Fu, 66, a retired civil servant who is fascinated with the Great Wall, decided to walk the 100-kilometer stretch of the Great Wall located in Fugu County, northwest China's Shaanxi Province, starting in 2010.

With just a crutch and a backpack, Fu has walked back and forth along the section of the Great Wall several times to record wear and tear on watchtowers and fortresses, as well as other natural and man-made damage.

"I don't have any other thoughts, but I just want to leave some research materials for later generations," Fu said.

The Fugu section of the Great Wall was built during the Ming Dynasty (1368-1644) and has endured years of weathering and erosion.

In 2010, Fu was the first person to count all 196 watchtowers along the 100-km stretch of wall. The watchtowers are all in extremely poor condition, with some barely even visible.

"The statistics collected by Fu are of great importance for the protection of the Great Wall," said Tan Yushan, the head of the county's culture bureau.

The walls, horse tracks, watchtowers and fortresses that make up the Great Wall span 15 provincial-level regions from west to east, including Qinghai, Shaanxi, Inner Mongolia and Beijing.

"The Fugu section of the Great Wall is not as imposing as the Badaling or Juyongguan Great Wall on the outskirts of Beijing, but they are precious possessions our ancestors left for us," Fu said, adding that they should be better protected, not left to be destroyed.

As a whole, the Great Wall was built continuously from the 3rd century B.C. to the 17th century A.D. as a major military defense project spanning different dynasties.

It was listed as a World Heritage Site by UNESCO in 1987.

About 21,196 km of wall currently remains, according to survey results released by the State Administration of Cultural Heritage in 2012.

However, some sections of the Great Wall across the country's arid northwest have been nearly flattened by sandstorms, strong winds, torrential rains and human activities.

"Some people tore down the walls of the Great Wall to make way for road repair projects, and some even took the bricks from the Great Wall to build personal homes," Tan said.

Though county authorities have set up a special Great Wall protection team of seven volunteers to report even minor damage since 2005, staff shortages and insufficient funds have impeded the protection work, Tan said.

"The Great Wall built in the Ming Dynasty will probably disappear without proper restoration," said Zhang Yan, an official with the Shaanxi Provincial Academy of Social Sciences.

According to a provincial plan to protect ancient Great Wall structures, the province will erect protection signs and recruit surveillance staff from local villages along the wall by the end of 2015.

"Modern technologies should be employed in order to showcase the integrity of the Great Wall," Zhang said.