Because eating is basically a reflex, we never really stop and think about where our food comes from, or how many miles it has traveled before ending up on our plates. I recently read in an article that the average meal will travel 1500 km before being consumed. When considering that there are over 310 million people in the US (not to mention the rest of the world), and that we'll each eat an average of 3 meals a day, it's obvious that the kilometers add up fast. Buying local produce and growing your own food can help to reduce the amount of precious fossil fuels used in transportation, and therefore decrease CO2 emissions.
Because my grandfather raises chickens and my mother has a garden chock full of fruits and veggies almost all year round, I consider myself to be something of a localvore, or person who eats locally. I know that not everyone has the time or space to maintain their own gardens, but you can start small. Growing a tomato plant in a pot on your windowsill, and later using it to make a delicious tomato sauce will make the distance from farm to table just  a few feet! Just like that you can drastically reduce your carbon footprint, and be well on your way to becoming a localvore.