Chances for a recovery of natural habitat and animals in the Tung Chung River are good, says Professor David Dudgeon, head of the department of ecology and biodiversity at the University of Hong Kong.
The rich intact habitat above the bridge will provide a source of new life that will 'colonise' downstream. 'Animals living in local streams have evolved to cope with the regular, predictable physical disturbances caused by typhoon and monsoon floods,' Professor Dudgeon said.
'During these, sand and mud is washed into the stream, the bed and banks are scoured, stones are overturned, and the habitat is disrupted. Animals that experience such events every wet season over many generations have life histories that facilitate rapid recovery to pre-flood abundance.'
This means that the physical disturbance at Tung Chung is reversible, as long as the habitat has been restored to something resembling the original conditions. 'If that is done, then time and natural processes should take care of recovery. But remember, this only applies if the upstream area remains intact and provides a source of colonists.'
Professor Dudgeon said it would be a very different story if the banks and bed had been concreted. In those cases, without removal of the man-made structures, natural recovery was impossible.
World Wide Fund for Nature assistant conservation officer Clarus Chu Ping-shing is among prominent environmentalists who consider the restoration successful. 'The stream bank and stream bed have been stabilised using natural rock,' he points out. 'Stream structures, including pools and riffles, have been rebuilt, vegetation has been replanted or seeded, the haul road has been removed and the stream profile and setting somewhat resembles the condition before it was disturbed.'
