Connectivity metrics for conservation planning and monitoring

Abstract

Conservation plans increasingly include goals to maintain a connected network. For example, planners might design a linkage between two conserved areas, or the parties to the Convention on Biological Diversity might set targets for a well-connected system of protected areas for each nation. Here we describe 35 metrics that can quantify connectivity of focal patches or of networks and monitor changes over time in an ecoscape (landscape or seascape). The connectivity metrics fall into four categories: (1) structural connectivity metrics derived from binary maps and species-nonspecific spatial functions, (2) connectivity metrics derived from binary maps and species-specific population sizes and dispersal functions (3) metrics derived from multi-state maps and species responses to those states, and (4) metrics of functional connectivity reflecting observed flow of organisms or genes. We provide a decision tree to select which of these metrics are most appropriate for a given conservation goal and broad ecoscape context. Functional connectivity metrics may be preferred if conservation is focused on particular species or if data are available to parameterize models for a suite of species that represent needs of the focal biota. However, with climate change, ecoscapes need to facilitate movements of all species that need to adapt by shifting their ranges. Because an intact network of relatively natural areas may support movement for many species, structural metrics that consider the human footprint should be used in all coarse filter approximations of functional connectivity in shared ecoscapes.