Little is known about one of Hong Kong’s most elusive, endangered, and endearing species, the Chinese Pangolin (Manis pentadactyla), now the subject of a conservation effort and research involving the Agriculture, Fisheries and Conservation Department (AFCD), Kadoorie Farm and Botanic Garden (KFBG), and other partners, as well as separate research by ecologists at the University of Hong Kong.

Pangolins, also known as scaly anteaters, are a unique group of mammals characterised by their armour of overlapping scales. Powerful limbs and claws for digging, long tapering snouts, and sticky tongues that can stretch to 40 centimetres – sometimes longer than their bodies – have adapted them well for their favourite diet of ants and termites. Without teeth to challenge predators, they curl in a ball when threatened. The Chinese Pangolin, one of eight species of pangolin, grows to around the same size as a corgi dog, a length of around 40 centimetres.

Yet pangolins, which are surprisingly friendly and endearing when encountered in a rescue centre, have the dubious distinction of being billed “the world’s most trafficked mammal”. This is largely due to the demand for their scales in Chinese medicine – despite the scales being made of keratin, the same material as hair and fingernails, with no scientifically proven benefits for human health.

In September 2020, Hong Kong Customs and Excise Department found a tonne of pangolin scales in a consignment of illegal wildlife products being shipped from Indonesia to Mainland China. Thousands of animals would have had to perish to make up such a haul, and over a million are said to have been poached in the past decade.

KFBG’s forensic genetics team is involved in combatting this trade from Southeast Asia and Africa. “Our genetics team was able to discover the region in Africa where White-bellied Pangolins originated by working with African scientists and sharing DNA results,” said Dr Gary Ades, Head of the Fauna Conservation Department, at KFBG.

Meanwhile, Hong Kong’s country parks, with the steep hills that the Chinese Pangolin appears to favour, are an important last sanctuary in the battle against trafficking of the species overall.

“Hong Kong has one of the last healthy wild populations of Chinese Pangolins. This species is extinct over much of its historical range and therefore any programme to protect the species is important globally,” Ades said.

The Chinese Pangolin is listed as critically endangered on the International Union for Conservation and Nature (IUCN) Red List of Threatened Species. KFBG is involved in the government’s species action plan, launched in 2020, through rescue and release work and education to raise awareness of the pangolin and its urgent need for protection. AFCD began surveying pangolin burrows and setting up camera traps over a year ago, which will inform future habitat protection. Any animals being released after rescue may be studied further using radiotelemetry, Ades said.

The KFBG Wild Animal Rescue Centre plays an important role in such conservation by rescuing, treating, and releasing as many pangolins as it can. It is also on the look-out for poachers’ wire or cage traps found in the countryside, which can catch pangolins and many other species.

The risk of poachers targeting the pangolin in Hong Kong is described as real but low in the species action plan. Their major local threat is from feral dogs. Of the 13 pangolins received by the rescue centre since it opened in 1994, five or six were likely to have been attacked by dogs. Ten have been released back to the wild.

“Apart from humans, dogs are the pangolin’s biggest enemy in Hong Kong,” Ades said.

Yet being so elusive means little is known about the Hong Kong pangolin population, its whereabouts, and viability, though the young, injured animals that KFBG has received suggest they are breeding.

Ades is hopeful that AFCD’s conservation project can make a difference. “For me, a key requirement for the protection of local pangolins is to have eyes on the ground studying the animals. We need early warning if poaching becomes a serious issue in Hong Kong and the only way this will happen is if researchers are in the field monitoring burrows and setting up camera traps. Appropriate enforcement work then has to follow.”

Other researchers doing such monitoring include Dr Tim Bonebrake, who leads the Global Change and Tropical Conservation Lab at the University of Hong Kong’s School of Biological Sciences. He has made the Chinese Pangolin the subject of his research, and is sharing information with the AFCD project.

With little information available on the local pangolins, his study, with PhD student Anna Goldman, has involved considerable time and effort simply to figure out where they are, before even considering their habitat requirements. He does not know whether they are so hard to find because they avoid people, or that there are so few of them.

“There’s a lot of evidence, like burrows, we can find in country parks. But we only got our first image after eight months of camera trapping,” he said.

