Wetland Restoration Projects Research Articles

Microbial Community Structure of Soil Methanogens and Methanotrophs During Degradation and Restoration of Reed Wetlands in the Songnen Plain

Wetlands are an important global source and sink of methane. However, human activities and climatic conditions are causing serious degradation of wetlands in China. In response to this, the relevant departments have progressively carried out wetland restoration projects over the past few years. To investigate the response of microbial communities of bacteria, methanogens, and methanotrophs during degradation and restoration of wetlands, soil samples were collected from undegraded reed wetlands, degraded reed wetlands, and restored reed wetlands in the Songnen Plain. Microbial diversity and community composition were studied by high-throughput sequencing based on the 16S rRNA gene of bacteria, the mcrA gene of methanogens, and the pmoA gene of methanotrophs. The results indicate that the degradation of reed wetlands results in a decrease in bacterial and methanogenic α-diversity and an increase in methanotrophic α-diversity. Bacterial α-diversity and methanogenic α-diversity were both significantly positively correlated with soil water content. At different taxonomic levels, higher relative abundances of Rhizobiales and Methanobacteriaceae were detected in the undegraded wetland soils. Wetland degradation decreased the relative abundance of Rhizobiales but increased that of the pathogenic bacteria Burkholderiaceae and microorganisms resistant to harsh and extreme environments including Sphingomonas, Rubrobacter, Methylobacter, Methylomonas, and Methylococcus. In the restored wetland soils, the relative abundances of Bacillus, Methanosarcinaceae, Methanomicrobiaceae, and the type Ⅱ methanotroph Methylocystis were higher. Therefore, different wetland conditions can indirectly change soil properties and, consequently, change the community structure of methanogens and methanotrophs.

Functional diversity of macroinvertebrates as a tool to evaluate wetland restoration

Abstract Ecological restoration of aquatic ecosystems has become widespread in recent decades. Although the recovery of biodiversity in restored wetlands has been studied from a taxonomic perspective, our knowledge of how functional biodiversity recovers remains poorly understood. We studied the functional diversity of macroinvertebrate communities in 32 Mediterranean temporary ponds 6–7 years after their creation during a restoration in South‐West Spain, and compared them with 10 natural reference sites during two consecutive hydroperiods. We compared alpha functional diversity indices, and the individual contributions of new ponds and reference sites to the regional functional beta diversity, as well as to its turnover and nestedness components. We also investigated the influence of environmental and spatial variables on the dissimilarities of functional beta diversity and its components between new ponds and reference sites. Alpha functional diversity in new ponds was lower than in reference sites. Although the contribution of new ponds to the regional functional beta diversity was similar to that of reference sites, the latter contributed more to functional turnover while new ponds contributed more to functional nestedness. Dispersal limitation coupled with environmental filtering structured the functional variation in communities between new ponds and reference sites, but their relative importance differed between beta components. New ponds can hold species with unique functional compositions, but their contribution to the regional functional beta diversity was mostly due to trait losses with respect to reference sites. Synthesis and applications. Considering different aspects of functional diversity of invertebrate communities can help elucidate the processes and mechanisms through which ecosystems recover following restoration. We encourage the use of trait‐based approaches to identify trends in processes and patterns that can guide future wetland restoration projects.

Wetland Restoration Planning Approach Based on Interval Fuzzy Linear Programming under Uncertainty.

When planning wetland restoration projects, the planting area allocation and the costs of the restoration measures are two major issues faced by decision makers. In this study, a framework based on the interval fuzzy linear programming (IFLP) method is introduced for the first time to plan wetland restoration projects. The proposed framework can not only effectively deal with interval and fuzzy uncertainties that exist in the planning process of wetland restorations but also handle trade-offs between ecological environment benefits and economic cost. This framework was applied to a real-world wetland restoration planning problem in the northeast of China to verify its validity and examine the credibility of the constraints. The optimized results obtained from the framework that we have developed indicate that higher ecological and social benefits can be obtained with optimal restoration costs after using the wetland restoration decision-making framework. The optimal restoration measure allocation schemes obtained by IFLP under different credibility levels can help decision makers generate a range of alternatives, which can also provide decision suggestions to local managers to generate a satisfactory decision-making plan. Furthermore, a comparison was made between the IFLP model and ILP model in this study. The comparison results indicate that the IFLP model provides more information regarding ecological environment and economic trade-offs between the system objective, certainty, and reliability. This framework provides managers with an effective way to plan wetland restoration projects, while transference of the model may help solve similar problems.

