Paotaiwan (Emplacement) Wetland Park in Shanghai's northern aoshan District, an ecological paradise, was built three years go where vast heaps of steel slag and junk were encroaching.

Reeds swaying in the breeze, egrets picking their way about mudflats, seagulls dive-bombing for a fish and marsh critters just going about their business. This tranquil scene is just within an hour's ride from frenetic downtown Shanghai.

Amazing proximity.

Even more amazing is the fact that three years ago, vast heaps of steel slag and junk were encroaching, the water was murky, the air was foul. These 50 hectares of natural wetland far smaller than the vast original and their native inhabitants could easily have been wiped out by reckless industrialization.

The Baoshan District government decided otherwise, however, and in late 2005 began a herculean task of environmental cleanup, protection and greenery planting in a wetland rescue.

The aim is to preserve the wetland ecosystem that functions as "the kidney of Earth," nature's filter, its water and air purifier.

The result is Paotaiwan (Emplacement) Wetland Park, Phase I, open to the public since May 2007. It now includes another 50 hectares of land that is expected to add another 20 hectares by the time the Shanghai World Expo opens in May 2010.

The wetland received the China Habitat Environment Award in January.

The riverside park lies in Wusong area, Baoshan District, in the north of Shanghai, where the Huangpu and Yangtze rivers meet. It has a 2-kilometer-long waterfront along the Yangtze River and is part of an ambitious plan to redevelop Baoshan's riverside parks.

Here the Yangtze River slows as it approaches the estuary; mud and sand carried by the river precipitate in the process and form wetland where water plants, water birds, fish and many animals thrive.

The wetland covers more than 50 hectares and the park includes another 50 hectares.

Phase I construction was launched in late 2005 and completed in early 2007, according to Yang Xin, president of the Shanghai Baoshan Greening Management Bureau.

It is Shanghai's second-largest wetland park only after the Chongming Dontan Wetland on Chongming Island.

A winding plank walkway lets visitors approach the river and enjoy the wetland on either side. Small fish swim about, crabs crawl on the mudflats, egrets strut about and wing their way above, seagulls dive downward to catch fish.

"Many egrets arrived in our wetland in the big snow period early last year," says Liu Shengde, deputy Party secretary of the Shanghai Baoshan Greening Management Bureau. "It was so amazing to see them strut around on the white snow."

Apart from the natural wetland, the park also has gardens and man-made forest, lawns, hills, waterfalls and streams. There are more than 13,000 trees of 53 varieties, including ginkgo, maple, cherry, bay and camphor, as well as 300,000 bushes of 77 varieties. Flowers are abundant in all seasons.

This is a place where visitors can get close to nature, but just three years ago it presented a totally different and very grim picture.

"Industrial refuse like steel slag was piling up all over. There was unauthorized construction and junkmen gathered there, making it a dirty and dangerous place," says Yang.

The wetland at Wusong estuary came into being ages ago. Its special location, the "throat" of both Huangpu and Yangtze rivers, made it a stronghold for China's coastal defense over the years.

An emplacement was built there to guard the interior in the Qing Dynasty (1644-1911), thus it was called "Paotaiwan."

It was important in the Opium Wars (1840-42), the War of Resistance Against Japanese Aggression (1937-45) and the Chinese Civil War (1945-49). After liberation, naval, air and land forces were garrisoned nearby. A hill was built upon waste steel and used for military purposes in the 1960s. It was covered with greenery and known as Paotai Hill.