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Environmental gradients and complexity in coastal landscape response to sea level rise
Abstract
Relative sea-level rise (SLR) raises geomorphic base levels, displaces salt water and tidal or backwater effects inland, and changes the hydrology of aquatic and upland environments. On an all-other-things-being equal basis, we can predict some transitions associated with SLR. However, in real coastal landscapes, all other things are not equal. Factors other than sea-level influence geomorphic, hydrological, and ecological processes and controls, environmental interactions often complicate or obscure process-response relationships, and local disturbances may interrupt or overprint them. In this study relationships among coastal environments in North Carolina, USA were investigated as they respond to changes in multiple environmental gradients driven by relative sea level rise, to determine the extent to which the spatial complexity of landscape response can be explained by environmental gradients. Spatial adjacency graphs reflecting observed patterns of contiguity were derived empirically , and five key environmental gradients related to relative sea-level were identified (elevation, hydro-period, salinity, vegetation, and process regime). The spectral radius of the spatial adjacency graph indicates a complex system that on the landscape level cannot be described or modeled based on linear gradients or suc-cessional relationships. Yet, spectral graph theory measures show that the complexity of the system can be fully explained, in the aggregate, by the five identified gradients, despite some redundancy of information therein. This indicates that coastal responses to SLR should be assessed based on multiscalar, nested environmental gradients rather than a single advancing front of change or linear sequence.
... Coastal river deltas are often naturally low-lying areas close to the local mean sea-level. Changes in regional sea-levels affect coastal river delta systems geomorphologically by altering the base level, coastal erosion, and inundation, not to mention inland propagation of tidal and backwater effects [2,3]. The geomorphological response of a coastal river delta system to sea-level rise is determined by the delta system's capacity to adapt. ...
... The geomorphological response of a coastal river delta system to sea-level rise is determined by the delta system's capacity to adapt. The system is complex owing to the variety of feedbacks and changes in internal and external boundary conditions, including sediment supply, river discharge, ecological system feedbacks, subsidence, and human intervention; it is also mainly associated with hydrodynamic and ecological responses [2,4]. It influences system ...
... As a consequence of the dynamic interactions of connected nodes, the concept's state changes over time. The reasoning is performed as the calculation of Equation (1), where f ( ) stands for a hyperbolic transformation function Equation (2), ensuring that the concept defined value falls within the interval [0,1] and f ( ) is given by Equation (2), where C-parameter, C > 0. ...
The Sundarbans is the world’s largest coastal river delta and the largest uninterrupted mangrove ecosystem. A complex socio-ecological setting, coupled with disproportionately high climate-change exposure and severe ecological and social vulnerabilities, has turned it into a climate hotspot requiring well-designed adaptation interventions. We have used the fuzzy cognitive maps (FCM)-based approach to elicit and integrate stakeholders’ perceptions regarding current climate forcing, consequent impacts, and efficacy of the existing adaptation measures. We have also undertaken climate modelling to ascertain long-term future trends of climate forcing. FCM-based simulations reveal that while existing adaptation practices provide resilience to an extent, they are grossly inadequate in the context of providing future resilience. Even well-planned adaptations may not be entirely transformative in such a fragile ecosystem. It was through FCM-based simulations that we realised that a coastal river delta in a developing nation merits special attention for climate-resilient adaptation planning and execution. Measures that are likely to enhance adaptive capabilities of the local communities include those involving gender-responsive and adaptive governance, human resource capacity building, commitments of global communities for adaptation financing, education and awareness programmes, and embedding indigenous and local knowledge into decision making.
... Evidence of a climate-driven ecohydrological state change was found, for instance, in North American prairie pothole wetlands by McKenna et al. (2017), and Phillips (2018) documented state changes in coastal environments due to rising relative sea-level. The paleoecological record also records ecosystem state changes; indeed changes in vegetation composition, soils, and disturbance regimes are often interpreted as indicators of climate change (Cronin, 1999;Retallack, 2001;Bottjer, 2016). ...
... About 35 percent of the difference of the observed λ 1 value from that of a fully connected graph is attributable to the specific configuration of links; the remainder is due to m being less than the maximum for N = 6. The theoretical range of ζ wiring is 0 to asymptotically approaching 1, but the values greater than 0.5 are unlikely-the largest observed value for a graph representing pedologic, geomorphic, or ecological systems is 0.416 (Phillips, 2012;2013;2018). ...
... Because of the overlapping, interactive effects of multiple gradients, however, and the complex nature of ecosystem networks, models or assessments based on (often well established) changes along these gradients may not produce the expected results, especially locally (as opposed to broader scale, average trends). This is illustrated by studies of geomorphic responses to sea level rise (Kim et al., 2012;Phillips, 2018) and by similar phenomena in studies of, e.g., riverine landscape change in response to floods and droughts or anthropic flow modifications (Rountree et al., 2000;Van Dyke, 2016) and soil-vegetation relationships in forests (Danek et al., 2016). Other case studies are reviewed by Burkett et al. (2005). ...
Case studies of ecosystem responses to changing climates are necessary in understanding and adapting to these changes. However, more general conceptual frameworks are also needed to contextualize and synthesize case studies, and to provide guidelines for assessment and prediction. This study analyzes a network model of ecological and soil state factor interrelationships to address issues such as sensitivity, resilience, and complexity of climate-driven terrestrial ecosystem changes. A factorial ecosystem model is analyzed using techniques from algebraic graph theory. Results show high values for spectral radius, graph energy, and algebraic connectivity. These indicate complexity, dynamical instability, active reverberating feedbacks, and high synchronization. Implications are that climate effects on ecosystems will be complicated, complex, and difficult to predict. We should be prepared for surprises in the form of unanticipated pathways and outcomes. The inherent nature of ecosystem interconnectivity indicated by the state factor model also suggests that when simulation models and change assessments do turn out to be wrong, it does not necessarily mean the underlying scientific understandings, data, or assumptions are wrong, as sensitivity to relatively minor variations and disturbances is high, and complexity and low predictability are inherent. Ecosystem reactions to climate (and other, often contemporaneous) changes will reverberate through the ecosystem. Both filtering and amplification may occur, but net amplification is indicated by the graph analysis. Ecosystem responses are integrated system responses-state factors will respond as a single integrated unit, not as a collection or sequence of individual responses.
... Though in a simple, undirected graph λ1 is always positive, in a directed graph the real part of the largest eigenvalue is equivalent to the Lyapunov exponent, and therefore λ1 > 0 signifies dynamical instability. Fath (2007) used spectral radius as an indicator of complexity of ecological food webs, and Phillips (2011a;b;2012;2018) to measure complexity in soil, geomorphological, and ecological state-and-transition models. Renaud et al. (2020) applied spectral radius to study properties of plant-pollinator networks. ...
... With respect to hydrological and geomorphological phenomena, this often occurs due to gradient, resistance, and efficiency selection. Pathways with the steepest flux gradients, landscape elements with the highest resistance, and configurations with the greatest efficiency for work (consistent with the least action principle) preferentially occur, recur, growth, and survive (Hunt, 1998;2017;Huang and Nanson, 2000;Phillips, 2010;2011;Smith, 2010;Nanson and Huang, 2017;2018). ...
In Earth surface systems (ESS), everything is connected to everything else, an aphorism often called the First Law of Geography and of ecology. Such linkages are not always direct and unmediated, but many ESS, represented as networks of interacting components, attain or approach full, direct connectivity among components. The question is how and why this happens at the system or network scale. The crowded landscape concept dictates that linkages and connections among ESS components are inevitable. The connection selection concept holds that the linkages among components are advantageous to the network and are selected for and thereby preserved and enhanced. These network advantages are illustrated via algebraic graph theory. For a given number of components in an ESS, as the number of links or connections increases, spectral radius, graph energy, and algebraic connectivity increase. While the advantages (if any) of increased complexity are unclear, higher spectral radii are directly correlated with higher graph energy. The greater E(g) is associated with more intense feedback in the system, and tighter coupling among components. This in turn reflects advantageous properties of more intense cycling of water, nutrients, and minerals, as well as multiple potential degrees of freedom for individual components to respond to changes. The increase of algebraic connectivity reflects a greater ability or tendency for the network to respond in concert to changes.
... Marshland response and fluvial dynamics are important in understanding changes to estuaries from sea-level change. As discussed above, marsh landscapes can respond to sea-level change through vertical and horizontal accretion that is dependent on fluvial dynamics of water and sediment discharge, tidal effects on sediment transport, vegetation dynamics and sediment deposition and erosion ( Crosby et al. 2016;Morris et al. 2002;Phillips 2018). If a marsh is to keep pace with rising sea level, the positive vertical rate of accumulation must be greater or equal to the rate of total subsidence plus the local sea-level trend (Cahoon 2015). ...
Europe’s Lost Frontiers was the largest directed archaeological research project undertaken in Europe to investigate the inundated landscapes of the Early Holocene North Sea – the area frequently referred to as ‘Doggerland’. Funded through a European Research Council Advanced Grant (project number 670518), the project ran from 2015 to 2021, and involved more than 30 academics, representing institutions spread geographically from Ireland to China. A vast area of the seabed was mapped, and multiple ship expeditions were launched to retrieve sediment cores from the valleys of the lost prehistoric landscapes of the North Sea. This data has now been analysed to provide evidence of how the land was transformed in the face of climate change and rising sea levels.
This volume is the first in a series of monographs dedicated to the analysis and interpretation of data generated by the project. As a precursor to the publication of the detailed results, it provides the context of the study and method statements. Later volumes will present the mapping, palaeoenvironment, geomorphology and modelling programmes of Europe’s Lost Frontiers. The results of the project confirm that these landscapes, long held to be inaccessible to archaeology, can be studied directly and provide an archaeological narrative. This data will become increasingly important at a time when contemporary climate change and geo-political crises are pushing development within the North Sea at an unprecedented rate, and when the opportunities to explore this unique, heritage landscape may be significantly limited in the future.
... Geographical setting of the coastal areas of Bangladesh being low laying deltaic nature, as a results morphology always changing by coastal erosion and accretion process, and response (Brammer, 2014). Global climate change and mean sea level rise (MSL) continuously impacts on coastal morphology, ecology, and human migration (Carter, 1991;Ellison, 1994;Pethick, 2001;Feagin et al., 2005;FitzGerald et al., 2008;Rao et al., 2008;Woodruff et al., 2013;Cazenave et al., 2014;Antonioli et al., 2017;Phillips, 2018;Islam and Parvez, 2020). Climate change induced natural hazards like tropical cyclone, coastal flooding, and coastal landmass erosion have been considerably adverse impacts on socio-economy and livelihood of the coastal community. ...
