Sentinels that monitor air quality and purify it of heavy metals are lichens, symbiotic organisms composed of at least two different partners that benefit from each other, in this case a fungus and an alga. In the Botanical Garden of the University of Pisa, just a stone’s throw from the Leaning Tower, a team of researchers from the University of Pisa found an unusual concentration of these organisms, up to 57 ‘epiphytic’ lichens, i.e. lichens that grow on the bark of trees, and a non-lichenised fungus. Among them there are rare and endangered species, some of which were found for the first time in Tuscany, while the widespread presence of nitrogen-tolerant lichens is probably linked to urban environmental conditions.
The study by the University of Pisa, in collaboration with the Slovak Academy of Sciences, published in the journal Italian Botanist, is the result of a three-year degree thesis in Natural and Environmental Sciences written by the student Giorgia Spagli, under the supervision of Professors Luca Paoli and Lorenzo Peruzzi, botanists of the Department of Biology, in collaboration with Marco D’Antraccoli and Francesco Roma-Marzio, Curator of the Botanical Garden and the Herbarium of the Botanical Museum, respectively.
Ginkgo biloba at the Botanic Garden of the University of Pisa
“A recent study estimated that in protected areas in Italy there are about 59 species of epiphytic lichens per 1 km², whereas in our case, in an urban context and in an area of only 0.02 km², there are 57,” says Peruzzi. “Botanical gardens in urban centres are in fact green islands that offer shelter to various animals and plants, including lichens, which appear spontaneously thanks to the diversity of microhabitats present and the richness of tree species”.
“Lichens are among the first colonisers of habitats even if they often go unnoticed,” continues Paoli, “and yet the role they play is very important: they are organisms that can be used, among other things, as biomonitors, a cheap solution that can complement traditional monitoring stations to assess air quality and ecosystems in general”.
In particular, among the species found, Arthopyrenia platypyrenia and Coenogonium tavaresianum are new reports for Tuscany. Arthopyrenia platypyrenia is a very small non-lichenised fungus, little known and rarely reported in Europe. In Italy, this species was previously found only in Calabria. In the Botanical Garden it grows on the bark of a specimen of Pittosporum (Pittosporum tobira). Coenogonium tavaresianum, typically found in the humid forests of the Tyrrhenian coast, is an endangered species, but in the Botanical Garden it grows abundantly on the bark of a specimen of California cedar (Calocedrus decurrens). Lecania cyrtellina, finally, is only recorded in the Botanical Garden for the area of Tuscany, where it grows on the bark of an old Chilean palm specimen (Jubaea chilensis).