Fellow quantifies wetland carbon budgets

June 27, 2013
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Gavin McNicol, a Berkeley doctoral student and Delta Science Fellow, wants to quantify the carbon-credit value of restoring wetlands in the Sacramento-San Joaquin Bay-Delta.

His starting point is the “red” side of the carbon budget ledger – the well-known fact that wetlands, besides sequestering carbon through plant growth and peat formation, can also produce methane, one of the more potent greenhouse gases.

This summer, McNicol and colleagues will begin exploring the processes that speed up, slow down and ultimately determine the amount of methane produced by fermenting microbes in marsh muds. The focus is on methane because the gas has about 25-times the heat-trapping power of carbon dioxide. 

“We are excited because we have a newly designed instrument that has never before been used in the delta to help us,” said McNicol, who is part of the 2012 Delta Science Fellowship class. “The instrument has a chamber inside it that not only captures methane as it bubbles out of marsh sediments but also puts a time-stamp on when each sample was collected.”

“The timing of events will give us clues as to the processes that are important for methane production,” McNicol said. This could include soil and water chemistry, as well as water flows.

It’s all part of an effort to put numbers to the carbon value of, say, converting an old farm field into a marsh, and to perhaps identify restoration strategies for increasing a property’s carbon sequestration value. This could be done, for example, by selecting certain re-vegetation schemes over others.

“There is strong evidence that wetland systems in the delta take up carbon from the atmosphere,” McNicol said.”But to accurately quantify this into a carbon credit, we need to know the amount of carbon that marshes release, and what fraction of this carbon is methane.”

“We think a better quantification of methane emissions, and a better understanding of the controls on those emissions, may assist developers of wetland projects maximize their potential carbon-uptake value,” he said.

Below is a summary of his project, extracted from the news release that announced the 2012 Delta Science Fellowship winners:

Controls on the Net Carbon Emissions from Restored Wetland Ecosystems
R/SF-57 Sep. 2012–Aug. 2014
Gavin McNicol, UCB, gavinmcnicol@berkeley.edu
Are wetlands sources or sinks of greenhouse gasses? Could certain restoration strategies alter net carbon loading? This project explores emissions scenarios for two large restored wetlands in the Delta—one on Sherman Island, the other on Twitchell Island. The main goals are to quantify methane releases and, using isotopic methods, to investigate the effects of marshland plants on methane flux dynamics. (Methane is 25 times more effective at trapping heat than carbon dioxide on a century time scale, and thus is a central focus of this study.) The fellow will also study the rates at which carbon degrades to carbon dioxide and methane in wetland soils and how these vary with soil and substrate characteristics.

Written by Christina S. Johnson

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NOAA’s California Sea Grant College Program funds marine research, education and outreach throughout California. Our headquarters is at Scripps Institution of Oceanography, University of California, San Diego; we are one of 33 Sea Grant programs in the National Oceanic and Atmospheric Administration (NOAA), U.S. Department of Commerce.