Wetland Loss Research Articles

Assessment of Wetland Change on the Delmarva Peninsula from 1984 to 2010

Stubbs, Q.; Yeo, I.-Y.; Lang, M.; Townshend, J.; Sun, L.; Prestegaard, K., and Jantz, C., 2020. Assessment of wetland change on the Delmarva Peninsula from 1984 to 2010. Journal of Coastal Research, 36(3), 575–589. Coconut Creek (Florida), ISSN 0749-0208.The decline in wetland extent and condition emphasizes the need for sound wetland restoration and conservation policies, which require baseline information on wetland status, change, and change drivers. Multiple wetland maps are available, but they can be quite inconsistent bcause of different input and generation techniques, dates, and objectives. Moderate-resolution (30 m2) regional land-cover data sets (LCDs) were analyzed to (1) quantify historical wetland changes on the Delmarva Peninsula at multiple spatial scales between 1984 and 2010, (2) identify differences in the spatial area of wetland change and discuss the source of and implications for these differences, and (3) investigate the extent to which drivers of wetland change can be identified using existing LCDs. The following regional LCDs were considered: the National Oceanic and Atmospheric Administration Coastal Change Analysis Program (C-CAP), the U.S. Geological Survey (USGS) Chesapeake Bay Land Cover Data Series (CBLCD), and the USGS National Land Cover Database. The C-CAP and CBLCD had the highest spatial agreement at 97%, and an average of 76% spatial agreement with the U.S. Fish and Wildlife Service National Wetland Inventory. The highest percentages of net wetland loss occurred between 1992 and 2001, whereas net wetland gain occurred between 2001 and 2010. Wetlands were predominantly converted (e.g., lost) to croplands/grass/shrubs (67%) and water (11%), which could be linked to drivers such as agriculture and sea-level rise.

What did China's National Wetland Conservation Program Achieve？Observations of changes in land cover and ecosystem services in the Sanjiang Plain

China implemented the National Wetland Conservation Program (NWCP) from 2002 to protect and rehabilitate wetlands. Under the background of sustainable development, assessment on the effectiveness of the NWCP is important to ecosystem management, especially in the Sanjiang Plain, the largest marsh distribution area and hotspot area with wetland loss. To achieve this aim, this study examined the changes in land cover and ecosystem services (ESs) from 1990 to 2000 and from 2000 to 2015 in the Sanjiang Plain as well as the nine national nature reserves for wetlands (NNRWs) by means of Landsat series images and the InVEST model. Results reveal that the NWCP played critical roles in reducing wetland loss and improving regional ESs. The shrinkage rate of wetlands in the Sanjiang Plain has been decreased remarkably, with a declined rate of wetland loss from 750 km2 yr−1 to 189 km2 yr−1. The reduction rate of habitat area in good suitable grade and ecosystem carbon stock declined notably during the period 2000–2015 compared to the period 1990–2000. The amount of water retention increased by 5.4%, while the grain production capacity was enhanced by nine times from 1990 to 2015. Specifically, since 2000, the reduction rate of wetland area in NNRWs (33 km2 yr−1) was obviously lower than that in the entire Sanjiang Plain, whilst various ESs in NNRWs were better than that in the whole Sanjiang Plain. This study is expected to provide an example for evaluating the effectiveness of the NWCP at other regions and support regional wetland conservation management.

Numerical and Experimental Analyses of Breakwater Designs for Turbulent Flow Characteristics and Sediment Transport Under Coastal Wave Actions

Abstract The goal of the study is to identify optimal breakwater designs to be placed on the banks of various water bodies in coastal Louisiana, to prevent the coastal erosion. Coastal erosion is a significant concern for Louisiana's wavy coastline. The loss of coastal wetlands is threatening the environment and the economic development. One of the ways to prevent coastal erosion and wetland losses is by using breakwaters designed to reduce the wave energy and change the transport of sediments brought by the waves. The objective of this research is to analyze the turbulent characteristics around specially designed three-dimensional (3D) breakwaters, and its impact on sediment deposition under coastal wave actions. Both computational fluid dynamics (CFD) simulations and experimental measurements were conducted. In order to validate the CFD models used for this study, the simulation results were compared to data measured from a scale-down experiment. Once the validity of the CFD models has been confirmed on three miniature panels, namely, a solid panel, a panel with three holes, and a panel with eight holes, the simulations were scaled up to the actual size of the designed breakwater panels for tests. The breakwater designs aim to allow sediment pass through the holes, to deposit sediment at target areas, and to reduce wave actions. There were three different panel-design cases simulated in this study. The results of 3D CFD simulations of these panels were compared and analyzed to determine the performance of each design in terms of wave reduction and sediment retention.

