Hong Kong-Zhuhai-Macau Bridge construction likely ‘primary stressor’ on dolphin habitat, marine experts say
- Dolphin numbers dropped to record low following construction of bridge linking Hong Kong, Macau and Zhuhai from 2010 to 2016
- Experts say mega Lantau reclamation project will disrupt dolphin habitat and conservation plans are lacking
Conservation efforts to protect Hong Kong’s pink dolphins need to be overhauled and strengthened before major reclamation work begins off Lantau Island, marine experts have warned.
As dolphin numbers dropped to a record low, researchers at the Cetacea Research Institute (CRI) found that construction of the Hong Kong-Zhuhai-Macau Bridge from 2010 to 2016 was likely to have “considerably compromised” the dolphins’ survival rate below levels needed to sustain the population.
While the bridge had long been blamed for falling dolphin numbers, the team’s findings highlighted the need to re-examine current conservation efforts.
“The recent conservation measures in waters off north-northwest Lantau are nothing short of hopeless in terms of providing the necessary food and shelter for the animals they are supposedly meant to protect,” institute director Leszek Karczmarski told the Post.
Beloved by many in Hong Kong, the Indo-Pacific humpback dolphin, also known as pink dolphins or Chinese white dolphins, are native to the Pearl River Delta and listed as a vulnerable species.
Dolphin numbers dropped to a record low of 34 between April 2022 and March last year, compared with 188 over the same period in 2002-03, according to latest data from the Hong Kong Cetacean Research Project, a government-funded organisation unaffiliated with the research institute.
To protect the dolphins and marine life habitats around Lantau, the government has designated four marine parks comprising nearly 4,900 hectares (12,108 acres) of protected waters, with a proposal to add another 2,400 hectares around the Hong Kong International Airport.
In research findings published last month, Karczmarski and Stephen Chan Chiu Yin, co-director of Research at CRI’s division of cetacean ecology, described current efforts to protect the dolphins to be “at best inadequate and at worst outright ineffectual”.
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Established in 2017, CRI is an independent research organisation with a focus on land and marine mammals such as cetaceans, the group of aquatic mammals that includes whales, dolphins and porpoises.
Karczmarski and Chan found from examining data that soon after construction of the bridge began in 2010, the dolphins abandoned parts of their core habitat, including areas designated as marine parks to the north of Lantau.
In the most affected region, the number of dolphins dropped by half. The size of dolphin groups observed also shrank.
They found a sharp decline in the survival rate of adult dolphins, measured as a percentage of individuals in an area that survived from one year to the next. It went from 96 per cent to just over 90 per cent by the later phase of the bridge construction.
That was not only the lowest rate recorded across the Pearl River Delta, but also below the rate of 95 per cent required to ensure the species’ long-term survival in Hong Kong’s waters.
As the bridge construction was the only new large-scale project within the dolphin habitat at the time, it was “likely the primary stressor” for the changes in the dolphins’ behaviour and numbers.
Karczmarski said construction work for the bridge and the third runway of the Hong Kong airport had combined to push the dolphins towards their less-suitable secondary habitat closer to the planned Lantau Vision Tomorrow project.
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The massive HK$580 billion (US$74 billion) reclamation project aims to build three artificial islands over the next two decades, providing enough land for 210,000 flats and a new business hub.
Concern groups have long opposed the project over its potential environmental impacts.
Work was slated to begin next year, but Financial Secretary Paul Chan Mo-po announced earlier this month that the plan would be delayed for about two or three years owing to the city’s ballooning deficit.
Karczmarski urged the government to use the delay to implement meaningful measures to protect the dolphins, with a specific focus on preserving the quality and quantity of the “last viable dolphin habitat” off west-southwest Lantau.
He said these should be implemented before the reclamation work begins.
The Agricultural, Fisheries and Conservation Department said dolphins often avoided areas affected by major infrastructure projects and the observed changes in their behaviour could be “an adaptive response”.
“Therefore, such habitat displacement during the construction period is predicted, but the effect should only be temporary,” it said.
It added that the proposed North Lantau Marine Park near the airport, once established, would link up two other Hong Kong marine parks and a mainland China nature reserve, allowing the animals to move across their core habitats.
“Statutory protection and proper management provided by these marine parks will not only help in enhancing the conservation of [pink dolphins] but also be conducive to [their] early return to Hong Kong waters after the cessation of temporary disturbance associated with marine construction activities,” it said.
The Development Bureau said that based on long-term monitoring by the conservation department and environmental impact studies done for the Lantau Tomorrow Vision project, it found that the central waters where the reclamation project was planned were “not an important habitat” for pink dolphins.
But it added that it would comply strictly with requirements and mitigation measures under the Environmental Impact Assessment Ordinance.
