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
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,
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.
(China Daily 07/16/2007 page3)