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KEYNOTE SESSION 8 th Int. Conference on LCA in the
Agri-Food Sector, 1-4 Oct 2012
The yield performance of organic agriculture
Verena Seufert 1,* , Navin Ramankutty 1 , Jonathan A. Foley 2
1 Department of Geography and Global Environmental and Climate Change Center, McGill University, Quebec H2T 3A3, Canada
2 Institute on the Environment (IonE), University of Minnesota, 1954 Buford Aevnue, St. Paul, Minnesota 55108, USA
Corresponding author. E-mail: verena.seufert@mail.mcgill.ca
ABSTRACT
Organic agriculture is often proposed as a solution to the challenge of producing sufficient food in a sustainable way. However,
organic agriculture is also critizised for its purported lower productivity compared to conventional agriculture. Here we use a comprehensive
meta-analysis to examine the relative yield performance of organic and conventional farming systems globally. Our
analysis of available data shows that, overall, organic yields are typically lower than conventional. The yield difference varies, however,
depending on site and system characteristics. Under certain conditions – i.e., with good management practices, particular crop
types and growing conditions – organic systems can nearly match conventional yields, while under others it currently cannot. 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.
Keywords: organic agriculture, yields, meta-analysis, sustainability
1. Introduction
Agriculture is a major source of global environmental degradation (Foley et al., 2005). Numerous recent
reports have emphasized the need for drastic changes in the food system in order to meet the double challenge
of feeding a growing population with a rising demand for high-quality diets while minimizing the environmental
impacts of food production (Foley et al., 2011). ‘Alternative’ management practices that try to
mimic ecological processes while minimizing external inputs are often suggested as important tools in the
solution to this problem (Schutter 2010). Organic agriculture, which currently covers 0.9% of global agricultural
land (Willer and Kilcher 2011), is the most prominent of these alternative farming systems. It is a farming
system aimed at producing food with minimal harm to ecosystems, animals or humans.
Driven by consumer concerns about food safety and environmental issues the market for organic products
has grown rapidly and more than tripled in the last decade (Willer and Kilcher 2011). Notwithstanding its
increasing popularity amongst consumers, organic agriculture has many ardent opponents (Trewavas 2001).
One of the main objections against it is its purported lower productivity – critiques argue that organic agriculture
would need considerable more land to produce the same amount of food, resulting in more widespread
deforestation and biodiversity loss.
A recent study attempted to address this criticism by analysing data from the literature on 293 organic-toconventional
yield comparisons (Badgley et al., 2007). They concluded that organic agriculture could, overall,
provide sufficient food to feed the current population for the same amount of land used. This conclusion
was, however, highly contested by several critiques who claimed that serious methodological flaws had led
to an overestimation of organic yields (Avery 2007; Connor 2008).
2. Methods
Here we have performed a comprehensive synthesis of the current scientific literature on organic-toconventional
yield comparisons using formal meta-analysis techniques. We compiled our own dataset of
scientific studies comparing organic and conventional yields. To address the criticisms of the Badgley et al.,
(2007) study we used several selection criteria: (1) we restricted our analysis to studies on “truly” organic
systems, defined as those with certified organic management or non-certified organic management, following
the standards of organic certification bodies; (2) only included studies with comparable spatial and temporal
scales for both organic and conventional systems; and (3) only included studies reporting (or we could
estimate) sample size and error. Conventional systems were either high- or low-input commercial systems, or
subsistence agriculture. 66 studies met these criteria, representing 62 study sites, and reporting 316 organicto-conventional
yield comparisons on 34 different crop species.
We used the natural logarithm of the response ratio, which is the ratio between organic and conventional
yields, as effect size and calculated a weighted average by weighting each observation by the inverse of the
mixed-model variance (Hedges et al., 1999). An effect size is considered significant if its confidence interval
(CI) does not overlap one in the backtransformed response ratio. In addition to yields, we collected information
on study characteristics like crop rotations, fertiliser type and experimental study design as well as information
on the biophysical characteristics of the study site, and analysed their influence as well. To test for
the influence of categorical variables on yield effect sizes we examined the between-group heterogeneity
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