Marsh Restoration Research Articles

Changes to spotted turtle (Clemmys guttata) habitat selection in response to a salt marsh restoration

Development of coastal New England has led to the replacement of up to 37% of salt marshes with degraded freshwater wetlands, primarily through tidal restrictions. Removing these restrictions to restore salt marsh ecology would improve water quality, increase flood and storm protection, nutrient filtration, erosion control, and carbon sequestration. However, such restorations replace functional freshwater wetlands and could potentially impact freshwater species. Freshwater-dependent wildlife species such as the spotted turtle (Clemmys guttata), may be especially vulnerable to rapid changes in habitat resulting from tidal reintroduction due to their high site fidelity and limited ability to disperse quickly. Conservation of genetically and physically isolated spotted turtle populations as well as the restoration of salt marshes to mitigate climate change impacts are both high priorities on Nantucket Island. These two priorities conflicted in a project to restore tidal hydrology to an impounded freshwater marsh known to host a robust spotted turtle population. We evaluated changes to spotted turtle home range size and location and habitat use in response to salt marsh restoration over eight years. Home range size did not change but the location of home ranges shifted into bordering wetlands landward of the tidal salt water influence. Spotted turtles selected remaining freshwater marshes and shrub swamps while avoiding developed land and areas of establishing salt marsh within areas that had previously been high quality habitat. This study suggests prioritizing conservation of wetlands adjacent to planned salt marsh restoration to provide habitat for freshwater species to migrate.

Rapid tidal marsh development in anthropogenic backwaters

AbstractTidal marsh restoration and creation is growing in popularity due to the many and diverse sets of services these important ecosystems provide. However, it is unclear what conditions within constructed settings will lead to the successful establishment of tidal marsh. Here we provide documentation for widespread and rapid development of tidal freshwater wetlands for a major urban estuary as an unintended result of early industrial development. Anthropogenic backwater areas established behind railroad berms, jetties, and dredge spoil islands resulted in the rapid accumulation of clastic material and the subsequent initiation of emergent marshes. In one case, historical aerial photos document this transition occurring in less than 18 years, offering a timeframe for marsh development. Accretion rates for anthropogenic tidal marshes and mudflats average 0.8–1.1 and 0.6–0.7 cm year−1, respectively, equivalent to two to three times the rate of relative sea level rise as well as the observed accretion rate at a 6000+ year‐old reference marsh in the study area. Paired historical and geospatial analysis revealed that more than half of all the tidal wetlands on the Hudson River were likely triggered by anthropogenic development since the onset of the industrial era, including two‐thirds of the emergent cattail marsh. These inadvertently constructed tidal wetlands currently trap roughly 6% of the Hudson River's sediment load. Results indicate that when sediment is readily available, freshwater tidal wetlands can develop relatively rapidly in sheltered settings. The study sites serve as useful examples to help guide future tidal marsh creation and restoration efforts.

Tidal Marsh Restoration Optimism in a Changing Climate and Urbanizing Seascape

Tidal marshes (including saltmarshes) provide remarkable value for many social (cultural, recreational) and environmental (fish production, water quality, shoreline protection, carbon sequestration) services. However, their extent, condition, and capacity to support these services are threatened by human development expansion, invasive species, erosion, altered hydrology and connectivity, and climate change. The past two decades have seen a shift toward working with managers to restore tidal marshes to conserve existing patches or create new marshes. The present perspective examines key features of recent tidal marsh restoration projects. Although optimism about restoration is building, not all marshes are the same; site-specific nuances require careful consideration, and thus, standard restoration designs are not possible. Restoration projects are effectively experiments, requiring clear goals, monitoring and evaluation, and adaptive management practices. Restoration is expensive; however, payment schemes for ecosystem services derived from restoration offer new ways to fund projects and appropriate monitoring and evaluation programs. All information generated by restoration needs to be published and easily accessible, especially failed attempts, to equip practitioners and scientists with actionable knowledge for future efforts. We advocate the need for a network of tidal marsh scientists, managers, and practitioners to share and disseminate new observations and knowledge. Such a network will help augment our capacity to restore tidal marsh, but also valuable coastal ecosystems more broadly.

