Speaker
Description
Food systems are at the core of numerous negative impacts, involving e.g. greenhouse gas emissions, biodiversity or human health. To address part of these problems, there were multiple calls to reduce or even suppress animal products in human diets (Tilman and Clark, 2014). However there is still no consensus regarding the extent of reduction of these animal source foods to mitigate the environmental impacts of food systems (Frehner et al., 2020). In addition, climate change poses an enormous threat on crops and livestock, while at the same time, agricultural systems constitute key levers to mitigate climate change. In this context, process-based models are essential to investigate the potential outcomes of prospective scenarios such as keeping highly specialized agricultural systems or suppressing livestock. Such studies are still very rare, most of comparisons in agricultural circularity using mass-flow models which do not allow to investigate climate change scenarios and perform granular analyses of carbon and nitrogen cycles.
In this work, we wanted to study the impacts of contrasting livestock integration on cropping systems sustainability (productivity, soil organic carbon, resistance to extreme climatic events). In that objective, we compared three different 8-year crop rotations contrasting by their level of livestock integration and by the commodities they supply for human diets. Each was simulated with the soil-crop model STICS (Brisson et al., 2009) over a 24-year period of time in Belgian pedoclimatic conditions, in five different climate scenarios: 1980-2010, 2040-2070 (RCP4.5 and RCP8.5), and 2070-2100 (RCP4.5 and RCP8.5). The first one is Business-as-usual with common cash crops of Belgium and in which manure is imported from other livestock farms in exchange of exported straw. The second system is called Vegan, and simulates an agriculture where livestock would be banned. It therefore does not use manure, but all crop residues are incorporated into the soil after harvest. The third system is qualified as Integrated crop-livestock (ICLS). It uses sheep as functional tools to manage weeds and pests through grazing of temporary pastures, which last 2.5 years over the 8-year rotation.
Simulated yield evolutions with climate change varied between crops, ranging from losses (up to -49%) to gains (up to 51%). It appeared that global yield shifts due e.g. to CO2 fertilization effect and higher crop stresses are modulated by the impacts and occurrence of extreme climatic events. The resistance to these extreme climatic conditions is influenced by the contrasting livestock integrations, even when comparing similar crops that are common to the different circularity scenarios. For example, the loss of soil organic carbon in the Vegan system provokes greater stomatic water stresses and lower crop resistance. In the contrary, closely connecting crops with livestock through the integration of temporary grazed grasslands into the rotation increases soil organic carbon, and hence improves soil capacity to retain water.
Finally, this study aims at illustrating how soil-crop models might be coupled with external methodologies to explore the outcomes of potential agricultural circularity scenarios for food systems under historical and future climatic conditions. We believe that extending such comparisons to various agro-pedoclimatic conditions would allow to better understand the impacts of food policies on the climate change adaptation and mitigation capacities of agricultural systems.
References:
Brisson, N., Launay, M., Mary, B., Beaudoin, N. (2009). Conceptual basis, formalizations and parameterization of the STICS crop model. Ed. Quae. 297
Frehner, A., Muller, A., Schader, C., De Boer, I. J. M., & Van Zanten, H. H. (2020). Methodological choices drive differences in environmentally-friendly dietary solutions. Global Food Security, 24, 100333.
Tilman, D., & Clark, M. (2014). Global diets link environmental sustainability and human health. Nature, 515(7528), 518-522.
| Keywords | Climate change; Resistance; Soil organic carbon; Soil-crop model; Circularity |
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