<b>Hristov</b>, A. N., J. M. F. <b>Johnson</b>, C. W. Rice, M. E. Brown, R. T. Conant, S. J. Del Grosso, N. P. Gurwick, C. A. Rotz, U. M. Sainju, R. H. Skinner, T. O. West, B. R. K. Runkle, H. Janzen, S. C. Reed, N. Cavallaro, and G. Shrestha, 2018: Chapter 5: Agriculture. In Second State of the Carbon Cycle Report (SOCCR2): A Sustained Assessment Report [Cavallaro, N., G. Shrestha, R. Birdsey, M. A. Mayes, R. G. Najjar, S. C. Reed, P. Romero-Lankao, and Z. Zhu (eds.)]. U.S. Global Change Research Program, Washington, DC, USA, pp. 229-263, https://doi.org/10.7930/SOCCR2.2018.Ch5.
A number of social and economic factors drive CO2 and other GHG emissions associated with agriculture (see Table 5.1), including dietary preferences and traditions; domestic and global commodity markets; federal incentives for conservation programs; and technical capabilities for production, processing, and storage in different geographic regions. For example, policies and economic factors that influence bioenergy and biofuel feedstock production systems have diverse direct and indirect impacts on the carbon cycle as discussed later in this chapter and in Ch. 3: Energy Systems. A biofuel’s carbon footprint depends on the feedstock and its associated management as well as the efficiency of the eventual energy produced from the feedstock. Changes in the management of these social and economic factors can affect soil carbon sequestration and storage and agricultural GHG emissions. Another driver of changes in agricultural production systems is consumer demand for types of food (e.g., meat versus dairy versus vegetable) and provenance of food (e.g., grass-fed, organic, and local). Such influences can have both negative and positive effects on the carbon cycle in direct and indirect ways (see Box. 5.1, Food Waste and Carbon). Decision support tools have been developed over the last decade to address agricultural impacts on climate and environmental drivers that play a role in the carbon cycle (for examples, see Ch.18: Carbon Cycle Science in Support of Decision Making).
Table 5.1. Greenhouse Gas Fluxes from North American Agriculture
(Teragrams of Carbon Dioxide Equivalent per Year)
|Emission Source||Canadaa||United Statesb||Mexicoc||Total by Source|
|Agricultural Soil Management||24d||295.0||0||318.0|
|Liming, Urea Application, and Others||3||8.7||7.5g||19.2|
|Field Burning of Agricultural Residues||0||0.4||1.3||1.7|
|Total by Countryh||60||566.9||79.9||705.8|
a Source: ECCC (2018); data for 2016.
b Source: U.S. EPA (2018); data for 2015.
c Source: FAOSTAT (2017); average data for 1990–2014.
d Includes emissions from field burning of agricultural residues.
e Not reported.
f Includes manure applied to soils, manure left on pasture, and manure management.
g Synthetic fertilizer.
h As reported in source; may not match sum of individual emission categories due to rounding.
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