Today’s topic is a response to a comment by Aron, a reader who asked me to explain why I remarked that lower food miles do not necessarily imply that local food has a small environmental impact.
One of the standard arguments for consuming local foods is that, by reducing food miles, we are lowering the carbon footprint of our food consumption. In other words, local food has a smaller impact on climate change.
There is a body of literature that examines the relationship between food production (including local food) and emission of greenhouse gases (GHG). A list of a few articles on the topic is articles is below; note this is not a comprehensive list. The basic premise of most of the research is that most GHG emissions occur when food is being produced. In fact, Weber and Mathews (2008) estimate that 83% of a US household’s annual GHG emissions (related to food consumption) are due to production, and 11% due to transportation of food. Across all types of food, livestock production emits the most GHG (specifically methane and nitrous oxide). They suggest a more effective way to reduce your carbon footprint: eat less red meat.
The literature on organic food and climate change finds that organic livestock production is less degrading to climate change, because it is pasture based (captures carbon) and has small herds. The closed loop system means that the pasture is fertilized by the manure excreted by the grazing animals: the manure is recycled, plants grow, and the animals feed on the plants. And then the loop continues, as the animals excrete manure, and so on. In contrast, the waste excreted by animals in the non-pasture systems must be discarded.
I do wonder, though, if you are a vegetarian, does the balance re: food miles change?
- “Food-Miles and the Relative Climate Impacts of Food Choices in the United States” Christopher L. Weber and H. Scott Matthews, Environmental Science & Technology 2008 42 (10), 3508-3513
- “Food, livestock production, energy, climate change, and health.” AJ McMichael, JW Powles, CD Butler… – The Lancet, 2007 – Elsevier
- ”Agricultural sustainability and farm production practices.” David Tilman, Kenneth G. Cassman, Pamela A. Matson, Rosamond Naylor & Stephen Polasky. Nature. Aug. 2002. Vol. 418.