What’s the connection between food and global warming? Author Michael Pollan and sustainable food advocate Anna Lappé suggest ways to reduce the carbon footprint of our food.

Why should people care about the relationship between food and climate change?

Michael Pollan: The carbon footprint of our food choices is important. When we think about global warming, we usually think about transportation and how we heat our houses. But how we eat has just as big an impact on climate change. Twenty percent of greenhouse gases can be traced to agriculture and to the food system, in general.

Anna Lappé: The relationship between food, transportation, and energy is huge. Large amounts of energy are expended globally to transport food, much of it illogically. A frozen chicken from the United States gets shipped to China to be processed into chicken nuggets then shipped back to the United States. That chicken has traveled more in its lifetime than most people on the planet ever do.

What are food miles?

Michael Pollan: The concept of “food miles” is an attempt to quantify the amount of energy that goes into our food. The average food item in America has traveled 1,500 miles from the farm to your plate. It has burned up an incredible amount of fossil fuel just to get there. If you’re in New York and you buy a bag of pre-washed, mixed lettuce that’s been grown in California’s Salinas Valley, it takes 56 calories of fossil fuel energy to deliver 1 calorie of food energy to your plate. That is a very unsustainable way to eat, even if the lettuce is organic.

The mode of transportation makes a difference, too. Foods that travel by ship–even if they travel further than food that has traveled by diesel truck–may have a lower carbon footprint. In counting food miles, you have to look at the whole picture.

How can people reduce their carbon footprint through their food choices?

Michael Pollan: One thing you can do is eat locally, so that your food doesn’t travel as far. Plus, there are other great benefits to eating locally besides conserving energy, such as keeping farmers in business in your community.

To understand how much energy goes into your food, all you have to understand is: If the food is local and unprocessed, it’s usually using less energy. A lot of energy goes into processing food. All the complicated steps needed to make a Twinkie a Twinkie use vast amounts of energy. If you’re eating whole foods, there’s generally a lot less energy going into making it. Eat closer to home, and eat less processed food, and you will cut down on your carbon footprint.

More: Agriculture, Anna Lappé, Changing the Menu, Environmental Issues, Farm to Fork, Global Community, Local Food, Michael Pollan, Shopping Wisely