Threatened dolphins will return to their habitat when disruption from the building of the airport's third runway ends, an international expert said confidently yesterday, citing two examples from the United States.
Professor Bernd Wursig, who was hired by the Airport Authority to assess the prospects for the Chinese white dolphin population that makes its home off North Lantau, said he was "positive" on the chances of the Chek Lap Kok dolphins coming home.
Wursig, who first studied the city's Chinese white dolphins in the early 1990s, is one of two experts hired by the authority to assess the threatened species' ability to survive the runway work, which will see 650 hectares of land reclaimed.
His comments come as environmentalists step up the pressure on airport chiefs, saying the runway work will do unprecedented damage to both the size and quality of the dolphins' habitat. They have criticised as inadequate measures identified by the authority in an environmental impact assessment of the plan.
Wursig, an expert in marine mammal behaviour at Texas A&M University, cited San Francisco Bay and Galveston Bay, Texas. He said both bays had lost their populations of bottlenose dolphins in the last century, but they had returned when the environment was improved.
In San Francisco, he said reclamation and dredging from the 1930s to the 1980s drove dolphins away. A large military presence, including a chain-link fence closing off the bay, caused problems during the second world war.
In Galveston, where he is based, Wursig said "amazing environmental degradation" had left "very little natural habitat" for the dolphins after 1905. A man-made island several kilometres long also caused problems. Wursig said both populations recovered due to better environmental regulations and a clean-up.
"If we can clean up properly, they will come back," he said.
But Wursig acknowledged that the Hong Kong dolphins were of a different species, and that some marine mammals, including some whales, did not return to disrupted habitats.
Local dolphin expert Dr Samuel Hung Ka-yiu was sceptical and questioned whether Wursig had come under pressure to find "successful" examples.
"They should substantiate their claims with reports and data," said Hung, chairman of the Dolphin Conservation Society. Hung studied under the other expert commissioned by the authority, Dr Thomas Jefferson. Jefferson had studied under Wursig.
Hung criticised the authority for proposing measures that were outside its power to implement - only the government could establish a new, 2,400-hectare marine park, for example, and bring in speed limits for boats. Hung also said the marine park should be set up before 2016, when work is due to begin, rather than 2023, when it will finish.
The runway plan still needs government approval, and the question of how the cost - more than HK$130 billion - will be funded has not been settled. A government consultation on the environmental assessment runs until July 19.