For the second time in a decade, fungus is threatening France's most celebrated prehistoric paintings, the mysterious animal images that line the Lascaux cave in the Dordogne region of southwest France, scientists say. No consensus has emerged among experts over whether the invading patches of gray and black mold are the result of climate change, a defective temperature control system, the light used by researchers or the carbon dioxide exhaled by visitors. But after inspection by a team of microbiologists, the government has approved a new treatment of the blemishes with a fungicide and ordered that the cave be sealed off for as long as four months so that its delicate environment can be stabilized.
     The Lascaux paintings, with their astonishing array of animals, are thought to be 15,000 to 17,000 years old. The early Europeans who roamed this region used crushed minerals to create some 600 images in red, ochre, deep brown and black, some so powerful and vivid that they are considered among the finest examples of Paleolithic cave art.
Since the paintings were discovered in 1940, however, their preservation has been a constant headache, with government officials in Paris and the local authorities criticized for failing to ensure their proper protection. By the late 1950s, the visitors' breath was blamed for the appearance of lichen and small crystals on the walls, prompting the government to close Lascaux to the public in 1963. Since then, only five people per day, five days a week, have been allowed to visit the underground gallery by special permission, and tourists are steered into a replica of the cave complex nearby. The replica, known as Lascaux II, opened in 1983 and now draws more than 250,000 tourists each year.
     In the real cave, new problems arose in 2001, when officials in charge of Lascaux decided to modernize the system regulating the temperature and humidity. Soon after this work was completed, a white mold began spreading rapidly across the cave ceiling and walls. At first, the blame fell on the new air-conditioning unit and the clothing of the workers who installed it. Later studies suggested that the fungus was probably already in the cave, although it might have been awakened by the movement of workers and a related rise in humidity. Some experts have pointed to climate change as a factor.
     Whatever the reason for the problems at Lascaux, the white mold outbreak in 2001 led the government to close it to all nonessential visitors. It was so serious that, to stop the invasion, the floor was covered with quicklime and scientists began treating the problem chemically, said Marc Gauthier, president of the International Scientific Committee for Lascaux, which was created as a result of the crisis. The new problem at Lascaux, however, does not appear to be linked to the fungus. Described by experts as black stains, the blemishes are in fact both gray and black and most are found in the passages where the rocks are most porous and paintings had faded the most long before modern man entered. While only a few stains have affected the paintings, they have now been found in some 70 different spots.
     Last year, The International Committee for Preservation of Lascaux warned of the rapid spread of black spots, which are now appearing where the traces of the fusarium fungus had been removed by scalpels. Two weeks ago, the International Scientific Committee for Lascaux decided to try new methods. "Every treatment we have applied had its own side-effects," said Anne Marie Sire, the curator responsible for interventions in French caves. "We cannot touch the figures with scalpels or chemicals, so now we will try to diffuse a treatment in the air."
     Since this summer, the stains have darkened and expanded, although they are still in a limited area, and this shows that Lascaux suffers from an illness that must be constantly treated. What appears clear is that the discovery of Lascaux 67 years ago disrupted an ecological balance that had helped preserve the paintings for thousands of years. And Lascaux’s continuous problems have served as warnings for other sites that bear prehistoric art in central and southern France. Some painted caves allow limited numbers of visitors, and others, on privately owned land, are open by invitation only.

Source: The New York Times (9 December 2007)