The ins and outs of organic farming.

IN THEIR REPORT “SOIL FERTILITY AND BIOdiversity in organic farming,” P. Mäder et al. (31 May, p. 1694) downplay two factors in their discussion of the relative merits of organic and conventional farming. First, because organic farming yields (per unit of land) were 20% lower than those from conventional farming, 25% more land would be required to produce the same amount of crop biomass, offsetting some of organic farming’s advantage with respect to biological diversity, inputs, and soil erosion. Allowing for an increase in cultivated land and adopting the authors’ results (p. 1695), organic farming would reduce overall nutrient use by 18 to 39% (not 34 to 51%), energy use by 20 to 41% (not 20 to 56%, as indicated in the text), and pesticide use by 96%. So in terms of the environment, the issue is whether reducing nutrient, energy, and pesticide inputs and impacts on biodiversity on a smaller piece of land outweighs the impacts of increasing cropland under cultivation (1, 2). The answer to this question might be different if one examines what occurs “typically.” If typical cereal yields under organic farming are 60 to 70% of those of conventional farming (p. 1695), then between 43 and 67% more land would be needed to keep production constant, further diminishing the environmental and biodiversity advantages of organic farming. Similarly, organic farming might require 0 to 43% more grasslands. Second, although Europeans—being well fed and currently running unsustainably large food surpluses—might welcome reduced crop production, it could prove disastrous for those in developing countries. A 20% reduction in production from 1997–99 levels, for instance, would reduce global crop production per capita to levels not seen since at least the early 1960s (3). Despite improvements during the 1960s, an estimated 37% of the inhabitants of developing countries (or 956 million people) still suffered from chronic hunger and malnourishment in 1969–71 (4). By 1997–99, thanks in large part to conventional agriculture, these numbers had dropped to 17% (or 777 million). Therefore, a 20% drop in production would have more than doubled their numbers to at least 1700 million in 1997–99. Clearly, there are environmental and humanitarian trade-offs that should be considered before judging the overall merits of different agricultural systems. Curiously, the authors did not discuss the difference in yields between experimental and “typical” conditions, which, according to them was 10% compared to 30 to 40% (p. 1695, paragraphs 3 and 4), particularly be-