Coastal wetlands, salt marshes and mangroves, fulfil important functions for biodiversity conservation and coastal protection, which are inextricably linked to interactions between hydrodynamics, sediment transport and ecology the so-called eco-geomorphological feedback. However, range expansion patterns of salt marshes and mangroves are changing due to both human influences and global change. Human driven introduction of salt marsh species for erosion mitigation starting in the last century e.g. (Europa and China) are influence natural mangrove habitats and its implications are still unfolding. Conversely, within the last decades, a climate change induced ubiquitous trend of mangrove encroachment on salt marshes has been observed globally in the mangrove-salt marsh transition zones, e.g. the southern USA, South America, Australia, New Zealand and South Africa. Here we present a novel eco-morphodynamic model able to predict species-species interactions, i.e. competition and facilitating, sediment transport on morphodynamics. The aim of our study is to predict competitive outcomes of mangrove-saltmarsh interactions resulting from the interaction of species-specific growth and stress tolerance, and additional natural and climatic factors. First results indicate the competitive outcome to be context dependent on the relative growth properties of the mangrove and salt marsh species in question. Thereby providing highly need to context to interpret implication on shifts in species ranges on morphodynamic wetland development.

Coastal cliff erosion affects communities worldwide. In England, cliffs make up approximately 54% of the coastline, a vast proportion of which is of weak to very weak rock resistance. Being able to adequately quantify rates and styles of retreat as well as relating these to their driving forces is key to making informed decisions on future coastal management strategies. Nationwide change analysis, spanning more than 20 years in places, was carried out by comparing the earliest and most recent LiDAR Digital Elevation Models (DEMs) using raster differencing in a GIS environment. Erosion rates over the cliff face were derived by excluding any bias caused by the presence of vegetation from the change analysis. Uncertainty of erosion rates is affected predominantly by the precision of the LiDAR sensors (typically ±15cm in elevation), and was derived at each location by comparison with a network of ground control points. Limitations of a DEM differencing approach are widely discussed in the literature, particularly in areas of high relief where overhanging and undercutting features may be present. Nonetheless, this large-scale assessment provides a consistent approach to estimate erosion rates and was used as a basis for the selection of sites at which more extensive topographic analysis was carried out in 3D, overcoming some of the limitations of a raster differencing approach. Sites were selected to capture the variability in intrinsic (e.g., geology, slope, aspect) and extrinsic (e.g., waves, tides, rainfall) drivers of retreat. An open-source Python workflow was developed by integrating the M3C2 plugin for Cloud Compare to calculate distances between subsequent timesteps of point cloud data, after which the volume of meshed erosion clusters was computed. As a result, an inventory of cliff face erosion scars was compiled, with attributes relating to scar shape, area, volume and elevation relative to cliff top height. A comparison of the two approaches for calculating erosion rates highlighted the ability of the 3D workflow to capture cliff failure in greater detail and with higher accuracy, at the expense of increased computational costs. Findings also indicate spatio-temporal variations in erosion patterns which are related not only to the intrinsic nature of each site, but also to its climatology. It is expected that the broad spatial scale of this research will provide some insights into the main styles and drivers of retreat affecting specific stretches of coastline in England.

Understanding the factors that drive coastline evolution is complex, yet essential for managing coastal environments. For Guyana, Suriname and French Guiana, coastline changes can shed light on the relative contributions of alongshore migrating subtidal mudbanks compared to human or climate induced changes. This study addresses the impact of mudbank morphometrics on the Guianas' coastline morphology from 1985 to 2023, using Landsat’s optical earth observation data. We found that during mudbank phases, the coastline advanced significantly, averaging 4 to 40 m/yr, while in their absence, retreat averaged 16 to 21 m/yr. Relative low migration rates of 1 - 1.2 km/yr combined with the characteristics of mudbanks, some extending up to 8km offshore, explained part (R2 = 0.2, P <0.05) of the coastline's progradation and retrogradation. This computed frequency of mudbank occurrence, linking the position and shape of a mudbank, thus proves to be a key factor controlling the number of years a coastal section is protected and accretion is facilitated. Understanding these dynamics is crucial for future coastal protection efforts and ecosystem restoration. Our findings also highlight where coastlines do not benefit from mudbank-induced accretion, possibly due to irreversible changes in the system, emphasizing the need for tailored coastal management strategies.

