You may have noticed it yourself, or heard someone else remark, that the winters don't seem to be as harsh as they used to be, or that spring comes earlier and earlier every year, or that the summers seem to be getting longer and hotter. While you may say that these are the result of a "phase" or "cycle" our planet is going through, research suggests that human activities are beginning to change the overall climate of our planet.

Climate Change and the Greenhouse Effect

The composition of the Earth's atmosphere primarily determines the planet's temperature and establishes the conditions and limits for all life on Earth. The "greenhouse effect", a term for the role the atmosphere plays in warming the earth's surface, occurs when incoming solar radiation penetrates the atmosphere, but much of this radiation is held within the earth's atmosphere by "greenhouse gases" such as carbon dioxide, methane, and ozone.

In proper balance, this process maintains the earth's temperature in a range that is hospitable to life. However, through increased human activity since the era of industrialization, the volume of greenhouse gases has increased substantially. This could lead, and some scientists believe already has, to an increase in global temperature that may progress to serious change in weather patterns, vegetation zones, ocean level and other factors.

Why would this be a concern to agricultural producers?

Agriculture in the United States has been flexible in the past and has adapted to weather fluctuations: farmers change their crops or varieties of crops, plant and harvest times, and use of fertilizers, pesticides, and irrigation. And, overall, it has worked. Studies of the potential impacts of climate change on agriculture indicate that we will continue to be able to feed people in our country and others throughout the world.

For individual farmers, however, climate changes could be disruptive and expensive. While elevated levels of carbon dioxide in the atmosphere may increase crop growth, changes in climate may cause yield reductions or crop losses.

How do agricultural activities contribute to the Greenhouse Effect?

American agricultural activities contribute only about 7.3% of the total U.S. contribution of greenhouse gases. The major sources are: methane from cattle, animal waste and rice cultivation; nitrous oxide from fertilizers and pesticides; and, carbon dioxide from vehicle and farm equipment exhaust, deforestation and conventional plowing.

Many practices adopted by agricultural producers also reduce emissions of greenhouse gases to the atmosphere and thereby help slow climate change. Among these are:

  • Conserving fuel by limiting the number and intensity of field operations.
  • Using conservation or no-till cultivation systems to reduce carbon dioxide emissions from the soil.
  • Using soil tests to determine when and where to apply nitrogen fertilizers. Using less nitrogen fertilizer can decrease emissions of nitrous oxide.
  • Management of grass-based animal production systems using, for example, rotational grazing and improved forages. This decreases methane emissions from ruminant animal production.
  • Using methane-recovery systems for liquid manure, such as digeters or covered lagoons, to reduce methane emissions and provide on-farm sources of biogas fuel for large livestock operations.
  • Producing "biofuels" as a substitute for fossil fuels to reduce net carbon dioxide emissions. Plant material can be burned to generate energy or can be converted into fuels. Potential biofuels include traditional agricultural crops (such as corn and soybeans), dedicated biofuel crops (such as switchgrass and short-rotation trees), and byproducts of food and fiber processing.

Carbon dioxide is the most prevalent of the major greenhouse gases. Of all sources of carbon dioxide in the U.S., 98.5% is from the combustion of fossil fuel. (The most common fossil fuels are coal, oil (also called petroleum) and natural gas. Some other fuels, like oil shale and peat (a very young form of coal), also are part of the fossil fuel family. These fuels were formed millions of years ago from plants and animals that died and decomposed beneath tons of soil and rock.)

How can agricultural producers store carbon?

Storing, or "sequestering," carbon in soil as organic matter and in trees helps reduce the amount of carbon dioxide in the atmosphere. This is why soil and vegetation are sometimes called carbon "sinks." Conservation practices that increase carbon storage include:
  • Using conservation or no-till cultivation systems.
  • Rotating crops and incorporating small grains, hay, legumes, or other crops into rotations.
  • Planting cover crops.
  • Minimizing or eliminating summer fallow.
  • Managing nutrients and irrigation efficiently and effectively.
  • Applying manure, compost, and other organic amendments according to nutrient management plans.
  • Improving pasture and rangeland soils through grazing, vegetation, and fire management.
  • Installing permanently vegetated conservation buffers, such as windbreaks, grass waterways, filter strips, and riparian buffers.
  • Restoring and protecting wetlands.
  • Converting marginal agricultural land to perennial grassland or forest.
  • Managing woodlands to conserve soil and increase biomass.
  • Adopting agroforestry practices that incorporate trees into agricultural operations.
Some of the practices that decrease greenhouse gas emissions or sequester carbon require a capital investment or increase farm-operating costs. The federal Conservation Reserve Program (CRP), the Wetlands Reserve Program (WRP), and the Environmental Quality Incentives Program (EQIP) provide assistance to help farmers adopt these beneficial practices.

How much carbon could actually be sequestered through these activities?

The total carbon sequestration and fossil fuel offset potential of US cropland is estimated at 154 million metric tons of carbon per year or 133 percent of the total emissions of greenhouse gases by agricultural and forestry activities. While our lands can be managed to increase carbon storage, the increase can only temporarily offset greenhouse gas emissions. Many view land-based carbon sinks as buying valuable time to address the more significant challenge- reducing greenhouse gas emissions.

Could carbon be marketed?

The desire to slow human-caused climate changes has spurred nations to adopt international climate change agreements. The first of agreement, the 1992 Framework Convention on Climate Change (the Rio Treaty), requires all countries to identify, inventory, and work voluntarily to reduce greenhouse gas emissions. The United States ratified this treaty in 1992 by a unanimous vote of the US Senate.

A second agreement that is under consideration but has not yet been approved is the 1997 Kyoto Protocol. Under the Protocol, agreed in Kyoto, Japan in 1997, 39 industrialized nations must cut emissions of six greenhouse gases to an average of 5.2 percent below 1990 levels by the period 2008-2012. The Protocol will not take effect until it is ratified by 55 percent of the nations emitting at least 55 percent of the greenhouse gases - carbon dioxide (CO2), methane, nitrous oxide, hydrofluorocarbons, perfluorocarbons and sulphur hexafluoride.

A climate agreement or domestic legislation could allow the United States and other nations to meet greenhouse gas emissions targets by a variety of means, so that they could choose the most cost-effective options. One might be to give credits to agricultural producers who increase their stores of carbon in the soil or in trees. Producers could then save the credits or sell them to others (utility companies, for example) that want them in order to offset their own greenhouse gas emissions.

Earning credits for storing more carbon would provide an additional source of income for agricultural producers - a carbon crop.

Back To Top

Home || Agriculture || District || Education || Land Trust
Links || Stormwater || Urban
Private Woodland Owners