Designing ecological corridors in a fragmented landscape: A fuzzy approach to circuit connectivity analysis

• Permeability and fragmentation, when taken individually, do not fully describe landscapes.
• The Fuzzy Functionality Index (FFI) combines permeability and fragmentation.
• The FFI yields a comprehensive ecological overview of landscape complexity.
• The use of circuit theory with FFI identifies connecting corridors among focal points.

Landscape connectivity analysis is a major tool in supporting biodiversity conservation. Several methodologies have been developed to tackle it by following two main paths. The first path exploits graph approaches and models focal nodes’ connections on a resistance/conductance matrix depending on focal species’ movement potential. The second path considers geometrical pattern analyses based on the calculation of structural landscape metrics. These approaches separately investigate functional and structural features of the landscape, and may come short of a total definition if used separately. Here we propose a new scalable, modular, participative and open-source procedure based on Fuzzy logic to combine the functional and structural aspects of connectivity. We applied this method on the highly fragmented landscape of the Po Plain, focusing on its rare and endangered plain springs named fontanili. We identified an expert panel and involved it in the assignation of permeability values of land use classes with respect to the capacity of movement of animal species typical of fontanili. We concurrently performed a quantitative evaluation of the landscape fragmentation with a moving window. We found that the functional and structural evaluations were poorly correlated in the area under study (Pearson's r = −0.35, p < 0.001). We thus integrated these two non-overlapping analyses of the landscape by Fuzzy logic using thresholds and combination weights obtained from questionnaires proposed to the expert panel. The resulting index, termed Fuzzy Functionality Index (FFI), improved the level of information associated with landscape classification. By merging functional and structural aspects of the landscape, the FFI allowed us to discriminate different functional values of equally permeable parcels and vice versa. We demonstrate that FFI may act as a conductance measure in a circuit theory approach, highlighting ecological corridors between focal points of species’ distribution. We present FFI as an effective predictive index to inspect complex and non-linear landscape dynamics.