habitat suitability and potential biological corridors for waterbirds in Yancheng coastal wetland of China

Yancheng coastal wetland, as an important part of the East Asian–Australasian Flyway, provided habitat for more than 200 migratory waterbirds by rest and over-winter. After it was listed as a “World Heritage List” in 2019, the protection of waterfowl habitat in Yancheng coastal wetland has attracted extensive attention from the international community. As an indicator species of Yancheng coastal wetland ecosystem health, waterbirds have practical significance for the protection of Yancheng coastal wetlands. Due to the long-term impact of human activities, the waterbird habitats are facing the threat of habitat fragmentation and lose, posing a serious challenge to its survival and diversity. Based on the survey data obtained Gruiformes, Charadriiformes, and Anseriformes waterbirds during the whole years from 2017 to 2021, this paper used the Maxent software for modeling species niches and distributions, a comprehensive evaluation method based on fuzzy mathematics, and Linkage Mapper model to assess the habitat suitability distribution of waterbirds, identify protection gaps and potential biological corridors for waterbirds in Yancheng coastal wetland. The results showed that habitat suitability and anthropogenic disturbance were the decisive factors affecting habitat selection of waterbirds. The suitable habitats for Gruiformes, Charadriiformes, and Anseriformes waterbirds were 23868, 22670, and 24870 ha, respectively. The suitable habitat area of waterbirds was 121,930 ha, concentrated on the study area's central and southern coast. Sheyang estuary was identified as a vital conservation gap in the study area. Meanwhile, biological corridors of a total of 33 waterbirds were identified in the study area. The longest biological corridor was 18.78 km, and the shortest was 0.09 km. Our research can provide scientific support for Yancheng coastal wetland protection and the improvement of waterbird diversity, together with the achievements of an ecological and sustainable situation between environmental conservation and economic development.

Seasonal change of habitat selection of Hydropotes inermis in Yancheng coastal wetlands, China

Yancheng coastal wetlands are one of the main habitats and breeding grounds of wild Chinese water deer (Hydropotes inermis). Based on GPS-GSM tracking data, we used the habitat selection index and MaxEnt model to simulate and analyze the distribution of suitable habitat of H. inermis in different seasons as well as the main influencing factors. The results showed that H. inermis mainly used reed marshes, with the usage rate in spring-summer and autumn-winter being 52.7% and 62.8%, respectively. The area under receiver operating characteristic curve value simulated by MaxEnt model in different seasons was 0.873 and 0.944, which showed high prediction accu-racy. In spring and summer, the sub-suitable and most suitable habitats were mainly reed marshes, farmland, and ponds. In autumn and winter, the main habitat types were reed marshes and ponds, with an area equivalent to only 5.7% and 8.5% of that in spring and summer. Distance to reeds, distance to Spartina alterniflora, habitat types, distance to water and distance residential area were the main environmental variables affecting the distribution of H. inermis in spring and summer. The above five variables and vegetation height were the main environmental variables affecting the distribution of H. inermis in autumn and winter. This study would provide an important reference for the conservation of Chinese water deer and the fine management of their habitats in Yancheng coastal wetlands.

Study on spatio-temporal variation and hydrological connectivity of tidal creek evolution in Yancheng coastal wetlands.

The ecological changes have attracted extensive international attention at Jiangsu Yancheng coastal wetland on the west coast of the Pacific Ocean in recent decades. Tidal creek is an important channel for material exchange between sea and land and plays an important role in the connectivity of water in coastal wetlands. The tidal flats from Sheyang Port to Liangduo Estuary in Jiangsu Province were selected and divided into five sub-study areas using each port as a split point. Based on the remote sensing image data from 1987 to 2020, this study used seven parameters (grade, number, length, density, curvature, bifurcation ratio, and drainage efficiency) to analyze the spatio-temporal divergence patterns and hydrological connectivity of tidal creek network. The results showed that (1) the area of tidal flat was reduced from 1024.87 to 352.05 km2, the total length of the tidal creek was directly reduced from 1061.27 to 640.74km, the average density increased from 1.00 to 1.82km/km2, and the total number increased by 33% in 1987-2020, indicating the tidal creeks tended to be "short, fragmented, and parallelized." (2) The development degree of tidal creek networks showed a trend of gradually increasing from north to south, in which the γ index in areas II and V were closer to 1/3 of tree shape after 2002, indicating that the development of tidal creeks in these two areas was better. (3) The spatial heterogeneity of hydrological connectivity levels of tidal creeks in the study area was obvious, which gradually increased from north to south. In 2020, Area I was the lowest, and ICmin was 0.14, and Area V was the highest, and ICmax was 0.90. (4) Reclamation was the main factor leading to the shrinkage and degradation of tidal creeks, but it also increased tidal creek density and hydrological connectivity per unit area; the expansion of Spartina alterniflora had a certain influence on the development of tidal creeks. The results of this study are expected to provide data support for understanding and predicting the evolution of the morphological characteristics of tidal creeks under the influence of human and natural activities and provide scientific reference for the protection and restoration of hydrological connectivity in coastal wetlands.