Assessing wetland sustainability by modeling water table dynamics under climate change

The hydrological responses of geographically isolated wetlands to climate change is insufficiently considered and qualified, with weak but critical hydrologic connectivity to surrounding uplands. This study simulated the essential physical hydrological processes under climate change by coupling a distributed process-based model with an assemblage of 20 general circulation models under Representative Concentration Pathway scenarios 8.5 and 4.5 for 1950–2099. A susceptibility rate was proposed to assess wetland sustainability under climate change. Different model capabilities in hydro-climatic interactions of geographically isolated wetlands were quantified by developing a process-based and an empirical model. The results show that the water table will have declined 68 cm by 2100, with decreasing water availability (−289 cm). Based on the sustainability assessment, the wetland will dry with an increasing risk from baseline of 63%–99% in 2100. The risk of wetland loss will increase from baseline of 37%–93% in 2100. The high risk of unsustainable wetlands in the study area indicates high susceptibility and vulnerability of the wetland hydrological system to climate change. The study has wide implications in conserving the entire hydrological continuum of geographically isolated wetlands and surrounded uplands. It also provides information to make adaptative strategies for wetlands under threat from climate change.

Saltmarsh grass supports fishery food webs in subtropical Australian estuaries

All fishery food webs are ultimately underpinned by organic matter produced by algae and plants, some of it supplied by primary producers at the fringes of fish habitats. This is no different in tropical and subtropical estuaries where secondary production by crustaceans and finfish may depend on coastal wetlands (e.g. mangroves, seagrass, saltmarshes) abutting channels. Coastal urbanisation is a major cause of wetland loss globally. Hypothetically, reduced wetland area may propagate to less fisheries production if wetland contributions to food webs are substantial – this is the prime question addressed here. We sampled key fisheries species in subtropical estuaries in reaches of moderate urbanisation (18–33% of shoreline hardened) and in reference locations dominated by wetlands, on the east coast of Australia. We used triple stable isotopes (C, N, S) to estimate (using mixing models) the trophic contributions of the key primary producers to regional fisheries species. Organic matter from wetland plants, particularly saltmarsh grass (Sporobolus virginicus), underpinned fishery food webs in most cases (with median contributions ranging from 18 to 88% for saltmarsh grass, followed by 6–70% for C3 wetland plants (e.g. mangroves, phragmites) and 3–36% by benthic algae). Moderate levels of urban transformation of estuarine margins did not change the dominance of wetland carbon for fish and crustaceans in settings without significant seagrass meadows. Given the demonstrated importance of saltmarshes, and other coastal wetlands, to regional fisheries production, conservation of these habitats is necessary in the face of multiple anthropogenic threats.

Mapping 30 Years of Change in the Marshlands of Breton Sound Basin (Southeastern Louisiana, U.S.A.): Coastal Land Area and Vegetation Green Cover

Potter, C. and Amer, R., 2020. Mapping 30 years of change in the marshlands of Breton Sound basin (southeastern Louisiana, U.S.A.): Coastal land area and vegetation green cover. Journal of Coastal Research, 36(3), 437–450. Coconut Creek (Florida), ISSN 0749-0208.This study analyzes the 30-year record of Landsat satellite imagery to better understand the patterns and processes of land loss/gain and recent changes in marshland vegetation green cover in coastal wetlands of Breton Sound basin of southeastern Louisiana. Impacted by both Hurricane Katrina in 2005 and Hurricane Gustav in 2008, this vast estuary area just south of New Orleans was mapped at 30 m resolution in 5-year intervals from 1985 to 2017 using the Landsat Normalized Difference Water Index (NDWI) and the Normalized Difference Vegetation Index (NDVI). Results revealed an entirely new picture of marshland change prior to Hurricanes Katrina and Gustav in the Breton Sound basin. Following decades of extensive wetland loss resulting largely from gas and oil well drilling and canal construction, this analysis estimated gains in land area between 1985 and 2005 (pre-Katrina) of 247 km2 across all subbasins of Breton Sound. The largest proportional increases in marshland areas were mapped from dNDWI analysis in the subbasins of Bayou la Loutre, Bayou Pointe-en-Pointe, and Bayou Terre Aux Boeufs, all surrounding the outer Mississippi River Gulf Outlet Canal. Brackish salinity areas were among the first of Louisiana's coastal wetlands to succumb to the hurricane storm surges of 2005 and 2008, as Landsat dNDWI analysis estimated that about 245 km2 of wetlands in the Breton Sound basin were lost to open water from the impacts of Hurricanes Katrina and Gustav. However, combined dNDWI and dNDVI analysis indicated that gains in marshland area and green vegetation cover have occurred at a yearly rate of increase after 2008 comparable to the period between 1985 and 2005. Specific areas of rapid land gain were detected in River aux Chenes and Bayou Bienvenue subbasins, and Bayou Plaquemines and Bayou la Loutre in brackish to saltwater marshland types on the outer margins of Breton Sound basin.

