This article reintroduces the concept of 'appropriation of space' into current theoretical debates and empirical approaches in environmental psychology. We present an analysis of a case study conducted in a Barcelona metropolitan river corridor, aimed at exploring how the development of people-place bonds can foster pro-environmental behaviours in a natural open space. The multi-method qualitative analysis based on participant observation, documentary research and interviews with 57 inhabitants reveals a long-term process of appropriation of the riverside environment that typically results in a sense of responsibility of the subject towards it. The article specifically shows that the time factor is crucial in the explanation of the process of appropriation, and that future longitudinal studies in this and other cases will be required to assess more accurately its importance. Finally, we stress the benefits of taking proper advantage of citizens' cumulative awareness of the management of river corridors.