Urban Wetland Ecosystem Research Articles

Urban wetland fragmentation and ecosystem service assessment using integrated machine learning algorithm and spatial landscape analysis

Dynamics of ecosystem service value (ESV) of various wetlands has been assessed by researchers globally. But the impact of spatio-temporal variation of landscape metrics on ESV in the lower Gangetic plains has not been examined, fully. The present work has established linkages between landscape metrics and ESV in Kolkata urban agglomeration using support vector machine and multivariate regression analysis. Result indicates that wetland area has been reduced by 5.26%, 13.67% and 9.03% during the periods 1990–2000, 2000–2010 and 2010–2020, respectively and the ESV contributed by wetlands has been decreased by $131428, $323674 and $184649, respectively during the same period at an annual rate of 0.85%. Number of patches, mean patch area and edge density are the main determinants of wetland fragmentation and decreased by 44.12%, 10.23% and 8.65%, respectively during the last three decades. A wetland restoration strategy based on dynamic restoration, reactive restoration and wetland creation for the study area has been formulated, which can guide for sustainable management of wetland resources in Kolkata urban agglomeration.

Temporal and Spatial Characteristics of CO2 Flux in Plateau Urban Wetlands and Their Influencing Factors Based on Eddy Covariance Technique

Urban wetlands, an important part of the urban ecosystem, play an important role in regional carbon cycles and the carbon balance. To analyze the CO2 source and sink effects of plateau urban wetlands, based on the data measured by an eddy covariance instrument, the temporal and spatial characteristics of CO2 flux and their influencing factors in the urban wetland of Xining City in the Qinghai Province of China during a warm season (July to September 2020) were studied. The results show that: (1) On the daily scale, the CO2 flux exhibited an obvious “U”-type variation, characterized by strong uptake in the daytime and weak emission at night, with an average daily flux of −0.05 mg·m−2·s−1. The CO2 uptake peak of the wetland took place at 13:00 (−0.62 mg·m−2·s−1), and the emission peak occurred at 23:30 (0.34 mg·m−2·s−1); (2) on the monthly scale, the CO2 flux of the wetland in the study period showed a net uptake each month. The flux increased month by month, and the maximum value occurred in September (−142.82 g·m−2·month−1); (3) from a spatial point of view, the river area showed a weak CO2 uptake (−0.07 ± 0.03 mg·m−2·s−1), while the artificial wetland area showed a strong CO2 uptake (−0.14 ± 0.03 mg·m−2·s−1). The former was significantly lower than the latter (p < 0.01); (4) the regression analysis results show that the CO2 flux was significantly correlated with PAR, VPD, Tsoil, and SWC (p < 0.01). The relationships between the flux and PAR, Tsoil, and SWC were rectangular hyperbola (y = 0.2304 − 2 × 10−3x/(0.9037 + 0.0022x), R2 = 0.64), exponential (y = 0.046exp(0.091x), R2 = 0.88), and quadratic (y = −0.0041x2 + 0.1784x − 1.6946, R2 = 0.83), respectively. Under the joint action of various environmental factors, the urban wetland ecosystem in plateau displayed a strong carbon sink function in warm seasons. This study can establish a data scaffold for the accurate estimation of carbon budget of this type of ecosystem.

Land system transformations govern the trophic status of an urban wetland ecosystem: Perspectives from remote sensing and water quality analysis

AbstractGlobally, urban wetlands are facing immense pressure from land use land cover changes (LULCCs) and associated water quality degradation that is severely affecting the trophic status of these ecosystems. This study analyzed water quality degradation resulting from land system changes in the vicinity of Khushalsar, an urban Wetland, in Srinagar City from 1980 to 2017. The analysis of satellite data indicated that this Wetland lost ~18.1 ha from 1980 to 2017. During the same period, the urban area within the Wetland increased from 0.2% to 16.5%. The land cover changes assessed in the vicinity of Wetland indicated an increase of 119% and 62.8% in built‐up and roads respectively. The analysis of surface water quality of the Wetland showed widespread degradation. The Trophic state index ranged from 73.4 to 84.6 indicating hyper‐eutrophic waters. A snapshot of comparative water quality data from 2002 to 2018 revealed that the mean concentration of NO3−‐N increased from 219 to 433 μg L−1 and that of total phosphorus increased from 135.4 to 1,236 μg L−1 indicative of continuous nutrient enrichment. Hierarchical cluster analysis (HCA) grouped eight sampling sites into four clusters based on likeliness of water quality characteristics. Similarly, discriminant analysis showed the formation of similar patterns of clusters, corroborating the HCA. Principal component analysis suggested three principal components accounting for a cumulative variance of 90.61%. The unplanned land system changes vis‐a‐vis human‐induced water quality degradation together with the lack of a monitoring mechanism have brought the Khushalsar Wetland to its current hyper‐eutrophic state.

