PhD Defence

Noélie Borghino will defend her PhD in front of the following jury:

• Pierre Gerber (Université de Wageningen, Banque Mondiale), referee
• Patrick Meyfroidt (Université catholique de Louvain), referee
• Souhil Harchaoui (INRAE), examinator
• Marie-Hélène Jeuffroy (AgroParisTech, INRAE), examinator
• Elin Röös (Swedish University of Agricultural Sciences), examinator
• Chantal Le Mouël (INRAE), supervisor
• Thomas Nesme (INRAE), supervisor

Abstract

Future climate related risks depend on our ability to curb greenhouse gas (GHG) emissions, which require a profound food system change. Organic farming and dietary shifts towards more plant-based diets are often seen as promising ways to mitigate GHG emissions. They are both promoted by the European Union (EU), which aims for climate neutrality by 2050. However, the expansion of organic farming is controversial, as it could lead to land-use changes – and associated CO2 emissions – to compensate for lower productivity. Therefore, the EU’s goal of dedicating 25% of its agricultural land to organic farming by 2030 has been criticized, particularly because the globalization of agricultural trade could lead to emissions being shifted to other regions. Furthermore, the interactions between dietary changes and the development of organic farming have not been sufficiently explored. A reduction in livestock, driven by a lower demand for animal products, might relax agricultural land demand for producing feed and compensate for higher land requirements of organic systems. However, the reduced availability of manure could negatively affect nitrogen (N) inputs to organic crops and challenge organic systems productivity. This could undermine the GHG mitigation potential of both strategies, especially in the case of a drastic reduction in animal product consumption, as in vegan diets. Therefore, the aim of this thesis is to assess the combined effects of these two levers in Europe on land use and GHG emissions, considering the effects related to the N cycle. We first reviewed studies that explored the effects of organic farming expansion using a modeling approach. We showed that considering N availability feedback on crops yields exacerbates the anticipated drop in agricultural production. Next, we used the GlobAgri model, which computes cropland and permanent grassland requirements at the scale of large global regions in 2050, to simulate the adoption of vegan diets in Europe, with or without maintaining livestock production for export. Our results show that the impacts on croplands N balance depend on the relative adjustment of two compensatory factors: the decrease in manure availability, and the decrease in the land required for producing feed. Finally, we simulated scenarios combining dietary changes and widespread adoption of organic practices by coupling two models: i) GOANIM, which simulates N balances of organic croplands, yields, and animal densities, and ii) an adapted version of GlobAgri. We found that a higher share of organically managed croplands would lead to an increase in European cropland requirements, due to lower crop yields and changes in crop rotations. This increase would allow Europe to maintain its export shares, preventing emissions to increases in the rest of the world. In a scenario without dietary changes, 25% organic croplands would increase the domestic GHG balance by 10%. In scenarios combining more plant-based diets with more disruptive organic practices, emissions from land-use changes would be offset by reduced land requirements and emissions from agriculture, up to 50% organic croplands. Beyond that, the land demand to maintain export shares would be too high. Overall, our work contributes to include complex interactions between crops, livestock, N cycle, global trade, and GHG emissions in large-scale models. It provides suggestions for effectively combining the expansion of organic farming with dietary shifts towards more plant-based diets.