Protected areas in the world’s ecoregions: How well connected are they?

[Display omitted] •The Protected Connected (ProtConn) indicator is presented and globally assessed.•ProtConn differentiates protected, unprotected and transboundary connecting lands.•Spatial arrangement of reserves is only partially successful in ensuring connectivity.•Only a third of world’s ecoregions meet Aichi Target 11 on protected area connectivity.•Detailed ProtConn results available at the Digital Observatory for Protected Areas. Protected areas (PAs) are the main instrument for biodiversity conservation, which has triggered the development of numerous indicators and assessments on their coverage, performance and efficiency. The connectivity of the PA networks at a global scale has however been much less explored; previous studies have either focused on particular regions of the world or have only considered some types of PAs. Here we present, and globally assess, ProtConn, an indicator of PA connectivity that (i) quantifies the percentage of a study region covered by protected connected lands, (ii) can be partitioned in several components depicting different categories of land (unprotected, protected or transboundary) through which movement between protected locations may occur, (iii) is easy to communicate, to compare with PA coverage and to use in the assessment of global targets for PA systems. We apply ProtConn to evaluate the connectivity of the PA networks in all terrestrial ecoregions of the world as of June 2016, considering a range of median dispersal distances (1–100km) encompassing the dispersal abilities of the large majority of terrestrial vertebrates. We found that 9.3% of the world is covered by protected connected lands (average for all the world’s ecoregions) for a reference dispersal distance of 10km, increasing up to 11.7% for the largest dispersal distance considered of 100km. These percentages are considerably smaller than the global PA coverage of 14.7%, indicating that the spatial arrangement of PAs is only partially successful in ensuring connectivity of protected lands. The connectivity of PAs largely differed across ecoregions. Only about a third of the world’s ecoregions currently meet the Aichi Target of having 17% of the terrestrial realm covered by well-connected systems of PAs. Finally, our findings suggest that PAs with less strict management objectives (allowing the sustainable use of resources) may play a fundamental role in upholding the connectivity of the PA systems. Our analyses and indicator make it possible