BERLIN, Nov 4 (Reuters) - UNESCO has awarded a German firm contract to preserve the world-famous but decaying Moai head sculptures on Easter Island, which are suffering the effects of the weather, tourism and past restoration attempts.

Stefan Maar, founder of Berlin-based Maar Denkmalpflege GmbH said on Tuesday his company planned to begin treating the statues with chemicals in early 2005 in a project estimated to cost about 10 million euros ($11.5 million).

"Something has to be done," Maar told Reuters. "But with over 1,000 figures, it is a really big undertaking."

Maar's scientists are developing a chemical treatment for the unique volcanic tuff stone from which the heads are carved.

"The stone is not like anything else," Maar said.

The Moai statues are between 400 and 1000 years old and average 13 ft (4 metres) in height, weighing up to 82 tonnes.

The chemicals should prevent moisture passing through the stone and stabilise it, stopping the growth of large cracks now forming rapidly, said Maar, who gained experience in preserving historic monuments on German projects.

"After the fall of the Berlin Wall, there was money to research preservation techniques for monuments that the German Democratic Republic had not restored," he said.

Also known as Rapa Nui, the 166 sq mile (430 sq km) Chilean-governed Easter Island is isolated from other land masses by thousands of miles of South Pacific Ocean.

The ancient Rapanui people, who sailed to the island either from Polynesia or South America, carved the heads and hauled them to the island's beaches. How they moved the massive statues with human power alone is one of archaeology's great mysteries.