Bonebrake noted that fieldwork in Taiwan has yielded key information on the Chinese Pangolin’s behaviour but elsewhere the species’ range has been poorly studied.

He added that he saw them as “amazing creatures”. “We have some video, including [images of] them digging. While they are armoured, they can move pretty fast.”

However, those combatting the pangolin trade and conserving these mammals need to move fast too if the scaly anteater is to survive.

Among Hong Kong’s globally significant populations of animals are several species of freshwater turtles for whom the city’s environs have become a last main refuge.

While “turtle” may conjure images of impressively large sea turtles – such as the green turtle, growing to perhaps one metre – Hong Kong’s freshwater turtles are relatively small, with shells no more than a modest 30 centimetres in length. They face severe threats from poaching for the pet trade, food markets, and Chinese medicine, which has devastated their populations elsewhere in the region, and are close to making them extinct in Hong Kong.

Dr Sung Yik-hei, Assistant Professor of the Science Unit, Lingnan University, leads research in Hong Kong on these endangered species, including the Golden Coin (Cuora trifasciata), Big-headed (Platysternon megacephalum), Beal’s-eyed (Sacalia bealei), Chinese Soft-shelled Turtles (Pelodiscus sinensis), and Reeves’ Terrapins (Mauremys reevesii).

By capturing and radio-tracking individuals, Sung has learned about their ecology. He found that they mostly stayed in streams within forested areas, though they might disperse on land during and after heavy rains. One reached a stream at least one kilometre away.

Beal’s-eyed and Golden Coin Turtles may roam further, through forest areas surrounding streams, while Reeves’ Terrapins and Chinese Soft-shelled Turtles prefer flatter, more open areas, for example, around fish ponds.

Most of the turtles, which might live up to 40 to 50 years in the wild, are opportunistic feeders, with a diet including insect larvae, fish, fruit, and seeds – making them valuable seed dispersers.

Along with understanding their ecology, Sung’s marking and radio tracking of turtles has shed insight into poaching. “Last year, a Big-headed Turtle with a microchip we implanted was confiscated when being smuggled to Mainland China. It was recovered, and we released it where it was caught.”

Combatting poaching is a focus of further research that Sung is undertaking, supported by the Ocean Park Conservation Foundation. In this work, he is using infrared cameras to find traps set by hunters, with around 100 located and removed since 2016. He is also working with the government’s Agriculture, Fisheries and Conservation Department (AFCD) on a pilot study to support larger scale patrolling, which he hopes can strengthen enforcement against this illegal trade.

“If poachers visit a site for just two days, half the turtles there may be gone,” said Sung, who despite his efforts is pessimistic about the survival of these species in the wild. “They are very close to being functionally extinct, whereby they can’t perform their ecological functions in the wild, or can’t reproduce,” he said.

The Golden Coin is the most prized by poachers and as a result is now critically endangered. “In the past, it was mainly used for Chinese medicine. People believed it cured cancer.” It is also regarded as a talisman for good fortune, making it sought after in the pet trade and for breeding farms. Individual males have been known to sell for as much as HK$150,000, Sung said.

Meanwhile, AFCD and KFBG have joined forces to conserve Golden Coins in Hong Kong. An assurance colony of rescued animals is being built by KFBG. This includes a breeding programme and eventual plans to release turtles back to their natural habitats.

Dr Gary Ades, Head of the Fauna Conservation Department of KFBG, said: “Our Golden Coin Turtle conservation project is globally the most important project for this species and one that will hopefully prevent the turtle from becoming extinct in the wild.” KFBG urges the public not to buy wild-caught turtles.

Hong Kong’s native fresh water turtles are not to be confused with the turtles adorning ponds in the city’s parks, which are mainly exotic species such as the Red-eared Slider (Trachemys scripta elegans) released by pet owners when they outgrow their tanks. Such releases, particularly when into rivers and reservoirs, pose another threat to the native species, which they are now displacing.

Sung’s interest extends beyond turtles to other reptiles and snakes. A new project, starting in spring 2021, is focused on the status of Bogadek’s Burrowing Lizard (Dibamus bodadeki), a species endemic to three remote islands of Hong Kong: Sunshine Island, Shek Kwu Chau, and Hei Ling Chau.