Atmospheric concentrations and ecosystem fluxes of CH2Cl2, CHCl3 and CCl4 along tidal and vegetation gradients within a coastal salt marsh in Eastern China

There is a causal relationship between atmospheric concentrations and ecosystem fluxes of DCM, CF, and CT. Atmospheric concentrations of these gases likely regulate ecosystem fluxes, and they may also be influenced in turn by exchanges with the ecosystem. The relationship between atmospheric concentrations and fluxes of DCM, CF, and CT is bound to affect the occurrence and fate of these gases in the environment. However, how atmospheric concentrations and ecosystem fluxes are related remains poorly understood. Here, the dynamics of atmospheric concentrations and ecosystem fluxes of these three gases were investigated using samples from three transects along tidal and vegetation gradients within a coastal salt marsh in Eastern China. Substantial variation was found among the dynamics of the three gases, which also showed different relationships between their atmospheric concentrations and ecosystem fluxes. In general, the ecosystem flux of each gas was negatively correlated with its ambient concentration in the atmosphere, although this varied across time and space. For example, high ambient concentrations of DCM and CT often corresponded with high ecosystem fluxes, but high ambient concentrations of CF corresponded to low ecosystem fluxes. Gas fluxes were significantly correlated, suggesting that the three gases have a common source. However, there may be differences between marine and terrestrial inputs, helping to explain the inconsistent flux-atmospheric concentration relationships. External inputs (e.g., coastal seawater and terrestrial biomass burning) may act to regulate ambient gas concentrations in the coastal salt marsh atmosphere, altering patterns of exchange between the ecosystem and atmosphere. Salt marsh ecosystems may be worthy of attention as sinks for DCM, CF, and CT. Ecological restoration of coastal salt marshes is therefore critical to help mitigate high atmospheric concentrations of DCM, CF, and CT.

Pond Dynamics Yield Minimal Net Loss of Vegetation Cover Across an Unditched Salt Marsh Landscape

Ponds in salt marshes are often misinterpreted as a symptom of degradation, yet ponds can also be part of a cyclical process of pond formation, expansion, breaching by tidal creeks, and vegetation recovery. Pond dynamics may be altered by accelerated sea level rise, with consequences for the long-term stability of ecosystems. This study tests the prediction that ponds are in dynamic equilibrium across one of the largest expanses of unditched salt marsh in the Northeast USA by (1) examining change in pond and marsh area between 1970 and present in both ditched and unditched regions and (2) by tracking individual pond dynamics across an 87-year time series. Across all marshes, vegetated area declined by 6.3%, with losses primarily due to edge erosion. Ditched marsh had significantly less pond area than unditched marsh. In unditched marshes, we found that net pond area has remained unchanged since 1970 because the amount of marsh conversion to ponds is equivalent to the amount of pond recovery to marsh. The overall extent of ponds connected to tidal creeks is increasing relative to isolated ponds that retain water at low tide, which suggests that some rates of change may be decoupling. This may correspond to a decline in the rate of pond formation, but other factors such as an increase in pond breaching rate and a lag in vegetation recovery rate may also contribute to this pattern. A nuanced understanding of marsh ponds needs to be incorporated into marsh condition assessments and establishment of restoration priorities so that ponds are not interpreted as evidence of degradation when they are exhibiting a recovery cycle. Unditched marshes around the world are a rare resource that remains essential for advancing scientific understanding and serving as reference sites for restoration of marshes altered by past management.

Connecting changes in Euphrates River flow to hydropattern of the Western Mesopotamian Marshes