Comparing carbon and nutrient allocations among the different organs of plants Suaeda salsa between two typically coastal wetlands, China

The allocations of nutrients and biomass are important in understanding the growth processes of plants affected by different environmental conditions. In this study, two coastal wetlands were chosen to study the same species how to adapt to soil environments if plant biomass C allocation existed. The results showed that plants Suaeda salsa from the different coastal wetlands had similar carbon allocation patterns that C contents of plants Suaeda salsa’ leaves were lower than their stems and roots, while N contents were contrary. By analysis, C, N, P contents of plants Suaeda salsa’s leaves, stems and roots in the Yellow River Delta coastal wetlands were almost higher than in the Yancheng coastal wetlands. For soil total N, no differences existed between the two coastal wetlands while soil total P was higher in the Yancheng coastal wetlands than in the Yellow River Delta wetlands. When N:P of soil was lower than 2, the N:P variations of plants Suaeda salsa were described by line correlation significantly, and this phenomenon also existed in their corresponding soil nutrients. Plants Suaeda salsa, the growth of which at different sites was limited by soil nutrition, would allocate their biomass C to their stems and roots more than leaves to adapt to coastal environments such as strong wind and inundation of tide.

Effects of Spartina alterniflora Invasion on Soil Carbon, Nitrogen and Phosphorus in Yancheng Coastal Wetlands

The rapid invasion of Spartina alterniflora threatens the ability of soils to store carbon (C), nitrogen (N) and phosphorus (P) in coastal wetlands. This study analyzed the temporal and spatial distribution characteristics of soil C, N and P in Spartina alterniflora wetland in the Dafeng Elk Nature Reserve of Yancheng, China, in different invasion stages from 1995 to 2020. The results suggest that: (1) the invasion of Spartina alterniflora increased the content and storage of soil C and N, and decreased the content and storage of soil P; (2) altered soil properties caused by Spartina alterniflora invasion also indirectly affected the accumulation of soil C, N and P in wetland ecosystem. Organic carbon (SOC), total nitrogen (TN) and total phosphorus (TP) were positively correlated with soil moisture content (SMC) and electrical conductivity (SEC), and negatively correlated with bulk density (SBD) and pH; (3) Spartina alterniflora invasion increased soil C/P and N/P, and decreased soil C/N. In conclusion, Spartina alterniflora invasion has changed the ecosystem, increased the storage capacity of soil C and N in the invasive ecosystem, but reduced the storage capacity of soil P to a certain extent.

Prediction of the landscape pattern of the Yancheng Coastal Wetland, China, based on XGBoost and the MCE-CA-Markov model

Coastal wetland is a crucial part of the blue carbon ecosystem, having unique structural characteristics and serving both land and water functions. These areas also offer strong carbon sequestration and storage capacity. However, human activities and climate change have led to an ongoing decline in wetland areas. As an important wetland reserve in China, the coastal wetlands of Yancheng, Jiangsu Province, bring together a great number of water resources, land resources, biological resources, landscape resources, mineral resources, energy resources, and many other resources. However, in recent years, the coastal wetlands of Yancheng have also faced a continuous reduction in area. In this study, an integrated model of the Extreme Gradient Boosting (XGBoost) algorithm and multi-criteria evaluation-cellular automata-Markov (MCE-CA-Markov) model was designed to determine the importance of the driving factors of landscape pattern change and predict the landscape pattern of coastal wetlands in 2025, based on the analysis of landscape pattern changes in 2005, 2010, 2015, and 2020 in Yancheng coastal wetlands, Jiangsu Province. The results showed that the landscape configuration of coastal wetlands in Yancheng changed significantly during 2005–2020. The total natural wetland landscape area declined steadily over that 15-year span, showing a total decrease of 2.971×104 ha; on the contrary, the artificial wetlands increased. The analysis of the driving factors of wetland damage showed that gross domestic product (GDP), distance to roads, and average precipitation were the key factors. Based on this model, the natural wetland landscape of Yancheng’s coastal wetlands is predicted to decline sharply in 2025, and the wetland salt marsh vegetation will be extensively converted to aquaculture and agricultural land. Constructed land is predicted to increase significantly, and the trend of urban expansion is obvious. The study concludes with practical suggestions for the sustainable development and ecological conservation of the Yancheng coastal wetland ecosystem based on the predicted scenario.