Coastal morphological change and landscape dynamics have been creating a new window for taking immediate sustainable management strategies for coastal resources management. The dynamic nature of coastal morphological response includes erosion/accretion of landmass, development of an island by sedimentation, movement of the island, and change in geometry and shape. The objectives of the study illustrate morphological change, driver, and mechanism of morphological change, and the effects of morphological change on coastal landscape dynamics. The study also explores spatio-temporal landscape dynamics effects on coastal ecosystem services and livelihood pattern of the coastal community. The novelty of the present research is that how morphological change influence in response to landscape dynamics and its ecosystem services by exploring historical data including shoreline change, century scale erosion and accretion, stability of the islands since 1776 to 2021. In this study, historical maps (i.e., Rennell’s map in 1776 and Tassin map in 1840), Topographic Survey map (1943) and remotely sensed digital image (i.e., Landsat TM in 1990, 2000 and 2010, and Landsat OLI in 2021) have been used to quantify coastal geomorphological change and landscape dynamics through RS and GIS tools and techniques. The finding of the study showed remarkable change occurred in geomorphology of the Monpura Island over the period of 245 years. The spatial coverage of the island has been declined dramatically, which is quantified ∼2905 ha from 1776 to 2021. In the century scale from 1840 to 1943, erosion is observed higher than accretion, and the statistics showing that 8963.40 ha eroded along the east flank of Island. In the northern flank of the Island, Net Shoreline Movement (NSM) and the rate of shoreline movement which expressed by EPR showed highest and flowed by ∼4 km and -126.55 m/y toward landmass. During the epoch 1990–2021, because of morphological change and anthropogenic interventions, the crop land of the Island has been significantly declined by ∼38%, while the rivers and settlement spatial coverage have been increased by ∼768% and ∼153%, with an annual rate of change ∼25% and ∼5% respectively. These outcomes and prepared maps of the current research will be supportive for the local inhabitant, coastal morphologist, and environmental resources management manager, national and international policy advisor, government and non-movement stakeholder, researcher to observe coastal morpho-dynamics including shoreline dynamics, coastal erosion and accretion and its impacts on landscape and ecosystem services.
... The interior regions of the continent are likely to be impacted by rising temperatures (Dimri et al. 2018;Goes et al. 2020;Mannig et al. 2018;Schuurmans 2021). Weather patterns change due to the shortage of natural resources (water), increase in glacier melting, and rising mercury are likely to cause extinction to many planted species (Gampe et al. 2016;Mihiretu et al. 2021;Shaffril et al. 2018).On the other hand, the coastal ecosystem is on the verge of devastation (Perera et al. 2018;Phillips 2018). The temperature rises, insect disease outbreaks, health-related problems, and seasonal and lifestyle changes are persistent, with a strong probability of these patterns continuing in the future (Abbass et al. 2021c;Hussain et al. 2018). ...
Climate change is a long-lasting change in the weather arrays across tropics to polls. It is a global threat that has embarked on to put stress on various sectors. This study is aimed to conceptually engineer how climate variability is deteriorating the sustainability of diverse sectors worldwide. Specifically, the agricultural sector's vulnerability is a globally concerning scenario, as sufficient production and food supplies are threatened due to irreversible weather fluctuations. In turn, it is challenging the global feeding patterns, particularly in countries with agriculture as an integral part of their economy and total productivity. Climate change has also put the integrity and survival of many species at stake due to shifts in optimum temperature ranges, thereby accelerating biodiversity loss by progressively changing the ecosystem structures. Climate variations increase the likelihood of particular food and waterborne and vector-borne diseases, and a recent example is a coronavirus pandemic. Climate change also accelerates the enigma of antimicrobial resistance, another threat to human health due to the increasing incidence of resistant pathogenic infections. Besides, the global tourism industry is devastated as climate change impacts unfavorable tourism spots. The methodology investigates hypothetical scenarios of climate variability and attempts to describe the quality of evidence to facilitate readers' careful, critical engagement. Secondary data is used to identify sustainability issues such as environmental, social, and economic viability. To better understand the problem, gathered the information in this report from various media outlets, research agencies, policy papers, newspapers, and other sources. This review is a sectorial assessment of climate change mitigation and adaptation approaches worldwide in the aforementioned sectors and the associated economic costs. According to the findings, government involvement is necessary for the country's long-term development through strict accountability of resources and regulations implemented in the past to generate cutting-edge climate policy. Therefore, mitigating the impacts of climate change must be of the utmost importance, and hence, this global threat requires global commitment to address its dreadful implications to ensure global sustenance.
... A study of environmental gradients and complexity at the landscape scale by Phillips (2018b) was conducted in a broader region of the central NC coast, including the Neuse estuary. This study focused on state transitions among geomorphic and ecological systems and environments in response to coastal submergence. ...
In September 2018 Hurricane Florence had severe impacts on the lower Neuse River and Neuse estuary, North Carolina, despite the fact that it was a minor storm in terms of traditional indicators of storm intensity. The storm was consistent with recent trends and predictions of tropical cyclone activity driven by Anthropocene climate warming. However, its impacts in the Neuse area were also conditioned by idiosyncratic aspects of the geographic setting and the synoptic situation. Geomorphic changes examined here include erosion of estuarine shoreline bluffs, geomorphic transformations of small freshwater swamps, and effects on the river and floodplain upstream of the estuary. The shoreline changes caused by Florence were unique with respect to previous tropical cyclones and ongoing episodic erosion, due to the extraordinarily high and unusually long duration of storm surge. Transformations of the “ravine swamps”—mainly associated with deposition of >0.6 m of sand on organic muck and open water surfaces—were similarly unprecedented. Despite high river discharges (third highest on record) and the high storm surge, fluvial impacts in the lower river and fluvial-estuarine transition zone were minimal. This is attributable to the morphology of the channel-floodplain system, adapted to Holocene sea-level rise and preserved by wetlands protection programs. The large area of the storm, slow forward movement, and extreme rainfall of Florence are likely indicative of a “new normal” with respect to tropical cyclones in the region. However, the geomorphic impacts in the lower Neuse were largely determined by particulars of the Neuse estuary and Florence's storm track. An exception is the limited impacts on the lower fluvial portion of the river and the fluvial-estuarine transition zone, where there exists a complex mosaic of channels and flowing wetlands capable of accommodating extreme discharges.
... Coastal wetlands exhibit strong ecological gradients, thus providing a wide range of niches, from freshwater to saline, for species-rich flora and fauna (Phillips, 2018). It might have been this wealth of plants and animal food resources that attracted prehistoric people living in the hilly regions of the upper Qiantangjiang River to move towards the coast and spread out along the coastline. ...
The Hangzhou Bay region was home to the Shangshan complex (10,800–8600 cal BP), one of the oldest Neolithic cultural sequences in the world, and a centre of early agriculture based on intensive wet rice cultivation. The current study focuses on environmental factors that possibly influenced the developments of Neolithic cultures north and south of Hangzhou Bay and the origin of rice-based agriculture. Although the beginning of sedentary occupation of the Ningshao Plain south of Hangzhou Bay (ca. 10,800 cal BP; associated with the so-called Shangshan cultural complex) predates that of the Taihu Plain north of Hangzhou Bay (ca. 7200 cal BP) by ca. 3000 years, occupation on the Ningshao Plain gradually declined to a cultural periphery after ca. 6000 cal BP. Unstable hydrological conditions on the Ningshao Plain in response to a higher exposure to marine influence were probably the reason behind this decline. By contrast, Majiabang, Songze, and Liangzhu culture (ca. 7200–4000 cal BP) populations on the Taihu Plain were increasingly protected from marine influence by progradation of the Yangzi delta after stabilisation of the sea level around ca. 7000 cal BP. Since then, the development of wet rice-based agriculture accelerated in the context of stable wetland environments and an abundant supply of freshwater, leading to the development of the key domestication traits in rice. This highlights the importance of the mid-to late Holocene Yangzi delta evolution in shaping the development of early agriculture in the Hangzhou Bay region.
... In Mojave Desert landscapes, Pietrasiak et al. (2014) showed that biotically or abiotically-dominated evolutionary trajectories may occur, depending on bioturbation. Complex patterns of geomorphological/ecological state transitions were found in coastal landscape responses to sea-level rise by Phillips (2018a). ...
Biogeomorphological and ecological succession following a disturbance or the exposure of new ground often proceeds in stages, from domination by abiotic, geophysical factors through stages characterized by increasing effects of biota, biotic-abiotic feedbacks, and eventual domination by ecological processes. However, some studies in forest settings have found more varied development patterns, including persistence of states dominated by biogeomorphic feedbacks. In this study we investigated this phenomenon In Norway spruce (Picea abies (L.) Karst.) dominated forests on the main ridge of the Šumava Mountains in the Czech Republic along the German and Austrian borders. Throughout most of the Holocene, Picea has strongly influenced microtopography and soil/regolith characteristics so as to inhibit hydrological connectivity and development of surface drainage, and maintain hydromorphic soil conditions. These strongly historically and geographically contingent ecosystem engineering effects create and maintain habitat that favors spruce over other trees. These interactions have maintained a landscape dominated by biogeomorphic feedbacks.
... When this tipping point is reached, the site will exhibit an abrupt loss of adaptability and become more vulnerable to inundation. Dashed lines show how an additional pulse disturbance (e.g., storms) may have the potential to accelerate these trends 2012; Wang and Temmerman 2013;Brantley et al. 2014;Eslami-Andergoli et al. 2015;Kirwan et al. 2016;Philips 2018;Phillips 2018). Global sea level rise projections predict increases between 0.3 and 1.2 m by 2100 (Church et al. 2013;Kopp et al. 2014;. ...
Context
Coastal landscapes evolve in response to sea-level rise (SLR) through a variety of geologic processes and ecological feedbacks. When the SLR rate surpasses the rate at which these processes build elevation and drive lateral migration, inundation is likely.
Objectives
To examine the role of land cover diversity and composition in landscape response to SLR across the northeastern United States.
Methods
Using an existing probabilistic framework, we quantify the probability of inundation, a measure of vulnerability, under different SLR scenarios on the coastal landscape. Resistant areas—wherein a dynamic response is anticipated—are defined as unlikely (p < 0.33) to inundate. Results are assessed regionally for different land cover types and at 26 sites representing varying levels of land cover diversity.
Results
Modeling results suggest that by the 2050s, 44% of low-lying, habitable land in the region is unlikely to inundate, further declining to 36% by the 2080s. In addition to a decrease in SLR resistance with time, these results show an increasing uncertainty that the coastal landscape will continue to evolve in response to SLR as it has in the past. We also find that resistance to SLR is correlated with land cover composition, wherein sites containing land cover types adaptable to SLR impacts show greater potential to undergo biogeomorphic state shifts rather than inundating with time.