Temporal Patterns of Wetland-Associated Bird Assemblages in Altered Wetlands in Turkey

A loss of wetlands, one of the highly sensitive ecosystems, necessitates the monitoring and assessment of wildlife population trends for the continuity and sustainable management of species. The goal of our study was to evaluate temporal changes in wetland-associated bird composition by conducting monthly counts during December 2006 - November 2007 and March 2015 - February 2016 in Efteni Lake, Duzce, Turkey. This lake has been exposed to structural change including shoreline length, area and depth for the last 50 years. Wetland-associated bird richness decreased, and abundance increased during the decade, but this change was not significant except for two species with an increased population, ferruginous duck Aythya nyroca and great crested grebe Podiceps cristatus. Cluster analyses resulted in two groups: the breeding season from April to September, and the non-breeding season from October to March. The most numerous species were observed mostly during the non-breeding season. Some guilds, including diving carnivores, omnivores, shoreline omnivores and herbivores species were more prevalent during the non-breeding season. The insectivores had higher population densities during the breeding season. Thus, wetland-associated bird abundance during the non-breeding season was higher than during the breeding season, although species richness was the opposite. The planned restoration of habitats of Efteni Lake should have a positive impact on birds by creating more space available to them. Our result should help to better understand the impact of habitat changes on waterbird assemblages. Long-term monitoring of Efteni Lake will be useful for the wetland-associated avian community, and for other animal and plant communities.

Coastal wetlands reduce property damage during tropical cyclones

Coastal wetlands dampen the impact of storm surge and strong winds. Studies on the economic valuation of this protective service provided by wetland ecosystems are, however, rare. Here, we analyze property damage caused by 88 tropical storms and hurricanes hitting the United States between 1996 and 2016 and show that counties with more wetland coverage experienced significantly less property damage. The expected economic value of the protective effects of wetlands varies widely across coastal US counties with an average value of about $1.8 million/km2 per year and a median value of $91,000/km2 Wetlands confer relatively more protection against weaker storms and in states with weaker building codes. Recent wetland losses are estimated to have increased property damage from Hurricane Irma by $430 million. Our results suggest the importance of considering both natural and human factors in coastal zone defense policy.

Management of urban wetlands for conservation can reduce aquatic biodiversity and increase mosquito risk

Abstract Global wetland loss means constructed urban wetlands are an increasingly valuable resource for conservation. However, priorities for managing urban wetlands for conservation are often seen to conflict with management to reduce potential mosquito risks, such as nuisance biting and pathogen transmission. Understanding the ecological consequences of wetland management practices is vital to maximize the conservation value of urban wetlands without negatively impacting public health; however, management practices are often untested. We conducted a landscape‐scale experiment to test the ecological impacts of an existing urban wetland management regime, in which a group of urban wetlands are drained annually to reduce the abundance of an invasive fish, the plague minnow Gambusia holbrooki, and then refilled to provide breeding habitat for a threatened frog, the green and golden bell frog Litoria aurea. We collected and compared aquatic macroinvertebrates and mosquito larvae from these refilled wetlands, and adjacent undrained wetlands, as well as sampling adult mosquito populations on four occasions across summer and autumn. Wetland draining had a significant effect on aquatic macroinvertebrates and larval mosquitoes. Twice as many macroinvertebrates were collected from drained wetlands compared to undrained wetlands, and almost all mosquito larvae were collected from drained wetlands. Differences in macroinvertebrate assemblages and larval mosquitoes at drained and undrained wetlands decreased over time, but total macroinvertebrate abundance and taxa richness did not. Synthesis and applications. While conserving threatened habitats and species is vitally important, our results highlight how wetland management practices can unintentionally impact non‐target species, and potentially public health. As constructed urban wetlands become more common, so too does the need for routine maintenance and management of threatened and invasive species. It is essential that future design and management of urban wetlands considers the impact mosquitoes might have on humans. Pre‐emptive action to control geographically relevant vectors of mosquito‐borne pathogens and nuisance biting species would reduce human exposure to mosquitoes and associated negative impacts, and increase positive conservation outcomes associated with urban wetlands.

