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Glaciologist Rob DeConto's research on polar climate change, specifically focusing on glaciers and ice sheets, is discussed in this article. DeConto explains the differences between Antarctica and Greenland and the challenges of understanding how the Antarctic ice sheet will behave in a warmer world. He also discusses the potential dangers of marine ice sheet instability and the impact of melting ice shelves on sea-level rise. The article emphasizes the uncertainties surrounding the rate of sea-level rise and the need for further research in this area. It highlights the term "deep uncertainty" used by the Intergovernmental Panel on Climate Change (IPCC) to describe the situation and the conservative nature of current projections. The author emphasizes the need for action to address the melting of ice sheets, as it poses a threat to infrastructure worldwide. [Extracted from the article]

AbstractTo combat the adverse effects of climate-change-driven sea-level rise, an increasing number of states have started preserving baselines. In this context, preservation means making baselines permanent despite changes to the coastline resulting from sea-level rise. In 2023, the International Law Commission’s Study Group on Sea-level rise in relation to international law released its Additional Paper on the impact of sea-level rise on the law of the sea. The Additional Paper focused on the states’ views concerning the possibility of preserving baselines irrespective of coastal changes caused by sea-level rise. However, the Additional Paper did not include a convincing methodological framing of the question of baseline preservation. This article frames this question as one of custom formation or treaty interpretation, arguing that neither framing would allow one to conclude that positive international law sanctions the preservation of baselines, but that there are viable solutions de lege ferenda to achieve it. [ABSTRACT FROM AUTHOR]

Arctic shorelines are vulnerable to climate change impacts as sea level rises, permafrost thaws, storms intensify, and sea ice thins. Seventy-five years of aerial and satellite observations have established coastal erosion as an increasing Arctic hazard. However, other hazards at play--for instance, the cumulative impact that sea-level rise and permafrost thaw subsidence will have on permafrost shorelines--have received less attention, preventing assessments of these processes' impacts compared to and combined with coastal erosion. Alaska's Arctic Coastal Plain (ACP) is ideal for such assessments because of the high-density observations of topography, coastal retreat rates, and permafrost characteristics, and importance to Indigenous communities and oilfield infrastructure. Here, we produce 21st-century projections of Arctic shoreline position that include erosion, permafrost subsidence, and sea-level rise. Focusing on the ACP, we merge 5 m topography, satellite-derived coastal lake depth estimates, and empirical assessments of land subsidence due to permafrost thaw with projections of coastal erosion and sea-level rise for medium and high emissions scenarios from the Intergovernmental Panel on Climate Change's AR6 Report. We find that by 2100, erosion and inundation will together transform the ACP, leading to 6-8x more land loss than coastal erosion alone and disturbing 8-11x more organic carbon. Without mitigating measures, by 2100, coastal change could damage 40 to 65% of infrastructure in present-day ACP coastal villages and 10 to 20% of oilfield infrastructure. Our findings highlight the risks that compounding climate hazards pose to coastal communities and underscore the need for adaptive planning for Arctic coastlines in the 21st century. [ABSTRACT FROM AUTHOR]

Reduced riverine sediment supply and sea-level rise (SLR) threaten land building and ecosystem in deltas. However, the sediment-morphodynamic processes in a channel-shoal complex are not well understood. Here, based on bathymetry and the Delft3D model, geomorphic changes and suspended sediment budgets in the South Passage, Nanhui and Jiuduansha Shoal in the mega-Changjiang Delta were examined. Results reveal that with riverine suspended sediment concentration (SSC) decreased by 75%, the net sediment deposition rate was reduced from 4.20 cm/yr in 1979–1990 to 3.21 cm/yr in 1990–2003, and further declined to 2.21 cm/yr in 2003–2013 and 0.40 cm/yr in 2013–2020. Severe erosion occurred along the upper South Passage and extended toward the mouth bar. Strong accretions accumulated in the Nanhui and Jiuduansha Shoal. After river SSC declined from 0.53 kg/m3 to 0.35 kg/m3, 0.16 kg/m3, and 0.12 kg/m3, net suspended sediment deposition was lowered by 3.13%, 7.35% and 8.67%, respectively. Moreover, SLR of 5 cm, 15 cm, 25 cm, and 50 cm resulted in a further 1.11%, 4.18%, 4.16%, and 14.79% reduction in sediment trapping efficiency. Our findings highlight the strong likelihood that reduced river sediment input, SLRs and intensified anthropogenic effects will exacerbate sediment deficit and erosion in mega fluvial-tidal deltas. [ABSTRACT FROM AUTHOR]

Sea-level rise is accelerating globally and will continue for centuries under all shared socio- economic pathways. Although sea-level rise is a global issue, its impacts manifest heterogeneously at the local scale, with some coastal communities and infrastructure considerably more vulnerable than others. Aotearoa New Zealand is poorly prepared to deal with sea-level rise impacts, and some places are already approaching the limits of adaptation, short of relocation. Maladaptive choices threaten Aotearoa's ongoing ability to adapt going forward. Development of climate-resilient pathways requires an immediate adoption of non-partisan, long-term, system-scale approaches to governance and decision making (from local to national), that integrate effective adaptation and emissions mitigation. This also requires proactive and collective action underpinned by indigenous and actionable knowledge (e.g., NZ SeaRise projections) designed for our unique circumstances. There is still time to put in place sustainable, equitable and effective solutions, but funding and governance models need urgent attention. [ABSTRACT FROM AUTHOR]

Leaf litter in coastal wetlands lays the foundation for carbon storage, and the creation of coastal wetland soils. As climate change alters the biogeochemical conditions and macrophyte composition of coastal wetlands, a better understanding of the interactions between microbial communities, changing chemistry, and leaf litter is required to understand the dynamics of coastal litter breakdown in changing wetlands. Coastal wetlands are dynamic systems with shifting biogeochemical conditions, with both tidal and seasonal redox fluctuations, and marine subsidies to inland habitats. Here, we investigated gene expression associated with various microbial redox pathways to understand how changing conditions are affecting the benthic microbial communities responsible for litter breakdown in coastal wetlands. We performed a reciprocal transplant of leaf litter from four distinct plant species along freshwater‐to‐marine gradients in the Florida Coastal Everglades, tracking changes in environmental and litter biogeochemistry, as well as benthic microbial gene expression associated with varying redox conditions, carbon degradation, and phosphorus acquisition. Early litter breakdown varied primarily by species, with highest breakdown in coastal species, regardless of the site they were at during breakdown, while microbial gene expression showed a strong seasonal relationship between sulfate cycling and salinity, and was not correlated with breakdown rates. The effect of salinity is likely a combination of direct effects, and indirect effects from associated marine subsidies. We found a positive correlation between sulfate uptake and salinity during January with higher freshwater inputs to coastal areas. However, we found a peak of dissimilatory sulfate reduction at intermediate salinity during April when freshwater inputs to coastal sites are lower. The combination of these two results suggests that sulfate acquisition is limiting to microbes when freshwater inputs are high, but that when marine influence increases and sulfate becomes more available, dissimilatory sulfate reduction becomes a key microbial process. As marine influence in coastal wetlands increases with climate change, our study suggests that sulfate dynamics will become increasingly important to microbial communities colonizing decomposing leaf litter. [ABSTRACT FROM AUTHOR]

To increase the resilience of salt marshes subject to sea‐level rise impacts, managers can focus on interventions within current marsh footprints or in adjacent uplands to facilitate landward marsh migration. The latter approach may be more appropriate when degradation is severe and in situ intervention options are limited. Strategies for facilitating marsh migration include removing artificial barriers, soil grading to reduce steep topography, and manipulating adjacent upland vegetation that can hinder migration, but experiments testing the effectiveness of these activities are limited. We therefore conducted a field experiment to determine if physically removing three upland vegetation types (forest, shrub, and Phragmites australis) adjacent to a Rhode Island salt marsh facilitates short‐term marsh migration. Upland vegetation removal led to increased ambient light in all habitats, significantly enhanced marsh plant cover, extent, and elevation in shrub habitat, and declines in total bird abundance in forest and shrub habitats. Enhanced migration did not occur in forest or Phragmites habitats, and in shrubs, marsh plants only colonized where Baccharis halimifolia, common in upper marsh borders, had been removed. Five years after removal, all upland habitats and associated vegetation were indistinguishable from initial conditions. Our study suggests that upland plant removal might provide a limited window for facilitating salt marsh migration and that more intensive methods may be needed for sustained, longer‐term benefits. It also demonstrates that there may be ecological trade‐offs to consider when altering upland habitats to enhance landward marsh migration. [ABSTRACT FROM AUTHOR]

