Local, Seasonal, or Plant-Based? What the Lifecycle Data Actually Says About Your Greenest Plate

There is a comfortable story we tell ourselves in the supermarket: the closer the food was grown, the better it is for the planet. Buy local, cut the “food miles,” shrink your footprint. It is intuitive, it feels virtuous, and — for most of what ends up on your plate — it is mostly wrong.

The honest version is less flattering to the shopper and more useful: what you eat matters far more than how far it travelled. And once you accept that, a few genuinely counter-intuitive things follow.

The food-miles instinct is measuring the wrong thing

The single largest study of food’s environmental impact — Poore and Nemecek’s 2018 analysis in Science1, covering ~38,700 farms across 119 countries — found that transport is a small slice of most foods’ total footprint. For the average product it is under 10% of emissions; for beef, transport is roughly half of one percent. The overwhelming majority of the damage happens on the farm, long before anything is loaded onto a truck.

That reframes the whole question. As Our World in Data puts it2, cutting red meat and dairy for just one day a week does more for your food footprint than sourcing your entire diet locally. The gap between foods dwarfs the gap between distances: a kilogram of beef carries on the order of 60 kg of CO₂-equivalent; a kilogram of peas, roughly one. No amount of buying local closes a sixty-fold gap.

Bold takeaway: if you only change one thing, change the ingredient, not the postcode it came from.

The tomato that breaks the local rule

Here is where our own data earns its keep. Using Swiss lifecycle-assessment figures — Agroscope’s comparison of domestic versus imported products (Bystricky et al., 2014)3, the AGRIBALYSE database4, and MeteoSwiss seasonality — a specific, uncomfortable result appears: a local tomato grown out of season in a heated greenhouse can emit more than an imported one grown in season under natural sun.

The reason is energy. In a cold-climate greenhouse, heating can account for the large majority of a vegetable’s production footprint. A 2025 Swiss greenhouse lifecycle study5 reaches the same conclusion our data does: when you burn gas to fake summer, “local” stops being green. An in-season import — grown where the sun was already doing the work for free — can carry lower emissions than the heated tomato from down the road.

So “local” is not a synonym for “sustainable.” “Local and in season” is the claim the data actually supports. Buying a Swiss strawberry in December is not the environmental win it feels like.

What actually moves the needle

Strip away the virtue-signalling and three moves survive contact with the evidence:

• Eat less of the high-impact foods — beef and lamb above all. This is the lever with by far the longest handle.
• Eat with the season and the sun, not just the map. In season and unheated beats local and heated.
• Treat distance as a tiebreaker, not the headline. Between two similar in-season plant foods, closer is marginally better — but it is a rounding error next to the meat-versus-plants choice.

Where the honest answer is “it’s complicated”

We are not going to tell you the sustainable plate is the easy plate. Two caveats matter, and pretending otherwise would be exactly the kind of overclaiming this exists to avoid.

It has to be affordable to count. The EAT–Lancet Commission’s 2025 modelling6 found the “planetary health” diet out of financial reach for an estimated 2.1 billion people, and its limits on animal foods may be too strict for nutrient adequacy in some low-income contexts. A greener diet that only the affluent can afford is a smaller achievement than it looks.

And “green” is not the same as “healthy.” The footprint question and the nutrition question overlap, but they are not identical — a diet can be low-carbon and still short on iron, or protein, or B12. We will treat those as the separate problems they are.

The greenest plate isn’t the one with the most virtuous story attached. It’s the one the lifecycle numbers actually support — which usually means less red meat and more in-season plants, and only rarely means what “local” made you feel. Where the data is genuinely mixed, we’ve said so, because on this topic the honesty is the point.