Many shades of gray – the context-dependent performance of organic agriculture
This review assesses the performance of organic cropping systems as an approach to sustainable agriculture, and seeks to identify the contextual considerations (such as type of cropping system) that may affect this performance. The scope of the review is constrained to the level of the farming system (i.e. excludes considerations of other components of the food system, such as packaging or transport). In order to provide an unbiased assessment of organic farming as a means of sustainable agriculture, rather than approaching the question from the usual “What does organic farming do well/badly?” angle, the authors ask “What constitutes successful sustainable agriculture?” then measure organic farming against this yardstick.
The authors assess the benefits and costs of organic farming in four main categories of impact: production (comprising yield and yield stability), the environment (biodiversity, soil quality, climate change mitigation, water quality and quantity), producers (farmer and farm worker livelihoods and health), and consumers (consumer health and access). The authors place an emphasis on assessing costs and benefits per unit of production output, rather than the more usual per unit area, arguing that production is the ultimate purpose of agriculture. Within each sub-category, the review writers consider not only the average performance of organic farming, but also the contextual factors that affect the range of this performance, such as cropping system type, which may result in organic farming performing better than conventional in some contexts but worse in others.
The key findings of the review are:
- Organic farms are usually lower yielding per unit area that their conventional counterparts, with an average yield gap of 19-25% (according to different meta-analyses). Contextual factors affecting this largely revolve around management practices and may result in a yield gap as low as 5% or as high as 40%.
- The performance of organic farming in terms of yield stability (i.e. dependability of yield over time) is mixed: factors favouring increased yield stability in organic systems compared to conventional include resilience conferred by higher soil organic matter and more diverse crop rotation; in contrast, factors leading to decreased yield stability in organic systems include a higher susceptibility to pest outbreaks, higher weed pressure and higher variability in nitrogen availability.
- Per unit area, organism abundance is 40-50% higher on organic farmland than conventional, with higher benefits to bees and plants than other groups, and higher benefits on simplified, highly agricultural land. However, there may be a trade-off between biodiversity and yields on organically managed farmland, with different landscape contexts favouring higher biodiversity per unit output (namely mixed and low-productivity landscapes)
- Soil on organic farms tends to have higher organic carbon content, possibly reduced soil erosion, and improved physical and nutrient qualities, with more abundant (but no more species-rich) soil fauna.
- Per unit area, direct and indirect GHG emissions (including N2O) are lower in most organic systems than conventional, while there is some evidence that CH4 emissions from organic rice paddies are higher than conventionally farmed ones. However, the performance of organic farming compared to conventional in terms of GHG emissions per unit output is less favourable, with N2O and CH4 emissions per unit output seemingly higher under organic management, and energy consumption being highly variable.
- Impacts on water quality: nitrogen leaching per unit area is generally lower in organic farming compared to conventional, but with high variation. However due to poorer nutrient use efficiency of organically applied nitrogen, nitrogen leaching to waterways is likely to be higher per unit output in organic systems. Depending on specific management systems applied, many organic systems are often either deficient in phosphorus or have a surplus (i.e. phosphorus sufficiency or excess is highly variable in organic systems). While organic pesticides tend to be less toxic at a specific dose than their synthetic equivalents, they are often applied more frequently and at higher dose so may have worse overall impacts, at a single farm or field level. However, the authors note that since most organic farms utilise alternative management practices instead of applying pesticides, the total impact on water quality of pesticide leaching is likely to be smaller from organic than from conventional agriculture.
- Improvements in soil structure due to organic management can result in improved water management per unit area but because yields are lower on organic farms it is not clear how organic farming performs in terms of water use per unit output. The authors urge further research into this question.
- For farmers, organic agriculture is often more profitable than conventional agriculture, as well as being less risky, due to a (usually) higher crop diversity. It is also often coupled with other livelihood benefits such as the formation of co-operatives, social networks, and (for the majority of organic farmers, who are in low income countries) access to services such as health care through their certifying and exporting agencies. While the nature of organic farming requires more, and more labour-intensive, farm labour, it is unclear how working conditions for farm workers differ between organic and conventional systems.
- For consumers, the health benefits of organic food are heavily debated, but organic foods may, on average, have higher nutrient contents than conventionally farmed foods, and certainly have lower pesticide residue contamination (however, as the authors point out, pesticide contamination on conventionally farmed crops is already well below acceptable levels in high income countries where the majority of organic food is consumed). Organic produce is generally more expensive for consumers than conventionally farmed produce and this does not appear likely to change.
The review considers the feasibility of scaling up organic farming (the review thus far focusses on organic farming at the single field or farm level), taking account, for example, of suggestions that organic farming relies heavily on outputs of conventional farming (e.g. manure from the livestock sector), and that a large-scale conversion of conventional to organic farms would likely result in decreased food production, but also reduced pollution of waterways.
The authors end by identifying remaining knowledge gaps and conclude that, while organic farming is not a total solution to many of the problems facing agricultural sustainability, and is challenged by many uncertainties, many benefits may be derived from incorporating certain elements of organic practice into conventional or other agricultural systems.
Organic agriculture is often proposed as a more sustainable alternative to current conventional agriculture. We assess the current understanding of the costs and benefits of organic agriculture across multiple production, environmental, producer, and consumer dimensions. Organic agriculture shows many potential benefits (including higher biodiversity and improved soil and water quality per unit area, enhanced profitability, and higher nutritional value) as well as many potential costs including lower yields and higher consumer prices. However, numerous important dimensions have high uncertainty, particularly the environmental performance when controlling for lower organic yields, but also yield stability, soil erosion, water use, and labor conditions. We identify conditions that influence the relative performance of organic systems, highlighting areas for increased research and policy support.
Seufert, V. & Ramankutty, N. (2017). Many shades of gray—The context-dependent performance of organic agriculture. Science Advances, 3.
Read the full paper here.
We also recommend that you read the FCRN publication Lean, green, mean, obscene…? What is efficiency? And is it sustainable? as it among other things considers how we think about the inputs to farm systems and about functional units- ie. the output we want and the impacts that arise.
While some of the food system challenges facing humanity are local, in an interconnected world, adopting a global perspective is essential. Many environmental issues, such as climate change, need supranational commitments and action to be addressed effectively. Due to ever increasing global trade flows, prices of commodities are connected through space; a drought in Romania may thus increase the price of wheat in Zimbabwe.
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