Abstract
In the current regime of ecological crisis, one generally expects actions and decisions about environmental issues to be enlighten by scientific knowledge. The aim of this thesis is to challenge this view by investigating how ecological knowledge and actions on nature are linked. I propose to study the interweaving between ecological knowledge, collective values and conceptions of nature in documents related to three types of actions (conservation in a nature reserve, environmental impact assessment, and ecological restoration). I lean on a field study where these actions are embodied, the plain of Crau (Bouches-du-Rhône, France). First, I examine how different types of ecological knowledge are translated in (and are influenced in return by) specific actions. I show that, in addition to the practical constraints of any action, this mutual relation is shaped by scientific cultural dynamics, as well as historical trajectories of these knowledges and actions. Then, I explain how the need to guarantee both credibility and legitimacy create an inherent tension in environmental actions. Finally, I explore how knowledge is based on preconceptions about our relationships with nature, and lead to specific ways of acting. From these insights, I suggest some trails to know and act differently with nature in the context of current ecological issues.