The Mesopotamian Marshlands are the largest wetland system in the Middle East. Historically, these marshes served as the floodplains of the Tigris and Euphrates rivers, and they are currently connected to these rivers via surface water feeder canals. Historically, the Mesopotamian marshes received consistent flood pulses during the spring season from March to May. In recent decades, however, several large dams have been constructed in the Tigris and Euphrates basins for irrigation purposes and power generation, severely altering the flow regime, which along with other direct anthropogenic activities, has severely degraded the marsh ecosystem. This work quantifies changes in the riverine flow regime and how they have affected the hydro-pattern of the western Mesopotamian marshes (focusing on the western Al-Hammar marsh) and describes the role of hydrological drivers that are important for marsh restoration. The total area of the Al-Hammar marshes has been reduced from an average of 2800 km2 before 1970 to a minimum of 240 km2 in recent decades, concomitant with reductions in annual average Euphrates River flow (at Hit) from 967 to 602 m3/s and marked flow regime alteration. While climate warming and reduced precipitation were observed in the basin, changes in the fundamental precipitation-flow relationship implicate infrastructural changes (upstream dams) as the primary reason for these changes. This analysis quantified how flow variability under historic and contemporary conditions have affected wetland area and other hydro-pattern characteristics and suggests that at an annual average of least 70 m3/s of water deliveries to the western Mesopotamian marsh are required to restore 1000 km2 of wetland area. Our hope is that this focus on the river-marsh connection will help inform predictive models and scenario analysis for restoration of this unique social-ecological system.

Inoculating rhizome-propagated Sporobolus pumilus with a native mycorrhizal fungus increases salt marsh plant growth and survival

Salt marshes are ecosystems of significant ecological importance for coastal stability and fundamental roles in marine ecosystems. Salt marshes are declining due to anthropogenic and natural causes including sea level rise. Coastal restoration efforts have increased worldwide, but many fail in long-term coastal stability. We used a naturally occurring arbuscular mycorrhizal fungus (AMF) to test whether survival and early growth of the salt marsh grass Sporobolus pumilus (formerly Spartina patens) improved under simulated salt marsh conditions. Using a tidal mesocosm bench, we grew inoculated plants with varying AMF treatments under simulated tidal regimes to determine if AMF could aid in establishment of healthy Sporobolus communities. Rhizome-derived S. pumilus had greater survival and grew faster than seed-derived plants. Plants inoculated with propagated AMF consistently outperformed both sterile and native sediment controls in terms of plant survival and growth. Use of rhizome-derived Sporobolus inoculated with propagated Funneliformis geosporum showed the most promise in producing successful plant populations for salt marsh restoration. This may be due to plant life stage and improved plant nutrient status, allowing rhizome-derived plants to grow more quickly than seed-derived plants. Using these plants in future large-scale restoration may increase re-establishment of salt marsh ecosystems.

A Lagrangian-to-Eulerian Metric to Identify Estuarine Pelagic Habitats

Estuaries are among the world’s most productive ecosystems, but recent natural and anthropogenic changes have stressed these ecosystems. Tools to assess estuarine pelagic habitats are important to support and maintain healthy ecosystem function. In this work, we demonstrate that estuarine pelagic habitats can be identified by a simple ratio, termed the LE ratio, that takes into account the tidal excursion along a channel (a Lagrangian length scale) and the distance along that channel (an Eulerian length scale). To develop and assess this concept, numerical simulations of the 1D advection–dispersion equation of a conservative tracer and tidal excursion estimates based on data were used to formulize a conceptual model and to define exchange zones within a tidal channel. This conceptual model was then used to predict the extent of pelagic habitats in a terminal channel network in the Sacramento–San Joaquin Delta. Exchange zones mapped onto these channels were found to be in good agreement with independent estimates of residence time. Sensitivity analyses of the numerical model suggest that productive pelagic habitats can be expanded by a factor of 2 by either increasing dispersion or increasing spring–neap variability in mean tidal velocity. Such changes can also enhance flushing in upper channel reaches. These findings are relevant for tidal marsh restoration projects that aim to expand beneficial aquatic habitats by varying exchange or residence time over the spring–neap cycle, because this variability may interact synergistically with varying rates of phytoplankton growth due to spatiotemporal changes in environmental conditions.

New mapping metrics to test functional response of food webs to coastal restoration

The recovery of natural energy flow in food webs is an important indication that a restoration project has been a success, yet is typically considered a challenging component of post-restoration monitoring protocols. Advancements in remote sensing and SIA offer unique opportunities to build and test new metrics that more easily measure food web recovery following restoration. Here, we combine fine-scale remotely sensed data with SIA mixing model outputs to demonstrate a method for creating energetic landscape maps, or E-scapes, that assess the energetic quality of a multi-year marsh restoration effort for white shrimp (Litopenaeus setiferus). These maps explicitly link spatial features with the resources used by a consumer to allow managers to visualize and quantify how a restored landscape is producing energy for a target species. Our results support many known restoration paradigms concerning the relationship between habitat cover and use, highlighting its potential usefulness for monitoring purposes. With further testing and development, these products could also be used in the design of restoration projects and increase their potential for success.