Bayhead deltas form at the interface between fluvial and estuarine systems. As such, they are sensitive to processes operating in both the fluvial catchment and the marine realm, including past relative sea‐level changes. The Nakdong valley is a small and confined incised valley containing a bayhead delta that provides a record of fluvial sediment input and accommodation changes. Based on a facies analysis that included 833 sediment textures and 118 optically stimulated luminescence and radiocarbon ages within five cores up to 70 m long, this study reconstructed the development of a fully filled bayhead delta in response to relative sea‐level changes through the early to late Holocene. Sixteen facies are defined and grouped into eight facies associations: alluvial plain; fluvial channel and floodplain; oxidized fluvial channel; tidal flat; tidal bar; central basin and bayhead prodelta; bayhead delta front; and bayhead delta plain. The sequence stratigraphy of the Nakdong valley fill can be divided into three systems tracts: a lowstand systems tract, a transgressive systems tract and a highstand systems tract. Overall sedimentary analyses suggest six depositional stages corresponding to variations between sediment inputs and sea‐level rise of the developing bayhead delta in the Nakdong valley. The depositional model tracks relative sea‐level rise in the Nakdong valley after 12 ka during the early to late Holocene. These analyses on the Nakdong bayhead delta succession illustrate the balance between sediment inputs and periods of accelerating and decelerating relative sea‐level rise during the Holocene. The architecture of the valley fill also records two abrupt disequilibrium events from 9 to 8 ka and 5 to 3 ka, likely resulting from rapid sea‐level rise during the deglacial outburst flooding of the early Holocene and decreased sediment inputs during regional climatic changes associated with the middle Holocene, respectively. [ABSTRACT FROM AUTHOR]

Disentangling the effects of cyclical variability in environmental forcing and long‐term climate change on natural communities is a major challenge for ecologists, managers, and policy makers across ecosystems. Here we examined whether the vertical distribution of rocky intertidal taxa has shifted with sea‐level variability occurring at multiple temporal scales and/or long‐term anthropogenic sea‐level rise (SLR). Because of the distinct zonation characteristic of intertidal communities, any shift in tidal dynamics or average sea level is expected to have large impacts on community structure and function. We found that across the Northeast Pacific Coast (NPC), sea level exhibits cyclical seasonal variability, tidal amplitude exhibits ecologically significant variability coherent with the 18.6‐year periodicity of lunar declination, and long‐term sea‐level rise is occurring. Intertidal taxa largely do not exhibit significant vertical distribution shifts coherent with short‐term (monthly to annual) sea‐level variability but do exhibit taxa‐specific vertical distribution shifts coherent with cyclical changes in lunar declination and long‐term SLR at decadal timescales. Finally, our results show that responses to cyclical celestial mechanics and SLR vary among taxa, primarily according to their vertical distribution. Long‐term SLR is occurring on ecologically relevant scales, but the confounding effects of cyclical celestial mechanics make interpreting shifts in zonation or community structure challenging. Such cyclical dynamics alternatingly amplify and dampen long‐term SLR impacts and may modify the impacts of other global change related stressors, such as extreme heat waves and swell events, on intertidal organisms living at the edge of their physiological tolerances. As a result, intertidal communities will likely experience cyclical periods of environmental stress and concomitant nonlinear shifts in structure and function as long‐term climate change continues. Our results demonstrate that consistent, large‐scale monitoring of marine ecosystems is critical for understanding natural variability in communities and documenting long‐term change. [ABSTRACT FROM AUTHOR]

Coastal hazards threaten properties, infrastructure, and cultural sites around Aotearoa New Zealand's (hereafter Aotearoa) coastline and sea-level rise (SLR) will escalate this problem. At present it is unclear how archaeological sites will be affected by future coastal erosion and inundation. In this paper we combine national-scale archaeological and environmental datasets to provide a first-pass overview of archaeological heritage at risk in Aotearoa. Two key national-scale datasets are utilized: (1) coastal sensitivity index (CSI) developed by the National Institute of Water and Atmospheric Research; and (2) ArchSite, Aotearoa's archaeological site database. The integrated datasets produce insights into the sensitivity of coastal archaeology to SLR and associated hazards, which are vital to planning for the loss of coastal archaeological sites. More than half (∼55%) of recorded coastal archaeological sites around Aotearoa are midden (n = 4938) and about 25% (n = 2271) are earthworks. In total, ca. 12% (9054) of all known archaeological sites are within 1000 m of soft shore shorelines. Of this total, only about 3% (302) of sites are burials, but the loss of these 302 burial sites would have very high cultural impact. Coastal erosion is a particularly important threat to archaeology as it would permanently remove sites, whereas the risk of site removal by coastal flooding inundation is lower. Our results show that about 22% (1954) of coastal archaeological sites are located on landforms that are sensitive to SLR-driven erosion: 29% (2660) of archaeological sites are located on foredune barrier beaches, 23% (2059) on foredune barrier plains, 14% (1283) on beaches, and 9% (808) on beach ridge barriers. This work draws attention to the scale of coastal archaeology in Aotearoa that needs adequate documentation, preservation, and potentially protection in the face of SLR. Robust coastal erosion and inundation datasets are needed to more deeply understand potential SLR-driven impacts on coastal archaeology and provide a scientific foundation for considering future adaptation options. [ABSTRACT FROM AUTHOR]

ABSTRACT: Introduction: Disrupted weather patterns are associated with climate change. Between 2001 and 2018, nearly 74% of disasters were water-related, including floods and cyclones. Such water-related cataclysmic events increase the risk of drowning. We aimed to map evidence on the impact of climate change on water-related physical events, associated human migration, and drowning burden in India. Materials and Methods: We searched electronic databases, government reports, and relevant websites to map evidence on water-related physical events (including but not limited to sea-level rise, glacier bursts, lake bursts, floods, rainfall, cyclones, and droughts) and consequent human migration using narrative review approach, while drowning burden through scoping review approach. We summarized the results narratively. Results: Evidence from 48 studies and seven reports suggest that India will witness the greatest sea-level rise, significantly impacting poor coastal communities. An increase in droughts, cyclonic rainfall, storms, and floods, with increasing surface rainwater and streamflow water, due to melting glaciers is expected. Climate change–triggered migration is expected notably in northeast and south India, making farmers, drivers, street vendors, women, and youth most vulnerable. No direct evidence was identified on the impact of climate change, water-related disasters, meteorological events, or seasonal variations on drowning from India. Conclusion: Our study highlights a significant gap in the availability of context-specific and localized data to improve disaster response and strengthen public health systems, especially for areas most vulnerable to climate change. There is an urgent need to generate new knowledge and understanding of climate change, water-related or meteorological events, and seasonal variations' impact on drowning burden as the level of risk remains unknown. [ABSTRACT FROM AUTHOR]

Durant, D. and Kernéïs, E., 2024. Investigating the farm resilience of polder environments after seawater flooding: Results from Storm Xynthia (2010). Journal of Coastal Research, 40(5), 887–900. Charlotte (North Carolina), ISSN 0749-0208. Climate forecasts predict that global warming will cause sea-levels to rise and will increase the frequency of storms in the future, thus also increasing the risk of submersion of coastal agricultural areas. Yet very few studies examine the consequences of seawater flooding, from either an agricultural or an environmental point of view. This study therefore investigates the resilience of coastal farming systems through the case study of the Saint Laurent de la Prée research farm hit by the Storm Xynthia in 2010. Two aspects of resilience are analysed here: (i) the soil characteristics of the system (indicators: salinity, sodicity and structural stability) after the submersion, and the system's ability to recover its productive capacity on croplands (crop yields) and on permanent grasslands (fodder production); and (ii) the ecological resilience of permanent grasslands (indicators: species richness and diversity). Results showed that the system recovered its productive capacity in 2012, so after two years, when the research farm engineers recorded a return of the crops and grasslands to a production level that they considered satisfactory. For crop soils, there was a quick recovery of salinity levels, but the structural stability after the storm was largely degraded and had not totally recovered by 2012. On grasslands, the farm suffered two successive years of low grassland productivity, partially due to a temporary shift in plant species' composition. Finally, two dimensions of resilience are discussed here: (i) the speed of recovery; and (ii) the ability to learn from the storm, in view of the increasing risks of coastal submersion in the future. As it appears that flood protection policy must consider local and long-term impacts of seawater flooding on agricultural lands, this study can provide useful information for further research on the foresight scenarios and adaptive strategies required. [ABSTRACT FROM AUTHOR]

