Quantitative monitoring of changes in forest habitat connectivity following the great eastern Japan earthquake and tsunami

Context In March of 2011 a huge tsunami devastated forest habitats along the coast of Sendai Bay in northeastern Japan. Evaluation and monitoring of the changes in habitat connectivity caused by this disaster are essential for managing the recovery of ecosystems and biodiversity. Objectives This research is designed to clarify changes in habitat connectivity caused by the tsunami, as well as subsequent changes due to the process of recovery and restoration. Methods Forest patch distribution maps were constructed from remote sensing data for 2010, just before the tsunami, 2011, immediately after the tsunami, and 2012 and 2016. A binary connection model was employed to generate forest patch network maps for each of the target years, for connectivity distances of 100 m, 800 m and 2500 m. Also, two quantitative connectivity indices, the Integral Index of Connectivity and Class Coincidence Probability were used to assess the changes in continuity. Results The forest patch network map and quantitative indices analysis both showed that not only had the forest habitats been reduced and fragmented by the tsunami, but that continuity kept declining in the following year. By 2016, however, newly established forest patches connected with extant ones, resulting in a slight recovery in habitat connectivity. Conclusions The network maps allowed clear visualization of changes in connectivity over the study period, and were backed up by quantitative results from the indices. This method is relevant for conservation of species with diverse mobility and habitat continuity needs, and for management and restoration of coastal ecosystems.