The persistent lichens have turned out to be a threat to the monuments of Persepolis, an ancient city in Iran built by the Persian king Darius I in the sixth century BC. Persepolis is recognized as a UNESCO World Heritage Site and is known for its huge stone sculptures of Persian rulers, deities and mythical creatures, the Phys.org portal reported, citing the Agence France-Presse (AFP) news agency.
According to Iranian scientists, lichens are slowly but inexorably destroying thousand-year-old stone structures. Without protection, the monuments will turn to dust in 50-100 years.
The spread of lichens, which dissolve minerals and penetrate rock surfaces more than 1.5 centimeters, is due to industrialization, acid rain and the harsh desert climate, the researchers said.
There are more than 3,000 species of lichens growing in Iran, of which 500-700 varieties can be found in Persepolis.
In addition to Persepolis, other monuments in Iran were damaged, such as the Bisotun Chronicle in Kermanshah province, a stone-carved text that recounts the conquests of King Darius I.
Scientists have noted that microorganisms could destroy the legacy of the ancient Persian civilization, since little money is currently allocated to protect monuments.
