In this study, a greenhouse gas emissions model for primary agriculture is extended to the agriculture and agri-food sector in order to examine the full impacts of the sector on greenhouse gas emissions. To accomplish this, methods for predicting emission levels are cast within a systems framework which includes both forward and backward linkages of agriculture production, as well as indirect and agroecosystem related emissions. Such an approach will assist policy-makers in evaluating the full impacts of the sector on greenhouse gas increase in the atmosphere. The model estimates that greenhouse gas emissions from primary agriculture in 1990 were 58 million tonnes of CO, equivalents, whereas if the entire agriculture and agri-food system is considered the estimate increases to 90 million tonnes. Estimates for 2010 indicate a substantial increase in greenhouse gas emissions under a business as usual scenario to 65 Mt for primary agriculture and 103 Mt for the entire agri-food system. The implications of using a systems approach for analyzing possible mitigation strategies targeted at reducing greenhouse gases from the agricultural sector are significant. Agriculture has significant impact on emissions beyond the farm gate, and in the context of national greenhouse mitigation strategies, such should not be ignored. Another implication of these results is the role of sinks for Canadian agriculture. Based on projections of a business as usual scenario, Canadian soils provide a third of the potential reduction of all greenhouse gases for the agriculture and agri-food sector for the commitment period. Since agricultural soils as sinks of carbon have yet to be recognized, this raises the important issue of how primary agriculture in Canada would meet its target of decreasing greenhouse gas emissions. The systems approach as demonstrated in this paper warrants a serious consideration for the policy decision-making process at both national and international levels.
