Tracing Vegetation Responses to Human Pressure and Climatic Stress: A Case Study from the Agri Valley (Southern Italy)

Projected climate changes in the Mediterranean exceed those in most European regions, yet their effects on vegetation remain uncertain. We investigated vegetation changes in the Agri Valley (Basilicata, Italy) using 318 plots, including 40 resurveys. Community-weighted Ellenberg indicator values (EIVs) and plant ecological groups were combined with long-term hydroclimatic anomalies reconstructed via the BIGBANG model (1951–2024), providing a long-term climatic baseline for interpretation. Significant shifts emerged in several EIVs, with clear habitat-specific patterns. Forests showed decreasing light and increasing moisture values, reflecting a higher presence of forest-associated species, though some diagnostic taxa declined. Grasslands exhibited increasing aridity, with a growing contribution of dry-grassland species and a decline in winter therophytes. Climatic analyses revealed pronounced long-term warming, accelerating after the 1980s, while annual precipitation remained highly variable without a monotonic trend. Recent years were marked by intensified drought, evidenced by declining SPEI values (2013–2022) and a higher frequency of dry months (SPEI ≤ −1). The convergence of vegetation responses, species turnover, and climatic anomalies supports climate-driven community trajectories. Despite limited land-use data, this multi-indicator framework effectively detects early ecological responses and identifies vulnerable habitats, providing valuable insights for the conservation and management of Mediterranean mountain ecosystems under ongoing climate change.