To compensate for the loss of natural wetland, artificial marshes have been created near river channels. However, their impact has been limited, according to Ng, who pointed to the mud drying on the boundary of the wetland. During the arid winter season, the drying land spreads to the core of the wetland.

"The water levels were lowered and the water patterns were altered after the river was channeled. The wetland can't get enough water during the dry season," he said.

In 2005, a partnership to preserve Long Valley's wetlands was formed by the Conservancy Association, the Hong Kong Bird Watching Society and local stakeholders, especially landowners, farmers and villagers.