California Agriculture
California Agriculture
California Agriculture
University of California
California Agriculture

Archive

California Agriculture, Vol. 63, No.2

“Unequivocal” - How climate change will transform California
Cover:  In its 2007 report, the Intergovernmental Panel on Climate Change concluded that climate change is “unequivocal.” Wildfires are expected to become more commonplace in California, consistent with the predictions of climate-change models. Twelve large wildfires — fueled by the powerful Santa Ana winds that pushed flames through brush and grass dried from drought — raged in California on Oct. 23, 2007, clouded the air over the Pacific Ocean with dense plumes of smoke. Photo: NASA image by Jeff Schmaltz, MODIS Rapid Response Team, Goddard Space Flight Center
April-June 2009
Volume 63, Number 2

Peer-reviewed research and review articles

How will changes in global climate influence California?
by Bryan C. Weare
| Full text HTML  | PDF  
Sophisticated models show that California can expect significant changes to water availability, air quality and growing conditions.
In 2007, the Intergovernmental Panel on Climate Change (IPCC) published its fourth assessment reports summarizing recent global climate change and projections for the next century. This article reviews the basics of climate science and modeling, highlights the conclusions of the IPCC report, and identifies the well-understood aspects of climate change that will be important for California agriculture and society as a whole. Predicted impacts to California include increased flooding and reduced water availability, higher sea levels, worse air pollution and fewer chilling hours for important crops.
As carbon dioxide rises, food quality will decline without careful nitrogen management
by Arnold J. Bloom
| Full text HTML  | PDF  
As atmospheric carbon dioxide rises and nitrogen assimilation decreases in crop plants, managing N will be necessary to ensure food quality and protein content.
Rising atmospheric concentrations of carbon dioxide could dramatically influence the performance of crops, but experimental results to date have been highly variable. For example, when C3 plants are grown under carbon dioxide enrichment, productivity increases dramatically at first. But over time, organic nitrogen in the plants decreases and productivity diminishes in soils where nitrate is an important source of this nutrient. We have discovered a phenomenon that provides a relatively simple explanation for the latter responses: in C3 plants, elevated carbon dioxide concentrations inhibit photorespiration, which in turn inhibits shoot nitrate assimilation. Agriculture would benefit from the careful management of nitrogen fertilizers, particularly those that are ammonium based.
Climate change will exacerbate California's insect pest problems
by John T. Trumble, Casey D. Butler
| Full text HTML  | PDF  
Higher temperatures can let new species invade and cause existing species to change locations or go extinct; higher carbon dioxide can increase insect feeding.
The elevated carbon dioxide concentrations and increasing temperatures associated with climate change will have substantial impacts on plant-insect interactions, integrated pest management programs and the movement of nonnative insect species into California. Natural ecosystems will also be affected by the expected changes in insect diversity. Many insects will alter how much they eat in response to changing plant nutrition. Also, we can expect increased problems with many pest insects as they develop more rapidly in response to rising temperatures. If we hope to maintain sustainable agro-ecosystems and preserve native species in our natural ecosystems, we need to begin preparing now for the challenges of our changing environment.
Direct measurements improve estimates of dairy greenhouse-gas emissions
by Frank M. Mitloehner, Huawei Sun, John F. Karlik
| Full text HTML  | PDF  
Actual cattle emissions were measured in an environmentally controlled chamber.
California is the leading dairy state in the United States, producing 21% of the nation's milk supply. The state's highest concentration of dairies is in the San Joaquin Valley, a region that violates federal limits for ozone and particulate matter in the air. Volatile organic compounds and greenhouse-gas emissions from dairies contribute to regional air-quality challenges and also play a role in climate change. We used an environmentally controlled chamber to monitor greenhouse-gas emissions from dairy cattle over a 24-hour period, and we measured the emissions from waste slurry using a simulated dairy waste lagoon. This research helps to quantify emissions from dairies in California and suggests possible approaches for their mitigation.
Modeling shows that alternative soil management can decrease greenhouse gases
by Steven De Gryze, Maria V. Albarracin, Rosa Catalá-Luque, Richard E. Howitt, Johan Six
| Full text HTML  | PDF  
By reducing tillage, fertilizing with manure or growing winter cover crops, farmers could cut carbon emissions and potentially sell the resulting carbon credits.
Agricultural management has a significant impact on the amount of greenhouse gases emitted by cropped fields. Alternative practices such as winter cover cropping and avoiding overfertilization can decrease the total amount of greenhouse gases that are produced. Policymakers are considering a structure in which parties (such as factories) who exceed their greenhouse-gas emissions cap can pay incentives to encourage farmers to adopt practices that curb greenhouse gases. Based on data from field studies and an ecosystem computer model, we assessed impacts on yields and the total potential for reducing greenhouse-gas emissions of certain alternative practices in California.
Realistic payments could encourage farmers to adopt practices that sequester carbon
by Richard E. Howitt, Rosa Català-Luque, Steven De Gryze, Santhi Wicks, Johan Six
| Full text HTML  | PDF  
Paying farmers for using conservation tillage could reduce Yolo County's greenhouse-gas production by 33,000 to 39,000 tons per year.
Carbon sequestration in agricultural land has been studied over the past few years to determine its potential for ameliorating climate change, Agricultural soils can be efficiently exploited as carbon sinks with a variety of techniques, such as reduced tillage, cover cropping and organic systems with better manure management. However, to fully understand the potential of carbon sequestration in agriculture, the economic costs of switching from conventional to conservation management must be estimated. Since carbon sequestration depends heavily on management, crop and soil type, we conducted a field-level survey of its economic aspects in Yolo County for the 2005 growing season. The survey showed that organic and conservation management can be more profitable for field crops than conventional management in Yolo County. Finall, we demonstrated how to combine the survey data with an agronomic process model to predict the rate of adoption for conservation techniques in response to carbon payments.
From kiosks to megastores: The evolving carbon market
by Deb Niemeier, Dana Rowan
| Full text HTML  | PDF  
California's greenhouse-gas mandate could provide a regulated carbon offset market for agriculture, including credits for manure digesters, and rangeland and forest conservation.
Markets can play a key role in mitigating the effects of climate change by providing added flexibility, allowing emissions reductions to occur at a lower cost while maintaining a set level of emissions reductions. With careful regulatory design, both industry and consumers can benefit from low costs. We review the state of carbon trading globally and in the United States, the West and California. New policies and regulations related to AB32, which mandates reductions in California's greenhouse-gas emissions to 1990 levels by 2020, are beginning to take shape. California has a unique opportunity to establish a new ethos for carbon trading by acknowledging unavoidable mitigation costs, and by designing a market-based solution that is fair, equitable and transparent, and protects the most vulnerable members of society.
Webmaster Email: wsuckow@ucanr.edu

