Climate Science

Vol. 27 No. 1

Reviewed by

Charles, J., “The Grass is Greener: Storing Carbon in Rangeland Soils,” Bay Nature (April–June 2012). A group of ranchers and scientists in California’s Marin County have been investigating a potential method for sequestering carbon in soil through “a few simple changes” in ranching practices. The project, referred to as the Marin Carbon Project, involves not only the ranchers but also a rangeland ecologist, a UC Berkeley biogeochemist, and representatives of the USDA Natural Resources Conservation Service, Marin Organic, and the Marin Agricultural Land Trust. The results have been promising:

Three years ago, the team spread a half-inch blanket of compost on the soil surface of the test plot. Today 90 percent of the material remains on the surface, acting like a slow-release fertilizer and helping to build soil organic matter. And the underlying soil has gained a metric ton more carbon than similar areas nearby that were left alone. Some of this additional carbon came from the compost, and some is likely to have come from plant growth that was stimulated by the compost. The team’s computer models suggest that a single application of compost could lead to carbon storage for up to 30 years. If this turns out to be true, spreading compost on half of the 23 million acres of rangeland in California every three decades could offset all carbon emissions from all commercial and residential use.

The next step is to increase the scale of the project and entice other ranchers to participate. The cost of the compost is a significant factor. The project team has been working toward participation in emerging carbon markets by “working with the Environmental Defense Fund to develop a protocol that will meet state standards and let interested businesses and investors partner with rangeland owners on efforts to meet greenhouse gas reduction requirements.” One notable local business, George Lucas’s Skywalker Ranch, has proposed “to offset 500 metric tons of greenhouse gas emissions per year” in part “through rangeland carbon sequestration.”

In conclusion the author observes that if the Marin Carbon Project is successful “in facilitating an economic reward for greenhouse gas reduction and carbon storage on California’s ranches, it will be an exciting step toward ensuring the preservation of iconic rural landscapes and communities.”


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