Some organic farming practices, like crop rotation and the use of cover crops , additional plants that can help control erosion and pests, help keep nitrous oxide emissions in check. That’s because they promote healthy soil, and healthy soil releases less nitrous oxide.

Other practices, though, like tilling the soil to get rid of weeds (instead of spraying chemicals), have the opposite effect. Tilling encourages nitrous oxide emissions. Moreover, because it typically produces less food per acre, organic farming tends to need more land, workers and organic fertilizer to stay competitive. That larger scale means larger greenhouse gas emissions.

“There’s pretty good peer-reviewed science arguing that the carbon footprint would actually expand if we were to see a widespread shift to organic, versus having the productivity benefits of conventional production,” said Michael Doane, the global managing director for sustainable food and water at The Nature Conservancy.

Julius McGee, an assistant professor of sociology at Portland State University, said that organic farming had a high carbon footprint because it’s been co-opted by industrial growers that supply big-box stores.

“Large organic retailers rely on cheap organic foods and, in order to produce organics cheaply, you oftentimes operate under the same model as industrial agriculture where you try to reduce costs, and for that you need more inputs , which contributes to more greenhouse gas emissions,” Dr. McGee said.