Climate change linked to the contraction of wetlands at the
source of the country's two longest rivers, the Yangtze and the
Yellow, has reduced the volume of water flowing in them, scientists
said.
Scientists from the institute of mountain hazards and
environment under the Chinese Academy of Sciences (CAS) studied
changes over the past 40 years to the wetlands on the cold
Qinghai-Tibet Plateau in west China where the two rivers have their
source.
Analyzing aerial photos and satellite remote-sensing figures,
they found the wetlands on the plateau have shrunk more than 10
percent over the past four decades. The wetlands at the origin of
the Yangtze have suffered the most, contracting by 29 percent.
In addition, about 17.5 percent of the small lakes at the source
of the Yangtze have dried up, the scientists said.
"The wetland plays a key role in containing water and adjusting
the water volume of the rivers," Wang Xugen, a researcher with the
institute, said.
"The shrinking of the wetland on the plateau is closely
connected with global warming," Wang said, adding that - even
though rainfall has increased in the region - the contraction of
the wetland has reduced the flow of the Yangtze and Yellow
rivers.
Figures by the World Wildlife Fund (WWF) weather station at the
head of the Yangtze showed annual rainfall at its source increased
from 260 mm during 1991-2000 to 323 mm in the period 2001-06.
"But the increased rainfall didn't lead to more water flow in
the rivers because the evaporation was so fast as a result of
global warming," Li Shijie, a researcher with the Nanjing institute
of geography and limnology under the CAS, said.
Another WWF study showed global warming has caused glaciers to
shrink, frozen earth to melt, grasslands to turn yellow and rivers
to dry up.
The Qinghai-Tibet Plateau used to boast 36,000 glaciers covering
an area of 50,000 sq km. In the past 100 years, their area has
shrunk by 30 percent.
(Xinhua News Agency, China Daily July 16, 2007)
