Influence of Transport Infrastructure on Nature

Abstract: Collserola Park (Barcelona) is a protected nature area occupying 8,500 ha. The park is subject to intense human pressure and includes an extensive transportation network made up of surfaced roads, forest trails and even a motorway and a railway line which form a major transport axis that crosses the Park.
As part of a wider study concerning the impact of transportation infrastructure on wildlife, roadkill data gathered since 1991 were analysed. These data come from several sources, basically from Park technical staff, wardens and from occasional roadkill studies. Since 2004 a more specific monitoring has been carried out of roadkills on roads and forest tracks in the Park by means of pre-established transects in order to obtain quantitative indices. In total, 865 roadkill incidents have been incorporated in the Park’s wildlife GIS database, of which 56% correspond to mammals, 20% to birds, 16% to reptiles and 8% to amphibians. This high percentage of incidents associated with mammals is related to the different detection rate of mammals in comparison to other groups. The mammals with the highest incidence of roadkills are wild boar Sus scrofa (21.4%), which have increased sharply in the last few years, hedgehogs, Erinaceus europaeus and Atelerix algirus (20.7%), squirrels Sciurus vulgaris (15.0%) and rabbits Oryctolagus cuniculus (14.4%).
Roadside habitats were characterised by means of 100 m wide buffers established around roads and overlapped with GIS land use maps of the Park. Also, other factors linked to the road itself were considered in analysis, such as the daily average density of traffic (DAD:vehicles/day) and velocity. Analysis of the incidents shows a positive relationship between the number of roadkills/km and DAD. On the other hand, there was also a seasonal trend to roadkills with a peak at the end of spring which coincides with the period population levels is maximal (presence of juveniles).
Incident black spots were identified, which differ according to species and which in the case of the wildboar, for example, coincide with connection zones between the two main forest areas of the Park.
Finally, it should be highlighted that roadkills are not necessarily the main impact of infrastructures, at least for most species concerned, but rather their effects are added to other impacts such as the barrier effect and habitat fragmentation which can have more damaging effects at the population level.
Key words: black spots, conservation, mammals, mortality, roadkills

Suggested citation: TenÄ‚Å s A., Cahill S.Ä.Ä„. & Llimona F. 2007. Long-term monitoring of wildlife roadkills in Collserola Park, Barcelona. Results from the first 15 years. In: B. Jackowiak (ed.). Influence of Transport Infrastructure on Nature. General Directorate of National Roads and Motorways, p. 99-107. Warszawa-PoznaÅ„-Lublin.
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