Guo al., 2021)determined by the processes driving the change, the size of the system, and the magnitude of such 61 interventions. Nevertheless, distinctive effects must consider the unique patterns of each specific site. 62The collection also highlights the interest in addressing approaches aimed at recovering and 63 increasing the environmental resilience of these valuable ecosystems. 64Authors Contribution 65 JCR: Writing-original draft, Writing-review and editing. AN: Writing-review and editing. BvM: 66Writing-review and editing. JDRA Writing-review and editing. MB: Writing-review and editing. 67The authors declare that the Editorial Note was conducted in the absence of any commercial or 69 financial relationships that could be construed as a potential conflict of interest. 70The author(s) declare that financial support was not received for the authorship, and/or publication of 72 this Editorial Note. 73As guest editors, we highly acknowledge all authors and reviewers who contributed to this Research 75 Topic. Their effort, commitment, and innovation ensured the high quality of the accepted papers. We 76 incredibly grateful to the Editor in Chief of the journal and Frontiers' specialist team for their 77 and 78 6

AbstractMangrove‐saltmarsh ecotones are experiencing rapid alterations due to climate change and human activities, however, the ecological and morphological implications of these shifts remain largely unknown. This study systematically explores how interspecific interactions and herbivory influence the dominant wetland species, as well as the resultant morphological evolution and landscape configuration. To achieve this, we develop a new eco‐morphodynamic model that integrates hydrodynamics, sediment transport, bed‐level change, and vegetation dynamics. The novelty of the current model lies in newly incorporated modules to simulate biotic interactions between mangroves and saltmarshes, enabling exploration of eco‐morphodynamic feedback in mangrove‐saltmarsh ecotones in response to tidal flows and species interactions. Our results show that vertical growth rates of coexisting vegetation species are dominant factors in determining wetland dominance. When mangroves and saltmarshes exhibit comparable growth rates, mangroves typically become the dominant wetland species. Conversely, if mangroves grow more slowly than saltmarshes, they are unable to outcompete saltmarshes. Additionally, herbivory can fundamentally alter wetland dominance depending on herbivore food preferences. Our simulations further underline that saltmarsh‐dominated wetlands develop channel networks more extensively and rapidly than mangrove‐dominated systems. This pattern is also observed during species invasions, with invading saltmarshes extending channel networks, while invading mangroves inhibit ongoing network expansion. This study highlights the pivotal roles of relative growth properties and herbivory in driving ecotone development in respect to wetland dominance and channel network development at the intertidal scale.

Mangroves are under immense anthropogenic pressures globally which are further exacerbated by their accessibility to humans. To minimize human access hence pressures to the ecosystem, establishment of protected areas is often employed. However, the ecological effectiveness of protected areas, which influences their legal durability, is rarely assessed beyond curbing deforestation. Furthermore, little is known about whether protection could still provide a positive ecological impact if the sites are easily accessible, i.e., adjacent to urban areas, near roads, small in area and/or fragmented. To improve our understanding thereon, this study compares anthropogenic disturbance severity, forest structures and ecosystem carbon (C) stocks of protected and unprotected mangroves near Barranquilla, Colombia 's largest coastal city. The outcomes suggest that accessible, yet protected mangrove has a mean disturbance index of 5.3, lower than unprotected mangrove (mean 11). Protected mangrove also has higher mean (+/- SD) tree basal area (26.5 +/- 15.6 m 2 ha -1 ), mean densities of tree, sapling and seedling (899 +/- 398, 5155 +/- 7860, and 68,837 +/- 73,899 individual ha -1 , respectively) and biomass C stock (mean 89.5 +/- 39 Mg ha -1 ) than those of accessible unprotected mangrove (mean basal area 19.3 +/- 5 m 2 ha -1 ; mean tree, sapling and seedling densities 823 +/- 215, 749 +/- 94, and 33,727 +/- 44,882 individual ha -1 , respectively; mean biomass C stock 60.2 +/- 14.5 Mg ha -1 ). Results suggest that the current sediment C stocks, that is higher in unprotected than protected mangroves (396.8 +/- 552.6 and 142.4 +/- 205.7 Mg ha -1 , respectively), are not primarily driven by conservation status, but by long-term processes that likely pre-date the protected status designation. Mangrove protection, however, could help maintain carbon stocks in soils and biomass and the potential for further soil carbon sequestration, and thus are pivotal in determining future trajectories of mangrove climate mitigation potential. This study shows that even imperfect protection offers ecological benefits to highly accessible ecosystems. Hence, focus should be placed on optimizing these benefits and minimizing their vulnerability to downgrading, downsizing and degazettement.

