The Ajanta Caves, a world heritage site located 5km northeast of Aurangabad, are under threat because of high carbon dioxide (CO2) content resulting from increasing human interference, the Archaeological Survey of India (ASI) has said.
The ASI has conducted a five-year climate monitoring study inside the caves.
The source of CO2 in the caves is exhalation by visitors. Ajanta Caves attract 6,000-7,000 tourists a day during the peak season of October to January and about 4,000 visitors a day during the rest of the year.
The CO2 content increases by 20-30% when the caves are opened for visitors.
“It is worth mentioning that with the higher relative humidity inside the caves, there is a chance of reaction between the calcium carbonate of the white pigments and CO2, changing into biocarbonates with time, thus causing loosening of the grains,” said M Singh, head of ASI regional office in Aurangabad.
The high content of CO2 has already had an impact on the ceiling paintings inside cave No 2, where white pigments from the ceiling have come off.
“For the survival of the paintings, it is essential to introduce proper visitor management at the caves,” Singh said in a research paper to be published next week.