Local Food and Climate Change

The result of this math is that huge shipments of millions of apples from far-away places like New Zealand are comparable in emissions to apples grown in Canada and transported to the consumer in many small trucks (see apple scenario in MacCrae et al. 2013, cited below). Trains are also efficient modes of transportation compared to trucks.

Air-freighted foods generate much higher emissions than other modes of transportation, but only 1-2% of foods use this mode, and account for about 0.16% of total food transportation emissions (Ritchie and Rose, 2020). Because air-freighted foods aren’t labeled, it’s hard to know which to avoid, but they’re often more expensive, highly perishable foods like asparagus and fresh fish/seafood from far away that cannot travel by boat.

Cold climate

Several studies have compared produce grown in heated greenhouses with produce imported  from warmer climates. These studies consistently show that food grown in warmer conditions that are shipped have lower emissions than food grown in heated greenhouses with lower food miles. Even when efforts are made to lower energy use (insulation, biomass fuel), the comparisons still favour foods imported from warmer climates. In a Canadian context, MacCrae et al show that greenhouse-grown lettuce and tomatoes from Leamington, Ontario emitted 25 times as much greenhouse gas as field-grown lettuce and tomatoes in California. Once the transportation emissions were accounted for, the Leamington produce generated 4 times the emissions of the California produce. In this scenario, buying local generates more emissions.

Energy efficiency measures can lower emissions from greenhouses, but it’s not enough to make up for the large amount of energy needed to create a warm climate in a cold country. Two operations in British Columbia that had invested in energy efficiency technology, like switching from coal or natural gas to biomass, were still not enough to compensate for the large amounts of energy needed (MacCrae et al, 2013). The authors conclude that there may be ways to reduce emissions further in greenhouses, but that this would decrease yields, which would not be high enough to make them competitive. This finding comes from 2013, so it’s possible that over the last decade, greenhouse technology and energy sources have improved. For more on ways that greenhouse production could be less energy intensive (in an Ontario context), see Dias et al, 2016.

Growing conditions

Another way to think about this issue is that we’ve previously concentrated on a narrow window of the food system: the last stage of the food’s journey to get from the farm to the consumer. What we’ve missed is a key part of ecology–crops grow efficiently when they’re grown in conditions that they are adapted to. Sourcing food from wherever it grows best means that we are working with nature rather than against it (i.e. with heated greenhouses or more fertilizer and other inputs). A co-benefit is that more people around the world can have a varied diet year-round (even in cold places like Canada). This is sometimes called "global seasonality" in food emissions research.

What about local, field-grown produce that’s in season?

The “buy local, seasonal produce” message does not account for the comparative advantages that certain regions have in producing specific foods very efficiently, and the ways in which this is connected to environmental impacts. For example, in California, one hectare of land will yield over 50,000kg of strawberries, whereas the same amount of land in Ontario will yield only 7000kg. (Desrochers & Shimizu, 2010). When the yields are lower and the conditions are less favourable for a plant, in general more inputs and land are needed and the overall system is less efficient (i.e., more emissions for less food produced). When less land is used for agriculture, it may be rewilded or reforested, contributing to carbon sinks and biodiversity.

For some places in Canada, there are likely some foods that can be field-grown (or livestock raised) with low inputs, giving them a similar emissions profile as imported foods. The problem, though, is that these differences are usually small, so even when all of the best-case criteria are in place, this will not make a meaningful difference to the food's carbon footprint or an individual’s food-related emissions. One study found that even when local, seasonal food had slightly lower emissions, this benefit would be offset if the consumer had to drive a round-trip of more than 6.7km in a car to get to the producer or farmers market for that single food item (Coley et al., 2009).

Overall, there are a few reasons we do not recommend the "buy local, seasonal" message for climate change mitigation at Drawdown Dietetics:

• The potential for emissions reduction is very small, so it is not strategic

• It's difficult (maybe impossible) for consumers to figure out at the retailer when the best-case scenario is met (efficient mode of transportation, low inputs, a food that grows well in their region/growing zone and has not used heated greenhouses)

• There are no regulations or agreed-upon definitions of the terms "local" or "seasonal," making them vague concepts to use as a proxy for sustainability. For example, what do we mean by local? Some researchers use climatic zones or countries as boundaries, but given that trucks are high-emissions modes of transportation, this leaves it open for many small trucks travelling around even a single province and generating much more emissions than foods travelling long distances by boat. What do we mean by seasonal? If seedlings are grown in a heated greenhouse before being planted in a local field, are they “in season?” 

• There's evidence that consumers are being misled by the message: they may believe that it's more impactful to buy local, seasonal produce than to reduce meat from ruminant animals or to waste less food. This is the opposite message we get from the research.

