Wetland Functions Research Articles

Effects of long-term nitrogen addition on dissolved organic matter characteristics in a temperate wetland of Northeast China

Dissolved organic matter (DOM) plays an indispensable role in ecosystem services and functions in wetlands. While most wetlands have undergone increased nitrogen (N) loading due to intensive human activities, the response of DOM characteristics to long-term N addition remains unexplored. In this study, we assessed the changes in dissolved organic carbon (DOC), NH4+, NO3-, dissolved organic N (DON), dissolved total N (DTN), and dissolved total phosphorus (DTP) in surface water and soil pore water at 15 cm depth after 10 years of N addition at four levels (0, 60, 120, and 240 kg N hm−2 year−1) in a freshwater marsh of Northeast China. We also examined the effect of N addition on DOM aromaticity and humification by measuring the specific UV absorbance at 254 nm (SUVA254), the color per C unit (C/C ratio), and the fulvic acid/humic acid ratio (E4/E6 ratio). Our results showed that N addition significantly altered DOM properties, but the direction and magnitude of these changes generally did not vary with the N addition level. During the growing season, DOC, NH4+, NO3-, DON, and DTN concentrations in both surface water and soil pore water were increased by N addition. Accordingly, N addition increased the DOC/DTP and DTN/DTP ratios but decreased the DOC/DTN ratio in surface water and soil pore water. In addition, the SUVA254 value and C/C ratio increased, while the E4/E6 ratio reduced after N addition in surface water and soil pore water, indicating increases in DOM aromaticity and humification. These observations suggest that long-term N addition changes DOM characteristics by causing stoichiometric imbalances and increasing recalcitrant compounds in temperate freshwater wetlands, which may then deteriorate water quality, alter microbial-mediated ecological processes, and impact downstream aquatic ecosystem structures.

Spatiotemporal dynamics in soil iron affected by wetland conversion on the Sanjiang Plain

AbstractSince the 1950s, nearly 80% of wetlands in the Sanjiang Plain have been converted into paddy fields. The conversion might affect the solubility and mobility of soil iron, influencing the export of iron into the Amur River and the primary production of the Okhotsk Sea. However, information regarding long‐term studies of the spatiotemporal dynamics of soil iron after cultivation is limited. In this study, six regions, including 18 plots in the Sanjiang Plain, were selected as sampling sites covering natural wetlands and paddy fields with planting ages of 2, 5, 11, 18, and 25 years after conversion from the wetland. Samples were collected at six different depths (0–10, 10–20, 20–40, 40–60, 60–90, and 90–120 cm) analyzed for water‐soluble ferrous iron (Fe[II]), water‐soluble iron (Few), complex iron (Fep), amorphous iron oxides (Feo), free iron oxides (Fed), and total iron (Fet) and six soil physicochemical characteristics. Two years after the conversion of wetlands to rice fields led to an immediate decrease in Fe(II), Few, Fep/Fed, and Feo/Fed, while the Fep and Feo contents decreased at 5 years. Both the concentrations and stocks of soil Fet increased gradually during the first 18 years. The findings in the Sanjiang Plain suggest that the function of wetlands after conversion as a source of iron might decrease with increasing time, with potential ecological effects on the neighboring marine environment. Recently initiated wetland restoration would protect the land ecosystems in the Sanjiang Plain and promote the future sustainability of the Amur Basin.

Ecological and Socio-Economic Value of Waterlogged Areas

The article summarizes the main indicators of the value of waterlogged areas, which must be taken into account for the sustainable management of wetlands. The ecosystem functions of wetlands included in the natural capital of a region relate to hydrology, water quality, supporting food chains, and providing habitats for living organisms, including rare and protected ones. The socio-economic significance of wetlands is formed both from their consumer value and from non-productive, socio-cultural values. There is a need to develop an approach and methodology for the study of waterlogged areas, within which the assessment of the natural capital of a region will necessarily include the assessment of the non-productive values of wetlands.

