The ancient irrigation system of the Palermo Plain (Sicily, Italy) as a substitute ecosystem: preliminary investigations on its aquatic flora

Many cities around the world are expanding, including in their perimeters green and blues spaces that could be crucial for the maintaining of biodiversity. Urban waterbodies are generally created to provide other services, but correctly managed they can provide also relevant ecosystem services. The Palermo Plain was characterized, in the past centuries, by several wetlands that were progressively destroyed (or “reclaimed”). The ancient irrigation system, probably set during the Arab domination (IX-XI century A.D.), became a substitute ecosystem able to host a significant biodiversity. Our research focused on the remains of this system, scattered in the relictual green areas of the Plain, and especially on typical open cisterns, named (with a term of Arabic origin) “gebbie”; we checked the presence of strictly aquatic flora (vascular plants and charophytes), taking also into account some water parameters (conductivity, pH and hydroperiod) and the type of management of these water bodies. The floristic richness of these urban reservoirs appears to be generally low; however, they sometimes support rare species, or species otherwise disappeared from the Plain. If well managed, they have the potential to support a much greater biodiversity than they currently do; on the contary, abandoned “gebbie” are the poorest ones.