The Australian and Indonesian researchers examined 11 caves and rock-shelters in the Maros-Pangkep region — which feature art dating from 45,000 至 20,000 年份 old — including the one with handprints. The scientists found that the art, which is made with red and mulberry pigments, is being physically weathered by a process known as haloclasty — when salt crystals form as a result of repeated changes in temperature and humidity.
“Salts are ubiquitous on the cave and rock-shelter surfaces in southern Sulawesi. These salts are chemically weakening the rock and mechanically separating the surface of the panels from the limestone walls and ceilings,” Huntley explained.
The authors believed this process is being caused by alternating periods of seasonal rainfall and drought that are being accelerated by the global climate crisis and El Niño weather pattens, with the tropical environment making the exceptionally old cave art particularly vulnerable.
“Climate change impacts are worse in the equatorial tropics — Australasia — because of the unique climate here. It is the most atmospherically dynamic place on Earth. 也, the tropics can experience up to three times the temperature increases under climate change compared to other parts of the world,” Huntley said.
The researchers say the caves need to have the same level of physical and chemical monitoring that has been going on for decades at famous French and Spanish prehistoric cave art sites like Lascaux and Altamira.
A small-scale monitoring program by the cultural heritage agency Balai Pelestarian Cagar Budaya has recently started in Maros-Pangkep, but more support for this initiative is required, especially infrastructure investment, 研究说.
‘Race against time’
The French and Spanish cave art sites are located in a more stable, temperate climate than the Indonesian artwork, Huntley said.
“The other difference is, those caves are very deep and the art is most often in the ‘dark zone’. In Australasia art is generally in the light zone or entrances of caves and rockshelter. There are paintings deep in caves (在) the Maros-Pangkep, but the vast majority are in the parts (indirect) light reaches,” she said in an email.
That location means that the Indonesian artwork is more vulnerable to weathering, 她解释.
The Indonesian cave art has been studied since the 1980s
, 但 it’s only in recent years it has been accurately dated
. That’s due to new techniques that can date so-called cave popcorn that forms on the cave surface
. These calcium carbonate deposits can be dated by measuring the radioactive decay of elements like uranium within them
Initially thought to be fewer than 10,000 岁, the most recent dating techniques suggested that one scene depicting three warty pigs was painted prior to 45,500 几年前 — which would make it the oldest figurative art ever found.
Adhi Agus Oktaviana, a rock art expert at Indonesia’s National Research Centre for Archaeology and a doctoral student at Griffith University, said the true extent of the region’s rock art remains unknown.
“We have recorded over 300 cave art sites in Maros-Pangkep. Our teams continue to survey the area, finding new artworks every year. Almost without exception the paintings are exfoliating and in advanced stages of decay. 我们正在与时间赛跑,” he said in a news statement.