Conclusions
Our findings support other studies that have highlighted the importance of ecological composition and diversity in stabilizing the physical landscape and suggest that flexible planning strategies, such as adaptive management, are particularly well suited for SLR preparation in diverse coastal settings.
... Wetland ecosystems are completely developed in these areas because of the unique habitat conditions and provide various ecological functions (Du et al., 2011;Duarte et al., 2013;Chi et al., 2018c). However, complex land-sea interactions, including sediment deposition, coastal erosion, and rising sea level, result in a constantly changing geomorphology and high sensitivity of the estuarine ecosystem to natural disturbances (Peng et al., 2010;Xing T et al., 2016;Phillips, 2018). Estuarine areas attract numerous people because of their important geographical positions, abundant natural resources, and good ecological conditions; humans live and produce with high intensity and considerably affect the estuarine ecosystem (Liu et al., 2014bb;Chi et al., 2018a). ...
Human activities have widely spread over nearly every corner of the world and been remarkably influencing the natural ecosystem since the 20th century. Identifying and quantifying the negative and positive influences of human activities are important for providing a solid basis for reasonable exploitation and effective conservation. This study focused on the negative and positive influences of human activities on five “macro to micro” aspects of an estuarine ecosystem, including island geomorphology, landscape pattern, plant community, physical quality, and chemical environment. An evaluation model was established using spatiotemporal ecological information from remote sensing, and three new indices, namely, human damage index (HDI), human regulation index (HRI), and human net influence index (HNII), were established to quantify the negative, positive, and net influences of human activities, respectively. Chongming Island in the Yangtze River Estuary of China was used as the study area, and four scenes of remote sensing images in 1988, 1995, 2007, and 2017 served as the data source. Results indicated that HDI initially increased and then decreased, HRI showed generally increasing characteristics, and HNII initially decreased and then increased in the entire study area from 1988 to 2017. Although the net influence was negative, ecological conservation and management since the 21 st century have clearly increased the HNII. Wetland vegetation, mudflat, and woodland had positive HNII; farmland, water area, and pond had HNII close to zero; and building, traffic, and industrial lands possessed negative HNII. The model was proven to greatly contribute to judging the ecological efficiencies of different types of land uses and optimizing the spatial configuration of human activities in estuarine areas.
... Comparando, la costa de Chiapas en el Pacífico con el Golfo de México, este último tiene un mayor espacio de la planicie de inundación, hay una mayor heterogeneidad ambiental, que puede explicar la mayor diversidad de especies en humedales como la selva inundable, en relación con los que existen en la costa de Chiapas (Infante-Mata et al., 2011;López-Portillo et al., 2011;Moreno-Casasola et al., 2012a). La distribución de la vegetación y el funcionamiento de los humedales costeros en parte se explican por el gradiente de los factores ambientales como la salinidad, sin embargo, para entender las diferencias hay que considerar las características hidrogeomorfológicas de cada sitio, que se reflejan en la extensión y el ensamblaje de los ecosistemas costeros (Phillips, 2018). Sin embargo, en México, aún faltan estudios para terminar de comprender totalmente el funcionamiento en los humedales costeros. ...
Introducción:
Las características de los humedales costeros son resultado de las interacciones hidrogeomorfológicas entre el continente y el océano, que causan un gradiente ambiental, que resulta en diferentes tipos de vegetación como manglares, popales, tulares, selvas y palmares inundables.
Objetivo:
Caracterizar las variables del hidroperiodo y fisicoquímicas del agua y suelo para determinar la relación que existe en el patrón de distribución de la vegetación en el Sistema de Humedales El Castaño (SHC).
Metodología:
Se establecieron 11 unidades de muestreo (UM) permanentes por estrato definidos: cinco en el manglar, dos en selvas inundables, dos en tular y dos en pastizal inundable. De mayo 2016 a octubre 2017 se caracterizó la vegetación y se muestreó mensualmente los niveles de inundación y parámetros fisicoquímicos del agua (superficial, intersticial y subterránea): salinidad, conductividad y pH; y el suelo: densidad aparente, porcentaje de humedad y potencial redox.
Resultados:
El manglar es el más cercano al mar, tiene la menor diversidad (H:1.66) y especies registradas (14), está dominado por Laguncularia racemosa y Rhizophora mangle y tiene los valores más altos de salinidad intersticial y subterránea, mayores a 10.8 ups, se mantiene inundado de 4 a 12 meses, su potencial redox es de 14.57 mV. Seguido está el manglar, tierra adentro, se ubican los remanentes de la selva inundable, (H:2.18 y 18 especies), dominada por Pachiraaquatica, la salinidad intersticial y subterránea de 4.95 ups, permanece inundada de 0 a 6 meses y el potencial redox es de 119.07 mV. El tular, después de la selva, (H:1.92 y 16 especies), dominado por Typha domingensis, salinidad intersticial y subterránea de 6.1 ups, el tiempo de inundación es de 5 a 8 meses y potencial redox es de 125.9 mV. El pastizal inundable, con menor influencia marina, es un humedal herbáceo modificado para uso ganadero, presentó los valores más altos de diversidad (H:3.44 y 50 especies), Paspalum conjugatum es la especie dominante, la salinidad intersticial y subterránea es menor a 0.5 ups, se mantiene inundado de 5 a 9 meses y el potencial redox es de 151.23 mV.
Conclusiones:
En cada tipo de vegetación, la estructura, composición y diversidad es diferente, con un alto recambio de especies que indica un gradiente definido por la salinidad. La vegetación en el SHC sigue los patrones de organización típica de los humedales costeros tropicales, manglares, selvas inundables y humedales herbáceos, en este caso los tulares y pastizales inundables. El factor que define la distribución de la vegetación, es salinidad y el gradiente que se observa está en función de la dinámica hidrológica que depende de entradas de agua marina y de la bajada de agua dulce del interior del continente.
... Shortage of water resources, increase in glacier melting, and changing weather patterns due to rising mercury is likely to cause extinction to many planted species (Gampe et al. 2016;Shaffril et al. 2018). On the other hand, the coastal ecosystem is on the verge of devastation due to rise in sea level (Perera et al. 2018;Phillips 2018). Rise in temperature, pest-disease, health-related issues, and seasonal and lifestyle changes are obstinately occurring with a strong likelihood of persistence in these trends in the future (Hussain et al. 2018). ...
The devastations and damages caused by climate change are apparent across the globe, specifically in the South Asian region where vulnerabilities to climate change among residents are high and climate change adaptation and mitigation awareness are extremely low. Pakistan’s low adaptive capacity due to high poverty rate, limited financial resources and shortage of physical resources, and continual extreme climatic events including varying temperature, continual flooding, melting glaciers, saturation of lakes, earthquakes, hurricanes, storms, avalanches, droughts, scarcity of water, pest diseases, human healthcare issues, seasonal and lifestyle changes, have persistently threatened the ecosystem, biodiversity, human communities, animal habitations, forests, lands and oceans with a potential to cause further damages in future. The likely effect of climate change on common residents of Pakistan with comparison to the world and their per capita impact of climate change are terribly high with local animal species such as lions, vultures, dolphins, and tortoise facing extinction regardless of generating and contributing diminutively in global GHG emissions. The findings of the review suggested that GHG emissions have impacted agriculture livestock & forestry, weather trends, and patterns, food water & energy security, and society of Pakistan.This review is a sectorial evaluation of climate change mitigation and adaption approaches in Pakistan in the aforementioned sectors and its economic costs which were identified to be between 7 to 14 billion USD per annum. The research suggested that governmental interference is essential for the sustainable development of the country through strict accountability of resources and regulation implemented in the past for generating state-of-the-art climate policy.
... Apart from recent global eustatic sea-level rise and its impact on the coastal zone (Phillips, 2018) with changes around 3.4 ± 0.4 mm/year as well as accelerated future sea-level rise (Sweet et al., 2017), the CS experiences a much higher rise in sea-level, at a rate one hundred times faster than the present eustatic sea-level (Kakroodi et al., , 2014(Kakroodi et al., , 2015. This in turn results in a variety of coastal responses to rapid sealevel change. ...
The Caspian Sea (CS)is the largest enclosed inland body of water and eminent for its rapid sea-level change. From 1929 to 1955, rapid cyclic changes with amplitudes of 3 m led to the formation of large submerged and emerged areas. The present study seeks to incorporate multi-source sensor data such as the Landsat time-series data (i.e., MSS, TM, ETM+ and OLI)alongside radar altimetry products (i.e., TOPEX, Jason-1, OSTM, Jason-3)as a means for extracting morphological features (Gorgan Bay and Gomishan lagoon)of the southeastern shorelines of the Caspian Sea, as well as to investigate changes in the shoreline for a given period of 42 years (1975-2016). We also employ Particle Swarm Optimization (PSO)algorithm as an automated method to extract shoreline change in shallow marine environments. Over the past century, the CS has experienced a lowstand in 1977 and a highstand in 1995. Despite an approximate 1.5 m drop in sea-level from 1995 to 2015, Gorgan Bay and Gomishan lagoon, with depths of 4.5 and 2.5 m, appear to have outlasted and emerged, respectively. PSO is a highly efficient method capable of defining shorelines and extracting water bodies. The surface area estimations using the PSO method are consistent with corresponding reference values, with an average error of 1.73% and a high coefficient of determination (R ² = 0.99). Differences between calculated and reference areas were mainly observed in muddy and swamp sectors of the study area. This study highlights the key role of satellite time-series in shoreline monitoring and management under rapid sea-level change conditions. Moreover, the study demonstrates the capabilities of the PSO algorithm as an automated and accurate method for shoreline detection.
... In a period of 105 years (1990 to 2005) precipitation increased significantly in northern and central Asia but declined in parts of southern Asia (Hijioka et al., 2014). Climate change is proven to affect water resource scarcity as the unstable climate variability and more rapid melting of glaciers increased risk of extinction for many plant and animal species (Gampe et al., 2016;DeNicola et al., 2015) while the increasing sea level rise is proven to affect the coastal ecosystems (Perera et al., 2018;Phillips, 2018). While the impact of severe climate change on the environment continues to be recorded, climate change's impact on human beings is more severe, particularly among those who rely on environmental and climactic stability such as Asian farmers (Arouri et al., 2015). ...
