Coastal Wetland Loss Research Articles

Impacts of Sea Level Rise on Danish Coastal Wetlands - a GIS-based Analysis.

Intergovernmental Panel on Climate Change (IPCC) scenarios run by an ensemble of models developed by the Coupled Model Intercomparison Project (CMIP) projects an average sea level rise (SLRs) of 0.6 to 1.2 m for the low and high emission scenarios (SSP1-1.9, SSP5-8.5), during the next century (IPCC 2021). The coastal zone will experience an increase in the flooding of terrestrial habitats and the depth of marine productive areas, with potential negative consequences for these ecosystems. The coast in Denmark is highly modified due to anthropogenic uses. Dikes, dams, and other coastal infrastructure are widespread, causing a coastal squeeze that prevents natural coastal development and inland migration of coastlines. We performed a national-scale analysis on the impacts of mean sea level rise (MSLR) in 2070 and 2120, and a 1 in 10-year storm surge water level (10SS) in 2120 MSLR for the Danish coast. Our study shows extensive permanent flooding of coastal habitats (~14%), whereas only 1.6% of urban areas will be flooded. Finally, very large agricultural areas (~191,000 ha) will be frequently flooded by 10SS if no extra protective measures are planned. With the present coastal protection structures, key habitats will be affected by permanent flooding or coastal squeeze while even larger extents will be subjected to intermittent marine flooding. About 45% (199 km2) of all Danish coastal wetlands will be permanently flooded by 2120, while areas occupied by forest, lakes and freshwater wetlands will be more frequently flooded by marine water. This study highlights the importance of including coastal habitats as dynamic elements in climate adaptation plans. Conservation and restoration of key habitats such as coastal wetlands should be prioritized in management plans. If Denmark does not change its current priorities, it may face the complete loss of coastal wetlands habitat in the 22nd century.

Dredged Canals, Wetland Loss, and Legacy

AbstractThe direct effects of converting coastal wetlands to open water by dredging them can be magnified by indirect effects. For example, dredged canals allow for recovery of mineral fluids 1000 s of m belowground which may induce geological subsidence or faulting; the dredged material deposited at the surface creates levees that redirect overland water flows. These indirect factors may stress wetland plants enough so that additional wetland habitat is converted to open water as a result of longer intervals of wetland soil waterlogging and drying, sulfide toxicity, less organic matter and sediment accumulation, and greater erosion. We quantified the indirect effects by demonstrating a robust dose–response relationship between coastal land loss and canal density in the Mississippi and Niger river deltas over 5 decades. Importantly, the ratio of land loss to canal area increases with time—a legacy effect. Surface impediments to water movements rather than belowground subsidence are the dominant causal factor. We also found that flood protection levees on the main river channel did not significantly magnify the effect of dredging on wetland loss. The cumulative effect of these direct and indirect consequences in coastal Louisiana is enormous and continuing, equaling many tens of billions dollars annually. Understanding these effects supports the rejection of a hypothesis that regional river channel flood protection levees or fluid withdrawal is of greater importance than the local changes in wetland hydrology. Wetland restoration/mitigation of dredging impacts on these two coasts can be implemented at a relatively low cost and quickly if this paradigm of the causes of coastal wetland losses is adopted.

Non-market value losses to coastal ecosystem services and wetlands from sea-level rise and storm surge, 2050 to 2100: The Kimberley Region, Western Australia

Accelerating climate change from the thermal expansion of oceans and losses from terrestrial glaciers and ice sheets causes sea level rise (SLR), damaging coastal ecosystems and generating non-market value losses. Using an innovative Artificial Intelligence (AI) projection method and 18 existing geographical SLR projections, we project future sea level rise and storm surge (SLR/S) for the 1600 km coastline of the Kimberley Region, Western Australia, a region with a larger surface area than Great Britain, Ireland, and Portugal combined and with a permanent population of 40,000 people of which more than 16,000 identify as Indigenous. Using our projected coastal area inundation from future SLR, we estimated the non-market value losses of the Kimberley's coastal ecosystem and wetlands with projected SLR/S to 2050 and 2100 for Representative Concentration Pathway (RCPs) 4.5 and 8.5. Average annual non-market losses from SLR/S in 2050 and 2100 in the Kimberley are large relative to the size of the regional economy and are estimated to range from A$2.7 to A$4.3 billion (2050) and A$8.1 to A$15.8 billion (2100), depending on the RCP and temperature pathway. Our findings highlight the need for adequately resourced community-based approaches to climate adaptation.

