There’s a burgeoning movement to eat local, at least among those who can afford it. Locavores buy their produce, meat, and dairy from farms within a small radius (there’s no consensus as to how small), or grow it themselves. The movement has a feel-good quality to it: it’s nice to meet your farmers and see the fields where your food gets raised, and fresher food usually does taste better. Best of all, transporting your food only a few miles must do wonders to reducing greenhouse emissions, right?

Actually, wrong. In this Freakonomics podcast, environmental studies professor David Cleveland explains the flaw in this reasoning. American food distribution is unbelievably efficient, allowing you to find ripe pineapples year-round at any supermarket across the country. When you look at all the greenhouse gas emissions related to producing the contents of your dinner, says Cleveland, transportation is responsible for less than 1%.

You might say, “well, every little bit helps,” but there are far more beneficial ways to give your eating habits a lighter impact on the Earth. Millions of people driving to farmstands to pick up locally grown food is highly inefficient. You’re better off living within walking distance of a grocery store, no matter where it sources the contents of its shelves. Food distribution is maximized when people dwell in close proximity with one another – that is, in cities. This is what I mean by “live local.”

(Incidentally, the best way to reduce your food footprint is to cut cow products from your diet. Raising cattle requires vast amounts of water – a huge problem for ranchers in the drought-stricken west. And cows produce lots of methane gas, which is more harmful than CO₂.)