A growing number of governments and donors are promoting the formalization of artisanal and smallscale mining (ASM). They believe that doing so puts them in a better position to govern the sector, and manage the social and environmental impacts of its activities. Mainstream formalization processes are based on the assumption that clear property rights enable the recipients of these rights to capitalize their possessions. Because of reciprocal obligations, the argument follows that formalized ASM actors then better embrace the social and environmental norms regulating their activity. This paper reflects critically on attempts made to formalize ASM in Madre de Dios in Peruvian Amazonia. We share local perceptions of ASM impacts, and broaden understanding of the relationship between mainstream formalization and more bottom-up processes for governing and managing ASM impacts. We forward mesoscale collaborative approaches to impact management. In Madre de Dios, this could involve the appointment of a regional mediator with a strong mandate, establishment of a mobile formalization office, and the implementation of a series of coordinated but independent impact management activities through an impact management plan. This approach would not involve a stepwise procedure in which the failure to achieve one goal would prevent the pursuit of others.