Creating a Model to Predict Future Carbon Levels in Tidally-driven Marshes

Science Center Objects

Tidal marshes are important ecosystems in the San Francisco-Bay Delta. They remove carbon from the atmosphere, they build up soils that buffer our communities from sea level rise, they provide critical habitat and food resources for a diversity of species, and they reduce excessive nutrients which have a negative impact on water quality. As a result of land-use change and urbanization, the San Francisco Bay and Sacramento-San Joaquin Delta (the Bay-Delta) have lost an estimated 90 and 95% of their historic tidal marshland, respectively.

In spite of their importance, tidal marsh ecosystems are understudied, making it difficult to predict how they may change naturally over time or respond to larger-scale changes in, for example, climate and water quality. Further, insufficient knowledge exists about how to enhance the benefits of tidal wetlands through restoration.

Objective

This project will provide the first ever multi-year dataset of the complete carbon budget of a tidal marsh, including continuous measurements of atmospheric and hydrologic carbon exchange. This dataset will be used to expand an existing Bay-Delta marsh biogeochemical model that predicts seasonal and annual carbon budgets in tidally-driven marshes over a range of salinity values.

Specifically, we propose to measure net carbon balance in two tidal marshes (Rush Ranch in Suisun Marsh and Eden Landing on San Francisco Bay) and use the data to develop a modeling tool to predict carbon sequestration, subsidence reversal, and climate resilience of tidal wetlands.

Scientist adjusts equipment mounted on tower at the Suisun Marsh in California.

USGS Research Scientist Ellen Goodrich-Stuart adjusts a CH4 (Methane) analyzer mounted on the eddy covariance flux tower at the Rush Ranch site at Suisun Marsh. 

Science Plan

This research will provide unprecedented long-term records (totaling 9 site years) of carbon monitoring in tidal wetlands. This will include eddy covariance measurements of vertical fluxes of carbon dioxide (CO2) and methane (CH4) coupled with continuous measurements of lateral carbon fluxes estimated using new technologies and methodologies.

The data will be used to develop a modeling tool to assess and evaluate the magnitude and direction of carbon fluxes critical to habitat restoration (e.g. sediment accretion, carbon sequestration) and evaluate the timescales necessary for cost-effective carbon accounting in the Bay-Delta which can guide policy.

The modeling tool will also be used to conduct regional modeling of greenhouse gas exchange from existing and proposed wetland restoration in the Bay-Delta region.

Relevance and Benefits

There is now a statewide action to restore tidal marshes in the Bay-Delta Estuary to fulfill the goals of the California Water Action Plan and the co-equal goals for the Delta. The model that results from this project will be an open-source tool designed for use by wetland managers and decisionmakers in the Bay-Delta region. The information gained from using this tool will help support on-going initiatives to restore tidal wetlands in the Delta and our ability to manage them in a changing world.