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

Integrating traffic, network location, and surrounding habitat to create a connected landscape.

Forman, Richard ^*,1, ¹ Harvard University, Cambridge, Massachusetts, USA

ABSTRACT- Using simple spatial models, three key variables (traffic, location in network, and habitat arrangement relative to roads) are evaluated for their effects on habitat loss, degradation and fragmentation. Although the overall approach may be new, parts of the picture have been successfully applied in, e.g., Germany, Netherlands, Massachusetts, Florida and New Jersey. First, the values of large patches (natural habitat), high connectivity, and small patches are used to ecologically evaluate a road segment, plus a road network, relative to the spatial arrangement of large patches, small patches, wide corridors and narrow corridors. Overall, a gradient emerges from the best arrangement (small habitat patch in center of a network enclosure) to the worst (large patch dissected by network). The best location for a road passing between two large patches is part way between the mid-point and a patch edge. Second, the curvilinear relationship between road traffic and wildlife crossing, as well as between traffic (noise) and effect distance on wildlife, are added to the analysis, along with spatial differences between natural and agricultural or suburban landscapes. Based on habitat loss, degradation and fragmentation, the ecologically worst situations are high and medium traffic in a natural area, and high traffic alongside a large natural patch in an agricultural/suburban landscape. For a given traffic flow, the best network form has a few large enclosures and is characterized by a few busy roads. Further modeling of network forms, traffic and habitat arrangements, plus empirical field studies, should convert the patterns uncovered into principles for transportation, ecology and society.

Key words: ecological effects of traffic, ecology of network form, habitat arrangement relative to roads, roads and habitat loss, degradation and fragmentation