Experts have identified 100 types of lichen on the stones of Persepolis.
They say if not treated, they are going to completely obliterate the carvings in 60 years.
The news has come as a shock to the lovers of one of the world’s most precious and iconic historical sites.
Experts say that the stones of the Persepolis provide the living conditions for a large variety of lichens which will nonetheless erode the carvings.
An expert on lichens in interview with Mehr News Agency said "The lichen growth problem is a term applied to the uncontrolled growth [of lichen] on stone monuments. In Persepolis the lichens have grown on the carvings and on the inscriptions and the lines of cuneiform, which is highly upsetting.”
Expressing sorrow over the lack of concern over the erosion threatening the world’s biggest stone monument he said "The specificity of the Persepolis has to do with the carvings, the cuneiform, the lotus, and the Achaemenid soldiers. Once these are gone the Persepolis will no longer be magnificent.”
"The lichens are one to two centimeters deep in some places,” he maintained, adding "If this goes on, the inscriptions will gradually turn into dust, which is evident in some places of the Persepolis.”
"The inscriptions in the Tachara for example have obliterated due to lichen growth. They no longer hold their old significance,” he pointed out.
While lichen’s contribution to weathering is usually benign, it can cause problems for artificial stone structures. Another famous example of the lichen growth problem is seen on Mount Rushmore National Memorial in the US that requires the employment of mountain-climbing conservators to clean the monument.