I am first going to develop a sort of cartography of the different meanings and usages of “biodiversity”, which will emphasize a few leitmotives. Next, to introduce some of these leitmotives, I will highlight two or three important elements in the process through which the term came to form a decisive role both for scientists from different fields linked to ecology, and the politicians or lawyers involved with the policies that govern the consequences of human actions on nature. In the conclusion, I suggest that, in the same way as cognition is now seen as “situated cognition” because the agent is not detached from the world where its cognition takes place and has effect, biodiversity is something like a “situated concept”, a concept that does not get its legitimacy from models, theoretical elaborations and empirical data, but from the realization that something is altered in the biological world as such.