The general purpose of this article is to contribute to a broader comprehension of collective grassroots processes that generate effective social and environmental transformations in the practices of urban communities. We start with a brief analysis of the concept of 'ecological footprint', which has been widely used as a way of measuring sustainability. It will be shown, however, that there are limitations to the calculations of the ecological footprint, some of which are directly related to

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... roecological forms of production. Various environmental and social benefits of community agroecological production in the cities are then described and the importance of grassroots forms of organisation is reinforced. In the last sections we present the activities, results and challenges of an urban collective project developed in the city of Morelia, Mexico. The ways in which the Jícara Project changed community practices in reference to the production and use of resources, mental habits, communicative styles, and forms of collective organisation are discussed. In conclusion, we argue that the ecological, intellective and relational transformations promoted by the Jícara Project offer us a proof of what can be achieved through grassroots self-organised urban collectives.