Worldwide, many tidal basins associated with barrier coasts have infilled over the past millennia due to the combination of sediment supply, wave‐tidal sediment transport, and eco‐engineering effects of vegetation. However, the biogeomorphological interactions between saltmarsh and the morphodynamics of an entire coastal barrier system are poorly understood, especially under sea level rise (SLR). Here, we study the evolution of a barrier coast for combinations of mud availability, presence of vegetation, and SLR. We developed a novel biogeomorphological model of an idealized barrier coast enclosing a tidal basin with sandy‐clayey sediments that was subjected to tides and waves for a century. The morphodynamic Delft3D model was coupled to a vegetation code which accounts for the dynamics of marsh‐type vegetation. Initially, vegetation contributed to reducing the tidal prism while sediment was imported. However, with SLR this trend was reversed and the tidal basins started to export sediment for vegetated runs after about 50–60 years while the unvegetated scenarios continued to infill in pace with the SLR. The sediment export was caused by cascading biomorphodynamic feedback effects triggered by vegetation which modified channel and shoal dynamics. Even under higher mud supply, the SLR resulted in vegetation collapse. The hypsometries, similar to natural systems, showed that vegetated systems converge to an alternative stable state condition. We conclude that the long‐term resilience of the tidal basin associated with sediment infilling under SLR can be reduced by cascading large‐scale effects of vegetation on the morphodynamics of barrier coasts.

Changes in upstream land-use have significantly transformed downstream coastal ecosystems around the globe. Restoration of coastal ecosystems often focuses on local-scale processes, thereby overlooking landscape-scale interactions that can ultimately determine restoration outcomes. Here we use an idealized bio-morphodynamic model, based on estuaries in New Zealand, to investigate the effects of both increased sediment inputs caused by upstream deforestation following European settlement and mangrove removal on estuarine morphology. Our results show that coastal mangrove removal initiatives, guided by knowledge on local-scale bio-morphodynamic feedbacks, cannot mitigate estuarine mud-infilling and restore antecedent sandy ecosystems. Unexpectedly, removal of mangroves enhances estuary-scale sediment trapping due to altered sedimentation patterns. Only reductions in upstream sediment supply can limit estuarine muddification. Our study demonstrates that bio-morphodynamic feedbacks can have contrasting effects at local and estuary scales. Consequently, human interventions like vegetation removal can lead to counterintuitive responses in estuarine landscape behavior that impede restoration efforts, highlighting that more holistic management approaches are needed.

