The only man-made structure that can be seen from space may not be visible to the eye even from the ground if the present state of affairs continues.

The Great Wall by all accounts is 6,300-km long. But 90 percent of this architectural and engineering marvel is under threat of disappearing, says a leading Great Wall protection expert.

"Only 10 percent of the existing wall is under protection," said Dong Yaohui, vice-chairman of the China Great Wall Society, an NGO championing restoration.

The society's 2006 figures showed that only about 20 percent of the Great Wall is in reasonable shape, another 30 percent is in ruins. Which means almost half of it has disappeared.

Only some sections of the Great Wall are listed as conservation sites, but its major portions, especially those in rural areas, have escaped attention, he said.

Unfortunately, what remains of the wall is "in danger of collapse" too, thanks to the weather, erosion and human activities, he said.

The Regulation on the Protection of Great Wall, the country's first statute to protect the "national symbol" from further damage, has done little, even though it was implemented last December, Dong said.

The regulation stipulates as illegal activities holding of events in sections of the Great Wall not open to tourists, carving names, digging the soil, taking out bricks or planting trees along the wall.

But "with no local budget allocated and shortage of hands in the State Cultural Relics Bureau, the regulation could be a mere paper, with no force," said Dong.

The country is likely to come up with a new protection plan in 2009, though, he said. And it is widely expected to ensure more all-around protection.

Dong urged the entire society to contribute to the cause of Great Wall protection.

The man who walked the entire stretch of the Great Wall between 1984 and 1985 is 50 today, and has spent more than two decades studying and protecting the wall.

He is ready to offer consultation on renovation and development projects, he said, because "commercial renovation has become an irresistible trend".

Renovation efforts that don't conform to scientific and professional standards often do more harm than good, he said, citing the Shahukou section in Youyu County in North China's Shanxi Province as an example.