URUMQI: Facing the continuous invasion of the Taklimakan, the world's second largest desert, people in Northwest China's Xinjiang Uygur Autonomous Region are trying to fence in the encroaching desert with trees.

Yin Chuanjie, an official with the Regional Forestry Bureau of Xinjiang, said more than 1,000 green walls are encircling the triangle-shaped desert at the northern, western and southern edges like a huge scarf, holding back the "sand dragon" from further migration.

Located in what is now the Xinjiang Uygur Autonomous Region, the sea of sand that is the Taklimakan Desert was once regarded as almost impassable by merchants travelling through the area.

With an area of 340,000 square kilometres, the desert is as large as Britain, Ireland and Holland combined.

Though the area was home to numerous flourishing civilizations in history, few survived the intrusion of the desert.

As the capital of the ancient Jingjue Kingdom, Minfeng County, once called Niya, on the southern edge of the desert was once swallowed by the desert like Loulan, or Kroraina, an ancient civilization on the eastern tip of Taklimakan, whose collapse remains a mystery to historians.

Even in modern times, the county seat was forced to move three times to escape the invasion of the desert.

Realizing the seriousness of the problem, China launched a planting programme covering its north, northeast and northwest in 1978. Since then, the central government and the regional government of Xinjiang have invested some 10 billion yuan (US$1.2 billion) to curb the expansion of the Taklimakan Desert.

Over the past two decades, more than 860,000 hectares of trees have been planted in the desert area, which, if arrayed into a 1-metre wide belt, could surround the equator of the earth in three loops, Yin said.

Thanks to the green belts, local people are enjoying better weather. Statistics from the regional meteorological authorities showed that sandstorm days every year declined to 11 from 22 in 1978 and dusty days dropped from 66 to 30.

Only drought tolerant tree breeds like sacsaouls, purple willows and narrow-leaved oleasters can survive the arid environment.

Because of atrocious weather conditions, young trees require special care, said Yin.

It is estimated by regional forestry workers that the cost for a hectare of trees averages a minimum of 13,500 yuan (US$1,600), equal to a year's income for about 10 local people at the southern end of the desert.