Cost distances and least cost paths respond differently to cost scenario variations: a sensitivity analysis of ecological connectivity modeling

ABSTRACT

Biodiversity conservation measures designed to ensure ecological connectivity depend on the reliable modeling of species movements. Least-cost path modeling makes it possible to identify the most likely dispersal paths within a landscape and provide two items of ecological relevance: (i) the spatial location of these least-cost paths (LCPs) and (ii) the accumulated cost along them (’cost distance’, CD). This spatial analysis requires that cost values be assigned to every type of land cover. The sensitivity of both LCPs and CDs to the cost scenarios has not been comprehensively assessed across realistic landscapes and diverging cost scenarios. We therefore assessed it in diverse landscapes sampled over metropolitan France and with widely diverging cost scenarios. The spatial overlap of the LCPs was more sensitive to the cost scenario than the CD values were. In addition, highly correlated CD matrices can be derived from very different cost scenarios. Although the range of the cost values and the properties of each cost scenario significantly influenced the outputs of LCP modeling, landscape composition and configuration variables also explained their variations. Accordingly, we provide guidelines for the use of LCP modeling in ecological studies and conservation planning.

KEYWORDS:

• Least cost path modeling
• sensitivity analysis
• ecological connectivity
• spatial ecology
• landscape ecology

Acknowledgements

We are particularly grateful to ARP-Astrance team for its constant support along the project. Part of the analyses were carried out on the calculation ”Mésocentre” facilities of the University of Bourgogne-Franche-Comté. We thank Christopher Sutcliffe for revising the English manuscript

Disclosure statement

No potential conflict of interest was reported by the author(s).

Data and codes availability statement

The data that support the findings of this study are openly available in figshare at https://figshare.com/articles/dataset/Data_from_Cost_distances_and_least_cost_paths_respond_differently_to_cost_scenario_variations_/14924214

Besides, the functions sample_raster(), graphab_link(), mat_cost_dist() and link_compar() respectively used for sampling points within landscapes, computing LCPs between these points, computing cost distances and comparing LCPs spatially have been included into the R package graph4lg and are directly available here: https://cran.r-project.org/web/packages/graph4lg/index.htmlhttps://cran.r-project.org/web/packages/graph4lg/index.html. The OSO land cover raster data are available here: https://www.theia-land.fr/product/carte-doccupation-des-sols-de-la-France-metropolitaine/https://www.theia-land.fr/product/carte-doccupation-des-sols-de-la-France-metropolitaine/.

Additional information

Funding

This study is part of a PhD project supported by the ARP-Astrance company under a CIFRE contract supervised and partly funded by the ANRT (Association Nationale de la Recherche et de la Technologie). This work is also part of the project CANON that was supported by the French ”Investissements d’Avenir” program, project ISITE-BFC (contract ANR-15-IDEX-0003)

Notes on contributors

Paul Savary

Paul Savary is a PhD searcher at Université Bourgogne Franche-Comté and is financed by the ARP-Astrance company. He has been working on the influence of habitat connectivity on genetic diversity and differentiation patterns using spatial graphs.

Jean Christophe Foltête

Jean Christophe Foltête is a Professor of geography at Université Bourgogne Franche-Comté. His research topics include the spatial modeling of ecological networks. He led the development of Graphab, a software application dedicated to habitat connectivity analyses, and since then is leading or involved in research projects in ecology and landscape and urban planning.

Stéphane Garnier

Stéphane Garnier is a Senior lecturer in ecology at Université Bourgogne Franche-Comté. He has led several research projects on the influence of habitat amount, fragmentation and connectivity on population genetics and host-parasite interactions.

PS designed the study, carried out the analyses and wrote the first draft. All co-authors significantly contributed to the correction of the initial manuscript and responses to the reviewers.