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07-07-2024

Ancient desert rock carvings face erosion from fungi and lichens

In the southern fringes of Israel, the arid plains of the Negev Desert cradle a precious cache of history. For millennia, the region’s roving hunters, shepherds, and traders carved their stories on the rock canvases of this desert.

Their work, ancient petroglyphs, carved meticulously on a thin, naturally formed black coating known as ‘desert varnish,’ is a remarkable sight.

Among these enduring illustrations, representations of ibexes, goats, horses, donkeys, and domestic camels are common. They’re not alone, though; abstract symbols and figures also make appearances.

However, a recent study featured in reveals an invisible threat to these invaluable artifacts: desert-adapted fungi and lichens.

Fungi and lichens on rock carvings

The author of the study is Laura Rabbachin, a PhD student at the Academy of Fine Arts Vienna in Austria.

“These fungi and lichens could significantly contribute to the gradual erosion and damage of the petroglyphs,” warns Rabbachin.

“They are able to secrete different types of acids that can dissolve the limestone in which the petroglyphs are carved. In addition, the fungi can penetrate and grow within the stone grains, causing additional mechanical damage.”

Rabbachin and her team embarked on a field trip to the central-western highlands of the Negev Desert, where the climate is as harsh as it gets.

Here, annual rainfall barely crosses 87mm (3.4 inches), and rock surfaces can reach a sweltering 56.3 °C (133.3 °F) in summer.

Fungi impact the rock carvings

For their research, the team took various samples from rocks bearing petroglyphs, unadorned rocks, and surrounding soil.

They also collected airborne spores, casting a wide net in their quest to understand the nature and diversity of the fungi and lichen species involved.

Negev petroglyph rock carvings are eroding from fungi and lichen. Credit: Laura Rabbachin
Negev petroglyph rock carvings are eroding from fungi and lichen. Credit: Laura Rabbachin

Their research revealed that only a few species can survive in extreme conditions. They found several fungi on the rock carvings, specifically from the genera Alternaria, Cladosporium, and Coniosporium.

These fungi are known for their resilience and ability to thrive in harsh environments.

Lichens deterioration of the carvings

Additionally, they identified various lichens from the genus Flavoplaca. Lichens are symbiotic organisms composed of fungi and algae or cyanobacteria, which allows them to survive in conditions that are too extreme for most other organisms.

This combination of fungi and lichens illustrates a diverse but limited group of species capable of enduring such challenging environments.

Rabbachin’s study noted that the greatest threat to the rock carvings comes from a group known as microcolonial fungi.

“Microcolonial fungi are considered highly dangerous for stone artifacts. They have been implicated as a probable cause of the deterioration of stone cultural heritage in the Mediterranean,” she reported.

Is there a remedy?

The sobering conclusion from the research team is that halting these natural weathering processes is unlikely. “Their speed of the weathering process depends heavily on whether and how the climate will change in the future,” says Prof Katja Sterflinger, the study’s senior author.

Instead, the team suggests a different approach. Document these valuable works of art in detail, including their materials, techniques, and historical significance. Monitor the microbial communities over time to understand their impact and evolution.

Conservation strategies and future directions

While eradicating the fungi and lichens is not feasible, there are strategies that can be implemented to slow down their damaging effects.

Conservationists are exploring the use of biocides that are effective against these microorganisms but safe for the environment and the artifacts.

Another approach involves environmental management, such as controlling the microclimate around the rock carvings to make it less conducive for fungi and lichen growth.

These methods require ongoing research and funding, but they offer a potential way to mitigate the impact of these natural processes.

Looking ahead, a multi-disciplinary approach involving mycologists, archaeologists, and conservation scientists will be crucial in developing sustainable strategies to protect these irreplaceable cultural treasures.

This tale of the Negev Desert’s rock carvings is a humbling reminder of our tenuous hold on the past. Our ancestors’ stories, lovingly carved on stone, might be wearing away under nature’s relentless forces. Yet, we can still preserve their memory in our shared histories and narratives.

The study has been published in the journal Frontiers in Fungal Biology.

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