Abstract
Agriculture currently faces many challenges, including balancing the needs of growing populations with demands for reduced environmental impact; while confronting uncertain conditions of production that result from climate change. In this context, maintaining and enhancing biodiversity, both wild and domesticated, is essential to sustainable and resilient forms of agriculture. Wine-growing (the third most economically profitable crop in the world) is strongly threatened by climate change and has a history of compromising human and environmental health due to high pesticide use. This thesis uses a case study of wine-growing region of Gaillac, in the Tarn department of France to examine how agrobiodiversity is constructed at different spatial scales (from farms to wine-growing regions) to increase resilience in the context of climate change. More specifically, it has three objectives: (1) to characterize past and future dynamics of grape diversity from the scale of the farm to the winegrowing region, (2) to identify factors (exogenous constraints, individual motivations, sources of knowledge) that influence growers' planting decisions, and (3) to analyze the role of vine variety diversity in stabilizing inter-annual yields. To do this, I combine an ethnoecological analysis of local knowledge of growers regarding grape varieties and landscapes, with academic knowledge from ecology and agronomy. The combined analysis of historical agricultural data, archive documents, and semi-structured interviews reveals the abandonment of 174 grape varieties (77.6% hybrids) between 1960-2020 but also shows the maintenance of more than sixty grape varieties, making it one of the most diversified vineyards in France (Chapter 1). These dynamics occur in response to socio-economic, regulatory, technological, environmental, and cultural factors. Diversity was maintained partially as a hedge against the risk of poor harvests and to mitigate market volatility (Chapter 1). Within a regulatory structure that limits the selection of varietals, farmers choose grape varieties to fulfill agronomic, oenological, and commercial needs, but also to express sensible relationships woven into their relations with place and nature. Grape variety choice is thus a social process. An analysis of knowledge circulation networks (Chapter 3) also shows that the sources mobilized for obtaining information on grape varieties and weed management primarily circulate among peers, while knowledge about rootstocks and clones is obtained from nurseries and technical institutes. According to the surveys, most farmers state that perceived threats of climate change currently have little influence on their choice of grape varieties in the immediate future (Chapter 2, Annex 3), but it is changing the choice of planting sites (Chapter 1 and Annex 3). Despite this, my research shows that agro-biodiversity, reflected in the reproduction of varietals over a long period of time in the study site can play an important role in the resilience of wine-growing systems to climate change. Indeed, the analysis of yield data for the 2015-2020 period for three wine-growing regions (Cahors, Fronton, and Gaillac) reveals that the higher the grape variety diversity, the more stable yields are in the face of inter-annual climate variations (Annex 2). My thesis highlights the dynamic nature of grape diversity and demonstrates the benefits of biocultural approach for increasing resilience in the context of climate change.