Multilayer Network Analysis Reveals Connectivity Synergies Between Protected Area Levels Across Various Taxonomic Groups

Assessing connectivity among protected areas (PAs) is vital for conserving species movement in fragmented landscapes; yet, most studies consider only a few taxa and ignore interactions between protection levels. We combined a recently developed framework to identify ecological continuities with a multilayer spatial network approach to quantify connectivity among strict and non-strict PAs, and their synergies, across metropolitan France. This was carried out for 397 vertebrate, invertebrate, and plant species from the national PA plan at an ecologically relevant 1-km² resolution. Results emphasized that non-strict PAs largely contribute to protected habitat accessibility across taxa, though connectivity patterns varied between taxonomic groups. Importantly, we showed that non-strict protections can synergize with strict protections to substantially enhance the amount of accessible protected suitable habitats. Our findings highlight the need for coherent PA expansion, strategically improving connectivity. Synergistic PA planning and corridor designation, leveraging new conservation tools, should notably provide viable solutions.