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Part 1 of this review synthesizes recent research on status and climate vulnerability of freshwater and saltwater wetlands, and their contribution to addressing climate change (carbon cycle, adaptation, resilience). Peatlands and vegetated coastal wetlands are among the most carbon rich sinks on the planet sequestering approximately as much carbon as do global forest ecosystems. Estimates of the consequences of rising temperature on current wetland carbon storage and future carbon sequestration potential are summarized. We also demonstrate the need to prevent drying of wetlands and thawing of permafrost by disturbances and rising temperatures to protect wetland carbon stores and climate adaptation/resiliency ecosystem services. Preventing further wetland loss is found to be important in limiting future emissions to meet climate goals, but is seldom considered. In Part 2, the paper explores the policy and management realm from international to national, subnational and local levels to identify strategies and policies reflecting an integrated understanding of both wetland and climate change science. Specific recommendations are made to capture synergies between wetlands and carbon cycle management, adaptation and resiliency to further enable researchers, policy makers and practitioners to protect wetland carbon and climate adaptation/resiliency ecosystem services.

Because wetland restoration projects are becoming more common and are expensive, it is important to evaluate their success. Evaluation studies common use measurements of soils, vegetation, hydrology and wildlife to evaluate the success of wetland restoration. In contrast, the diversity of macrobenthos and their relationships with environmental factors are often neglected. To better understand the success of wetland restoration, we examined the abundance and diversity of macrobenthos in different stages of a freshwater wetland restoration project in the Yellow River Delta in China, with reference to environmental factors that might explain macrobenthic patterns. Macrobenthic species richness and density were greater in the oldest restoration area versus the younger and no-treatment areas. Macrobenthic biomass, however, was greatest in the no-treatment area. The oldest restoration area had deeper water levels, lower salinities, softer and wetter soils, and higher soil organic, nitrogen and carbon contents, and these variables largely distinguished the macrobenthic samples in a CCA analysis. A combination of landscape position and recovery time (time since the restoration was implemented) likely explains the abiotic differences among restoration areas. We recommend an adaptive management strategy, guided by long-term monitoring and experiments, to improve the success of this and other wetland restoration projects.

Interactions between surface water and groundwater (SW-GW), composed of complex hydrological networks, maintain a dynamic balance between water regimes and salinity in coastal wetlands. Impacted by reclamation activity, however, changes in water regimes and salinity have resulted in wetland degradation. To mitigate such reclamation impacts on coastal wetlands, it is vital to understand the role of SW-GW interactions involved in maintaining the integrity of coastal wetlands. The objectives of this review were to: ( i ) outlining SW-GW interactions; ( ii ) addressing ecological responses to changes in water regimes and salinity; and ( iii ) exploring modeling techniques used to ascertain interactions between groundwater and coastal wetlands. Key findings are as follows: SW-GW interactions control water regimes and salinity while maintaining the integrity of coastal wetlands; the combined effects of water and salinity have an impact on ecological processes and patterns disturbed by hydrological pulses; and the distribution of physically-based models is an approach that can provide a profound means by which to understand the vital role in maintaining hydrological connectivity. Further research is required to fully reveal SW-GW interactions in maintaining coastal wetlands integrity and the mitigating effects reclamation has on coastal wetlands.

Many ecosystems, even in protected areas, experience multiple anthropogenic impacts. While anthropogenic modification of bottom‐up (e.g., eutrophication) and top‐down (e.g., livestock grazing) forcing often co‐occurs, whether these factors counteract or have additive or synergistic effects on ecosystems is poorly understood. In a Chilean bio‐reserve, we examined the interactive impacts of eutrophication and illegal livestock grazing on plant growth with a 4‐yr fertilization by cattle exclusion experiment. Cattle grazing generally decreased plant biomass, but had synergistic, additive, and antagonistic interactions with fertilization in the low, middle, and high marsh zones, respectively. In the low marsh, fertilization increased plant biomass by 112%, cattle grazing decreased it by 96%, and together they decreased plant biomass by 77%. In the middle marsh, fertilization increased plant biomass by 47%, cattle grazing decreased it by 37%, and together they did not affect plant biomass. In the high marsh, fertilization and cattle grazing decreased plant biomass by 81% and 92%, respectively, but together they increased plant biomass by 42%. These interactions were also found to be species specific. Different responses of plants to fertilization and cattle grazing were likely responsible for these variable interactions. Thus, common bottom‐up and top‐down human impacts can interact in different ways to affect communities even within a single ecosystem. Incorporating this knowledge into conservation actions will improve ecosystem management in a time when ecosystems are increasingly challenged by multiple interacting human impacts.

