PARENT SESSION
Organized Oral Session 10: Reducing habitat fragmentation by roads: A comparison of measures and scales
Organizer(s): JAG Jaeger, L Fahrig, and W Haber
Monday, August 8, 1:30 PM - 5:00 PM, Meeting Room 511 B, Level 5, Palais des congrès de Montréal

Effects of bundling of roads on population persistence.

Jaeger, Jochen^*,1, Fahrig, Lenore², ¹ Swiss Federal Institute of Technology ETH Zurich, Zurich, Switzerland, Switzerland² Ottawa-Carleton Institute of Biology, Carleton University, Ottawa, Ontario, Canada

ABSTRACT- Roads act as barriers to animal movement, thereby reducing the accessibility of resources on the other side of the road. They also increase wildlife mortality due to collisions with vehicles, and reduce the amount and quality of habitat. The strength of these effects depends on the amount of traffic. To minimize these effects, the bundling of roads and traffic has been suggested because it keeps as large areas as possible free from disturbances due to traffic. This can be done in two ways: avoiding the construction of new roads by upgrading of existing roads, and placing new roads close and in parallel to existing roads. However, this suggestion has been criticized because the accumulated effects of several roads bundled together, or an upgraded road with more traffic on it, may create a stronger overall barrier effect that may be more detrimental to population persistence than the even distribution of roads across the landscape. We used a spatially explicit individual-based simulation model of population dynamics to evaluate the effectiveness of road and traffic bundling. We compared the probability of population persistence and the time to extinction for three different road configurations and different types of animal behavior at the road, when traffic volume was varied. Our results support the bundling concept. Population persistence was generally better when all traffic was put on one road than when it was distributed on several roads across the landscape. If traffic cannot be combined on one road our results suggest it is better to bundle the roads close together than to distribute them evenly across the landscape.

Key words: barrier effect, road effects, spatially explicit population model, traffic mortality