States Can Use Federal Data to Assess ‘Blue Carbon’ and Combat Climate Change

Pew webinar explored resources available to help quantify greenhouse gases captured by coastal habitats

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States Can Use Federal Data to Assess ‘Blue Carbon’ and Combat Climate Change
Oregon’s tidal forested wetlands—such as the Sitka spruce tidal swamp on the Columbia River estuary, shown here—capture and store significant amounts of carbon, but only 5% of these habitats’ historical peak acreage remains.
Oregon’s tidal forested wetlands—such as the Sitka spruce tidal swamp on the Columbia River estuary, shown here—capture and store significant amounts of carbon, but only 5% of these habitats’ historical peak acreage remains. Researchers have determined that 1,000 hectares could be restored, which would quadruple the total carbon sequestered and stored by the state’s coastal habitats.
Laura Brophy

Reducing greenhouse gas (GHG) emissions remains the most important weapon available to combat climate change, but states increasingly have access to other tools to help them in the battle.

During a recent webinar hosted by The Pew Charitable Trusts, experts from the U.S. Environmental Protection Agency and Silvestrum Climate Associates highlighted how new and expanded federal data resources can help states catalog and conserve “blue carbon”—carbon captured and stored in coastal wetlands. Although their geographic footprint is small, these coastal habitats—which include salt marshes, mangroves, and seagrasses—sequester carbon at a much faster rate than other types of habitat, and if left undisturbed, they can store that carbon for thousands of years.

Webinar participants learned how improving state-level conservation and management of wetlands—as well as other natural and working lands, such as forests, grasslands, and agricultural lands—can promote long-term carbon capture and storage, which in turn can lessen the effects of climate change. For instance, Tom Wirth, environmental protection specialist with the EPA’s Office of Air and Radiation Climate Change Division, noted that natural and working lands collectively removed 812 million metric tons (MMT) of carbon dioxide equivalent from the atmosphere in 2020, offsetting 13.6% of gross U.S. emissions. However, when accounting for emissions related to certain practices on working lands, such as livestock management and nitrogen additions to agricultural soils, those figures drop to 162.7 MMT and about 3% of emissions.

The webinar—which was attended by about 100 representatives of state and federal agencies, nongovernmental organizations, and research institutions—was one of the first activities conducted by the Blue Carbon Network.  Pew established the network earlier this year to help strengthen connections among professionals working on blue carbon.

EPA’s inventory of GHG emissions and sinks is a foundational resource

To accurately evaluate any improvements, states must first understand how much carbon already is captured by and stored in their coastal landscapes. State officials can begin by developing GHG inventories and using that data as a baseline on which to set emissions reduction goals and strategies. And progress toward those goals can be quantified over time by comparing subsequent carbon measurements with that baseline record.

An essential tool in establishing these baselines is the Inventory of U.S. Greenhouse Gas Emissions and Sinks, an annual report from the EPA that offers a comprehensive GHG accounting dating back to 1990. Wirth told webinar attendees that the inventory, which includes GHG emissions and removals from agricultural lands, forests, wetlands, and urban areas, is designed to be “policy neutral but policy relevant” and is available to state officials via the EPA Greenhouse Gas Inventory Data Explorer. The agency also can provide more in-depth data if needed, Wirth added.

Lisa Schile-Beers, a wetland ecologist with Silvestrum, told webinar participants that the EPA began including coastal wetlands in the inventory in 2017 using data developed from the National Oceanic and Atmospheric Administration’s Coastal Change Analysis Program and estimates from peer-reviewed national and global literature. The inventory’s data on coastal wetlands is now broken out by state, and because the inventory is updated annually, it’s expected to become more accurate over time.

Oregon leads country in coastal wetlands GHG inventory development

In response to Oregon Gov. Kate Brown’s directive to set goals for carbon sequestration and storage by the state’s natural and working lands, a team—including the Oregon Coastal Management Program, the Pacific Northwest Blue Carbon Working Group, Silvestrum, and Pew—developed a strategy in 2021 to help the state leverage its coastal wetlands to establish and pursue the goals. The strategy included creating a state GHG inventory for coastal wetlands, the first to use the same methods as the national inventory, along with Oregon-specific mapping data.

The team also presented recommendations for enhancing carbon storage in Oregon’s coastal wetlands. “One of the things that was neat about working on this project is that we called it ‘the art of the possible,’” Schile-Beers said, referring to the effort to ascertain whether some of the state’s once-dominant tidal forested wetlands could be restored and what their contribution to carbon capture and sequestration could be.

Only 5% of the state’s historical peak forested tidal acreage remains, and the team determined that almost 2,500 acres could be restored, which in turn could quadruple the amount of carbon sequestered and stored by the state’s coastal habitats. “There are some opportunities for restoration, but it just takes a lot of planning and trying to see how the environment might change in the future with sea-level rise,” Schile-Beers added.

Future improvements for blue carbon inventories

Importantly, neither the federal nor the Oregon data includes seagrasses, another coastal habitat recognized for its ability to capture and store significant amounts of carbon. Steve Crooks, Silvestrum’s principal in wetland science and a noted blue carbon expert, told webinar attendees that data from ongoing work in North Carolina is helping researchers understand how seagrasses can be incorporated into a coastal wetland GHG inventory.

Significant reductions in GHG emissions are essential to turning the tide on climate change. But coastal states can also use tools—such as the EPA’s Inventory of U.S. National Greenhouse Gas Emissions and Sinks and the Blue Carbon Network—and learn from pioneers, including Oregon and North Carolina, to establish their own GHG inventories for coastal wetlands and use that information to inform their climate strategies and goals.

Sylvia Troost works on incorporating blue carbon into climate action plans for The Pew Charitable Trusts’ conserving marine life in the United States project.

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