U.S. Agriculture and Global Climate Change:
The Potential for Agriculture to Mitigate Greenhouse Gas Emissions
and Combat Global Warming
Debbie A. Reed
Global Warming Campaign Director
National Environmental Trust
Environment and Public Works Committee
Clean Air, Climate Change and Nuclear Safety Subcommittee
United States Senate
July 8, 2003
Mr. Chairman and members of the Subcommittee, I am Debbie Reed, the Global Warming Campaign Director and Legislative Director at the National Environmental Trust, a nonprofit organization located in Washington, D.C., with an organizing presence in 15 states. The National Environmental Trust conducts public education campaigns on important environmental issues through media education and field outreach.
I am pleased to have this opportunity to share my expertise and that of the National Environmental Trust on what we feel is perhaps the greatest environmental issue confronting the world today: global climate change. While climate change is one of several important campaigns we work on at the National Environmental Trust, it is an overarching issue which affects virtually all the areas that we are concerned with as an organization. We commend this Committee and the Senate for dealing with the issue, and hope that you will continue to grapple with ways to reduce U.S. emissions of greenhouse gases (GHG).
Global climate change can have a major impact on agriculture, and yet agriculture can play a positive role in helping to combat climate change. These two areas are of particular interest to me and my organization. Prior to joining NET in 2000, I was the Legislative Director and Director of Agricultural Policy at the White House Climate Change Task Force, and I previously worked for Senator J. Robert Kerrey of Nebraska, and at the U.S. Department of Agriculture. It was while I worked for Senator Kerrey that I began working on the issue of agriculture and global climate change. Coming from a largely rural, agricultural state, Senator Kerrey was concerned first with the impact of global climate change on agriculture, which, as a business conduced largely outdoors, may be hardest hit by increased global temperatures, changes in precipitation, and severe weather events. He was equally concerned with strategies to deal with climate change in order to prevent the potentially devastating consequences of unmitigated global warming. Fortunately, there is a nexus between agriculture and mitigation strategies to begin dealing with climate change.
U.S. agriculture can make important, cost-effective contributions to offset a portion of U.S. emissions of GHG in the near- and medium-term. But it is no panacea, nor is it a solution. With the proper mix of policies and incentives, agriculture can provide a bridge to a less fossil carbon-intensive future, while improving the sustainability and perhaps profitability of a beleaguered but nonetheless vital U.S. economic sector. Agriculture and climate change policy, approached correctly, offer truly “win-win” opportunities for society and the environment.
I will limit my remarks today to the U.S. situation and domestic agricultural policies and practices, but the impacts of these policies and practices are universal. The same process by which agricultural soils absorb carbon, leading to improved agricultural sustainability and soil fertility and reduced erosion, also helps to reverse desertification and soil degradation in lands the world over.
Forests and forest soils are also important carbon reservoirs in the U.S. and worldwide. Currently, deforestation, or the cutting and clearing of forests, accounts for approximately 25% of global GHG emissions, and is responsible for significant environmental degradation. Policies to protect forest ecosystems and manage forests for climate change benefits are extremely important, but are not the focus of my testimony.
Global Warming is Occurring
As the overwhelming majority of scientists internationally and in this country have concluded, global climate change is occurring, and is linked to increased atmospheric concentrations of GHG. Evidence continues to accumulate that human activities and man-made GHG are contribute to global climate change. Fossil fuel combustion in the U.S. and globally accounts for the greatest amount of GHG emissions and increasing atmospheric concentrations, but other activities, including land use, land-use change and agriculture, also contribute.
Just last week, on July 2, 2003, the World Meteorological Organization issued an unprecedented alert indicating that record extremes in weather and climate events were continuing to occur around the world, stating: “(r)ecent scientific assessments indicate that, as the global temperatures continue to warm due to climate change, the number and intensity of extreme events might increase.” The Organization documented recent extreme weather events in several countries, including the following in the United States:
“In the United States, there were 562 tornados during May, which resulted in 41 deaths. This established a record for the number of tornados in any month. The previous monthly record was 399 tornadoes in June 1992. In the eastern and southeastern part of the US, wet and cold conditions prevailed for well over a month. Weekly negative temperature anomalies of -2 degrees C to -6 degrees C were experienced in May while precipitation excesses, ranging from 50 mm to 350 mm over a period of more than 12 weeks starting in March 2003, have been recorded.”
