The environmental footprint of organic vs. conventional food

For most people willing to pay a premium for organic food, the reason is some nebulous combination of health, environment and flavor. If pressed, however, few could point to evidence that organic food is better than conventionally grown products on any of those counts.

This month, a new piece of evidence emerged on this issue, and the news was bad for organic agriculture. A report out of Stanford University found no consistent differences in nutritional content between organic and conventionally grown crops. So how about the other reasons for buying organic? Let’s start by looking at the environmental differences between conventional and organic farming.

Comparing the environmental impacts of two products involves many considerations: chemical runoff into our water supply, soil health and greenhouse gas emissions, to name just a few. Since there isn’t enough space to consider all of those in a single article, we’ll take one environmental consideration at a time in an occasional series.

Land use is a reasonable place to begin. Part of a product’s environmental impact is the amount of space required to produce it. After all, if a plot of land weren’t required to produce corn or avocados or pigs, it could be used for environmentally helpful purposes such as habitats for wild animals or carbon-eating plants or land for solar panels and wind farms.

Food production requires an incredible amount of land. By some estimates, croplands and pastures now occupy 40 percent of Earth’s land surface. Producing more food with less land could be a major win for the environment.

In May, researchers at Canada’s McGill University and the University of Minnesota published an article in the journal Nature comparing the productivity of organic and conventional farms.

This particular study is known as a meta-analysis. In a meta-analysis, a researcher compiles all of the studies on a particular issue, usually discarding those that are methodologically unsound, then finds a statistical method with which to combine them. Ultimately, a meta-analysis turns a series of smaller studies into a large study, which, if done right, carries more persuasive heft and can bring real clarity to disputed scientific issues.

In their meta-analysis, McGill’s Verena Seufert and her colleagues examined 66 previous studies. Their results are bound to disappoint organic advocates. Overall, they found that organic methods produce 25 percent less food than conventional farming on the same land area.

That headline number, however, tells only part of the story, and the details can help guide your decisions as a consumer.

For some crops, organic methods are nearly as productive as conventional farming. Organic fruit farms, for example, finished in a statistical dead heat with conventional acreage. The yield of organically grown tomatoes (considered separately from other fruits) was statistically indistinguishable from conventional tomatoes as well, as were organic oilseeds such as sunflower and canola. Organic legumes, such as peas and beans, also performed well.