April 2007

Earth Day 2007 is April 22--UC efforts address climate change

The theme of Earth Day 2007 is "A call for action on climate change." Many scientists agree that the earth's temperature is on an upward trend and that it is due to human activities that release greenhouse gases into the earth's upper atmosphere. The most significant opportunities to curtail global warming lie in the hands of governments who set policies related to natural energy sources and construction of power plants. But there are things everybody can do. Manufacturing consumer products, producing agricultural crops, transporting people or goods, and cooling or heating homes and buildings are all associated with the release of greenhouse gases--however small or distant. Making informed changes in consumption offer opportunities to help stabilize the earth's climate. Here are some efforts being taken by the University of California Division of Agriculture and Natural Resources:

Drip irrigation reduces greenhouse gas

Subsurface drip irrigation has the potential to reduce greenhouse gas emissions, according to research at the UC Davis Center for Integrated Farming Systems sustainable farming project. California is the second largest emitter of greenhouse gases in the United States, of which an estimated 8 percent of carbon dioxide and 59 percent of nitrous oxide emissions are from agricultural activities. A two-year CIFS sustainable farming study suggests that the conversion from furrow irrigation to subsurface drip irrigation has the potential to reduce emissions, according to project coordinator Will Horwath and graduate student researcher Cynthia Kallenbach. Furrow irrigation, which is the most common irrigation practice in California row crop systems, wets the entire soil profile to near saturation. Subsurface drip irrigation limits the water delivery to a small area, which reduces the activity of soil microorganisms and processes related to trace gas emissions. "The adoption of subsurface drip irrigation is increasing in the Central Valley, but still is less than 15 percent of all irrigation despite the demonstrated benefits of water savings and reduction in greenhouse emissions," said Horwath. "We hope that our fall 2007 results on the economics of drip irrigation will help growers evaluate the benefits of alternative irrigation systems." For more information, contact Horwath at (530) 754-6029, ; or Kallenbach at (530) 758-3217, . Tip by Lyra Halprin, (530) 752-8664, .

Eat locally to reduce ecological "footprint"?

What's in season, helps the local economy, and may reduce greenhouse-gas emissions? Foods with a low-carbon or reduced ecological "footprint," according to Gail Feenstra, food systems analyst for the Davis-based statewide University of California Sustainable Agriculture Research and Education Program. "Carbon footprints" are calculated by assessing the energy and carbon emissions of the life cycle of food--the cost of growing, harvesting, processing and transporting food products. SAREP is collaborating with the UC Davis Energy Efficiency Center, UCD's Department of Agricultural and Resource Economics, and the Bon Appetit Management Co. to make those assessments. "Once we figure out how to calculate the energy cost of specific foods in a reliable way, we can label them with their carbon footprint," said Feenstra. "This will contribute to a 'farm to fork' analysis of foods purchased by institutional food buyers and chefs," said Feenstra. "We hope this research can be used by food service managers in making decisions about how to improve their ecological footprints." For more information, contact Feenstra at (530) 752-8408, . Tip by Lyra Halprin, (530) 752-8664, .

UC Davis Agroecology Lab aims to reduce atmospheric carbon by examining carbon sequestration

The UC Davis Agroecology Laboratory is evaluating the potential for and the economic value of carbon sequestration in the soil. The results can be used in a carbon credit market, in which farmers are subsidized for their efforts to sequester carbon. Greenhouse gases, primarily carbon dioxide and to a lesser degree methane and nitrous oxide, are exchanged between the earth and the atmosphere. Plants absorb carbon dioxide during photosynthesis, store it as carbon in their leaves, branches and roots, and then deposit it in the soil during decomposition, thus storing carbon that would otherwise move into the atmosphere, where it may contribute to global warming. The researchers are calculating the bio-physical potential for storing carbon in the soil by alternative management practices, such as organic farming, reducing tillage intensities or planting cover crops. The relatively small amount of carbon released from the plant and the release of nitrous oxide by soil microbes are also being taken into consideration. With these calculations, one can determine the relative costs of differing farm management practices and assist farmers in optimizing fertilizer application amounts to minimize nitrous oxide emissions. The results of this research will inform economic models that can be used to determine the value of carbon sequestration and how much a coal-burning power plant, for instance, would be required to pay in subsidies to offset its release of carbon. The resulting pool of money could then be tapped by farmers who adopt carbon sequestration practices. "This is an exciting opportunity for farmers to contribute to a solution for global warming and receive extra income for these efforts," said Steven De Gryze, a post-doctoral researcher in the UC Davis Department of Plant Science. For more information, contact plant science professor Johan Six at (530) 752-1212, , or De Gryze at (530) 752-3450, . Tip by Janice Corner, (530) 752-7091, .

UC study aims to reduce greenhouse gas emissions from dairy lagoons

Most California dairies maintain lagoons for liquid manure storage--lagoons that contain very little oxygen. Biological and chemical conditions in the lagoon result in the release of carbon, sulfur and nitrogen into the air. Besides the disagreeable smell, some of the gases can make their way into the upper atmosphere and contribute to global climate change. Aeration devices have been used at municipal waste facilities since the 1960s to increase oxygen in the water to change the microbial conditions, reduce the odor and cut greenhouse gas emissions. An increasing number of dairy operators are now considering aeration, however little research has been conducted related to dairy waste aeration and its potential benefits. University of California Cooperative Extension dairy advisor in Kings County Carol Collar is leading a collaborative project aimed at documenting how well aeration devices work in dairy lagoons, exactly how much oxygen is needed to reduce emissions, and whether it makes economic sense to use this emission-reducing strategy compared to other mitigation techniques. Among their early results, Collar and her colleagues found that the efficiency of aeration devices is far lower than what is being marketed to dairy operations. "The performance of the aerators was so poor, instead of needing four in a pond, a dairy might need 40. That would be unreasonable," Collar said. The research is continuing, with Collar the principal investigator, plus UC Davis faculty members in the departments of Biological and Agricultural Engineering and Animal Science, a microbiologist at USDA-Agricultural Research Service and the UCCE dairy advisor in Tulare County. For more information, contact Collar at (559) 582-3211, Ext. 2739, . Tip by Jeannette Warnert, (559) 241-7514, .

Link between global warming and transmission of West Nile Virus

There's a definite link between global warming and the transmission of mosquito-borne diseases, such as West Nile virus, says research entomologist William Reisen of the Center for Vectorborne Diseases at UC Davis. Mosquitoes are coldblooded and their temperature is similar to that of their environment, he explains. "Therefore, environmental temperatures play a critical role in establishing when (during the year) and where (geographically) that vector-borne diseases amplify to epidemic levels. This, in turn, enables parasite acquisition and transmission." In addition, parasites develop faster within the vectors (mosquitoes) and can be transmitted earlier in vector life and more frequently during warm periods. "Global warming will enhance these processes by extending transmission seasons to more months during the year and parasite distributions into colder latitudes," Reisen says, pointing out that West Nile virus epidemics in northern United States and Canada "have clearly occurred during summers with above normal temperatures and subsided during cool summers." Female mosquitoes "bite" because they require a blood meal to develop their eggs. "They're not flying needles; they're biological vectors," he says. Species of Culex mosquitoes that transmit West Nile virus are found on every continent except Antarctica. For more information, contact Reisen at (530) 752-0124, . Tip by Kathy Keatley Garvey, or (530) 754-6894.

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