Bottom-up processes control benthic macroinvertebrate communities and food web structure of fishless artificial wetlands

In freshwater environments, the relative contributions of top-down and bottom-up effects on invertebrate communities in relation to productivity are largely ecosystem dependent. Artificial wetlands are increasingly developed to compensate for the loss of natural wetlands; however, their trophic processes remain poorly studied. The present study aimed to evaluate the respective contributions of bottom-up and top-down processes in structuring benthic food webs of three artificial wetlands with varying levels of benthic primary productivity. We found that phototrophic-based food webs in our artificial wetlands were controlled from the bottom-up by primary productivity and algal biomass developing at the water–sediment interface. No significant top-down control of herbivore species by invertebrate predators was detected even in the wetland with the highest productivity. Increased richness of invertebrate grazers and scrapers with benthic primary productivity and algal biomass might have dampened the trophic cascade from predators to primary producers. In contrast with the phototrophic-based food web, analyses performed on the detritus-based food web showed that deposit-feeder invertebrate abundance was not correlated with the quantity of organic matter in sediments, suggesting no bottom-up effect of sedimentary organic matter content on deposit-feeders. More surprisingly, deposit-feeders, especially aquatic oligochaetes, seemed to influence the detritus-based food webs by stimulating organic matter processing and bacterial growth through bioturbation. The present study highlights the occurrence of contrasting trophic processes between phototrophic-based and detritus-based food webs which can have implications on ecosystem functions, such as nutrient cycling and energy fluxes.

Improving wetland ecosystem health in China

Abstract To counter widespread wetland loss and deterioration due to rapid socioeconomic development, China implemented a series of wetland conservation and restoration policies that have resulted in an increase in wetland area since 2000. Although wetland loss has been contained, changes in wetland ecosystem health are poorly quantified across China. We report on China’s first nationwide assessment of the spatial-temporal dynamics of wetland ecosystem health based on physical, biological, and chemical indicators from the first wetland inventory (1995–2003) to the second wetland inventory (2009–2013), and identify the potential effects of wetland ecosystem health changes to provide guidance for future wetland conservation management. We found that the wetland ecosystem health comprehensive index increased by 7.2%, indicating that China’s wetland conservation and restoration policies significantly promoted an improvement in wetland ecosystem health. These improvements were concentrated in the middle reaches of the Yangtze River and in the eastern and northern Qinghai-Tibetan Plateau. Deteriorations in wetland ecosystem health were focused in southern provinces and Heilongjiang, which were mainly attributed to population increase and conversion of wetland to cropland, respectively. Although wetland protection and restoration policies have improved wetland ecosystem health without affecting agricultural production, wetland conservation did not prevent the reduction in natural wetland area and the decline in biodiversity throughout China. This analysis demonstrated that a more proactive conservation strategy is required to greatly strengthen wetland conservation management, by expanding the wetland protected area network, strictly obeying wetland ecological redlines, strengthening degraded wetland restoration, and raising population awareness of wetland protection. This study provides a proactive wetland conservation strategy, and indicates that assessment of wetland ecosystem health changes and their driving factors could contribute to a better understanding and further coordination of the relationship between wetland ecological conditions and socioeconomic development.

