Getting lost in the matrix? On how the characteristics and arrangement of linear landscape elements influence ecological connectivity

Abstract

Context: Linear landscape elements (LLEs) such as ditches and hedgerows can increase the ecological connectivity of habitat embedded within agricultural areas by acting as corridors for animal movement. However, we lack knowledge on how the spatial arrangement of LLEs influence dispersal, impeding our ability to offer robust advice on how best to add new LLEs to improve connectivity. Objectives: To examine how the width and spatial orientations of LLEs composing an intersecting network might influence connectivity across landscapes. Methods: We used an individual-based dispersal model to simulate the stochastic movement of small organisms through stylised LLEs of different characteristics. Landscapes were composed of two habitat patches separated by a grid-like network of LLEs composed of two types: (1) connecting-edges (touching patches on either end) and (2) transecting-edges (running perpendicular to connecting-edges). By altering numbers and widths of each LLE type we sought to understand the effect of these variables on inter-patch dispersal rates. Results: Increasing the number or width of connecting-edges improved connectivity but, conversely, increasing numbers or widths of transecting-edges reduced it. The greater freedom of movement offered by increasing numbers of transecting-edges may have inhibited connectivity, as individuals with limited perceptual-range were more likely to become trapped in complex networks and thus fail to navigate to suitable habitat patches. Conclusions: Orientation of LLEs with respect to landscape resources greatly affects their impact on connectivity. The addition of LLEs to landscapes may decrease their connectivity for small, flightless species if they do not directly channel dispersers toward landscape resources.