Spatial and temporal changes in shorebird habitats under different land use scenarios along the Yellow and Bohai Sea coasts in China

The effect of coastal wetland loss on shorebird habitat in recent years has been widely reported in previous studies. Various coastal wetland conservation and restoration measures have been implemented or will soon be implemented in China. The extent to which these measures will affect the area and structure of coastal wetland habitat in the future remains unclear. Here, we predicted changes in habitat area and structure for 39 common shorebird species along the coasts of the Yellow and Bohai Seas using a cellular automata–Markov (CA-Markov) land use scenario model and a maximum entropy species distribution model, along with terrain factors (slope, aspect, and digital evaluation model) and climate factors (temperature and precipitation) from the Data Centre for Resources and Environmental Sciences at the Chinese Academy of Sciences, land cover maps interpreted using the human–computer interactive method, and citizen science data of shorebird occurrences derived from eBird, Global Biodiversity Information Facility, and Bird Report. We found that shorebird habitat was most abundant along the coasts of Bohai Bay, Laizhou Bay, and Yancheng. The area of habitat decreased and became increasingly fragmented between 2000 and 2020 for more than half of the 39 species. Under the future business-as-usual scenario, the area of shorebird habitat decreased from 2020 to 2050, and the remaining habitat became increasingly fragmented. Under the ecological protection (EP) scenario, habitat loss was mitigated, and habitat connectivity was improved. The area of habitat was lower in 2050 under the EP scenario than in 2000 for most species, especially threatened species, suggesting that the area of habitat will not return to year-2000 levels under the EP scenario. These results emphasize the need to protect remaining shorebird habitats and implement ecological conservation measures to ensure the long-term preservation of coastal wetlands.

A framework to quantitatively assess the influence of land use and land cover on coastal wetland hydrological connectivity from a landscape resistance perspective

Land use and land cover (LULC) change is one of the dominant factors contributing to coastal wetland degradation and loss. Most studies focused on LULC changes or whether they influenced on ecosystems. However, few studies quantitatively assessed the impact of different LULCs on hydrological connectivity. This study aimed to understand how LULC affected hydrological connectivity in the coastal wetlands in the Yellow River Delta (YRD), China, from 1985 to 2020. A framework from a landscape resistance perspective was used to evaluate the LULC's influence. LULCs were converted into a series of resistance surfaces whose values represent the degree to which LULC facilitated or restricted hydrological connectivity. The LULC's influence was evaluated by parameterizing the resistance surfaces using observed hydrological connectivity. The results showed that human-related LULC had more influence on hydrological connectivity. The critical time of LULC's influence on hydrological connectivity was 1985–1990 and 2010–2015. The critical areas were Zone II, Zone I, and Zone VI. The LULCs of agriculture, industry, town/city, and river had the most significant impact on the hydrological connectivity of the YRD coastal wetland. The result could direct LULC planning to mitigate the negative effect on coastal wetlands and provide support for the environmental impact assessment of coastal development practices. This paper advances the study by assessing LULCs' impact on hydrological connectivity and providing a quantitative method. The framework of this study enriches the coastal wetland conservation theory and policy-making of coastal management.

Assessment and Prediction of Sea Level and Coastal Wetland Changes in Small Islands Using Remote Sensing and Artificial Intelligence

