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Background
Background
In January 2014, the South Slough National Estuarine Research Reserve (South Slough NERR), in partnership with representatives from Restore America’s Estuaries (RAE), Environmental Science Associates (ESA), the U.S. Fish and Wildlife Service (USFWS), and the National Estuarine Research Reserve System’s Science Collaborative (NERRS Science Collaborative) hosted a group of wetland managers, agency representatives, and other decision makers from the Pacific Northwest to learn about blue carbon; specifically to discuss the Verified Carbon Standard's recently developed blue carbon methodology for tidal wetland and seagrass restoration and its implications for climate mitigation and estuary management in the Pacific Northwest.
The Pacific Northwest Blue Carbon Working Group was formed soon after to organize researchers to collaboratively fill what were then considerable blue carbon data gaps in the Pacific Northwest.
The mission of the PNW Blue Carbon Working Group is to develop blue carbon as a conservation and management tool, so the conservation and restoration of Pacific Northwest tidal wetland ecosystems can be used to help mitigate climate-related changes.
The Membership of the working group includes scientists, restoration practitioners, conservation leaders, land managers, policy and carbon market experts, representatives from carbon registries, and funding program leaders, as well as representatives from key government agencies. The working group reflects broad regional and national interest in blue carbon.
The current geographic scope of the working group includes estuarine ecosystems and coastal watersheds from the Puget Sound, WA to Cape Mendocino, CA. The group has identified three areas of primary interest—the outer coast, Puget Sound, and the lower Columbia River (see figure). Additional interest in the working group from our colleagues to the north will likely result in our adjusting the geographic scope's northern boundary to include the Strait of Georgia, BC.
For more information about the PNW Blue Carbon Working Group, see the working group's Biophysical Research Framework on the Documents page.
Current geographic scope of the
PNW Blue Carbon Working Group
What is Blue Carbon?
Blue carbon is the carbon stored and sequestered in coastal ecosystems such as mangrove forests, seagrass meadows or intertidal salt marshes (http://bluecarbonportal.org/). Tidal wetlands, including emergent marshes, forested and scrub-shrub swamps, and seagrass beds, play an important role in the global carbon cycle by sequestering carbon from the atmosphere (CO2) continuously over many growing seasons, building stores of carbon in wetland soils high in organic content (Crooks et al. 2014). Thus, wetlands that store blue carbon mitigate for carbon dioxide emissions and moderate climate change.
Carbon sequestration has been shown to be very high in tidal wetlands. On a per-acre basis, tidal wetlands store 3-5 times more carbon than tropical forests (Murray et al. 2011). Recent studies have highlighted the potential for carbon sequestration in Pacific Northwest tidal wetlands (Crooks et al. 2014). Pacific Northwest (PNW) tidal wetlands have high potential for carbon sequestration for several reasons:
Sediment delivery: Due to coastal geomorphology and climate, PNW rivers deliver large quantities of sediment to tidal wetlands and bays. High sediment delivery means higher resilience to climate change, since sediment accretion is an important component of tidal wetland equilibration with sea level rise. (The other major component is belowground organic matter produced and stored by plants, such as roots and buried woody debris.)
High organic content in soils: Evidence is strong that large quantities of carbon accumulate in PNW tidal wetlands. Several studies have shown very high soil carbon content in Oregon’s tidal marsh and tidal swamps (e.g. MacClellan 2011, Brophy 2009) and other PNW tidal wetlands. In many of Oregon’s drowned river mouth estuaries, organic soils are very deep, indicating long-term carbon accumulation and storage.
Sheltered settings: Most of the PNW’s tidal wetlands exist in relatively sheltered landscape settings (the “sheltered coast” of bays and river systems, as opposed to the outer coast where wave and storm action is high). The erosion that threatens coastal wetlands in the Gulf of Mexico, for example, is unlikely to threaten our tidal wetlands because of this sheltered setting.
Brackish tidal swamps: The PNW outer coast once supported large areas of brackish forested and shrub tidal wetlands (“tidal swamps”). Brackish wetlands are less likely to release greenhouse gases (such as methane), compared to freshwater wetlands. In addition, tidal swamps generate large quantities of woody debris, which becomes buried and serves as another carbon storage mechanism. There is high potential to recover many of these altered tidal swamps through restoration actions (Brophy 2009, Brophy et al. 2011).
System engineers: In PNW tidal wetlands, system engineers such as beaver (Hood 2012) and Sitka spruce (Brophy 2009) create conditions highly conducive to organic matter accumulation. Beaver dams in tidal wetlands raise water tables, increasing soil saturation. Sitka spruce root platforms support production of large woody debris which eventually becomes buried in the saturated soils below, adding to carbon stocks.
Large tide range and strong tidal/fluvial interactions: Compared to many other parts of the U.S., tide range is large in the Pacific Northwest. Large tide ranges and strong seasonal fluctuation in precipitation and river flow have led to the development of tidal wetland plant communities with broad tolerances for inundation and salinity. These broad tolerances may allow higher resilience to climate change and the associated changes in inundation and salinity.
Land values and land use types: In many agricultural areas of the Pacific Northwest coast, land values are relatively low compared to urban and rural residential landscapes, increasing opportunities for conservation and restoration of tidal wetlands.
Tidal wetland image: Barbara Harmon