Climate change in Asia is affecting farmers' daily routines. Much of the focus surrounding climate change has targeted the economic and environmental repercussions on farming. Few systematic reviews have been carried out on the social impacts of climate change among farmers in Asia. The present article set out to analyse the existing literature on Asian farmers' adaptation practices towards the impacts of climate change. Guided by the PRISMA Statement (Preferred Reporting Items for Systematic reviews and Meta-Analyses) review method, a systematic review of the Scopus and Web of Science databases identified 38 related studies. Further review of these articles resulted in six main themes - crop management, irrigation and water management, farm management, financial management, physical infrastructure management and social activities. These six themes further produced a total of 35 sub-themes. Several recommendations are highlighted related to conducting more qualitative studies, to have specific and a standard systematic review method for guide research synthesis in context of climate change adaptation and to practice complimentary searching techniques such as citation tracking, reference searching, snowballing and contacting experts.
Concentrated or preferential flow patterns occur at all scales in hydrologic systems. They shape, and are shaped by, geomorphic and pedologic patterns and structures. Preferential flow patterns in surface channel networks and dual-porosity subsurface flow systems are a way of achieiving maximum efficiency, as predicted by dissipative systems, constructal, network evolution, percolation, and ecohydrological theories. These all converge on the same predictions and interpretations of preferential flow, which satisfactorily answer “why” these patterns form and persist. However, as geomorphic and hydrologic systems have no intentionality or agency, and thus no ability to actively seek improved efficiency, how these systems evolve is an open question. I propose an emergent explanation based on five phenomena. First, concentrated flows form due to principles of gradient and resistance selection. Second, positive feedback reinforces the concentrated preferential flow paths and their relationship to potential moisture storage zones. Third, intersecting flow paths form networks. Fourth, the expansion of concentrated flow paths and networks is limited by thresholds of flow needed for channel, macropore, or conduit growth and maintenance. This results in a “store and pour” flow system that can retain water during dry periods and transport it efficiently during wet periods. These systems survive provided they develop “spillway” and/or secondary storage mechanisms to accommodate excess water inputs. Finally, store-and-pour systems are maintained (selected for) because they are often stable. Store-and-pour structures are advantageous for flow systems, and for vegetation and ecosystems. These entities cannot actively pursue goals, and no laws dictate evolution toward such patterns. Their development is an emergent phenomenon and their persistence a matter of selection, i.e., survival of the most stable.
The fluvial‐estuarine transition zone (FETZ) of the Neuse River, North Carolina features a river corridor that conveys flow in a complex of active, backflooded, and high‐flow channels, floodplain depressions, and wetlands. Hydrological connectivity among these occurs at median discharges and stages, with some connectivity at even lower stages. Water exchange can occur in any direction, and at high stages the complex effectively stores water within the valley bottom and eventually conveys it to the estuary along both slow and more rapid paths. The geomorphology of the FETZ is unique compared to the estuary, or to the fluvial reaches upstream. It has been shaped by Holocene and contemporary sea‐level rise, as shown by signatures of the leading edge of encroaching backwater effects. The FETZ can accommodate extreme flows from upstream, and extraordinary storm surges from downstream (as illustrated by Hurricane Florence). In the lower Neuse—and in fluvial‐to‐estuary transitions of other coastal plain rivers—options for geomorphological adaptation are limited. Landscape slopes and relief are low, channels are close to base level, sediment inputs are low, and banks have high resistance relative to hydraulic forces. Limited potential exists for changes in channel depth,width, or lateral migration. Adaptations are dominated by formation of multiple channels, water storage in wetlands and floodplain depressions, increased frequency of overbank flow (compared to upstream), and adjustments of roughness via vegetation, woody debris, multiple channels, and flow through wetlands.
Thresholds are ubiquitous in Earth surface systems and fundamental to landscape evolution. They occur at the level of process mechanics, and at the broader level of landscape system states, and may be fuzzy or crisp in their occurrence and/or the ability to measure or define them. Five main types of thresholds occur: force vs. resistance, storage capacities, relative rates of linked processes, saturation and depletion effects, and limiting factors. Tipping points and regime shifts are types of thresholds that occur at the landscape level (or broader) and are abrupt. As virtually all landscape systems are strongly influenced by thresholds, and many are threshold-dominated, landscapes and ESS are nonlinear, opening up possibilities for complex phenomena that do not occur in linear systems. One of these is dynamical instability, which can be both a consequence (via nonlinearity) and a cause of thresholds. Instability is a cause of thresholds in the case of system-level meta-thresholds. These are shifts in the positive or negative effects, or in the relative magnitudes, of interactions within the system. They can result in switches between dynamically stable and unstable modes, often manifested as convergent or divergent evolution.
An approach to landscape and Earth surface system evolution is outlined based on the inseparability of landform, soil, and ecosystem development, versus the traditional semi-independent treatment of geomorphic, ecological, pedological, and hydrological phenomena. Key themes are the coevolution of biotic and abiotic components of the environment; selection whereby more efficient and/or durable structures, forms, and patterns are preferentially formed and preserved; and the interconnected role of laws, place factors, and history. Existing conceptual frameworks for evolution of geomorphic, soil, ecological, and hydrological systems are reviewed and contrasted with the integrated approach.
Soil total organic carbon (TOC) and total nitrogen (TN) in estuarine areas show distinct heterogeneities in horizontal and vertical distributions due to complex influencing factors, and clarifying the horizontal and vertical distributions and their influencing factors is of great significance. In this study, the eastern Chongming Island in the Yangtze River estuary in China was selected as the study area, and the horizontal and vertical distributions of soil TOC and TN in different layers of 0–20 cm, 20–40 cm, and 40–60 cm were exhibited in maps and analyzed in different community types. Then, a total of 17 potential factors in aspects of soil, vegetation, atmosphere, landscape, and position were adopted and their single and synergistic effects on the spatial patterns of TOC and TN were identified from different perspectives. Results indicated that the mean values of TOC and TN in the entire study area decreased from surface to bottom layers. TOC and TN showed distinct spatial heterogeneities in different sampling sites and community types; they were generally high in the inner part and low in the alongshore areas in surface soils and showed opposite spatial characteristics in bottom soils; and woodland showed the highest TOC and TN in surface soils and the lowest values in bottom soils of different community types. TOC and TN in different layers, as well as the variations of TOC and TN across layers, exhibited specific and different spatial patterns under the complex factors. In soil factors, pH and available phosphorus showed the closest correlations with TOC and TN in different layers; in land surface factors, plant diversity and growth condition contributed the most to the horizontal distribution while plant growth condition and bare soil index exerted the highest influences on the vertical distribution.
The analysis of spill-over effect and mechanism is of great significance for eliminating the unbalanced development of regional energy efficiency. Our research considers the impact of external environmental factors on energy efficiency, and the spatial Durbin model is used to discover the spatial spill-over effect and mechanism. The main conclusions are as follows. (1) Eastern China is the most efficient region, central China ranks second, and west China ranks third, with a gradually descending trend in the temporal dimension. Compared to the traditional DEA model, the results removed the environmental factors to be more in line with economic intuition. (2) The spatial distribution of China's energy efficiency has a significant positive correlation from the global perspective, implying that provinces with high energy efficiency are surrounded by neighbouring provinces with high energy efficiency, and provinces with low energy efficiency are surrounded by neighbouring provinces with low energy efficiency. Provinces in each quadrant change slightly from a local perspective, indicating that energy efficiency has stable spatial correlation characteristics. (3) Neighbourhood mimicry generates a complementary effect, which promotes the spatial spill-over of energy efficiency. It is important to encourage yardstick competition and restrain lower-tier competition. (4) Industrial structure, market factors, opening-up, energy price, energy structure, and environmental regulation exert certain influences on energy efficiency.
Ecosystems at the land–sea interface are vulnerable to rising sea level. Intertidal habitats must maintain their surface elevations with respect to sea level to persist via vertical growth or landward retreat, but projected rates of sea-level rise may exceed the accretion rates of many biogenic habitats. While considerable attention is focused on climate change over centennial timescales, relative sea level also fluctuates dramatically (10–30 cm) over month-to-year timescales due to interacting oceanic and atmospheric processes. To assess the response of oyster-reef (Crassostrea virginica) growth to interannual variations in mean sea level (MSL) and improve long-term forecasts of reef response to rising seas, we monitored the morphology of constructed and natural intertidal reefs over 5 years using terrestrial lidar. Timing of reef scans created distinct periods of high and low relative water level for decade-old reefs (n = 3) constructed in 1997 and 2000, young reefs (n = 11) constructed in 2011 and one natural reef (approximately 100 years old). Changes in surface elevation were related to MSL trends. Decade-old reefs achieved 2 cm/year growth, which occurred along higher elevations when MSL increased. Young reefs experienced peak growth (6.7 cm/year) at a lower elevation that coincided with a drop in MSL. The natural reef exhibited considerable loss during the low MSL of the first time step but grew substantially during higher MSL through the second time step, with growth peaking (4.3 cm/year) at MSL, reoccupying the elevations previously lost. Oyster reefs appear to be in dynamic equilibrium with short-term (month-to-year) fluctuations in sea level, evidencing notable resilience to future changes to sea level that surpasses other coastal biogenic habitat types. These growth patterns support the presence of a previously defined optimal growth zone that shifts correspondingly with changes in MSL, which can help guide oyster-reef conservation and restoration.
Tidal marshes and the ecosystem services they provide may be at risk from sea-level rise (SLR). Tidal marsh resilience to SLR can vary due to differences in local rates of SLR, geomorphology, sediment availability and other factors. Understanding differences in resilience is critical to inform coastal management and policy, but comparing resilience across marshes is hindered by a lack of simple, effective analysis tools. Quantitative, multi-metric indices are widely employed to inform management of benthic aquatic ecosystems, but not coastal wetlands. Here, we develop and apply tidal marsh resilience to sea-level rise (MARS) indices incorporating ten metrics that contribute to overall marsh resilience to SLR. We applied MARS indices to tidal marshes at 16 National Estuarine Research Reserves across the conterminous U.S. This assessment revealed moderate resilience overall, although nearly all marshes had some indication of risk. Pacific marshes were generally more resilient to SLR than Atlantic ones, with the least resilient marshes found in southern New England. We provide a calculation tool to facilitate application of the MARS indices to additional marshes. MARS index scores can inform the choice of the most appropriate coastal management strategy for a marsh: moderate scores call for actions to enhance resilience while low scores suggest investment may be better directed to adaptation strategies such as creating opportunities for marsh migration rather than attempting to save existing marshes. The MARS indices thus provide a powerful new approach to evaluate tidal marsh resilience and to inform development of adaptation strategies in the face of SLR.
Coastal marshes are considered to be among the most valuable and vulnerable ecosystems on Earth, where the imminent loss of ecosystem services is a feared consequence of sea level rise. However, we show with a meta-analysis that global measurements of marsh elevation change indicate that marshes are generally building at rates similar to or exceeding historical sea level rise, and that process-based models predict survival under a wide range of future sea level scenarios. We argue that marsh vulnerability tends to be overstated because assessment methods often fail to consider biophysical feedback processes known to accelerate soil building with sea level rise, and the potential for marshes to migrate inland.
