Making graph theory operational for landscape ecological assessments, planning, and design

Graph theory and network analysis have become established as promising ways to efficiently explore and analyze landscape or habitat connectivity. However, little attention has been paid to making these graph-theoretic approaches operational within landscape ecological assessments, planning, and design. In this paper, a set of both theoretical and practical methodological developments are presented to address this issue. In highly fragmented landscapes, many species are restricted to moving among small, scattered patches of different resources, instead of one, large patch. A life-cycle based approach is therefore introduced, in which a metapatch is constructed, spanning over these resources, scattered across the landscape. The importance of spatially explicit and geographically defined representations of the network in urban and regional planning and design is stressed, and appropriate, context-dependent visualizations of these are suggested based on experience from real-world planning cases. The study moves beyond the issue of conservation of currently important structures, and seeks to identify suitable redesigns of the landscape to improve its social–ecological qualities, or increase resilience. By introducing both a system-centric and a site-centric analysis, two conflicting perspectives can be addressed. The first answers the question “what can I do for the network”, and the second, “what can the network do for me”. A method for typical planning strategies within each of these perspectives is presented. To illustrate the basic principles of the proposed methods, an ecological study on the European common toad (Bufo bufo) in Stockholm, Sweden is presented, using the betweenness centrality index to capture important stepping-stone structures.