Evaluation of wetland ecosystem services in green core of Changzhutan urban agglomeration, Hunan

Wetland in Changzhutan green core area of Hunan Province provides a number of ecosystem services for local urban construction and economic development. The evaluation of wetland ecosystem services may provide the wetland value data for the construction of Changzhutan urban agglomeration, and provide the basis for the creation of ecological compensation for wetland ecological protection. In this study, 8 service functions: water conservation, pollution degradation, carbon fixation & oxygen release, soil fixation & fertilizer preservation, nutrient accumulation, microclimate improvement, habitat provision provision, and scientific research & culture recreation were selected to evaluate the ecological service functions of wetlands in the green core area. The results showed that: (1) The total value of wetland ecological services in the green core area was 748 million yuan/a, among which the water conservation function was the dominant service function, with the highest value (319 million yuan), followed by the carbon fixation & oxygen release function and the pollution degradation function (156 million yuan and 125 million yuan, respectively). (2) From the perspective of the three prefecture-level cities, the total annual ecological value of Changsha wetland (353,007,600 yuan/a) was the highest, followed by Xiangtan (268,140,900 yuan/a), and Zhuzhou (126,749,900 yuan/a) was the lowest. (3) From the perspective of each district and county, both the total value and individual value of wetland service functions are the highest in Yuetang District, followed by Yuhua District and Tianxin District, and the lowest in Xiangtan County. The research results may provide a reference for the construction of wetland ecosystem service evaluation index system, strengthen the protection and utilization of wetland resources, and provide data support for the improvement of ecological civilization in Changzhutan urban agglomeration.

Linking functional diversity, trait composition, invasion, and environmental drivers in boreal wetland plant assemblages

AbstractQuestionsA range of landscape and local environmental factors, including invasion, interact with species functional diversity and trait composition to shape biodiversity patterns and ecosystem function of wetlands. A trait‐based, mechanistic understanding of community assembly holds promise for wetland conservation, but this has been rarely examined across scales. We examined: (a) the relative influence of climate, landscape matrix, and local physicochemistry on invasion intensity and functional diversity in boreal wetland plant assemblages; and (b) the ecological traits linked to these environmental factors.LocationOne hundred fifty‐three wetlands across the Boreal Forest of Alberta, Canada.MethodsWe used data on invasion intensity, using two terrestrial invaders (Sonchus arvensis and Cirsium arvense), and environmental factors at local and landscape levels. We used eight traits from 366 vascular plants to assess functional diversity and invasion responses to environmental gradients (generalized linear models) and individual species trait–environment relationships (community‐weighted mean redundancy analysis, fourth‐corner analysis).ResultsLandscape matrix and the degree of invasion were the primary drivers of functional diversity, while invasion intensity was driven by physicochemistry and functional diversity. Community trait–environment patterns clearly separated wetlands by invasion status. Uninvaded wetlands were surrounded by lowland conifers and composed of stress‐tolerant associated traits, while invaded wetlands contained high levels of disturbance and traits associated with high resource availability and reproduction rates. This division was further supported by individual trait–environment relationships.ConclusionsLandscape matrix was the dominant driver of functional diversity and composition pattern, while the local physicochemistry and surrounding land‐cover matrix helped explain invasion. Our analysis revealed some of the mechanistic relationships shaping plant community assembly across boreal wetlands, information that can help resource managers identify, predict, and alleviate possible threats from landscape anthropogenic disturbances to wetland ecological integrity.

Assessing the Health of Inland Wetland Ecosystems Over Space and Time in China

Wetland is a unique natural landscape pattern, which provides a variety of important functions and services for human societies. With the rapid develop of the economy and accelerated urbanization, the inland wetlands are faced with series of problems, including reduced area, weakened wetland functions, and deterioration of the wetland ecosystem environment. Therefore, it is necessary to quantitatively assess the ecological health of China's inland wetlands, which is key to the sustainable development of ecosystems. However, most assessments of wetland ecosystems only examine single wetlands or watershed wetlands, and there are few assessments of wetland health at the national level. In this paper, based on land cover data, climate data, and social and economic data, an assessment system of inland wetland health is established by using the Pressure-State-Effect-Response (PSER) model, which includes 15 assessment indicators. Analytic hierarchy process (AHP) was used to define the indicator weights. Then we assessed the ecosystem health of the inland wetlands of China in 2010 and 2018, which produced three main results. (1) Unlike ecosystem health evaluated by administrative districts, wetland ecosystem health (WEH) evaluation based on the grid could provide additional details of wetland health. (2) The area of inland wetlands increased by 16328 km2 in 2018 compared to 2010, and the average wetland ecosystem health index in 2018 was 3.45, compared to an index value of 3.24 in 2010. (3) In 2018, wetlands in the better, good, moderate and poor conditions represented about 26.3%, 46.4%, 26.9% and 0.5% of the total, respectively. These results provide a practical guide for protecting and managing wetland system resources and reliable information for land use planning and development.

