By bridging scientific inquiry and climate policy implementation, this project filled key regional blue carbon data gaps and expanded blue carbon data accessibility to facilitate the development of climate mitigation strategies.

The Project

Blue carbon refers to the carbon sequestered and stored in tidal wetlands such as tidal swamps, salt marshes, and seagrass meadows (and mangrove forests at tropical and subtropical latitudes). Blue carbon ecosystems are especially effective at capturing and storing carbon, often storing disproportionately large amounts of carbon on a per acre basis. However, tidal wetlands can also emit varying amounts of greenhouse gases (GHGs)—including carbon dioxide, methane, and nitrous oxide—which can reduce or offset their net climate benefit.

To fill regional data gaps associated with GHG emissions and carbon accumulation rates in Pacific Northwest (PNW) tidal wetlands and investigate how net ecosystem carbon balance differs among wetland types and land uses, a project team of PNW Blue Carbon Working Group members partnered with two National Estuarine Research Reserves and other collaborators to plan and implement this project. This project was built on partnerships developed through previous Science Collaborative efforts and addressed key data gaps and research priorities identified in those earlier projects (see: 2016 Collaborative Research and 2018 Catalyst Project).

Through new data collection across five estuaries and continued engagement with partners, the project team examined how net ecosystem carbon balance differs among wetland types and land uses, quantified blue carbon-ecosystem driver relationships, expanded the regional blue carbon database, and provided new data to the Smithsonian’s Coastal Carbon Research Coordination Network working group to help validate a national methane emissions model.

Significant findings included:

• Most project sites with salinity >2–3 ppt showed reduced methane fluxes.
• Highest methane emissions occurred in wet pastures and restored marshes, especially those with low salinity and high water table.
• Carbon accumulation rates were highest in restored marshes, somewhat lower in least-disturbed marshes and swamps, and lowest in diked pastures.
• Carbon accumulation rates varied within wetland categories, primarily due to local differences in growing season water table level.

The Impact

The project along with the PNW Blue Carbon Working Group (Working Group) has played a pivotal role in advancing blue carbon science and facilitating the development of natural climate solutions policy, generating both direct and indirect impacts on climate mitigation efforts focused on the US Pacific Northwest. Through collaborative research, policy integration, tool development, and regional coordination, the Working Group has significantly influenced how scientists and policymakers incorporate coastal ecosystems into natural climate solutions strategies.

The project's impacts include:

• Helped advance climate policy and secure funding for natural climate solutions (e.g. directly contributed to Oregon’s Blue Carbon Inventory, making Oregon the first state to formally incorporate blue carbon into its state climate plan).
• Expanded data accessibility by creating a centralized data repository that has facilitated information sharing among regional and international stakeholders.
• Contributed to and addressed data gaps in decision-support tools to enhance climate action .
• Strengthened international scientific networks by forging connections between U.S. and Canadian researchers.
• Project data were central to upgrading and improving the accuracy of blue carbon tools under development for the region: a regional blue carbon calculator and blue carbon mapping for individual estuaries.