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 how that adjacency translates to movement of organisms. We present a modelling approach that elucidates both 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 to model the river network at the segment scale. To derive functional connectivity, a Bayesian hierarchical modelling of species dispersal is applied to infer the influence of riparian corridor characteristics to the species colonization.The integration of the functional and structural component is realized with a graph-theoretic connectivity measure. With this approach, the European otter colonization of the Loire river basin over 25 years is modelled on the basis of large datasets on riparian corridor land use and hydromorphological characteristics of a 17,000km river network. Channel straightening and riparian forest fragmentation are determined to be key elements to the functional connectivity. Road infrastructure is distinguished as a critical habitat factor, but not so much an obstacle for the species movement in the riparian corridor. Integration of the Bayesian model posterior colonization probability in the integrated connectivity analysis reveals the importance of the river network density to the otter colonization and locates conservation priorities mainly in the lower parts of the river basin.Both functional and structural connectivity are essential elements in the contexts of ecological network identification for species conservation and recovery. We successfully developed an integrated modelling of both components of connectivity that highlighted the importance of the downstream basin for a well-connected ecological network for the otter.