Climate change may increase landslide frequency despite generally drier conditions in the Mediterranean area

Abstract. This study presents a methodological framework to investigate the impacts of climate change on rainfall-triggered landslides at the subregional scale. Focusing on a ~ 170 km² area in the Partenio Mountains in southern Italy, we employed regional rainfall projections (CORDEX) under moderate (RCP4.5) and high (RCP8.5) emission scenarios for 2006–2070. Rainfall data were bias-corrected with observations from 2006–2023 and benchmarked against a synthetic dataset generated through stochastic reproduction of currently observed conditions. Physically based simulations of hydrological processes, coupled with slope stability analyses that account for unsaturated soil conditions, enabled event-by-event identification of landslides throughout the period. Statistical comparisons between scenarios were conducted across three rainfall homogeneous subregions. Results show a general tendency toward drier soil conditions, consistent with regional-scale climate studies, but with increasing rainfall variability across subregions. Despite this drying trend, projections indicate a significant rise in landslide occurrence, with a faster increase under RCP4.5 when compared to RCP8.5. This counterintuitive outcome reflects shifts in rainfall dynamics: under RCP8.5, landslides are mainly linked to more intense triggering rainfall, while under RCP4.5 they result from a combination of wetter antecedent conditions and more intense early-peak rainfall events. These findings emphasize the critical role of antecedent soil moisture in landslide initiation by showing its stable influence on landslide occurrence despite the rapid evolution of climate change. Overall, the methodology provides a transferable framework to assess local climate change impacts on geohazards by integrating bias-corrected climate projections with physically based hydrological–geomechanical modeling.