A new classification of coastal wetlands along the coast of China has been generated that is compatible with the Ramsar Convention of 1971. The coastal wetlands have been divided into two broad categories with overall nine subcategories. On this basis, a series of coastal wetland maps, together covering the coast of mainland China, have been produced based on topographic maps acquired in the 1970s and satellite images acquired in 2007. These document substantial wetland losses over this period. In the 1970s, the total coastal wetland area in China was 5.76× 10 4 km 2 , whereas in 2007, it was 5.36×10 4 km 2 , indicating a loss of 7 %. Over this approximately 40-year period, the area of natural coastal wetlands decreased from 5.74×10 4 to 5.09×10 4 km 2 , while that of artificial coastal wetlands increased from 240 to 2,740 km 2 . Due to shoreline and sea-level changes, newly formed coastal wetlands amounted to 2,460 km 2 , while coastal wetland loss amounted to 6,310 km 2 in the period from the 1970s to 2007. When excluding shallow coastal waters (depths between 0 and −5 m), nearly 16 % of Chinese coastal wetlands have been lost between the 1970s and 2007.

The faucet snail (Bithynia tentaculata) was introduced to the Great Lakes region in the late 1800s. Faucet snails alter native community dynamics and are an intermediate host for multiple trematode parasites that can be lethal to waterfowl when the snails are consumed. Although faucet snails have been established in the Great Lakes for over a century, their populations appear to have remained small for most of this period and their known distribution was limited to the lower Great Lakes, though basin-wide surveys were lacking until recently, so snails may have gone undetected. We compiled data from a five-year coastal wetland monitoring program spanning all of the Great Lakes, providing a basin-wide inventory of faucet snail populations and confirming the snail’s presence in every Great Lake. Further, we identified potential drivers of faucet snail occurrence and abundance (individuals per sampling replicate) across the basin and within individual lakes to identify factors that could lead to elevated risk of range expansion. Across the basin and within individual lakes, faucet snail occurrence was related to human recreational transport (proximity to a boat launch) and eutrophication (anthropogenic land-use, elevated nutrient concentrations). In addition, at sites where faucet snails occurred, they were most abundant at wetlands with surrounding forest cover, suggesting that the species can thrive in a range of environmental conditions. Our results suggest that limiting passive transport of faucet snails is vital to minimizing their spread to remote wetlands where the snails may thrive once established.

Freshwater supplementation is often used for wetland restoration and ecosystem health protection. Understanding temporal patterns of aquatic metabolism caused by freshwater supplementation may help optimize wetland restoration designs. We investigated the short-term changes in aquatic metabolism and potential driving factors at two sites dominated by Phragmites australis and Suaeda salsa , respectively, in a restored coastal wetland located in the Yellow River Delta. Results showed that metabolism was influenced by freshwater supplementation. There was a wide range of variation in gross primary production (GPP) from 0.04 to 49.78 mg O 2 L −1 d −1 , ecosystem respiration (ER) from 3.37 to 45.86 mg O 2 L −1 d −1 , and net ecosystem metabolism (NEM) from −12.92 to 9.01 mg O 2 L −1 d −1 . GPP was more sensitive than ER as a response to flooding and, thus, decreases in NEM led to change of ecosystem from autotrophic to heterotrophic or from heterotrophic to more heterotrophic within one day. Several factors, including water depth, nutrient, salinity, pH, and turbidity, collectively influenced the variation in metabolism. Salinity is a particularly important factor that affected the metabolism rate of the coastal wetland. These findings suggest that a moderate water flow rate (e. g., ≤ 20 cm d −1 ) may help increase GPP post-flooding.

