Agriculture and global warming
Impact of Global Warming on Agriculture
When green groups discuss climate change, they often invoke farmers as one of the groups whose livelihoods will be most impacted. To do so, though, would require a failed jump of reasoning that ignores the fact that greenhouse gases were named as such because their impact on global climate resembles that of physical greenhouses. As in a physical greenhouse, higher concentrations of carbon dioxide can increase photosynthetic capacity and water-use efficiency. (Wittwer 1997).
Rainfall is currently increasing in many areas due to increased evaporation that powers a more active hydrological cycle. (NCPA 2005). Even in Africa, this century’s stable, wet conditions have been unusually conducive to human welfare. (Taylor 2011). Additionally, record per-acre yields have been recorded for many important U.S. crops including beans, corn, cotton, oats, rice, and wheat throughout the past decade. (Taylor 2011).
Although climate models also predict a greater incidence of extreme weather events that can arguably have as great an impact on yields as climate change, (Wittwer 1997), they do not adequately take into account the ability of farmers to adapt to a changing world. Early climate models adopted the “dumb farmer” approach, or the idea that farmers would not change any part of their behavior when faced with changes in climate. This assumption was clearly flawed and Bernstein (2002) notes that it “was at odds with all of human experience.” As models became more sophisticated, they allowed farmers to change the species or breed of their existing crop or switch to a new crop altogether. Using this “smart farmer” approach, models can more accurately predict the real behavior of farmers and in many cases found that climate change yielded net benefits. (Bernstein 2002).
Greenhouse Gas Emissions from Agriculture
According to the EPA’s February 2011 estimates, agriculture accounts for only about 6.3% of total emissions at about 419.3 million metric tons of carbon. This figure is based exclusively on enteric fermentation in domestic livestock, livestock manure management, rice cultivation, agricultural soil management, and field burning. Fuel combustion in agriculture was grouped within the industrial energy category. Carbon storage on the other hand was estimated as offsetting about 17.4 million metric tons of carbon with a range of as much as 47.3 million metric tons offset to 11.6 million metric tons released.
In the past, the degree to which agriculture affects the climate has been overstated. One such report, claimed that livestock alone was worse for the climate than transportation. (Taylor 2010). What the authors of this study later admitted was that while they conducted the emissions from livestock based on an exhaustive life cycle analysis, they did not give the same treatment to the transportation sector. This is not to say that livestock emissions are small; their impact is significant but it should be measured within the greater context before such broad accusations are made.
Sequestration by Agriculture
Environmental advocates tend to suggest that agricultural carbon sequestration would enhance the income of farmers across the country, but to believe this requires an unlikely leap of faith.
For the carbon sequestered by agricultural lands to have any value, there would need to be a price on carbon. As was stated in the previous section, agriculture sequesters about 17.4 million metric tons of carbon while emitting more than 419.3 million (likely much more when industrial processing is taken into account). If there were a price on carbon, the increased energy costs would more than offset any sequestration income. One study suggests that net profits would fall about 50% and that production expenses would rise over $20 billion. (Heartland 1998)
Under this assumption, increased costs would push some agricultural production overseas to countries with less-restrictive environmental laws. This will also occur if farmers begin turning their cropland to forest for the benefit of sequestration. Such behavior would exacerbate destruction of pristine forests in many areas of the developing world.
Because of these reasons, the American Farm Bureau Federation (AFBF) testified to the U.S. Senate in 2003 that while it wants to be a partner in improving sequestration practices, any approach needs to remain voluntary. (Stallman 2003) Additionally, a joint study by the AFBF and the Heartland Institute noted that, “U.S. farmers lead the world in the use of progressive agricultural practices that minimize erosion, enhance soil fertility, and in other ways sequester carbon while minimizing emissions. If left unhampered by energy taxes or burdensome regulations, they will make further progress in limiting unnecessary emissions, as it is in their long-term self-interest to do so.” (Heartland 1998)
Bernstein, L. 2002. Climate Change and Ecosystems. The George C. Marshall Institute, Washington, DC.
EPA. 2011. 2011 Draft U.S. Greenhouse Gas Inventory Report. 
Heartland Institute. 1998. The Kyoto Protocol and U.S. Agriculture.
Stallman, B. 2003. Statement of the American Farm Bureau Federation to the Senate Subcommittee on Clean Air, Climate Change, and Nuclear Safety Regarding Agricultural Sequestration of Carbon.
Taylor, J.M. 2011. Global Warming is Creating Perfect Crop Conditions. Forbes.com.
Taylor, J.M. 2010. UN Scientists Admits Study Overstated Impact of Livestock on Global Warming. The Heartland Institute.
Wittwer, S. 1997. The Great Promise of the Greenhouse Effect. Consumer's Research: 19-22.