Long-term vegetation dynamics and management challenges in coastal dunes: Insights from a resurvey of two Mediterranean sites in Italy

Coastal dune ecosystems play a vital role in shoreline protection and biodiversity conservation, yet they face growing threats from coastal erosion, human activity, and invasive species. Long-term vegetation monitoring is key to understanding these changes and guiding conservation efforts. This study resurveyed historical vegetation plots established approximately 20 years ago in San Rossore and Calambrone (Tuscany, Italy) to assess shifts in species composition and habitat conditions. Species abundance was visually estimated using the Braun-Blanquet method, and each relev´e was classified into one of five herbaceous habitats (1210, 2110, 2120, 2210, and 2230) according to the 92/43/EEC Habitats Directive. Changes in species richness and diversity were analyzed using Hill numbers, while temporal differences were assessed through the Wilcoxon test and rank-abundance curves. The resurvey revealed three key patterns: (i) a marked reduction in the number of resampled plots, with habitat 1210 halved in San Rossore and entirely lost in Calambrone; (ii) although diagnostic dune species have persisted, their abundance has declined, while ruderal and invasive alien species have increased; and (iii) in Calambrone, increases in species richness and evenness, coupled with a decline in dominance, suggest that beach tourism—particularly mechanical cleaning and trampling—has facilitated the spread of generalists and nonnative species. Overall, our findings highlight ongoing degradation and fragmentation of coastal dune habitats in San Rossore, where erosion is the primary threat, and in Calambrone, where intense tourist pressure prevails. Without targeted conservation actions in anthropized areas and structural interventions to mitigate erosion, further deterioration— and even the complete loss—of these habitats can be expected.