My wife just came in from the garden with an autumn bounty of vegetables grown about 100 yards from our front door—kale, broccoli, carrots and tomatoes. During the next few weeks, we will also store a few potatoes, garlic and squash for the winter. Our food production brings the comfort of knowing that we used no pesticides, GMO varieties, and industrial fertilizer. Indeed, some gnarly looking vegetables reassure that view; you would never see such specimens in the local supermarket.
Meanwhile, when we shop in the farmer’s market of our small town, we know that we are supporting the local farm economy, keeping small farms nearby. Farms maintain a green, pastoral landscape that we all enjoy, versus the alternative of increasing suburban sprawl. And locally produced foods avoid the energy costs of shipping.
But, come winter, we will increasingly depend on supermarket fruits and vegetables, grown in California and South America. There seems little doubt that these will require more energy to ship to us than the vegetables we grow ourselves. Consuming blueberries grown in Chile in January carries a cost in energy used in air transport, but also a benefit to our nutrition. Just how significant is the energy cost of transport, relative to the energy used to grow crops?
A 2008 study found that for the U.S., the average foodstuff travels 1640 km from the farm to our table. Some modes of transport, such as trucking fruits and vegetables are relatively energy intensive. Other forms, such as the international transport of grains in ocean ships are relatively benign. All transport uses some energy, but the study indicates that 83% of the energy to supply food to our table was used in the production phase—the rest in transport.
Consistent with my recent post on the consumption of beef (Citizen Science, September 20, 2016), dietary shifts—for example, away from meat—could have substantially more impact on reducing energy use than would consuming only local produce. And as we come to understand that caloric intake has a greater impact on obesity than differences in metabolism, we might also choose to eat more modestly and thereby lower our impact on the environment.
The benefits of local versus agro-industrial food production, relevant now to our own interest in minimizing environmental impact, will become increasingly important as population rises in regions of the world that have little potential to feed themselves and as climate change impacts food production globally. With proper motivation much of the U.S. could feed itself locally, but we certainly shouldn’t expect the entire world to forsake adequate nutrition for energy savings. Some types of food can be grown more efficiently overseas and shipped to the point of use, with less overall energy use.
Enjoy locally-grown foods. They are healthy and restful to produce. But let’s be realistic about the environmental benefits of locavory in an increasingly globalized and overpopulated world.
References
Avetisyan, M., R. Hertel, and G. Sampson. 2014. Is local food more environmentally friendly? The GHG emissions impacts of consuming imported versus domestically produced food. Environmental and Resource Economics 58: 415-462.
Billen, G., S. Barles, J. Garnier, J. Rouillard, and P. Benoit. 2009. The food-print of Paris: long term reconstruction of the nitrogen flows imported into the city from its rural hinterland. Regional Environmental Change 9: 13-24.
Cleveland, D.A., C.N. Radka, N.M. Mueller, T.D. Watson, N.J. Rekstein, H.V. Wright, and S.E. Hollingshead. 2011. Effect of localizing fruit and vegetable consumption on greenhouse gas emissions and nutrition, Santa Barbara County. Environmental Science and Technology 45: 4555-4562.
Fader, M., D. Gerten, M. Krause, W. Lucht, and W. Cramer. 2013. Spatial decoupling of agricultural production and consumption: Quantifying dependences of countries on food imports due to domestic land and water constraints. Environmental Research Letters 8:doi:10.1088/1748-9326/8/1/014046
Michalsky, M. and P.S. Hooda. 2015. Greenhouse gas emissions of imported and locally produced fruit and vegetable commodities: A quantitative assessment. Environmental Science and Policy 48: 32-43.
Pontzer, H., D.A. Raichlen, B.M. Wood, A.Z.P. Mabulla, S.B. Racette and F.W. Marlowe. 2012. Hunter-gatherer energetic and human obesity. PLoS One 7: e40503
Schmitz, C., A. Biewald, H. Lotze-Campen, A. Popp, J.P. Dietrich, B. Bodirsky, M. Krause and I. Weindl. 2011. Trading more food: Implications for land use, greenhouse gas emissions, and the food system. Global Environmental Change 22: 189-209.
Webber, C.L. and H. S. Matthews. 2008. Food-miles and the relative climate impacts of food choices in the United States. Environmental Science and Technology 42: 3508-3513.
Zumkehr, A. and J.E. Campbell. 2015. The potential for local croplands to meet US food demand. Frontiers in Ecology and the Environment 13: 244-249.
You say “But, come winter, we will increasingly depend on supermarket fruits and vegetables, grown in California and South America.”. Get yourself a copy of Putting Food By – http://www.amazon.com/Putting-Food-By-Fifth-Edition/dp/0452296226. You can eat your kale and broccoli in January if you blanch and freeze.
WADR, if you really care about food miles, then you must save your harvest. If your harvest isn’t sufficient, use local sources for putting by.
Unfortunately, it is not as simple as you suggest. If one preserves locally grown produce, one must discount the energy savings by not importing distant food by the energy used to prepare and store local food for later consumption. One analysis suggests that keeping local apples in cold storage for the winter about balances the energy used to transport fresh apples from abroad. I suspect the same is true of blanched kale and broccoli in the freezer.
In any case, my blog means to focus on the comparative energy costs in food production versus shipping, with the former dominating the total energy balance in most cases. Shipping food does use energy, but the real question with whether it is worse than alternatives.