Climate change is an existential threat to the environmental and socioeconomic sustainability of the coastal zone and impacts will be complex and widespread. Evidence from California and across the United States shows that climate change is impacting coastal communities and challenging managers with a plethora of stressors already present. Widespread action could be taken that would sustain California's coastal ecosystems and communities. In this perspective, we highlight the main threat to coastal sustainability: the compound effects of episodic events amplified with ongoing climate change, which will present unprecedented challenges to the state. We present two key challenges for California's sustainability in the coastal zone: 1) accelerating sea-level rise combined with storm impacts, and 2) continued warming of the oceans and marine heatwaves. Cascading effects from these types of compounding events will occur within the context of an already stressed system that has experienced extensive alterations due to intensive development, resource extraction and harvesting, spatial containment, and other human use pressures. There are critical components that could be used to address these immediate concerns, including comanagement strategies that include diverse groups and organizations, strategic planning integrated across large areas, rapid implementation of solutions, and a cohesive and policy relevant research agenda for the California coast. Much of this has been started in the state, but the scale could be increased, and timelines accelerated. The ideas and information presented here are intended to help expand discussions to sharpen the focus on how to encourage sustainability of California's iconic coastal region. [ABSTRACT FROM AUTHOR]

Freshwater lenses and their freshwater–saltwater transition zones are affected by climate change. Both sea-level rise and groundwater recharge influence freshwater volume and transition zone thickness. This study used a semi-generic approach to investigate climate change effects on freshwater lenses: a hypothetical island cross-section was combined with real-world boundary conditions. Sea-level projections including tides and storm surges, annual mean sea-level rise data, and monthly recharge projections of several climate models of the German barrier island Norderney in the North Sea were used to evaluate changes in freshwater lens and transition zone size between 1971–2000 and 2071–2100. Firstly, impacts of sea-level and recharge boundary conditions were investigated on islands of different widths. Secondly, a multi-parameter study was conducted focussing on variations of several relevant hydrogeological parameters. Results showed that it is very likely but not certain that freshwater lens volume and depth will decrease and transition zone thickness increase as a consequence of climate change. Model predictions revealed a strong dependency on the employed climate models and to a lesser extent on the hydrogeological parameters, at least for the parameter ranges used in this study. Of all hydrogeological parameters tested, the largest effects were caused by the hydraulic conductivity and its anisotropy. Furthermore, the study showed that boundary conditions have larger impacts on smaller islands. These results illustrate the importance of using projections from climate models in a sufficiently high resolution. Furthermore, their uncertainties and changes in variability of boundary conditions should be considered in studies about climate change impacts on freshwater lenses. [ABSTRACT FROM AUTHOR]

Recent Greenland ice-sheet melt constitutes a considerable contribution to global sea-level rise. Observations indicate an approximate zero mass balance of the ice sheet until the late 1990s, after which a strong increase in melting occurred. This cannot be attributed linearly to gradually-increasing global warming. Instead the abrupt shift has been linked to atmospheric circulation changes, although causality is not fully understood. Here we show that changes of atmospheric waves over Greenland have significantly contributed to the shift into a strong melting state. This is evident after having applied a newly-developed methodology effectively decomposing atmospheric flow patterns into parts associated with waves of different scales such as Rossby waves and smaller perturbations. The onset of a westerly-flow reduction, consistent with anthropogenic Arctic warming, affected transports by atmospheric waves and led to a decrease in precipitation and an increase in surface warming, contributing to ice-sheet mass loss, in particular over the southwestern regions. As such, the Greenland ice-sheet melt is an example of a climate response non-linearly coupled to global warming. [ABSTRACT FROM AUTHOR]

A policy subsystem is a system of relations between actors within the context of a specific, territorially bounded policy issue. Mature policy subsystems feature well‐established, easily distinguishable, confrontational coalitions. Recent literature has explored the behavior of nascent subsystems, which emerge in response to novel policy challenges and feature developing, rather than fully fledged, coalitions. However, as yet, we lack an empirical approach to identify and analyze the structural characteristics of nascent subsystems and assess their implications for theoretical and subsystem development. How do we recognize a nascent policy subsystem when we see one? What are the drivers of its nascent coalitional structure? We answer these questions using social network analysis in the empirical case of the governance network of adaptation to sea‐level rise in the San Francisco Bay Area, using original data collected in 2018. We find that the network portrays a nascent subsystem developing out of pre‐existing coalitions focused on two facets of environmental advocacy: environmental protection and environmental justice. We conclude with recommendations for future research on policy subsystem development. [ABSTRACT FROM AUTHOR]

Southeast Australian saltmarshes are endangered ecological communities under threat from various anthropogenic factors including climate change. As climate change drives sea‐level rise mangrove encroachment and saltmarshes are squeezed at their landward edge, our lack of knowledge of the ecological interactions and any associations between saltmarsh vegetation and fauna becomes concerning, especially given the importance of saltmarsh for fisheries and as a blue carbon habitat. This study investigated the association of saltmarsh vegetation and the abundance and movement of gastropods in a typical coastal saltmarsh at Patonga, New South Wales, Australia. Densities of the gastropods including Phallomedusa solida, Ophicardelus spp. and Littoraria luteola were significant in vegetated Salicornia quinqueflora and least in unvegetated saltmarsh and areas where mangroves had encroached. Experiments that translocated Ophicardelus spp. and manipulated cover revealed that these patterns were actively maintained by Ophicardelus spp., which dispersed up to 40 cm and 1.4 m after 3 and 24 h, respectively, away from unvegetated saltmarsh and mangroves. The results of this study suggest that both habitat and cover influence the abundance and movement of gastropod dynamics in southeastern saltmarsh. Given future anticipated saltmarsh loss, further investigations are needed on the unknown functional role of gastropods in saltmarsh ecosystems. [ABSTRACT FROM AUTHOR]

This systematic review assesses the relationship between climate induced coastal hazards and psychological well-being of communities in the Asia-Pacific region. The review synthesises findings from 13 peer-reviewed articles published between 2007 and 2020, encompassing data from seven countries: Bangladesh, India, Indonesia, Philippines, Solomon Islands, Tuvalu, and Vietnam. Results reveals a robust negative association between exposure to coastal hazards and psychological outcomes, notably stress, depression, anxiety, and distress. Most of the studies (77%) corroborate negative impacts of coastal hazards on psychological health. Additionally, 69% of the reviewed articles suggest a correlation between coastal hazards and negative outcomes for community livelihoods and essential resources. The review highlights increased psychological vulnerability among marginalised subpopulations, such as economically disadvantaged communities, a trend supported by 92% of the examined articles. The findings indicates that factors such as environmental vulnerability, resource availability, community traits, and coping methods are important in determining whether a community can effectively handle coastal hazards or face increased psychological health risks. This research aligns with international health frameworks, including the World Health Organization’s Health Emergency and Disaster Risk Management guidelines. However, a notable research gap emerges – the absence of studies that specifically explore psychological responses of communities to ongoing climate-related coastal hazards, such as sea-level rise. These findings emphasise an urgent need for targeted research to guide comprehensive, multidisciplinary policy interventions aimed at mitigating the psychological and socio-economic repercussions of climate-related coastal hazards. [ABSTRACT FROM AUTHOR]

Accelerated warming since the 1950s has caused dramatic change to ice shelves and outlet glaciers on the Antarctic Peninsula. Long observational records of ice loss in Antarctica are rare but essential to accurately inform mass balance estimates of glaciers. Here, we use aerial images from 1968 to reveal glacier configurations in the Larsen B region. We use structure-from-motion photogrammetry to construct high-resolution (3.2 m at best) elevation models covering up to 91% of Jorum, Crane, Mapple, Melville and Flask Glaciers. The historical elevation models provide glacier geometries decades before the Larsen B Ice Shelf collapse in 2002, allowing the determination of pre-collapse and post-collapse elevation differences. Results confirm that these five tributary glaciers of the former Larsen B Ice Shelf were relatively stable between 1968 and 2001. However, the net surface elevation differences over grounded ice between 1968 and 2021 equate to 35.3 ± 1.2 Gt of ice loss related to dynamic changes after the ice shelf removal. Archived imagery is an underutilised resource in Antarctica and was crucial here to observe glacier geometry in high-resolution decades before significant changes to ice dynamics. [ABSTRACT FROM AUTHOR]

Managed retreat is a climate adaptation strategy involving government buyouts of at-risk properties that is currently underutilized in coastal areas of the United States. These programs often require both voluntary homeowner applications and municipal government support for a successful buyout. We use a conceptual framework and a set of empirical models with data from a buyout program in a coastal state to develop descriptive evidence on potential barriers to successful managed-retreat policies in high-risk coastal areas. Key factors influencing buyout success can be associated with municipal budgets, including revenues, expenditures, debt, and government transfers. Importantly, revenue impacts related to property taxes appear to contribute to fewer buyouts, suggesting a potential principal-agent problem related to climate resilience in high-value coastal housing markets. Recognition of the combination of factors that may represent barriers to adoption may help the design and implementation of future programs and improve coastal climate adaptation strategies. [ABSTRACT FROM AUTHOR]