Pacific Island countries are vulnerable to the impacts of climate change, which include the risks of increased ocean temperatures, sea level rise and coastal wetland loss. The destruction of wetlands leads not only to a loss of carbon sequestration but also triggers the release of already sequestered carbon, in turn exacerbating global warming. These climate change effects are interrelated, and small island nations continuously need to develop adaptive and mitigative strategies to deal with them. However, accurate and reliable research is needed to know the extent of the climate change effects with future predictions. Hence, this study develops a new hybrid Convolutional Neural Network (CNN) Multi-Layer Bidirectional Long Short-Term Memory (BiLSTM) deep learning model with Multivariate Variational Mode Decomposition (MVMD) to predict the sea level for study sites in the Solomon Islands and Federated States of Micronesia (FSM). Three other artificial intelligence (AI) models (Random Forest (FR), multilinear regression (MLR) and multi-layer perceptron (MLP) are used to benchmark the CNN-BiLSTM model. In addition to this, remotely sensed satellite Landsat imagery data are also used to assess and predict coastal wetland changes using a Random Forest (RF) classification model in the two small Pacific Island states. The CNN-BiLSTM model was found to provide the most accurate predictions (with a correlation coefficient of >0.99), and similarly a high level of accuracy (>0.98) was achieved using a Random Forest (RF) model to detect wetlands in both study sites. The mean sea levels were found to have risen 6.0 ± 2.1 mm/year in the Solomon Islands and 7.2 ± 2.2 mm/year in the FSM over the past two decades. Coastal wetlands in general were found to have decreased in total area for both study sites. The Solomon Islands recorded a greater decline in coastal wetland between 2009 and 2022.

Top-predator recovery abates geomorphic decline of a coastal ecosystem.

The recovery of top predators is thought to have cascading effects on vegetated ecosystems and their geomorphology1,2, but the evidence for this remains correlational and intensely debated3,4. Here we combine observational and experimental data to reveal that recolonization of sea otters in a US estuary generates a trophic cascade that facilitates coastal wetland plant biomass and suppresses the erosion of marsh edges-a process that otherwise leads to the severe loss of habitats and ecosystem services5,6. Monitoring of the Elkhorn Slough estuary over several decades suggested top-down control in the system, because the erosion of saltmarsh edges has generally slowed with increasing seaotter abundance, despite the consistently increasing physical stress in the system (that is, nutrient loading, sea-level rise and tidal scour7-9). Predator-exclusion experiments in five marsh creeks revealed that sea otters suppress the abundance of burrowing crabs, a top-down effect that cascades to both increase marsh edge strength and reduce marsh erosion. Multi-creek surveys comparing marsh creeks pre- and post-sea otter colonization confirmed the presence of an interaction between the keystone sea otter, burrowing crabsand marsh creeks, demonstrating the spatial generality of predator control of ecosystem edge processes: densities of burrowing crabs and edge erosion have declined markedly in creeks that have high levels of seaotter recolonization. These results show that trophic downgrading could be a strong but underappreciated contributor to the loss of coastal wetlands, and suggest that restoring top predators can help to re-establish geomorphic stability.

Accelerating Elevation Gain Indicates Land Loss Associated with Erosion in Mississippi River Deltaic Plain Tidal Wetlands

In recent years, the Mississippi River Deltaic Plain (MRDP) has experienced the highest rates of wetland loss in the USA. Although the process of vertical drowning has been heavily studied in coastal wetlands, less is known about the relationship between elevation change and land loss in wetlands that are experiencing lateral erosion and the contribution of erosion to land loss in the MRDP. We quantified relationships of elevation change and land change in ten submerging tidal wetlands and found that, despite significant land loss, elevation trajectories in seven of the land loss study sites were positive. Furthermore, we observed an acceleration in elevation gain preceding the conversion from vegetated marsh to open water.To identify regional contributions of lateral erosion to land loss, we quantified the relationship of elevation change and land change in 159 tidal marsh sites in the MRDP. Approximately half the sites were persistently losing land, and 82% of these sites were vulnerable to erosion, identifying erosion as a dominant mechanism of coastal wetland loss in this region. Notably, the sites that were vulnerable to erosion were experiencing land loss while also gaining elevation, and sites with the highest land loss exhibited accelerating elevation gain. Together, these data illustrate that (1) erosion is a dominant mechanism of wetland loss in the MRDP, (2) accelerated elevation gain is an indicator of erosion, and (3) consideration of elevation change trajectories within the context of land change is critical for providing accurate coastal wetland vulnerability assessments.

