SAN FRANCISCO (KCBS RADIO) – For thousands of years, people in the Negev desert of southern Israel have created rock art. Fungi currently growing on the rocks now threatens to erase these works.
A study published this week in the Frontiers in Fungal Biology journal revealed that uncommon fungi and lichens are now living among the ancient petroglyphs. Researchers believe that preventing the slow, destructive work of these organisms is unlikely.
“We show that these fungi and lichens could significantly contribute to the gradual erosion and damage of the petroglyphs,” said Laura Rabbachin, a PhD student at the Academy of Fine Arts Vienna in Austria, and the study’s first author, per a press release .
To determine what fungi and lichen is living on the ancient stones, Rabbachin and her colleagues took samples from a petroglyph area in the central-western highlands of the Negev. In that area, under 3 inches of rain falls every year and rock surfaces can be around 133 degrees in the summer.
“The researchers scraped samples from desert varnish next to petroglyphs, from rocks without desert varnish, and from soil near the sampled rocks,” said the press release. “They also left petri dishes open near the rocks to capture airborne spores.”
According to the Bradshaw Foundation nonprofit organization, there are two hundred thousand rock art engravings found in the Negev desert date back at least 5,000 years. Some might be even older.
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“Negev rock art is mostly found on exposed rock outcropping and contains motifs and symbols associated with the communities that roamed and resided in region over the millennia,” said the foundation. “Located in southern Israel, the Negev desert is a semi-arid region that stretches from the Sahara in the west to Arabia in the east. Covering approximately 13,000 square kilometers, the triangular-shaped Negev extends east from Gaza on the Mediterranean coast to the southern basin of the Dead Sea.”
Hunters, shepherds, and merchants were among those who left art on the Negev rocks, said the study press release. To make them they cut into something called “desert varnish,” that consists of a thin black coating on limestone rock. This coating forms naturally.
Animals such as ibexes, goats, horses, donkeys, and domestic camels often feature in the carvings. There are also some abstract forms.
“During an emergency survey undertaken in the Negev in the late 1980s, Thamudic, Nabataean and Arabian inscriptions were located, frequently accompanied by engraved elements,” said the Bradshaw Foundation. “Despite the wealth of images and inscriptions, only a small percentage of these panels have been thoroughly documented.”
Authors of the recent study said documentation of these rocks is becoming more important than ever, in particular because of several species of fungi they found on them. These included “multiple species of fungi within the genera Alternaria , Cladosporium , and Coniosporium ,” as well as “multiple species in the genera Vermiconidia , Knufia , Phaeotheca , and Devriesia .”
After collecting the samples, Rabbachin and her team cultured them until they obtained pure isolates for DNA barcoding. Then, they performed DNA sequencing on the samples.
Most of these species (except Alternaria and Cladosporium ) are microcolonial fungi that are known to thrive in hot and cold deserts around the world and considered dangerous to stone artifacts. Lichens in the genus Flavoplaca were also found on the rocks.
“They are able to secrete different types of acids that can dissolve the limestone in which the petroglyphs are carved,” said Rabbachin of the specimens. “In addition, the fungi can penetrate and grow within the stone grains, causing an additional mechanical damage.”
Going forward, the researchers recommend monitoring these fungal communities over time and that documentation of the ancient communication continue as a way to preserve them.
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