There are numerous ways to measure structural connectivity. Different metrics take into account different factors, such as resistance, landscape heterogeneity, or spatial scale. As a result, many metrics are high in accuracy, but also complicated to learn and require complex data or analyses to implement.
This can be a hindrance to large conservation efforts that are national or even global in scale. Many of these conservation efforts focus on creating well-connected protected area networks, such as the 30×30 initiative at the center of the Kunming-Montreal Global Biodiversity Framework.
Yang, W., Kedron, P. and Frazier, A.E. 2024. Percentage of area protected can substitute for more complicated structural metrics when monitoring protected area connectivity. Ecological Indicators 158: 111387.
Policy makers tasked with implementing and monitoring connectivity within these networks are often short on time, resources, or in-depth knowledge (and sometimes all three), making it difficult to decide how to assess connectivity in a practical yet meaningful way.
A recent evaluation aims to provide guidance by going beyond conceptual reviews of connectivity metrics with empirical evidence that shows which metrics are analogous and whether certain ones are unique. Protected area networks across California, Colombia, and Liberia were assessed using 17 different connectivity metrics. Then a 10% expansion of each network across the landscape was simulated and the resulting changes in connectivity were measured using each metric.
The most important finding from the comparison of metrics is that, in the case of large-scale protected area networks, simply reporting the area percentage of land protected seems to be accurate enough to capture gains in connectivity. While other, more complicated metrics may better capture the nuances of landscape composition and configuration, percent area is an effective proxy for connectivity that dispenses with mathematical complexity without losing essential information.
This is good news for policy makers and managers, who can benefit from straightforward and easy to interpret numbers that make assessments and reports easier to implement and understand. The limited guidance available for choosing connectivity metrics makes it that much more necessary to identify when a simple metric will suffice. In most cases, the best connectivity metric is the one that will actually be used to reach conservation targets.
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