A series of questions needs to be answered before scientists can conclude that carbon-capture farming is beneficial. Among them is whether turning cornfields into tule-filled wetlands will only replace one type of greenhouse gas with more of another. Plowing for agriculture oxidizes the soil, creating "perfect banquet conditions" for microbes that eat the peat and release carbon dioxide, Miller said. Flooding the fields with low levels of water to make wetlands limits the oxygen but forces the microbes to turn to other compounds. "When oxygen is limited, the bugs, the microbes, have to eat and breathe somehow," she said. "They will use sulfate, iron or some other compound. Instead of producing (carbon dioxide) at the end of the pathway ... they end up producing methane," another greenhouse gas. Scientists also want to be sure that changing cornfields to wetlands won't increase a third greenhouse gas, nitrous oxide. They also are trying to determine how to minimize another potential problem -- dissolved organic matter, which leaches out of peat soil and plants when exposed to water. When delta water containing dissolved organic matter is treated for drinking supplies, it forms something called "disinfection byproducts," compounds that are carcinogenic. Geological Survey scientists want to make sure that creating more wetlands won't increase levels of those compounds. They also want to be sure that carbon-capture farming won't cause the release of mercury that has been washing into the delta from mining operations going back to the Gold Rush era. If scientists can work out those problems, they hope to develop a manual showing farmers how to create their own carbon-capturing wetlands and keep them healthy. Related Links: Geological Survey's California Water Science Center Discovery News: Global Warming |
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