Interpreting Salt Marsh Dynamics: Challenging Scientific Paradigms

Hatvany, Matthew G.; Cayer, Donald; Parent, Alain

doi:10.1080/00045608.2015.1059172

Cited by 7 publications

(6 citation statements)

References 35 publications

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“…The threat of sea level rise has dominated theoretical and empirical salt marsh research for more than 30 years, from concerns that over 90% of global marshes could drown by 2100 (Crosby et al, 2016; Horton et al, 2018; Spencer et al, 2016; Valiela et al, 2018). Recent results show that marshes are adept at keeping pace with sea level rise, by growing vertically, when sediment is available to settle onto the marsh surface (Kirwan et al, 2016), an irony, given that fear of marsh loss by drowning has had an overriding influence on conservation policy since the 1970s (Hatvany et al, 2015). Despite the vertical resilience to sea level rise, there are many documented cases from Europe, North America, and Asia where marshes have undergone extensive lateral changes in cover, expanding or eroding hundreds of meters in just a few years (Yang et al, 2001; Lotze et al, 2006; Fagherazzi et al, 2013; Gunnell et al, 2013; Leonardi et al, 2016).…”

Section: Introductionmentioning

confidence: 99%

Sediment Supply Explains Long‐Term and Large‐Scale Patterns in Salt Marsh Lateral Expansion and Erosion

Ladd

Duggan-Edwards

Bouma

et al. 2019

Geophysical Research Letters

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Salt marshes often undergo rapid changes in lateral extent, the causes of which lack common explanation. We combine hydrological, sedimentological, and climatological data with analysis of historical maps and photographs to show that long-term patterns of lateral marsh change can be explained by large-scale variation in sediment supply and its wave-driven transport. Over 150 years, northern marshes in Great Britain expanded while most southern marshes eroded. The cause for this pattern was a north to south reduction in sediment flux and fetch-driven wave sediment resuspension and transport. Our study provides long-term and large-scale evidence that sediment supply is a critical regulator of lateral marsh dynamics. Current global declines in sediment flux to the coast are likely to diminish the resilience of salt marshes and other sedimentary ecosystems to sea level rise. Managing sediment supply is not common place but may be critical to mitigating coastal impacts from climate change.Plain Language Summary Salt marshes are valuable ecosystems for human societies and are especially vulnerable to losses caused by human activity and climate change. Little is known about how the size of marshes has changed in response to disturbance over large-and long-term scales. We used historical maps and aerial photographs to capture 150 years of change in marsh area extent in 25 estuaries and ca. 100 marshes across Great Britain. We then related the rates of marsh change to existing data on hydrology, biology, climate, sediment supply, and other variables, to find out which elements best explained patterns of erosion and expansion for the period between 1967 and 2016. We found a shift from long-term marsh erosion in the southeast to long-term marsh expansion in the northwest of Great Britain. This pattern was explained by a south-to-north gradient of increasing sediment flux into marshes and wave fetch lengths which helps transport sediment onto marshes. Our study demonstrates how sediment supply should be monitored and managed to preserve salt marsh extent into the future.

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Section: Introductionmentioning

confidence: 99%

Sediment Supply Explains Long‐Term and Large‐Scale Patterns in Salt Marsh Lateral Expansion and Erosion

Ladd

Duggan-Edwards

Bouma

et al. 2019

Geophysical Research Letters

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“…The research problem explored how such factors influence morphodynamic behavior over multiple seasons and at multiple sites, specifically SDRs and surface elevation. Rather than evolving in a linear and generalized manner, as frequently presented in the literature for the entire St. Lawrence Estuary (Hatvany, Cayer and Parent, 2015), the results illustrate a high degree of morphodynamic variability in the MTZ that is the norm rather than the exception. This variability makes modelling marsh evolution in response to climate change, RSL fluctuations, weather, and estuarine turbidity (SSCs) a difficult endeavor except at the broadest of generalizations.…”

Section: Discussionmentioning

confidence: 58%

“…In this scenario, an increasing portion of the high marsh surface becomes sediment deprived during certain periods, as documented on the high marshes at St. Joseph, AAC, and Montmagny West. This trend may be accentuated by falling RSL (1–2 mm annually) throughout the MTZ as a result of isostatic rebound (Dionne, 1986; Hatvany, Cayer, and Parent, 2015; Koohzare, Vaniček, and Santos, 2008; Xu, Saucier, and Lefebvre, 2006).…”

