Colombia started a five-decade-long series of developmentalist agrarian reforms in 1961, which oscillated between progression and regression with a degenerative effect on those they claimed to benefit: the peasantries. This thesis compares three case study sub-regions of Colombia to argue that many agrarian reforms acted instead as counter-reforms, contributing to depeasantisation, the loss of communities’ food sovereignty – and consequently their food security – and the depletion of agroecosystems. The three sub-regions investigated are: Los Montes de María, a warm-land; the coffee region, a temperate-land; and Santurbán, a cold-land. This thesis’ findings on peasantries’ accounts derive from privileging the voice of the same communities and, through them, their relational reading of their own territories and crops as historical subjects. The comparative analysis reveals how the uneven resolutions of the agrarian question in Colombia have driven a gradual loss of food sovereignty and agro-biodiversity in the three cases. It also questions the degradation of peasant cultures and their subsequent detachment from Nature, with damaging environmental impacts. To do so, this thesis has used an environmental history methodology, including the extensive use of oral history, combined with principles drawn from Critical Agrarian Studies (CAS), political ecology and decolonial/post-developmental approaches. The thesis focuses on the late twentieth and early twenty-first century: a period dominated in Colombia by the domestic adoption of international capitalist paradigms, such as developmentalist interventions, market liberalisation, and neoliberal globalisation, starting with the 1961 Social and Agrarian Reform and finishing in the 2013 Great Peasant Strike. This thesis reviews how these paradigms were embedded by the Colombian state, who colluded with local economic elites to drive agrarian counter-reforms with anti-peasant agendas. By doing so, it takes the study from global to local frames of analysis. This thesis argues that state-imposed agrarian reform actually served to abolish – partially or entirely, directly and indirectly – the peasants’ way of life and food production in the sites of study. It also argues that these were colonial, patriarchal, racist/classist and, in general, violent; and ultimately led to different levels of depeasantisation not just of the countryside but also of peasants themselves, and to the creation of food and environmental injustice.