Officials with the local afforestration bureau said the move is to improve its ecological conditions, thus striving to realize sustainable development.

The region, also called "world roof" due to its high average sea level of 4,000 meters, features freezing cold and a low proportion of oxygen in the air. The harsh geological conditions and climate resulted in a limited amount of green coverage rate in the region.

Helicopters will sow the seeds of shrubs, grass, and arbors in an area of 1,333 hectares first as an experiment.

Officials said the highest sea level for air-sowing would be around 3,800 meters. Due to lack of records and experience on air-sowing in regions with such a high sea level, pilots will go to Tibet soon for a test flight.

The local afforestration bureau has started using the method in the areas around Nyangqu River, Yarlung Zangbo River and Lhasa River since 1996.

(Xinhua 03/19/2001)