Most of wetland and scenery was destroyed later through rapid industrialization without environmental management. Polluting steel factories near the wetland simply dumped steel slag and other waste at the river bank, turning the riverbank into a refuse dump.

"Some piles of steel slag were more than 10 meters high; the dump nearly bordered the wetland," says Yang. "When it rained, the slag would flow into the river, making it dark and dirty. When the wind blew, the slag particles were caught in the air, making it choking."

And the many unemployed junkmen in the area also posed a threat to public security.

Therefore, the Baoshan District government decided in 2005 to clean up the area and revive the wetland. All the steel slag (the leftover from smelting ore) was buried deep. Soil, plants and trees were brought in and an ecological park was set up along the riverbank.

"Unlike chemical discharges, steel slag won't damage the environment when it is buried deep," says Yang. "And the soil and plants above can help purify the water and soil."

Protecting what's left of the original wetland is a major task.

"The 50-hectare wetland is a precious treasure for the ecosystem here," says Yang. He calls wetland "the kidney of Earth," a purifier and filter that protects water resources.

Ecologists call wetlands transitional areas between terrestrial ecosystems and aquatic systems; the two systems are inherently different from each other, yet dependent on each other. They meet in the wetlands that are places of great biodiversity. Many water birds only reproduce in wetlands.

Wetland, forest and ocean are considered the three great ecosystems.

Wetland not only provides a friendly habitat for many creatures but also protects water resources on the land. Polluting substances in water will naturally precipitate when a river or stream flows slowly through a wetland; toxins will break down while nutrients will nourish plants.

Wetlands can help prevent drought and flood through its exchange between underground water and surface runoff. They also can prevent seawater from invading the land and freshwater.

Yet the "kidney of Earth" couldn't possibly purify the many tons of refuse along the river in Baoshan District. No water birds or migratory birds would ever nest where the water was dark and smelly and the air was suffocating.

"Luckily, with our efforts, we have successfully turned the dump back into an ecological area," says Yang. "Water plants like wild water bamboo are found again here and many birds have discovered this wonderful habitat. You will find seagulls there these days."

The park was opened to the public in May 2007. Because of the damage that too many visitors can cause, officials decided to charge 5-yuan admission to discourage too many sightseers. The original plan had called for free admission.

It took about 150 million yuan (US$22 million) to move the refuse piles and build the first phase of the park, according to Yang. Another 300 million yuan will be spent to complete Phase II of an additional 20 hectares.

"We plan to complete an ecological zone along the riverbank in time for World Expo 2010 opening in May 2010," says Yang.

Opening hours: 5am-5pm (free during 5-7am)

Address: 206 Tanghou Rd, Wusong, Baoshan District

Admission: 5 yuan

Tel: 5657-9007

Wetlands in China

China has more than 66 million hectares of wetland, representing 10 percent of the world's total the largest wetland area in Asia and the fourth-biggest in the world.

There are 31 kinds of natural wetland and nine man-made wetland, according to the International Convention on Wetlands. They include natural marsh wetland, river wetland, littoral wetland and reservoir wetland. These are scattered throughout China, from the cool temperature zone to tropical area, from coast to inland, from plains to plateau.