Comparisons between organic and conventional agriculture need to be better, say researchers
The environmental impact of agriculture and food production is a highly topical issue and frequently discussed worldwide. However, researchers from Aarhus University, Chalmers University of Technology and INRAE point out that the comparison method most widely applied (LCA) often lacks some rather crucial factors. Often, the LCA method does not include factors such as biodiversity, soil quality and pesticide impacts, factors of major importance in relation to agricultural impact on the environment. In a scientific paper in the journal Nature Sustainability, the researchers describe – based on an exhaustive analysis – their concern that the current application of the method may result in incorrect conclusions concerning comparisons of intensive specialized farming and agroecological agriculture (such as organic farming).
The method most widely used to assess environmental impacts from agriculture and food production is life cycle assessments (LCA). A few of the studies that have used this method conclude that organic farming is worse for the climate because it often has lower yields and therefore might use more land to make up for this.
According to three researchers from Denmark, Sweden and France, this comparison of organic and conventional farming is inadequate for the following reasons: 1) a narrow perspective on functions in agricultural systems; 2) a lack of impact on biodiversity, soil and pesticides; and 3) inconsistent modelling of indirect effects outside the production system. The researchers present this in an analysis of many different life cycle assessments in the scientific journal Nature Sustainability.
”We are worried that the use of LCA in its current form is too narrow and misrepresentative as to such a comparison, and that we therefore end up making poor decisions politically and socially. When comparing agroecological agriculture (such as organic) with conventional agriculture, there are wider effects that the current approach does not adequately consider”, says Hayo van der Werf, INRAE – French National Research Institute for Agriculture, Food and Environment.
Biodiversity, soil quality and pesticide impact
Biodiversity is of vital importance to the health and resilience of ecosystems. However, it is declining worldwide, and intensive agriculture has been shown to be one of the main drivers of negative trends such as insect and bird decline. Recently, more than 65 researchers called for action – in an open letter in the scientific journal Nature Ecology & Evolution – in order to prevent this decline in insects due to e.g. agricultural intensification.
Agriculture occupies more than one-third of global land area (in Denmark more than 60%), so any links between biodiversity losses and agriculture are hugely important.
”Our analyses show that the current life cycle assessments rarely consider the impact on biodiversity, and that they thus miss one of the obvious advantages of agroecological farming”, Marie Trydeman Knudsen, Department of Agroecology at Aarhus University, explains. She further adds: “A meta-analysis of many field observations has shown that organic agriculture supports biodiversity levels, measured as species richness, that are approximately 30% higher than those of conventional agriculture.”
According to the researchers, pesticide use is another factor, which is often lacking in current LCAs. From 1990 to 2015, pesticide use increased by 73% worldwide. Residues of certain pesticides in soil, water and food may affect human health as well as terrestrial and aquatic ecosystems, and it is a major driver of biodiversity loss.
Organic agriculture prohibits the use of synthetic pesticides, but according to the researchers’ analysis, only few LCAs include pesticide use when comparing the environmental impact of organic and conventional farming.
According to the international group of researchers, factors such as land degradation and soil quality are rarely included in LCAs. Thus, cultivation practices that increase soil carbon sequestration and soil quality are often ignored in LCAs, according to the analysis from the researchers.
”Another crucial factor is the fact that LCA generally assesses environmental impact per kg of product. This measuring method favors intensive cultivation systems that may have a lower impact per kg, but higher impact per ha. The method does not cover the entire agroecological system. A diversified landscape with smaller agricultural fields, more hedgerows and a variety of crops, which provides other benefits – greater biodiversity, for example ”, says Christel Cederberg, Chalmers University of Technology.
According to the three researchers, the current use of LCA and its product-based approach does not capture the complexity of agroecological cultivation systems, an example of which is organic farming. There is a need for a more fine-grained LCA approach, says Christel Cederberg.
A varied picture
According to the researchers from Denmark, Sweden and France, an additional weakness in the current use of LCA occurs when hypothetical “indirect effects” are included in the calculations. An example of this is the hypothesis that a reduced yield in organic farming will automatically mean increased GHG emissions due to the need for more farmland, which in turn may result in deforestation. According to the researchers, the assessment of such indirect effects is problematic and simplified, as other indirect effects in organic farming, which may lead to lower greenhouse gas emissions and land use, is not included.
”Taking meat as an example, it is assumed that the meat consumption will remain the same – when the demand for organic foods increases – and that there is a need for more farmland. However, studies indicate that consumers buying organic food – for environmental or ethical reasons – are likely to purchase fewer animal-based products – which reduces the need for more farmland. Only a few studies of such consumer behavior exist, making it difficult to explain this type of social shift”, says Hayo van der Werf.
Life cycle assessment is a strong and useful tool to assess environmental and climate impact in relation to e.g. food production. However, there is a need to develop the method in order for it to take into account some of the sustainability aspects mentioned, says Marie Trydeman Knudsen.
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Further information
Researcher Marie Trydeman Knudsen, Department of Agroecology, Aarhus University. E-mail: mariet.knudsen@agro.au.dk Telefon: +45 87 15 7958
Researcher Hayo Van der Werf, French National Research Institute for Agriculture, Food and Environment (INRAE). E-mail: hayo.van-der-werf@inrae.fr Telefon: +33 2 23 48 57 09
Professor Christel Cederberg, Department of Space, Earth and Environment, Chalmers University of Technology. E-mail: christel.cederberg@chalmers.se Telefon: +46 31 772 22 18