Abstract
Roads have a pervasive multi‐faceted influence on ecosystems, including pronounced impacts on wildlife movements. In recognition of the scale‐transcending impacts of transportation infrastructure, ecologists have been encouraged to extend the study of barrier impacts from individual roads and animals to networks and populations. In this study, we adopt an analytical representation of road networks as mosaics of landscape tiles, separated by roads. We then adapt spatial capture–recapture analysis to estimate the propensity of wildlife to stay within the boundaries of the road network tiles (RNTs) that hold their activity centres. We fit the model to national non‐invasive genetic monitoring data for brown bears Ursus arctos in Sweden and show that bears had up to 73% lower odds of using areas outside the network tile of their home range centre, even after accounting for the effect of natural barriers (major rivers) and the decrease in utilization with increasing distance from a bear's activity centre. Our study highlights the pronounced landscape‐level barrier effect on wildlife mobility and, in doing so, introduces a novel and flexible approach for quantifying contemporary fragmentation from the scale of RNTs and individual animals to transportation networks and populations.
Highlights
In a world dissected and heavily impacted by roads, road ecology has emerged as an important applied ecological discipline (Forman and Alexander 1998)
Studies on gene flow and genetic diversity can address questions related to barrier effects and network-caused fragmentation at a large spatial scale (Simmons et al 2010, Proctor et al 2012), they are constrained by the time needed for genetic effects to appear in wild populations and do not capture individual space use
We have broken from the traditional approach of artificial and problematic inflations of scale by attempting to extrapolate from local barrier effects (Coffin 2007, Balkenhol and Waits 2009)
Summary
In a world dissected and heavily impacted by roads, road ecology has emerged as an important applied ecological discipline (Forman and Alexander 1998). Studies on gene flow and genetic diversity can address questions related to barrier effects and network-caused fragmentation at a large spatial scale (Simmons et al 2010, Proctor et al 2012), they are constrained by the time needed for genetic effects to appear in wild populations (especially for long-lived species, Anderson et al 2010) and do not capture individual space use. Many individuals in wild populations maintain home ranges for most of their life, it is important to focus on the impediment to long-distance migration and dispersal, and on the constraints that fragmentation poses to resident movements and the configuration of home ranges within the population (Morales et al 2010, Poessel et al 2014) When it comes to animal movements, ecologists have primarily studied roads as local barriers (Riley et al 2006, Sawaya et al 2014, Proctor et al 2015, Wilson et al 2015). We suggest solutions to both of these challenges to population- and network-scale assessment of barrier effects, which we implement using an empirical example
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