Conservation challenges of the endangered gravel grasshopper Chorthippus (Glyptobothrus) pullus along Alpine rivers: Insights from remote sensing in Northwestern Italy

Floodplains are considered among the most endangered land types on a global scale. Only a few natural and semi-natural floodplains remain in the European Alps and are currently considered threatened. This study focused on Chorthippus (Glyptobothrus) pullus (Philippi, 1830), a small grasshopper widely considered an indicator of well-preserved riverine habitats. In the European Alps, this species now survives alongside very few watercourses, showing an increasingly rarefied and fragmented distribution due to habitat loss, mainly caused by artificial flow regulation. Presence data were collected in the upper Susa Valley (NW Italy) along transects positioned in floodplains and constrained reaches of the Dora Riparia and Dora di Bardonecchia rivers. A species distribution model was implemented using topographic variables and Normalized Difference Vegetation Index derived from remote sensing. Suitability and connectivity maps were produced to identify key conservation areas. Furthermore, the times of colonization, persistence, and extinction of this species along the vegetation succession at the patch level were estimated. The study revealed the presence of a significant population of C. pullus in the study area, primarily distributed in large floodplains. Connectivity between suitable areas was limited by the regulation of certain river sections, particularly in urbanized areas. The results confirmed it as a pioneer species, which tends to become extinct in patches when an undisturbed succession reaches an unsuitable stage for the species in about 12 years from bare soil. According to the study results, the conservation of this species depends on the maintenance of large floodable surfaces, which create a mosaic of patches with varying flooding frequencies. Specific recommendations are provided for its long-term conservation in the upper Susa Valley.