The magnitude of storm events is only one determinant of their geomorphic effects. The timing and sequence of storms and the initial conditions of the shoreline also exert important controls on the geomorphic impacts. Two category three hurricanes struck coastal North Carolina during the summer of 1996, Bertha in July and Fran in September, with similar wind velocities and storm surges in the Neuse River estuary. There was little evidence of wave attack on the faces of shoreline bluffs along the Neuse estuary following Bertha, but the same bluffs experienced retreat of three to 12 meters following Fran. The dominant long-term process of slope retreat is mass wasting. Bertha removed toeslope sedimentary aprons and woody debris, which absorbed the majority of the wave energy. Thus, when the second storm arrived, waves came into direct contact with the unconsolidated bluffs and initiated slope failures by undermining the lower bluffs. The effects of the the hurricanes illustrate the importance of event sequencing and initial conditions rather than energy or magnitude in determining shoreline response, and the important interactions between slope (mass wasting) and coastal processes in causing bluff retreat along the Neuse.
The lower reaches of many rivers are subject to two distinct phenomena driving aggradation: Holocene sea level rise and culturally-accelerated erosion and sedimentation. It is critical to both geoscientists and resource managers to distinguish between the effects of these phenomena, but in many situations it is difficult to distinguish between historic alluvium associated with accelerated erosion, and other Holocene fill. In the Croatan area of eastern North Carolina, there are at least five field indicators which may allow one to distinguish historic from other Holocene floodplain sediments: Development of soil B-horizons, pedological and mineralogical indicators of a Piedmont sediment source, oxidized layers, dendrogeomorphic indicators, and burial of historic features. Examination of eight stream reaches showed evidence that the surficial alluvium (~1 m or more) is historic in seven cases. Burial of historic features in the Croatan suggests mean floodplain accretion rates of 3 to 9 mm yr -1 and mass additions of 45 to 92 t ha -1 yr -1. Prehistoric mineral sedimentation rates; estimated from sediment budget considerations based on contemporary erosion and sediment transport in forested basins, were about 0.05 mm yr -1 (0.65 t ha -1 yr -1). Maximum organic accumulation rates are no more than 0.3 mm yr -1 (1.05 t ha -1 yr -1). Thus, in the Croatan, human agency has accelerated alluvial sedimentation rates by at least a hundredfold. The human-accelerated aggradation is largely confined to the lower fluvial reaches of Croatan streams. In the fluvial-estuarine transition zone, organic-dominated infilling has been little affected on a large scale by human agency. So much upland sediment is stored in alluvial floodplains that the geomorphic impacts of accelerated erosion on estuaries has been minimal.
Coastal responses to sea level rise (SLR) include inundation of wetlands, increased shoreline erosion, and increased flooding during storm events. Hydrodynamic parameters such as tidal ranges, tidal prisms, tidal asymmetries, increased flooding depths and inundation extents during storm events respond non-additively to SLR. Coastal morphology continually adapts towards equilibrium as sea levels rise, inducing changes in the landscape. Marshes may struggle to keep pace with SLR and rely on sediment accumulation and the availability of suitable uplands for migration. Whether hydrodynamic, morphologic or ecologic, the impacts of SLR are inter-related. To plan for changes under future sea levels, coastal managers need information and data regarding the potential effects of SLR to make informed decisions for managing human and natural communities. This review examines previous studies that have accounted for the dynamic, nonlinear responses of hydrodynamics, coastal morphology and marsh ecology to SLR by implementing more complex approaches rather than the simplistic “bathtub” approach. These studies provide an improved understanding of the dynamic effects of SLR on coastal environments and contribute to an overall paradigm shift in how coastal scientists and engineers approach modeling the effects of SLR, transitioning away from implementing the “bathtub” approach. However, it is recommended that future studies implement a synergetic approach that integrates the dynamic interactions between physical and ecological environments to better predict the impacts of SLR on coastal systems.
Full text available: http://onlinelibrary.wiley.com/doi/10.1002/2015EF000298/full
Micropaleontological, geophysical, and chronologic data indicate that normal salinity conditions occurred over currently estuarine back-barrier areas of the Outer Banks of eastern North Carolina during the peak of the Medieval Climate Anomaly. Sedimentary units several meters thick, containing foraminiferal assemblages usually found on the continental shelf of North Carolina, are present in 16 vibracores acquired from the shallow shoals of Pamlico Sound behind Cape Hatteras. Optically stimulated luminescence age estimates from these normal salinity units range from approximately 1360 to 980 calibrated years (cal yr) BP, corresponding with a previously documented collapse of a segment of the southern Outer Banks. It is vital to understand past scenarios of barrier island formation and segmentation to provide insight on how these islands may react to future change in climate and sea level.
Climate change is affecting world systems in many ways, of which one important dimension is sea level rise. This implication, however, has not heretofore been incorporated powerfully in analyses of biodiversity consequences of climate change, for lack of effective means of (1) modeling the degree and extent of marine intrusion into terrestrial habitats, and (2) anticipating dispersal-mediated shifts in natural systems (species, ecosystems, etc.). In this paper, recent developments in modeling marine intrusion over complex coastal landscapes are integrated with an adaptation of ecological niche modeling for estimating ‘niches’ of natural systems to anticipate sea level rise effects on them in an appropriate biological framework. This novel series of steps is illustrated with a worked example of wetlands systems and associated species and communities along the coast of North Carolina, but the methodology is novel for anticipating sea level rise-mediated shifts in vegetation types in many coastal systems.
Applications of graph theory have proliferated across the academic spectrum in recent years. Whereas geosciences and landscape ecology have made rich use of graph theory, its use seems limited in physical geography, and particularly in geomorphology. Common applications of graph theory — analyses of connectivity, path or transport efficiencies, subnetworks, network structure, system behaviour and dynamics, and network optimization or engineering — all have uses or potential uses in geomorphology and closely related fields. In this paper, we give a short introduction to graph theory and review previous geomorphological applications or works in related fields that have been particularly influential. Network-like geomorphic systems can be classified into nonspatial or spatially implicit system components linked by statistical/causal relationships and spatial units linked by some spatial relationship, for example by fluxes of matter and/or energy. We argue that, if geomorphic system properties and behaviour (e.g., complexity, sensitivity, synchronisability, historical contingency, connectivity etc.) depend on system structure and if graph theory is able to quantitatively describe the configuration of system components, then graph theory should provide us with tools that help in quantifying system properties and in inferring system behaviour.
Focusing on factors that cause relative sea-level (RSL) rise to differ from
the global mean, we evaluate RSL trajectories for North Carolina, United
States, in the context of tide gauge and geological sea-level proxy records
spanning the last $\mathord{\sim}$11,000 years. RSL rise was fastest
($\mathord{\sim}$7 mm/yr) during the early Holocene and decreased over time.
During the Common Era before the 19th century, RSL rise ($\mathord{\sim}$0.7 to
1.1 mm/yr) was driven primarily by glacio-isostatic adjustment, dampened by
tectonic uplift along the Cape Fear Arch. Ocean/atmosphere dynamics caused
centennial variability of up to $\mathord{\sim}$0.6 mm/yr around the long-term
rate. It is extremely likely (probability $P = 0.95$) that 20th century RSL
rise at Sand Point, NC, (2.8 $\pm$ 0.5 mm/yr) was faster than during any other
century in $\geq2,900$ years. Projections based on a fusion of process models,
statistical models, expert elicitation and expert assessment indicate that RSL
at Wilmington, NC, is very likely ($P = 0.90$) to rise by 42--132 cm between
2000 and 2100 under the high-emissions RCP 8.5 pathway. Under all emission
pathways, 21st century RSL rise is very likely ($P > 0.90$) to be faster than
during the 20th century. Because sea level responds slowly to climate forcing,
RSL rise in North Carolina to 2050 varies by <6 cm between pathways. Due to RSL
rise, under RCP 8.5, the current `1-in-100 year' flood is expected at
Wilmington in $\mathord{\sim}$30 of the 50 years between 2050-2100.
Sea level variations prior to the launch of satellite altimeters are estimated by analysing historic tide gauge records. Recently, a number of groups have reconstructed sea level by applying EOF techniques to fill missing observations. We complement this study with alternative methods. In a first step gaps in 178 records of sea level change are filled using the pattern recognition capabilities of artificial neural networks. Afterwards satellite altimetry is used to extrapolate local sea level change to global fields. Patterns of sea level change are compared to prior studies. Global mean sea level change since 1900 is found to be 1.77 ± 0.38 mm year−1 on average. Local trends are essentially positive with the highest values found in the western tropical Pacific and in the Indian Ocean east of Madagascar where it reaches about +6 mm year−1. Regions with negative trends are spotty with a minimum value of about −2 mm year−1 south of the Aleutian Islands. Although the acceleration found for the global mean, +0.0042 ± 0.0092 mm year−2, is not significant, local values range from −0.1 mm year−2 in the central Indian Ocean to +0.1 mm year−2 in the western tropical Pacific and east of Japan. These extrema are associated with patterns of sea level change that differ significantly from the first half of the analyzed period (i.e. 1900 to 1950) to the second half (1950 to 2000). We take this as an indication of long period oceanic processes that are superimposed to the general sea level rise.
Abrupt ecosystem regime shifts from one state to another can occur in response to environmental change (such as climate/sea level change). Detecting an approaching tipping point may help management to adapt to or mitigate the effects of catastrophic change. Intertidal wetlands are one of the most vulnerable ecosystems, faced with climate, sea level and anthropogenic changes. Early warning indicators of regime shifts that may be evident include slowing recovery rates from perturbation, increased autocorrelation and variance, changing skewness and self-organised patchiness. We examine these indicators using intertidal examples and discuss the limitations. Managers cannot adapt to or mitigate the effects of state shifts over tipping points if there is no way to detect early warning signals. This detection is highly dependent on system-specific modelling and requires understanding of alternate stable states theory and its application in large, complex ecosystems.