Restoration has been elevated as an important strategy to reverse the decline of coastal wetlands worldwide. Current practice in restoration science emphasizes minimizing competition between outplanted propagules to maximize planting success. This paradigm persists despite the fact that foundational theory in ecology demonstrates that positive species interactions are key to organism success under high physical stress, such as recolonization of bare substrate. As evidence of how entrenched this restoration paradigm is, our survey of 25 restoration organizations in 14 states in the United States revealed that >95% of these agencies assume minimizing negative interactions (i.e., competition) between outplants will maximize propagule growth. Restoration experiments in both Western and Eastern Atlantic salt marshes demonstrate, however, that a simple change in planting configuration (placing propagules next to, rather than at a distance from, each other) results in harnessing facilitation and increased yields by 107% on average. Thus, small adjustments in restoration design may catalyze untapped positive species interactions, resulting in significantly higher restoration success with no added cost. As positive interactions between organisms commonly occur in coastal ecosystems (especially in more physically stressful areas like uncolonized substrate) and conservation resources are limited, transformation of the coastal restoration paradigm to incorporate facilitation theory may enhance conservation efforts, shoreline defense, and provisioning of ecosystem services such as fisheries production.

1. Coastal wetland ecosystems are expected to migrate landwards in response to rising seas. However, due to differences in topography and coastal urbanization, estuaries vary in their ability to accommodate migration. Low-lying urban areas can constrain migration and lead to wetland loss (i.e. coastal squeeze), especially where existing wetlands cannot keep pace with rising seas via vertical adjustments. In many estuaries, there is a pressing need to identify landward migration corridors and better quantify the potential for landward migration and coastal squeeze. 2. We quantified and compared the area available for landward migration of tidal saline wetlands and the area where urban development is expected to prevent migration for 39 estuaries along the wetland-rich USA Gulf of Mexico coast. We did so under three sea level rise scenarios (0.5, 1.0, and 1.5 m by 2100). 3. Within the region, the potential for wetland migration is highest within certain estuaries in Louisiana and southern Florida (e.g. Atchafalaya/Vermilion Bays, Mermentau River, Barataria Bay, and the North and South Ten Thousand Islands estuaries). 4. The potential for coastal squeeze is highest in estuaries containing major metropolitan areas that extend into low-lying lands. The Charlotte Harbor, Tampa Bay, and Crystal-Pithlachascotee estuaries (Florida) have the highest amounts of urban land expected to constrain wetland migration. Urban barriers to migration are also high in the Galveston Bay (Texas) and Atchafalaya/Vermilion Bays (Louisiana) estuaries. 5. Synthesis and applications. Coastal wetlands provide many ecosystem services that benefit human health and well-being, including shoreline protection and fish and wildlife habitat. As the rate of sea level rise accelerates in response to climate change, coastal wetland resources could be lost in areas that lack space for landward migration. Migration corridors are particularly important in highly urbanized estuaries where, due to low-lying coastal development, there is not space for wetlands to move and adapt to sea level rise. Future-focused landscape conservation plans that incorporate the protection of wetland migration corridors can increase the adaptive capacity of these valuable ecosystems and simultaneously decrease the vulnerability of coastal human communities to the harmful effects of rising seas.

Tidal wetlands experiencing increased rates of sea-level rise (SLR) must increase rates of soil elevation gain to avoid permanent conversion to open water. The maximal rate of SLR that these ecosystems can tolerate depends partly on mineral sediment deposition, but the accumulation of organic matter is equally important for many wetlands. Plant productivity drives organic matter dynamics and is sensitive to global change factors, such as rising atmospheric CO 2 concentration. It remains unknown how global change will influence organic mechanisms that determine future tidal wetland viability. Here, we present experimental evidence that plant response to elevated atmospheric [CO 2 ] stimulates biogenic mechanisms of elevation gain in a brackish marsh. Elevated CO 2 (ambient + 340 ppm) accelerated soil elevation gain by 3.9 mm yr −1 in this 2-year field study, an effect mediated by stimulation of below-ground plant productivity. Further, a companion greenhouse experiment revealed that the CO 2 effect was enhanced under salinity and flooding conditions likely to accompany future SLR. Our results indicate that by stimulating biogenic contributions to marsh elevation, increases in the greenhouse gas, CO 2 , may paradoxically aid some coastal wetlands in counterbalancing rising seas.