Great Wall of the Ming Dynasty

In Weiyuan County, some parts built in the Warring States Period have been merged with surrounding cropland, while another 200-km-long section built in the Ming Dynasty in Dingxi has suffered weather damage, collapse and biological damage over a long period.

According to Zhou Youma, Deputy Secretary General of the China Great Wall Society, the Great Wall, no matter how solidly it may have been built, also had a finite lifespan.

"In line with Ming Dynasty standards, the 'quality guarantee period' of the Great Wall was 50 years. Today, even the most recently constructed sections of the Great Wall, not to mention those built in the Warring States Period, have a history of 300 to 400 years, which is why their condition is fragile," Zhou said, adding that the Great Wall is extremely vulnerable to natural erosion, the pace of which far outstrips that of restoration.

The Great Wall is a huge and complex structure and cuts across a diverse range of landscapes and climatic conditions as well. Therefore various challenges face the preservation of this famous landmark.

"The protection issues throughout different regions in China vary. For instance, natural forces, like wind, rain, frost and thawing, are the main problems for those parts of the wall built in mountains and along hills. For those parts that are close to cities and towns, human activities, such as mining, infrastructure development and profit-driven tourism, are the main causes for damage," said Wu Jia'an, a professor of archaeology at the Chinese Academy of Cultural Heritage. He added that some local residents had even taken soil or bricks from the Great Wall, and have planted crops over ruins of it.

In May, a post on Weibo.com, China's biggest micro-blogging site, revealed that a section of the Great Wall in Yulin in northwestern Shaanxi Province had been demolished for the purpose of constructing a factory on the site.

In Hebei, about 20 percent of the walls and towers can be rated "well or fairly preserved," while more than 70 percent have cracks, stand on shaky ground, or are about to collapse, provincial cultural protection officials said.

A part of the Great Wall in the province's Chongli County was even demolished by a mining company to make way for road construction.

Zhou Jinjun, Deputy Director of the Land Resources Bureau of Laiyuan County in Hebei, said that the area where the ancient walls stand in the county has rich reserves of copper, iron, and nickel. Driven by profits, small mines proliferated despite the government ban.

Last October, a section of the Great Wall in a remote area in Laiyuan collapsed because of unregulated mining activities. The area was home to a dozen small mines, with some operating as close as 100 meters to the centuries-old wall.

Villagers and local cultural relics officials said that about 700 meters of the wall built during the reign of Emperor Wanli (1573-1620) of the Ming Dynasty had already collapsed, and more walls and even towers were likely to collapse if mining continues unchecked.