Table 1.

Protected Connected and related fractions and indicators, all expressed as percentages. ProtConn_Bound and the three fractions of ProtUnconn are newly presented here, while the other indicators were introduced by Saura et al. (2017). In this table, and throughout the rest of the article, the fractions of ProtUnconn are expressed as a percentage of the total land area of the country, and hence they sum to the ProtUnconn value. The fractions of ProtConn are expressed as a percentage of the ProtConn value and so they sum to 100. See Methods and Appendices B and C for further details. PA coverage (Prot) is not a connectivity indicator but it is included because of its widespread use in assessing PA systems and because it is a key benchmark for the connectivity indicators described.

Indicator name (acronym)	Description
Indicators referring to the entire connectivity, coverage or isolation of PAs in a country
Protected Connected land (ProtConn)	Percentage of the country covered by connected protected lands.
Protected Connected land bounded to the possibilities of the country (ProtConnBound)	Protected Connected land considering the part of PA connectivity that is in the power of the country to influence, i.e. excluding the isolation of PAs that is naturally imposed by the sea, and that due to foreign lands (out of the jurisdiction of the country). It is the same as ProtConn for countries with PAs distributed in a single landmass that is naturally and politically continuous (i.e. no PAs in land portions separated by the sea or by other nations), and higher than ProtConn otherwise. ProtConnBound is calculated as the difference between Prot and ProtUnconn[Design] (see below).
PA Coverage or Protected land (Prot)	Percentage of the country covered by PAs (either connected or not). Prot can never be smaller than ProtConn or ProtConnBound.
Protected Not Connected land (ProtUnconn)	Percentage of the country covered by protected lands that are isolated. It is simply the difference between Prot and ProtConn.
Protected Not Connected due to… (fractions of ProtUnconn referring to specific causes of PA isolation)
…the sea (ProtUnconn[Sea])	Percentage of the country land that is protected but not connected because of the natural isolation of terrestrial PAs imposed by the sea. This fraction will be higher than zero only in those countries in which PAs are distributed over multiple islands or landmasses
…foreign lands (ProtUnconn[Outland])	Percentage of the country land that is protected but not connected because of the lack of protection in foreign lands. This fraction will be higher than zero for a given country only when other nations dissect the country in several disjoint land portions in such a way that it is not possible to move between some of the country's PAs without traversing unprotected foreign lands.
…limitations in the PA system (ProtUnconn[Design])	Percentage of the country land that is protected but not connected because of limitations or deficiencies in the design of the terrestrial PA system of the country. This is the part of the PA isolation for which a country can be made accountable, i.e. that which is under the control of a country. It is the difference between Prot and ProtConnBound.
Protected Connected by moving… (fractions of ProtConn referring to specific components of PA connectivity)
…within Individual PAs (ProtConn[Within])	Percentage of the Protected Connected land that can be reached by moving only within individual PAs, i.e. how much land can be accessed by species if they move only within the limits of individual PAs.
…through Contiguous PAs (ProtConn[Contig])	Percentage of the Protected Connected land that can be reached by moving through sets of immediately adjacent (contiguous) PAs, without traversing any unprotected lands. This percentage excludes the protected land that can be reached by moving within a single PA, which is given by ProtConn[Within].
…through Unprotected lands (ProtConn[Unprot])	Percentage of the Protected Connected land that can be reached by moving through unprotected areas. It includes movements between PAs that entirely happen through unprotected lands and others that traverse unprotected lands in the initial and final stretches but that may use some protected land in between. The value of this fraction will be lower when PAs are separated by larger tracts of unprotected lands, making inter-PA movements less likely, particularly when the distances that need to be traversed through unprotected lands are large compared to the dispersal distance.
…through Transboundary Protected lands (ProtConn[Trans])	Percentage of the Protected Connected land within the country that can be reached by moving through PAs located outside the country's boundaries. It includes the effect of both transboundary PAs in the strict sense (i.e. individual PAs that extend across country boundaries) as well as of other PAs that, located outside the country, promote the connectivity between PAs in the country by acting as corridors or stepping stones between them.