Shallow-subsidence vulnerability in the city of New Orleans, southern USA

AbstractLand subsidence in the city of New Orleans (USA) and its surroundings increases flood risk, and may cause damage to buildings and infrastructure and loss of protective coastal wetlands. To make New Orleans more resilient to future flooding, a new approach for groundwater and subsidence management is needed. As a first step in developing such an approach, high-quality and high-resolution subsurface and groundwater information was collected and synthesized to better understand and quantify shallow land subsidence in New Orleans. Based on the collected field data, it was found that especially the low-lying areas north and south of the Metairie-Gentilly (MG) Ridge are most vulnerable to further subsidence; north of the MG Ridge, subsidence is mainly caused by peat oxidation and south of the MG Ridge mainly by peat compaction. At present, peat has compacted ~31% on average, with a range of 9–62%, leaving significant potential for further subsidence due to peat compaction. Phreatic groundwater levels drop to ~150 cm below surface levels during dry periods and increase to ~50 cm below surface during wet periods, on average. Present phreatic groundwater levels are mostly controlled by leaking subsurface pipes. Shallow groundwater in the northern part of New Orleans is threatened by salinization resulting from a reversal of groundwater flow following past subsidence, which may increase in the future due to sea-level rise and continued subsidence. The hydrogeologic information provided here is needed to effectively design tailor-made measures to limit urban flooding and continued subsidence in the city of New Orleans.

Kentish Plover (Charadrius alexandrinus) and Little Tern (Sternula albifrons) prefer shells for nesting: A field experiment

Shorebird populations are declining worldwide, mainly due to human disturbances and loss of coastal wetlands. However, supratidal habitats as saltpans could play a role in buffering human impact. Saltpans have shown to be important as feeding or breeding sites of some shorebird species. A potential conservation strategy to increase shorebird populations in saltpans is to manipulate the cues that birds use to select optimal breeding habitat. Here it is hypothesized that shorebirds are attracted to bivalve shells due to the advantages they offer. Following this hypothesis, we supplemented a restored saltpan in 2019 and 2021 with bivalve shells, expecting an increase in the number of breeding birds’ nests. More than 75% of Kentish Plover (Charadrius alexandrinus) and Little Tern (Sternula albifrons) nests were found in patches with shells in both years. The best model for both species indicates that the presence of shells is the factor that most correlates with the location of nests. The probability of choosing one place over another to settle their nest increases in areas with an abundance of shells, double in the case of the Kentish Plover and triple in the case of the Little Tern. The result of this study may constitute a valuable tool for attracting birds to restored saltpans and could contribute to the success of expensive restoration projects where time is usually a constraint.

Will They Stay or Will They Go — Understanding South Atlantic Coastal Wetland Transformation in Response to Sea-Level Rise

Threats to coastal wetlands, including sea-level rise and subsidence, led the National Wildlife Refuge (NWR) System to protect over 500,000 hectares of coastal wetlands during the twentieth century, with approximately 20% occurring in the South Atlantic geography. This effort has involved systematic long-term monitoring of changes in marsh elevation using surface elevation tables and marker horizons at 20 sites across 19 NWRs in the southeastern coastal USA. From 2012 to 2021, the rates of change in surface elevation (−9.3 to 7.1 mm/year), accretion (−0.3 to 17.5 mm/year), and net vertical elevation change (−14.3 to 3.1 mm/year) were highly variable among monitoring sites and varied with coastal wetland type (oligohaline marsh, salt marsh, pocosin, or forested wetland), land surface elevation, and estuarine salinity and geomorphology (i.e., tidally influenced or embayed). Of 20 sites included in our study, only six were gaining elevation at a rate that was equal to or greater than the long-term rates of sea-level rise and therefore considered resilient. Only Waccamaw and Currituck NWRs, both located in oligohaline marshes, were gaining elevation at a rate that exceeded sea-level rise by 1 mm/year. These results support the mounting evidence that many coastal wetlands, particularly in the South Atlantic geography of the USA, will undergo ecological transformations in the next several decades. The NWR System and other coastal management entities will need to use strategic decision-making frameworks to identify management actions that can mitigate the loss of coastal wetlands to support the conservation of coastal wetland–dependent and obligate species.

