Risks to major rock art site debated

Controversial studies say the world's largest rock art collection is not at risk from industry or weathering.

THE WORLD'S LARGEST COLLECTION of rock art is found at the Burrup Peninsula in the Pilbara region of Western Australia. Two new studies argue that it may not be as much at risk from weathering or industry as some experts had feared, but not everyone agrees with the findings.

Nearly one million engravings are thought to be carved into the hard rock surfaces at many different sites across the peninsula and the Dampier Archipelago of islands. The peninsula itself was the largest of these islands until industrial activity joined it to the mainland in the 1960s.

The engravings, called petroglyphs, depict animals such as kangaroos, birds, fish and reptiles as well as human figures and faces and geometrical patterns, and may be more than 10,000 years old. There are also more than 2,500 archaeological sites in the region including quarries and campsites, according to the World Monument Fund.   

Remarkable resistance

Two separate studies presented last week at the Australian Earth Science Convention in Canberra, now suggest that the engravings are remarkably resistant to both natural erosion and the effects of nearby heavy industry, including an iron ore terminal, liquefied natural gas plant and ammonia fertiliser plant.

"So far we have seen no change whatsoever," says Dr Erick Ramanaidou, a CSIRO earth scientist and leader of a five-year study on the effects of industry. The team from CSIRO and Murdoch University, in Perth, studied colour changes in the rock using a variety of scientific equipment and also tested the mineral and chemical composition of eight different rock art sites.

The levels of emissions of air pollutants in the area were low and did not appear to be affecting the rock art, Erick told Australian Geographic. "This is a very clean place even with the industry."

However Robert Bednarik, President of the International Federation of Rock Art Organisations disagrees with the new findings and says that his own studies of the colour of the rocks show that damage is occurring. He says that emissions from nearby industry increase acidity in the atmosphere causing acid rain, which is damaging the iron oxide coating through which the petroglyphs were carved.

Findings are "optimistic"

"Any acidic precipitation tends to destroy iron deposits," he says. "My view is that the acidity [on the rocks] is [similar to] lemon juice. To expect iron coatings to survive that for a long time is optimistic."

A second study, partly funded by Woodside Energy, which operates a gas plant in the area, measured the long-term rate of natural surface erosion. The study's lead author, geologist Brad Pillans, from the Australian National University in Canberra, says erosion rates of the rocks were typically significantly less than one millimetre every 1000 years, among the lowest in the world.

"If you are going to look at human impact you need to know the baseline," he told Australian Geographic. "The bottom line is we have good baseline data on the long-term natural erosion rate of the rocks."

Robert described this as "balderdash", adding that the longevity of "the rock art depends entirely on the survival of the iron coating."

Ken Mulvaney, an archaeologist who works for Rio Tinto and who has studied the area, says that one of the reasons there is so much rock art is because of the low natural weathering rate of the rock. "As recognised through the National Listing, the area is of immense cultural and scientific value," he says.

LINKS
Read more about the rock art at the World Monument Fund's site