So far, less than 20 individuals have been found. The first step in the research will be to develop ways to find them – a challenge given that they live largely underground. “If we know more about their distribution, steps can be taken to conserve them,” Sung explained. This was particularly important, given that new reclamation around Lantau Island could affect these islands.

“I hope one day people will value the presence of wild amphibians and reptiles just performing their ecological functions,” he said

Sharne McMillan, a PhD candidate at the University of Hong Kong’s School of Biological Sciences, has almost completed a study of Eurasian otters (Lutra lutra) in Hong Kong, which she began in 2016. So far, she hasn’t seen one.

However, McMillan has found otter scats, referred to as “spraints”, which she analysed to collect DNA. She has taken photographs with cameras triggered when infrared beams are interrupted, and interviewed local people in the otter’s range, which is nowadays restricted to the Deep Bay area of the northwestern New Territories.

Some people have seen them, such as fish farmers who work at night, she said. “The otters are rare and extremely elusive. They often know we’re there and leave before we can spot them.”

While people traditionally think of otters using underground holts, McMillan has not found any in Hong Kong. Instead, she suspects they may breed and rest on a bed of grass, known as an “otter couch”, as researchers have found in Taiwan. Part of the study involves looking at their habitat preferences, as they evidently favour areas with better vegetation cover and limited disturbance. “They want to feel safe,” McMillan said.

Worldwide, otters living near humans are all too often not safe, due to habitat loss, water pollution, and hunting for their pelts. Some of McMillan’s interviewees told her of otters being hunted in the past, while occasionally the animals were caught in traps set for other creatures such as birds, fish, and shrimps. Overall, interviewees suggested otter numbers had declined over time.

More happily, the interviewees had broadly positive attitudes towards this animal, which is typically considered too rare to significantly predate on fish. A recreational fisherman who supported their protection pointed out that “otherwise they will become extinct and kids [won’t be able to] see them”.

McMillan has viewed tens of thousands of images taken with camera traps. At times, these show nothing, as they might be triggered simply by grass swaying in the wind. But the cameras have also revealed mongooses, civets, snakes, birds – and sometimes, to her delight, an otter.

“Occasionally, I’ve seen images of otters with juveniles, or two otters together,” she said. “That’s very special.”

Along with collecting information, McMillan aims to help inform efforts to protect otters and suggest how they can be surveyed and monitored over the long term. “There’s a lot of interest, and NGOs, researchers, the government, and local people should work together to come up with solutions for conserving the otter,” she said.

To Dr James Lazell, a former president of the US-based Conservation Agency, Hong Kong is a “biological treasure trove”, which he only discovered by accident when a team of biologists he led was forced to abandon plans for a survey in Mainland China. This was in 1987, and spurred Lazell to make several follow-up visits to search places including Chek Lap Kok, before it was mostly levelled and transformed into Hong Kong International Airport.

Lazell is a herpetologist, and his surveys have yielded 29 species of reptiles and amphibians on Chek Lap Kok – around one-quarter of Hong Kong’s tally. They included Romer’s Tree Frog (Liuixalus romeri), which is endemic to Hong Kong, and named after amateur herpetologist John Romer, who discovered them in a small cave on Lamma Island in 1952.

Romer found more of these tiny frogs, growing to just 2.5 centimetres in length, the next year. But the cave collapsed, and for almost 30 years he searched in vain for them. He died in 1982, believing they had become extinct. But two years later, the frogs were rediscovered on Lamma. Subsequent finds on Lantau, Po Toi, and Chek Lap Kok brought their entire known world distribution to these four Hong Kong islands.

Lazell believes Romer’s Tree Frog and a handful of species that are likewise unique to Hong Kong islands are ice-age relics. They might have been common along a coastal plain that extended along southern China when sea levels were lower during the ice age, but became stranded on hilltops that became islands as the ice sheets melted and the sea inundated the plain.

After the 1990 discovery of the frogs on Chek Lap Kok, herpetologist Dr Michael Lau, chairman of the Hong Kong Wetlands Conservation Association and co-author of Hong Kong Amphibians and Reptiles (1998), scoured the island for more.