Smooth cordgrass Spartina alterniflora Loisel., a perennial rhizomatous grass native to the Atlantic and Gulf coasts of North America, spreads rapidly in estuaries and coastal salt marshes in the Pacific coast of North America, Europe, New Zealand and China, and has caused considerable effects on the invaded regions. We here describe a comprehensive account of its biology and ecology, and discuss the management of this invasive plant. S. alterniflora was intentionally introduced to China in 1979 for the purposes of erosion check, soil melioration and dike protection. However, its rapid elongation rates, high leaf area indices, high photosynthetic rates, long photosynthetic season and clonal growth make S. alterniflora an aggressive competitor with native salt marsh plants in the coastal regions in China. The estimates made for the year 2002 show that S. alterniflora covered 112000 hectares throughout the eastern China, from Guangxi (21º N) to Tianjin (39º N), and is still spreading rapidly in the east coast of China. The successful invasion of S. alterniflora in non-native ranges is obviously the result of the interactions between its great invading ability and a high invasibility of the invaded ecosystems, which is further facilitated by human activities. On the basis of its population trend and potential impact on native ecosystems, S. alterniflora was officially placed on the list of most harmful invasive alien plants (nine species) in China in 2003. S. alterniflora invasions in the salt marshes have multiple effects on the abiotic and biotic properties and the functioning of the invaded ecosystems, including conversion of mudflats to Spartina meadows, loss of shorebirds' foraging habitats, alteration of ecosystem processes (e.g. carbon and nitrogen cycling), decrease in abundance of native species, degradation of native ecosystems and their functions, and considerable economic loss. It is predicted that the environmental changes driven by human activities in the coastal regions (e.g. eutrophication, sea level rise and saltwater intrusion) may favour its further invasions in coastal ecosystems in the future. Like other invasive species, it is quite difficult, expensive and even impossible to eradicate S. alterniflora once it has successfully invaded the coastal ecosystems. Obviously, further intentional introductions of S. alterniflora should be banned in China, and effective control
Low-elevation bare intertidal flats and high-lying vegetated marshes are
the main components of intertidal areas of estuaries, deltas and coastal
embayments. Large-scale transitions between them have been reported
worldwide. Because vegetated marshes provide significant services to
coastal societies, predicting transitions between vegetated and
unvegetated states is of widespread importance. Previous theoretical and
modeling work highlighted the potential bistable nature of intertidal
elevations, with low-elevation bare flats and high-elevation vegetated
marshes being two alternative stable states. However, empirical evidence
of this bistable condition is limited. In this study, we tested
empirically the hypothesis that bare flats and vegetated marshes can be
considered as alternative stable landscape states with the occurrence of
rapid catastrophic shifts between them. We analyzed historical records
of intertidal elevation surveys and aerial pictures from the macrotidal
current-dominated Western Scheldt estuary (SW Netherlands). We found (1)
a bimodal distribution of intertidal elevations corresponding to either
a completely bare state or a densely vegetated state. (2) The shift from
bare to vegetated state is accompanied with a relatively rapid shift in
elevation, i.e., the mean accretion rate during the shift is 2 to 8
times larger than during the equilibrium state. (3) A threshold
elevation could be identified above which the shift from bare to
vegetated state has a high chance to occur. Hence, our results
demonstrate the abrupt nonlinear shift between low-lying bare flats and
high-elevation vegetated marshes, suggesting that the occurrence of
catastrophic shifts between alternative stable states is indeed a
potential mechanism in intertidal systems.
The Everglades of south Florida is a patterned peatland that has undergone major hydrologic modification over the last century, including both drainage and impoundment. The Everglades ridge and slough patterns were originally characterized by regularly spaced elevated ridges and tree islands oriented parallel to water flow through interconnected sloughs. Many areas of the remaining Everglades have lost this patterning over time. Historical aerial photography for the years 1940, 1953, 1972, 1984, and 2004 provides source data to measure these changes over six decades. Maps were created by digitizing the ridges, tree islands, and sloughs in fifteen 24 km2 study plots located in the remaining Everglades, and metrics were developed to quantify the extent and types of changes in the patterns. Pattern metrics of length/width ratios, number of ridges, and perimeter/area ratios were used to define the details and trajectories of pattern changes in the study plots from 1940 through 2004. These metrics characterized elongation, smoothness, and abundance of ridges and tree islands. Hierarchical agglomerative cluster analysis was used to categorize these 75 maps (15 plots by 5 years) into five categories based on a suite of metrics of pattern quality. Nonmetric multidimensional scaling, an ordination technique, confirmed that these categories were distinct with the primary axis distinguished primarily by the abundance of elongated ridges in each study plot. Strong patterns like those described historically were characterized by numerous, long ridges while degraded patterns contained few large, irregularly shaped patches. Pattern degradation usually occurred with ridges fusing into fewer, less linear patches of emergent vegetation. Patterning improved in some plots, probably through wetter conditions facilitating expression of the underlying microtopography. Trajectories showing responses of individual study plots over the six decades indicated that ridge and slough patterns can degrade or improve over time scales of a decade or less. Changes in ridge and slough patterns indicate that (1) patterns can be lost quickly following severe peat dryout, yet (2) patterns appear resilient at least over multi-decadal time periods; (3) patterns can be maintained and possibly strengthened with deeper water depths, and (4) the sub-decadal response time of pattern changes visible in aerial imagery is highly useful for change detection within the landscape. This analysis suggests that restoration of some aspects of these unique peatland patterns may be possible within relatively short planning time frames. Use of aerial photography in future Everglades restoration efforts can facilitate restoration and adaptive management by documenting sub-decadal pattern changes in response to altered hydrology and water management.
A positive relationship between interannual sea level and plant growth is thought to stabilize many coastal landforms responding to accelerating rates of sea level rise. Numerical models of delta growth, tidal channel network evolution, and ecosystem resilience incorporate a hump-shaped relationship between inundation and plant primary production, where vegetation growth increases with sea level up to an optimum water depth or inundation frequency. In contrast, we use decade-long measurements of Spartina alterniflora biomass in seven coastal Virginia (USA) marshes to demonstrate that interannual sea level is rarely a primary determinant of vegetation growth. Although we find tepid support for a hump-shaped relationship between aboveground production and inundation when marshes of different elevation are considered, our results suggest that marshes high in the intertidal zone and low in relief are unresponsive to sea level fluctuations. We suggest existing models are unable to capture the behavior of wetlands in these portions of the landscape, and may underestimate their vulnerability to sea level rise because sea level rise will not be accompanied by enhanced plant growth and resultant sediment accumulation.
The spatial and temporal complexity of earth surface processes and landforms and the presence of deterministic chaos in many fundamental physical processes provide reasons to suspect chaos in geomorphic systems. A method is presented to assess the likelihood of chaotic behavior in a geomorphic system. The method requires identification of the fundamental system components, their positive, negative, or negligible influences on each other, and the relative strength or magnitudes of these links. Based on this information, the method can classify geomorphic systems as stable and nonchaotic, unstable and potentially chaotic, or unstable and generally chaotic. Positive, self-enhancing feedback is a key diagnostic of the likelihood of chaotic behavior. A sample application of the method to the problem of coastal marsh response to sea level rise is provided, which shows the marsh to be unstable. If changes in vegetation cover are partly dependent on vegetation density, the system is generally chaotic if marsh vegetation exhibits self-enhancing feedback (for example, seed source effects) and potentially chaotic if vegetation exhibits self-limiting feedback (competitive effects). The attractors controlling the chaotic dynamics represent states of pronounced erosion/drowning or accretion/expansion.
Coastal and marine sedimentary archives are sometimes used as indicators of changes in continental sediment production and fluvial sediment transport, but rivers crossing coastal plains may not be efficient conveyors of sediment to the coast. Where this is the case, changes in continental sediment dynamics are not evident at the river mouth. Stream power is typically low and accommodation space high in coastal plain river reaches, resulting in extensive alluvial storage upstream of estuaries and correspondingly low sediment loads at the river mouth. In some cases there is a net loss of sediment in lower coastal plain reaches, so that sediment input from upstream exceeds yield at the river mouth. The lowermost sediment sampling stations on many rivers are too far upstream of the coast to represent lower coastal plain sediment fluxes, and thus tend to overestimate sediment yields. Sediment which does reach the river mouth is often trapped in estuaries and deltas. Assessment of sediment flux from coastal plain rivers is also confounded by the deceptively simple question of the location of the mouth of the river. On low-gradient coastal plains and shelves, the location of the river mouth may have varied by hundreds of kilometers due to sea-level change. The mouth may also differ substantially according to whether it is defined based on channel morphology, network morphology, hydrographic or hydrochemical criteria, elevation of the channel relative to sea level, or the locus of deposition. Further, while direct continent-to-ocean flux may be very low at current sea-level stands, sediment stored in estuaries and lower coastal plain alluvium (including deltas) may eventually become part of the marine sedimentary package. The role of accommodation space in coastal plain alluvial sediment storage has been emphasized in previous work, but low transport capacity controlled largely by slope is also a crucial factor, as we illustrate with examples from Texas.
The Outer Banks barrier islands of North Carolina, USA, contain a geologic record of inlet activity that extends from ca. 2200calyr BP to the present, and can be used as a proxy for storm activity. Optically stimulated luminescence (OSL) dating (26 samples) of inlet-fill and flood tide delta deposits, recognized in cores and geophysical data, provides the basis for understanding the chronology of storm impacts and comparison to other paleoclimate proxy data. OSL ages of historical inlet fill compare favorably to historical documentation of inlet activity, providing confidence in the technique. Comparison suggests that the Medieval Warm Period (MWP) and Little Ice Age (LIA) were both characterized by elevated storm conditions as indicated by much greater inlet activity relative to today. Given present understanding of atmospheric circulation patterns and sea-surface temperatures during the MWP and LIA, we suggest that increased inlet activity during the MWP responded to intensified hurricane impacts, while elevated inlet activity during the LIA was in response to increased nor'easter activity. A general decrease in storminess at mid-latitudes in the North Atlantic over the last 300yr has allowed the system to evolve into a more continuous barrier with few inlets.
Sea-level rise is pushing freshwater tides upstream into formerly non-tidal rivers. This tidal extension may increase the area of tidal freshwater ecosystems and offset loss of ecosystem functions due to salinization downstream. Without considering how gains in ecosystem functions could offset losses, landscape-scale assessments of ecosystem functions may be biased toward worst-case scenarios of loss. To stimulate research on this concept, we address three fundamental questions about tidal extension: Where will tidal extension be most evident, and can we measure it? What ecosystem functions are influenced by tidal extension, and how can we measure them? How do watershed processes, climate change, and tidal extension interact to affect ecosystem functions? Our preliminary answers lead to recommendations that will advance tidal extension research, enable better predictions of the impacts of sea-level rise, and help balance the landscape-scale benefits of ecosystem function with costs of response.
