Part III Managing Natural Sinks of CO2

Water, Air, and Soil Pollution

, Volume 64, Issue 1, pp 121-137

First online:

On estimating agriculture's net contribution to atmospheric carbon

  • R. B. JacksonIVAffiliated withU.S. Environmental Protection Agency

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Fossil fuel combustion, chlorofluorocarbon releases, and agricultural activities (including deforestation) are the primary anthropogenic sources of greenhouse gases. Of the three sources, agriculture is the only one that also has a sink capacity. Thus, an accounting of the net carbon (C) flux is required to properly evaluate agriculture's contribution and to determine the opportunities for emissions mitigation through changes in agricultural practices. Common data sets and a standard accounting method are required to perform country-by-country net C analyses. This research used agricultural census data to determine that U.S. agriculture removed 1.3 Pg of CO2 from the atmosphere, in 1987, in the plants that it produced. The turnover times and the fate of this C were not ascertained. The research also showed that 6.4 Tg of CO4 was emitted from live U.S. agricultural animals. A net C flux was computed, but is incomplete, because rice CO4, plant and animal waste CO4 and CO2, and soil-atmosphere C fluxes could not be estimated from the census data. Additionally, agriculture's net contribution to atmospheric C was found to depend critically on the boundaries of the analysis.