Restoration impacts on rates of denitrification and greenhouse gas fluxes from tropical coastal wetlands

Forested coastal wetlands are globally important systems sequestering carbon and intercepting nitrogen pollution from nutrient-rich river systems. Coastal wetlands that have suffered extensive disturbance are the target of comprehensive restoration efforts. Accurate assessment of restoration success requires detailed mechanistic understanding of wetland soil biogeochemical functioning across restoration chrono-sequences, which remains poorly understood for these sparsely investigated systems. This study investigated denitrification and greenhouse gas fluxes in mangrove and Melaleuca forest soils of Vietnam, using the 15N-Gas flux method. Denitrification-derived N2O was significantly higher from Melaleuca than mangrove forest soils, despite higher potential rates of total denitrification in the mangrove forest soils (8.1 ng N g-1 h-1) than the Melaleuca soils (6.8 ng N g-1 h-1). Potential N2O and CO2 emissions were significantly higher from the Melaleuca soils than from the mangrove soils. Disturbance and subsequent recovery had no significant effect on N biogeochemistry except with respect to the denitrification product ratio in the mangrove sites, which was highest from the youngest mangrove site. Potential CO2 and CH4 fluxes were significantly affected by restoration in the mangrove soils. The lowest potential CO2 emissions were observed in the mid-age plantation and potential CH4 fluxes decreased in the older forests. The mangrove system, therefore, may remove excess N and improve water quality with low greenhouse gas emissions, whereas in Melaleucas, increased N2O and CO2 emissions also occur. These emissions are likely balanced by higher carbon stocks observed in the Melaleuca soils. These mechanistic insights highlight the importance of ecosystem restoration for pollution attenuation and reduction of greenhouse gas emissions from coastal wetlands. Restoration efforts should continue to focus on increasing wetland area and function, which will benefit local communities with improved water quality and potential for income generation under future carbon trading.

Inundation characteristics of mangrove and saltmarsh in micro-tidal estuaries

Tidal inundation is a principal driver in intertidal wetland functioning. A combination of surface elevation and its relation to tidal range creates inundation regimes that influence a range of abiotic factors that affect wetland species distribution. Hydroperiod is a term frequently used to describe inundation regimes; however, the term has been vaguely defined in the past and typically quantified using tide gauge data rather than empirical field observations. This study explores relationships between various characteristics, such as frequency, total duration, average duration, average depth, non-tidal exposure, and mangrove/saltmarsh distribution in micro-tidal estuarine settings of southeast Australia. Inundation was measured directly using 35 pressure transducers embedded into mangrove and saltmarsh substrates over a period of two lunar tidal cycles along six transects located at Clyde and Minnamurra River estuaries, New South Wales, Australia. Results indicated differences in wetland inundation characteristics between mangrove and saltmarsh that are a function of wetland microtopography and site-specific tidal regime (e.g. local tidal range). For example, mangroves were inundated approximately 15–70% of the time, and 0.9–2 times a day, whereas saltmarshes were submerged only <15% of the time and less than 0.9 times per day. Comparison of direct field measurements and tide gauge-derived estimates of wetland inundation regime revealed that nearby gauge data may provide an acceptable estimate; however, distant tide gauge data provided poor estimates due to the effect of tidal dampening and amplification, respectively. Detailed analysis of wetland inundation characteristics as presented in this study demonstrates a method for describing inundation regimes at local scale. Improved understanding of contemporary tidal inundation dynamics in mangrove and saltmarsh can support modelling of wetland response to sea-level rise, as well as restoration practises by providing estimates of inundation tolerances.

