In the wake of different studies, the intention in this chapter is to perform a critical examination of the process of turning nature into heritage. Such a study, if used as a management tool, may help to yield broader debate on environmental governance. To do this we shall look at the two elements that lie at the heart of creating heritage, namely conserving and enhancing the value of a terroir particularly through ecotourism and other productive environmental activities under way in the two Biosphere Reserves of the Yucatán : Celestún and Ría Lagartos. It seems that a heritage creation process is taking place, as the sign at the entrance of the Ría Lagartos reserve and the management plans of each Reserve suggest. It is, however, rather discrete, as no other indication has so far been detected in the rhetoric of the different stakeholders on the Yucatán coast. Does it really point to the emergence of a heritage process ? Is this the starting point for such a process ? What are the potential social, economic and political implications of such a process ? Does it help to reduce unequal relations or does it exacerbate social and economic marginalisation ?