The vanished Alnus-dominated forests along the Tyrrhenian coast

The development and decline of alder floodplain forests and alder carrs along the Tyrrhenian coasts, in relation to sea level changes, geomorphological processes, human activity, and climate change are presented and discussed. A number of 22 pollen records, complemented by Alnus macrofossil data, document the presence of widespread alder populations in the coastal Tyrrhenian floodplains throughout the Holocene, although with different density from one site to the other, mostly depending on local hydrological conditions. The role of climate changes in the dynamics of floodplain forests appears uncertain. In the last two centuries, major reclamation works disrupted this natural vegetation to obtain fertile plains that are now exploited for agricultural purposes, industrial activities, urban areas and related infrastructures. Only a few remnants of the original alder forests are preserved by international conservation conventions, as biodiversity reservoirs of severely endangered habitats. However, the vanished alder forests, which proved to be able to rapidly recover several times through the Holocene, may still have some potential to be restored. •Alnus was present in all Tyrrhenian coastal floodplains before reclamation works.•Human activity is the main cause for the decline of alder-dominated forests.•Remnants of the former coastal alder forests are restricted in a few protected areas.•The disappearance of Alnus swamps has produced a severe loss of biodiversity.