Geo-Spatial Analysis of Urban Wetlands Loss in Obio/Akpor Local Government Area of Rivers State, Nigeria

Urban wetlands make cities livable in many important ways. They reduce flooding, replenish drinking water, filter waste, provide urban green spaces, and are a source of livelihoods in most urban areas. This study aims to geo-spatially analyze urban wetland loss in Obio/Akpor Local Government Area (LGA), Rivers State, Nigeria. The study analyses land use /land cover changes (LULC) using Landsat7 UTM images of 2000, 2009 and 2018. The satellite images covering the area were acquired and analyzed using ArcGIS10.6. A total area of 25,773.39 sq km was delineated in the study area. After processing the imagery, five LULC classes where developed in ArcGIS environment, such as wetland, built-up area, vegetation, water bodies and bare surface. The study shows that the urban land-use of Obio-Akpor LGA had changed dramatically during the period of 18 years. In 2000, wetlands occupied the second-lowest classes with 9.12% (2352.15 sq.km) of the total classes due to high level of urban development in the area while built-up areas occupied the third-highest classes with 17.62% (4543.83 sq.km) of the total classes. In 2009, the study revealed that the built-up area (urban land use) rose to 19.3% (4975.11 sq.km) and maintained an increase in urban growth due to changes from constructions of many roads and houses while wetlands also surprisingly experienced an increase and occupied the third-highest classes with 19.17% (4942.26 sq.km). Evidence from the study show that 2018 witnessed an expansion in terms of developmental activities in all facets as the built-up area increased in three-fold size within the year, bare surface reduced to a class of 15.47% (4057.29 sq.km) forcing developers to develop towards the wetland ecosystem. The wetlands, therefore, experienced a sharp decline to 4.91% (1266.75 sq.km) due to rapid conversion of wetlands for housing development and excessive urban sprawl and its associated problems of inefficient use of land, urban space and the development of shanty towns/slums. The study concluded that there is a need for the wise use of wetland resources and improvement of institutional arrangement so that wetland policies can be fully integrated into the planning process across all disciplines.

Plant functional connectivity of Nymphoides fallax in geographically isolated temporary wetlands in Mexican highlands

Plant functional connectivity integrates species-environment interactions, dispersal vectors, and landscape structure variables to understand species’ spatial responses to habitat fragmentation. Functional connectivity is still poorly understood for aquatic plants despite the promise it holds for informing wetland conservation across landscapes. Through a landscape genetics approach, we quantified plant functional connectivity among geographically isolated wetlands by genotyping seven nuclear microsatellite loci in 18 populations of Nymphoides fallax, a tetraploid aquatic plant endemic to Mexican and Guatemalan highland wetlands. We tested if wetland connectivity, quantified with three connectivity indices, translated to high genetic diversity within populations and if geographical distance per se explained gene flow among wetlands. We also tested if landscape features such as vegetation and surface water cover explained gene flow among N. fallax populations. Our results show that wetland connectivity is positively associated with genetic diversity over threshold distances up to 5 km. The Si Hanski connectivity index, with wetland area incorporated, was the best predictor explaining the effective number of alleles, allelic richness, and expected heterozygosity. Population-specific FST, as a proxy for gene flow, was better explained by a model including forest cover than by geographical distance or water cover. Our findings highlight the importance of forest conservation to maintain gene flow at the landscape scale for N. fallax and allows the detection of key populations to maintain genetic diversity and connectivity. Understanding wetland connectivity is critical to address wetland loss in human-impacted landscapes.

Refinement of an index of ecological condition for marsh bird communities in lower Great Lakes coastal wetlands

Abstract The Laurentian Great Lakes coastal wetlands are highly productive and biologically diverse ecosystems. Ongoing environmental degradation and wetland loss have resulted in a number of restoration and conservation programs. To facilitate reporting on the health and recovery of these wetlands, various indices of ecological integrity have been developed to distill complex biotic community data into results that are easy to interpret and understand. The Index of Ecological Condition (IEC) approach uses a probabilistic framework to derive an index by fitting the observed assemblage of species based on species occurrence along an a priori environmental gradient. This study refines the original IEC by Howe et al. (2007a) using updated methodologies and focusing on marsh bird communities in lower Great Lakes coastal wetlands. The a priori environmental gradient was redeveloped using finer-scale (minimum mapping unit = 50 m2) landscape data than Howe et al. (2007a), including Phragmites australis as an invasive stressor, and incorporating measures of water quality and submerged aquatic vegetation as watershed-level disturbances. The environmental gradient showed a good relationship with known anthropogenic disturbances. Marsh bird communities were surveyed in lakes Erie and Ontario and wetland species with clear responses to the environmental gradient were selected for inclusion in the IEC. Where detection was low, species were grouped into multispecies guilds. The resulting IEC was comprised of 15 biotic response functions: 12 individual species and 3 species guilds, and was highly correlated with the a priori environmental gradient (R2 = 0.54). Species with strong positive responses included Canada Goose (Branta canadensis), Marsh Wren (Cistothorus palustris), Swamp Sparrow (Melospiza georgiana), and American Bittern (Botaurus lentiginosus). Pied-billed Grebe (Podilymbus podiceps) had a particularly strong response and was highly influential in the IEC. Great Egret (Ardea alba) was the only species with a negative relationship to the environmental gradient. The refined IEC performed well and provides easily understood output for coastal wetland practitioners in the lower Great Lakes, tasked with reporting on the ecological integrity of marsh bird communities.

