Résumé
Agriculture, forestry, aquaculture and fisheries face many challenges: growing food demand, persistent malnutrition and degradation of natural resources. Climate change makes it even more complex to ensure food security for 9.7 billion people by 2050, while maintaining livelihoods and respecting the environment. The pace of these changes and the scale of their human impacts and costs make it urgent to find solutions to strengthen the resilience of food systems. My research assesses the potential of a solution based on biodiversity, both wild and cultivated.Within this framework, my work aims to improve understanding of the links between agricultural activities, biodiversity, and the functioning and contributions of nature to societies through an interdisciplinary, multi-scale approach and a finalized agroecology approach. Two themes stand out:1. My research assesses the effects of biodiversity on the functioning of natural and cultivated ecosystems, past and present. Since 2016, I have been particularly interested in crop diversity as a lever for stabilizing agricultural yields in the face of climatic variations. I am contributing to the advancement of knowledge on the mechanisms of diversity-stability links and the spatial scales - from farm to country - at which these links are articulated. This research supports a dynamic vision of agroecosystems (stability vs. annual yields, climatic variability) and goes beyond the study of dominant species (rice, wheat, corn, soybean) to integrate the diversity and composition of species and varieties cultivated by farmers.2. In line with ethnoecology, my work draws on farmers' local knowledge to trace past changes in crop diversity and highlight the link between farmers' values towards the plants they grow and external factors (i.e. climate change) in the plant selection process. This research supports greater recognition of the central role of farmers and their multiple perceptions, knowledge and values in political decisions on adaptation, particularly to climate change.My project aims to identify more concretely the spatial scales and crop-species combinations that maximize the biological insurance effect and thus stabilize food production (axis 1). I then hope to go beyond the limits of a monodisciplinary and monofunctional approach to build a more holistic vision of the multiple functions-agronomic, ecological and socio-cultural-supported by agrobiodiversity. I thus propose to (i) construct and characterize the geometry of the multifunctional space occupied by cultivated plant species, (ii) monitor the inter-annual dynamics and stability of this space and (iii) assess its vulnerability to climate change (axis 2).