Wang Yuwen, a retired worker who lives in Beijing's northern suburbs, noticed the usually azure skyline was slightly turning sandy on the morning of March 3. Soon he saw a veil of fine sand grains falling. "Spring is coming," he murmured.

Decades of living in Beijing has proved ample time for Wang to familiarize himself with the springtime scene. In fact, dusty winds have become one of the symbols of Beijing's spring, so much so that Beijing natives like Wang did not take the season's first sandy scene too seriously.

"I thought there might be a couple of such cases later in the spring and then the winds would get weaker and cease before rain falls, like before," Wang said.

But he was wrong.

In the following month, he and other Beijingers witnessed weather Wang had never seen in his 67 years of life.

Since their onset in early March, dust-laden winds from the depth of the drought-stricken Mongolian Plateau and loess land swept through Beijing a record nine times.

Among them, the strongest brought sandstorms to Beijing and then headed south to Shanghai and Nanjing, though changing into muddy rains there.

On the morning of April 6, the sixth and most serious sandstorms of the season hit Beijing, forcing sands 10 times that of the normal standards to toss about in the sky, according to the municipal meteorological bureau.

And Beijing was not alone in the sandstorm attack.

Experts have put this spring's dozen storms in Northwest and North China as the most widely affecting, and possibly most serious, in 50 years.

So far, more than 20 major cities in China have come under attack of the dusty winds in the last two months.

The latest round of sandstorms swept the Ningxia Hui Autonomous Region and Shaanxi Province, around China's largest loess land, last Thursday.

Local media reported that the visibility had been obscured by the sandy skies to less than 100 metres during the middle of the day.

This is the 10th sandstorm in Ningxia this year, according to local media.

The Inner Mongolia Autonomous Region bears the brunt of the season's sandstorms and was one of the most seriously hit areas.

The sandstorms there came in March, nearly one month earlier than usual.

In less than one month since March, seven large-scale sandstorms swept across most of the 1.1-million-square-kilometre region, adding to the snow disasters the area had already endured.

In the region's Alxa Prefecture, the most serious sandstorm so far this spring occurred on March 26, bringing about a record floating dust density of 74.9 grams per cubic metre air, almost 760 times the average observation rate, according to local observatory.

The sandstorm-prone areas also expanded from the west to the east, showing an growing tendency of sandstorms occurring.

When residents of Inner Mongolia were ready to breathe a sigh of relief after the strong dusty winds seemingly drew to a close near the end of April, a new round of sandstorms arose in the west of the region last week and forced its way southeast across Inner Mongolia.

"This sandstorm arose in the similar areas to most of the previous ones but was less severe," an observer with the region's meteorological bureau told China Daily.

But the observer, without identifying himself, admitted that it added to the disaster of the entire autonomous region.

This time, Beijing was fortunate enough to avert the attack as the storms stayed north of the capital. "The rainfall before its arrival also headed off the sandstorms," explained an employee with the Beijing Meteorological Observatory.

The worker, who was surnamed Li and identified himself as the observatory's chief technician, compared this years's dusty winds attacks to those of 1988.

"We had a similar scene that year, but the sand back then was not as much as this time," he said.

The observatory, as well as other weather monitoring agencies in northern China, has kept a close watch of the rampant dusty winds and the weather changes in the past two months.

The origins of most of the sandstorms have been identified as the deserts in the Republic of Mongolia and those in China's northwestern Xinjiang Uygur Autonomous Region and Inner Mongolia.

Li said observations have revealed that all but one of the nine dusty storms that attacked Beijing carried sands from another location.

"Most of the sands came from the north," he said.

Observations by meteorologists from Inner Mongolia also pointed the sand origin of most of the sandstorm to the 300,000-square-kilometre wide area of dry land in Alxa in western Inner Mongolia, where decades of overgrazing and land claiming have nearly depleted the vegetation.

Who is to blame?

People's complaints about the frequent sandstorms were soon directed to the destruction of the ecosystem in northern China as the storms continued.

Human destruction of the vegetation in the sandstorm origins were uncovered by media and conveyed to an astonished public.

Yet scientists, especially meteorologists, tend to stress that abnormal weather helped aggravate this year's sandstorms.

Ding Yihui, a research fellow with the National Meteorological Centre, said volatile weather conditions this spring are also culprits to blame for this year's sandstorms.

The unusually rapid rise of temperature since this past March sped up the thawing period in northern China.

"In some regions, the speed of temperature increase is the highest in 40 years, which speeds up the thawing of frozen soil," said Ding.

And this, he said, made the soil unusually loose and more prone to erosion.

Meanwhile, there was little precipitation this spring and there has been no rainfall before each of the dust storms. "That makes the loose soil directly exposed to the wind, without any deterrent," he said.

Unusually frequent, strong cold fronts from the north turned out to be a major cause of the storms, Ding said.

Li, from the Beijing observatory, also echoed Ding, saying that abnormal weather conditions were the key to the sandstorms. "People talked about the desertification and ecological degradation, but as far as this season's sandstorm attacks are concerned, I'd say that weather also played a role." Li said.

Despite explanations from weather forecasters, experts from other fields stressed that the ecological degradation sparked the sandstorms.

Liu Tuo, an expert from the Anti-desertification Division under the State Forestry Administration, argued that this year's wide sandstorms were the result of incremental ecological destruction.

Increasing population pressure in the former grasslands in northern China led to inevitable desertification, he said.

For example, in Alxa, one of the major sand origins, the population density has more than doubled the normal standards the dry land can tolerate. In some regions, the level has tripled, according to administration statistics.

The major river running through Alxa, the Black River, has seen its annual run-off shrink from 1.1 billion cubic metres five decades ago to less than 300 million today. More than 400,000 hectares of land have turned into desert while 10 per cent of the vegetation there have fallen victim to drought.

Unfettered land claiming, which still goes on in the region, detracted the already shrinking run-off.

In Inner Mongolia, overgrazing diminished the natural prairie by at least 30 per cent during the past 50 years, while livestock in the region doubled in only two decades.

Statistics from the State Forestry Administration also indicated that an average of 2,460 square kilometres of land turns into desert annually in China.

"All these have provided the necessary conditions for strong winds," said Liu.

China initiated a large-scale afforestation project in northern China in the 1980s and intended to build a green "Great Wall" across northern China to stave off the sandstorm attacks.

But inefficient afforestation and human destruction have caused the project's fruits to be less than stellar.

"For now, the project has not be able to prevent Beijing from suffering sandstorms hailing from the north," said Luo Bing, another expert with the Anti-desertification Division.

The problem also drew great concern from the central government. During his inspection trip over the weekend to Hebei Province and the Inner Mongolia Autonomous Region, Premier Zhu Rongji called for immediate and efficient efforts to combat serious desertification in the country and to build green belts to improve ecological environment.

The State Forestry Administration is now mulling a new anti-desertification control plan.

Based on the plan, intensive and comprehensive efforts will be made so that sand origins that are relatively less threatening in the country will be fastened by 2010.

And by 2030, the overall sand invasion of the country will be contained.

(China Daily)