Analyzing spatial variability of drivers of coastal wetland loss in the northern Gulf of Mexico using Bayesian multi-level models

ABSTRACT A modeling framework that can quantify the impact of multiple potential drivers on coastal wetland loss while estimating its uncertainties is needed to better conserve and restore these valuable ecosystems. We developed a Bayesian multi-level modeling framework to predict the areal wetland loss in the northern Gulf of Mexico, driven by relative sea-level rise (RSLR), vegetation productivity, tidal range, wave height, and coastal slope. We further investigated how the impact of these site or local-scale biogeophysical factors on wetland loss differed by watershed unit. The results indicate the importance of accounting for watershed boundaries where the coastal wetlands are located when evaluating their loss. The effects of RSLR, wave height, and tidal range on wetland loss differed by watershed. Inclusion of streamflow and land use/land cover at the watershed scale did not improve model predictions while other relevant watershed-scale covariates, such as sediment availability, are not available. Based on the 95% credible intervals of the posteriors of the model coefficients, there were only five watersheds among the 14 studied where RSLR, wave height, or tidal range, showed positive or negative effects on coastal wetland loss. The results demonstrate the complexity of modeling wetland loss processes as no single dominant driver was identified for most of the watersheds. Furthermore, the need to account for multiple drivers simultaneously to ensure the effectiveness of costly wetland restoration projects clearly appears warranted when evaluating wetland loss processes over a broad spatial scale.

Eco-hydrology as a driver for tidal restoration: Observations from a Ramsar wetland in eastern Australia.

Land reclamation projects and the installation of drainage infrastructure has impacted coastal wetlands worldwide. By altering water levels and inundation extent, these activities have changed the viable ecosystems onsite and resulted in the proliferation of freshwater species. As more than 50% of tidal wetlands have been degraded globally over the last 100 years, the importance of this issue is increasingly being recognised and tidal wetland restoration projects are underway worldwide. However, there are currently limited sites where large-scale reintroduction of tidal flushing has been implemented with the explicit aim to foster the growth of a threatened ecosystem. In this study, the tidal restoration of an internationally recognised Ramsar listed wetland in eastern Australia is described to highlight how coastal saltmarsh can be targeted by mimicking inundation depths and hydroperiod across the 410-ha site. Coastal saltmarsh is particularly important to this site as it is part of the east Australasian flyway for migratory birds and the minimum saltmarsh extent, as listed within the Ramsar’s limits of acceptable change, have been breached. To recreate coastal saltmarsh habitat onsite, water level and hydroperiod criteria were established based on similar vegetation patterns within the adjacent estuary. A calibrated 2D hydrodynamic model of the site was then used to test how the preferred inundation criteria could be applied to the largest possible restored wetland area. Once optimised, a synthetic tidal signal was implemented onsite via automated hydraulic controls. The onsite vegetation response over an 8-year period was assessed to highlight the ecosystem response to controlled tidal inundation and denoted substantial saltmarsh expansion during the period. The techniques applied onsite have successfully met the restoration targets and can be applied at similar sites worldwide, offsetting sea level rise impacts to natural inundation hydroperiod.

Recovering ecosystem functions in a restored salt marsh by leveraging positive effects of biodiversity

AbstractNatural and managed ecosystems provide a variety of ecological, economic, and cultural benefits; yet most have been altered by human activity such that they exhibit deficits in both biodiversity and functionality. Identifying factors accelerating the recovery of key species and associated functions in degraded systems is therefore a global priority. We tested the hypotheses that explicitly incorporating biodiversity into restoration design will lead to greater ecosystem function and that positive effects of diversity will strengthen over time due to an increase in the importance of complementarity relative to selection effects. We did this by manipulating salt marsh plant species richness across a tidal elevation gradient as part of a coastal wetland restoration project in southern California. Overall, diversity enhanced biomass accumulation in experimental plots, with the magnitude of the effect strengthening from one to three years post‐restoration due to a combination of decreasing performance in monocultures and increasing performance in multispecies mixtures over time. Positive diversity effects were initially due exclusively to selection, as mixtures were dominated by species also exhibiting high performance in monoculture, although the identity of the highest performing species varied across tidal elevations and over time. By the end of the study, complementarity, indicative of niche partitioning and/or positive interactions among species, contributed to productivity at least as much as selection effects. Our study provides real‐world support for a recent theoretical model predicting strong positive biodiversity effects when functionally different species coexist in a heterogeneous landscape. Incorporating biodiversity into restoration designs can result in net gains in ecosystem function especially in low diversity systems, yet shorter experiments lacking broad environmental and species trait variability may both underestimate the strength of and misidentify the mechanisms underlying positive diversity effects.