To prevent dangerous consequences from climate change, the U.S. and other countries must reduce our reliance on the burning of fossil energy sources. Mandatory policies to reduce GHG emissions are needed to command the resources and ingenuity necessary to convert to a less fossil-carbon-intensive future, and in a timeframe that prevents potentially devastating consequences for our society and others. Such policies, once enacted, will take time to implement. But until the U.S. begins to approach global climate change with credible policies that reduce net GHG emissions, we should pursue with vigor strategies such as agricultural sequestration to help offset as much of our emissions as possible.
Global Warming is a Threat to Agriculture
U.S. agricultural is a major industry. Farming contributed $80.6 billion (0.8%) to the national gross domestic product (GDP) in 2001. The U.S. agricultural sector provides the safest, most abundant and economical food and fiber supply in the world, and is the engine behind U.S. growth and prosperity, literally fueling our ability to prosper. However, farmers and many rural communities operate on the financial edge, within narrow profit margins and under variable environmental conditions. The threat of global warming and potentially severe weather events jeopardize the very livelihood of farmers and rural communities, as well as the ability of agriculture to continue to fuel U.S. prosperity. The potential impact of global climate change on agriculture should not and cannot be ignored.
Some general circulation models (GCMs) predict that regional temperatures and moisture shifts caused by warming trends will require adaptive changes in agriculture across the country. However, predictions for reduced crop yields, increased flooding, droughts, pests and diseases also raise the possibility that U.S. agricultural production will be harmed. U.S. farmers are a resilient, market-savvy group, keeping up with futures markets and trade boards, reacting as necessary to optimize profits and remain viable. However, catastrophic storm events can overwhelm a farmer’s resilience and ability to adapt, as can changes in moisture that can devastate harvests, forage, and livestock production. Warmer climates also favor the proliferation of insect pests and crop and livestock diseases. Potential severe weather events, such as flooding or drought, can overwhelm not just individual farmers, but entire communities and regions. The agricultural sector and rural communities alike thus have vested interests in addressing the threat of climate change.
Agriculture and Forestry as a Source and Sink of GHG Emissions
Agriculture and forestry currently represent a “net sink” in the U.S., and helped to offset just over 7 percent of U.S. emissions in 1999. The enactment of policies to promote more widespread adoption of proven management practices to enhance this sink effect can boost this potential above current “business as usual” levels. Agricultural soils were but 0.6 percent of the total net sink, for instance, but scientists estimate the soils have the capacity to offset up to 10 percent of U.S. emissions.
Total U.S. emissions in 1999 were 1840 million metric tons of carbon equivalents (MMTCE). The agricultural and forestry sectors contributed roughly 134 MMTCE, or 7 percent of total U.S. emissions, but also reduced emissions by 270 MMTCE, or nearly 15 percent of total U.S. 1999 GHG emissions. Thus, agriculture and forestry accounted for a net reduction of 137 MMTCE, or just over 7 percent of total U.S. emissions in 1999.
Approximately 91% of the “net sink” effect of agriculture and forestry (or approximately 125 of the 137 MMTCE) was due to forest sequestration, including trees, forest soils, and harvested wood. Agricultural soils accounted for 8 percent of the 137 MMTCE net sink, or 11 MMTCE. For both agricultural soils and forests, this represents the net sink effect under current, “business as usual” conditions.
Agriculture as a source of GHG Emissions
Agriculture contributes emissions of 3 of the 6 GHG’s of concern: carbon dioxide, methane, and nitrous oxide. For CO2, agricultural emissions are primarily from fossil fuel use, soil carbon release, and biomass burning. Methane emissions from agriculture are primarily from enteric fermentation in ruminant animals, rice cultivation, and biomass burning. For nitrous oxides, soils, fertilizers, manures and biomass burning contribute to releases from agriculture, with the greatest amount coming from the use of fertilizers.
Reductions from any of these sources can help to offset U.S. emissions. Scientists and policymakers are working on many of these areas.
For example, wind power on agricultural lands can reduce some of our reliance on fossil fuel combustion, as can the production of renewable energy sources and biofuels produced from agricultural materials (plant materials, animal wastes). Changes in tillage practices and the use of cover crops can reduce on-farm fuel use and nitrogen fertilizer applications rates. Methane from livestock and manures can be reduced through improved diets and changes in manure treatment. And soil carbon sequestration can be increased through improved management practices such as no-till and other conservation practices, the use of shelterbelts, grass waterways, site specific management, restoration of wetlands, and improved irrigation management, to name a few. Taken individually and together, these practices can make significant contributions towards offsetting our national emissions.