Mangrove forests are valuable coastal ecosystems that have been shown to persist on muddy intertidal flats through bio-morphodynamic feedbacks. However, the role of coastal conditions on mangrove behavior remains uncertain. This study conducts numerical experiments to systematically explore the effects of tidal range, small wind waves, sediment supply and coastal slope on mangrove development under sea-level rise (SLR). Our results show that mangroves in micro-tidal conditions are more vulnerable because of the gentler coastal equilibrium slope and the limited ability to capture sediment, which leads to substantial mangrove landward displacement even under slow SLR. Macro-tidal conditions with large sediment supply promote accretion along the profile and platform formation, reducing mangrove vulnerability for slow and medium SLR, but still cause rapid mangrove retreat under fast SLR. Small wind waves promote sediment accretion, and exert an extra bed shear stress that confines the mangrove forest to higher elevations with more favorable inundation regimes, offsetting SLR impacts. These processes also have important implications for the development of new landward habitats under SLR. In particular, our experiments show that landward habitat can be created even with limited sediment supply and thus without complete infilling of the available accommodation space. Nevertheless, new accommodation space may be filled over time with sediment originating from erosion of the lower coastal profile. Consistent with field data, model simulations indicate that sediment accretion within the forest can accelerate under SLR, but the timing and magnitude of accretion depend non-linearly on coastal conditions and distance from the mangrove seaward edge.

For the development of climate-resilient coastal management strategies, which focus on challenges in the decades to come, it is critical to incorporate spatial and temporal variability of coastline changes. This is particularly true for the mud-dominated coast-line of Suriname, part of the Guianas, where migrating subtidal mudbanks cause a cyclic instability of erosion and accretion of the coast that can be directly related to interbank and bank phases. The coastline hosts extensive mangrove forests, providing valuable ecosystem services to local communities. Recent studies on mudbank dynamics in Suriname predominantly focused on large-scale trends without accounting for local variability, or on local changes considering the dynamics of a single mudbank over relatively short time scales. Here we use a remote sensing approach, with sufficient spatial and temporal resolution and full spatial and temporal coverage, to quantify the influence of mudbank migration on spatiotemporal coastline dynamics along the entire coast of Suriname. We show that migration of six to eight subtidal mudbanks in front of the Suriname coast has a strong imprint on local coastline dynamics between 1986 and 2020, with an average 32 m/yr accretion during mudbank presence and 4 m/yr retreat of the coastline during mudbank absence. Yet, coastal erosion can still occur when mudbanks are present and coastal aggregation may happen in the absence of mudbanks, exemplifying local variability and thus suggesting the importance of other drivers of coastline changes. The novel remote sensing workflow allowed us to analyse local spatial and temporal variations in the magnitude and timing of expanding and retreating trajectories. Our results demonstrate that it is essential that all coastal behaviours, including changes that cannot be explained by the migration of mudbanks, are included in multi-decadal management frameworks that try to explain current variability, and predict future coastline changes in Suriname.

Coastal wetlands fulfil important functions for biodiversity conservation and coastal protection, which are inextricably linked to typical morphological features like tidal channels. Channel network configurations in turn are shaped by bio-geomorphological feedbacks between vegetation, hydrodynamics and sediment transport. This study investigates the impact of two starkly different recruitment strategies between mangroves (fast/homogenous) and salt marshes (slow/patchy) on channel network properties. We first compare channel networks found in salt marshes and mangroves around the world and then demonstrate how observed channel patterns can be explained by vegetation establishment strategies using controlled experimental conditions. We find that salt marshes are dissected by more extensive channel networks and have shorter over-marsh flow paths than mangrove systems, while their branching patterns remain similar. This finding is supported by our laboratory experiments, which reveal that different recruitment strategies of mangroves and salt marshes hamper or facilitate channel development, respectively. Insights of our study are crucial to understand wetland resilience with rising sea-levels especially under climate-driven ecotone shifts.

Coastal wetlands provide a livelihood for local communities and simultaneously provide services that include coastal protection, enhanced carbon storage and habitats provision for both terrestrial-and marine life.Yet, the development of climate resilient management strategies that need to account for changes that might occur in the coming decades is challenging due to the variable response of coastal ecosystems.This is because coastal ecosystems, including mangroves, wetlands and tidal flats, are

