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Half Empty ep.5: Remote sensing monitors wetland fluctuations

Reporter: Han Bin 丨 CCTV.com

05-19-2015 21:00 BJT

Full coverage: Special Series: Half Empty

Scientists often refer to wetlands as the kidneys of the earth. They are one of nature's ways to filter pollution and protect a water source. Unfortunately, rapid urbanization and modernization have taken their toll on China's wetlands. 

Poyang Lake

Poyang Lake

Today in our special series "Half Empty", we go to Poyang Lake, one of East Asia's most important wetlands, to see the environmental damage to the wetlands there, and the difficulties in restoring the area. 

“From a scientific view, the lake is like an open-air lab. By observation and analysis with satellite and remote sensing, we identify wetland problems,” said professor Chen Xiaoling, State Key Lab (LIESMARS), Wuhan University.

"Wetlands are like kidneys. More than 200 lakes with an area of over 1 square kilometer in China, have disappeared over the past 5 years. We need to keep a wetland bottom line of 53 million hectares through 2020. Once this red line is crossed,the bottom line of ecological balance will be broken, which will push up the cost of wetland protection.

A wetland is a natural gene pool. Biodiversity holds a crucial place. Its loss will have a devastating impact on the global ecosystem. Through remote sensing,we found the water body has been shrinking over the past decade, by 30 sq. km. every single year. The marsh encroachment and sand dredging remain the biggest problems.

Poyang Lake

Poyang Lake

There's also human activity. The Three Gorges Dam, on the upper reaches, was filled in 2003. Lake area decreased dramatically. The drought period came early. Operation of the Three Gorges Dam, likely contributed to lake drawdown,

though scientific evidence is needed. If a dam is built on Poyang Lake, water flow and quality will be greatly affected.

The biggest threat to China's wetlands is their gradual disappearance. Take Poyang Lake for example. Remote sensing shows that since the 70s, the water body has been shrinking from edge to center, rapidly turning into marshland. If this trend continues, this lake will disappear one day. All wetlands face this challenge.

The density change in floating sand, is evidence of the deterioration caused by sand dredging in Poyang. We've found over 200 boats there. Each can dredge over 10,000 tons an hour, hundreds of millions of tons every year. That's dozens of times what lake water brings in. It seriously affects water quality and the ecological environment. The government has set a seasonal ban on dredging. Yet remote sensing still finds secret dredging activities.

China stresses GDP growth. It should also stress green GDP to ensure environmental protection to quantify the performance metrics. I hope the government and the public can protect the wetlands as a precious public treasure. I also hope wetland management can be improved by strengthening legislation and supervision. Public awareness can be raised. China's wetlands will see a better future." 

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