The flora and vegetation of the wetlands have in part been altered and to some extent impoverished by the introduction of allochthonous species.
These species were not typical of these aquatic habitats and were often introduced after reclamation for farming and agricultural purposes.
Some of the introduced species of trees and shrubs, originally extra-European (especially from North America) do not have any important natural enemies in their new habitat.
Consequently they are spreading and causing concern as they tend to replace indigenous plant associations.
Some examples are the False Indigo (Amorpha fruticosa), which is spreading uncontrolled in the Fucecchio Marshes, the Ramone Marshlet and Lake Sibolla; the Black Locust (Robinia pseudoacacia), which is invading hygrophilous and mesophilous woodland in the Bientina Plain and the Ashleaf Maple (or Box-Elder) (Acer negundo) which is rapidly expanding on the banks and margins of the roads running through the reclamation areas.
Other allochthonous species, on the contrary, have become perfectly integrated within the wetland ecosystem and do not pose a problem of habitat colonisation or excessive competition to the autochthonous plants.
On the whole, their presence may be considered an enrichment of the biodiversity of the area. This group includes the Bald Cypress (Taxodium distichum), a large tree originally from the wetlands of Florida and Carolina.
It was introduced as a ornamental tree and its aerial roots (pneumatophores) make it unmistakable.