There are lots of good reasons to buy local, but don't worry about the impact of shipping.
For some years we have been eating mostly a local and seasonal diet, worried about the carbon footprint of transporting all that food across or between continents. It can get quite monotonous; when spouse Kelly Rossiter was writing for TreeHugger about this, it was a diet of potatoes and turnips and more turnips. As I try to live a 1.5 degree lifestyle we have been eating this kind of diet again as I count my carbon, and have already discussed the huge footprint of red meat. However, Hannah Ritchie of Our World In Data, out of Oxford University, has published data that show we can worry about the seasonal, but relax about the food miles. She writes:
‘Eating local’ is a recommendation you hear often – even from prominent sources, including the United Nations. While it might make sense intuitively – after all, transport does lead to emissions – it is one of the most misguided pieces of advice.... GHG emissions from transportation make up a very small amount of the emissions from food and what you eat is far more important than where your food traveled from.
Really. I literally just had this for lunch, a yummy Autumn Root Vegetable Gratin with Herbs and Cheese, because it's made from good old local non-refrigerated potatoes, turnip and parsnip, because Kelly is supporting me in the 1.5-degree diet. Now, the net can be a little bit wider. But we have always said that eating seasonally was more important than eating locally (no hot-house tomatoes, please) and Ritchie confirms it:
There are also a number of cases where eating locally might in fact increase emissions. In most countries, many foods can only be grown and harvested at certain times of the year. But consumers want them year-round. This gives us three options: import goods from countries where they are in-season; use energy-intensive production methods (such as greenhouses) to produce them year-round; or use refrigeration and other preservation methods to store them for several months. There are many examples of studies which show that importing often has a lower footprint.
My late mom always thought that getting asparagus in winter was the greatest luxury, and of course I would complain about the air freight. But Ritchie confirms that this is the one kind of well-traveled food that we really should avoid, noting that the asparagus had a shipping footprint 50 times as high as produce that comes by boat.
Living in North America where most of the food travels by truck, I worried that her data would not be as relevant here, but in fact, American researchers came to the same conclusion:
By analysing consumer expenditure data, the researchers estimated that the average American household’s food emissions were around 8 tonnes of CO2eq per year. Food transport accounted for only 5% of this (0.4 tCO2eq). This means that if we were to take the case where we assume a household sources all of their food locally, the maximum reduction in their footprint would be 5%.
And their diet would be a lot more boring. I also questioned whether this included the whole cold chain, the refrigerated warehouses and trucks that move it all across the continent, and even the packaging it comes in; it's all teensy, compared to the impact of land use and farm emissions.
From an emissions point of view, the single biggest thing you can do is give up red meat, no matter how it is raised, then lamb, and then cheese, if you are counting emissions per kilogram of food. But as my cheesemonger daughter keeps reminding me, you can't compare a kilo of cheese to a kilo of apples; the caloric and carbon densities are totally different.
And it turns out, she is right; Our World in Data has a table for that, too, measuring emissions per 1000 kilocalories, where the order changes significantly. Now shrimp is off the menu (it was anyway because of the way it is harvested) and cheese is down there with the chickens, weirdly lower than tomatoes.
I still believe there are lots of good reasons to go local; it supports the local farmers and the regional economy. California strawberries are a drain on water resources and taste like wood, so we eat them seasonally. Our household rule is that if it grows here (in Ontario, Canada) then we wait until we can eat the local version, but I still get to have a grapefruit for breakfast and some guacamole at lunch.
Clearly the greenest diet of all is to go vegan, hold the tomatoes. But if your dietary choices are based on your carbon footprint, dropping the red meat is the single most important thing you can do, no matter what the American Meat Institute tells you.
And it's nice to know that I can enjoy my grapefruit and not fret about its travel footprint. It's one less thing to worry about.