Waterbird–habitat relationships in South Carolina: implications for protection, restoration, and management of coastal and inland wetlands

South Carolina coastal and inland wetlands are continentally important to resident, migrating, and wintering dabbling ducks (Anatini), diving and sea ducks (Aythini, Mergini, Oxyurini), pelagic waterbirds (Anhingidae, Laridae, Pelicanidae, and Phalcrocoracidae), and wading birds (Ardeidaie, Ciconiidae, Threskiornithidae). Our goal was to model wetland selection of these waterbird guilds in South Carolina during autumn–winter to determine habitat preferences and guide wetland conservation and restoration amid sea‐level rise and other coastal pressures. We conducted aerial surveys and recorded waterbird occurrence and relative abundance in winters 2017–2019. We modeled waterbird–habitat relationships relative to managed and unmanaged coastal and inland wetlands, legally protected conservation lands (e.g. federal, state, and private easements), and habitat diversity. Waterbirds selected a variety of wetlands emphasizing the importance of wetland diversity within habitat complexes. However, only managed tidal impoundments (MTIs) and protected conservation lands were selected across all waterbird guilds. Results suggest these are contemporary keystone habitats for promoting wintering waterbird abundance and diversity in South Carolina and other South Atlantic coastal regions. To compensate for future coastal wetland loss while facilitating the current and future needs of migrating and wintering waterbirds, we recommend: (1) identification and continued management of MTIs resilient to sea‐level rise; (2) strategic planning and partnerships for land acquisition and legal protections inland; and (3) land protection networks between extant coastal and inland sites designated for future construction and emigration of decommissioned MTIs. Stakeholder and partner engagement is paramount to prioritize resource allocation for the restoration, construction, and decommissioning of coastal and inland wetlands.

The concept of land bridge marshes in the Mississippi River Delta and implications for coastal restoration

Louisiana has high coastal wetland loss rates due to natural processes such as subsidence and anthropogenic activities such as construction of river levees and dams, pervasive alteration of surface hydrology by local industries such as oil and gas, and navigation. With the exception of the Atchafalaya River discharge area, most of Louisiana's marsh coastline is retreating and coastal marshes are degrading. In the inactive degrading delta regions, there exists a previously uncharacterized landform referred to colloquially as coastal ‘land bridge’ marshes. Land bridge marshes are saline or brackish marshes fronting large estuarine bays or lakes with sufficient fetch and wave energy to supply high levels of resuspended sediments to the marsh surface. They are generally linear features that are oriented parallel to the coast and the shoreline front retreats landward due to erosion from wave energy. These marshes persist over time vertically due to input of resuspended sediments but are experiencing rapid edge erosion due to wave attack. Comparison of data from Louisiana's Coastal Reference Monitoring System (CRMS) sites show that land bridge marshes have a greater frequency of higher soil surface elevation and higher soil bulk density than non-land bridge marshes. Because land bridges are vertically stable relative to other coastal wetlands, identification of measures to sustain these landscape features is important. Simulations using MarshMorpho2D, a process-based reduced-complexity morphology model, suggest that protection barriers installed on the seaward side of land bridge marshes will attenuate wave energy and, thus, edge erosion. Shoreline protection that can reduce wave energy but still allow sediment input to marshes include living shorelines, rock barriers, and/or breakwaters. Periodic thin layer nourishment of the marsh surface may be necessary to help sustain vertical growth. Further, marsh creation projects directly landward of land bridge marshes may benefit from their protection from waves and as a source of sediment. Consideration of land bridge marshes as distinct marsh types in the State Master Plan and integrated modeling could help to identify measures to sustain these landscape features.

The impacts of tidal wetland loss and coastal development on storm surge damages to people and property: a Hurricane Ike case-study

Coastal wetlands protect communities during hurricanes by reducing storm surge flooding and damages. Previous studies have quantified surge reduction benefits of wetlands, but there is less understanding of how the combination of wetland loss and coastal development influences the spatial distribution of flood extents and damages. In this study we integrate a high-resolution 2-D hydrodynamic model with land-use/land-cover change analyses to assess the effects of total wetland loss, decadal wetland loss, and coastal development on storm surge damages in Galveston Bay, Texas. We measure storm surge flood extents from Hurricane Ike for three scenarios: (i) 2008 Baseline; (ii) 2008 No Wetlands, and (iii) 2019 “Present-day H. Ike”. We find that during Hurricane Ike in 2008, the total loss of coastal wetlands would have increased damages by a net ~ USD $934 million or 12.8% of baseline damages. For the 2019 Present-day H. Ike scenario, we found very few wetlands were lost between 2008 and 2019. If Hurricane Ike had occurred in 2019, damages would have been higher by ~ $2.52 billion or 34.6%, almost entirely due to increased real estate value and new coastal development. Our findings suggest that, while increase in economic exposure is a key driver of storm surge risks in Galveston Bay, effective wetland conservation continues to reduce these risks.

