Ecological solidarity is one of the fundamental principles of the 2006 law reforming French national parks and the 2016 law on biodiversity, nature and landscapes. In order to make an assessment of the appropriation of this principle in protected areas in France, we explore the use of the term solidarity by national parks and regional nature parks by a textual analysis of their charters. We question the relationship between the use of the three registers of solidarity (ecological, social and economic), with the socio-environmental context of the parks and the representations of human-nature relationships conveyed in the charters. The notion of solidarity appears to be mobilized by both park networks, but the types of solidarity as well as the objects on which these solidarities focus differ. Thus, the references to ecological solidarity and to nature are based either on a formalism of conventional, fictional and motivational beliefs or on a principle of integrated territorial management whose putative character of the public and nature participates in the legitimization of the existence of protected areas and their action. We conclude this exploration by questioning the place of the principle of ecological solidarity in the construction of "capable territories" that participate in the ecological, social, economic and energy transition within and beyond the boundaries of protected areas.