Organic farming – environmental benefit, yield cost?
August 27, 2013
While most consumers may choose organic foods for their potential health characteristics (e.g., lower chance of pesticide residue and potentially greater nutrient value), these same consumers generally believe that organic farming is “good” for the environment and thus worth supporting. But is the assumption of environmental benefit correct? And is there a cost? Let’s take a look at how the newer studies compare to older research findings.
Many studies of the environmental effects of “organic” versus “conventional” have been done, and organic often does show environmental benefits. In 2000, Stolze et al. attempted to synthesize the then-available data and knowledge on this question with regards to European countries. They surveyed specialists in 18 different countries as their primary source, and did an extensive literature review as a secondary source. They found organic systems generally increased soil organic matter and soil biology, but information on soil erosion was scarce. There were similar or lower levels of nitrate leaching with organic systems and no water quality contamination from synthetic pesticides since they were not used. Organic had lower emissions of CO2 per hectare, but higher emissions per unit of product due to generally lower yields on organic farms. The trend for N2O was similar based on limited data. Ammonia emissions were lower with organic systems. Organic systems typically had a nutrient balance near zero (inputs equaled outputs). Thus, organic systems did appear to provide environmental benefits, more so for some parameters than others.
Since that time, much more research has been done. A recent paper by Tuomisto et al. (2012) reports on their meta-analysis of published research regarding the environmental impacts of organic farming in Europe. Tuomisto and colleagues found that soil organic matter was an average of 7% greater on organic farms, mostly due to higher inputs (+65%) of organic materials, often manure. Nitrate leaching was 31% lower per unit area with organic, but 49% higher per unit of product. There were no significant differences between systems in field studies, while modeling studies predicted the greater leaching for organic, and may in fact be overestimating this. N2O emissions were 31% lower per unit area for organic and 8% higher per unit of product. Energy use averaged 21% less on organic farms per unit of product, with wide variation among products and studies.
The main conclusion of the 2012 paper was that organic farming generally has positive environmental impacts per unit of area relative to conventional systems, but not necessarily per unit of product, something Stolze et al. alluded to in 2000. On average, Tuomisto and colleagues found that organic crop yields were 75% of conventional yields looking at 13 crops. Variability ranged widely among crops. For potato, organic yields ranged from 11-132% of conventional, with a mean of 68%. For spring wheat, the range was only 70-87% of conventional, with a mean of 78%. So while environmental benefits are evident in organic systems, lower yields remain a factor to consider, especially when looking at land use. In this study, the lower yields and crop rotations that included non-harvested crops (e.g. green manures for nutrients) meant that organic farming would require 84% more land in Europe to produce the equivalent amount of harvest as conventional. Clearly, not a lot of new land is being made; is the tradeoff sustainable? Or perhaps the question is: how can yields be improved without compromising the environmental benefits of organic systems?
Increasing yields in organic systems would help address the contrasting findings between per area and per unit of product results, but the push to increase yields could also erode some of the benefits. Soil nutrient deficiencies were cited as a major cause of reduced yields, something that can be addressed through better use of the range of organic residuals available. The authors noted that in experiment station trials with high soil fertility, yields were more comparable between the two systems. Yields were also often reduced by inadequate control of weeds, insect pests, and diseases. Thus, there is clearly opportunity for research and education to help improve organic crop yields, which will lessen the environmental impact per unit of product and address the question of the increased land area needed for organic systems to produce the same food output as conventional. Yields do matter, and better data on yields from a large number of organic farms would help improve our understanding of this issue.
Stolze M., Piorr A., Härring A., Dabbert S. 2000. The environmental impacts of organic farming in Europe. Organic Farming in Europe: Economics and Policy; Volume 6. University of Hohenheim, Stuttgart, Germany. 143 pp. https://www.uni-hohenheim.de/i410a/ofeurope/organicfarmingineurope-vol6.pdf
Tuomisto H.L., Hodge I.D., Riordan P., Macdonald D.W. 2012. Does organic farming reduce environmental impacts? A meta-analysis of European research. J. Environmental Management 112:309-320.