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Organic food is not as "green" as you think

 To Hindus, cows are sacred. Jewish dietary laws (kashrut) and Muslim dietary laws (halal) prohibit pork consumption. Traditional Catholics abstain from eating meat on Fridays during Lent. Religion and food have forever been intertwined. Food is deep, emotional stuff.

So it's perhaps not surprising that devotees of organic food often embrace with quasi-religious fervor the practice of growing food without synthetic fertilizer or pesticides. [See, for example, my blogpost about Maria Rodale.] But if we want to understand impact of organic agriculture on the planet and on our health, science and not faith ought to guide us.

New scientific research points to a key drawback of organic agriculture, unfortunately: It is typically less efficient and productive than conventional growing methods. That's a problem for fans of organic because the world has a limited supply of farmland, a billion or so undernourished people, a growing population, an expanding middle class and therefore a vast appetite for affordable and nourishing food. If, in fact, organic methods are less productive, scaling up the production of organic food at will require more land, contribute to deforestation and cost more than growing our food using conventional methods. That suggests that organic methods alone can't feed the world in a sustainable way.

In a meta-analysis of 66 research studies  called "Comparing the yields of organic and conventional agriculture" published last month in Nature, Verena Seufert, Navin Ramankutty and Jonathan A. Foley write:

Overall, organic yields are typically lower than conventional yields.

They go on to say that the yield differences are highly contextual, depending on  crops and localities. The studies that they studied, it must be noted, use different methods and many are a decade or two old. This is by no means the last word on this issue. Still, they report that the yield differences

range from 5% lower organic yields (rain-fed legumes and perennials on weak acidic to weak-alkaline soils), 13% lower yields (when best organic practices are used), to 34% lower yields (when the conventional and organic systems are most comparable)

Of course, there are other reasons to embrace organic methods, which may be able to match or even outperform conventional farming methods under certain conditions. Organic methods reduce the use of agricultural chemicals that damage farm workers' health, for example. But, as the authors write, the yield issue should not be ignored:

To establish organic agriculture as an important tool in sustainable food production, the factors limiting organic yields need to be more fully understood, alongside assessments of the many social, environmental and economic benefits of organic farming systems.

Navin Ramankutty

To learn more, I called Navin Ramankutty, a geography professor at McGill University and an author of the study. Much of the debate that goes on about food today focuses on methods rather than outcomes, he told. That was obvious to me after he said it,  but I'd never thought about it that way. Organic farming is a method, or management system; it may well  generates less water pollution and fewer greenhouse gases than conventional agriculture, but organic certification doesn't measure those outcomes. Likewise, locavores, a group that includes not just the folks browsing the stands at a farmer's market, but also Walmart, which has promised to buy more locally-grown produce, are all about location, and the environmental benefits of localism, if any, are unclear. One reason why we don't look at outcomes, Navin said, is that "measuring those outcomes is extremely difficulty." Broad generalizations about agriculture don't tend to hold true because, like politics, all farming is local. Florida tomatoes have a different environmental profile from those grown in California.

Instead of wondering how and where an agricultural product was grown, we should be asking different questions, Navin suggested: "Is it good for the environment? Can it feed people? Is it good for the farmer?" To answer those last two questions–can it feed people and is it good for the farmer–you have to understand yields. Land is scarce and expensive, and if organic methods require more land (because they produce fewer calories per hectar), they will drive up food costs. That's troubling in a world where hunger is a bigger problem than obesity.

The Nature report has provoked a variety of responses. In an email to Andrew Revkin, who wrote about it at Dot Earth, author Jon Foley wrote:

The bottom line? Today's organic farming practices are probably best deployed in fruit and vegetable farms, where growing nutrition (not just bulk calories) is the primary goal. But for delivering sheer calories, especially in our staple crops of wheat, rice, maize, soybeans and so on, conventional farms have the advantage right now.

I asked Stave Savage, a scientist and industry consultant who blogs about agriculture at Applied Mythology, for his reaction. He looked at the underlying studies and told me that the evidence for the claim that organic can compete with conventional methods, even when it comes to growing fruits and vegetables, is skimpy. He told me by email:

The authors ultimately come out saying that some sort of hybrid would be a good idea.  On that I agree.  Organic was very ahead of its time in the early 20th century by focusing on building soil quality.  No-till and cover cropping achieve the same benefits without having to haul in massive amounts of compost or manure.

The problem is that many of the avid supporters of organic have no interest in anything like a hybrid or one learning from the other.  There is too much emphasis on philosophical purity and about demonizing regular agriculture rather than observing how much it has changed over time.

I agree, and I must say that  I wasn't surprised by what the Nature study found about yield.  To believe that organic agriculture is as productive or more productive than conventional, you have to believe that most American farmers don't know what they are doing–because the overwhelming majority cho0se not to grow organic. As I wrote last May:

Less than 1% of US farmland is farmed organically. If farmers could improve their yields by giving up chemicals and genetically modified seeds, why wouldn't they?

I'm planning to interview Laura Batcha of the Organic Trade Association this week, and I'll ask her that question. We'll also talk about the Farm Bill, the campaign to label genetically-modified foods and mad cow disease. I'll report back in a few days.