He rescued 220 adults before the island was largely levelled to create the new airport. Melbourne Zoo agreed to help with a captive breeding programme, and soon established a healthy population, enabling Lau to release over 1,100 frogs and 1,600 tadpoles at eight sites in Hong Kong.

Today, five of those eight translocated populations have survived, with at least three spreading up to two kilometres, according to Lau, who teaches on the Conservation Biology and Management Master’s programme at the University of Hong Kong.

Romer’s Tree Frogs are monitored and surveyed by the Agriculture, Fisheries and Conservation Department, among others, which has provided up-to-date information on the distribution of this unique species. However, a full population estimate has yet to be done. The largest population is at Ngong Ping, Lantau, and as a result this has been designated a Site of Special Scientific Interest since 1999.

The Tung Chung New Town extension may impinge on some of the habitats but Lau said that the frogs affected would be translocated again to suitable sites nearby. “Since it is protected with a species action plan, the habitat requirement and ecology is well studied, and will be flagged in EIAs [environmental impact assessments] and planning studies, should it be affected by development,” he said.

In addition, existing populations on Lantau and Lamma have expanded since the early 1990s as the forests there mature. “I think the future of this species is quite secure,” Lau said.

Meanwhile, new species of amphibians and reptiles in Hong Kong continue to be found, with recent discoveries including Lau’s Leaf Litter Frog (Leptolalax laui), which is named after Lau.

Among other vertebrates first found in Hong Kong and new to science is a type of paradise fish. Researchers including David Dudgeon, Emeritus Chair Professor in Ecology and Biodiversity at the University of Hong Kong, discovered this fish in 1996. It was subsequently identified from its morphology and named the Hong Kong Paradise Fish (Macropodus hongkongensis) by researchers in Germany, while recent genetic work has confirmed that it is distinct from other paradise fishes in Southeast Asia.

Distinguishing features of the Hong Kong Paradise Fish, which has long elegant fins, and red pelvic fins, include black spots on its head and body as well as a white first ray on the pelvic fin. Like other paradise fishes, the male builds and guards a floating bubble nest, in which the eggs and developing young are tended. The female takes no part in parental care.

The Hong Kong Paradise Fish was initially believed to be endemic to Hong Kong, though soon after was found to be present in eastern Guangdong and Fujian. In Hong Kong, it lives in slow-moving streams and wetlands in Sai Kung, Tai Po, and the northern New Territories.

In 2019, a team of biologists from Nanjing Forestry University investigated further, completing the first mitogenome sequence of the Hong Kong-named fish. This determined its uniqueness, and that its closest relative was the Red-back Paradise Fish (Macropodus erythropterus), endemic to Vietnam and sequenced in 2016, rather than the more common Chinese Paradise Fish (Macropodus opercularis) found in Hong Kong and elsewhere in China.

The Hong Kong Paradise Fish is one of 185 freshwater fish recorded in Hong Kong and listed among 21 of “conservation concern” by the Agriculture, Fisheries, and Conservation Department, which has recognised threats to such biodiversity from habitat loss and degradation, climate change, over-harvesting, pollution, and the presence of exotic species – factors that have caused a rapid global decline of freshwater fish populations.

Dudgeon would also like the Hong Kong Paradise Fish included on the International Union for Conservation and Nature (IUCN) Red List of Threatened Species, as has been the case with the Hong Kong Newt (Paramesotriton hongkongensis). “There is a real risk of over-exploitation, and ‘conservation concern’ does not protect animals from collection if they are outside Hong Kong’s country parks,” he said.

Meanwhile, this particular fish has one special status, as the only freshwater fish species named after Hong Kong.

While endangered, appealing vertebrates often grab the limelight, there is much more to Hong Kong’s biodiversity as a whole. Ant species alone extend to several hundred.

Dr Benoit Guénard, of the University of Hong Kong’s School of Biological Sciences, studies insects, especially ants. To Guénard, ants are important for their interactions with other groups of organisms, helping seed dispersal, aerating and enriching soil, and playing their role in the nutrient cycle, among others.

