New research has shown some of the world’s earliest known rock art is degrading at an alarming rate, and the likely suspect causing this disappearance is climate change.
Much of the world’s earliest known cave art is found in Indonesia, including the oldest known figurative artwork – you may remember the fat-bellied pig, which was global news in January – and the oldest known stencil handprints. These are under threat from aggressive weathering caused by the climate crisis, a team documenting the degradation of painted limestone cave surfaces in Sulawesi reports in Scientific Reports.
The dating of ghostly handprints and animal paintings to at least 35,000 years ago in the Sulawesi caves in 2014 re-wrote the textbooks on what we know about when and where ancient people developed an artistic inclination and what that means for human cognition. Later discoveries, like the pig and the earliest known hunting scene, which also depicts “supernatural” beings, date back even further to 44,000-45,500 years old.
Until 2014, it was thought cave art originated in the Ice Age caves of France and Spain. And yet here was evidence that humans on the other side of the world had also developed it, possibly even earlier.
Indonesia, however, is in the tropics, one of the most atmospherically dynamic places in the world, where global warming can be up to three times higher than anywhere else.
The team, led by Dr Jillian Huntley, a rock art conservation expert from the Griffith Centre for Social and Cultural Research in Australia, knew that the paintings had been deteriorating at an accelerated rate for decades, so decided to look into the mechanism causing it by analyzing 11 rock art sites in Maros-Pangkep. They analyzed flakes of rock that had detached from the cave walls and found salts including calcium sulfate and sodium chloride at three sites. These salts form crystals on the rock surface that causes it to detach. They also found high levels of sulfur at all 11 sites.
However, they were shocked at the extent of the salt weathering occurring. They recorded the loss of multiple hand-sized flakes from these art panels in just 5 months.
“I was gobsmacked by how prevalent the destructive salt crystals and their chemistry were on the rock art panels, some of which we know to be more than 40,000 years old,” Huntley said in a statement. “Our analyses show that phalloplasty is not only chemically weakening the cave surfaces, the growth of salt crystals behind ancient rock art is causing it to flake off the walls – it is disappearing before our eyes.”
Their research, carried out with the aid of both Indonesian experts and Sulawesi's cultural heritage department, revealed that repeated changes in temperature and humidity, caused by alternating seasonal rainfall and drought, were creating conditions that exacerbated the salt crystals forming and the rock paintings degrading. Though seasonal changes are normal, the team argues these changes have been accelerated by rising global temperatures and the increase in both frequency and severity of extreme weather linked to both climate change and El Niño events, which are themselves increasing in frequency due to climate change.
Mitigating the climate crisis is crucial to our planet's future, but, they argue, it's also vital in preserving our past.