Estuaries contain vital habitats and it is important to understand how these areas respond to human activities and natural processes such as sea-level rise and wave attack. As estuarine shorelines erode or become modified with hard structures, there is potential for significantly altering the availability of sediment and the filling of coastal systems. This study used a source-to-sink approach and quantified rates of shoreline erosion in the Tar-Pamlico sub-estuary, a tributary of the larger Albemarle-Pamlico Estuarine System (APES). The average shoreline change rate (SCR) determined using an end-point method was -0.5 ± 0.9 m yr⁻¹ for the Tar-Pamlico. Incorporating bulk density estimates, this contributes 0.6 × 10⁵ tons of fine sediment to the system annually, or after accounting for fluvial input, about 40% of the total sediment supply to the sub-estuary. The role of the Tar-Pamlico as a sink for these sediments was addressed using the radionuclide tracers ²¹⁰Pb and ¹³⁷Cs. Radionuclide activities and sediment accumulation rates identified several depositional regions, in particular in the middle of the estuary. Linear sediment accumulation rates ranged from 0.10 ± 0.02 to 0.38 ± 0.02 g cm⁻² yr⁻¹, and total storage of fine sediment in the system was 1.6 × 10⁵ t yr⁻¹. It was not possible to confidently discern a change in the rate of shoreline erosion or seabed accumulation. A preliminary budget for fine sediments (grain-size <63 μm) was then calculated to compare erosional sources with sedimentary sinks. Almost all (∼93.0%) of the fine sediment entering the system was accumulated and stored, while only about 7.0% was exported to Pamlico Sound.
The relationship between erosion and shoreline configuration was investigated along the New Jersey shore of Delaware Bay. During a period of intense erosion and shoreline retreat the irregularity and complexity of the shoreline configuration, as measured by the fractal dimension, increased significantly. -from Author
Geomorphic system resilience is often perceived as an intrinsic property of system structure and interactions but is also related to idiosyncratic place and history factors. The importance of geographical and historical circumstances makes it difficult to generate categorical statements about geomorphic resilience. However, network-based analyses of system structure can be used to determine the dynamical stability (= resilience) based on generally applicable relationships and to determine scenarios of stability or instability. These provide guidelines for assessing place and history factors to assess resilience. A model of coastal wetlands is analyzed, based on interactions among relative sea level, wetland surface elevation, hydroperiod, vegetation, and sedimentation. The system is generally (but not always) dynamically unstable and non-resilient. Because of gradients of environmental factors and patchy distributions of microtopography and vegetation, a coastal wetland landscape may have extensive local variations in stability/resilience and in the key relationships that trigger instabilities. This is illustrated by a case study where dynamically unstable fragmentation is found in two nearby coastal wetlands in North Carolina's Neuse River estuary—Otter Creek Mouth and Anderson Creek. Neither is keeping pace with relative sea level rise, and both show unstable state transitions within the wetland system; but locally stable relationships exist within the wetland systems.
Tidal freshwater forested wetlands (TFFW) of the southeastern United States are experiencing increased saltwater intrusion mainly due to sea-level rise. Inter-annual and intra-annual variability in forest productivity along a salinity gradient was studied on established sites. Aboveground net primary productivity (ANPP) of trees was monitored from 2013 to 2015 on three sites within a baldcypress (Taxodium distichum) swamp forest ecosystem in Strawberry Swamp on Hobcaw Barony, Georgetown County, South Carolina. Paired plots (20 × 25-m) were established along a water salinity gradient (0.8, 2.6, 4.6 PSU). Salinity was continuously monitored, litterfall was measured monthly, and growth of overstory trees ⩾10 cm diameter at breast height (DBH) was monitored on an annual basis. Annual litterfall and stem wood growth were summed to estimate ANPP. The DBH of live and dead individuals of understory shrubs were measured to calculate density, basal area (BA), and important values (IV). Freshwater forest communities clearly differed in composition, structure, tree size, BA, and productivity across the salinity gradient. The higher salinity plots had decreased numbers of tree species, density, and BA. Higher salinity reduced average ANPP. The dominant tree species and their relative densities did not change along the salinity gradient, but the dominance of the primary tree species differed with increasing salinity. Baldcypress was the predominant tree species with highest density, DBH, BA, IV, and contribution to total ANPP on all sites. Mean growth rate of baldcypress trees decreased with increasing salinity, but exhibited the greatest growth among all tree species. While the overall number of shrub species decreased with increasing salinity, wax myrtle (Morella cerifera) density, DBH, BA, and IV increased with salinity. With rising sea level and increasing salinity levels, low regeneration of baldcypress, and the invasion of wax myrtle, typical successional patterns in TFFW and forest health are likely to change in the future.
Soil diversity and complexity is influenced by a variety of factors, and much recent research has been focused on interpreting or modeling complexity based on soil-topography relationships, and effects of biogeomorphic processes. We aimed to (i) describe local soil diversity in one of the oldest forest reserves in Europe, (ii) employ existing graph theory concepts in pedocomplexity calculation and extend them by a novel approach based on hypothesis testing and an index measuring graph sequentiality (the extent to which soils have gradual vs. abrupt variations in underlying soil factors), and (iii) reveal the main sources of pedocomplexity, with a particular focus on geomorphic controls.
Climate-driven shifts in environmental conditions can transform the structure and function of coastal ecosystems. Here we examine how two back-barrier brackish marshes in Pamlico Sound (North Carolina, USA) responded to changes in precipitation, temperature, and relative sea level and whether local rates of accretion have kept pace with relative sea-level rise. We used the distribution of seeds in sediment cores, coupled with 210Pb-sediment geochronology, to determine patterns of community and ecosystem change over the past century. The chronologies demonstrate that both marshes recently transitioned from communities dominated by Cladium jamaicense, which prefers fresh and brackish settings, to communities dominated by Schoenoplectus americanus, which prefers brackish and saline environments. Multiple regression analysis indicates that community shifts are best explained by relative sea-level rise and regional trends in precipitation. Results also indicate that the marshes are developing an elevation deficit with respect to rising sea level, which likely influenced the conversion from C. jamaicense dominated to S. americanus dominated communities. These findings substantiate a growing body of evidence indicating that climate-driven shifts in environmental conditions are transforming coastal ecosystems and suggest that brackish intertidal marshes may become increasingly threatened by accelerated sea-level rise and associated environmental changes expected to unfold this century.
This study examines the Holocene stratigraphic record and paleoenvironmental evolution of a large estuarine system, at high temporal and spatial resolution, in the context of changing climate, sea level, and hydrodynamics. New data are used to examine two time periods of increased marine influence within Pamlico Sound in northeastern North Carolina interpreted to be the result of extensive barrier island segmentation synchronous with periods of rapid climate change during the late Holocene. The study reveals the controls on the stratigraphic development and the highly dynamic character of the coastal system in response to climate, and sea-level change as it interacts with paleotopography. These findings can be used to inform projections of future environmental changes.
Foraminiferal, sedimentological, geophysical, and geochronologic data were utilized to elucidate the late Quaternary geologic development of the Croatan Beach Ridge Complex (CBRC), Bogue Sound, and Bogue Banks, North Carolina, USA. The CBRC is a relict beach ridge feature located on the mainland. It is separated from the modern barrier island, Bogue Banks, by Bogue Sound. Seventeen cores along shore-normal and shore-parallel transects provided material for sedimentologic and foraminiferal analysis and resulted in the recognition of seven depositional facies representing a variety of coastal depositional environments.
Since the period of agriculture began about 300 years ago, sedimentation rates have greatly increased, resulting in an alluvial progradational sequence advancing over the older sediment. Much of the older marshland has been buried by a modern forested flooplain and new marshland has appeared down-stream from the older marshes as a result of estuarine shoaling. -from Author
The barrier system moves as a whole, so that the sediment balance is relative to the moving shoreline (Lagrangian grid). Application of a continuity model to the budget suggests that, in places, the barrier system is supplied with sand from the shelf. -from Authors
The literature often holds that, in salt marshes, surface elevation mediates the depth, duration, and frequency of submergence, thereby constituting the fundamental factor of plant species distribution and most other environmental variables. However, such an elevation-centered view has not been fully tested in a temporal sense; it is still unclear whether elevation is also a significant control on the rate of changes in species composition over time. In the Skallingen salt marsh of the Danish Wadden Sea, this question was evaluated along two elevation gradients where distinct physical and ecological processes operate: a gradient across a marsh platform and the other across creek bars. The rate of vegetation dynamics was measured as the Euclidean distance between two positions of the same plot, each representing two different points in time, in a two-dimensional diagram produced by nonmetric multidimensional scaling. Results showed that the rate of vegetation dynamics did not show any significant relationships with surface elevation across either marsh platform or tidal creeks (R
2 less than 0.04). This suggests that, other than elevation, some biological factors, such as the presence of keystone species and the initial species composition, control patterns of vegetation change in the marsh. This logic leads to a point that hydrological effects (e.g., inundation frequency and duration), often represented by surface elevation, are not necessarily overriding factors of rates of changes in species composition in backbarrier marshes like Skallingen. The conventional elevation-centered perspective may be an oversimplification of the biological and environmental variability of salt marshes.
Moran, K.L.; Mallinson, D.J.; Culver, S.J.; Leorri, E., and Mulligan, R.P., 2015. Late Holocene evolution of Currituck Sound, North Carolina, USA: Environmental change driven by sea-level rise, storms, and barrier island morphology. The Holocene evolution of Currituck Sound, North Carolina, is investigated using geological data and a hydrodynamic model to understand how this depositional basin changed in response to sea-level rise and regional climate patterns. Five depositional units (one Pleistocene and four Holocene) are defined based on geophysical surveys, lithofacies, biofacies, and geochronological data. The earliest Holocene unit (ca. 5000 cal YBP) represents a midsalinity (10–25‰) sand shoal above the transgressive ravinement surface. This unit is overlain, successively, by (1) a freshwater swamp forest deposit, (2) a relatively saline (25–35‰) back-barrier estuarine deposit associated with increased inlet activity, and (3) a mid- to low-salinity (<10‰) deposit that is typical of modern (post-1827) Currituck Sound, a back-barrier estuary with no inlets in the barrier island. Geomorphic reconstructions provided the boundary conditions input to hydrodynamically model tide and current patterns and to constrain the probable size and location of inlets. The evolution of this system depends on sea-level rise and barrier morphology, regional hydrological factors, and regional climatic conditions, which modulate storm impacts and inlet activity along the fronting barrier system. The late Holocene stratigraphy reflects climate variability also recorded in the sediments of Chesapeake Bay (to the north) and Pamlico Sound (to the south) and is consistent with an increase in tropical cyclone activity during the Medieval Climate Anomaly and subsequent decrease in tropical storm activity since ca. 500 cal YBP.
