CHINA:Sandstorms in northern China, getting worse every year as creeping deserts blight the land, are reducing large sections of the Great Wall of China to piles of rubble. Archeologists say entire chunks of the wall could be gone in 20 years, swallowed up by the Badain Jaran desert.
More than 20 centuries old, the Great Wall of China once stretched 6,400km (4,000 miles) through China, from the Shanhaiguan Pass in the northeastern province of Hebei to the Jiayuguan Pass in the northwestern province of Gansu. The wall was originally built to defend China against invasion by northern nomadic tribes.
About 500km from the Jiayuguan Pass lies Minqin county, where more than 60km of the wall is disappearing rapidly, a victim of extensive farming since the 1950s, which has sapped underground water and destroyed the local ecology.
"This section of the Great Wall was made of mud rather than brick and stone, so is more prone to erosion," Zhou Shengrui, former curator of the local museum, said.
"Similar erosion happened to the Great Wall in other places, but the situation is much more worse here. Frequent storms not only eroded the mud, but also cracked the wall and caused it to collapse or break down."
This historic section of the great defensive structure was built during the Han dynasty, which lasted from 206 BC to AD 220, and was extended during the Ming dynasty (1368-1644).
More than 40km of wall in Minqin have disappeared in the past 20 years. The wall is just two metres tall in places, where once it stood five metres high, and many watchtowers have been lost to the sands.
Since the 1960s, the area has become increasingly parched. The 400sq km, 60m-deep Qingtu lake has dried up in the past 30 years, and in the last decade the area has been swallowed up by the sand of the Badain Jaran.
The world's fourth-largest desert, the Badain Jaran spans more than 40,000sq km and covers large sections of Gansu and Mongolia. The desert is home to some of the world's tallest stationary dunes, which stand 500m tall, and it is a major source of sandstorms in China.
Local residents describe how the Great Wall gets shorter every year. "When I was seven or eight years old, the section of Great Wall about 1,000 metres west of my village was still as new. We used to walk on it like the ancient soldiers," said Wei Zhaobai (61), a resident of Chengxi village in Minqin.
In a bid to fend off the encroaching desert, local workers were covering the wall remains with more sand and dirt.
"If sandstorms strike again, it will take some time to blow the top-dirt away, and that'll give us time to build barriers and plant trees," said Mr Zhou.
Chosen last month as top of the new seven wonders of the world, the Great Wall of China has an estimated 10 million visitors a year. But these days, China's national symbol is in a sorry state, with only about 2,500km of the wall left standing.
"As a relics protector, it saddens me to see the Great Wall being blown away, but we hope it can be a warning of what we have done to ourselves and our environment," said Mr Zhou.