Suspended-sediment Flux in the San Francisco Estuary; Part II: the Impact of the 2013–2016 California Drought and Controls on Sediment Flux

Recent modeling has demonstrated that sediment supply is one of the primary environmental variables that will determine the sustainability of San Francisco Estuary tidal marshes over the next century as sea level rises. Therefore, understanding the environmental controls on sediment flux within the San Francisco Estuary is crucial for optimal planning and management of tidal marsh restoration. Herein, we present suspended-sediment flux estimates from water year (WY) 2009–2016 from the San Francisco Estuary to investigate the environmental controls and impact of the record 2013–2016 California drought. During the recent drought, sediment flux into Lower South Bay, the southernmost subembayment of the San Francisco Estuary, increased by 345% from 114 kt/year from WY 2009 to 2011 to 508 kt/year from WY 2014 to 2016, while local tributary sediment flux declined from 209 to 51 kt/year. Total annual sediment flux from WY 2009 to 2011 and 2014 to 2016 can be predicted by total annual freshwater inflow from the Sacramento-San Joaquin Delta (R2 = 0.83, p < 0.01), the primary source of freshwater input into the San Francisco Estuary. The volume of freshwater inflow from the Sacramento-San Joaquin Delta is hypothesized to affect shoal-to-channel density gradients that affect sediment flux from broad, typically more saline and turbid shoals, to the main tidal-channel seaward of Lower South Bay. During the drought, freshwater inflow from the Sacramento-San Joaquin Delta decreased, and replacement of typically more saline shoal water was reduced. As a result, landward-increasing cross-channel density gradients enhanced shoal-to-channel advective flux that increased sediment available for tidal dispersion and drove an increase in net-landward sediment flux into Lower South Bay.

Potential hazards of metal-contaminated soils in an estuarine impoundment

A recreational impoundment was constructed in the mid-nineteenth century on the mudflats reclaimed from the Plym Estuary (SW England) following salt marsh removal and infilling with waste soils from local catchments. Restoration of the salt marsh was attempted about 25 years ago when a regulated tidal exchange system was installed in the embankment separating the impoundment from the estuary. Currently, the embankment is disintegrating with the potential loss of the impounded soils, of unknown composition, to the estuary. Cores were obtained from the impoundment and the adjoining estuary, sectioned, dried and analysed. The geochronology of the soils, and estuarine sediments, was established using gamma-ray spectroscopy to determine the activities of fallout radionuclides, 137Cs and 210Pb. The concentrations of As, Co, Cr Cu, Fe, Mn, Ni, Pb, Rb, Sn, W and Zn in the core sections were determined by quantitative X-ray fluorescence spectrometry. Below a shallow surface layer (> 5 cm and post-1963), metal concentrations were high with several exceeding soil quality indices, and enrichment factors (EFs) were elevated, in the sequence Sn > W≈As > Cu > Pb. Estimates of the total masses of particulate Sn, Pb, As and Cu available for down-estuary migration were significant. Given the ecotoxicological implications resulting from a loss of metal-contaminated soils into the estuary, a strategy for the future management of the impoundment is required. The conditions at this site are compared with ageing estuarine impoundments at other locations, where polluted sediments, or soils, could be vulnerable to release.