Thank you for visiting us at California Agriculture. We have created this printable page for you to easily view our website offline. You can visit this page again by pointing your Internet Browser to-

http://calag.ucanr.edu/archive/index.cfm?issue=63_2

California Agriculture, Vol. 63, No.2

“Unequivocal” - How climate change will transform California
Cover:  In its 2007 report, the Intergovernmental Panel on Climate Change concluded that climate change is “unequivocal.” Wildfires are expected to become more commonplace in California, consistent with the predictions of climate-change models. Twelve large wildfires — fueled by the powerful Santa Ana winds that pushed flames through brush and grass dried from drought — raged in California on Oct. 23, 2007, clouded the air over the Pacific Ocean with dense plumes of smoke. Photo: NASA image by Jeff Schmaltz, MODIS Rapid Response Team, Goddard Space Flight Center
April-June 2009
Volume 63, Number 2

Peer-reviewed research and review articles

How will changes in global climate influence California?
by Bryan C. Weare
| Full text HTML  | PDF  
Sophisticated models show that California can expect significant changes to water availability, air quality and growing conditions.
In 2007, the Intergovernmental Panel on Climate Change (IPCC) published its fourth assessment reports summarizing recent global climate change and projections for the next century. This article reviews the basics of climate science and modeling, highlights the conclusions of the IPCC report, and identifies the well-understood aspects of climate change that will be important for California agriculture and society as a whole. Predicted impacts to California include increased flooding and reduced water availability, higher sea levels, worse air pollution and fewer chilling hours for important crops.
As carbon dioxide rises, food quality will decline without careful nitrogen management
by Arnold J. Bloom
| Full text HTML  | PDF  
As atmospheric carbon dioxide rises and nitrogen assimilation decreases in crop plants, managing N will be necessary to ensure food quality and protein content.
Rising atmospheric concentrations of carbon dioxide could dramatically influence the performance of crops, but experimental results to date have been highly variable. For example, when C3 plants are grown under carbon dioxide enrichment, productivity increases dramatically at first. But over time, organic nitrogen in the plants decreases and productivity diminishes in soils where nitrate is an important source of this nutrient. We have discovered a phenomenon that provides a relatively simple explanation for the latter responses: in C3 plants, elevated carbon dioxide concentrations inhibit photorespiration, which in turn inhibits shoot nitrate assimilation. Agriculture would benefit from the careful management of nitrogen fertilizers, particularly those that are ammonium based.
Climate change will exacerbate California's insect pest problems
by John T. Trumble, Casey D. Butler
| Full text HTML  | PDF  
Higher temperatures can let new species invade and cause existing species to change locations or go extinct; higher carbon dioxide can increase insect feeding.
The elevated carbon dioxide concentrations and increasing temperatures associated with climate change will have substantial impacts on plant-insect interactions, integrated pest management programs and the movement of nonnative insect species into California. Natural ecosystems will also be affected by the expected changes in insect diversity. Many insects will alter how much they eat in response to changing plant nutrition. Also, we can expect increased problems with many pest insects as they develop more rapidly in response to rising temperatures. If we hope to maintain sustainable agro-ecosystems and preserve native species in our natural ecosystems, we need to begin preparing now for the challenges of our changing environment.
Direct measurements improve estimates of dairy greenhouse-gas emissions
by Frank M. Mitloehner, Huawei Sun, John F. Karlik
| Full text HTML  | PDF  
Actual cattle emissions were measured in an environmentally controlled chamber.