Questions: Baltic coastal meadows are ecologically unique habitats that have been severely impacted by habitat loss and environmental change. To determine the effects of habitat loss and isolation on their plant communities, we analysed the relationships between species richness and habitat size and amount. Because coastal meadows host species with a vast array of traits, we expected responses to vary between species groups. Location: Swedish Baltic coast. Methods: We inventoried the presence of vascular plant species in twenty‐eight 1‐m2 plots placed along edaphically defined transects in fifteen coastal meadows. We determined the richness of three species groups: all species, halophytes and inland grassland specialists. We then mapped the habitat for coastal grassland plants using GIS overlay analysis. Using this habitat map, we calculated two variables: "habitat size" and "habitat amount". We tested correlations between species richness measures and habitat variables, as well as determining the distribution of species traits within meadows. Results: We recorded 174 plant species, of which 6 were halophytes and 35 were inland grassland specialists. Species traits coincided with edaphic sea‐to‐land gradients. Halophyte and inland grassland specialist richness were significantly correlated with both habitat variables (r = 0.52–0.71). No correlations were found with total species richness. Our habitat map showed that there are 8,900 ha of managed Baltic coastal meadow left in Sweden, mostly in the south. Conclusions: Species traits and distribution play a major role in determining persistence in the face of habitat loss and environmental change. This is especially true for some halophyte populations, which are more susceptible to habitat size and isolation because of their specialisation. Furthermore, they risk being squeezed between the dual threats of encroaching succession and sea‐level rise. Preventing habitat loss, restoring meadows and increasing connectivity is crucial for the persistence of specialist plant species. [ABSTRACT FROM AUTHOR]

Tidal salt marshes offer crucial ecosystem services in the form of carbon sequestration, fisheries, property and recreational values, and protection from storm surges, and are therefore considered one of the most valuable and fragile ecosystems worldwide, where sea-level rise and direct human modifications resulted in the loss of vast regions of today's marshland. The extent of salt marshes therefore relies heavily on the interplay between upland migration and edge erosion. We measured changes in marsh size based on historical topographic sheets from the 1850s and 2019 satellite imagery along the Texas coast, which is home to three of the largest estuaries in North America (e.g., Galveston, Corpus Christi, and Matagorda Bays). We further distinguished between changes in high and low marsh based on local elevation data in an effort to estimate changes in local ecosystem services. Our results showed that approximately 410 km2 (58%) of salt marshes were lost due to coastal erosion and marsh ponding and nearly 510 km2 (72%) of salt marshes were created, likely due to upland submergence. Statistical analyses showed a significant relationship between marsh migration and upland slope, suggesting that today's marshland formed as a result of submergence of barren uplands along gently sloping coastal plains. Although the overall areal extent of Texas marshes increased throughout the last century (~100 km2 or 14%), economic gains through upland migration of high marshes (mostly in the form of property value (USD 0.7–1.0 trillion)) were too small to offset sea-level-driven losses of crucial ecosystem services of Texan low marshes (in the form of storm protection and fisheries (USD 2.1–2.7 trillion)). Together, our results suggest that despite significant increases in marsh area, the loss of crucial ecosystem services underscores the complexity and importance of considering not only quantity but also quality in marshland conservation efforts. [ABSTRACT FROM AUTHOR]

Evidence of ancient Maya exploitation of salt, other marine resources, settlement, and sea trade is hidden in flooded mangrove landscapes on the cays, mainland, and in shallow offshore locations on the south coast of Belize. This article includes a discussion of the coastal economy from the Middle Preclassic through the Postclassic periods (600 B.C.–A.D. 1500). Data from sites discovered and excavated since 1982 in the coastal area of the Port Honduras and Paynes Creek National Park support a model of coastal reliance on marine resources and tree crops. The need for a regular supply of coastal salt to inland cities may have expanded the market for other marine resources. Obsidian imported from volcanic highlands documents long-distance trade throughout prehistory in the area. The island of Wild Cane Cay expanded its role in long-distance coastal trade after the abandonment of inland cities in southern Belize at the end of the Classic period. Inundation of the region documented from the depths of radiocarbon-dated archaeological deposits below the water table and from a sediment core indicates sea-level rise of at least 1 m that submerged the coastal sites. The waterlogged deposits provided an ideal matrix for preservation of vertebrate material at Wild Cane Cay. The red mangrove (Rhizophora mangle) peat below the sea floor in a shallow lagoon preserved wooden buildings. [ABSTRACT FROM AUTHOR]

Coastal wetlands are vulnerable to accelerated sea-level rise, yet knowledge about their extent and distribution is often limited. We developed a land cover classification of wetlands in the coastal plains of the southern United States along the Gulf of Mexico (Texas, Louisiana, Mississippi, Alabama, and Florida) using 6161 very-high (2 m per pixel) resolution WorldView-2 and WorldView-3 satellite images from 2012 to 2015. Area extent estimations were obtained for the following vegetated classes: marsh, scrub, grass, forested upland, and forested wetland, located in elevation brackets between 0 and 10 m above sea level at 0.1 m intervals. Sea-level trends were estimated for each coastal state using tide gauge data collected over the period 1983–2021 and projected for 2100 using the trend estimated over that period. These trends were considered conservative, as sea level rise in the region accelerated between 2010 and 2021. Estimated losses in vegetation area due to sea level rise by 2100 are projected to be at least 12,587 km2, of which 3224 km2 would be coastal wetlands. Louisiana is expected to suffer the largest losses in vegetation (80%) and coastal wetlands (75%) by 2100. Such high-resolution coastal mapping products help to guide adaptation plans in the region, including planning for wetland conservation and coastal development. [ABSTRACT FROM AUTHOR]

Sea-level rise was a key factor changing environments during the Early Holocene in Northwest Europe. It affected Mesolithic hunter-gatherer communities by inundating large areas in the current North Sea, commonly referred to as Doggerland. In this paper we present novel inundation models for the southern North Sea providing visualisations of lateral inundation driven by sea-level rise and relate it to frequency analysis of radiocarbon dates from archaeological sites. These improve on previous studies that relied on bathymetric data, which includes post-inundation overprints of Holocene sedimentation and erosion, and thus significantly underestimates the timing of inundation in some areas. We constructed a paleoDEM (a composite elevation grid of the top of the Pleistocene) for the eastern part of the southern North Sea; and sea level surfaces that combine relative sea-level curves from glacio-isostatic adjustment models optimised for Britain and southern Scandinavia respectively. We corrected our paleoDEMs for tectonic background basin subsidence, and in the inundation modelling account for pre-compaction elevation of peat in coastal areas. We evaluated the impact of these model components on our results and describe the possible inundation history of Doggerland. We suggest earlier inundation than predicted by previous models, showing significant area loss around 10.5–10 ka cal BP. Palaeogeographic changes are compared with archaeological radiocarbon data using a dates-as-data approach. Composite Kernel Density Estimate and permutation tested Summed Probability Distributions are used as a proxy for the visibility, nature and intensity of human activity. Results indicate key periods of growth and decline recorded in the dataset, as well as regional differences in growth rate, some correlating with inundation phases. Chiefly, we find elevated growth rates around 10.5–10 ka in northwest Germany and the Netherlands, contemporaneous with the abovementioned phase of extensive area loss, and moreover, with changes in culture and practices on Early Mesolithic sites. However, the spatiotemporal distribution of archaeological data is significantly influenced by accessibility and preservation of sediments of a certain age. We discuss the importance of inundation modelling and sediment data in understanding how landscape taphonomy affects archaeological patterning, especially in dates-as-data approaches. [ABSTRACT FROM AUTHOR]

Climate change is accelerating sea‐level rise and saltwater intrusion in coastal regions world‐wide and interacting with large‐scale changes in species composition in coastal wetlands. Quantifying macrophyte litter breakdown along freshwater‐to‐marine coastal gradients is needed to predict how carbon stores will respond to shifts in both macrophyte communities and water chemistry under changing environmental conditions.To test the interactive drivers of changing species identity and water chemistry, we performed a reciprocal transplant of four macrophyte litter species in seven sites along freshwater‐to‐marine gradients in the Florida Coastal Everglades. We measured surface water chemistry (dissolved organic carbon, total nitrogen and total phosphorus), litter chemistry (% nitrogen, % phosphorus, change in N:P molar ratio, % cellulose and % lignin as proxies for recalcitrance) and litter breakdown rates (k/degree‐day).Direct effects of salinity and surface water nutrients were the strongest drivers of k, but unexpectedly, litter chemistry did not correlate with litter k. However, salinity strongly correlated with changes in litter chemistry, whereby litter incubated in brackish and marine wetlands was more labile and gained more phosphorus compared with litter in freshwater marshes. Our results suggest that litter k in coastal wetlands is explained by species‐specific interactions among water and litter chemistries. Water nutrient availability was an important predictor of breakdown rates across species, but breakdown rates were only explained by the carbon recalcitrance of litter in the species with the slowest breakdown (Cladium jamaicense), indicating the importance of carbon structure, and species identity on breakdown rates.Synthesis. In oligotrophic ecosystems, nutrients are often the primary driver of organic matter breakdown. However, we found that variation in macrophyte breakdown rates in oligotrophic coastal wetlands was also explained by salinity and associated seawater chemistry, emphasising the need to understand how saltwater intrusion will alter organic matter processing in wetlands. Our results suggest that marine subsidies associated with sea‐level rise have the potential to accelerate leaf litter breakdown. The increase in breakdown rates could either be buffered or increase further as sea‐level rise also shifts macrophyte community composition to more or less recalcitrant species. [ABSTRACT FROM AUTHOR]