Effects of barrier island salt marsh restoration on marsh bird occurrence in the northern Gulf of Mexico

In the northern Gulf of Mexico, salt marshes are threatened by sea level rise, erosion, and loss of protective barrier islands. These barrier islands provide critical habitat for wildlife, including globally significant populations of marsh and shorebirds. We investigated salt marsh restoration on two Louisiana barrier islands using presence of eight marsh bird species as an index to evaluate restoration success. Land loss was extensive for both islands prior to restoration, with submerged marsh restored by backfilling sediment into the marsh platform. Restoration methods were similar between the two islands, although Raccoon Island was built to a higher elevation (1.1 m) than Whiskey Island (0.8 m). Avian presence was estimated via passive acoustic monitoring and point counts. To evaluate restoration success, we modeled influence of habitat covariates on index species presence in restored and reference (intact) sites over three breeding seasons and modeled occupancy for six species. On Whiskey Island, index richness was higher in restored sites. Marsh specialists Seaside Sparrows (Ammospiza maritima) and Least Bitterns (Ixobrychus exilis) had higher occupancy in restored areas on Whiskey, while generalist species showed no response to site. These results are likely due to a strong association between habitat and vegetation type, with restored sites dominated by Spartina alterniflora and reference sites by Avicennia germinans. On Raccoon Island, species richness was low across all sites. Our results suggest that restoration efforts were successful in creating salt marsh habitat on Whiskey but not Raccoon as of the time of our study.

Dredging Impacts on Soil Properties of the Kankakee River System 150 Years after Perturbation

Freshwater marshes provide ecosystem services such as improving water quality by storing water and filtering nutrients from upland runoff, minimizing erosion and flooding by reducing stream and river velocity and peak flows, and carbon sequestration by storing organic matter for long extended periods of time. These ecosystem services have increased interest in the protection and restoration of marshes and soil properties and are an important consideration for successful restoration. This study was conducted in Indiana, USA, within the historical extent of the Grand Kankakee Marsh that once encompassed 202,343 ha, until the dredging of the Kankakee River from 1852 to 1917 to convert the marsh to cropland. Current (in 2019) soil properties (organic matter mass and concentration, bulk density, moisture content, and carbonate concentration) were compared between (1) marshes that were dredged and presently in other land-use categories such as cropland and forests, and (2) remnant marshes that were not impacted by dredging. On average, organic matter mass and concentration were not significantly different between dredged areas and marshes (p > 0.05). However, marshes tended to have lower bulk densities, greater moisture contents, and greater carbonate concentrations compared to dredged areas. The soil properties of remnant marshes in this study can be used to evaluate the success of marsh restoration efforts in regions with similar soils, climate, and land-use history.

Observations of wave attenuation, scour, and subsurface pore pressures acrossbthree marsh restoration sill structures on a sandy bed

With rising sea levels and more frequent exposure to extreme storms, coastlines worldwide are vulnerable to increased erosion and loss of natural marsh lands. In an effort to lessen these impacts, there is a growing practice of adapting hard or “gray” coastline protection techniques to more nature-based features that promote habitat and ecosystem health. Living shoreline marsh restorations utilize natural and naturebased materials to protect marsh shores from erosion while also allowing intertidal flushing to promote the health and diversity of the marsh. Our study investigates three types of living shoreline sill designs exposed to average and storm-energy wave conditions at varying water levels. The sills were designed to mimic constructed sills in practice (rock, oyster shell, tree root wads), but more generally vary in structure porosity and material dissipation potential. Large-scale laboratory experiments were conducted in the large wave flume at the O.H. Hinsdale Wave Research Laboratory. Wave transmission and reflection are used to demonstrate wave attenuation capability of each sill structure. Scour of the sill, bedload sediment transport rates on the seaward and shoreward sides of the sill, and sediment pore-water vertical hydraulic gradients were used to demonstrate the potential for sediment transport and liquefaction. Results will contribute to understanding the effect of sill material porosity and mass on structure stability, and the effectiveness of using green living shoreline sill structures in the continued effort to establish design criteria for living shoreline implementation.

