Numerical models of salt marsh evolution: Ecological, geomorphic, and climatic factors

Abstract

[1] Salt marshes are delicate landforms at the boundary between the sea and land. These ecosystems support a diverse biota that modifies the erosive characteristics of the substrate and mediates sediment transport processes. Here we present a broad overview of recent numerical models that quantify the formation and evolution of salt marshes under different physical and ecological drivers. In particular, we focus on the coupling between geomorphological and ecological processes and on how these feedbacks are included in predictive models of landform evolution. We describe in detail models that simulate fluxes of water, organic matter, and sediments in salt marshes. The interplay between biological and morphological processes often produces a distinct scarp between salt marshes and tidal flats. Numerical models can capture the dynamics of this boundary and the progradation or regression of the marsh in time. Tidal channels are also key features of the marsh landscape, flooding and draining the marsh platform and providing a source of sediments and nutrients to the marsh ecosystem. In recent years, several numerical models have been developed to describe the morphogenesis and long-term dynamics of salt marsh channels. Finally, salt marshes are highly sensitive to the effects of long-term climatic change. We therefore discuss in detail how numerical models have been used to determine salt marsh survival under different scenarios of sea level rise.

A global standard for monitoring coastal wetland vulnerability to accelerated sea-level rise

“…Coastal wetland models continue to evolve, and vary in the extent that they incorporate complex ecological and physical processes occurring at the surface and shallow subsurface levels 27 . Recent numerical models that integrate non linear feedbacks among inundation, plant growth, organic matter accretion and mineral sediment deposition have been developed to identify the circumstances that lead to coastal wetland resilience and thresholds that result in the submergence of coastal wetlands 27,28 . These models are addressing a major knowledge gap in understanding the limits of wetland adaptation to SLR 28 and the processes affecting coastal marsh response.…”

Signatures of sea level changes on tidal geomorphology: Experiments on network incision and retreat

“…Within tidal landscapes, improving our understanding of network dynamics in response to variations in relative mean sea level (RMSL) is theoretically and practically relevant for the key role exerted by tidal networks on the eco-morphodynamic evolution of tidal systems [e.g., Fagherazzi and Overeem, 2007;de Swart and Zimmerman, 2009;Fagherazzi et al, 2012]. Despite their importance in landscape evolution, tidal networks have received less attention when compared to their fluvial counterparts [e.g., Howard et al, 1994] particularly in terms of the chief processes governing their initiation and evolution, and their response to variations in external forcings [e.g., Rigon et al, 1994;Rinaldo et al, 1995].…”

Multiple Stable States and Catastrophic Shifts in Coastal Wetlands: Progress, Challenges, and Opportunities in Validating Theory Using Remote Sensing and Other Methods

“…), and so there has been a recent explosion of the use of such theory to describe the temporal evolution of coastal wetlands (see Section 2.3.). In brief, multiple stable ecosystem states are created by coupled positive and negative feedbacks that link the ecological, hydrological and geomorphological processes in the coastal wetland environment in a self-reinforcing and relatively resilient manner [39][40][41][42][43].…”