Restoration otherwise: Towards alternative coastal ecologies

This article considers how to rethink ecological restoration as a process tethered to ongoing formulations of racial and environmental justice. It is situated in the context of coastal Louisiana's wetland loss crisis and the state's unprecedented investment in large-scale wetland restoration projects as a technoscientific fix that comes at the expense of several small, Black and Indigenous bayou communities. Critical of approaching restoration as a practice predicated on loss and return, this article builds upon scholarship in Black and Indigenous ecologies and ethnographic fieldwork among Black coastal communities in southeast Louisiana to reimagine restoration as an intergenerational, socioecological set of practices grounded in cultivating cultural continuity and community care across time and space. Working with the Black feminist geographic concepts of the plot and the shoal, the article develops the notion alternative restorations—or restoration otherwise—around three reformulations of restoration: As a practice of cultural continuity, as a mode of cultivating self-reliance, and as a scientific practice of integrity and humility. It concludes by reflecting the ways Black ecological practices and values can shift the course of restoration science toward sustaining Black life in the era of climate change.

An effective online platform for crowd classification of coastal wetland loss

AbstractWetland loss is increasing rapidly, and there are gaps in public awareness of the problem. By crowdsourcing image analysis of wetland morphology, academic and government studies could be supplemented and accelerated while engaging and educating the public. The Land Loss Lookout (LLL) project crowdsourced mapping of wetland morphology associated with wetland loss and restoration. We demonstrate that volunteers can be trained relatively easily online to identify characteristic wetland morphologies, or patterns present on the landscape that suggest a specific geomorphological process. Results from a case study in coastal Louisiana revealed strong agreement among nonexpert and expert assessments who agreed on classifications at least 83% and at most 94% of the time. Participants self‐reported increased knowledge of wetland loss after participating in the project. Crowd‐identified morphologies are consistent with expectations, although more work is needed to directly compare LLL results with previous studies. This work provides a foundation for using crowd‐based wetland loss analysis to increase public awareness of the issue, and to contribute to land surveys or train machine learning algorithms.

Coastal wetland area change for two freshwater diversions in the Mississippi River Delta

Coastal systems around the globe are being re-integrated with adjacent river systems to restore the natural hydrologic connection to riparian wetlands. The Mississippi River sediment diversions or river reconnections are one such tool to combat high rates of wetland loss in coastal Louisiana, USA by providing freshwater, sediment, and nutrients. There has been some disagreement in the published literature whether re-establishing river reconnection is slowing or contributing to coastal wetland loss. This issue is due to the difficulties in the application of remote sensing in low-relief environments where water level changes could indicate either land loss or simply temporary submergence. We analyzed land change at the receiving areas of two existing freshwater river diversions, Davis Pond and Caernarvon, which have been intermittently receiving river water for up to 2+ decades. This study provides a robust analysis of wetland land change rates in proximity these river diversions including years before river reconnection. Our analyses indicate a net land gain since river reconnection operations began at Davis Pond Diversion (+3.42 km2; range: +2.02–4.81 km2) and no statistically significant change at the Caernarvon Diversion. The Davis Pond wetland results are corroborated with data from a decadal field study documenting increased inorganic sedimentation in the soil. It is clear from this study and others, that river reconnection can increase or, in the case of Caernarvon, have no statistical effect on the land change in these systems due to differences in vegetation, hydroperiod, sediment delivery and external factors including hurricane impacts. Our remote sensing analysis was compared with a global water area change analysis mapping tool which also supported our findings.