Mapping of subtidal banks in mud-dominated coastal systems is crucial as they influence not only shoreline and ecosystem dynamics but also economic activities and livelihoods of local communities. Due to associated spatiotemporal variations in suspended particulate matter concentrations, subtidal mudbanks are often confined by diffuse and rapidly changing boundaries. To avoid inaccurate representations of these mudbanks in remote sensing images, it is necessary to unmix distinctive reflectance signals into representative landcover fractions. Yet, extracting mud fractions, in order to characterize such diffuse boundaries, is challenging because of the spectral similarity between subtidal- and intertidal features. Here we show that an unsupervised decision tree, used to derive spatially explicit and spectrally coherent image endmembers, facilitates robust linear spectral unmixing on an image-to-image basis, enabling the separation of these coastal features. We found that resulting abundance maps represent cross-shore gradients of vegetation, water and mud fractions present at the coast of Suriname. Furthermore, we confirmed that it is possible to separate land, water and an initial estimate of intertidal zones on individual images. Thus, spectral signatures of end-member candidates, determined from relevant index histograms within these initial estimates, are consistent. These results demonstrate that spectral information from well-defined spatial neighbourhoods facilitates the detection of diffuse boundaries of mudbanks with a spectral unmixing approach.

Mangroves play an important role in protecting coasts against wave energy and storms. Mangrove ecosystems provide important habitats for fauna and flora and are an important carbon sink. Loss of mangroves forest may lead to enhanced coastal erosion. Mangroves are complex ecosystems and processes of settling and development are not fully understood. Characterizing the rates and patterns of mangrove gains and losses is needed to better understand the functioning of mangrove ecosystems, how mangrove dynamics are linked to coastal morphological behaviour and how human interference with the coastal system impacts mangroves. Here we present a study of the mangrove ecosystems at the Suriname coast, which are relatively pristine and characterized by strong dynamics due to migrating mudbanks along the coast. Satellite images between 2000 and 2018, available in the historic satellite image archives, were analysed using the LandTrendr (Landsat-based detection of trends in disturbance and recovery) algorithm to identify locations of mangrove erosion, mangrove colonization, surface areas of change and patterns of settlement, as indicated by (sudden) changes in NDVI. The algorithm requires careful setting of various parameters for successful detection of (abrupt) temporal changes in mangrove coverage. The algorithm was evaluated on its robustness using various parameter settings. Results show the value of the timeseries of Landsat imagery to detect locations of coastal erosion of up to 50 m/yr and accretion where loss or settlement of mangroves is prevailing between 2000 and 2018. Locally differences are very large. An overall westward mangrove progression along the coast is apparent from the images and probably linked to mud bank migration. Various patterns of mangrove colonization and development such as arc-, zonaland patcharrangements were identified, although at some locations the Landsat resolution of 30 m is somewhat coarse to allow detailed analysis. The success and robustness of the LandTrendr algorithm are controlled by NDVI threshold values, number of allowed breakpoints in the timeseries and fitting parameters. The presented method requires further testing and evaluation but is a promising tool for semi-automatic detection of coastal mangrove erosion and colonization that can be applied to other mangrove ecosystems in the world. The satellite timeseries analyses generate valuable information on coastal dynamics, which is helpful to identify coastal areas prone to erosion and mangrove retreat and provide as such a valuable tool for coastal management and protection.

In coastal systems occupied by large clusters of pond aquaculture farms, hydro-sedimentary processes may be impacted by the combination of water management strategies that are individually performed by each cultivation unit. In this study, a numerical model was used to evaluate 100-year morphological alterations in two different idealized coastal lagoons surrounded by shrimp ponds. One is broadly based on the Guaraíras Lagoon System (RN, Brazil) where shrimp farming has developed since 1924, and the other is highly simplified to systematically investigate pond aquaculture impacts. Information obtained through numerical simulations (e.g., hypsometry changes, evolution of morphological parameters, balance of sediment volumes, bed level changes, and residual bed shear stress variations) provided coastal impact assessments for a wide variety of aquaculture occupation scenarios. Key findings include (i) water exchange operations performed by aquaculture farms are capable of modifying the morphological equilibrium state of a coastal lagoon system, especially if carried out synchronously to the local tidal oscillation; (ii) water intake operations regularly performed by pond aquaculture activity increase sediment import to the system; (iii) depth and configuration of tidal channels are modified when pond aquaculture is present. The modeling approach and analyses presented here can be extended to other systems that are under the influence of shrimp farming activity and be adopted to support novel regulations for the conservation of coastal habitats and to contribute to the sustainable development of pond aquaculture in the coastal zone.

