Buying local is treated as self-evidently correct. Short distances, less transport, fewer emissions. The logic looks compelling.

The data is more complicated, and in several cases intuition leads to the wrong answer. That doesn't mean local is bad — only that the justification should usually be a different one.

Transport is rarely the big item

Life-cycle assessments of food consistently find that transport accounts for a smaller share of total emissions than public debate suggests. The far larger portion arises in production itself — feed, fertiliser, land use, on-farm energy.

The reason is efficiency through volume. A container ship moves enormous quantities with comparatively little energy per kilogram. Even a fully loaded lorry over a thousand kilometres is more efficient per kilo than many short journeys with small loads.

This produces a counterintuitive result: the last few kilometres are often the least efficient. Driving twenty kilometres to a farm shop and buying three kilos can generate more emissions per kilogram than the entire preceding transport chain.

Where transport does decide it

One important exception, and it's a large one: air freight.

The emissions difference between ship and aircraft is enormous — orders of magnitude depending on how it's calculated. Anything flown therefore carries a substantially worse footprint.

Affected are mainly highly perishable products that must reach the customer quickly: certain berries out of season, fresh beans from overseas, some exotic fruit, fresh fish from distant regions.

The problem is that you usually can't tell by looking. A rough rule: if it spoils fast and comes from a distant country, it was probably flown. If it keeps well — bananas, citrus, nuts, coffee — it almost always came by sea.

Seasonal beats local

The most instructive finding in this area concerns greenhouses.

Tomatoes from a heated greenhouse in northern Europe in winter have, according to several studies, a worse footprint than field tomatoes from southern Europe trucked north. Heating energy clearly exceeds transport.

The same applies to strawberries, peppers and other crops produced under glass out of season.

Local plus out of season is therefore often the worse choice. Seasonality is the stronger lever.

The picture shifts where greenhouses run on waste heat or renewable energy, which is increasingly common. Blanket statements don't survive long here.

Storage counts too

A factor almost nobody includes. Local apples in May come out of controlled-atmosphere storage where they've sat for months. That consumes energy continuously.

With long storage, freshly harvested fruit from another climate zone can come out ahead. The calculation depends heavily on storage duration and energy source.

What makes the biggest difference

Taking the research together, a fairly clear ranking of levers emerges.

First: the product category. The difference between animal and plant foods is many times larger than any difference in origin or transport. Ruminants sit well above other animal products again.

Second: food waste. A substantial share of food produced is never eaten, and much of that occurs in private households. A discarded product has generated all of its emissions and delivered no benefit at all.

Third: seasonality and growing method. Field rather than heated greenhouse.

Fourth: transport mode. Avoid air freight.

Fifth, and by some distance the smallest: distance.

Buy local anyway

One category deserves separate mention because it is where intuition fails hardest: greenhouse-grown produce shipped from warm regions versus locally grown under glass.

Southern European field production in winter, trucked north, generally outperforms northern greenhouse production heated through the cold months. The transport is real and the heating is larger.

But the calculation flips again for water. Several major growing regions supplying northern Europe in winter are water-stressed, and irrigation there draws on aquifers under pressure. Emissions are not the only environmental dimension, and a product with a good carbon footprint can carry a poor water footprint.

There is no single number that captures all of this, which is genuinely frustrating for anyone trying to shop responsibly. My honest position is that the differences between individual products within a category are usually smaller than the differences between categories, and that anyone who has already adjusted what they eat and how much they waste has done most of what is available to them.

I don't want this read as an argument against buying locally, because there are good reasons for it — they're just different reasons.

Local value creation stays in the region. Smaller farms survive, which matters for landscape and diversity. You're more likely to know how something was produced. And the products are often fresher and taste better, because they can be harvested ripe.

Those are economic, cultural and culinary arguments, and they're entirely legitimate. They just aren't primarily climate arguments, and selling them as such makes them vulnerable.

My practical conclusion: buy seasonally, waste little, keep an eye on the share of animal products, avoid flown goods — and then happily from the producer round the corner, because that's a good idea for other reasons.