These factors are mainly relevant for fruits and vegetables. What about other foods that can be purchased locally?

Beef: Mostly comes from Alberta, and Canadian beef is raised more efficiently than in other regions of the world. Unfortunately, beef is a very high-emissions food, even when raised efficiently (see graphic below). The transport emissions from beef are often 1% or less of the total amount, so the food miles of beef are not worth targeting for climate change.

Other animal foods like pork and chicken: emissions mainly come from growing the feed crops needed to raise livestock and the manure produced. Buying these locally may or may not be more climate-friendly than imported meats—again, a focus on reducing food miles isn’t strategic.

Dairy is supply-managed in Canada, so there are few or no imported options for these products.

Grains (except rice) and pulses: these are mostly from Canada (in the prairies), but because these foods have such low emissions, reductions in food transport emissions would likely not make much difference to the total.

If food transport doesn’t have much impact on emissions, where do all the food emissions come from? 

The visualized data below helps us to see the bigger picture of food emissions (transport emissions in red). The biggest share of emissions comes from enteric fermentation of ruminant animals like cows, sheep, and goats, land use change (large amounts of land are dedicated to growing feed crops for livestock, sometimes driving deforestation around the world). For fruits and vegetables, it’s mainly nitrogen fertilizers and pesticides driving emissions.

Still have questions, comments, or concerns about local food? We know this goes against what we’ve heard for a long time in nutrition, and understand that this information may cause confusion. You can see the evidence at the citations listed below, and access our recorded webinar on this topic here.

Citations and some evidence from the research

Dias, G.M.; Ayer, N.W.; Khosla, S.; Van Acker, R.; Young, S.B.; Whitney, S. & Hendricks, P. (2017). Life cycle perspectives on the sustainability of Ontario greenhouse tomato production: Benchmarking and improvement opportunities. Journal of Cleaner Production, 140: 831-839.

Ritchie & Roser (2020). "Environmental Impacts of Food Production". Published online at OurWorldInData.org. Retrieved from: 'https://ourworldindata.org/environmental-impacts-of-food' [Online Resource]. See especially their analysis of food transportation emissions: https://ourworldindata.org/environmental-impacts-of-food#you-want-to-reduce-the-carbon-footprint-of-your-food-focus-on-what-you-eat-not-whether-your-food-is-local

Stein, A.J. & Santini, F. The sustainability of “local” food: a review for policy-makers. Rev Agric Food Environ Stud 103, 77–89 (2022). https://link.springer.com/article/10.1007/s41130-021-00148-w

MacRae, R.; Cuddeford, V.; Young, S.B. & Matsubuchi-Shaw, M. (2013). The Food System and Climate Change: An Exploration of Emerging Strategies to Reduce GHG Emissions in Canada, Agroecology and Sustainable Food Systems, 37:8, 933-963, DOI: 10.1080/21683565.2013.774302

Articles on local seasonal food

Department of Environmental Food and Rural Affairs (DEFRA) U.K. (2012). “Understanding the environmental impacts of consuming foods that are produced locally in season.” Summarized and accessible at https://tabledebates.org/research-library/defra-report-fo0412-understanding-environmental-impacts-consuming-foods-are

David Coley, Mark Howard, Michael Winter. (2009). Local food, food miles and carbon emissions: A comparison of farm shop and mass distribution approaches. Food Policy, Volume 34, Issue 2, 2009, Pages 150-155, ISSN 0306-9192, https://doi.org/10.1016/j.foodpol.2008.11.001. [Online Resource]. https://www.sciencedirect.com/science/article/pii/S0306919208000997.

Desrochers & Shimizu (2010). Will buying food locally save the planet? Montreal Economic Institute: Economic Note. https://www.iedm.org/files/note0210_en.pdf

Research updates

A big, new study was published in the journal Nature Food recently that, at first glance, contradicts our position that food miles are not an issue to focus on with climate change:

• (Li et al, 2022) "Global food-miles account for nearly 20% of total food system emissions."

The authors of this study made an unusual decision to label all transportation emissions within the food system as "food miles." That is, the total emissions from transporting inputs like fertilizer and compost to the farm, as well as the generally understood definition of "food miles"--only the emissions generated from final delivery from the farm to the consumer. The problem is that this over-estimates the environmental benefits of buying local food. It makes it sound like localizing the food system could reduce its emissions by 20%. But even the authors of this study acknowledge that consumers buying local would not affect most of the total food transportation emissions they included in their calculations, since the total transportation emissions of local food systems would not be changed much if farms were closer to consumers. If a farm is close to a consumer, that farm will still need to import any inputs used in production; only the emissions from the final journey would be reduced (even then, the emissions may not be reduced relative to farms farther away, depending on yields, scale, and mode of transportation as shown above). There is a response here for more details.