/ 29 May 2021

Human history on the verge of being wiped out by climate change

Indonesia Anthropology Art History
At risk: Cave art on an island in Indonesia is deteriorating. Photo: Ratno Sardi/Griffith University/AFP

Scientists have discovered that ancient cave art from the Indonesian island of southern Sulawesi is deteriorating at an alarming rate because of climate change. This area is the home to some of the oldest cave paintings discovered, some dating back from as much as 20 000 to 45 500 years ago.

The storytelling ancient mulberry paintings and red hand stencils of native animals and supernatural species are believed to have led to the areas’ modern-day religious culture and scientists are concerned that this human cultural history may soon be totally erased from the cave walls.

The Griffith Centre for Social and Cultural Research study led by archaeologist Jillian Huntley studied how climate change affects historic paintings from 11 caves in Maros-Pangkep. They’re located in the Australasian monsoon domain, the world’s most atmospherically dynamic region.

Greenhouse gas emissions from human activities are raising temperatures and magnifying climate extremes. Temperatures in the tropics are expected to rise three times faster than the global average.

At the time the earliest rock art in Maros-Pangkep was being created when climatic conditions were cooler and more humid, resulting in lower evaporation. This cool trend increased throughout the glacial period when the tropics experienced generally stable dry conditions.

The extensive shorelines of the region make it sensitive to climate change with Indonesia identified as a high-risk area in terms of drought-induced food security and extreme weather events such as tsunamis, flooding and bush fires.

“Although the Pleistocene rock art of Maros-Pangkep has existed throughout tens of thousands of years of climate variation in response to the earth’s orbital geometry, there is no doubt that global carbon cycling and greenhouse gasses are now significantly amplifying climate responses.

“And, we infer, hastening the deterioration of the unique, irreplaceable record of early human artistic culture in a little-understood region that continues to provide important insights into the culture of the first people,” reads the report.

The tropics have always been integral to the global climate system, essentially acting as a “heat engine”.  

However, the rising temperatures and seasonal rainfall in this area caused an evaporation process known as haloclasty, triggered by the growth of salt crystals due to repeated changes in temperature and humidity, caused by alternating wet and dry weather in the region.

According to the report, climate-catalysed salt efflorescence (haloclasty) or salt crystallisation is responsible for the exfoliation of the older, case-hardened limestone surfaces of Maros-Pangkep’s cave. This process is widespread among older cave surfaces in Indonesia. 

“Moreover, the exfoliation process, which destroys the rock surfaces or ‘canvases’ on which the Late Pleistocene art was created, appears to have worsened in Maros-Pangkep in recent decades — a trend we believe is set to accelerate with warming ambient temperatures and increasingly frequent and severe El Niño events,” the report says.

The successive salt crystallisation pressure results in the wall crumbling to powder and it may sometimes peel off the art panel.

“While human health and security have rightly been the research focuses, climate change equally impacts the long-term survival of physical remnants from the human past, our cultural heritage. Climate fluctuations over recent millennia and especially in recent decades have been, and are increasingly a major catalyst for the deterioration of the Pleistocene cave art in Maros-Pangkep,” reads the research in part.

Scientists reported that the research will still continue as they aim to understand what could be done to prevent industrial development from “blasting away archaeological sites” and learn how human behaviour can be improved to monitor and save heritage sites from being taken away by climate change.