Multi‐Species Occupancy Modeling Provides Novel Insights into Amphibian Metacommunity Structure and Wetland Restoration

A fundamental goal of community ecology is to understand species-habitat relationships and how they shape metacommunity structure. Recent advances in occupancy modeling enable habitat relationships to be assessed for both common and rare species within metacommunities using multi-species occupancy models (MSOM). These models account for imperfect species detection and offer considerable advantages over other analytical tools commonly used for community analyses under the elements of metacommunity structure (EMS) framework. Here, we demonstrate that MSOM can be used to infer habitat relationships and test metacommunity theory, using amphibians. Repeated frog surveys were undertaken at 55 wetland sites in southeastern Australia. We detected 11 frog species from three families (Limnodynastidae, Myobatrachidae, and Pelodryadidae). The rarest species was detected at only one site whereas the most common species was detected at 42 sites (naive occupancy rate 0.02-0.76). Two models were assessed representing two competing hypotheses; the best-supported model included the covariates distance to the nearest site (connectivity), wetland area, presence of the non-native eastern mosquitofish (Gambusia holbrooki), proportion cover of emergent vegetation, an interaction term between Gambusia and emergent vegetation cover, and the proportion canopy cover over a site. Hydroperiod played no detectable role in metacommunity structure. We found species-habitat relationships that fit with current metacommunity theory: occupancy increased with wetland area and connectivity. There was a strong negative relationship between occupancy and the presence of predatory Gambusia, and a positive interaction between Gambusia and emergent vegetation. The presence of canopy cover strongly increased occupancy for several tree frog species, highlighting the importance of terrestrial habitat for amphibian community structure. We demonstrated how responses by amphibians to environmental covariates at the species level can be linked to occupancy patterns at the metacommunity scale. Our results have clear management implications: wetland restoration projects for amphibians and likely other taxa should maximize wetland area and connectivity, establish partial canopy cover, and eradicate Gambusia or provide aquatic vegetation to mitigate the impact of this non-native fish. We strongly advocate the use of MSOM to elucidate the habitat drivers behind animal occupancy patterns and to derive unbiased occupancy estimates for monitoring programs.

Successional dynamics of a 35 year old freshwater mitigation wetland in southeastern New Hampshire.

The long-term ecological success of compensatory freshwater wetland projects has come into question based on follow-up monitoring studies over the past few decades. Given that wetland restoration may require many years to decades to converge to desired outcomes, long-term monitoring of successional patterns may increase our ability to fully evaluate success of wetland mitigation projects or guide adaptive management when needed. In Portsmouth, New Hampshire a 4 ha wetland was constructed in an abandoned gravel quarry as off-site compensatory mitigation for impacts to a scrub-shrub swamp associated with property expansion. Building upon prior evaluations from 1992 and 2002, we conducted a floral survey in 2020 to compare results with prior surveys to document vegetation successional trends over time. In addition, we monitored the avian community throughout the growing season as a measure of habitat quality. The plant community mirrored documented successional trends of freshwater wetland restoration projects as native hydrophytes dominated species composition. Plant species composition stabilized as the rate of turnover, the measurement of succession, declined by nearly half after 17 years. Researchers should consider long-term monitoring of specific sites to better understand successional patterns of created wetlands as we documented long time frames required for the development of scrub-shrub swamps, red maple swamps, and sedge meadows. High species richness was attributed to beaver activity, topographic heterogeneity from Carex stricta tussocks, and the seed bank from the application of peat from the original wetland. Habitat heterogeneity of open water, herbaceous cover, and woody vegetation supports a diverse avian community including 11 wetland dependent species. Although the mitigation project has not created the full area of lost scrub-shrub swamp after 35 years, it has developed a structurally complex habitat and diverse avian community that effectively provides the functions and values of the impacted system.