Estimation of Soil Carbon Stocks of Urban Freshwater Wetlands in the Colombo Ramsar Wetland City and their Potential Role in Climate Change Mitigation

Wetlands hold significant potential for climate change mitigation due to their high capacity to sequester atmospheric carbon dioxide (CO2). Colombo, Sri Lanka was recently declared as one of the eighteen global Ramsar wetland cities. The current study represents the first attempt to quantify soil organic carbon (SOC) stocks held by the urban freshwater wetlands in Colombo. The study focused on the extensive urban wetland ecosystems of Kolonnawa wetland and Thalawathugoda wetland park. SOC stocks were determined using three parameters: depth of soil, bulk density, and SOC concentration. Loss on ignition method was used in quantifying SOC concentrations. Average SOC stocks, up to a depth of 60 cm at Kolonnawa wetland and Thalawathugoda wetland park were estimated at 504 ± 14 t C/ha and 550 ± 23 t C/ha, respectively. Furthermore, the total SOC stock at Kolonnawa wetland and Thalawathugoda wetland park were estimated at 198,408 ± 5564 t CO2eq and 66,313 ± 2764 t CO2eq, respectively. When considering global estimates, it was found that freshwater wetlands in Colombo hold a higher SOC stock than tropical wet forests and tropical dry forests. The current study highlights the importance of urban ecosystems in mitigating the ever increasing concentrations of atmospheric CO2 .

Impacts of Urbanization on the Muthurajawela Marsh and Negombo Lagoon, Sri Lanka: Implications for Landscape Planning towards a Sustainable Urban Wetland Ecosystem

Urban wetland ecosystems (UWEs) play important social and ecological roles but are often adversely affected by urban landscape transformations. Spatio-temporal analyses to gain insights into the trajectories of landscape changes in these ecosystems are needed for better landscape planning towards sustainable UWEs. In this study, we examined the impacts of urbanization on the Muthurajawela Marsh and Negombo Lagoon (MMNL), an important UWE in Sri Lanka that provides valuable ecosystem services. We used remote sensing data to detect changes in the land use/cover (LUC) of the MMNL over a two-decade period (1997–2017) and spatial metrics to characterize changes in landscape composition and configuration. The results revealed that the spatial and socio-economic elements of rapid urbanization of the MMNL had been the main driver of transformation of its natural environment over the past 20 years. This is indicated by a substantial expansion of settlements (+68%) and a considerable decrease of marshland and mangrove cover (−41% and −21%, respectively). A statistical analysis revealed a significant relationship between the change in population density and the loss of wetland due to settlement expansion at the Grama Niladhari division level (n = 99) (where wetland includes marshland, mangrove, and water) (1997–2007: R2 = 0.435, p = 0.000; 2007–2017: R2 = 0.343, p = 0.000). The findings also revealed that most of the observed LUC changes occurred in areas close to roads and growth nodes (viz. Negombo, Ja-Ela, Wattala, and Katana), which resulted in both landscape fragmentation and infill urban expansion. We conclude that, in order to ensure the sustainability of the MMNL, there is an urgent need for forward-looking landscape and urban planning to promote environmentally conscious urban development in the area which is a highly valuable UWE.

Monitoring of water quality variation trends in a tropical urban wetland system located within a Ramsar wetland city: A GIS and phytoplankton based assessment

The present study, was conducted in an urban wetland system within a Ramsar wetland city in Sri Lanka to study the effectiveness of using the Geostatitical and multivariate statistical techniques together with phytoplankton based biological indices to assess the wetland ecological status. Seven sites were selected from the wetland and the water quality parameters and the diversity and abundance of phytoplankton at each site was assessed. Thirteen species of phytoplankton from Class Cyanophyceae, 18 species from Class Chlorophyceae and six species from class Bacillorphyceae were recorded during the study. There were significant spatial variation of water quality parameters and phytoplankton composition among the study sites. Principal component analysis for water quality and phytoplankton distribution was performed. Palmers index, percentage biological index and the limnological condition index was calculated based on water quality and phytoplankton data. According to the classification based on Palmers index the sites located in the northern portion of the wetland indicated high organic pollution, while other sites indicated no or less less organic pollution. According to the limnological categorization based on pollution index, %BI and LICOI, the northern sites were categorized as sites with poor ecological quality and as severely contaminated sites. The sites in the southern portion of the wetland were categorized as moderately polluted sites with acceptable limnological conditions for the ecological functions to occur within tolerable limits. Water quality prediction maps for the wetland was developed using geostatistical methods and the water quality trends also agreed with the results of the biological indices and the results of the multivariate statistics. The results indicated that the geostatisical and multivariate techniques together with the Palmers index, percentage biological index and the limnological condition index can serve as important tools for monitoring the water quality trends in tropical urban wetland ecosystems.

