Modeling the effect of roads and other disturbances on wildlife populations in the peri-urban environment to facilitate long-term viability

Roads and traffic exhibit a multitude of impacts on wildlife populations. Most road ecology research seeks to assess the quantity and diversity of fatalities from collisions with vehicles, while studies documenting the impact of roads on the structure and sustainability of wildlife populations adjacent to roads have been lacking. Populations of wildlife existing within the confines of fragmented reserves are particularly susceptible to fatalities on roads, especially those situated within peri-urban and semi-rural matrices. We chose to examine the effects of disturbances, including fatalities on roads, using four case studies from Australia. These studies included a range of fauna, including the long-nosed bandicoot, the koala, and two studies of the swamp wallaby. To explore the impact of the various threats to wildlife living in peri-urban reserves, each case study utilized a population modeling approach. A combination of PVA modeling and sensitivity analysis was used to assess the impact of disturbances on the populations and identify appropriate management options to target disturbances. We discuss the utility of this approach in enabling conservation managers to assess the long-term viability of wildlife in these environments and in establishing management targets for improving viability in populations predicted to decline. In all four cases road fatalities were a major disturbance, but the different landscape characteristics of each reserve and other threat levels altered the relative impact of roads. The findings suggest that the combination of a range of management options, such as road fatality prevention, control of predation, and improvements in immigration and fertility, are often necessary although the exact combination will be location specific. Road management in the peri-urban environment can play a substantial role in ensuring the persistence of isolated populations in protected reserves that are surrounded by, and traversed by, roads. Given the broad geographic scale of roads, their effect on wildlife populations may be best understood from a landscape perspective, taking into account other disturbances that may be influencing population viability. We recommend the integration of PVA, sensitivity analysis, and GIS-based dispersion models as a suitable means for addressing both the temporal and spatial impacts of roads in order to successfully manage wildlife populations