Aim and Questions: Sea‐level rise has been responsible for extensive vegetation changes in coastal areas worldwide. The intent of our study was to analyze vegetation dynamics of a South Florida coastal watershed within an explicit spatiotemporal framework that might aid in projecting the landscape's future response to restoration efforts. We also asked whether recent transgression by mangroves and other halophytes has resulted in reduced plant diversity at local or subregional scales. Location: Florida''s Southeast Saline Everglades, USA. Methods: We selected 26 locations, representing a transition zone between sawgrass marsh and mangrove swamp, that was last sampled floristically in 1995. Within this transition zone, leading‐ and trailing‐edge subzones were defined based on plant composition in 1995. Fifty‐two site × time combinations were classified and then ordinated to examine vegetation–environment relationships using 2016 environmental data. We calculated alpha‐diversity using Hill numbers or Shannon–Weiner index species equivalents and compared these across the two surveys. We used a multiplicative diversity partition to determine beta‐diversity from landscape‐scale (gamma) diversity in the entire dataset or in each subzone. Results: Mangrove and mangrove associates became more important in both subzones: through colonization and establishment in the leading edge, and through population growth combined with the decline of freshwater species in the trailing edge. Alpha‐diversity increased significantly in the leading edge and decreased nominally in the trailing edge, while beta‐diversity declined slightly in both subzones as well as across the study area. Conclusions: Recent halophyte encroachment in the Southeast Saline Everglades continues a trend evident for almost a century. While salinity is an important environmental driver, species' responses suggest that restoration efforts based on supplementing freshwater delivery will not reverse a trend that depends on multiple interacting factors. Sea‐level‐rise‐driven taxonomic homogenization in coastal wetland communities develops slowly, lagging niche‐based changes in community structure and composition. [ABSTRACT FROM AUTHOR]

The largest uncertainty in future sea-level rise is loss of ice from the Greenland and Antarctic Ice Sheets. Ice shelves, freely floating platforms of ice that fringe the ice sheets, play a crucial role in restraining discharge of grounded ice into the ocean through buttressing. However, since the 1990s, several ice shelves have thinned, retreated, and collapsed. If this pattern continues, it could expose thick cliffs that become structurally unstable and collapse in a process called marine ice cliff instability (MICI). However, the feedbacks between calving, retreat, and other forcings are not well understood. Here we review observed modes of calving from ice shelves and marine-terminating glaciers, and their relation to environmental forces. We show that the primary driver of calving is long-term internal glaciological stress, but as ice shelves thin they may become more vulnerable to environmental forcing. This vulnerability—and the potential for MICI—comes from a combination of the distribution of preexisting flaws within the ice and regions where the stress is large enough to initiate fracture. Although significant progress has been made modeling these processes, theories must now be tested against a wide range of environmental and glaciological conditions in both modern and paleo conditions. Ice shelves, floating platforms of ice fed by ice sheets, shed mass in a near-instantaneous fashion through iceberg calving. Most ice shelves exhibit a stable cycle of calving front advance and retreat that is insensitive to small changes in environmental conditions. Some ice shelves have retreated or collapsed completely, and in the future this could expose thick cliffs that could become structurally unstable called ice cliff instability. The potential for ice shelf and ice cliff instability is controlled by the presence and evolution of flaws or fractures within the ice. [ABSTRACT FROM AUTHOR]

Stories about a submerged land named Lyonesse abound in culture traditions of Southwest Britain and plausibly derive from memories of land loss within the Scilly Isles. We review Lyonesse stories, their links to Arthurian romances and Greek/Roman accounts of the Cassiterides, and trace their divergent evolution. From this region's history of land-sea movements and human occupation, we propose Lyonesse stories originated more than 4000 years ago when rising sea level divided a single inhabited island in the Scilly group. The comparable antiquity of similar stories is a compelling reason for supposing Lyonesse stories originated from observations of submergence encoded in cultural memories through oral traditions that endured in intelligible form for several millennia to reach us today. [ABSTRACT FROM AUTHOR]

Griggs, G., 2024. Can we make coastal communities resilient to sea-level rise? Journal of Coastal Research, 40(3), 571–576. Charlotte (North Carolina), ISSN 0749-0208. "Resilient" is a term that has gotten increasingly widespread usage in recent years as a solution or response for coastal communities to the well-documented global rise in sea level. The message that is usually conveyed seems to be that if we can make coastal communities resilient, everything will be fine and we will have solved the challenge of how to adapt to a rising sea. The federal government and some coastal state government agencies are providing grant money to encourage coastal communities to develop plans to become more resilient. This is an appropriate time to ask what would a resilient coastal community look like and can we actually make a community resilient to future sea-level rise, and if so, for how long? [ABSTRACT FROM AUTHOR]

Expansive soils pose a significant challenge in geotechnical engineering, especially in coastal areas. While research has mainly focused on their elastic properties, this study explores the overlooked aspect of inelastic subsidence during prolonged droughts, utilizing decade‐long GPS datasets from the University of Houston Coastal Center. Our findings reveal substantial subsidence, approximately one to two dm, during the summer droughts of 2018, 2020, 2022, and 2023, due to compaction within the upper 4 m of expansive soils. Inelastic subsidence constitutes roughly 10% of the total subsidence, resulting in step‐like permanent land elevation loss over time. Notably, drought‐induced subsidence is prominent in open‐field areas with expansive soils but is minor in built‐up areas or in non‐expansive soil regions. The occurrence of inelastic subsidence challenges traditional assessments of relative sea‐level rise and coastal flooding, emphasizing the need to consider it in coastal infrastructure planning for enhanced resilience against climate uncertainties. Plain Language Summary: Expansive soils, often found in coastal regions, are known for causing issues like land shifts and unstable buildings. Our research adds a new dimension: prolonged droughts can lead to significant, irreversible sinking of expansive soils, permanently lowering the elevation of open land areas. Using a decade of GPS data, we found that during droughts, these soils can sink considerably and will not fully recover. Interestingly, in developed regions where pavement covers the soils, thereby minimizing moisture loss, this sinking is observed to be minimal. In the Galveston coastal area, drought‐induced sinking can reach one to two dm, with irreversible subsidence making up about 10% of the total subsidence. This becomes a growing concern as droughts become more frequent due to climate change, especially in coastal areas. Additionally, our results suggest that current methods for estimating sea‐level rise may be missing a key factor: we have underestimated the speed at which uninhabited coastal lands are sinking because we did not account for this irreversible sinking due to droughts. Key Points: Prolonged droughts cause up 2 dm of subsidence in shallow expansive soils (<4 m deep) in Galveston, TX, 10% of which is inelasticProlonged droughts lead to notable subsidence in open fields with expansive soils, but less in built‐up areas or non‐expansive soil areasRecurring droughts lead to permanent land elevation losses in open‐field coast, possibly skewing sea‐level rise and flood risk projections [ABSTRACT FROM AUTHOR]

When the first Americans inhabited the area now known as Isla Espiritu Santo, around 12.5 and 6 ka, the sea level continuously rose. This resulted in the loss of the coastal territory and the retreat of the human population further inland. Part of the archaeological evidence of this period currently lies over the seafloor and under the seabed. Therefore, reconstructing paleoshorelines is a necessary first step toward submerged precontact archaeology and a broad understanding of the spatial context in which those human populations interacted and how the landscapes changed. Isla Espiritu Santo is of prehistoric importance as it contains numerous Paleocoastal tradition sites as early as ~12,400 Cal B.P. This research aims to reconstruct the changing shoreline positions as sea levels rose around Isla Espiritu Santo between 12.5 and 6.5 ka. We apply numerical modeling to map digital elevation models at 1 ka intervals by estimating the changes in the morphology of the seafloor according to the deposition rates and global sea‐level curve. The results show the evolution of coastal morphology and paleoshoreline's position. Three primary geoforms are proposed: (1) coastal plains, (2) tombolo, and (3) a coastal lagoon–island barrier system. This also offers insights into the physical aspect of submerged prehistoric landscapes and the possible resource exploitation options of early societies. In this research, the reconstruction of submerged landscapes seeks to contribute to the long‐term goal of locating submerged precontact sites. [ABSTRACT FROM AUTHOR]