The Conservation Technology Information Center (CTIC), a public-private partnership dedicated to sharing information and data on agricultural management systems, estimates that approximately 80 percent of environmental issues that result from cropland and cropping practices can be corrected with the proper management approaches, including integrated conservation tillage.
Production Agriculture as a Sink
I would like to focus specifically on agricultural soils, and practices that can increase soil carbon sequestration. Changes in tillage practices can reduce fossil fuel use; result in net sequestration of CO2 in soils as soil organic carbon, or humus (the “life bread” of soils); reduce nitrous oxide emissions from soils and fertilizers; improve water quality; and increase wildlife habitat. Simply put, soil carbon enhances agricultural sustainability. Fortunately, soil carbon is a component of soil that can be changed via management practices.
Soil scientists estimate that the potential for U.S. agricultural soils to sequester additional carbon ranges from 98-276 MMTCE per year (average 187 MMTCE per year) – which represents fully 10 percent of U.S. annual emissions. However, this capacity represents the upper potential for soils, and would only occur if all cropland soils were immediately managed to maximize carbon uptake. If that were to occur, the ability of these soils to absorb carbon at these levels would still fall over time, since soils have a finite ability to absorb carbon, until a ‘saturation’ level is achieved. Rates of carbon sequestration drop as saturation levels are approached. In other words, maximization of agricultural soil carbon sequestration could mitigate up to 10 percent of our national emissions annually, but only for a 10- to 20-year period. But that timeframe is enough to offset some of our emissions as we transition our economy away from the current reliance on fossil fuels, and towards a less fossil-carbon intensive energy base. Agriculture can be a band-aid, but it won’t prevent global climate change.
Soil Carbon: Multiple benefits to farmers and society
Agricultural and soil scientists have measured the carbon content of soils for more than a century; USDA maintains test plots where they’ve collected and monitored soil carbon content for well over 100 years. Carbon monitoring in soils did not begin because of a potential link to global warming, however. The carbon content of soils is indicative of the “health” of soils. Increased soil carbon content – or soil carbon sequestration – leads to improved soil “tilth” (structure), thus reducing erosion of soils from wind and water; improved soil fertility and crop productivity; reduced runoff of agricultural nutrients and chemicals; and improved air quality.
Soil carbon content is increased via the addition of organic matter to soils – also known as “humus.” Plants, via photosynthesis, remove CO2 from the air for the production of plant biomass, which over time is sequestered in the soil as soil carbon, or humus. The carbon remains sequestered and stable in the soil as long as it is not disturbed or tilled. Tillage or the turning over of soils leads to exposure of the humus, and the resulting release of carbon. Thus, traditional tillage practices that “inverted” soils have led to the release of carbon. In this way, conversion of lands for agricultural uses in this country historically has led to emissions of carbon dioxide. Traditional tillage practices continue to add to U.S. carbon releases, albeit at a lower rate, since most agricultural soils that are traditionally-tilled have reached a low-point of carbon emissions, a near-equilibrium.
Scientists have shown that the adoption of conservation or no-till by farmers can reverse the historic and continued carbon loss – thus helping to reduce U.S. emissions, while contributing to agricultural sustainability and ancillary environmental benefits.
Farmer’s Experiences with No-Till: Practice Confirms Research
Some compelling stories from farmers who have converted to conservation tillage and no-till farming perhaps best provide a picture of the many benefits to society and farmers of this management practice. At a February, 2003 Congressional briefing on global warming and soil carbon sequestration, Elmon Richards of Richards Farms in Circleville, Ohio shared his experiences with Senate and House staff.
Beginning in the 1970s, Richards Farms began planting their 3,500 acres of corn and soybeans without tilling the soil. By converting to “no-till,” they found that the time it took to plant their fields was significantly reduced, as were fuel use, labor and equipment costs. Through experimentation they additionally found that by planting crop rows closer together, the crop canopy developed earlier and reduced the use of herbicides for weed control. Despite initial reduction in yields, the Richards’ found that after five years of complete no-till on their croplands, yields increased back to pre-conversion rates or even higher, due mainly to increased soil quality and improved water infiltration and retention. Additionally, the carbon content of the soils started to increase, leading to improved aggregate stability and higher earth worm populations – in other words, the soil began to look more like natural soils, teaming with biological life.
Among the benefits of no-till farming documented by the Richard’s family are:
· the need for fewer, smaller tractors;
· the need for fewer tractor passes over fields;
· reduced fuel use;
· reduced labor costs; and
· more free time.