Zonal patterns of salt marsh plants and physical conditions have been addressed primarily across the elevation gradient from inland to coastline rather than across tidal creeks in relation to their hydro-geomorphic processes such as bar formation and bank erosion. We found at a Danish marsh that by shaping major geomorphic features and providing sediments to the adjacent sites, fluvial-geomorphic processes of tidal creeks exert fundamental controls on the cross-channel distribution of abiotic and biotic factors. These results point to a need for biogeomorphic and landscape ecological perspectives to fully understand the underlying structure and geographic variability in salt marshes.
Patterned landscapes are often evidence of biotic control on geomorphic processes, emerging in response to coupled ecosystem processes acting at different spatial scales. Self-reinforcing processes at local scales expand patches, while self-inhibiting processes, operating at a distance, impose limits to expansion. In Big Cypress National Preserve (BICY) in southwest Florida, isolated forested wetland depressions (cypress domes) appear to be evenly distributed within a mosaic of short-hydroperiod marshes and pine uplands. To test the hypothesis that the apparent patterning is regular, we characterized frequency distributions and spatial patterns of vegetation communities, surface and bedrock elevation, and soil properties (thickness and phosphorus content). Nearest neighbor distances indicate strongly significant wetland spatial overdispersion, and bedrock elevations exhibited periodic spatial autocorrelation; both observations are consistent with regular patterning. Bedrock elevations and soil P were clearly bimodal, suggesting strong positive feedbacks on wetland patch development. Soil-surface elevations exhibited weaker bimodality, indicating smoothing of surface morphology by some combination of sediment transport, mineral reprecipitation, and organic matter production. Significant negative autocorrelation of bedrock elevations at scales similar to wetland spacing suggest the presence of distal negative feedbacks on patch expansion. These findings support the inference of regular patterning, and are consistent with the presence of local positive feedbacks among hydroperiod, vegetation productivity and bedrock dissolution. These processes are ultimately constrained by distal negative feedbacks, potentially induced by landscape scale limitations on the water volume required to enable this biogeomorphic mechanism. This article is protected by copyright. All rights reserved.
Most of the coastal wetlands of the South Atlantic region of the United States are expected to diminish in size in response to increasing human population growth and accelerating rates of rising sea level. after examination of the distribution of wetlands, elevation contours, estimates of surface slope, soil types, and peat deposits on the peninsula, current models were considered unsuited for wetlands of the Albemarle-Pamlico peninsula of North Carolina. Some unusual features of this peninsula are low elevation (56% of total area
Salt marshes are valuable yet fragile ecosystems, disappearing globally at an alarming rate. Facing this crisis, it becomes increasingly important to understand what forces drive their formation. Previous studies of marsh ontogeny relied on stratigraphy and physical monitoring, depending on inferences from multi-century and daily time scales, respectively. In this study, vertical accretion rates are evaluated at the same time resolution as a marsh’s lateral expansion, providing the fi rst comprehensive view of a laterally expanding marsh’s sedimentary trajectory. 210Pb-derived (half-life, t1/2, of 22.3 yr) accretion rates are examined in a marsh at the Newport River (North Carolina, United States), a location experiencing ongoing emergence of new marshland over the past century. Accretion rates at all marsh sampling sites begin with slow sedimentation characteristic of the bay bottom, then shift to rapid, persistent sedimentation, eventually progressing from submerged mudfl at to marsh table. Acceleration of vertical accretion occurs asynchronously across the marsh and prior to vegetative colonization, indicating a physical mechanism. We hypothesize that extant marsh tables act as promontories, effectively shielding adjacent mudfl ats from erosive forces, dictating the trajectory of marsh emergence, and yielding the pattern of alongshore marsh emergence at the Newport River.
The two barrier-island systems of North Carolina responded to the storm waves and surges of Hurricane Ginger in a strikingly different manner. Within the northern sector, which has been stabilized by man, erosion and dune recession were extensive. In the southern sector, as yet relatively unmodified, overwash and associated deposition were the dominant processes. This difference offers important geologic, ecologic, and land management implications.
Ecological network analysis allows for an investigation of the structural and functional interconnectedness in ecosystems. Typically, these interactions are seen to comprise a food web of “who eats whom”, but more generally applies to the transfer of energy-matter within the biotic and abiotic ecosphere. This web of transactions can be depicted as a digraph or an adjacency matrix in which the presence of direct transactions are represented as a 1 and no transactions as 0. Each transaction between system components leads to an overall network structural pattern. These structures cluster into different categories or regimes based on their cyclic nature. This paper demonstrates threshold effects of the placement or removal of links, such that certain changes essentially keep the structure in the same regime whereas others shift it to another regime in a non-linear manner.
Effects of environmental change may be either amplified and facilitated, or constrained, by the network of state-changes in ecological systems. Network structure affects system response independently of the dynamics of the individual subsystems. Ecological responses were represented as state-and-transition models (STMs), and analyzed as mathematical graphs. Three metrics were applied that reflect: (1) the extent to which environmental change is amplified or filtered by state transitions; (2) network synchronizability and the rate of propagation of state changes; and (3) the extent of system structural constraints to the spatial propagation of state transitions. These were determined for seven archetypal graph structures representing common forms of connectivity in ecological networks, and linked to distinct modes of ecological change. Radiation-type structures are the least synchronized and most constrained patterns, with the most limited amplification, followed by other low-connectivity patterns such as those associated with monotonic succession. The maximum-connectivity rigid polygon structure (any state can transition to any other) has the strongest amplification and synchronization and least constraints. Structural constraints to change propagation are most sensitive to increasing numbers of transitions for a given number of states, and synchronization also increases at least linearly with the number of links. Amplification, however, does not increases as rapidly; as long as a graph is connected, increasing the number of links does not proportionally increase it. Because the more densely connected structures have much higher synchronization than other patterns, and fewer constraints on change propagation, environments characterized by these types of STMs may be prone to rapid, complex transitions in response to environmental changes. STMs for rangelands in two regions of Texas show that the rigid polygon structure is very common. If this phenomenon is more general, it suggests that relatively abrupt landscape reorganizations may be more likely than more orderly successions of change along environmental gradients. This analysis shows that identification of STMs and their network structure is useful for recognizing environments at higher risk for complex reorganization, and for identification of management actions to either retard or facilitate propagation of state changes.
After establishing its present location around 9.5 ka, Mustang Island aggraded, stacking over 20 m of barrier-island sand in the same location. Throughout Mustang Island's history, tidal inlets shifted within nearly the same location from 7.5 ka to the present, leaving 10–15 m thick deposits of clean, well-sorted, quartz sand deposited within only a few centuries. These deposits lack some of the sedimentary features normally associated with tidal inlets, such as tidal couplets and shell hash. The lack of such features is attributed to the uniform nature of the deposits cut by the inlets during the island's relatively long period of aggradation. Mustang Island was able to maintain an aggradation character throughout most of the Holocene due to the sediment eroded from three sources: Pleistocene headlands, the transgressive Colorado River delta of Texas, and the OIS 3 shoreline of the central-Texas shelf. Each of these sources was exposed to waves and accompanying longshore drift during the island's early history when sea level rose quickly, but was flooded or capped by transgressive muds by the time sea-level rise slowed during the middle Holocene.
Computer analysis of aerial photographic series demonstrates that the estuarine shorelines within the North Carolina Albemarle-Pamlico coastal system are eroding at 2-3 times greater rates than previous studies reported. Specific rates and amounts of shoreline recession vary tremendously depending upon local variables including: 1) shoreline type, geometry, and composition; 2) geographic location, size, and shape of associated estuary; 3) frequency, intensity, and fetch of storms; 4) type and abundance of associated vegetation; and locally 5) boat wakes. Organic or wetland shorelines (marsh and swamp forest) comprise approximately 62% of the estuarine margins in NE NC, whereas sediment banks (low, high, and bluff) constitute about 38%. The goals of this study were to determine the rates of recession for different shoreline types and the role of local variables in the erosion process. Shorelines were mapped using high precision GPS mapping techniques, digital orthographic quarter quadrangles, and other georeferenced aerial photographs from the early 1950's to 2001. Shoreline change was then calculated for 20 estuarine study sites. Field mapping of each site provided data on shoreline characteristics and erosional processes. Data synthesis suggests mean annual shoreline erosion rates are significantly different for shoreline types as follows: 1) marshes = 7.4 ft/yr (range 2.7-17.0 ft/yr), low sediment banks = 5.0 ft/yr (range 1.0-12.0 ft/yr), bluff sediment banks = 5.0 ft/yr (range = 3.9-6.0 ft/yr), swamp forests = 3.0 ft/yr (range = 1.7-4.0 ft/yr), high sediment banks = 2.8 ft/yr (range = 2.7-2.9 ft/yr). Modified shorelines continue to erode, however at lower mean annual rates that range from 0.9-2.7 ft/yr. Locally, specific marsh shorelines have eroded at rates up to 100 ft/yr during particularly stormy periods. Thus, about 1166 acres of land are lost each year along the 1593 miles of mapped estuarine shoreline in NE NC. If these erosion rates are representative of all 3,000 miles of NE NC's estuarine shorelines, if sea level continues to rise, and if the storm pattern persists at present levels, NC will experience significant loss of both wetlands and uplands at the estuarine water-land interface.
State-and-transition models (STMs) can represent many different types of landscape change, from simple gradient-driven transitions to complex, (pseudo-) random patterns. While previous applications of STMs have focused on individual states and transitions, this study addresses broader-scale modes of spatial change based on the entire network of states and transitions. STMs are treated as mathematical graphs, and several metrics from algebraic graph theory are applied—spectral radius, algebraic connectivity, and the S-metric. These indicate, respectively, the amplification of environmental change by state transitions, the relative rate of propagation of state changes through the landscape, and the degree of system structural constraints on the spatial propagation of state transitions. The analysis is illustrated by application to the Gualalupe/San Antonio River delta, Texas, with soil types as representations of system states. Concepts of change in deltaic environments are typically based on successional patterns in response to forcings such as sea level change or river inflows. However, results indicate more complex modes of change associated with amplification of changes in system states, relatively rapid spatial propagation of state transitions, and some structural constraints within the system. The implications are that complex, spatially variable state transitions are likely, constrained by local (within-delta) environmental gradients and initial conditions. As in most applications, the STM used in this study is a representation of observed state transitions. While the usual predictive application of STMs is identification of local state changes associated with, e.g., management strategies, the methods presented here show how STMs can be used at a broader scale to identify landscape scale modes of spatial change.
The response of coastal marshes to relative sea-level rise depends upon their ability to maintain their relative elevation through sedimentation. However, sediment supply and vegetation factors are in turn susceptible to alterations in marsh hydrology and flooding. Assessment of the viability of a marsh to survive various sea-level rise scenarios may best be achieved through ecosystem simulation modelling, which can incorporate the interconnections between physical processes and marsh sedimentation. -after Author