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And then the farm would store that carbon in the tissue by minimizing the loss or the decay of that. And since carbon dioxide is a very important greenhouse gas that's been linked to global warming, this could be a method to address that problem. And so our new research project will be testing the feasibility of carbon-capture farming in the Sacramento-San Joaquin Delta where it could have other benefits as well.
And so under traditional farming practices, the islands lose up to an inch of surface elevation a year. And now many of the islands are subsided more than 20 feet below sea level and the ground water has to be kept even lower than the land surface to grow crops. And so we have water tables on some of those Delta islands that are 25 feet or more below the surrounding water channels which create a lot of pressure against the levees and make the levees extremely vulnerable to failure.
And this would be incredibly catastrophic to California. I mean imagine all of the water being sent down to LA, to San Joaquin valley farms, and Contra Costa being shut off. I mean what would those people in farms and businesses do without a usable water supply? So by increasing land surface elevations on these islands, the water pressures against the levees are minimized or decreased and the levee systems are a lot less felt vulnerable to failure and so there was less likely levee breaks and if there are, there are less of a problem because there's less space to filled with water. So this helps protect California's water supply.
And we hope to be able to develop a different kind of farming in the Delta. Instead of growing corn or alfalfa or tomatoes, the farmers will grow tules or cattails.
Jim Nickles: So you are talking about a new kind of farming in the Delta. But Robin, how would a farmer potentially generate income from this? How would this work to replace traditional farming?
Robin Miller: Well, the farmer would sell carbon-capture credits which are similar to emission-reduction credits. A greenhouse gas reduction could be sold to an industry for which greenhouse gas reductions are prohibitively expensive or impractical. California's trying to establish a carbon-credit system that would allow carbon credits to be bought and sold. And although the carbon-credit market is not yet established in California, our hope is that carbon farms will be able to sell their credits and make money, essentially replacing conventional farming in the Delta with carbon-capture farming.
Jim Nickles: Robin, what are some of the things your research will be looking at? I've heard, for instance, that wetlands also can be emitters of greenhouse gases?
Robin Miller: We could also be producing a lot of nitrous oxide which is also a big important greenhouse gas much stronger than CO2 or methane. Re-establishing wetlands could sequester CO2 and mitigate some of the nitrous oxide emissions but then by putting out methane, you know, you're introducing another.
Not all wetlands produce a lot of methylmercury even if they have mercury in the system. We don't know what will happen in these wetlands and we need to look at that. Another issue is just DOC, dissolved organic carbon, that's produced by wetland plants and is an issue in drinking water because once the drinking water's treated if there's a lot DOC, if there's a lot of dissolved organic carbon in the water, when it's treated, it can become chlorinated and creates disinfection by-products that are regulated and a concern for human health.
Robin Miller: And that's what we're finding. We're finding that we can manage the wetland to minimize DOC export, that we can actually manage the hydrology to kind of minimize some of the methane emissions. We need to look at that more closely. An interesting thing about the Delta is that it produces less methylmercury than the surrounding areas. So there's more methylmercury coming in to the system than going out of the system. So even though wetlands are places where methylmercury is produced, these wetlands seem to almost be cleaning and scrubbing.
If you're interested in learning more about the USGS carbon-capture efforts, take a look at the links on the notes for this episode.
Music by Dane Klima
Resources related to this episode:
Title: Farming Carbon to Help the Atmosphere and the Land
Description: Long-standing farming practices in California's Sacramento-San Joaquin River Delta expose fragile peat soils to wind, rain and cultivation, emit carbon dioxide (CO2) and cause land subsidence. To capture or contain the carbon, farmers would ‘grow’ wetlands. In doing so, they would begin to rebuild the Delta's unique peat soils, take CO2 out of the atmosphere, ease pressure on the Delta's aging levees, and infuse the region with new economic potential. We learn more from USGS bio-geochemist Robin Miller about how this could help California, the nation, and the world.
Date Recorded: 9/29/2008
Audio Producer: James Nickles , U.S. Geological Survey
Usage: This audio file is public domain/of free use unless otherwise stated. Please refer to the USGS Copyright section for how to credit this audio.
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