More specifically, the tractors the Richards’ used for conventional tillage consumed an average of 3-4 gallons of fuel per acre for chiseling, disking, field cultivating, planting and spraying. The smaller no-till tractors consume an average of 0.3 to 0.4 gallons of fuel per acre for planting and spraying – or one-tenth the fuel use per acre.
If we were to apply the Richards’ figures on a national scale, we can begin to appreciate the potential impacts of just one aspect of this agricultural management change. Cropland nationwide accounts for 420 million acres, of which about 240 million are used for the major grain crops. Traditional tillage methods on these 240 million acres would use approximately 840 million gallons of fuel to till and plant. Using the Richards’ data, fuel use would drop to 96 million gallons nationwide for no-till planting – a savings of 744 million gallons of fuel annually. Since each gallon of fuel burned releases 6.1 pounds of carbon to the atmosphere, a reduction of 744 million gallons would reduce carbon emissions from fuel savings alone by approximately 2.1 MMTCE per year – which does not even account for the carbon sequestered in the soil!
Gordon Gallup of Idaho, who is currently President of the Idaho Grain Grower’s Association, offers similar evidence of the benefits of no-till. Gordon, his wife and sons currently farm about 3,000 acres in a wheat-barley rotation on the Snake River plateau in Southeast Idaho. The Gallup’s switched to no-till in 1985, and documented the following results:
· Tractor hours reduced from 1,400 to 120 per year;
· Water adsorption tests show the soils adsorb at a rate of 3.25 inches per hour of rainfall, compared to the neighbor’s conventionally-tilled soils, which adsorb at 0.6 inches per hour;
· “Phenomenal soil structure,” evidenced by rarely having to clean sediment basins (which collect eroded soil sediments) since converting to no-till;
· Higher yields (higher profit) during drought years, compared to neighbors who conventionally till;
· No significant difference in crop diseases between the Gallups’ fields and neighboring, conventionally-tilled fields; and
· Carbon content of soils has more than doubled.
Terry Davis of Roseville, Illinois also shared his experiences with Congressional staff at the February briefing. Among the benefits he emphasized, Terry documented the effect of no-till on water infiltration, run-off, and soil erosion. He found that carbon sequestration from no-till:
· Significantly improved water infiltration and the water holding capacity of his soils, and virtually eliminated run-off and soil loss (compared to neighboring fields experiencing same weather impacts);
· Led to an increase in the organic content of his soils from 2.1 percent in 1980 to 3.4 percent in 1995 – an increase in soil carbon content of nearly two-thirds; and
· Allowed him to cut nitrogen fertilizer applications by 50 percent, which translates into less nitrous oxide emissions and less leaching of nitrates into groundwater (which would ultimately end up in the Gulf of Mexico).
Finally, the following data are from farmers in the Colonial Soil and Water Conservation District in nearby Virginia. Conversion to no-till planting:
· Reduced run-off by 75 percent;
· Reduced sediment loss by 98 percent;
· Reduced nitrogen fertilizer losses in run-off by 95 percent;
· Reduced phosphorus run-off by 92 percent; and
· During Hurricane Floyd in 1999 (a 500+ year storm event), the soils held up incredibly well, showing no evidence of concentrated flows, a lack of down-stream bank erosion, of sediment deposition, and affected vegetation.
Barriers to Adoption of Conservation Tillage
The percentage of total planted acres in the U.S. under conservation tillage rose from 25% in 1989 to nearly 37% in 2002. No-till increased from 5 to 20 percent in that same period. While not all crops and soils are suited to no-till, policies to promote conservation tillage could ensure greater adoption rates.
The Richards’, the Gallups’, Terry Davis and other agricultural producers have attested that landowners are reticent to change from conventional tillage to no-till for a variety of reasons, including: tradition and culture; the prohibitive costs of purchasing or renting new equipment; and the need for technical assistance.
There is a 2-5 year ‘risk period’ when converting from traditional to conservation tillage, where management practices are unfamiliar, and soils need to become “reestablished” in the absence of tillage. Technical assistance is especially important during this period. However, some farmers are unable to weather the short-term drop in yields during the ‘risk period’ – even though yields tend to rebound and in many cases are higher under no-till, once the soil and the farmer adapt to this management change. Financial incentives may help.
Finally, it is important to ensure that policies to promote practices that optimize carbon sequestration do not have unintended (negative) environmental impacts. Assessments of the impacts on other GHG and on wildlife should be conducted prior to enactment.
