Encroaching deserts threaten life along Tibet's longest river
February 22, 2012
alertnet / Teresa Rehman
By Teresa Rehman
Yang Yong said he had observed desertification in parts of the upper reaches of the Yarlung Zangbo River, and believes this could be caused by climate change as well as human activity.
The Yarlung Zangbo (also called the Yarlung Tsangpo) is Tibet’s largest river, originating in the west of the region. Along its 2,057 km (1,286 mile) length, it passes through India, where it is known as the Dihang and the Brahmaputra, and Bangladesh, where it is called the Jamuna.
The United Nations Environment Programme says that desertification - land degradation in arid, semi-arid and dry sub-humid areas, caused by climatic variations and human activities - affects a quarter of the world’s total land area and one-sixth of its population, and is a major factor in widespread poverty.
Yang, who has explored western Tibet three times since his first visit in 1998, has seen that firsthand in the upper reaches of the Yarlung Zangbo.
“People move due to desertification and their traditional occupation of herding hasn't changed,” said Yang at a workshop in Kathmandu on climate change effects in the Yarlung Zangbo/Brahmaputra Basin.
The herders that Yang spoke to linked the encroaching deserts to drought brought on by increasing temperatures and reduced precipitation.
“This has deteriorated the quality of the grassland that they used to herd on and increased the possibility of strong winds that turn to sandstorms,” he said.
Herders who previously lived by the river have been forced by to move several kilometres away by the growth of sand dunes. They must now graze their herds at altitudes as high as 5,500 metres (18,000 feet), close to the snow line.
Yang said that several villages are now surrounded by dunes up to 40 metres (130 feet) in height and 100 metres (325 feet) wide, although Yang said he had seen some dunes twice this height and width.
Wetlands between the dunes are deteriorating rapidly, and residents are considering relocating farther away from the river. Yang believes the dunes will eventually become connected, causing the wetlands to disappear.
Along the upper reaches of the Yarlung Zangbo, where the river is known as the Maquan, the connected dunes already extend for 100 km (63 miles) and are 10 km (6 miles) at their widest.
Yang noted that evaporation is intensifying due to global warming and that rainfall has become less predictable. He said that the region he visited now experiences extreme rainfall in summer, contributing a significant portion of the annual total, and that there is now rain in some areas that used not to receive it.
Glacial melting is also making the traditional hydro-geological pattern fragile and less predictable, he said.
Yang pointed out that the river is an important water source for all three countries through which it flows, but especially for Bangladesh, where it passes through heavily populated areas. In India, the Brahmaputra does not flow through many cities, and Yang said it was important to maintain its relatively pristine condition there.
The science of desertification along the Yarlung Zangbo needs to be better understood before steps can be taken to combat the process, he said, emphasizing the importance of reducing human impacts in the region.
“Over-herding is significant and needs to draw more attention,” he said, and both commercial logging and harvesting of vegetation in the middle and lower reaches of the river in Tibet have contributed to the deterioration of land, Yang said.
He also recommended restrictions on industrial development and mining in the region, and said that any hydropower development should include detailed evaluations of environmental impacts, especially in terms of geology and biodiversity.
What the region needs, Yang said, is an integrated river basin plan agreed on by all countries affected by the river system – China, India and Bangladesh. Such a plan, among other things, would need to look at how to control hazards associated with the river, at hydropower plans, at water flow and at demand for water in each country.
Teresa Rehman is a journalist based in Northeast India. She can be reached at www.teresarehman.net.
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