Comparing Wetland Ecosystems Service Provision under Different Management Approaches: Two Cases Study of Tianfu Wetland and Nansha Wetland in China

The largest blue-green infrastructures in industrialized, urbanized and developed regions in China are often multiuse wetlands, located just outside growing urban centers. These areas have multiple development pressures while providing environmental, economic, and social benefits to the local and regional populations. Given the limited information available about the tradeoffs in ecosystem services with respect to competing wetland uses, wetland managers and provincial decision makers face challenges in regulating the use of these important landscapes. In the present study, measurements made by citizen scientists were used to support a comparative study of water quality and wetland functions in two large multiuse wetlands, comparing areas of natural wetland vegetation, tourism-based wetland management and wetland agriculture. The study sites, the Nansha and Tianfu wetlands, are located in two of the most urbanized areas of China: the lower Yangtze River and Pearl River catchments, respectively. Our results indicated that the capacity of wetlands to mitigate water quality is closely related to the quality of the surrounding waters and hydrological conditions. Agricultural areas in both wetlands provided the lowest sediment and nutrient retention. The results show that the delivery of supporting ecosystem services is strongly influenced by the location and use of the wetland. Furthermore, we show that citizen scientist-acquired data can provide fundamental information on quantifying these ecosystem services, providing needed information to wetland park managers and provincial wetland administrators.

The variability in CO2 fluxes at different time scales in natural and reclaimed wetlands in the Yangtze River estuary and their key influencing factors

With the increasing pace of global warming, studies of the carbon cycle and carbon sink capacity of estuarine wetlands have received increasing attention. Estuarine wetlands are often located in economically developed and densely populated areas, and their reclamation has become an important way to acquire land resources. To explore the effect of reclamation on the carbon sink function of estuarine wetlands, the Chongming Dongtan reclaimed wetland and Jiuduansha natural wetland, which are located in the Yangtze River estuary, were selected to investigate their variabilities in carbon fluxes and the main influencing factors using the open path eddy covariance flux monitoring system. The CO2 uptake capacity of the Dongtan reclaimed wetland was significantly weaker than that of the Jiuduansha natural wetland (P < 0.05). The difference in carbon fluxes between the two wetlands was mainly influenced by plant growth and carbon fixation, which accounted for 70.7% of the variation, with soil respiration being the second most important factor. The soil water content and nitrogen and phosphorus concentrations in the reclaimed wetland significantly decreased due to the barrier to water flow presented by a dam (P < 0.01). Nitrogen limitation was the main reason for the poor plant growth in the reclaimed wetland. Although nitrogen inputs in the natural wetland promoted soil respiration (40.6%), they were overshadowed by the inhibitory effect of soil moisture and salinity (55.8%). It was therefore possible to improve the carbon sink function of reclaimed wetlands if plant growth and carbon fixation efficiency could be enhanced without promoting soil respiration.

Buried hurricane legacies: increased nutrient limitation and decreased root biomass in coastal wetlands

AbstractPlant identity and cover in coastal wetlands is changing in worldwide, and many subtropical salt marshes dominated by low‐stature herbaceous species are becoming woody mangroves. Yet, how changes affect coastal soil biogeochemical processes and belowground biomass before and after storms is uncertain. We experimentally manipulated the percent mangrove cover (Avicennia germinans) in 3 × 3 m cells embedded in 10 plots (24 × 42 m) comprising a gradient of marsh (e.g., Spartina alterniflora, Batis maritima) and mangrove cover in Texas, USA. Hurricane Harvey made direct landfall over our site on 25 August 2017, providing a unique opportunity to test how plant composition mitigates hurricane effects on surface sediment accretion, soil chemistry (carbon, C; nitrogen, N; phosphorus, P; and sulfur, S), and root biomass. Data were collected before (2013 and 2016), one‐month after (2017), and one‐year after (2018) Hurricane Harvey crossed the area, allowing us to measure stocks before and after the hurricane. The accretion depth was higher in fringe compared with interior cells of plots, more variable in cells dominated by marsh than mangrove, and declined with increasing plot‐scale mangrove cover. The concentrations of P and δ34S in storm‐driven accreted surface sediments, and the concentrations of N, P, S, and δ34S in underlying soils (0–30 cm), decreased post‐hurricane, whereas the C concentrations in both compartments were unchanged. Root biomass in both marsh and mangrove cells was reduced by 80% in 2017 compared with previous dates and remained reduced in 2018. Post‐hurricane loss of root biomass in plots correlated with enhanced nutrient limitation. Total sulfide accumulation as indicated by δ34S, increased nutrient limitation, and decreased root biomass of both marshes and mangroves after hurricanes may affect ecosystem function and increase vulnerability in coastal wetlands to subsequent disturbances. Understanding how changes in plant composition in coastal ecosystems affects responses to hurricane disturbances is needed to assess coastal vulnerability.