Spatial distribution and sources of heavy metals in the sediment and soils of the Yancheng coastal ecosystem and associated ecological risks.

Studies of heavy metal pollution are essential for the protection of coastal environments. In this study, positive matrix factorization (PMF) and a GeoDetector model were used to evaluate the sources of heavy metal contamination and associated ecological risks along the Yancheng Coastal Wetland. The distribution of heavy metals was shown to be greatly affected by clay content, except for Cr in shoal. Components from 6.5 to 9φ have the strongest ability to absorb heavy metals, where the effects of Cd and Zn sequestration in the wetlands were most apparent. The abilities of various wetland environments to sequester heavy metals were shown to be Spartina alterniflora wetland > woodland > Phragmites australis wetland > aquaculture pond > shoal > paddy > meadow > dry land. The sources of the heavy metals included parent soil material (59%), agriculture (15%), and industrial pollutants (26%). According to the single-factor pollution index, there was no evidence of pollution except Cr and Pb. In general, the heavy metal pollution was insignificant. The order of pollution loading index was shoal > paddy field > dry land > Spartina Alterniflora wetland > aquaculture ponds > woodland > meadow > Phragmites australis wetland. The ecological harm of heavy metal exposure was slight except for Cd and Hg, where vehicle emissions appeared to be the main cause of heavy metal pollution.

Study on the rare waterbird habitat networks of a new UNESCO World Natural Heritage site based on scenario simulation

As a newly established World Natural Heritage site, the conservation of rare waterbird habitats in the Yancheng coastal wetlands has attracted wide international attention. In view of the importance of this area in international biodiversity conservation and waterbird habitat conservation, the study of the current situation of rare waterbird habitat networks with spatial isolation features of great demonstration significance to improve the habitat conservation quality of the heritage site. Based on the data obtained from habitat suitability assessments of rare waterbirds, this paper used complex network theory, ecological stepping-stone theory and circuit models to analyze the current status and robustness of rare waterbird habitat networks in the Yancheng coastal wetlands. The results showed that the stepping stones of the red-crowned cranes and the Oriental storks were mainly distributed around important habitat areas, including aquaculture ponds and reed marshes, with areas of 1275.68 hm2 and 1247.74 hm2, respectively, while the stepping stones of Saunders's gulls were mainly distributed within the Tiaozini habitat site, with an area of 1180.76 hm2. The stability and connectivity of the habitat networks of red-crowned cranes and Oriental storks in the northern habitat area were better. At the Tiaozini habitat site, there was spatial isolation and low connectivity among the habitats and stepping stones of Saunders's gulls. In the optimal protection scenario, the stability and connectivity of the habitat network structure of red-crowned cranes and Oriental storks were the best, and the networks tended to exhibit assortativity. In the random destruction scenario, the connectivity of the habitat networks of Saunders's gulls was the lowest, and the network structure was the most fragile. Finally, the optimization and restoration patterns of habitat network based on improving the support capacity of important habitat nodes and the enhancement of the stability and connectivity of the stepping-stone networks were proposed.

Satellite-Based Monitoring of Coastal Wetlands in Yancheng, Jiangsu Province, China

The dynamic process of the wetland can reflect its impact on the environment, and finding a balance point supporting harmonious coexistence between man and nature has become an issue of increasing concern. On the basis of previous studies that have focused on local coastal wetlands, the temporal and spatial changes and driving forces of wetlands in the Yancheng coastal area from 1991 to 2021 were analyzed over a larger area. According to the study findings: (1) The results of the study of the Yancheng coastal wetland with a larger scope differed significantly from findings resulting from a study of coastal wetland only. This difference was mainly reflected in the relatively stable situation of wetland ecology as a whole, while the changes in local surface features were more significant. (2) Natural wetlands were transformed into artificial wetlands and non-wetland types, and artificial wetlands were transformed into non-wetland types; additionally, reverse transformations and internal transformations of surface features also took place. For instance, the saltpan was transformed into mudflats (86.26 km2), and some mudflats into herbaceous vegetation (193.47 km2). (3) When analyzing the impact intensity of human activities on the Yancheng wetland, it was found that this factor has experienced a process of first rising and then falling. The index was 0.650, 0.653, 0.664, 0.661, and 0.641 in 1991, 2000, 2008, 2016, and 2021, respectively. (4) Lastly, an analysis of factors driving wetland change revealed that human factors were the most critical reasons for wetland landscape change. Our work can play a reference and inspiration role in the monitoring and protection of similar coastal wetlands.