A strip of land intended for a wetland wildlife habitat has been revealed as a potential obstacle to development of a free-trade zone on the Hong Kong-Shenzhen border. Green groups fear the building of roads for the zone could result in the 3km strip being concreted over. The proposal to create the wetland area was raised before the river works started in 1995 as part of compensation for the destruction of fishpond areas. The improvement works straightened a section of the Shenzhen river near Lok Ma Chau, leaving 3km of river bed and adding 100 hectares of land to Hong Kong. The government promised in its environmental impact assessment to turn the abandoned river channel into a 'new wetland habitat suitable for wildlife'. However, green groups claim little has been done to achieve this since the first two phases of work were completed six years ago. Karen Woo Lai-wan, a senior environmental protection officer with lobby group Green Power, said it was worried the developer of the border zone would fill in the old channel. 'The channel will be seen as an obstacle for development of the site,' she said. 'Once the free-trade zone comes, there will be supporting infrastructure like roads and drainage to follow. It will open the door for sweeping changes to land use in the northwestern New Territories.' Mai Po Nature Reserve manager Lew Young is also concerned the wetland plan will be scrapped. 'What conservation could be done there if there is an industrial zone built next to it?' asked Dr Young The news follows the revelation last week by the South China Morning Post that the site of the proposed zone was contaminated with more than 1 million cubic metres of toxic mud dumped on the site during improvement works. A Drainage Services Department spokesman yesterday said the old river bed was supposed to be a conservation area, but could not rule out changes in land use. The Planning Department last week said it was studying the land use of the border zone.