The sensitivity of least-cost habitat graphs to relative cost surface values |
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Authors: | Bronwyn Rayfield Marie-Josée Fortin Andrew Fall |
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Institution: | (1) Department of Ecology and Evolutionary Biology, University of Toronto, 25 Harbord Street, Toronto, ON, M5S 3G5, Canada;(2) School of Resource and Environmental Management, Simon Fraser University, Burnaby, BC, Canada |
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Abstract: | Maintaining and restoring connectivity among high-quality habitat patches is recognized as an important goal for the conservation
of animal populations. To provide an efficient measure of potential connectivity pathways in heterogeneous landscapes, least-cost
route analysis has been combined with graph-theoretical techniques. In this study we use spatially explicit least-cost habitat
graphs to examine how matrix quality and spatial configuration influence assessments of habitat connectivity. We generated
artificial landscapes comprised of three landcover types ranked consistently from low to high quality: inhospitable matrix,
hospitable matrix, and habitat. We controlled the area and degree of fragmentation of each landcover in a factorial experiment
for a total of 20 combinations replicated 100 times. In each landscape we compared eight sets of relative landcover qualities
(cost values of 1 for habitat, between 1.5 and 150 for hospitable matrix, and 3–10,000 for inhospitable matrix). We found
that the spatial location of least-cost routes was sensitive to differences in relative cost values assigned to landcover
types and that the degree of sensitivity depended on the spatial structure of the landscape. Highest sensitivity was found
in landscapes with fragmented habitat and between 20 and 50% hospitable matrix; sensitivity decreased as habitat fragmentation
decreased and the amount of hospitable matrix increased. As a means of coping with this sensitivity, we propose identifying
multiple low-cost routes between pairs of habitat patches that collectively delineate probable movement zones. These probable
movement zones account for uncertainty in least-cost routes and may be more robust to variation in landcover cost values. |
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