The ‘Mississippi River Delta Transition Initiative’: Understanding the link between plant salt stress and water table dynamics in coastal wetlands

Coastal wetlands have experienced a rapid decline over the past 200 years due to human development, changes in land use, subsidence, sediment deficiency, rising sea levels, and shifts in hydro-climatic conditions. Nearly two-thirds of the world’s coastal wetlands have disappeared, with Louisiana accounting for about 40% of the U.S. coastal wetlands and 80% of the nation's total losses. These coastal wetlands are predominantly classified as Groundwater-dependent Environments (GDEs). In these ecosystems, groundwater plays a crucial role in sustaining life, and they have been extensively modeled using stochastic models of water table dynamics. However, the impacts of plant stress—particularly due to salinization—on plant transpiration and the water budget of coastal wetlands remain largely unexplored. This thesis reviews and critically examines various modeling frameworks and compares them with actual hydrological conditions. Specifically, the analysis focuses on coastal wetlands as a prototype for the ecosystems that support the Mississippi River Delta (MRD) in Louisiana. This region provides a wide range of ecosystem services and serves as a pivotal economic and socio-political hub. To address the limitations of traditional approaches, this work suggests developing future models that integrate the effects of salinization on ecosystem-scale transpiration, along with temporal fluctuations in factors such as salinity and sea level. This transition from a static to a dynamic perspective promises a more accurate representation of these phenomena, which is essential for effectively supporting restoration and conservation efforts in these vulnerable areas.