Sustainability economics attempts to reconcile efficiency criteria with those of social justice in a context of environmental concern. This article aims at highlighting the fact that the Capability Approach offers an interesting perspective for the foundation of sustainability in economics. It primarily focuses on the major role that freedom brings as a normative basis for well-being and adds new insights for our understanding of human and environment relationship through the study of the constraints and opportunities that affect the individual. The final section of this article asks us to reconsider our Nature conservation choices by acknowledging the restrictive impact that they have on individual freedoms.