Assessing the historical adaptive cycles of an urban social-ecological system and its potential future resilience: the case of Xochimilco, Mexico City

As the bulk of the world’s population becomes urban, maintaining urban ecosystem services for environmental and social well-being in cities is crucial. According to resilience theory, maintaining such services requires for a complex adaptive systems perspective that helps in identifying key elements and dynamics behind cross-scale social-ecological interactions. In this context, the objective of this article is to use a resilience “lens” to problematize the imminent loss of an urban wetland using the adaptive cycle model as a heuristic tool. Our case study focuses on the Xochimilco wetland, located in the southern periphery of Mexico City. Xochimilco is characterized by the presence of a complex system of raised bed wetland agriculture (the chinampa system), which was established over 1000 years ago; currently, despite having a recognized cultural and environmental value, it is threatened by increasing urban sprawl, over-exploitation of the aquifer, and water contamination. By conducting a historical analysis of the Xochimilco social-ecological system, we assess how it has gone through phases of the adaptive cycle. As a result, we identify critical elements of the system’s historically maintained resilience and main drivers of system change. From such findings, we present some insights on the possibilities of maintaining the system’s resilience and guidance for future management strategies for the Xochimilco wetland. Lastly, we reflect on the scope and limitations of using a resilience-based approach and an adaptive cycle analysis for addressing urban sustainability problems, especially in cities in the Global South.

Modelling the contribution of ephemeral wetlands to landscape connectivity

Habitat loss and fragmentation continue to drive declines of amphibian populations. Maintaining connectivity between aquatic and terrestrial habitats and across wetlands is critical to amphibian conservation, particularly in regions where climate change may exacerbate habitat loss. Our objective was to study the impact of climate- and human-driven losses in ephemeral wetlands on functional connectivity for amphibians, using the endangered western tiger salamander (Ambystoma mavortium) in British Columbia, Canada as a case study. Land use data and dispersal characteristics for the western tiger salamander were used to develop a spatially-explicit individual-based model of amphibian movement. The model was configured to explore connectivity under three climate scenarios (a wet, average, and dry year), and a land management scenario in which only known breeding sites are conserved. We used a spatial network analysis to identify key ephemeral wetlands that connect otherwise isolated sub-networks across the landscape and probable movement paths between wetlands and the upland terrestrial habitat. Our results illustrate the importance of conserving ephemeral wetlands as stepping stones. We argue that a landscape approach to wetland conservation, rather than just conserving known breeding sites, is essential for retaining viable amphibian populations in a context of human induced habitat loss and climate change.

Pond Excavation Reduces Coastal Wetland Carbon Dioxide Assimilation

AbstractCoastal wetlands comprise important global carbon sinks; however, anthropogenic disturbance accompanied with accelerating sea level rise threaten their continued survival. In this study, we quantified habitat disturbance to salt marshes in Barnegat Bay, New Jersey, resulting from the construction of ponds for mosquito control. Geographic object‐based image analysis of high‐resolution four‐band aerial imagery revealed that over 7,000 ponds were constructed in the marsh complex with pond densities as high as 290 ponds per km2. Physical disturbance from pond creation and sediment dispersal extended to over 17% of the bay's tidal wetlands. By tracking recolonization of vegetation, we estimated that it took 5 years for 51% vegetation recovery and 10 years for 69% recovery, with complete recover (100%) not expected for more than 50 years. This suggests that efforts to extend the lifespan of drowning coastal wetlands through sediment additions might disrupt carbon dioxide assimilation, as effects of disturbance persist. Focusing on greenhouse gas exchange, our work found that areas of marsh vegetation contribute to carbon assimilation (−42 g C · m−2 · year−1), while ponds and areas of bare peat created by pond excavation were associated with carbon emissions (44 and 125 g C · m−2 · year−1, respectively). These results suggest that the conversion of wetlands to ponds—which is a significant driver of coastal wetland loss worldwide—may convert coastal wetlands from greenhouse gas sinks to sources. Additionally, quantifying the area of vegetation within a marsh (vs. bare ground or open water) is important for quantifying their greenhouse gas mitigation function.

