Assessing the impact of road developments on connectivity across multiple scales: application to Yunnan snub-nosed monkey conservation

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This paper proposes an integrative approach to assess the impact of several highway developments on the connectivity of high-elevation coniferous forests in Yunnan (China). These forests are the optimal habitat of the black and white snub-nosed monkey (Rhinopithecus bieti), an endemic endangered primate species. A graph-based approach is used for modeling the ecological network of this species and analyzing connectivity across several spatio-temporal scales, from daily movements to dispersal events. The aims of this paper are (1) to assess the impact of an existing highway by comparing connectivity with and without the infrastructure; (2) to assess the potential improvement of connectivity induced by diverting traffic from the highway to a tunnels/viaducts section under construction; (3) to compare several mitigation scenarios with potential reforestation measures. The analysis is carried out both at the global level to quantify changes in the overall connectivity at several distances and, at the local level to identify which parts of the network are the most vulnerable. The results show that the highway has a low effect (− 3.3%) on connectivity at the daily scale, but that increased gradually with distance (up to − 21.5% for the largest), however habitat loss is only − 0.1%. Some of the affected habitat patches are located 30 km north of the highway. The three mitigation scenarios have a different impact on connectivity. The third scenario leading to the creation of new habitat patches is the only one that strongly increases connectivity at several scales. This kind of graph approach can improve assessment of the impact of constructing a given infrastructure by taking into account the different scales of ecological processes and so can better target conservation measures for impacted species, here the emblematic, endangered, Yunnan snub-nosed monkey.