Sediment infilling and geomorphological change of a mud-capped Raccoon Island dredge pit near Ship Shoal of Louisiana shelf

To restore degraded barrier shorelines of the Mississippi River Delta of coastal Louisiana, sand is dredged from high-quality borrow areas on the adjacent continental shelf. This dredging process generally creates a topographic low that facilitates the rapid capture of sediments. Our understanding of sedimentary processes and influences on seabed morphologic evolution is still limited. In this study, Raccoon Island dredge pit in a paleo-river channel on the Louisiana shelf was studied via multiple bathymetric surveys. Physical parameters include pit geometry and topographic change from post-dredging, and infilling sediment sources were analyzed. Raccoon Island pit was 100% filled up less than six years after dredging. The average infilling rate in the Raccoon Island pit was 1.10 m/year from 2013 to 2018. During the surveying period, the pit wall slope decreased by 6.8° within two years. The sediment infilling process in the Raccoon Island pit was likely under the combined influence of topography, wind-driven currents, storm waves, and the dynamic Atchafalaya River dispersal system. The Atchafalaya River reached high discharge in 2016, which likely contributed to a surprisingly high sediment infilling rate at Raccoon Island pit between 2015 and 2018. Raccoon Island pit is in a mixed texture environment in which the sandy pit was fully filled with mud. Mud is useful for marsh restoration but is not considered a quality resource for barrier island or beach restoration. Thus, the Raccoon Island pit is not regarded as a renewable resource for future barrier island restoration.

Plant biomass and rates of carbon dioxide uptake are enhanced by successful restoration of tidal connectivity in salt marshes

Salt marshes, due to their capability to bury soil carbon (C), are potentially important regional C sinks. Efforts to restore tidal flow to former salt marshes have increased in recent decades in New England (USA), as well as in some other parts of the world. In this study, we investigated plant biomass and carbon dioxide (CO2) fluxes at four sites where restoration of tidal flow occurred five to ten years prior to the study. Site elevation, aboveground biomass, CO2 flux, and porewater chemistry were measured in 2015 and 2016 in both restored marshes and adjacent marshes where tidal flow had never been restricted. We found that the elevation in restored marsh sites was 2–16 cm lower than their natural references. Restored marshes where porewater chemistry was similar to the natural reference had greater plant aboveground biomass, gross ecosystem production, ecosystem respiration, as well as net ecosystem CO2 exchange (NEE) than the natural reference, even though they had the same plant species. We also compared respiration rates in aboveground biomass (AR) and soil (BR) during July 2016, and found that restored marshes had higher AR and BR fluxes than natural references. Our findings indicated that well-restored salt marshes can result in greater plant biomass and NEP, which has the potential to enhance rates of C sequestration at 10-yrs post restoration. Those differences were likely due to lower elevation and greater flooding frequency in the recently restored marshes than the natural marsh. The inverse relationship between elevation and productivity further suggests that, where sea-level rise rate does not surpass the threshold of plant survival, the restoration of these salt marshes may lead to enhanced organic and mineral sedimentation, extending marsh survival under increased sea level, and recouping carbon stocks that were lost during decades of tidal restriction.

Quantifying the Benefits of Estuarine Habitat Restoration in the Gulf of Mexico: an Introduction to the Theme Section

This collection of papers provides insights into methods and data currently available to quantify the benefits associated with estuarine habitat restoration projects in the northern Gulf of Mexico, USA, with potential applicability to other coastal systems. Extensive habitat restoration is expected to occur in the northern Gulf of Mexico region over the next several decades through funding associated with the 2010 Deepwater Horizon oil spill. Papers in this section examine the development of vegetation, soil properties, invertebrate fauna, and nekton communities in restored coastal marshes and provide a conceptual framework for applying these findings to quantify the benefits associated with compensatory marsh restoration. Extensive meta-analysis of existing data for Gulf of Mexico coastal habitats further confirms that structured habitats such as marsh, submerged aquatic vegetation, and oyster reefs support greater nekton densities than nonvegetated bottom habitat, with oyster reefs supporting different species assemblages than marsh and submerged aquatic vegetation. Other papers demonstrate that while vegetation cover can establish rapidly within the first 5 years of restoration, belowground parameters such as root biomass and soil organic matter remain 44% to 92% lower at restored marshes than reference marshes 15 years after restoration. On average, amphipod and nekton densities are also not fully restored until at least 20 and 13 years following restoration, respectively. Additional papers present methods to estimate the benefits associated with marsh restoration projects, nekton productivity associated with coastal and estuarine habitats, and the benefits associated with the removal of derelict crab traps in Gulf of Mexico estuaries.

