ABSTRACT
The industrial development that started during the second part of the 19th century was accompanied by harmful phenomena such as noise, smoke, and soot. The effect of urban pollution on lichens has, in fact, been demonstrated at every place where research has been undertaken. The effect does not always cause a complete disappearance of the epiphytic lichens. The zonation of urban centers has not been considered by all authors to be due to pollutants. Some authors attributed zonation to changes in climatic conditions such as temperature, and mainly to a decrease in the relative air humidity, a theory known as the “drought hypothesis”. The ability of lichens to accumulate high levels of sulfur has been demonstrated in many investigations. Absorption and accumulation of heavy metals from the environment are well-documented features of lichens and have been used to monitor atmospheric depositions of a large number of metals.