An optimization model of sewage discharge in an urban wetland based on the multi-objective wolf pack algorithm.

The Longfeng Wetland of Daqing City in China was taken as the research object to determine a reasonable sewage reduction scheme and resolve the pollution of urban wetland ecosystems. First, the main pollutants, including dichromate oxidizability (CODCr), ammonia nitrogen (NH3-N), total phosphorus (TP), and petroleum, were selected as indices. A two-dimensional hydrodynamic and water quality coupling model was established using MIKE 21. An optimal regulation method to improve the water quality of the wetland was then proposed following the numerical simulation method, and a multi-objective optimization model is established. The model establishes two objective functions based on wetland pollutant and water quality requirements. The model's constraints include hydrodynamic conditions and water quality conditions, and it considers the control point of the sewage concentration, sewage outfall processing capacity, depth of treatment, and changes in the water cycle. The wolf pack algorithm is introduced to resolve the multi-objective problem of sewage outfall optimization, and an optimal sewage scheme is obtained. According to the results of the scheme, some measures are proposed to manage the pollutants in urban wetland waters.

Cost-effectiveness analysis of different types of payments for ecosystem services: A case in the urban wetland ecosystem

Payments for Ecosystem Services (PES) have emerged as a popular conservation tool, yet evaluation among different PES programs strategies remains piecemeal. We prospectively compare cost-effectiveness of general PES, collective payments for ecosystem services (CPES) and the transition from PES to Land Purchases or Easements (LPE). We analyze the economic cost using statistics data and literature data, and analyze the transaction cost with the ordinal variable. We develop the Emergy Analysis method with the InVEST Habitat Quality model, and utilize it to analyze and map the ecological effectiveness. This paper gives an example to assessing the cost-effectiveness of different PES programs. Based on the analysis, LPE strategy led to improved ecological effectiveness, lower cost and greater cost-effectiveness. The collective PES has lower cost than general PES. However, they demonstrate equal ecological effectiveness. Based on these outcomes, we analyze the factors that influence PES programs’ cost-effectiveness, including collective or group, market-based mechanism, economic incentive, transaction cost, contract scale etc. We conclude that minimal number of intermediaries, community/collective support and involvement constitute the key factors in improving the cost-effectiveness of ecological programs. However, we acknowledge the need for further studies on the subject.

Climate Change Impacts on Water Resources of AryCreek, Inverloch, Victoria

Understanding urban wetland ecosystem services structure allows managers to base restoration efforts on multiple user end-benefits. Ary Creek can provide the coupled function of improving water qua ...

Setting conservation priorities in cities: approaches, targets and planning units adapted to wetland biodiversity and ecosystem services

Protecting wetlands in cities is challenging. A cost-effective spatial prioritization approach taking into account stakeholder motivations is needed to identify wetlands of conservation interest. This study aims to optimize the efficiency of a systematic conservation planning (SCP) approach to protect nine urban wetland ecosystem services (ES) and biodiversity. First, we mapped ES supply and demand to capture their spatial variation as they occur at the wetland scale. Secondly, using wetland property value as cost data, we compared the efficiency of SCP to two multicriteria scoring approaches. Thirdly, we compared SCP alternatives by changing the planning unit scale and conservation objectives (i.e. emphasizing ES demand and focusing on the most important ES). The total cost of the scoring approach networks was minimally 13 times higher, when compared to the SCP approaches. Consequently, the scoring approaches were at least five times less efficient than SCP per unit of network area ($/m2). Decreasing the size of planning units resulted in further cost reduction, with networks that were up to 92% less costly. We also highlighted that beneficiary demand fulfillment in networks could be optimized without a loss in efficiency. Finally, SCP secured nine ES for the same expenditure as that required to protect four public safety related ES. However, planning solely for these four important ES failed to represent those of other ES. Our results may provide a tool to better inform land use decision planning in order to mitigate the impacts of urban growth on ES.

