Dolphins under 'serious threat' from third runway

PUBLISHED : Tuesday, 07 June, 2011, 12:00am
UPDATED : Tuesday, 07 June, 2011, 12:00am

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Building a third runway at Hong Kong's airport will pose a serious threat to the dwindling population of Chinese white dolphins, experts warn. But they are unable to quantify the extent of the threat.

Some specialists predicted their demise with the building of Chek Lap Kok airport off North Lantau in the mid-1990s.

Since 1997, a total of 135 white dolphins have been found dead in Hong Kong waters. Fewer than 10 per cent of these deaths could be explained, however, because the carcasses were too badly decomposed.

Dolphin experts said it was impossible to predict what would happen to up to 200 dolphins in Hong Kong waters and 2,500 in the Pearl River Delta area if the authorities give the go-ahead to another runway.

Building it would require reclaiming 650 hectares from the sea - an area equivalent to half the present size of the airport. The proposed site for the runway is in a habitat actively used by the dolphins.

Scientists have carried out extensive research on the dolphins over the past two decades, covering their breeding, feeding and roosting habits and social structures. But the causes of dolphin deaths are still a mystery.

Dr Samuel Hung Ka-yiu, chairman of the Hong Kong Dolphin Conservation Society, has been involved in dolphin research since late 1990s.

Hung said the dolphin population in Hong Kong was in decline statistically, based on monitoring data he had obtained in past years.

He said the Airport Authority should work closely with the government to work out 'dramatic measures' to protect the species in the long term.

'Merely designating a marine park is definitely not enough. They have to think out of the box,' Hung said.

He said dolphins die for a variety of reasons, including pollution, disease or collisions with sea-going vessels. But the condition of the carcasses found was usually too poor to establish the cause of death.

'The death number is so random that we can't draw any conclusion unless there is a regional effort to recover most of the carcasses,' he said. 'A lot has been done on researching the habitats, acoustics, and even the social behaviour of the dolphin and more study is unlikely to yield anything more significant.

'The most important thing is for the authorities to acknowledge the environmental impact.'

The Airport Authority is certain to have to live up to higher expectations than when the airport was first built in the mid-90s, when less was known about the dolphins.

Collisions with vessels, entanglement in fishing nets and even drowning have been cited as causes of deaths.

Data from the Agriculture, Fisheries and Conservation Department shows that each year between five and 14 dolphins are found dead.

Male deaths far outnumber female deaths; nearly half are calves. More than half of the dead dolphins were found in North Lantau waters.

In the light of the massive infrastructure works planned for the area, including construction of the cross-delta bridge to Macau and Zhuhai, Hung said what was most needed now were major dolphin conservation measures.