Integrated Modeling of Coastal Processes and Linkages to Management Applications

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Coastal wetlands provide valuable ecosystem services such as wave attenuation, surge reduction, carbon sequestration, wastewater treatment, and critical habitats for endangered fish and wildlife species. However, wetland loss threatens the capacity of coastal wetlands to provide these ecosystem services.

The Science Issue and Relevance:  Coastal wetlands play an important role in carbon sequestration, storage, fluxes, and mitigating the impact of climate change. The location and low-lying position of coastal wetlands make them vulnerable to saltwater intrusion from alterations in climate-induced rainfall variability, sea-level rise (SLR), river discharge, and increased frequency and extent of storm surge. However, the impacts of these environmental changes on carbon storage and fluxes in coastal wetlands remain unclear due to the complicated and non-linear relationships between plant and soil biogeochemical processes and physical conditions. Coastal ecosystem restoration and protection efforts strive to maintain or enhance the ecosystem services provided by coastal wetlands. Understanding the production and consumption of carbon under natural and anthropogenic disturbances is important for estimating the sequestration capacity and contribution of carbon dioxide (CO2) and methane (CH4) from coastal wetlands to the global carbon budget and global warming. Such data and information are needed for carbon credit-related management and restoration of coastal wetlands.

Figure 2. Current and proposed MR diversions in Louisiana deltaic wetlands. (Source: LaCPRA)

Figure 2. Current and proposed Mississippi River diversions in Louisiana deltaic wetlands. (Source: LaCPRA)

Methodology for Addressing the Issue: USGS scientists and collaborators will develop a process-driven wetland biogeochemistry model for tidal swamps and marshes in coastal Louisiana. The model will incorporate non-linear feedback relationships that govern plant productivity, soil organic matter decomposition, nitrification, denitrification, and greenhouse gas emissions (GHG) emissions. Input data include climate, vegetation, soil, and hydrology. We will use data of above- and belowground plant productivity, carbon sequestration and GHG (CH4, CO2, N2O) emissions from past and ongoing field studies to calibrate and validate the biogeochemistry model. The validated biogeochemistry model will be used to predict the impacts of Mississippi River sediment diversions (Fig. 1) and SLR on carbon sequestration, storage, and GHG emissions

Future Steps: The process-driven coastal wetland biogeochemistry model will be applied to other coastal regions to examine the impacts of coastal management on wetland carbon budget and GHG emissions under future climate change in support of a national wetland carbon assessment.

Location of Study: 29°42’27.30’’N, 90°24’41.27’’W