Race to save moulding Lascaux cave paintings

The French government is taking emergency action to rescue the world's most celebrated prehistoric cave paintings from a second fungal invasion in seven years.

Each day until 8 January, experts are treating the caverns at Lascaux in the Dordogne nicknamed the Sistine Chapel of pre-history with a fungicide to try to check a gradual spread of spots of grey and black mould. The caves will then be closed to all but essential visitors for three months.

An air conditioning system, installed just before a similar fungal attack seven years ago, is to be replaced. Some scientists believe the introduction of the machinery was misconceived and may be partially responsible for the fungal invasions.

Other experts blame global warming for increasing the temperature in the caves. Others point to an increased level of human activity in the caverns as part of an ambitious attempt to create an exact computerised record in three dimensions of the 17,000-year-old paintings of bison, wild cattle, deer and other animals.

Whatever the explanation, the French government has decided to take no risks and to accept the advice of a committee of experts which met at Lascaux, in south-western France, just before Christmas. The fungicide will be sprayed on the stricken areas of the cave walls. The three-dimensional survey will be halted. The air-conditioning unit will be replaced.

No public visits to Lascaux have been allowed since 1963 but almost all visits by scientists and historians will be banned for at least three months.

Officials from the French government's department of historic monuments and experts from all over the world have been quarrelling for years over the best way to preserve the paintings. Last September, the "International Committee for the Conservation of Lascaux", infuriated Paris by writing a letter to the UN cultural body, Unesco, asking for the caves to be included in the official list of world heritage sites "in peril".

The French government has minimised the scale of the new fungal attack. Officials say that the invasion is much smaller than the blankets of white fungus which spread over the walls of the caverns, and some of the painting, in 2001 and 2002. On this occasion, only small areas of pre-historic drawings have been touched and none has been damaged. Scientists fear, however, that the second attack, so soon after the first, is a warning that the micro-climate in the caverns has been permanently altered in ways which may be difficult to reverse.

The American scientist Laurence Laut- Beasley, president of the international Lascaux committee, has called for the management of the caves to be taken out of the hands of the French government and entrusted to a "higher scientific body". She accuses French authorities of "improvisation" and "lack of scientific thoroughness".

The Lascaux paintings were discovered by four teenagers in September 1940. The 600 images of bison, horses, wild cattle and ibexes, some at rest, some running or jumping, are regarded as among the finest cave paintings in the world. It is thought that they were painted between 15,000 and 17,000 years ago by hunter-gathering people who crushed minerals to create drawings in red, ochre, brown and black.