Measurement, Monitoring, and Verification of Soil Carbon Content
Soil carbon content and changes in content can be accurately measured and monitored, and have been for many years. Farmers routinely collect soil samples to determine fertilizer application needs, and soil carbon is one of the parameters measured. Over two million such samples are collected every year, and these samples document changes in carbon over time. Specific sampling performed at experimental plots also shows changes in carbon content over time.
Natural variability of soils and carbon content of soils exists, even within the same field, making it difficult to accurately assess soil carbon content over large areas without a large number of soil samples. However, recent research has shown that soil scientists can apply their knowledge of landforms (topography) to selectively and precisely measure carbon within fields such that the aggregate carbon content of the soils can be reported with less than 10% variability. Such data can then be extended to large areas with the use of computer modeling, soil maps, and other resource information.
With additional research, rates of change in soil carbon content can be calculated and predicted for various management practices, and remote sensing and other methods can be used to confirm and calibrate carbon data. Models such as CENTURY are already being used to show changes in soil carbon content over time in areas as large as the continental U.S. Continued work can enhance the accuracy of the data at smaller spatial scales, to ensure accuracy at the field level for individual farmers.
Carbon markets are forming and operating in this country. The concept of emissions trading can provide financial opportunities to farmers who sequester additional carbon (i.e., above “business as usual”) on their lands. Agriculture offers the prospect of sequestering carbon in a low-cost, societally beneficial way for the emerging carbon market. If carbon tons sequestered on agricultural lands are to be traded or sold by farmers, it is important that such issues as baselines, additionality, leakage and permanence be addressed, and that transparent accounting protocols be developed.
 IPCC, (2001), “Third Assessment Report – Climate Change 2001”, The Third Assessment Report of the Intergovernmental Panel on Climate Change, IPCC/WMO/UNEP. Summary for Policymakers @ http://www.ipcc/ch/pub/un/syreng/spm.pdf.
 ibid; U.S. Department of State, U.S. Climate Action Report 2002, Washington, D.C., May 2002. Report at http://www.epa.gov/globalwarming/publications/car/index.html.
 World Meteorological Organization, WMO-No 695, Geneva, 2 July 2003.
 IPCC, (2001), “Third Assessment Report – Climate Change 2001”, The Third Assessment Report of the Intergovernmental Panel on Climate Change, IPCC/WMO/UNEP. Summary for Policymakers @ http://www.ipcc/ch/pub/un/syreng/spm.pdf.
 International Food and Policy Research Institute, 2020 VISION: “Global warming changes the forecast for agriculture,” April 2001. (http://www.ifpri.org/2020/newslet/nv_0401/nv_0401_Global_Warming.htm)
 Rosenzweig, C., A. Iglesias, X.B. Yang, P.R. Epstein, and E. Chivian, “Climate Change and U.S. Agriculture: The Impacts of Warming and Extreme Weather Events on Productivity, Plant Disease, and Pests;” Center for Health and the Global Environment, Harvard Medical School, May 2000.
 U.S. Department of State, U.S. Climate Action Report 2002, Washington, D.C., May 2002. Report at http://www.epa.gov/globalwarming/publications/car/index.html
 Lal, R., R.F. Follett, J.M. Kimble, 2003, pre-publication data.
 Lal, R., J.M. Kimble, R.F. Follett, and C.V. Cole, “The Potential of U.S. Cropland to Sequester Carbon and Mitigate the Greenhouse Effect,” Sleeping Bear Press, Inc., 1998.
 February 10-11, 2003 briefing on Agriculture and Climate Change, sponsored by the National Environmental Trust, the National Academy of Sciences, the Conservation Technology Information Center, the American Society of Agronomy, the Crop Science Society of America, the Soil Science Society of America, and the National Farmers Union; and hosted by Senators Sam Brownback and Tom Harkin, and Congressmen Wayne Gilchrest and John Olver.
 Calculation: [(774 million gal. fuel X 6.1 tons carbon per gal. fuel)/2000 lbs/ton) x 0.907 U.S. tons to metric tons = MMTCE].
 Nishantha, F., G. Watson, C. Rice, J. Kimble, and M. Ranson, “Establishment of Benchmarks for the Measurement and Monitoring of Soil Carbon Sequestration,” pre-publication data.
 Kimble, J.M., R. Lal, and R.F. Follett, eds, “Agricultural Practices and Policies for Carbon Sequestration in Soil,” CRC Press LLC, 2002.