Plan boundaries for terrestrial plans essentially follow existing or historic administrative jurisdictions. For marine areas, while the land/sea boundary and  international boundaries provide clear onshore and offshore boundaries, it is often the case that there are no clear lateral boundaries which might be followed in determining plan subdivisions.

In a UK/European context, the situation is further complicated by a plethora of existing legal, administrative and reporting boundaries operating at different scales in the marine area, for example:

  • Marine Regions identified under the Marine Strategy Framework Directive;
  • National boundaries with the devolved administrations;
  • Water body and river basin district boundaries identified under the Water Framework Directive;
  • Regional sea boundaries and State of Seas reporting boundaries.

It is also of note that the scope of national legal powers also varies with distance offshore, for example the EU has competence on fisheries matters beyond 6nm and licensing controls over cables vary within and beyond the limit of territorial waters.

It is desirable that marine plans should be based around ecosystem boundaries (Vincent et al 2004; MSPP Consortium, 2006; Gilliland and Laffoley 2009), although these may often be difficult to define clearly. It has also been suggested that plans should take account of the spatial scale at which human use activities occur if they are to be effective tools for their management.