Nearly 30 percent of the original Great Wall has disappeared for various reasons since it was built, including being pilfered by local residents to build houses, the government warns.A total length of 1,961 kilometers of the Great Wall has disappeared, and a further 1,185 kilometers are in bad condition, reported the Beijing Times on Sunday, citing statistics from the State Administration of Cultural Heritage.

Damage from human activities remains a great threat, because some poor local residents steal bricks from the Great Wall to build their houses or to sell, said the report.

The 8,000-kilometer-long Great Wall was built in different dynasties in history. Over 6,000 kilometers of it are spread over China's northern regions.

"Residents who live along the Great Wall used to pull down bricks to build houses and some sections of the Great Wall were destroyed during urban expansion or the building of roads," Cheng Dalin, an expert of the Great Wall research committee with the Chinese Association of Cultural Relics, told the Global Times Sunday.

The popular trend of exploring some unprotected sections of the Great Wall in recent years has brought more tourists than these sections could bear, and damaged them severely, the Beijing Times reported.

On the other hand, some places develop scenic areas for tourism or even restore parts of the Great Wall by changing its appearance to something non-historic, Cheng said.

"Natural damage, like lightning, earthquakes or floods, remains another threat to the Great Wall. Governments should take different measures considering various climate and geographic conditions," He Xinyu, a researcher specializing in the protection of the Great Wall at the Ningxia Museum, told the Global Times. 

"Surveys about the state of the Great Wall built in the Ming Dynasty (1368-1644) showed that there are few problems to protect the Great Wall in theory. But in reality, it requires local authorities to strengthen enforcement of related laws and regulations," Cheng said.

China promulgated regulations on Great Wall protection in September 2006, which stipulated that people who take bricks from the Great Wall can be fined up to 5,000 yuan ($805).

"But there is no specific organization to enforce the rules. Damage could only be reported to higher authorities and it is hard to solve when it happened on the border of two provinces," said Jia Hailin, director of the cultural relics protection department at the Jinshanling Great Wall scenic area in Hebei Province.

Shortages of resources for enforcement are another problem, said Cheng.