Wetland restoration in the East Dongting Lake effectively increased waterbird diversity by improving habitat quality

Wetland restoration is an effective way to recover degraded wetlands worldwide. The Dongting Lake wetland, an important wintering habitat for waterbirds, has suffered considerable degradation due to climate change and human disturbance during the last two decades; however, wetland restoration projects have now been implemented to improve waterbird diversity in the Dongting Lake. Based on annual waterbird and habitat survey data (2012/2013–2019/2020), we aimed to compare the differences in habitat variables (e.g., sedge [Carex spp.] meadow area, mudflat area, water area, and the normalized difference vegetation index of the sedge [Carex spp.] meadow) between the restored and unrestored wetlands to confirm whether wetland restorations could improve habitat quality. We also evaluated whether wetland restoration could effectively improve waterbird diversity by comparing the differences in waterbird populations at the community, foraging guild, feeding habitat guild, and species levels in the restored and unrestored wetlands. The results indicated that the restored wetland could provide more diverse and suitable habitats than the unrestored ones, particularly in terms of a sufficient variety of water habitats of different depths for waterbirds. The restored wetland was able to support substantial and diverse waterbird populations during the winter season. Specifically, compared to the unrestored wetlands, the restored wetland generally had higher species richness, individual density, and Shannon–Wiener diversity index at the community level; higher densities or proportions of different foraging guilds (tuber feeders, herbivores, fish eaters, insectivores, and omnivores, except herbivores geese), and of different feeding habitat guilds (G [0–10 cm], G (20–50 cm), G (20–70 cm), and G (>70 cm) guilds); and higher densities or proportions of the target species (except the lesser white-fronted goose and bean goose) at the species level. The larger waterbird populations in the restored wetland might be closely related to suitable crucial habitats, as indicated by positive correlation between their abundance and suitable habitat areas. Creating diverse suitable habitats for waterbirds, according to their habitat requirements, should be the first consideration in future wetland restorations. These findings provide a basis for wetland restoration and protection of wintering waterbird diversity in the Dongting Lake as well as in the middle and lower reaches of the Yangtze River floodplain.

Multi-species occupancy modeling provides novel insights into amphibian metacommunity structure and wetland restoration.

A fundamental goal of community ecology is to understand species-habitat relationships and how they shape metacommunity structure. Recent advances in occupancy modeling enable habitat relationships to be assessed for both common and rare species within metacommunities using multi-species occupancy models (MSOM). These models account for imperfect species detection and offer considerable advantages over other analytical tools commonly used for community analyses under the elements of metacommunity structure (EMS) framework. Here, we demonstrate that MSOM can be used to infer habitat relationships and test metacommunity theory, using amphibians. Repeated frog surveys were undertaken at 55 wetland sites in southeastern Australia. We detected 11 frog species from three families (Limnodynastidae, Myobatrachidae, and Pelodryadidae). The rarest species was detected at only one site whereas the most common species was detected at 42 sites (naive occupancy rate 0.02-0.76). Two models were assessed representing two competing hypotheses; the best-supported model included the covariates distance to the nearest site (connectivity), wetland area, presence of the non-native eastern mosquitofish (Gambusia holbrooki), proportion cover of emergent vegetation, an interaction term between Gambusia and emergent vegetation cover, and the proportion canopy cover over a site. Hydroperiod played no detectable role in metacommunity structure. We found species-habitat relationships that fit with current metacommunity theory: occupancy increased with wetland area and connectivity. There was a strong negative relationship between occupancy and the presence of predatory Gambusia, and a positive interaction between Gambusia and emergent vegetation. The presence of canopy cover strongly increased occupancy for several tree frog species, highlighting the importance of terrestrial habitat for amphibian community structure. We demonstrated how responses by amphibians to environmental covariates at the species level can be linked to occupancy patterns at the metacommunity scale. Our results have clear management implications: wetland restoration projects for amphibians and likely other taxa should maximize wetland area and connectivity, establish partial canopy cover, and eradicate Gambusia or provide aquatic vegetation to mitigate the impact of this non-native fish. We strongly advocate the use of MSOM to elucidate the habitat drivers behind animal occupancy patterns and to derive unbiased occupancy estimates for monitoring programs.