The devastating consequences of tsunamis on coastal infrastructure have highlighted the urgent need for effective disaster risk reduction strategies. To mitigate tsunami disasters, the insurance industry plays a vital role in implementing risk transfer measures by providing financial protection against asset damage. However, the current research on catastrophe insurance policies for coastal infrastructure lacks consideration of climate change effects. It is essential to take into account the non-stationary effects of sea-level rise to develop long-term tsunami disaster mitigation measures and promote socioeconomic resilience in coastal communities. This paper aims to provide an insurance portfolio optimization framework for coastal residential buildings subjected to tsunamis considering non-stationary sea-level rise effects based on a stochastic simulation approach. A spatiotemporal probabilistic sea-level rise hazard assessment is carried out by utilizing available climate models and considering several emission scenarios. Tsunami propagation analyses under various sea-level rise cases are performed to evaluate the time-variant tsunami hazard curves based on Monte Carlo simulation. A life cycle-based stochastic insurance claim model associated with the cumulative loss of building assets is developed based on a non-stationary compound renewal process. Finally, a sample average approximation method is leveraged to estimate the optimum basic insurance premium rate by maximizing the insurer's profit under a cost-constrained insurance purchase decision of homeowners. As a case study, the proposed framework is applied to multiple municipalities situated in the tsunami-prone region of Kochi Prefecture, Japan. Sea-level rise substantially decreases the maximum profits of tsunami insurers and increases the premium rate and ruin probability. [ABSTRACT FROM AUTHOR]

The present work is an effort to expose the sedimentation rate of the Ganges–Brahmaputra (GB) tidal delta plain from the subsurface-dated sediments samples. The study reveals that the average sedimentation rates (about 2.12–4.59 mm yr−1) of the area are not as good to minimize as the estimated range of relative sea-level rise (RSLR) (1–9 mm yr−1). Moreover, the sediments cannot be distributed properly in the tidal and fluvio-tidal plains due to different anthropogenic activities like poldering and embankments. In addition, the upstream diversion of the Ganges and the Brahmaputra rivers water reduces the suspended sediment load to the downstream and consequently, the sedimentation rates. Finally, the GB tidal delta plain and its coastal area are in a vulnerable situation in consideration of sedimentation rates, RSLR, and different anthropogenic activities. Therefore, regular monitoring and evaluation is essential about sedimentation, coastal and upstream anthropogenic practices, RSLR, etc., for the implementation of effective and efficient mitigation and adaptation measures in the deltaic plains. [ABSTRACT FROM AUTHOR]

Shorelines face growing threats due to climate change and diminishing sand supply. Coastal headlands, common rocky features along coastlines, are crucial in shaping hydrodynamics and sediment transport. Yet, the influence of future climate conditions, including sea‐level rise (SLR) and intensified storm energy on complex shorelines with headlands has remained relatively unexplored. In this study, we model changes in hydrodynamics and headland bypassing under different SLR and higher storm wave scenarios. Our findings reveal the formation of circulation cells on both sides of a headland, where wave energy converges around the headland zone. Future climate conditions result in larger storm waves on the beach. However, SLR enhances nearshore currents through a landward shifting of the circulation cells, while higher storm waves intensify offshore flow currents due to the seaward movement of the cells. This effect, in turn, increases the potential for headland sediment bypassing. Plain Language Summary: Coastal headlands, prominent rocky features along open coastlines, play a crucial role in protecting nearby beaches from strong waves and erosion. They also affect how sand is exchanged between different beaches. We use a model to explore how future climate conditions including sea‐level rise (SLR) and larger storm waves influence coastal waves, littoral currents, and the transport of sand around headlands. Our findings reveal that headlands converge wave energy forming circulation flow cells. SLR results in stronger nearshore currents, driven by the landward movement of the rotating flow cells. In contrast, larger storm waves can move the rotating flow cells seaward, thereby increasing offshore current strength and the potential for sand transport around the headland. Understanding how coastal waves, flow and sediment transport change under future climate conditions will help determine coastal resilience. Key Points: The formation of circulation cells and wave energy convergence around headlands during storms reduce bottom shear stress at the beachSea‐level rise increases wave heights, currents, and bed shear stress in the nearshore because of landward shifting of the circulation cellsHigher storm waves expand the surf zone, shift circulation cells seaward, and enhance potential headland sediment bypassing [ABSTRACT FROM AUTHOR]

Coastal erosion and flooding are projected to increase during the 21st century due to sea-level rise (SLR). To prevent adverse impacts of unmanaged coastal development, national organizations can apply a land protection policy, which consists of acquiring coastal land to avoid further development. Yet, these reserved areas remain exposed to flooding and erosion enhanced by SLR. Here, we quantify the exposure of the coastal land heritage portfolio of the French Conservatoire du littoral (Cdl). We find that 30% (~40%) of the Cdl lands owned (projected to be owned) are located below the contemporary highest tide level. Nearly 10% additional surface exposure is projected by 2100 under the high greenhouse gas emissions scenario (SSP5-8.5) and 2150 for the moderate scenario (SSP2-4.5). The increase in exposure is largest along the West Mediterranean coast of France. We also find that Cdl land exposure increases more rapidly for SLR in the range of 0–1 m than for SLR in the range 2–4 m. Thus, near-future uncertainty on SLR has the largest impact on Cdl land exposure evolution and related land acquisition planning. Concerning erosion, we find that nearly 1% of Cdl land could be lost in 2100 if observed historical trends continue. Adding the SLR effect could lead to more than 3% land loss. Our study confirms previous findings that Cdl needs to consider land losses due to SLR in its land acquisition strategy and start acquiring land farther from the coast. [ABSTRACT FROM AUTHOR]

The warnings of potential climate migration first appeared in the scientific literature in the late 1970s when increased recognition that disintegrating ice sheets could drive people to migrate from coastal cities. Since that time, scientists have modeled potential climate migration without integrating other population processes, potentially obscuring the demographic amplification of this migration. Climate migration could amplify demographic change--enhancing migration to destinations and suppressing migration to origins. Additionally, older populations are the least likely to migrate, and climate migration could accelerate population aging in origin areas. Here, we investigate climate migration under sea-level rise (SLR), a single climatic hazard, and examine both the potential demographic amplification effect and population aging by combining matrix population models, flood hazard models, and a migration model built on 40 y of environmental migration in the United States to project the US population distribution of US counties. We find that the demographic amplification of SLR for all feasible Representative Concentration Pathway-Shared Socioeconomic Pathway (RCP-SSP) scenarios in 2100 ranges between 8.6-28 M [5.7-53 M]--5.3 and 18 times the number of migrants (0.4-10 M). We also project significant aging of coastal areas as youthful populations migrate but older populations remain, accelerating population aging in origin areas. As the percentage of the population lost due to climate migration increases, the median age also increases--up to 10+ y older in some highly impacted coastal counties. Additionally, our population projection approach can be easily adapted to investigate additional or multiple climate hazards. [ABSTRACT FROM AUTHOR]

Questions: What role do soil seed banks play in the resilience of coastal freshwater wetland vegetation communities? How might soil seed bank composition and similarity to standing vegetation drive changes in vegetation expression, particularly given projected changes in climate? Location: Sixty wooded coastal freshwater wetlands in southeast Queensland, Australia. Methods: We surveyed standing vegetation and investigated soil seed bank composition through an 8‐month‐long emergence experiment. Results: Soil seed bank assemblages were dominated by forb and sedge species (23% exotic), but composition varied throughout the study region. Spatial (north–south) and land‐use (urban–rural) gradients explained some variation in soil seed bank composition. Soil moisture and groundwater dependence also influenced species distributions, particularly for freshwater wetland species. The similarity of soil seed banks to standing vegetation was low. Species present in both extant and soil seed bank assemblages were commonly native wetland taxa, including one salt marsh species (Juncus kraussii). Conclusions: Projected climatic changes will likely drive changes in coastal freshwater wetland vegetation communities through increases in the frequency and intensity of disturbances (e.g., storm surge). Our results suggest that regeneration from soil seed banks could promote four potential scenarios: (1) expansion of weed communities, (2) expansion of salt marsh communities, (3) maintenance and expansion of wetland/terrestrial species, and (4) transformation to an unvegetated open water zone because of reduced regeneration success under changing conditions. These diverse vegetation futures highlight the vulnerability of wooded coastal freshwater wetlands and the need for research and management interventions to maintain their biodiversity and ecosystem services. [ABSTRACT FROM AUTHOR]

