Primate extinction, the legacy of 40 years' road expansion in Colombia

Primates are declining worldwide and rapid infrastructure expansion, particularly roads, threatens their habitat. New roads fragment habitats allowing anthropogenic activities to occur in once pristine ecosystems; this is particularly impactful in tropical areas with high endemic biodiversity, as is occurring with primates in Colombia. However, temporal assessments of how roads impact local biodiversity are rare. We conducted a comprehensive assessment of the exposure of Colombian primates to roads from 1970 to 2015. Using a spatially explicit and species-specific approach, we estimated the critical road density and the critical patch size primate species can withstand before going locally extinct. Then, overlapping 15 primate species (~40% of the primate species present in Colombia) ranges with Colombia's road networks over time, we determined the road expansion scope within each habitat and consequent fragmentation. Comparing the species critical road density and patch size, we determined the degree of road exposure of each species over time and its vulnerability to local extinction. Our results show that between 1970 and 2015, there were nearly 40 000 km² where at least one species was at risk of local extinction, due to road expansion, principally in the Andean and Caribbean regions. Primates in these regions faced the greatest exposure to road impacts, with an average 16% increase in the amount of affected habitat during this period. Species in most need of conservation based on road exposure rankings are: Cebus versicolor, Aotus griseimembra, Ateles hybridus, Saguinus leucopus and Saguinus oedipus. Our study contributes to understanding road impacts on local biodiversity in one of the biodiversity hotspots across the tropics and highlights the need of infrastructure accounting for the necessary mitigation and conservation actions.