Reconstructing the aquatic plant landscape of the Renaissance (Po Plain, N-Italy) according to the Erbario Aldrovandi (1551–1586)

Historical herbaria allow previous flora to be reconstructed and to understand long-term environmental changes. By using Ulisse Aldrovandi’s herbarium, one of the oldest of Europe, we attempted to reconstruct historical plant communities at the habitat level, selecting the ancient wetland system of Valle Padusa (SE Po Plain, northern Italy) as a case study, which has now disappeared due to land reclamation and development. We analysed 85 specimens (belonging to 54 species) collected by Aldrovandi in this area, clearly attributed to freshwater sites; after which we made a list of potential habitats (as defined by Directive 92/43/EEC and regional classifications of vegetation under conservation interest), on the basis of the presence of physiognomic and companion species (e.g. species generally acknowledged as frequent in target vegetation) and abundance observations from Aldrovandi’s manuscripts. The landscape shown is characterized by a complex mosaic of water bodies, riparian environments and marshes: 17 habitats have been identified, out of which 12 are recognized by the Directive; among them 3150, 3260, 3290, 7210* plus regional vegetation types Mc (Magnocaricion) and Pa (Phragmites australis thickets), which definitely existed. Many of the collected species are now either regionally extinct, critically endangered, or protected, underlining a dramatic decline in inland water plant diversity primarily driven by wetland destruction. Our study confirms the potential of using herbaria for reconstructing past landscapes, especially when different disciplines are integrated.