Greenhouse gases (GHGs) are of increasing concern because of their potential role in promoting rapid and undesirable change in climate. Agriculture ironically serves as both a source and a sink for this increase in GHGs. A report released by the Council for Agricultural Science and Technology (CAST), Climate Change and Greenhouse Gas Mitigation: Challenges and Opportunities for Agriculture
highlights the complexities of policy options, implementation, and future monitoring and verification of GHG mitigation.
"Although uncertainties remain about the rate and extent of human-induced climatic change as well as the types and severity of its impact on agriculture, there is strong consensus on several points," says Keith Paustian, Task Force co-chair, Colorado State University. "Some of these points include the fact that climate is changing, and even more significant changes are on the horizon; the possibility of increased climate variability and more extreme weather events is a significant concern, especially as it interacts with agricultural production; and agriculture as a whole has evolved ways of dealing with variability in weather and climate, but these changesâ€” especially in the short termâ€”may be costly."
According to Paustian, the authors worked to examine all aspects of the agricultureâ€“GHG interface and outlined seven potential methods for agricultural mitigation of GHG concentrations:
â€¢ Take carbon dioxide from the atmosphere through crop photosynthesis and sequester it in biomass and soils
â€¢ Decrease the rate of land clearing for agriculture and take marginal lands out of production
â€¢ Change agricultural practices on productive, established agricultural lands
â€¢ Increase efficiency of farm inputs such as fuel, fertilizers, and pesticides
â€¢ Increase production of agricultural biofuels to replace fossil energy emissions
â€¢ Improve nitrogen use efficiency as the primary means of decreasing nitrous oxide emissions
â€¢ Decrease methane emissions by capturing or preventing emissions from animal manure storage and by increasing livestock production efficiency.
Agricultural practices that can reduce or offset GHG emissions are relatively well known; many are currently in use, although to a limited degree. While there is need to learn more about the effects of different environmental and management factors on GHG emissions, the current technical potentials for agricultural mitigation options are reasonably well known, and they are substantialâ€”on the order of 100â€“300 million tonnes of carbon per year, equivalent to 5â€“15% of total U.S. GHG emissions.
Because GHGs stem from so many different sources, agriculture must "compete" with other sectors of the economy for mitigation opportunities. Agriculture will have to overcome certain inherent disadvantages if it is to compete successfully for government payments or producing tradable emission offsets for the marketplace. Although emissions and potential sinks for agriculture are large in aggregate, the amounts for an individual farm are small compared with large point sources such as power plants.
"Emissions and sinks for GHGs in agriculture are characterized by being widely dispersed and difficult to measure compared with certain other major sources," says Bruce A. Babcock, Task Force co-chair, Iowa State University. "These factors have implications for the implementation of agricultural GHG mitigation strategies, including measurement and monitoring, offset valuation, and contractual arrangements. It is clear that agriculture can and should play a role in the debate about, and solutions to, climate change and GHG increases," he adds.
"The extent of that role is as yet impossible to predict given that outcomes dependâ€”to a large degreeâ€”on economic, social, and political decisions that will be made in the near future and in years to come." The state of the science, the emerging policy environment, and the enlightened self-interest of the agricultural industry argue for a prominent role for agriculture.
"The debate on climate changeâ€”its potential effects and what can or should be doneâ€”will continue to evolve and change in the years to come, shaped by scientific discovery, emerging policies, and subsequent changes in public awareness and opinion," concludes Teresa A. Gruber, CAST Executive Vice President. "Regardless of how science and policy may direct the future discussion of climate change and GHG mitigation, agriculture will be a focal point of concern, and therefore, agricultural producers and consumers will need to be informed to be engaged in the debate."