Seasonal Variation in Populations of Eurasian Coot Fulica atra: Relationships with Environmental Variables in Mediterranean Wetlands

Mediterranean wetlands represent a broad variety of natural resources with a huge role in the maintenance of biological diversity. Waterbirds are significant components of this diversity. Among them, the Eurasian Coot Fulica atra is a key species when studying the correlations and interactions between waterbirds and environmental variables, because of its abundance, ease of detection, and relation with some basic aspects of the functioning of wetlands. The present study aimed to analyse the annual and seasonal variation in populations of Eurasian Coot in 31 wetlands in Andalusia, southern Spain, from 2003 to 2008, paying particular attention to correlations with biotic and abiotic variables. The results showed a positive correlation between water depth and coot abundance, while a negative relationship was observed with salinity and no correlation was observed between wetland size and coot abundance. These environmental variables, together with submerged macrophyte coverage, stand out as playing important roles in the use of habitat by coots in Andalusian wetlands.

Ecological stability evaluation of tidal flat in coastal estuary: A case study of Liaohe estuary wetland, China

The tidal flat, located at the forefront of the coastal estuary wetland, serves as a peripheral defense line to maintain the stable ecological function of the estuary wetland. Therefore, the accurate identification of the stable state of a tidal flat is rendered as the decision-making basis for the restoration and management of estuary wetland ecosystems. Conducted at the tidal flat of the Liaohe Estuary Wetland, the study established a comprehensive evaluation index of tidal flat ecological stability (ECO-CSI) based on the Pressure-State-Response model and Rough Set theory. The driving factors and threshold values which affected the stability of the tidal flat were identified. The results showed that the average ECO-CSI value of the tidal flat during the past 30 years was 0.44 indicating, in general, a relatively stable state of the tidal flat. On the other hand, in 2017 the ECO-CSI value was 0.25, pointing that the tidal flat is in an unstable state currently. Among the factors affecting the tidal flat ecological stability, the artificial development activities were the major driving factors, and the urbanization and the traffic road scale were the key driving factors leading to the instability of the tidal flat. Of the natural factors, the sediment discharge, the flow in flood season, and the precipitation in the upstreams were the key guarantee factors for maintaining the material supply of the tidal flat. The threshold values for maintaining the ecological stability of the tidal flat in the Liaohe Estuary wetland were determined that the sediment discharge of the Liaohe River should be not less than 792.91 × 104t⋅y-1 and the scale of traffic roads in the tidal flat should be less than or equal to 770.9244 hm2. Hence, in the development and utilization of tidal flats and coastal wetlands, unreasonable human development activities should be minimized to avoid damage to the integrity and natural dispositions of the tidal flat. In this way, the stability of the tidal flat could be improved, contributing to the ecological security for the overall stability of the estuary wetland ecosystem.

Crab bioturbation alters nitrogen cycling and promotes nitrous oxide emission in intertidal wetlands: Influence and microbial mechanism

Intertidal wetlands provide important ecosystem functions by acting as nitrogen (N) cycling hotspots, which can reduce anthropogenic N loading from land to coastal waters. Benthic bioturbations are thought to play an important role in mediating N cycling in intertidal marshes. However, how the burrowing activity of benthos and their microbial symbionts affect N transformation and greenhouse gas nitrous oxide (N2O) emission remains unclear in these environments. Here, we show that bioturbation of crabs reshaped the structure of intertidal microbial communities and their N cycling function. Molecular analyses suggested that the microbially-driven N cycling might be accelerated by crab bioturbation, as the abundances of most of the N related functional genes were higher on the burrow wall than those in the surrounding bulk sediments, except for genes involved in N fixation, dissimilatory nitrate reduction to ammonium (DNRA), and N2O reduction, which were further confirmed by isotope-tracing experiments. Especially, the potential rates of the main N2O production pathways, nitrification and denitrification, were 2-3 times higher in the burrow wall sediments. However, even higher N2O emission rates (approximately 6 times higher) were observed in this unique microhabitat, which was due to a disproportionate increase in N2O production over N2O consumption driven by burrowing activity. In addition, the sources of N2O were also significantly affected by crab bioturbation, which increased the contribution of hydroxylamine oxidation pathway. This study reveals the mechanism through which benthic bioturbations mediate N cycling and highlights the importance of considering burrowing activity when evaluating the ecological function of intertidal wetlands.