The service function value assessment analysis of urban wetland ecosystem--A case study of Xi’an Chan-Ba wetland

To analyze the service function value of urban wetland ecosystems, a functional value assessment system was done for Xi’an Chan-Ba wetland. Using market value method, carbon tax law and afforestation cost method, alternative cost method, travelling cost method and so on, those values were converted into economic value and a summary of the same was made for comparison. The total service function value of Chan-Ba wetland ecosystem is 3.87 × 108 ￥. Of this, the value of wetland leisure tourism is the highest (accounting for 55.76%), followed by the value of carbon fixation and oxygen release from the wetland (accounting for 25.56%), other functional values accounting for smaller proportions. The value of ecosystem functions in Xi’an Chan-Ba wetland plays an important role in development of the urban economy. In that context, it should be reasonable to develop and protect the urban wetland ecosystem, and promote the virtuous circle of the urban wetland ecosystem.

Analysis on Ecological Protection of Urban Wetland

ABSTRACT Urban wetland is an important ecological infrastructure of the city, which is an important natural system that depends on the sustainable development of the city. It has many ecological and social service functions. Urban wetland ecosystems are currently facing serious pollution, wetland area is reduced, biodiversity is seriously damaged, biological invasion led to the disappearance of the original species and other issues, for these issues proposed to create wetland parks, the establishment of nature reserves, the use of bioremediation of wetlands, Effective wetland information and evaluation system, strengthen legislation enforcement, regulate eco-tourism, strengthen international cooperation, change the mode of operation and other effective measures to restore and protect.

The rise of glyphosate and new opportunities for biosentinel early-warning studies.

Glyphosate has become the most commonly used herbicide worldwide and is reputedly environmentally benign, nontoxic, and safe for use near wildlife and humans. However, studies indicate its toxicity is underestimated and its persistence in the environment is greater than once thought. Its actions as a neurotoxin and endocrine disruptor indicate its potential to act in similar ways to persistent organic pollutants such as the organochlorines dichlorodiphenyltrichloroethane (DDT) and dioxin. Exposure to glyphosate and glyphosate-based herbicides for both wildlife and people is likely to be chronic and at sublethal levels, with multiple and ongoing exposure events occurring in urban and agricultural landscapes. Despite this, there has been little research on the impact of glyphosate on wildlife populations, and existing studies appear in the agricultural, toxicology, and water-chemistry literature that may have limited visibility among wildlife biologists. These studies clearly demonstrate a link between chronic exposure and neurotoxicity, endocrine disruption, cell damage, and immune suppression. There is a strong case for the recognition of glyphosate as an emerging organic contaminant and substantial potential exists for collaborative research among ecologists, toxicologists, and chemists to quantify the impact of glyphosate on wildlife and to evaluate the role of biosentinel species in a preemptive move to mitigate downstream impacts on people. There is scope to develop a decision framework to aid the choice of species to biomonitor and analysis methods based on the target contaminant, spatial and temporal extent of contamination, and perceived risk. Birds in particular offer considerable potential in this role because they span agricultural and urban environments, coastal, inland, and wetland ecosystems where glyphosate residues are known to be present.

Use of Protozoa for Assessing Water Quality in A Humid Subtropical Urban Wetland Ecosystem, Southern China

Multivariate bioassessment based on community data has many advantages to assess environmental quality status in aquatic ecosystems. However, there are few reports on their use for bioassessment in subtropical wetland systems. In this study, the protozoan microfauna and their use in evaluating water quality status was investigated in a humid subtropical urban (XiXi) wetland system in southern China, during the period of June 2013-May 2014. Samples were collected every month at six sampling stations within different pollution/eutrophication levels. A total of 85 protozoan species were recorded, including 67 ciliates, 10 flagellates, 8 sarcodines. A clear variation on spatial scale in protozoan community structures were represented at the six stations. Multivariate approaches revealed that the variations in the community structure were significantly related to the changes of environmental variables, especially nutrients ammonia-N (NH4-N), nitrate-N (NO3-N) and total phosphorus (TP), alone or in combination with water temperature (T) and dissolved oxygen (DO) and Four dominant species (Euglena acus, Cucurbitella mespiliformis, Codonella acutula and Hemiophrys punctata) were significantly correlated with nutrients. Otherwise, the species richness, diversity and evenness indices represented significant correlations with the nutrients. The results demonstrate that the community-based bioassessment using protozoa may be used as a feasible protocol for determining the water quality status and human disturbance in a humid subtropical urban wetland system.

