When measuring the productivity of farming, yield -- or output per acre of land -- is the metric that is often trotted out. And when this measure is used, organic farming usually falls short since it can’t match the yields of conventional agriculture. From there, it’s a short jump to conclude, as my friend Marc Gunther does, that organic methods will take more land to produce an equivalent amount of food, especially when population is increasing. The upshot, “organic food is not as green as you think.”

The problem with this argument is not that the yield calculations are wrong. The problem is that yield studies are inappropriate by themselves in measuring what’s “sustainable,” in determining what might “feed the world,” and which methods actually end up using more land in a particular situation. That’s because farming does not occur in a vacuum where yield is the sole measure of success.

Consider that the conventional farming methods that achieve higher yield require costly fossil fuel inputs in fertilizers and pesticides (the environmental impacts of which fall outside of yield studies), that they require highly mechanized tools that replace labor, and may rely on intensive irrigation from increasingly scarce water resources. Measured against the methods in most of the world -- 80% of the world’s workers are still farmers -- I have no doubt that the highly intensive model would produce a higher yield. But are those methods available or even appropriate to farmers in areas where food is most scarce and population growth the highest?

In some cases, those methods have proved disastrous, beause the technnology can’t be easily transposed from Iowa to Africa. One person who has looked closely at the issue, and who is also a conventional farmer in Illinois, the philantropist Howard Buffett, writes (pdf):

Commercial investment often focuses on increasing crop yields while governments emphasize expanded trade. The ultimate key to food security, however, is affordability and access to the proper food—neither approach has effectively addressed these issues in developing countries. The current situation mandates looking beyond crop productivity.

A narrow focus has dictated global agricultural policy over the past 30 years—it has failed, leaving millions hungry. Productivity in one part of the world cannot address land tenure, infrastructure, governance, investment protocol, culture, human capacity, research and development, gender disparity and a myriad other regional issues. Decisions and investments specific to individual countries—not the yields of another country half a world away—will always be the primary drivers of food security. (Emphasis added). 

As others have pointed out -- including the authors of the Nature study on which Gunther's post was based -- yield studies ignore two other imporant parameters: farmer livelihood and environmental impact, or the downstream effect of agriculture. If intensive agriculture pushes farmers off the land or leaves them indebted, what does that mean to livelihood? Of course, higher yields may produce more farm income -- except in situations where it does not.

I would add another consideration: that is, how appropriate and accessible are farming methods, especially when considering feeding the world. If the methods that produce the highest yield in Iowa are irrelevant in Zambia, does measuring relative yield even make sense? 

As just one small example, deforestation in Africa is a huge issue, since more land is cleared to plant crops. But as soil is depleted, fertilizers are used in ever larger amounts, contributing to even more intensive mining of the soil, loss of fertility and the burning of forests in the race for continued yields. In this situation, the question of which yield is higher, organic or conventional, is not even relevant. The question how can you achieve the highest yield without denuding the soil given methods that are accessible. Organic methods -- such as crop rotations, adding compost to the soil and even non-organic ones, such as judicious use of fertilizer -- might be best. But how does this fit into the what’s-the-highest-yield debate? It doesn’t, which shows the limitations of the question, even when considering the impact of farming on land use.

Indeed, this sole focus on yield takes on an almost religious ferver that drives attention from other issues that might raise yield far higher, such as addressing pre- and post-harvest food waste, which cuts productivity by up to 40%. Crack that nut and you will achieve more gains in efficiency and productivity than any improvement in farming could ever hope to offer -- and with technology that's currently available (think decent grain storage facilities, roads and transport). Yield by iself is too often relied upon as the sole yardstick to determine whether farming is "sustainable," will "feed the world," and is, in fact, green. To base decisions on that metric alone is myopic.