Acting upon Livestock's Long Shadow to mitigate climate change, mass extinction, and other social-ecological crises requires fundamental changes in food practices. Labelled as "ethical consumers", vegans, vegetarians, and meat-reducing carnists already attract considerable attention. However, food practices on the production side, which are just as much an ethical issue, also require reconfiguration in order to achieve sustainable development. In a critical assessment of tendencies that depict consumer demand as the only legitimate means of change and depoliticise absolute reductions of animal-sourced foods, this thesis extends the locus of vegan food practices to various productive processes drawing on cases such as stock-based and stockfree farms, retailers, and food-related advocacy networks. By exploring these foodscapes, it is examined how the material-discursive boundaries between vegan and carnist food practices are drawn, particularly in response to animal agriculture as a sustainability challenge. Inspired by practice and materialist turns, my research builds on debates on ethical consumption, responsibility, and sustainability within sociological and geographical food studies. Relational and posthumanist approaches are drawn upon to conceptualise practices and conduct material-discursive analyses. Qualitative methods are applied to outline relations within and between agricultural and retailing foodscapes in Greater Manchester, Derbyshire, and South West England, involving a mix of participant observation (incl. field notes and photography), in-depth interviews with stakeholders on site, and an interpretative examination of their sustainability-related websites and reports. The findings revolve around the marginal but emerging agricultural and culinary paradigm of "vegan organic" production. It excludes the use of manure, bone meal, or other animal derivatives for the replenishment of soil fertility and relies instead on nutrient-fixing plants and practices such as composting or mulching. Thus, veganism, rather than being a dietary identity, becomes a relationally grounded approach to how vegans and plant foods come into being performatively through material-discursive practices. Conventionally, however, the term "vegan" as applied in both food regulations and everyday life, is merely a label either for people who abjure from animal products or for vegetal products. This dematerialised consumption-based mainstream conception of veganism personalises food practices, confines ethics to a sentimental care for domesticated animals, and depoliticises social-ecological reasons for veganism. In order to maintain a safe operating space for all life on Earth, I suggest that performing vegan food practices as much as possible is an undogmatic responsibility of ethical producers and consumers alike, regardless of their personal identities as vegans, vegetarians or "meat eaters" (carnists).