This is when you take into account not just ‘food miles’, but food production impact from ‘farm to fork’. In fact, even buying local can have a marginal impact when production methods are all factored in.
There’s no easy solution (is there ever?), but there is an easy thing you can do to be less of a big fat stupid planet hog:
“For the average American, buying local every day of the year would cut their carbon footprint by only around 4% or 400 kg of ‘equivalent C02 emissions’ (C02eq) per year. By comparison, shifting just one day a week from eating red meat and dairy to either chicken, fish, eggs or vegetables lowers your emissions by between 252kg and 400kg of C02eq.” (Italics mine)
From one good choice, many more can follow. Start now.