**2. How are marine protected areas conceived?**

More recently than on land, the creation of MPAs began in the 1960s and accelerated in the mid-1970s. Today, MPAs have become one of the key tools in ocean management, used throughout the world to protect species and habitats, maintain the functioning of ecosystems and ensure a sustainable use of marine resources [18].

An MPA is first and foremost a legal status intended to provide it with visibility, prerogatives and stable integration in the local institutional context. However, within a country, or from one country to another, statuses are extremely diverse. The IUCN typology [22] shows a gradient between "full protection" status (nature without humankind), the legacy of a Western school of thought that sets humankind against wild nature [23], and zones for "the sustainable use of natural ecosystems", open for multiple uses, such as the Multi-Use Marine and Coastal Protected Areas in Chile. However, other points of differentiation exist, including either directly via conservation, or via fishery management (the Marine Fisheries Management Area in Cambodia, Extractive Reserves in Brazil). Behind the diversity of statuses is hidden the idea that a status can be considered as protection, an idea present in narratives in which classified surface areas are added up and considered protected. However, according to a global assessment of MPAs in 1995, only 29% of them achieved their objectives [24]. Jameson et al. [25] highlight two causes: their location, with MPAs subject to too many uncontrollable external influences (atmospheric, land- or ocean-based), and their management, limited by weak institutional and community-based capacities as well as inappropriate size with regard to the issues at stake. Furthermore, many MPAs throughout the world are qualified as "paper parks", meaning that they are legally designated but do little for conservation [18]. If this status does not necessarily provide protection, what does it provide, and what role does it play (or not) in a dynamic to devise measures?

An MPA is then a perimeter and regulations. MPAs were initially thought of as a "setting aside" of maritime areas, with the IUCN having first defined them as "*any area of intertidal or sub-tidal terrain, together with its overlying water and associated flora, fauna, historical and cultural features, which has been reserved by law or other effective means to protect part or all of the enclosed environment*" [26]. The law, by means of regulations combined with zoning, is the primary "effective means" of action envisaged. The definition of MPAs evolved in 2008 when the IUCN assimilated them with Protected Areas (PAs) defined as *"a clearly defined geographical space, recognised, dedicated and managed, through legal or other effective means, to* 

*achieve the long term conservation of nature with associated ecosystem services and cultural values"* [27]. Although it is no longer a question of "setting aside", the use of legal regulations remains central: it is a constitutive element of MPAs along with the perimeter. With regard to perimeters, although it may be relatively straightforward on land, this geometrical vision of space poses various challenges at sea. Among the specificities linked to the marine character of an MPA identified by Day et al. [22] are the fact that boundaries are difficult to establish, that the protected elements are not always visible, that the scale of marine connectivity between ecosystems and habitats is vast, and that monitoring activities is made more complex by the fact that there are many more access points to a specific area than there are on land. Consequently, what is the reality of a perimeter and how should it be considered? An MPA is defined by its perimeter, and managed with the aim of achieving a higher level of protection than the areas surrounding it [28], but how, in reality, do managers come to terms with these limitations?