Coastal Watershed Forested Wetland Change and Opportunities for Enhanced Collaboration with the Forestry Community

U.S. Fish and Wildlife Service National Wetlands Inventory (NWI) Wetlands Status and Trends reports have documented greater net wetland loss rates in U.S. coastal watersheds than in the rest of the contiguous U.S., and this loss rate has increased through time. Atlantic and Gulf of Mexico coastal watersheds contain 30% of the country’s forested wetlands. Although forested wetlands in this region have a long history of supplying substantial benefits to society, a portion of these habitats are currently being transformed into different land cover types – including both uplands and other types of wetlands. Drivers of forested wetland change in this region are complex, but some loss of area appears to be associated with plantation forestry. Improved understanding of this relationship is necessary to better support informed management of this critical resource. This will require close collaboration between the wetland and forestry communities. Unfortunately, communication between these two communities has been hampered by misconceptions about how wetland and forestry data are collected, and differences in the way key terms are defined. This article summarizes recent Wetlands Status and Trends data, seeks to clarify definitions and current misconceptions involving this dataset, and describes opportunities for future collaboration between the forestry and wetland communities.

Quantifying the Relative Importance of Climate Change and Human Activities on Selected Wetland Ecosystems in China

Climate change and human activities are important factors driving changes in wetland ecosystems. It is therefore crucial to quantitatively characterize the relative importance of these stressors in wetlands. Previous such analyses have generally not distinguished between wetland types, or have focused on individual wetland types. In this study, three representative wetland areas of the upper, middle and lower reaches of the Heilongjiang River Basin (HRB) were selected as the study area. An object-based classification was used with Landsat TM data to extract the spatial distribution of wetland in 1990, 2000 and 2010. We then quantified the relative importance of climate change and human activities on the wetlands by using the R package “relaimpo” package. The results indicated that: (1) the effects of human activities on wetland changes were greater (contribution rate of 63.57%) than climate change in the HRB. Specifically, there were differences in the relative importance of climate change and human activities for wetlands in different regions. Wetlands of the upper reaches were more affected by climate change, while wetlands in the middle and lower reaches were more affected by human activities; (2) climate change had a greater impact (contribution rate of 65.72%) on low intensity wetland loss, while human activities had a greater impact on moderate and severe intensity wetland loss, with respective contribution rates of 57.22% and 70.35%; (3) climate change had a larger effect on the shrub and forested wetland changes, with respective contribution rates of 58.33% and 52.58%. However, human activities had a larger effect on herbaceous wetland changes, with a contribution rate of 72.28%. Our study provides a useful framework for wetland assessment and management, and could be a useful tool for developing wetland utilization and protection approaches, particularly in sensitive environments in mid- and high-latitude areas.

A Citizen Science State of the World’s Wetlands Survey

Citizen science is increasingly recognised as a valuable approach to improve the knowledge and understanding required for robust environmental management. We report on the results of a citizen science survey conducted on the status and trends of over 500 wetlands from across the globe. Whilst many wetlands were reported as being in fair or good ecological character state, many (particularly those already in a poor state) were reported as deteriorating. Although designated Ramsar Sites were reported as currently having a slightly better state than other wetlands, widespread deterioration of Ramsar Sites as well as other wetlands was reported. Significant regional differences were reported on the state of wetlands and their extent of improvement or deterioration. Large wetlands, particularly in Africa but also in Latin America and the Caribbean, were reported to be in a worse, and increasingly deteriorating, state than smaller wetlands in North America, Europe and Oceania. Numerous drivers are contributing to degradation and loss of wetlands. However, our data suggest that positive outcomes can be delivered where local community awareness, implementation of conservation measures, cultural values/traditions, tourism and forestry are proactively integrated in order to achieve the wise use of wetlands.