Sand, silt and smooth cordgrass

The Shanghai Chongming Dongtan National Nature Reserve is one of the few reserves scattered across the Yangtze River basin to have made real progress in the restoration of degenerating wetland.

Much of the damage to the wetland - formed by the deposits of mud and sand silt carried by the Yangtze River as it drains into the East China Sea - has been caused by a salt-marsh grass that, despite its green and soft appearance, is killing the landscape, according to Tang Chendong, the reserve's director. Spartina alterniflora, commonly known as smooth cordgrass, is native to the Atlantic coast of the Americas, where it is found in intertidal wetland. It has become notorious as an invasive plant around the world because of its capacity to accelerate the accumulation of sediment and cause the level of the land to rise on the seaward edge.

It was introduced to China in 1979 as an environmental engineering measure. It was intended to catch sediment and allow it to accumulate and prevent coastal erosion.