A Model of the Spatiotemporal Dynamics of Soil Carbon Following Coastal Wetland Loss Applied to a Louisiana Salt Marsh in the Mississippi River Deltaic Plain

AbstractThe potential for carbon sequestration in coastal wetlands is high due to protection of carbon (C) in flooded soils. However, excessive flooding can result in the conversion of the vegetated wetland to open water. This transition results in the loss of wetland habitat in addition to the potential loss of soil carbon. Thus, in areas experiencing rapid wetland submergence, such as the Mississippi River Delta, coastal wetlands could become a significant source of carbon emissions if land loss is not mitigated. To accurately assess the capacity of wetlands to store (or emit) carbon in dynamic environments, it is critical to understand the fate of soil carbon following the transition from vegetated wetland to open water. We developed a simple soil carbon model representing soil depths to 1 m using the data collected from a Louisiana coastal salt marsh in the Mississippi River Deltaic Plain to predict soil carbon density and stock following the transition from a vegetated salt marsh to an open water pond. While immediate effects of ponding on the distribution of carbon within the 1‐m soil profile were apparent, there were no effects of ponding on the overall, integrated, carbon stocks 14 years, following wetland submergence. Rather, the model predicts that soil carbon losses in the first meter will be realized over long periods of time (∼200 years) due to changes in the source of carbon (biomass vs. mineral sediment) with minimal losses through mineralization.

Accelerating sea-level rise and the fate of mangrove plant communities in South Florida, U.S.A.

Analysis of four South Florida tide gauges, with records ranging from 27 to 116 yrs., indicate the average rate of sea-level rise has accelerated from 3.9 mm yr−1 (1900–2021) to 6.5 mm yr−1 (2000−2021), and 9.4 mm yr−1 over the past decade. Future rates are forecast to accelerate over the duration of this century. A predictive conceptual framework (model) was developed in which the resilience of South Florida mangrove plant communities is solely a function of the rate of sea-level rise and vertical sediment accumulation. The model was verified using historical (e.g., 1900–2021) and recent (e.g., 2000–2021) sediment accumulation rate data derived using three different methodological approaches. Results indicate by 2040–2050 South Florida mangrove plant communities, already subjected to the destabilizing effects of accelerating sea-level rise for decades, will begin a widespread conversion to estuarine conditions. This will initially trigger the formation and expansion of inundation ponds, as is already occurring in the study area. By the end of this century, most mangrove forested areas will be submerged. The loss of other coastal wetlands (e.g., brackish marsh) is also likely because their rates of sediment accumulation are lower than mangrove. The findings of this study are consistent with other resilience projections that have been conducted in South Florida and at the global scale. Several knowledge gaps were identified which must be filled to improve confidence in subsequent forecasts and the outcome of mitigation efforts undertaken to enhance resilience. These include the lack of (1) sediment accumulation data representative of transitional and freshwater wetlands, (2) a robust understanding of post-depositional processes (e.g., compaction) that can compromise resilience through shallow (~1 m) subsidence, and (3) recent sediment accumulation data necessary to determine how South Florida coastal wetlands have responded to a sustained acceleration in the rate of sea-level rise over the last decade.

Loss of Coastal Wetlands in Lake Burullus, Egypt: A GIS and Remote-Sensing Study

Lake Burullus is the second largest lake at the northern edge of the Nile Delta, Egypt, and has been recognized as an internationally significant wetland that provides a habitat for migrating birds, fish, herpetofauna, and mammals. However, the lake is experiencing severe human impacts including drainage and conversion to agricultural lands and fish farms. The primary goal of this study was to use multispectral, moderate-spatial-resolution (30 m2) Landsat satellite imagery to assess marsh loss in Lake Burullus, Egypt, in the last 35 years (1985–2020). Iterative Self-Organizing Data Analyses (ISODATA) unsupervised techniques were applied to the Landsat 5 Thematic Mapper (TM) and Landsat 8 Operational Land Imager–Thermal Infrared Sensor (OLI–TIRS) satellite images for classification of the Lake Burullus area into four main land-use classes: water, marsh, unvegetated land surfaces (roads, paths, sand sheets and dunes), and agricultural lands and fish farms. The overall classification accuracy was estimated to be 96% and the Kappa index was 0.95. Our results indicated that there is a substantial loss (44.8% loss) in the marsh aerial coverage between 1985 and 2020. The drainage and conversion of wetlands into agricultural lands and/or fish farms is concentrated primarily in the western and southern part of the lake where the surface area of the agricultural lands and/or fish farms doubled (103.2% increase) between 2000 and 2020. We recommend that land-use-policy makers and environmental government agencies raise public awareness among the local communities of Lake Burullus of the economic and environmental consequences of the alarming loss of marshland, which will likely have adverse effects on water quality and cause a reduction in the invaluable wetland-ecosystem services.