From natural habitats to successful application - Role of halophytes in the treatment of saline wastewater in constructed wetlands with a focus on Latin America

In many parts of the world wastewater is not treated at all or only to a limited extend because there are no resources available to establish an efficient wastewater treatment plant and there are also insufficient resources for operation and maintenance costs. Constructed wetlands (CWs) are nature-based solutions to treat wastewater in a highly cost-efficient manner. They can be very efficient and effective when well designed and maintained. Latin America is rich in saline natural wetlands. These can be used as prototypes for CWs treating saline process or wastewater. Similar to natural saline wetlands CWs can deliver several ecosystem services. This review focuses on saline wetlands and will first present the protagonists, the salt-tolerant plant species belonging to the halophytes with respect to their physiological and biochemical functions in wetlands. In a second step, their remediating activities which are used in many ways by local people will be shown in an exemplary manner. A number of CWs established in different regions, including Latin America, will be introduced as case studies. Halophytes are already being used in a number of CWs as biofilter but their usage could be increased, for example to treat aquaculture effluents and the biomass has a high potential for valuable compounds (i.e. metabolites) or for bioenergy production. Lastly, aspects of sustainability and ecosystem services of saline natural and constructed wetlands are shown with an emphasis on charting a way forward for the future holistic implementation of saline systems in Latin America.

Response of microbial community composition and function to emergent plant rhizosphere of a constructed wetland in northern China

To understand the mechanisms by which emergent plants influence the microbial communities in wetland sediments, we analyzed the response of microbial composition, abundance, metabolic activity, and metabolic genes to three emergent plant species [Cyperus alternifolius L. (Cyp), Typha angustifolia L. (Typ), and Phragmites australis (Cav.) Trin. ex Steud. (Phr)], and determined the important physicochemical properties of the soils and root exudates in Zhaoniu River Constructed Wetland in northern China. We found the composition of both the microbial communities and the metabolic genes differed between rhizosphere and non-rhizosphere sediments. The rhizosphere microbial abundance in Phr in summer was significantly higher than in the other two plants and in the non-rhizosphere. The rates of microbial respiration and ammonia oxidation in rhizosphere sediments were significantly higher than those in non-rhizosphere sediments. Our statistical analyses showed that the total organic carbon (TOC) concentration in root exudates and the oxidation–reduction potential (ORP) significantly influenced the differences in the composition, abundance, and metabolic activities of the microbial community and metabolic genes between rhizosphere and non-rhizosphere sediments, suggesting that the secretion of root exudates and oxygen by emergent plants was the main mechanism affecting the composition and function of the microbial community. As the result of the high levels of TOC and the ORP, the rhizosphere sediments showed relatively high abundances of the genes related to biodegradation of xenobiotic compounds. By contrast, non-rhizosphere sediments showed relatively high abundances of genes related to carbon fixation and sulfate reduction, possibly due to the low levels of TOC and ORP. Plants with an enhanced ability to secrete root exudates and oxygen, such as Phr, should be preferred in constructed wetlands to increase the metabolic activity of sediment microbial communities. This study extends our understanding of the mechanisms by which the plant rhizosphere affects the ecological functions of wetlands.

Grading Evaluation of the Structural Connectivity of River System Networks Based on Ecological Functions, and a Case Study of the Baiyangdian Wetland, China

River system network (RSN) connectivity is important to maintain the environmental and ecological functions of wetlands. Quantitative evaluation of connectivity can provide crucial support for efforts to improve wetland connectivity and to restore and protect wetland ecosystems. Most existing evaluation methods uniformly generalise RSN to form an undifferentiated RSN of edges and nodes that is taken as a whole to evaluate the connectivity. However, actual RSNs comprise rivers, canals, ditches, lakes, and ponds, which differ substantially in their structures, morphologies, and attributes. The mix of RSN elements therefore defines grades that give RSNs distinctive characteristics. Moreover, RSNs with different grades perform different ranges of environmental and ecological functions. The existing evaluation methods, which have some limitations, do not account for these characteristics. To account for these differences, we examined the grade characteristics and their impact on environmental and ecological functions. We established a grading system of RSN elements and a grading method of RSN, and constructed the structural connectivity evaluation indicator system for RSNs at different grades. On this basis, we propose a method for grading evaluation of RSN connectivity. We used China’s Baiyangdian Wetland to demonstrate the use of the system and validate the results. The proposed method provided an objective and accurate evaluation of RSN connectivity and clarified the differences in connectivity among RSNs with different grades, thereby providing improved guidance for the development and maintenance of the environmental and ecological functions of RSNs.