“They are huge in terms of predation – removing many herbivorous insects, so we have forests,” he said. He is particularly intrigued by their behaviour as social insects and how this contributes to their success.

Moving on: the social nature of ants extends their individual capabilities. Photo: Francois Brassard

Guénard is now continuing research on Hong Kong ants, one of the insect groups with relatively strong data to build on. During his career he has described 27 insects such as ants, flies, and wasps that were new to science, the most recent being four new ant species from Hong Kong and Macau, of the genus Polyrhachis, along with seven of that genus that were newly recorded in this area, published in Asian Myrmecology in February 2021.

The seven-millimetre-long Paratopula bauhinia, named in the vernacular as the Golden Tree Ant, was the first species Guénard described in Hong Kong, in an article also published in Asian Myrmecology in 2016. The discovery proved especially notable as the ant is the only member of its genus yet known in Hong Kong.

As its name suggests, this is a forest ant, resting on trees during the day and, as evening approaches, descending to forage in lower vegetation during the night. Guénard and researcher Ying Luo found such ants just a few hundred metres from the university and, to date, they are unique to Hong Kong Island.

Since then, he has described eight more ant species, three species of flies and two species of wasps from Hong Kong. He explained that a newly described species indicates that it is considered new for science.

“First a species has to be described by taxonomists, not only to have a name, but most importantly to have a description that will distinguish it from all other species. Once it has a name, a species can be recorded from other regions, so the knowledge on the species distribution improves.

“Both taxonomic descriptions (‘naming’) and recording (‘knowing the distribution of a species’) are important steps in order to study them, and eventually protect them,” he said.

“Finding new species is not so unusual when you’re an entomologist,” he said. “But it’s always exciting, describing something nobody has found.”

Many more are likely to be discovered. “We are still working on a final list of the ants of Hong Kong, and still frequently discover new records and new species. It seems reasonable to say that between 300 to 400 species of ants can be found in Hong Kong,” he said. Ant species known globally extend to more than 15,700, a number expected to increase considerably in the coming years.

Not all ants are welcome. Several are “invasives” – exotic species introduced by humans and with some negative impacts on biodiversity, and even people. “Hong Kong has one of the highest densities of invasive species in the world, only exceeded by Hawaii and Florida,” Guénard said.

“At ecosystem level, there’s something like an equilibrium between predators and prey that may have evolved over millions of years. But when species from outside arrive, they are playing a different game,” he explained.

The Red Imported Fire Ant (Solenopsis invicta), which is native to South America and named for its intensely painful sting, is especially prominent among Hong Kong’s invasive ants. Guénard is studying fire ants here, and has learned that some farmers are so deterred by the stings that they give up farming part of their land.

Native ants, by contrast, play an important role in local ecosystems. For instance, Weaver Ants (Oecophylla smaragdina) defend trees against herbivores. They make nests by sewing leaves together, forming brown, ball-like structures that are easily spotted in branches.

“If you look in a nest, you find a community of insects within,” Guénard said. “There are species that mimic ants – such as spiders that prey on them, and juvenile stick insects that avoid predation by living amongst the ants. Others are kept by ants for food. With invasives, you lose all of this interdependence.”

One way to expand space for nature in such a dense, high-rise city as Hong Kong is to extend the greenery upwards in the form of vertical green walls, and roof gardens and woodlands.

The Hong Kong government sets minimum requirements for green space around buildings, and encourages sky gardens in the Development Bureau’s Sustainable Building Design Guidelines. But in vertical greening, the city is lagging behind Singapore, according to researchers.

However, there are examples of green-clad buildings established long enough to prove they not only improve the energy efficiency of the building, but have also become established homes for birds and insects.

Professor Jim Chi-yung, of the Education University of Hong Kong, and known as the father of the city’s green roof movement, is delighted that the green wall wrapping and rooftop woodland that he designed and completed for China Light and Power (CLP)’s substation at Chui Ling Road in Tseung Kwan O in 2013 is continuing to thrive today.

