Global changes are disrupting the traditional missions of protected areas and challenging the tenuous links between societies and their environment regarding nature conservation. In this project, which brings together scientists in philosophy, geography, ecology and conservation science, we question how to reinvest the concepts of “nature” and “naturalness” in what has become the Anthropocene. Adopting a pragmatic approach, this theoretical inquiry will be rooted in concrete situations, namely in the complexities faced by managers and decision-makers regarding the meaning of nature conservation. We will examine three main subjects where human intervention for conservation currently faces complex questions: 1. the spontaneous return of species – when species that were not or no longer present in a protected area upset the socio-ecological equilibrium that has developed in their absence; 2. the management of exotic species – when managers have to take decision about populations that are not historically native to protected areas and 3. the debate on assisted colonization – which questions the acceptability of voluntarily transferring endangered species from their site of origin towards a site more favorable outside their actual distribution. The idea and bases for the designation of strict nature reserves free of human intervention will be treated as a backdrop to these questions. Addressing traditional questions in philosophy on the relationship between humans and nature, this proposition is at the crossroads of science, expertise and decision-making and thus contributes to the challenge of adapting conservation strategies in the face of global change.