YINCHUAN, March 27 (Xinhua) -- Cliff paintings in northern China that date back to prehistoric times face severe damage from natural erosion and human destruction, a Chinese archaeological expert told Xinhua on Thursday in an interview.

    About 80 percent of ancient cliff or rock paintings in Ningxia, Inner Mongolia, Xinjiang and Qinghai have sustained damage through the forces of erosion and human activity, combined with a lack of protection, according to Zhou Xinghua, an expert on cliff paintings in Ningxia Hui Autonomous Region.

    "Cracks, falling pieces and collapses have made the previously clear pictures difficult to identify and some have even completely disappeared," said Zhou, former curator of the Ningxia Hui Autonomous Regional Museum.

    The northwest region, inhabited by humans for about 30,000 years, boasts rich remains of such paintings with the most famous sites at the Helan Mountain and Damaidi.

    The eastern Helan Mountain area has 2,318 cliff paintings that contain individual figures in an area of seven square kilometers. Damaidi, located at the Weining North Mountain on the northern bank of the Yellow River, has 8,532 cliff carvings in a 15-sq-km area. The density of figures carved in the area has rarely been seen elsewhere.

    "Most of the paintings are on exposed rock mountains. They cannot be protected like cave paintings," Zhou said.

    Two cracks have emerged on a famous painting named "the God of Sun" in Helan Mountain. Pieces of stones also have fallen on the right-upper corner of the rock. A "King of Tiger" painting in Damaidi was split in half by man.

    Most of the rock paintings lack protection.

    "It is urgent to rescue the ancient paintings from complete destruction as they serve as an encyclopedia of the society, arts and folk customs of prehistoric humans," Zhou said.