Q: Can the choices you make at the grocery store truly impact the environment?

Asked by Monica Jain, ’85, Carmel, Calif.

With all the environmental problems the world faces, it’s easy to be overwhelmed and discouraged—and to wonder whether small actions can really make a big difference. But the short answer is: Yes, absolutely. Growing, shipping, storing and preparing food accounts for up to 30 percent of our greenhouse gas emissions, for example. And then there’s all the water used for irrigation, and the chemical fertilizers and pesticides used to make crops grow, and all the packaging used to make your food look presentable. Agriculture has a huge impact on the environment, and because the choices you make in the supermarket tell managers what to stock and farmers what to grow, you can have an important impact on agriculture.

So what are these choices, and how can you start greening your grocery list? It can seem awfully confusing at first, especially given the prevalence of “greenwashing,” a phenomenon in which companies advertise less-than-stellar products as “sustainable” or “eco-friendly”. Some labels, such as “organic,” involve third-party certification; others, including “natural,” can be slapped onto just about anything, without any data to back up the claim. Many of these terms are decoded online: Consumer Reports is one website with a great database of common labels and what they really mean.

Still, who wants to consult a database before they go grocery shopping, let alone try to work out the carbon footprint of a box of cereal while standing in the breakfast aisle? One day the food we buy may come with carbon emissions labels, just like the nutrition labels we have now. But until then, here are some general guidelines to help ease your shopping experience:

Buy local, seasonal produce. Sure, this is easier in California than in some other parts of the country, but the average food item in the United States is shipped 1,500 miles to its final destination. That means huge energy costs in transportation, and in cold storage. Local foods are also fresher than those shipped from far away.

Buy organic when you can. Organic food comes free of harmful chemicals like pesticides and slows the dangerous flood of fertilizers into our waterways. With organic, you don’t have to worry about mysterious residues on your food. When the choice is between organic and local, just remember that either is better than none, and both are best!

Cut down on meat. Livestock alone accounts for 18 percent of our global greenhouse gas emissions, and intensive feedlots turn once-beneficial manure into noxious waste lagoons. The growing global appetite for beef also is a big contributor to Amazon deforestation. Try going without meat one day each week, or switch from environmentally damaging meats like beef to more eco-friendly fare like chicken.

Minimize food packaging and processing. Frozen organic veggies may be good for you, but they are way worse for the environment than the fresh equivalent. Packaging, meanwhile, just ends up in the landfill, so think about bulk purchases, or products with recyclable packaging.

My favorite way to meet practically all of these guidelines at once: a visit to the local farmer’s market. Plus when you support the little guy, you not only get tastier, more ripe and often cheaper food, you also get to meet the person who grew it. Even better, farmer’s markets are overflowing with delicious free samples!

Our food system won’t become truly sustainable without some major changes in the way our food is produced and distributed. There are many organizations and lobbying groups pushing for deeper systemic change. You can get involved in the debate directly, and you can get your friends on the sustainable food bandwagon too; the more voices, the greater the impact will be. In the meantime, you can enjoy your eco-friendly dinners with a clean conscience.

Heather Benz plans to receive her bachelor’s degree in earth systems in 2010.