Ancient rock art in this region is being threatened by global warming

This rock painting found in a cave on the island of Sulawesi, Indonesia, is the oldest known in the world. It represents a wild boar and dates from at least 45,500 years ago. Photo: AFP

Climate change is a major issue affecting many domains, and while it may not be the first thing that comes to mind, rock art specialists are particularly concerned.

A new study reveals that some of the oldest rock art sites are threatened with extinction due to global warming, especially in South-East Asia. Researchers based in Australia and Indonesia looked at the island of Sulawesi, which has numerous rock paintings, including a figurative Sulawesi boar fresco dating back at least 45,500 years.

The region in which this Indonesian island is located is the most dynamic on the planet in terms of atmosphere, which makes it particularly sensitive to climate change. A situation that worries archaeologists, as evidenced by a study recently published in the scientific journal Nature.

Salt, heat and extreme weather events such as El Niño contribute to the degradation of archaeological sites in Sulawesi. Alternating phases of drought and heavy rains during the monsoon season cause an accumulation of salts on the surfaces of the caves in the Indonesian region, which contributes to the exfoliation of the rock surfaces.

"Salt efflorescence is the growth of salt crystals deposited by saline solution, also known as haloclasty or salt crystallisation. When the solution evaporates, crystals form, expand, and contract as the environment heats and cools, causing repetitive strain," the researchers explain.

Caves yet to be explored

This salt crystallisation damages the limestone surfaces inside the caves, creating cracks in the rock surface and causing the rock art to flake off.

Local communities that have watched over these archaeological sites for generations have noted that the phenomenon has accelerated more in recent decades "with more panel loss from exfoliation over recent decades than at any other time in living memory."

As the researchers explain, the climate crisis is "hastening the deterioration of the unique, irreplaceable record of early human artistic culture in a little-understood region, one that continues to provide important insights into the culture of the first peoples of the Indonesian Maritime Continent."

The urgency is all the more felt as new rock art sites are discovered every year in Sulawesi, and some caves have not yet been explored. - AFP