Declining wintering shorebird populations at a temperate estuary in California: A 30-year perspective

Abstract Worldwide, shorebird populations are declining. Our objectives were to examine abundance trends of shorebirds regularly wintering at Tomales Bay, Marin County, California, accounting for the local effects of rainfall, raptors, and the restoration of part of the bay to tidal wetlands. From November 1989 to February 2019, we conducted 177 comprehensive winter shorebird surveys of Tomales Bay; we averaged 5.7 ± 0.9 (mean ± SD) winter surveys per year. In 30 yr, we counted 1,215,821 shorebirds of 31 species. We used generalized linear models and multi-model inference to evaluate trends in shorebird abundance while accounting for local sources of variation. We conducted separate analyses for 14 species seen in at least 20 of the 30 yr of monitoring and for all shorebird species combined. During the study, the abundance of all species combined declined 66% (52% in the North Bay and 81% in the South Bay) with the most rapid decline in the first 10 yr of monitoring. Of 13 species for which year was in the top model, 10 species decreased in abundance and 3 species increased. Dunlin and Western Sandpiper accounted for the greatest losses in total numbers. The best-supported models to estimate trends in shorebirds included predictors for year and North Bay vs. South Bay. Of the local variables we considered, rainfall was included in 10 of the 15 best-supported models (including all species combined), negatively affecting the numbers of all species except Willets. The wetland restoration project was included in 5 top models, with a short-term positive impact. Raptor abundance was included in 3 top models with mixed results. Our results show that effective conservation and management of local shorebird populations must be linked with regional/global efforts if we are to reverse negative shorebird trends.

Lagoon of Islands, Tasmania: Ecosystem response to dam wall removal

Lagoon of Islands was a rare wetland of high conservation value, supporting floating islands of vegetation before it was dammed to supply water for consumptive use downstream. After damming, water quality declined to such an extent that in 2013, the dam wall was removed and a wetland restoration project was commenced, resulting in immediate improvements in water quality and, within five years, regeneration of a plant community largely composed of dominant species of the original wetland.

Effects of Wetland Restoration and Conservation Projects on Soil Carbon Sequestration in the Ningxia Basin of the Yellow River in China from 2000 to 2015

The long-term use of wetlands stresses wetland ecosystems and leads to degradation and C loss. This study explored an optimal remote sensing-multivariate linear regression model (RS-MLRM) for estimating wetland soil organic carbon (SOC) by using a combination of the measured SOC and above ground biomass (AGB) from 273 samples, textural features, spectral information, and a vegetation index calculated from Landsat-8 images using the Ningxia Basin of the Yellow River as the study area. To derive the optimal predictor model for SOC, these variables were regressed against the measured SOC. These were used to predict SOC and evaluate the contribution of wetland restoration and conservation projects to soil carbon sequestration and sinks on the Ningxia Basin of the Yellow River in early (2000 and 2005), intermediate (2010), and recent (2015) years. The results show that from 2000 to 2015, the project-induced contribution to C sequestration was 20.49 TC, with an annual sink of 1.37 TC. This accounted for 54.06% of the total wetland ecosystem C sequestration on the Ningxia Basin of the Yellow River. Moreover, there was a significant success of restoration and conservation projects regarding C sequestration. These restoration and conservation projects have substantially contributed to CO2 mitigation in the arid area.

The indication of soil microorganism to wetland restoration in Three River Source Area

Post-assessment of wetland restoration projects offers insight into project efficiency, effectiveness and sustainability. In order to evaluate the wetland restoration in three river source area, Qinghai Province, 16SrRNA high-throughput sequencing, OTU analysis, Alpha diversity analysis, etc., were used to analyze the soil microorganisms in the three restoration measures. Then, the species distribution and species richness cluster information were obtained. Compared with the wetland without any restoration measures, the results showed that the soil health index in three plots was higher or lower, which was specifically reflected in: replanting plot > rodent control plot > enclosure plot. Finally, the health status of alpine meadow wetland was comprehensively analyzed. The results in this work can offer reference for the restoration and protection of meadow wetland in Qinghai-Tibet Plateau.