“We Won’t Survive in a City. The Marshes are Our Life”: An Analysis of Ecologically Induced Genocide in the Iraqi Marshes

ABSTRACT The Iraqi marshes were drained by Saddam Hussein in the 1990s as part of a counterinsurgency campaign against the Marsh Arabs as a collective – an operation that has been analyzed previously as a case of ecocide and genocide. Providing an updated analysis of this case study, this article argues that present day upstream hydropower projects, oil extraction and conservation practice in the marshes are causing a continuing genocidal and ecocidal effect. This is because these activities are contributing to the continuing degradation of the marshes, causing them to be uninhabitable and resulting in the re-displacement and cultural alienation of those Marsh Arabs who had returned after the draining in the 1990s. The primary focus of this article is the intersection between neoliberal conservation and the process of ecologically induced genocide, with an exploration of how various partnerships between conservation NGOs and the oil extractive industry on marsh restoration projects have proved to be the newest contributor to the ecocide and ecologically induced genocide occurring there. The role of counterinsurgency and its interplay with conservation, ecocide and genocide will be explored, specifically the “soft” techniques of counterinsurgency which have been used to pacify and co-opt Marsh Arab communities. This article makes connections between the theories and concepts of cultural genocide, the genocide-ecocide nexus, social death, counterinsurgency, and neoliberal conservation, and upholds a nuanced understanding of what can be perceived as genocidal intent.

Where does the salt marsh start? Field-based evidence for the lack of a transitional area between a gradually sloping intertidal flat and salt marsh

Salt marshes are vegetated ecosystems between land and sea, hosting unique plant and animal communities, contributing to crucial habitats for birds and providing numerous other ecosystem services. They form a sustainable nature-based coastal protection, and its protective value increases with the width of the system. Salt marshes and their adjoining tidal flats are often studied separately. At present, there is a lack of studies that describe the features of these two systems in unison and in relation to each other. This study descriptively assesses an array of abiotic and biotic variables that potentially affect successful vegetation establishment. Unfavourable soil conditions may limit establishment as well as bioturbation of infauna. This is related to the marsh expansion potential and could aid in salt marsh restoration and marsh growth stimulation projects. In a naturally developing salt marsh, we sampled the elevation gradient from the tidal flat to the low marsh for benthic species composition, plant seed availability and abiotic variables. The abundance of benthos was highest landwards of the transition zone, in the pioneer zone. Distinct meiobenthic groups occurred in the different zones along the tidal flat to low marsh gradient, but macrobenthos was largely absent from the muddy soil. In the sparsely vegetated transition zone, the abundance of salt-marsh seeds was low, similar to the tidal flat. It suggests that, even though a seed source was in proximity, seed availability in spring was insufficient to achieve lateral marsh expansion. Clustering and nMDS analyses showed that an identifiable transition zone was lacking. The transition zone resembled the bare tidal flat in terms of its abiotic and biotic conditions. This was mainly driven by significant changes in soil oxygenation and seed availability.

Micro-Topography Manipulations Facilitate Suaeda Salsa Marsh Restoration along the Lateral Gradient of a Tidal Creek

Topographic heterogeneity provides a potential opportunity for seedling recruitment in the disturbance-dynamic ecosystem. Micro-topography manipulation is the typical way to imitate or recover the natural topographic heterogeneity for the degraded salt marsh restoration. However, it is still not clear how different micro-topographic structures work along the lateral gradient of a tidal creek. In this study, we performed three micro-topographic treatments, i.e., hollow topography, fine and coarse biotic grille structures, to restore the degraded Suaeda salsa wetlands. The results showed that the effectiveness of micro-topography restorations varied with structures and elevation levels. The hollow topography performed well in high marshes by relieving salinity stress and enhancing seeds retention. Moreover, in middle and low marshes, fine biotic grille structure improved the seeds retention and soil conditions better, including soil salinity and moisture, which were critical physico-chemical factors for Suaeda salsa biomass restoration according to redundancy analysis. In contrast, coarse biotic grille structure showed little significance on Suaeda salsa restoration. The findings of this work emphasized that seeds retention and post local soil conditions were significant aspects for salt marsh restoration. Meanwhile, it provided an alternative design for micro-topographic structures by native biotic materials in the complex and dynamic salt marshes.