Charroux, S.; Jeanson, M.; Morisseau, S., and Pennober, G., 2024. Seasonal morphodynamics of fringing reef pocket beaches and responses to rapid vertical tectonic movements. Journal of Coastal Research, 40(1), 31–50. Charlotte (North Carolina), ISSN 0749-0208. Determining the morphological response of coastal environments to a general rise in sea level constitutes one of this century's greatest challenges. In 2018–19, Mayotte, a coral reef–fringed island in the Indian Ocean, underwent a volcanic crisis that resulted in island subsidence of up to 0.2 m. This seismo-volcanic crisis made the island an ideal workshop site to observe the response of pocket beaches to sea-level variations. Morphodynamic analyses were carried out on three beaches located on different sides of the island on a biannual basis between 2019 and 2022. Analysis of these survey data showed that the alternation between monsoon and trade winds led to a seasonal rotation of the beaches. Furthermore, the central profiles did not appear to be affected by seasonal variations. As result, they were used to characterize subsidence-related impacts. When the pre- and postsubsidence profiles were compared, morphological changes were not noticeable. However, the rise in the sea level caused by subsidence led to an increase in the frequency of spring flooding at high tide in certain areas of low-lying beaches and roads on the densely populated NE coast of the archipelago, the area most affected by this tectonic movement. [ABSTRACT FROM AUTHOR]

Quantifying carbon fluxes into and out of coastal soils is critical to meeting greenhouse gas reduction and coastal resiliency goals. Numerous 'blue carbon' studies have generated, or benefitted from, synthetic datasets. However, the community those efforts inspired does not have a centralized, standardized database of disaggregated data used to estimate carbon stocks and fluxes. In this paper, we describe a data structure designed to standardize data reporting, maximize reuse, and maintain a chain of credit from synthesis to original source. We introduce version 1.0.0. of the Coastal Carbon Library, a global database of 6723 soil profiles representing blue carbon‐storing systems including marshes, mangroves, tidal freshwater forests, and seagrasses. We also present the Coastal Carbon Atlas, an R‐shiny application that can be used to visualize, query, and download portions of the Coastal Carbon Library. The majority (4815) of entries in the database can be used for carbon stock assessments without the need for interpolating missing soil variables, 533 are available for estimating carbon burial rate, and 326 are useful for fitting dynamic soil formation models. Organic matter density significantly varied by habitat with tidal freshwater forests having the highest density, and seagrasses having the lowest. Future work could involve expansion of the synthesis to include more deep stock assessments, increasing the representation of data outside of the U.S., and increasing the amount of data available for mangroves and seagrasses, especially carbon burial rate data. We present proposed best practices for blue carbon data including an emphasis on disaggregation, data publication, dataset documentation, and use of standardized vocabulary and templates whenever appropriate. To conclude, the Coastal Carbon Library and Atlas serve as a general example of a grassroots F.A.I.R. (Findable, Accessible, Interoperable, and Reusable) data effort demonstrating how data producers can coordinate to develop tools relevant to policy and decision‐making. [ABSTRACT FROM AUTHOR]

Ghost forests consisting of dead trees adjacent to marshes are striking indicators of climate change, and marsh migration into retreating coastal forests is a primary mechanism for marsh survival in the face of global sea‐level rise. Models of coastal transgression typically assume inundation of a static topography and instantaneous conversion of forest to marsh with rising seas. In contrast, here we use four decades of satellite observations to show that many low‐elevation forests along the US mid‐Atlantic coast have survived despite undergoing relative sea‐level rise rates (RSLRR) that are among the fastest on Earth. Lateral forest retreat rates were strongly mediated by topography and seawater salinity, but not directly explained by spatial variability in RSLRR, climate, or disturbance. The elevation of coastal tree lines shifted upslope at rates correlated with, but far less than, contemporary RSLRR. Together, these findings suggest a multi‐decadal lag between RSLRR and land conversion that implies coastal ecosystem resistance. Predictions based on instantaneous conversion of uplands to wetlands may therefore overestimate future land conversion in ways that challenge the timing of greenhouse gas fluxes and marsh creation, but also imply that the full effects of historical sea‐level rise have yet to be realized. [ABSTRACT FROM AUTHOR]

Summary: Predicting the fate of coastal marshes requires understanding how plants respond to rapid environmental change. Environmental change can elicit shifts in trait variation attributable to phenotypic plasticity and act as selective agents to shift trait means, resulting in rapid evolution. Comparably, less is known about the potential for responses to reflect the evolution of trait plasticity.Here, we assessed the relative magnitude of eco‐evolutionary responses to interacting global change factors using a multifactorial experiment. We exposed replicates of 32 Schoenoplectus americanus genotypes 'resurrected' from century‐long, soil‐stored seed banks to ambient or elevated CO2, varying levels of inundation, and the presence of a competing marsh grass, across two sites with different salinities.Comparisons of responses to global change factors among age cohorts and across provenances indicated that plasticity has evolved in five of the seven traits measured. Accounting for evolutionary factors (i.e. evolution and sources of heritable variation) in statistical models explained an additional 9–31% of trait variation.Our findings indicate that evolutionary factors mediate ecological responses to environmental change. The magnitude of evolutionary change in plant traits over the last century suggests that evolution could play a role in pacing future ecosystem response to environmental change. See also the Commentary on this article by Kottler, 240: 1714–1716. [ABSTRACT FROM AUTHOR]

Mangrove forests are the dominant vegetation growing on low wooded islands, which occur in the Caribbean, Indian and Pacific Oceans. In the northern Great Barrier Reef, we map remarkable, undocumented mangrove forest extension on 10 low wooded islands in the Howick Group that collectively equates to an area of 667 000 m2 (66.7 ha). We combine extensive field survey with canopy height models derived from RPA imagery and allometric scaling to quantify above ground biomass in both old (pre-1973) and new (post-1973) forest areas. Forest expansion added approximately 10 233 tonnes of new biomass since the early 1970s. We suggest that such substantial expansion of mangrove forest has occurred within a short time span in response to changing environmental controls. These may include sea-level rise, sediment transport and deposition, cyclone impact and the development of associated reef flat sedimentary landforms including unconsolidated and lithified shingle ridges, which influence reef flat hydrodynamics. Our observations highlight the globally dynamic response of mangrove distribution and forest structure to environmental change and provide timely new estimates from understudied reef island settings. [ABSTRACT FROM AUTHOR]

One of the largest restoration programs in the world, the Comprehensive Everglades Restoration Plan (CERP) aims to restore freshwater inputs to Everglades wetlands and the Florida Bay estuary. This study predicted how the Florida Bay ecosystem may respond to hydrological restoration from CERP within the context of contemporary projected impacts of sea‐level rise (SLR) and increased future temperatures. A spatial–temporal dynamic model (Ecospace) was used to develop a spatiotemporal food web model incorporating environmental drivers of salinity, salinity variation, temperature, depth, distance to mangrove, and seagrass abundance and was used to predict responses of biomass, fisheries catch, and ecosystem resilience between current and future conditions. Changes in biomass between the current and future scenario suggest a suite of winners and losers, with many estuarine species increasing in both total biomass and spatial distribution. Notable biomass increases were predicted for important forage species, including bay anchovy (+32%), hardhead halfbeak (+19%), and pinfish (+31%), while decreases were predicted in mullet (−88%), clupeids (−55%), hardhead silverside (−15%), mojarras (−117%), and Portunid crabs (−16%). Increases in sportfish biomass included the angler‐preferred spotted seatrout (+9%), red drum (+10%), and gray snapper (+8%), while decreases included sheepshead (−40%), Atlantic tarpon (−73%), and common snook (−507%). Ecosystem resilience and fisheries catch of angler‐preferred species were predicted to improve in the future scenario in total, although a localized decline in resilience predicted for the Central Region may warrant further attention. Our results suggest the Florida Bay ecosystem is likely to achieve restoration benefits in spite of, and in some cases facilitated by, the projected future impacts from climate change due to the system's shallow depth and detrital dominance. The incorporation of climate impacts into long‐term restoration planning using ecosystem modeling in similar systems facing unknown futures of SLR, warming seas, and shifting species distributions is recommended. [ABSTRACT FROM AUTHOR]

