Ceia-Hasse, A., Borda-de-Àgua, L., Grilo, C. y Pereira, H.M. Global impact of roads on carnivores: which species and where? 2014 IENE International Conference. Programme and abstracts. Malmö: Infrastructure & Ecology Network Europe. 2014, pag. 108. ISSN 978-91-637-7327-3
Carnivores have life histories that can render them susceptible to roads, such as low population growth rates and great mobility. However, little is known about the effect of roads on population viability. In this study we determined which carnivore species are more affected by roads at the global level, and the spatial match between the number of species affected and road density. We used a reaction-diffusion model describing population dynamics to predict the impact of a road network on a population including the following parameters: dispersal distance, growth rate in favorable natural habitat patches, and growth rate in unfavorable habitats (roads). We applied this approach to 230 carnivore species at a global level. To rank the species most affected by roads we used maximum road density, and the minimum size of the patches between roads, above or below which populations cannot persist. We addressed the following tasks: 1) for each species we computed the maximum road density and the minimum patch size between roads that allow species to occur, using species-specific life histories and road mortality data; 2) we obtained the road density, and the number and size of the patches between roads that are observed within each species range, by intersecting each species IUCN range map with roads (density) map from openstreetmap; 3) we computed for each species the ratio of maximum to observed road density and the number and area of patches that are bigger than the minimum patch size; 4) we selected the species within the 5% percentile for these quantities as the most affected species. We found that family Ursidae has the highest percentage (43%) of species within the 5% most affected species, followed by family Felidae and family Canidae. We also found that 54% of the most affected species are not threatened by roads according to the IUCN, including 10 species that currently have an IUCN “Least Concern” status. The highest numbers of species affected by roads are found in Europe, North and Central America, South of Asia and China, and central-east Africa. However, while in Europe this high number of species is matched by high road density, this is not necessarily the case in the other regions, indicating that species can be affected even at low road densities. Our approach can be extended to any species for which the necessary life history data can be obtained, and can assist in developing conservation and mitigation measures. Furthermore, it can be applied at different spatial or temporal scales, such as projecting the impact of future road network development.
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