Understanding drivers of vegetable agro-biodiversity in smallholder farming in northern Vietnam

Vegetables play essential roles in smallholder farming households by contributing to food, nutrition, income, feed, and resilience. Yet, compared to staple crops, vegetable diversity and its link to seed systems remain understudied. This thesis explores how vegetable agro-biodiversity is shaped, maintained, or lost through farmers’ crop and seed management practices in northern Vietnam. Using mixed methods, including household surveys, interviews, focus groups, and participatory experiments, the research shows that vegetable diversity was strongly linked to farmers’ use of multiple seed sources, especially self-saved seed and local markets. Diversity accumulates across spatial levels, with rare vegetables maintained through individual household preferences and seed saving. Focusing on pumpkin varieties, the thesis further demonstrates that farmers’ seed and variety choices were adaptive and shaped by market opportunities, labour requirements, and changing livelihood strategies rather than a simple adoption processes. The thesis highlights the central role of informal and intermediate seed systems in sustaining vegetable agro-biodiversity over time.