Health Assessment of Urban Wetland Ecosystems: A Case Study

Health Assessment of Urban Wetland Ecosystems: A Case Study

English

The presence of 1,1,1-trichloro-2,2-bis(p-chlorophenyl)ethane (DDT) and derivatives in the Clarius werneri of Uganda’s major urban wetland ecosystems was investigated. Solid dispersion extraction method for extraction, florisil column method for clean-up, gas chromatograph equipped with an electron capture detector (GC-ECD) for analysis and gas chromatograph equipped with mass spectrophotometer (GC-MS) for confirmation of results were used in this study. The major DDT contaminants detected in the samples were p,p’-DDD, p,p’-DDE and p,p’-DDT which were found in 25, 22 and 21% of the samples, respectively. o,p’-DDD was detected in 19% and o,p’-DDT in 13% of the samples. For o,p’-DDE there were no measurable values since the levels were below limit of quantitation (LOQ). The concentrations of DDT derivatives ranged between ND-0.478 µg/kg for p,p’-DDE, ND-0.387 µg/kg for o,p’-DDD, ND-0.476 µg/kg for p,p’-DDD, ND-0.345 µg/kg o,p’-DDT and ND-0.556 µg/kg for p,p’-DDT. The concentration of total DDT in C. werneri was in the range of 1.111 to 1.328 µg/kg dry wt. Generally, all the samples had DDT derivative levels below the maximum residue limit recommended by Food and Agriculture Organisation/World Health Organization (FAO/WHO) Codex Alimentarius Commission.   Key words: 1,1,1-trichloro-2,2-bis(p-chlorophenyl)ethane (DDT), DDT derivatives, Clarius werneri, Uganda, wetlands.

Influence of Microorganisms on Nitrogen Cycle of Urban Wetland in Northeast China

Wetland is the important part in urban ecosystem. Microorganisms is integral component of urban wetland ecosystem is the main factor of wetlands sewage treatment, and plays an irreplaceable role in the degradation. In this paper, the authors regard urban wetland of Harbin in north shore of Songhua river as the research object, through experiments to identify the microorganisms types, finding five microorganisms types being nitrify fungi. The article analyzes the contributions of microorganisms in nitrogen cycle of urban wetland. It is present that microorganisms plays an irreplaceable role in controlling pollutions and nitrification and anti-nitrification reactions play the most significant role in the degradation of nitrogen compounds and ammonium oxidation is a possible process in deducing nitrogen pollutions.

Contributions of Microorganisms to Nitrogen Cycle of Wuyiling Wetland in Yichun in Northeast China

Wetland is the important part in urban ecosystem. Microorganisms is integral component of urban wetland ecosystem is the main factor of wetlands sewage treatment, and plays an irreplaceable role in the degradation. In this paper, the authors regard urban wetland of Yichun in north shore of Tangwang river as the research object, through experiments to identify the microorganisms types, finding five microorganisms types being nitrify fungi. The article analyzes the contributions of microorganisms in nitrogen cycle of urban wetland. It is present that microorganisms plays an irreplaceable role in controlling pollutions and nitrification and anti-nitrification reactions play the most significant role in the degradation of nitrogen compounds and ammonium oxidation is a possible process in deducing nitrogen pollutions.

Changes of urban wetlands in Wuhan, China, from 1987 to 2005

Urban wetlands play a significant role in the sustainable development of the urban eco-environment. However, accelerated urbanization has caused rapid changes in urban wetland landscape patterns, which may seriously affect their functions. Based on land-use maps, TM images, and field data from the Wuhan wetlands, the spatiotemporal evolution and wetland landscape pattern were quantitatively analyzed, with reference to landscape ecology indices of diversity, fragmentation, dominance, shape, and dimension. The results showed that: (1) the natural wetland area decreased: lake wetlands and marsh wetlands decreased by 18.71% and 50.3% from 1987 to 2005, respectively; (2) artificial wetland area increased by 47.75% in Wuhan over the same period; (3) the lake wetland area of Wuhan declined due to the conversion of large lakes to smaller ones; (4) the value of the diversity index (H), evenness index (E), and fragmentation index (F) decreased, while the value of the dominance index (D) increased from 1987 to 2005; (5) the landscape shape index (LSI) and fractal dimension (FD) of the river wetlands, lake wetlands, bottomland wetlands, and marsh wetlands decreased, while the LSI and FD of the reservoir and pond wetlands increased from 1987 to 2005; and (6) natural, societal, and economic, as well as human, activities are major factors for the structural changes in the Wuhan wetland landscape, as revealed by canonical correlation analysis. Results suggest that the ecological environment of urban wetlands should be protected to maximize the services of urban wetland ecosystems in Wuhan, China.