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Friday, August 09, 2013
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Carbon storage in CA Tidal Marshes: the Role of Tidal Marsh Restoration in Carbon Credit Programs

By Guest Author, Kevin Sherrill, Yale F&ES '14

Five years ago – the last time I walked through the Giacomini Wetlands -- I was working to rescue 12 leopard sharks that had stranded themselves in a pasture after a levee broke, just six months shy of its scheduled removal. This is just one of the many interesting land-sea conflicts that arise in a state that has seen 91 percent wetland loss, well above the estimated 53 percent national average for the lower 48.

The 560-acre area at the southern end of Tomales Bay was leveed and drained in the 1940s to make room for expanding dairy farms and roads in west Marin County, California, cutting off the Lagunitas Creek watershed’s connection with its flood plain and increasing pollutant loading to the bay. Thankfully, a lot has changed since the 2008 restoration project effectively doubled the size of tidal marshes.

Following the restoration Tomales Bay has seen improvements in water quality, native plant recolonization, along with a rise in wildlife abundance and diversity. Aside from the more obvious improvements to the Bay’s health, tidal marsh restoration or conservation projects also have a huge potential to store carbon, an appealing prospect for those seeking to mitigate climate change.

Intact marshes that can keep pace with relative sea-level rise are usually sinks for the greenhouse gas carbon dioxide and sources of methane and nitrous oxide. Emission rates of the latter are much smaller in magnitude; however, they have 25- and 298-times, respectively, the global warming potential of carbon dioxide on a 100-year time horizon. While marshes play a vital role in carbon sequestration rates, it is essential to quantify how greenhouse gas emission rates vary across marsh complexes – especially with more large-scale restoration projects for the San Francisco Bay area on the horizon.

I’ve spent the summer back in Giacomini Wetlands – much less wary of submerged drainage ditches and stray leopard sharks than I was in 2008. Instead, I’m using static soil chamber and gas chromatography techniques to see how greenhouse gas emissions rates vary across a number of variables including salinity gradients, vegetation communities, and restoration histories. My research should offer a more accurate portrayal of restored marshes’ net carbon-storage capacity, potentially elucidating the restoration strategies – for example, the re-vegetation palettes – that minimize greenhouse gas emissions.

Kevin Sherrill is a MESc candidate at Yale School of Forestry & Environmental Studies, YCELP Research Fellow, Carpenter-Sperry awardee, and Jubitz Family Endowment awardee. This summer he is working on quantifying carbon storage rates for restored and intact wetlands in the San Francisco Bay Area.

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Posted in: Energy & Climate

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