California is the leading dairy state in the United States, producing 21% of the nation's milk supply. The state's highest concentration of dairies is in the San Joaquin Valley, a region that violates federal limits for ozone and particulate matter in the air. Volatile organic compounds and greenhouse-gas emissions from dairies contribute to regional air-quality challenges and also play a role in climate change. We used an environmentally controlled chamber to monitor greenhouse-gas emissions from dairy cattle over a 24-hour period, and we measured the emissions from waste slurry using a simulated dairy waste lagoon. This research helps to quantify emissions from dairies in California and suggests possible approaches for their mitigation.
Modeling shows that alternative soil management can decrease greenhouse gases
by Steven De Gryze, Maria V. Albarracin, Rosa Catalá-Luque, Richard E. Howitt, Johan Six
| Full text HTML  | PDF  
By reducing tillage, fertilizing with manure or growing winter cover crops, farmers could cut carbon emissions and potentially sell the resulting carbon credits.
Agricultural management has a significant impact on the amount of greenhouse gases emitted by cropped fields. Alternative practices such as winter cover cropping and avoiding overfertilization can decrease the total amount of greenhouse gases that are produced. Policymakers are considering a structure in which parties (such as factories) who exceed their greenhouse-gas emissions cap can pay incentives to encourage farmers to adopt practices that curb greenhouse gases. Based on data from field studies and an ecosystem computer model, we assessed impacts on yields and the total potential for reducing greenhouse-gas emissions of certain alternative practices in California.
Realistic payments could encourage farmers to adopt practices that sequester carbon
by Richard E. Howitt, Rosa Català-Luque, Steven De Gryze, Santhi Wicks, Johan Six
| Full text HTML  | PDF  
Paying farmers for using conservation tillage could reduce Yolo County's greenhouse-gas production by 33,000 to 39,000 tons per year.
Carbon sequestration in agricultural land has been studied over the past few years to determine its potential for ameliorating climate change, Agricultural soils can be efficiently exploited as carbon sinks with a variety of techniques, such as reduced tillage, cover cropping and organic systems with better manure management. However, to fully understand the potential of carbon sequestration in agriculture, the economic costs of switching from conventional to conservation management must be estimated. Since carbon sequestration depends heavily on management, crop and soil type, we conducted a field-level survey of its economic aspects in Yolo County for the 2005 growing season. The survey showed that organic and conservation management can be more profitable for field crops than conventional management in Yolo County. Finall, we demonstrated how to combine the survey data with an agronomic process model to predict the rate of adoption for conservation techniques in response to carbon payments.
From kiosks to megastores: The evolving carbon market
by Deb Niemeier, Dana Rowan
| Full text HTML  | PDF  
California's greenhouse-gas mandate could provide a regulated carbon offset market for agriculture, including credits for manure digesters, and rangeland and forest conservation.
Markets can play a key role in mitigating the effects of climate change by providing added flexibility, allowing emissions reductions to occur at a lower cost while maintaining a set level of emissions reductions. With careful regulatory design, both industry and consumers can benefit from low costs. We review the state of carbon trading globally and in the United States, the West and California. New policies and regulations related to AB32, which mandates reductions in California's greenhouse-gas emissions to 1990 levels by 2020, are beginning to take shape. California has a unique opportunity to establish a new ethos for carbon trading by acknowledging unavoidable mitigation costs, and by designing a market-based solution that is fair, equitable and transparent, and protects the most vulnerable members of society.

University of California, 1301 S. 46th St., Bldg. 478 Richmond, CA
Email: calag@ucanr.edu | Phone: (510) 665-2163 | Fax: (510) 665-3427
Please visit us again at http://californiaagriculture.ucanr.edu/