This article seeks to analyze, from a diachronic perspective, a diversified set of initiatives of environmentalization/ecologization of agriculture and the agri-food system, contextualized in the Sierra Region of Rio de Janeiro, particularly in the municipalities of Petrópolis, Teresópolis and Nova Friburgo. The reflections presented here seek to establish a dialogue with an emerging field of studies, of an interdisciplinary nature, which takes as an object of investigation the processes of transition to sustainability. The research seeks to integrate a systemic approach to the study of practices and experiences of social actors, also incorporating contributions from Brazilian critical geography and French sociology. The work was based on a diverse set of methodologies including document analysis, semi-structured interviews, and participant observation. The results achieved highlight the effects generated by a heterogeneous set of territorial containments, which impose limits to the incorporation of sustainability principles into the agri-food system at territorial level. At the same time, they draw attention to the agency capacity demonstrated by social actors in the construction of collective and individual projects, enabling the emergence, over time, of a shared field of relations, interpretative frameworks, and controversies, described in this research as an ecology of projects.