The assumption is that a linkage is practical and that mice will survive there. The former would serve to protect or enhance the genetic diversity of each subpopulation. The structure of the linkage would differ in each case. In some cases this division is subjective or based on expertise of individual scientists. These are areas known to the ST that are not currently suitable for occupation by PMJM or are believed to be obviously degraded.
Examples are with severely overgrazed zones or some actively mined areas.
The important point is that they may be restored to high quality if the stakeholders choose to do so. Should the stakeholders not do so, it would increase the risk of a given population. Such designates zones are often chosen knowing that the restored area could significantly increase the potential number of mice in a population. Should these areas not be restored, they should be considered linkages, or at worst, barriers between subpopulations. Barriers between populations reduces the population size of each constituent part.