Hybridization and introgression can promote adaptive potential and evolutionary resilience in response to increased pressures of climate change; they can also disrupt local adaptation and lead to outbreeding depression. We investigated female fitness consequences of hybridization in two sister species that are endemic to a threatened tidal marsh ecosystem: Saltmarsh (Ammospiza caudacutus) and Nelson's (Ammospiza nelsoni) sparrows. We found increasing nest flooding rates due to rising sea levels are outpacing potential adaptive benefits of hybridization due to very low overall nesting success in both the Nelson's and Saltmarsh sparrows. In the center of the hybrid zone across two years, we determined the success of 201 nests of 104 pure and admixed Saltmarsh and Nelson's Sparrow females, genotyped using a panel of single nucleotide polymorphisms (SNPs) from double digest restriction-site associated DNA (ddRAD) sequencing. We evaluated 5 metrics of female fitness and modeled nesting success in relation to genotypic, environmental, and nesting characteristics. We found differential fitness among Saltmarsh, Nelson's, and hybrid females, such that birds with predominantly Saltmarsh Sparrow alleles had higher reproductive success than birds with predominantly Nelson's Sparrows alleles, and hybrids were intermediate. Fledging success increased with two known tidal marsh nesting adaptations: nest height and nesting synchrony with tidal cycles. We found a positive relationship between hybrid index and fitness in daily nest survival in 2016, but not in 2017, likely due to differing levels of precipitation and nest flooding between years. The strongest and most consistent predictors of daily nest survival were nesting synchrony with lunar tidal flooding cycles and daily maximum tide height. Fitness patterns suggest that there may be an adaptive benefit of interspecific geneflow for the Nelson's Sparrow at the detriment of the Saltmarsh Sparrow; however, flooding rates are so high in many years they mask any fitness differences between the species, and all females had poor nesting success, regardless of genetic makeup. [ABSTRACT FROM AUTHOR]

Assessing the vulnerability of low-lying coral reef islands is a global concern due to predictions that climate and environmental change will increase reef island instability and cause reef island populations to be among the first environmental refugees. Reef islands in the Pacific and Indian Oceans are highly dynamic environments that morphologically adjust to changing environmental conditions over annual-decadal timescales. However, there is a paucity of reef island shoreline change data from the Caribbean where sea-level rise, ecological and environmental disturbance and hydrodynamic regimes are considerably different than in other oceans globally. Here we present shoreline change analysis of 16 reef islands in northern Honduras, at the southern end of the Mesoamerican Barrier Reef. Satellite imagery from a maximum period of 12.4 years from Utila (2006–2019), and 2.4 years from Cayos Cochinos (2018–2021) was analysed to quantify island shoreline change and planform morphological adjustments. We identified accretion as the dominant island behaviour in Utila, where 5 of 7 islands increased in area and 61.7% of shorelines accreted, contributing to an overall net area increase of 9.4%. Island behaviour was more variable in Cayos Cochinos, where 55.7% of shorelines eroded, 5 of 9 islands remained stable, and net island area change was insignificant (2%). Conversely, the 4 smallest Cayos Cochinos islands (all <1500 m2) experienced significant shoreline change, potentially highlighting a new size threshold for considering reef island evolution. Across both sites, reef islands demonstrated a range of modes of planform change, including lateral accretion and erosion, and migration. Consequently, we provide the first empirical evidence of the dynamic nature of Caribbean reef islands during a period coincident with sea-level rise and highlight the heterogeneous nature of reef island evolution between and within two neighbouring sites at timescales relevant for island adaptation efforts. [ABSTRACT FROM AUTHOR]

Coastal systems, globally, including wetlands, marshlands and mangrove forests, face a severe threat due to climate change and rising sea levels. The Intergovernmental Panel on Climate Change Sixth Assessment Report (IPCC AR-6) has highlighted high-stress levels in South Asian coastal systems, particularly in the Indian Ocean. Mangrove systems are particularly vulnerable and rely on peat accumulation or landward migration to survive. The rod surface elevation table marker horizon (RSET-MH) technique finds widespread usage among researchers to comprehend the response of coastal wetlands to sea-level fluctuations. However, there is a need for national-level research on mangrove response to sea-level rise and for establishing RSET stations in mangrove forests across India. Establishing comprehensive and coordinated monitoring networks for coastal wetlands is proposed to address this gap. The present study outlined the methodology adopted in setting up the first RSET-MH station in Pichavaram mangrove forest, Tamil Nadu. The estimated cost of setting up a single RSET station ranges from INR 9,000 to INR 15,000. A coordinated monitoring system for RSET stations is crucial to ensure the survival of coastal systems in the face of climate change. The study outlined a coordinated monitoring system for RSET stations across India that will help authorities develop and implement coastal climate change adaptation strategies, critical to ensure the long-term survival of mangrove systems. It would also enable researchers to comprehend how coastal wetlands have responded to sea-level fluctuations in the past and present, and identify appropriate adaptation measures to prepare for future changes. [ABSTRACT FROM AUTHOR]

Climate change risks to coastal communities may overwhelm current management strategies. The emergence of nature‐based solutions could provide alternative approaches for climate adaptation; however, studies on their public acceptability are limited. This research focuses on the human dimensions of nature‐based coastal adaptation solutions. The research sought to understand the kind of environmental changes participants were experiencing in their coastal communities of Nova Scotia and what management responses they observed being taken, if any. Online focus groups were held with coastal property owners in Nova Scotia to understand how they assess coastal risks and four approaches to nature‐based coastal adaptation: living shorelines, accommodation, retreat, and dyke realignment to make space for wetland restoration. Results revealed ongoing trust in traditional hard‐line approaches, but also interest in knowing more about nature‐based options. There was general support for living shorelines, albeit with scepticism; a concern that accommodation is just a "band‐aid" approach; resistance to retreat, despite general recognition of its future utility; and a lack of understanding of dyke realignment. The successful implementation of nature‐based coastal adaptation approaches will require more evidence of their viability, better options for financing them, and engagement with communities around the best‐fit alternatives for them. Key messages: In focus groups, coastal residents expressed needs for proof of viability and financing to enhance buy‐in to nature‐based solutions.Living shorelines were supported, but with scepticism about their effectiveness, although dyke realignment was often misunderstood.Accommodation was seen as a "band‐aid" and almost as unpopular as coastal retreat. [ABSTRACT FROM AUTHOR]

The impact of climate change and the dynamic nature of environmental conditions underscore the critical need to enhance resilience of systems and process safety considerations. The efficacy of such efforts primarily depends on how resilience is measured. Among the myriad efforts to quantify resilience, composite indicators have emerged as promising tools. However, these indicators typically employ statistical methods to derive weights for aggregation and rely on statistical homogeneity among indicators which can limit their scope and fidelity. In this study, we propose an alternative novel resilience index derived from a system's structure and the essential conditions for safe operation during and after disruptions. The proposed measure reflects the systems' ability to resist and respond to failures by addressing possibilities of impact propagation to other infrastructure systems. Moreover, it eliminates the need for weights and allows for compensability among its leading indicators. Using a case study based on the on-site wastewater treatment and disposal systems (OSTDS) in South Florida that faces increasing risks due to rising sea levels, we investigate the validity of the proposed index and perform a comparative analysis with statistically-driven measures. Furthermore, we demonstrate the adaptation of the proposed index for decision making within a generalized optimization framework. [ABSTRACT FROM AUTHOR]

Jackson, K.; Wang, P.; Pluckhahn, T.J.; Rogers, J.A., and Thompson, V.D., 2023. Stratigraphic framework, paleoenvironments, and Indigenous terraforming of inshore estuarine subbasins in Tampa Bay, Florida, U.S.A. Journal of Coastal Research, 39(5), 779–815. Charlotte (North Carolina), ISSN 0749-0208. Tampa Bay is a karst-controlled estuary system on Florida's central peninsular Gulf of Mexico coast. Although previous work has reconstructed late-Pleistocene environments (ca. 20–11.5 kya) and early marine influence (ca. 8–5.5 kya) in deeper central portions of the bay, the estuarine development of the shallow inshore subbasins remains poorly understood. Across the late Holocene, Indigenous societies terraformed the coastal strand with large volumes of estuarine mollusk shell, and these anthropogenic landforms constitute coastal barriers that partially enclose marginal tidal bayous. This study integrates sediment coring and archaeological excavations to reconstruct the Holocene estuarine evolution of four inshore subbasins within Tampa Bay. This study synthesizes sedimentological, macrofossil, and archaeological data to describe and differentiate seven sedimentary facies and 18 subfacies representing weathered Miocene limestone at the base, overlain by late-Pleistocene freshwater wetland deposits, followed by Holocene estuarine sediments and late-Holocene shell-terraformed settlements. Four stratigraphic cross-sections and >100 radiocarbon assays are utilized to interpret the sequences of inshore estuary development, situate ancient shell-bearing Native settlements within a geologic and paleoenvironmental framework, and resolve elements of mid- and late-Holocene sea-level history. [ABSTRACT FROM AUTHOR]