You’re ‘green’—you recycle, take cooler and shorter showers, turn off lights, turn down thermostats, drive less, fly less, buy less stuff. But have you considered the profound impact that your dietary choices have on the environment? Few things we do on this planet affect the environment more than the way we produce our food. Recent estimates suggest that, globally, food production is responsible for nearly ⅓ of all greenhouse gas emissions—more than any other sector, including transportation. There are several things you can do to adopt a greener diet and lessen your impact on the earth:

Go vegetarian or vegan. A 2006 United Nations report estimated that livestock are responsible for a staggering 18 percent of greenhouse gas emissions. Even if you commit to eating vegetarian only one day a week (visit meatlessmonday.com for help), this can do more to reduce your environmental impact than driving a hybrid vehicle or switching to an entirely local diet. Reducing dairy and meat consumption is crucial because ruminants (cows, sheep and goats) naturally emit methane, a greenhouse gas that is 23 times more potent than carbon dioxide.

Avoid products from factory farms. Water, air and soil pollution is an inevitable result of the approximately three trillion pounds of excrement produced annually by these industrial-scale production systems. This manure is often contaminated with disease-causing organisms like Salmonella and E. coli, residual amounts of hormones, antibiotics, pesticides, and toxic heavy metals like cadmium, lead, and arsenic. Factory farming raises additional concerns about the development of antibiotic resistant organisms, food-borne illness, the emergence of novel pathogens like avian and swine influenza, and the welfare of the workers and animals involved.

Reduce or eliminate seafood consumption. Fishing vessels use large amounts of energy, as does the air transportation and refrigeration of seafood. Furthermore, many aquatic species are over-fished, and ocean habitats are on the verge of collapse. Fish farms pollute waters with concentrated amounts of feces, chemicals and antibiotics. If you choose to eat seafood, consult the Monterrey Bay Aquariam’s guide to sustainable seafood at seafoodwatch.org.

Buy regional foods in season, and choose organic. Local foods tend to result in the production of fewer greenhouse gases than foods that must be transported over long distances. But be sure to buy food in season—foods grown in local hothouses often require more energy than foods that must be shipped. Organic farming methods are generally more sustainable and don’t rely on synthetic pesticides, herbicides, and fertilizers derived from non-renewable resources. If you choose to eat meat, consider that most meat producers are not located near one of the country’s few USDA-certified slaughterhouses. Consequently, even ‘local’ livestock must be transported long distances before it reaches your plate.

Eat with consciousness. Know what you’re eating, where it came from, how it arrived at your table, and what it really cost to produce. Demand a more transparent food system from your legislators. And finally, share what you’ve learned with others, and inspire change in your friends and neighbors.