Mangrove forests are valuable ecosystems, but their extent and diversity are increasingly threatened by sea-level rise and anthropogenic pressures. Here we develop a bio-morphodynamic model that captures the interaction between multiple mangrove species and hydro-sedimentary processes across a dynamic coastal profile. Numerical experiments are conducted to elucidate the response of mangrove assemblages under a range of sea-level rise and sediment supply conditions, both in the absence and presence of anthropogenic barriers impeding inland migration. We find that mangrove coverage can increase despite sea-level rise if sediment supply is sufficient and landward accommodation space is available. Tidal barriers are mainly detrimental to mangrove coverage and result in species loss. Importantly, we show that bio-morphodynamic feedbacks can cause spatio-temporal variations in sediment delivery across the forest, leading to upper-forest sediment starvation and reduced deposition despite extended inundation. As such, bio-morphodynamic feedbacks can decouple accretion rates from inundation time, altering mangrove habitat conditions and causing mangrove diversity loss even when total forest coverage remains constant or is increasing. A further examination of bio-morphodynamic feedback strength reveals that vegetation-induced flow resistance linked to mangrove root density is a major factor steering the inundation-accretion decoupling and as such species distribution. Our findings have important implications for ecosystem vulnerability assessments, which should account for the interactions between bio-morphodynamics and mangrove diversity when evaluating the impacts of sea-level rise on species assemblages.

Understanding estuarine hydrodynamics and sediment dynamics is of key importance to provide the foundation for sound management of these coastal systems. Turbidity maxima, which are zones of elevated suspended sediment concentration (SSC), are of particular interest as they control biogeochemical cycling and affect the overall environmental quality of the estuary. These turbidity maxima, however, are complex dynamic features that respond to changes in forcing conditions. In this study we use a 3D numerical model to investigate the response of hydrosedimentary dynamics to variations in river inflow and sea level rise in the Gironde estuary, which is one of the largest estuarine systems in Europe. Yearly simulations and comparisons with satellite data and measurements of salinity and SSC show that the model reproduces variations in salinity intrusion and the migration of the turbidity maximum driven by seasonal fluctuations in river inflow. Numerical experiments indicate that the formation of this dynamic turbidity maximum is mainly driven by tidal asymmetry. Density gradients play a secondary role by maintaining the stability of the suspended sediment mass. The model also simulates the presence of a secondary turbidity maximum which is more stable, consistent with observations. Evaluation of the sediment budget shows that sediment export mainly occurs during spring tides and when river discharge is high. Simulations including sea level rise suggest that salinity levels in the middle estuary will increase and rising water levels cause tidal amplification, strengthening of tidal currents and enhanced SSC levels in the upper estuary. On the other hand, the locations of the salinity front and the turbidity maximum remain relatively stable under rising water levels. Overall, our simulations suggest that decadal changes in river inflow can potentially have a larger effect on turbidity maximum dynamics than sea level rise.

The aim of this study is to understand the tidal characteristics in the radial sand ridges area (South Yellow Sea, China) considering the most adverse metrological and hydrodynamic condition. Based on data analysis, at least 30% of the annual highest tidal levels in the South Yellow Sea are caused by the combination of storm surge and astronomical spring tides. Among the top 10 extreme high tidal levels, such combinational effects account for over 60%. A 2-D numerical model is applied to study distributions of the extreme high tidal levels influenced by typhoons with various tracks in the South Yellow Sea. Typhoon characteristics are classified into four categories: the front landing, the front leaving, the offshore moving and other types. As such, four different combinations with the same astronomical tide are examined. The front landing and the offshore moving tracks are of specific interest, as they lead to the most significant surge in coastal areas, especially at Jianggang and Liyashan. Temporal-spatial patterns of the extreme storm tides are presented to identify risks of coastal flooding in the radial sand ridges area.