Wintering waterbird assemblage in an emerging wetland of West Bengal, India: characterization for conservation management

Abstract Waterbirds constitute a prominent biota and reflect the ecosystem health and functionality of the freshwater wetlands. Documentation of the bird species assemblages of wetlands is therefore carried out as a part of monitoring of wetlands from a sustainability viewpoint. Using the emerging wetland of Purbasthali, West Bengal, India, as a model study area, the diversity of the associated bird species was estimated to supplement necessary information for conservation management of birds and ecosystems. The point count method was applied to count the waterbirds from each sighting location with a 25 m radius covering 360° arc and the counting period lasted 10 min for each site, and counts were made in the winter of 2016/2017. The data on the waterbirds encountered were recorded and subjected to diversity analysis, including the residential status, global population trend and feeding guilds. Apparently, the wetland was considered as suitable habitat for 27 waterbird species, which could be grouped under 24 genera, 10 families and 5 orders. Among these, the family Anatidae with maximum relative density and abundance dominated in the wetland. Out of the 27 recorded species, 5 species were widespread winter visitors, 3 species widespread resident, as well as, widespread winter visitors and 2 species were sparse local winter visitors. A globally near threatened species, the Black-headed Ibis (Threskiornis melanocephalus) was very common in the sampling sites. The waterbird assemblage in the wetland was dominated by carnivores followed by omnivores and herbivores. The abundance of the waterbirds with considerable variations in the foraging guild reflects availability and exploitation of multiple resources of the Purbasthali wetlands. Prominence in the differences in relative abundance of the different waterbirds could be linked with the heterogeneity in the habitat quality. The present information on waterbird assemblage calls for appropriate measures for conservation of the species and appropriate management of Purbasthali wetlands.

Ecohydrology: A management tool for aquatic ecosystem and SDGs implementation

The availability and quality of water resources are not only to support human health and well-being, but also are providing the functioning of essential ecosystems, including rivers, wetlands, lakes and coastal ecosystems. The contamination of the aquatic ecosystem certainly carries a substantial loss, not only for the environment but also for human beings who use the goods and services of the environment. Water related problems often cannot be managed and overcome completely because of sectoral approach, monodisciplinary and unintegrated. Trans disciplinary science dealing with the interaction of hydrological processes and the dynamics of biology and/or ecology in various spatial, temporal conditions and human life practices around its environment is called ecohydrology. The ecohydrology concept is agreed to solve water related problems in the world. It is included in one of UNESCO IHP VIII themes to support SDGs achievement. This article aims to demonstrate the concept of ecohydrology in supporting sustainable water resource management. Based on the implementation of ecohydrology concept in three different demonstration sites, the results showed that it has been agreed as the solution to improve and restore river basin and lake ecosystem functions and services. It is important to note that the implementation of ecohydrology should consider economic valuation, political and government support as well as local society involvement in order to get effective and sustainable solutions for managing water resources.

Modeling Alternative Approaches to the Biodiversity Offsetting of Urban Expansion in the Grenoble Area (France): What Is the Role of Spatial Scales in ‘No Net Loss’ of Wetland Area and Function?

It is increasingly common for developers to be asked to manage the impacts of their projects on biodiversity by restoring other degraded habitats that are ecologically equivalent to those that are impacted. These measures, called biodiversity offsets, generally aim to achieve ‘no net loss’ (NNL) of biodiversity. Using spatially-explicit modeling, different options were compared in terms of their performance in offsetting the impacts on wetlands of the planned urban expansion around Grenoble (France). Two implementation models for offsetting were tested: (a) the widespread bespoke permittee-led restoration project model, resulting in a patchwork of restored wetlands, and (b) recently-established aggregated and anticipated “banking” approaches whereby larger sets of adjacent parcels offset the impacts of several projects. Two ecological equivalence methods for sizing offsets were simulated: (a) the historically-prevalent area-based approach and (b) recently introduced approaches whereby offsets are sized to ensure NNL of wetland functions. Simulations showed that a mix of functional methods with minimum area requirements was more likely to achieve NNL of wetland area and function across the study area and within each subwatershed. Our methodology can be used to test the carrying capacity of a landscape to support urban expansion and its associated offsetting in order to formulate more sustainable development plans.