Megafauna extinctions have reduced biotic connectivity worldwide

Aim Connectivity among ecosystems is necessary to sustain ecological processes that promote biodiversity, community stability and ecosystem resilience, such as organism and nutrient dispersal. Along with human land use and habitat fragmentation, connectivity can also be affected by faunal changes. Here, we address this issue by studying how human-driven late Quaternary extinctions and extirpations of terrestrial mammals have affected the movement capacity of assemblages, an estimate of the potential connectivity among ecosystems promoted by wildlife. Location Global. Time period Late Pleistocene to the Anthropocene. Major taxa studied All 4,395 (4,073 extant and 322 extinct) terrestrial mammals alive in the Late Pleistocene. Methods We combined macroecological estimates of home range size with range maps of current and natural geographical distributions of species to investigate how human pressure has modified natural movement capacity of terrestrial assemblages and how movement capacity will respond to future extinction and rewilding scenarios. Results Our results showed that 74% of average and 83% of maximum movement capacity of Late Pleistocene mammal assemblages has been lost owing to prehistorical and historical extinctions and extirpations. We also found that movement capacity will decrease further if current extinction trajectories are not averted. However, our results showed that current average and maximum movement capacity can be restored to twice their current values under a full rewilding scenario and that average, but not maximum movement capacity, will increase under a conservative rewilding scenario, that is, without restoring the largest megafauna most likely to cause major human-wildlife conflicts. Main conclusions Prehistorical and historical losses of megafauna have caused severe decreases in movement capacity of mammal assemblages, hence large reductions in ecosystem connectivity. Reintroductions can partly restore biotic connectivity, especially when the largest megafauna are also restored. However, natural levels of movement capacity cannot be recovered fully without including ecological replacements for extinct species in rewilding efforts.