Is Local Food More Environmentally Friendly?The GHG Emissions Impacts of Consuming Imported versus Domestically Produced Food

摘要

With the increased interest in the 'carbon footprint' of global economic activities, civil society, governments and the private sector are calling into question the wisdom of transporting food products across continents instead of consuming locally produced food. While the proposition that local consumption will reduce one's carbon footprint may seem obvious at first glance, this conclusion is not at all clear when one considers that the economic emissions intensity of food production varies widely across regions. In this paper we concentrate on the tradeoff between production and transport emissions reductions by testing the following hypothesis: Substitution of domestic for imported food will reduce the direct and indirect Greenhouse Gas (GHG) emissions associated with consumption. We focus on ruminant livestock since it has the highest emissions intensity across food sectors, but we also consider other food products as well, and alternately perturb the mix of domestic and imported food products by a marginal (equal) amount. We then compare the emissions associated with each of these consumption changes in order to compute a marginal emissions intensity of local food consumption, by country and product. The variations in regional ruminant emissions intensities have profound implications for the food miles debate. While shifting consumption patterns in wealthy countries from imported to domestic livestock products reduces GHG emissions associated with international trade and transport activity, we find that these transport emissions reductions are swamped by changes in global emissions due to differences in GHG emissions intensities of production. Therefore, diverting consumption to local goods only reduces global emissions when undertaken in regions with relatively low emissions intensities. For non-ruminant products, the story is more nuanced. Transport costs are more important in the case of dairy products and vegetable oils. Overall, domestic emissions intensities are the dominant part of the food miles story in about 90 % of the country/commodity cases examined here.