Rural territories and cultures have been increasingly sacrificed through depopulation, invasion by infrastructure, and the presence of industries which are incompatible with agriculture. Meanwhile, the expansion of urban space through demographic agglomeration and the concentration of activities in cities is leading to a progressively urbanised world. This article sheds light on the particularities of the relationship between urban expansion and the assault on agrarian modes of existence that survive at the diffuse urban frontiers in Central Mexico. A multiple case study was carried out; nine social-environmental conflicts where an agrarian community resisted the installation of urban infrastructure or city enterprises were analysed through the perspective of Political Ecology and environmental justice. Peasant communities question the political, economic, environmental, and cultural factors of the hegemonic social configuration as urban megaprojects menace their territory. In their struggles, they highlight that urban development undermines the very conditions necessary for the existence of the city, as its social metabolism depends in part on the resources these rural communities are defending.