Thanksgiving isn’t about just any old food. It’s about the food that’s native to our land, the food that sustained indigenous people long before Europeans landed on these shores, the food that connects us to the world around us. It’s what we often think of when we talk about sustainable food. But what is sustainable, anyway?

One of the best people to ask is Ruth DeFries. She teaches about sustainable development, land use and food systems at Columbia University (her work has won her a MacArthur Foundation fellowship), and she asks her students that same question: What is sustainable?

To answer, they plan and cook a dinner, made of foods they believe meet the definition. This year, I got to be a dinner guest. I went, notebook in hand, to see what they picked. My date was Miriam Horn, author of “Rancher, Farmer, Fisherman,” a book exploring sustainable practices. We both spend an unconscionable amount of time on this stuff. We talk to each other in the hopes of unburdening our other friends who think that, no, cover crops aren’t fascinating. We talk about no-till, and soil microbes, and complex rotations, and agroecology, and carbon sinks.

After years of talking and writing about all this, I welcomed the chance to hear the ideas of people who don’t eat, sleep and breathe food, and who are younger than your typical agriculture journalist. And, sure enough, their ideas were different. Environmental issues were part of the picture, but the students had a much more expansive definition of sustainability, including social (does everyone eat and enjoy this food?), economic (can people afford it and make a living growing it?) and waste considerations.

Well, that’s a tall order! What was for dinner? Their first plan was dumpster diving, but not everyone found that appetizing. Plan B was a vegetarian menu made mostly of food from a nearby Hudson Valley farm.

When we arrived, they were baking apples (with no sugar, because sugar has to come a long distance). Apples are also reasonably affordable (for fruit) and accessible all year. In the oven was the main dish — shakshuka, made with tomatoes and eggs from the farm. The tomatoes were discounted to $1 per pound because they were on the verge of going bad. Although the students didn’t know the farm’s environmental or labor practices, those unknowns were trumped by the fact that they were saving the tomatoes from the trash. There was steamed broccoli with the shakshuka; they chose fresh rather than frozen because the price was about the same and the fresh had less packaging (although they know there’s less waste associated with frozen vegetables). The only other food was a loaf of whole-grain bread, taken from the day-old shelf. The total cost was $65.22 for a dinner for 18.

But where were the lentils? They seemed to fit so many of the students’ criteria, as well as being a hobby horse of mine. Turned out that one student flat-out refused to eat anything with lentils, so they were off the table.

Though the students used standard numbers to calculate the greenhouse gas emissions for their dinner, there’s no way to take cover crops, or no-till, or any of the other practices that can make a food more sustainable into consideration at the grocery store. We just don’t have the information. Their primary focus was, instead, on the criteria that were tangible: They wanted to minimize waste and buy local.

We can all agree about cutting food waste; it’s a win any way you slice it. But their other priority — buying local — doesn’t contribute much to sustainability by the standard metrics. Throw a spreadsheet at a local farm, and you don’t see an environmental win. Because transport is only a small part of the environmental impact of a food (a tenth or so), it makes more sense to grow food where it can be grown efficiently — where the climate and the soil are congenial — and then ship it. DeFries’s students know this because DeFries knows it and she taught them.

But if you widen the definition of sustainability, as the students did, it matters. We evolved as a species making food acquisition a top priority, right up there with sex. A connection to food is literally in our DNA, and we’ve mostly lost it. Thanksgiving, for a lot of people, is a chance to get it back. The fact that buying locally has become important to people is a sign that it’s important, DeFries told me.

It’s hard to factor that into the spreadsheet. How do you convert reconnection to CO2-equivalents? “It’s a very non-hard science,” said DeFries. “Our entire evolutionary history is cooperating to produce food, eating what we like and making sure everybody is enjoying it.” Her students’ priorities are our evolutionary endowment.

DeFries is a scientist, and she’s quick to point out that, no matter how important the connection is, it can’t be our only consideration. “If everybody ate locally from the Hudson Valley, there’d be a lot less forest in the Hudson Valley,” she said. That’s not a good thing. But neither can we just run our sustainability metrics and expect the outcome to guide people’s choices. “I used to feel conflicted between the scientific rationale and the need for the visceral connection,” she told me. “Now I don’t. I realize that connection is part of who we are as a species.”

I get why local (and also organic) agriculture resonates with consumers even when they can’t get too excited about cover crops. DeFries, Horn and I all go out of our way to buy from local farms, carbon footprint be damned. This is visceral, not analytical. To ask people to sacrifice that because local farms have a higher greenhouse gas cost or organic has lower yields is to miss the point.

My husband and I are very connected to our food. We raise pigs, turkeys and chicken. We grow some of our fruit and veg. We catch our own fish, we hunt our own venison. And we farm oysters.

Except for the farm, none of this is particularly planet-friendly. We fish from a boat powered by gasoline. To hunt, we take our F-250 all the way to Virginia from Massachusetts. We drive to the feed store to buy animal feed in 50-pound plastic bags. And on and on. Break out the carbon spreadsheet and the picture isn’t pretty, but that’s not why we do all this.

Don’t get me wrong. I value the spreadsheet. I write about it all the time. I want to find ways to bring the numbers down. But the satisfaction I find in feeding my friends and family food that I’ve grown or harvested with my own two hands has nothing to do with that.

People like that feeling, which is why I don’t expect consumers to make wonky sustainability measures a top priority. But DeFries has a suggestion for what they can do instead: “Support leaders who can have information about production systems and can make the incentive structures that line up to, say, water use.” By expecting consumers to vote at the grocery store, she said, “we’re asking people to be involved at the wrong entry point.” Vote at the voting booth. Shop at the grocery store.

There was one more sustainability issue the students tackled; DeFries encouraged them to use the metric of prep time, intending it to be low. But one of the students, whose family came from Mexico, turned it on its head. For her, part of being sustainable was making sure there was something for everyone to do in preparing the meal. The more chopping, the better.

Yes, carbon is important, but it seems weird to give thanks for a reduction in greenhouse gases. Connection is important, too. So is community. Those are what sustain us.

Haspel writes Unearthed, a monthly commentary in pursuit of a more constructive conversation on divisive food-policy issues. She farms oysters on Cape Cod.

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