Assessing hydrodynamic effects of ecological restoration scenarios for a tidal-dominated wetland in Liaodong Bay (China)

Estuarine wetlands have experienced a variety of ecological and environmental problems caused by natural and anthropogenic factors. China has proposed a series of measures and made great efforts to control coastal degradation; however, decision makers still urgently need to know which measures to implement and how they will influence the estuarine environment and functions. This study used field observations, a hydrodynamic model, and statistical methods to investigate the effects of potential restoration scenarios on hydrodynamic conditions in the tidal-influenced estuarine wetland system, Liaodong Bay (China). Results reveal that the average total phosphorus, organic carbon, available phosphorus, pH, total nitrogen content, and moisture content in the soil and sediment environment were 0.04 ± 0.003%, 0.84 ± 0.25%, 16.3 ± 4.7 mg/kg, 8.3 ± 0.1, 0.07 ± 0.02%, and 44 ± 2%, respectively, exhibiting an overall trend of degradation. A series of restoration scenarios in regards to hydrodynamic regulation and tidal inputs were used to preserve the ecological value of the estuarine wetland. Model simulations indicate that the significant improvement of hydrodynamic fields (inundation depth and flow velocity) is more likely to occur when the tidal amplitudes reach around 2 m, while relatively weak responses can be observed when the tidal levels are lower than 1 m. Additionally, the construction of floodgates may play a key role in determining the tidal inputs and flowpaths across the wetland. The modifications in micro-topography of the wetland may play a complementary role in enhancing the connectivity condition via increased creek depth of 0.5 m and width up to around 20 m. This work represents a first attempt in exploring hydrodynamic effects of restoration scenarios for a tidal-dominated wetland. An improved understanding of the estuarine system also highlights that the design and implementation of wetland restoration projects should use more comprehensive measures to achieve long-term landscape management, connectivity planning, and ecological sustainability.

Impact of soil salinity on mangrove restoration in a semiarid region: a case study from the Saloum Delta, Senegal

Ongoing losses to mangrove forests globally have prompted increased interest in restoration programs that seek to restore vital ecosystem functions and services. In many cases, data on local‐scale environmental tolerances of mangrove species used in reforestation efforts is lacking, and failure of restoration projects has been attributed to incorrect species selection in plantations. Here, we assess the impact of soil salinity on the early establishment success of monospecific red mangrove Rhizophora mangle reforestation projects in the Saloum Delta, Senegal, a region where widespread mangrove restoration efforts are ongoing. At soil salinities >60 ppt, stomatal conductance, photosystem II operating efficiency, and growth of planted R. mangle seedlings were severely reduced. Similarly, after 1–3 years, survival of mangrove seedlings decreased in soil salinities of >60 ppt. In contrast, we recorded naturally occurring black mangrove Avicennia germinans growing in exceptionally hypersaline conditions (90 ppt), representing some of the most saline vegetated ecosystems on Earth. The findings reported herein can be used to inform species choice in reforestation projects and help improve success rates of coastal wetland restoration projects in semiarid regions.

Restoring wetland biodiversity using research: Whole‐community facilitation by beaver as framework

Abstract Wetlands are declining worldwide, and there is a great need for their restoration and creation. One natural agent of wetland engineering is beavers, Castor spp., which have returned or are returning to many parts of their former range. We initially studied the facilitative effect of the beaver Castor canadensis on a waterbird community consisting of three waders and four ducks in boreal wetlands in southern Finland. Both waterbird species diversity and abundance increased when beavers impounded a pond. Common teal Anas crecca and green sandpiper Tringa ochropus were the species showing the most positive numerical response, but the other five species also increased upon flooding. This article evaluates how the results of the study have been used in management, both in theory and practice. The whole‐community facilitation concept has been taken up in numerous articles considering the restorative effects of beavers. It has also been used as ecological background when planning and executing man‐made wetland projects in Finland within both the public and the private sectors. Our study and its publication in Aquatic Conservation: Marine and Freshwater Ecosystems have set a foundation for further evidence‐based management of waterbird communities. As the results show, having beavers as wetland managers is a feasible tool for creating and restoring wetlands for waterbirds and other biota. Moreover, wetland restoration projects are becoming more popular endeavours, owing to an understanding of the diverse benefits of wetlands. Flooding by beavers is used as a model for managers when creating man‐made wetlands; for example, in urban areas where it is difficult to maintain beavers.

