Discrepancies between climate velocity and dispersal capacity threaten subalpine forests in Northern Italy

Saman Ghasemian Sorboni 

The acceleration of anthropogenic warming is fundamentally altering the climatic space available to foundational conifer species in European alpine environments. This study evaluates the potential impacts of future climate scenarios on the spatial distribution and elevational displacement of four key taxa (Abies alba, Larix decidua, Picea abies, and Pinus sylvestris) in the Italian Alps. We employed an ensemble modeling framework, integrating climatic and topographic predictors under two Shared Socioeconomic Pathways (SSP1-2.6 and SSP5-8.5) for mid- (2050) and late-century (2070) time horizons. The projections indicate a universal trajectory of habitat contraction and forced upslope migration across all modeled taxa, primarily driven by temperature and precipitation seasonality. While A. alba demonstrated relative spatial stability under moderate warming, P. abies exhibited the highest vulnerability, with a projected 87.8% reduction in climatically suitable area by 2070 under the high-emission scenario. Elevational analyses revealed that A. alba, L. decidua, and P. sylvestris would require sustained upslope migration velocities exceeding 70 meters per decade to track their optimal thermal niches. Conversely, the severe niche deterioration for P. abies under extreme warming resulted in a projected net downward shift, indicating a potential restriction to localized topographic micro-refugia rather than a biological migration. The required climate velocities substantially exceed the natural seed dispersal capacities of these long-lived conifers, introducing a pronounced migration lag. Consequently, relying solely on natural regeneration may prove insufficient to maintain current distributions. Sustaining these alpine forests will likely require targeted climate-adaptive management, including the protection of micro-refugia and the evaluation of assisted migration.