Integrated modelling of functional and structural connectivity of river corridors for European otter recovery

Connectivity may be structural, based on adjacency of landscape features, or functional, based on howthat adjacency translates to movement of organisms. We present a modelling approach that elucidatesboth aspects of connectivity to identify vital corridors and conservation priorities in a river network.For the dendritic network structure of river systems, at first a graph theoretic structure is developed tomodel the river network at the segment scale. To derive functional connectivity, a Bayesian hierarchicalmodelling of species dispersal is applied to infer the influence of riparian corridor characteristics to thespecies colonization.The integration of the functional and structural component is realized with a graph-theoretic con-nectivity measure. With this approach, the European otter colonization of the Loire river basin over 25years is modelled on the basis of large datasets on riparian corridor land use and hydromorphologicalcharacteristics of a 17,000 km river network. Channel straightening and riparian forest fragmentation aredetermined to be key elements to the functional connectivity. Road infrastructure is distinguished as acritical habitat factor, but not so much an obstacle for the species movement in the riparian corridor. Inte-gration of the Bayesian model posterior colonization probability in the integrated connectivity analysisreveals the importance of the river network density to the otter colonization and locates conservationpriorities mainly in the lower parts of the river basin.Synthesis and applications: Both functional and structural connectivity are essential elements in thecontexts of ecological network identification for species conservation and recovery. We successfullydeveloped an integrated modelling of both components of connectivity that highlighted the importanceof the downstream basin for a well-connected ecological network for the otter.