Early Ecosystem Development Varies With Elevation and Pre-Restoration Land Use/Land Cover in a Pacific Northwest Tidal Wetland Restoration Project

Tidal wetland restoration through dike removal can enhance coastal ecosystem services, such as flood attenuation, fish production, and carbon sequestration. However, landscape-level heterogeneity may influence recovery. For a 169-ha restoration project in Tillamook Bay, Oregon, we hypothesized that areas of more intensive pre-restoration land use/land cover (cropping, grazing) would differ more from reference conditions before restoration than less-intensive uses and that initial post-restoration recovery would vary by land-use/land-cover type and wetland elevation. Before the restoration, the project site overall had higher non-native plant cover, lower elevation and groundwater levels, and lower soil pH than reference high marsh, with some differences by land-use/land-cover type. The cropped and grazed areas were strongly dominated by non-native species, such as Phalaris arundinacea, and were 74 and 31 cm lower than reference high marsh. Less intensively managed areas had elevations intermediate to the cropped and grazed areas and a trend towards higher native plant cover. The restoration led to higher dry-season groundwater levels, increased soil salinity to mesohaline conditions, and a 10-fold increase in soil pH at the project site, while reducing total plant cover. The degree of pre- to early post-restoration change for some parameters differed by land-use/land-cover type (total and non-native plant cover) and by wetland elevation (soil salinity, pH, and accretion rate; and total and non-native plant cover). Our results suggest that pre-restoration heterogeneity in elevation and land cover/land use may influence early post-restoration recovery. Restoration planning can incorporate such spatial variability into management targets and interventions for specific outcomes.

The Impact of Biophysical Processes on Sediment Transport in the Wax Lake Delta (Louisiana, USA)

Sediment transport in coastal regions is regulated by the interaction of river discharge, wind, waves, and tides, yet the role of vegetation in this interaction is not well understood. Here, we evaluated these variables using multiple acoustic and optical sensors deployed for 30–60 days in spring and summer/fall 2015 at upstream and downstream stations in Mike Island, a deltaic island within the Wax Lake Delta, LA, USA. During a flooding stage, semidiurnal and diurnal tidal impact was minimal on an adjacent river channel, but significant in Mike Island where vegetation biomass was low and wave influence was greater downstream. During summer/fall, a “vegetated channel” constricted the water flow, decreasing current speeds from ~13 cm/s upstream to nearly zero downstream. Synchrony between the upstream and downstream water levels in spring (R2 = 0.91) decreased in summer/fall (R2 = 0.84) due to dense vegetation, which also reduced the wave heights from 3–20 cm (spring) to nearly 0 cm (summer/fall). Spatial and temporal differences in total inorganic nitrogen and orthophosphate concentrations in the overlying and sediment porewater were evident as result of vegetation growth and expansion during summer/fall. This study provides key hourly/daily data and information needed to improve the parameterization of biophysical models in coastal wetland restoration projects.

Ecological risk assessment of the wetlands in Beijing-Tianjin-Hebei urban agglomeration

Wetlands are some of the most highly productive ecosystems on earth and are one of the most important environments for human survival and development. However, with the acceleration of industrialization and urbanization, wetlands have been constantly occupied and destroyed and have even disappeared in some areas, so it is necessary to establish a reasonable and scientific ecological risk assessment system for wetlands. In this study, 181 counties in Beijing-Tianjin-Hebei urban agglomeration (Jing-Jin-Ji) were selected as the research objects, and an index system with 22 indexes was established from two aspects: the external hazard degree and the vulnerability of the wetland itself. The ecological risk of the wetlands during 6 periods from 1990 to 2015 was comprehensively evaluated by long-term data and multiple index factors. The results showed that (1) due to the decrease in the hazard degree and the increase in the vulnerability, the ecological risk of the wetlands in Jing-Jin-Ji first increased and then decreased; (2) more than 60% of the counties were at the middle or middle-high risk level, especially in the center of urban development, which generally had higher risk level than other regions; (3) most wetland parks were at the middle-high risk level, while wetland reserves, reservoirs and lakes were mostly in the low risk or middle-low risk level. Therefore, in recent years, the implementation of wetland protections and restoration policies and projects has played a significant role in reducing the ecological risk of the wetlands. In the future, more targeted management and protection measures need to be formulated and followed up in time.