The current biodiversity crisis has reduced the connectivity among ecosystems, and humans have created barriers to the movement of animals responsible for these connections by fragmenting the landscape. Furthermore, the extinctions of species with large movement ranges may have removed the coupling interactions among ecosystems, resulting in a larger decrease of ecosystem connectivity even where the landscape has not been fragmented. However, how these extinctions have affected ecosystem connectivity has been overlooked so far, and the real impact of anthropogenic pressure on ecosystem connectivity may have been underestimated. To understand the implications of the extinctions of terrestrial mammals for ecosystem connectivity, we estimated the connectivity that ecosystems would have today in the complete absence of anthropogenic pressure through time, and we compared it to its current value. Then, we explored how much of the current connectivity would be lost if currently threatened species would go extinct. We considered a total of 4,395 terrestrial mammals, both extant and extinct (n = 322), that were alive during the Late Pleistocene, making our study the first global assessment of how ecosystem connectivity has changed because of species extinctions and range modifications due to anthropogenic pressure.
Results/Conclusions
Ecosystem connectivity has decreased worldwide following the extinctions and range modifications of terrestrial mammals, and it will continue to decrease if threatened species would go extinct. Particularly, ecosystem connectivity has been reduced in Europe, North America, and South America, which were more severely affected by human pressure that promoted the extinctions of megafauna (>44 kg) with large movement ranges. Africa and Asia, which conserve today a larger proportion of the original megafauna and relatively more intact connectivity, will be affected by future extinctions, and their ecosystem connectivity will continue to decrease if threatened species would go extinct. In general, most of the connectivity decrease is due to the extinctions and extirpations of megafauna. Nevertheless, ecosystem connectivity can be partly restored to its original value by re-introducing megafauna species in their natural geographic ranges. Overall, our results show that ecosystem connectivity has decreased worldwide because of anthropogenic extinctions and range modifications of terrestrial mammals, especially megafauna.