Section: Discussionmentioning

confidence: 99%

“…In the form of a V, the MTZ is from east to west a saline to brackish macrotidal environment with an approximate length of 150 km and width of 15 to 25 km, making it the largest turbidity zone on the East Coast of North America. Because of ongoing postglacial isostatic rebound, relative sea level (RSL) is falling at an estimated rate of 1–2 mm throughout the MTZ (Dionne, 1986; Hatvany, Cayer, and Parent, 2015; Koohzare, Vaniček, and Santos, 2008; Xu, Saucier, and Lefebvre, 2006). The MTZ is denoted by high and variable turbidity related to its form, complex bathymetry, tidal range, strong currents, and variable salinities ranging from <5 mg/L to >11 mg/L (Ouellet and Cerceau, 1976).…”

Section: Introductionmentioning

confidence: 99%

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Complexity, Variance, and Nonlinearity: A Multisite, Multiseasonal Study of Tidal Marsh Sedimentation Processes in the St. Lawrence Estuary, Canada

Cayer,

Hatvany

2023

Journal of Coastal Research

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A review of the international literature demonstrates the high potential of intertidal marshes for sediment sequestration and growth over time. Surprisingly few studies, however, discuss the sediment pathways that occur both seasonally and annually or the magnitude of such transits. Using a multifactorial approach that accounts for asymptotic evolution, this study examines and compares four marsh sites in the maximum turbidity zone of the St. Lawrence Estuary. The aim is to determine the role of intrinsic and extrinsic factors, ecogeomorphologic feedbacks, and coastal configuration on sediment dynamics. The hypothesis is that multiagency results in nonlinear evolution trends that are site specific. The methodology comprises interannual and intersite surface-height measures, sediment concentration values, tidal inundation frequency, relative sea-level data, and a weather activity index. The results reveal variable sediment deposition rates and surface-height evolution across the marsh profile over multiple seasons and between sites. They also conform with the understanding of asymptotic evolution and illustrate a multifactorial agency driving current dynamics. As hypothesized, the evolution of the studied marshes was highly variable and nonlinear across time and space, demonstrating complex sediment pathways. Recognition of this variability brings into question the generalizability of tidal marsh dynamics in large systems. Ultimately, modelling the trajectories and predictability of future marsh evolution in large systems such as the St. Lawrence Estuary requires a multifactorial approach over multiple seasons and at multiple sites.

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“…To continue these advances, there is a need for CPG engagement with the management or restoration of urban coastal environments. Along similar lines, Hatvany et al (2015) explored changes in scientific paradigms on coastal marshes, and Spears (2021) analyzed how race and income interact with sea level rise to mediate vulnerability in the southeastern United States (US). These studies address scientific theory and the human impacts of environmental change, but leave a gap around management interventions meant to address environmental change in urban coastal zones.…”

Section: Site Selection As a Key For Restoration Success And Equitymentioning

confidence: 99%

Site prioritization and the reproduction of inequity in the restoration of Biscayne Bay

Bradbury

2022

Canadian Geographies / Géographies canadiennes

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The restoration of urban estuaries is challenging due to the complexity of prioritizing sites in a context of social and biophysical unevenness. Site prioritization and selection are crucial components of ecological success and equity in restoration. In many cases, site prioritization is conducted according to simple opportunity or political expediency, but this needs to be investigated further in local contexts, with accompanying analysis of the impacts on urban environmental equity. Using a critical physical geography framework, I explore site selection processes in the restoration of Biscayne Bay through case studies of two urban streams. I use multiple data types to present an integrated perspective on urban restoration priority and the social context that produces restoration siting decisions. I find that the logics of restoration site selection in the Biscayne Bay watershed have produced ecologically questionable decisions and inequitable outcomes. Therefore, I argue that restoration decision making needs to include environmental justice criteria.

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Interpreting Salt Marsh Dynamics: Challenging Scientific Paradigms

Cited by 7 publications

References 35 publications

Sediment Supply Explains Long‐Term and Large‐Scale Patterns in Salt Marsh Lateral Expansion and Erosion

Sediment Supply Explains Long‐Term and Large‐Scale Patterns in Salt Marsh Lateral Expansion and Erosion

Complexity, Variance, and Nonlinearity: A Multisite, Multiseasonal Study of Tidal Marsh Sedimentation Processes in the St. Lawrence Estuary, Canada

Site prioritization and the reproduction of inequity in the restoration of Biscayne Bay

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