title: A few large roads or many small ones? How to accommodate growth in vehicle numbers to minimise impacts on wildlife.
abstract: Roads and vehicular traffic are among the most pervasive of threats to biodiversity because they fragmenting habitat, increasing mortality and opening up new areas for the exploitation of natural resources. However, the number of vehicles on roads is increasing rapidly and this is likely to continue into the future, putting increased pressure on wildlife populations. Consequently, a major challenge is the planning of road networks to accommodate increased numbers of vehicles, while minimising impacts on wildlife. Nonetheless, we currently have few principles for guiding decisions on road network planning to reduce impacts on wildlife in real landscapes. We addressed this issue by developing an approach for quantifying the impact on wildlife mortality of two alternative mechanisms for accommodating growth in vehicle numbers: (1) increasing the number of roads, and (2) increasing traffic volumes on existing roads. We applied this approach to a koala (Phascolarctos cinereus) population in eastern Australia and quantified the relative impact of each strategy on mortality. We show that, in most cases, accommodating growth in traffic through increases in volumes on existing roads has a lower impact than building new roads. An exception is where the existing road network has very low road density, but very high traffic volumes on each road. These findings have important implications for how we design road networks to reduce their impacts on biodiversity.
authors.affiliation: School of Geography, Planning and Environmental Management, The University of Queensland, Brisbane, Queensland, Australia; ARC Centre of Excellence for Environmental Decisions, The University of Queensland, Brisbane, Queensland, Australia; NERP Environmental Decisions Hub, The University of Queensland, Brisbane, Queensland, Australia.
authors.forename: Jonathan R
authors.initials: JR
authors.lastname: Rhodes
authors.affiliation: Office of Environment and Heritage New South Wales, Hurstville, New South Wales, Australia; School of Biological Sciences, University of Sydney, Sydney, New South Wales, Australia.
authors.forename: Daniel
authors.initials: D
authors.lastname: Lunney
authors.affiliation: Australian Koala Foundation, Brisbane, Queensland, Australia.
authors.forename: John
authors.initials: J
authors.lastname: Callaghan
authors.affiliation: School of Geography, Planning and Environmental Management, The University of Queensland, Brisbane, Queensland, Australia; NERP Environmental Decisions Hub, The University of Queensland, Brisbane, Queensland, Australia.
authors.forename: Clive A
authors.initials: CA
authors.lastname: McAlpine
mesh_terms: D000063:Accidents, Traffic; D000818:Animals; D001315:Australia; D003247:Conservation of Natural Resources; D006801:Humans; D015233:Models, Statistical; D009026:Mortality; D018986:Motor Vehicles / Q000706:statistics & numerical data; D048368:Phascolarctidae / Q000502:physiology* / Q000523:psychology; D014186:Transportation / Q000706:statistics & numerical data