Seasonal rainfall, combined with increasing drought, is threatening the conservation of cave art in the Maros-Pangkep site on the island of Sulawesi, researchers led by archaeologist Jillian Huntley said in a paper published in Nature on Thursday. The area is home to the oldest known hand stencil and to possibly the earliest narrative scene in prehistoric art.
Man-made climate change is leading to more frequent and severe episodes of El Nino, a Pacific Ocean phenomenon that raises temperatures. Increasing drought and monsoon rains provide ideal conditions for salts and minerals to crystallize on the limestone caves where paintings have survived thousands of years.
Deterioration has accelerated over the past four decades as increasing greenhouse gas emissions from human activities altered the world’s climate, especially in the tropics, according to the paper, which covered the last four centuries. An increase of 1.5 to 2 degrees Celsius in global average temperatures by the end of the century-scientists’ optimistic scenario for global warming-would have grave implications for the conservation of rock art.
"In almost all sites containing early art, the hand stencils and figurative motifs are heavily affected by exfoliation of the limestone cave wall and ceiling surfaces that comprise the artists’ ‘canvas,’” the authors wrote. "A mounting body of quantitative and anecdotal evidence suggests that the rate of exfoliation is increasing.”
Crystal salts on the rocks expand and contract as the environment heats and cools, causing strain on the paintings. That pressure can generate cracks or even lift flakes, detaching them from the surface, a phenomenon that researchers call exfoliation. Deterioration is aggravated by the fact that the artworks are located in the Australasian monsoon domain, the world’s most atmospherically dynamic region.
Preserving paintings in the Maros-Pangkep site, first discovered by archeologists in the 1950s, is essential because they are one of the oldest testimonies of prehistoric art in the world. With more than 300 caves found so far and new ones unveiled every year, it rivals ice age cave art in western Europe. It constitutes a "unique and irreplaceable record of early human artistic culture in a little-understood region,” the researchers said.
Earlier paintings are mulberry and red hand stencils depicting mostly animals, while more recent art was made in black charcoal and includes small images of human figures, domesticated animals such as dogs and geometric and abstract symbols. One scene, which researchers believe is the oldest record of a hunting strategy, appears to show several human figures drawing different animals toward waiting hunters. - Bloomberg