Duan Xiangzheng repeatedly interrupted the interview to answer his continuously ringing cellphone.

His grave face and severe tone indicated something bad was going on.

"It must be closed immediately," he accentuated every word to the speakerphone, adding: "No matter what."

The commissioner of Nagqu Prefecture of the Tibet Autonomous Region was being told about difficulties in executing a government decision to shut down an alluvial gold mine in Xainza County.

Last year, the mine generated 5 million yuan (US$617,300) of the county's 8.5-million budgetary income.

"But we have no choice. It contaminates the water system, and causes serious soil erosion," Duan explained. "Besides, it is plagued with labour disputes."

Since 2003, environmental authorities have conducted comprehensive check-ups on 97 major mining sites in the autonomous region, among which 68 were gold mines. Altogether, 14 are undergoing rectification, 20 have received ultimatums to improve and meet environmental standards and 34 have been shut down.

The Xainza gold mine has been classified in the third category. Mining sites are not the sole target of the industrial-cleaning.

The region has closed down nine cement production lines, five small steelworks and four small papermills.

According to Wang Bin, a deputy director of Lhasa's Bureau of Environmental Protection, the city alone had shut down four ore dressing facilities, as well as 22 stone, sand and earth pits by June this year.

"It has been a game of hide-and-seek between us and illicit miners," Wang said. "After all, huge profits are particularly enticing in the industry."

As tracks of the Qinghai-Tibet Railway extend, there is an emerging urge for some local officials to exploit the region's untapped mineral resources and narrow the economic gap between Tibet and the rest of the country.

Some decision-makers, however, appear to have noticed the potential risk of such actions.

In the county of Qamdo in east Tibet, local officials cite an example to illustrate their environmental consciousness:

As early as the 1970s, a 300,000-ton arsenic mine was discovered in the county. Mining it may add millions of yuan a year to local revenues.

But it stays untouched because of concerns for potential pollution of the Lancang River as well as damage to vegetation.

"We are not compromising our environment for immediate gains," said Duan Xiangzheng of Nagqu.

Wang Bin shared his opinion that Tibet's ecological conditions are too fragile to survive blind exploitation.

Such a notion is incorporated into local legislations and government papers, and touted on the lips of local administrators.

At the core of Tibetan tradition, worship of nature, which defines the Bonpo religion, Tibet's oldest spiritual religion in existence before the import of Buddhism, has remained intact through the vicissitudes of history.

Gods and goddesses are not the only guardians of Tibet's ecological integrity.

Today, 38 government-designated natural reserves, with an aggregate area of 407,700 square kilometres, cover 34 per cent of the overall land territory of the Tibet Autonomous Region.

"No unauthorized development projects are allowed in the 230,000 square kilometres of natural reserves in Nagqu," said Duan Xiangzheng. Nagqu claims a 430,000-square-kilometre territory.

All major construction projects, including the Qinghai-Tibet Railway, are now subject to strict environmental scrutiny, according to Duan.

A 510-kilometre stretch of the 1,110-kilometre Golmud-Lhasa section of the Qinghai-Tibet Railway runs through Nagqu. At a minimum altitude of more than 4,500 metres, this section of the railway has to deal with extremely complex and fragile geological and ecological conditions.

Identified as one of the three major challenges for the ambitious project, environmental protection has enjoyed equal attention with construction efforts from the very beginning, according to officials of the prefecture's special office in charge of local assistance to railway building.

In official terms, the goal was to build an "environmentally friendly railway" that "guarantees that the layer of historical frozen earth is effectively preserved, river sources are not polluted, migration of animals is not hampered, and scenery on either side of the rail line is not damaged."

Duan shrugged off outside worries that the railway may cause irreparable environmental damage.

Instead, he takes pride in the high environmental standards in the biggest building project to be executed in Nagqu.

"We have special contracts with the building units on environmental protection," he said.

Building contractors bear full responsibility for the environmental consequences of their activities there. According to their contracts with local authorities, they have to repair and restore the environmental conditions along the railway so as to go through the latter's inspection and approval.

Along the Qinghai-Tibet Highway, there are eye-catching signs at building sites reminding people of environmental protection.

In order to facilitate vegetation restoration, workers have cut out manoeuvrable sized squares of land to transport temporarily.

In some parts along the railway, where tracks have been laid, traces of the removal and restoration are hardly noticeable.

"We have made a dozen inspection trips along the railway in our territory," said Wang Bin. "We required them to number all sod squares so as to make restoration easier."

His bureau has even dispatched a full-time environmental supervisor to the building site of the 60-kilometre highway that links the town of Damxung and the sacred lake of Namtso.

"Nationwide, there was no precedence before us in doing this," he said.

"We are also the first major city to ban plastic pollution," Wang added.

On March 25, the city published a government decree outlawing production, sale and use of non-biodegradable plastic food containers and bags, replacing them with biodegradable materials such as paper. This took effect on May 1.

Another pet project of Wang and his colleagues is the Lhalu Marsh Reserve, which was upgraded to a national nature reserve on July 23.

There are 15 wetland reserves in Lhasa's territory with a total area of 300 square kilometres.

In spite of the increase in vehicles on the streets, as well as rise in local population, Lhasa has witnessed constant improvement in environmental indices, Wang disclosed.

It has a lot to do with the city's recent efforts to harness emission and install drainage control, he said.

Compared with 2000, industrial dust release dropped by more than 70 per cent in Tibet. For the first time in history, Lhasa has had a garbage fill, and a sewage treatment plant is under construction. Similar efforts are under way at the seats of governments of all prefectures.

Additionally, in the past five decades, more than 90 million trees have been planted throughout Tibet, regional environmental authorities commented.

"So far, Tibet remains to be a place featuring the world's highest environmental qualities," the report concludes.

"The latest survey shows water and air are basically uncontaminated in our area," said Duan Xiangzheng.