Hagimont asks why tourism and nature conservation came together in the twentieth century. He shows that shared concerns about the rise of tourism can be observed from the beginning of the century, but that at the same time tourism appears as a bulwark against hydroelectric development, seen as predatory. Tourism was theorized as a way of remunerating the protection of nature, which became an economic resource. Tourism can protect and develop, but it always threatens to destroy. It is a kind of pharmakon. Hagimont also shows that tourism was a response to the feeling of dispossession engendered by protection. He invites us to retrace the chronology of the social, economic and ecological reflections that gave rise to sustainable tourism.