Rather than using planters to green the 500-square-metre façade, Jim employed “nature’s climbers”, such as Chinese Wisteria, Japanese Honeysuckle, and Firecracker Vine. For the Sky Woodland on the 520-square-metre roof areas, Hong Kong Camellia, Incense Trees, and Scarlet Sterculia were among 80 trees from 32 native species planted. This is now home to nesting birds, bees, butterflies, and other insects.

Jim is continuing to explore the area, leading research to investigate the optimal soil conditions for green walls and roofs, and their cooling and energy-saving benefits. A 2020 study showed that a woodland canopy intercepted about 90 per cent of incoming solar radiation, and on sunny days reduced highest mean surface temperatures by 2.77 degrees Celsius, and the air temperature by 2.27 degrees Celsius.

Meanwhile, he has indicated that safety elements – such as loading limits and drainage – also needed to be informed by science and need not limit the ambitions for more green buildings.

“Green roofs are important islands of nature in the city,” he said.

Indeed, flocks of sparrows and Black-collared Starlings can now be seen foraging in the grass of one of the largest of the city’s green roofs, above the Central-Wan Chai bypass tunnel portal, commissioned by the Highways Department. The tunnel opened to traffic in 2019.

Other Hong Kong researchers have utilised their expertise in architectural and building science to inform greater use of vertical greening, including on skyscrapers.

Research by Dr Caroline Chan, Lecturer in Building Science and Technology at City University of Hong Kong, described vertical greening as of paramount importance as Hong Kong’s population and urban areas continue to expand.

She has explored why there has been little application of vertical green walls, with Hong Kong trailing Singapore in terms of high-rises with self-sustaining vegetation for cladding. This is despite widespread local and international interest in the benefits of such walls, for reduced energy consumption, mitigating against air pollution, and increasing biodiversity in the city.

Vertical greening has been used on government and utility buildings, and retail levels of some recent developments, such as the living wall for the K11 Musea retail and cultural complex in Tsim Sha Tsui, but does not match Singapore in reaching to the higher levels of city skyscrapers.

Chan’s survey of architects, published in 2018, indicated the mix of incentives and guidelines that could help developers green their buildings upwards to overcome the higher initial costs and price of maintaining a green façade.

“There are improvements in Hong Kong,” she said. “More greening has been done by the government and private sector. New developments are usually larger in scale, which make them more flexible to incorporate green designs in the planning stage.”

Additional education was needed to promote sustainable design knowledge among young professionals, with this area included in university courses, research, and community activities such as design competitions and exhibitions, Chan said.

While Chan cites improving biodiversity by creating habitats for birds, insects and microorganisms as a benefit of greening, “attracting pests and unwanted animals” was, ironically, a concern among the surveyed architects, as were technical issues such as implications for structural load capacity and damage to the building.

Hong Kong buildings could go greener if there was “more research related to the technical issues such as the suitable species for growth in Hong Kong in view of the climate change in recent years, design details for cost-effective greening options, especially for cutting costs in the maintenance period, and technical guidelines for designers and building owners”, she said.

Meanwhile, fieldwork and modelling by a research team at Chinese University of Hong Kong’s School of Architecture and Institute of Future Cities, published in 2017, found that such efforts would be worthwhile. Greening 30 to 50 per cent of high-rise facades could make for a more comfortable city by reducing daytime and night-time temperatures by one degree Celsius. The team advocated that greening at ground level, vertical facades, and roofs should be included in the urban planning process.

But equally important, such greening brings quick benefits for nature too. Jim said of the CLP sub-station project: “When we started planting trees, they had not even settled in the soil when the birds and butterflies began to come.”

One of the joys around and above the skyscrapers of Hong Kong Island is the sight of the Yellow-crested Cockatoo, not in a cage but flying wild.

In fact, this bird is not a Hong Konger at all, but an introduced species living far from its original home of Indonesia. However, it has become a well-established city resident, and given it is rated as a critically endangered species by the International Union for Conservation of Nature (IUCN) Red List of Threatened Species, its presence in Hong Kong is now important for its survival.

Free-flying cockatoos, likely to have escaped from captivity, were first recorded in Hong Kong in the late 1950s, according to the University of Hong Kong’s Dr Caroline Dingle, whose team studies this species in the city, among others. Cockatoos found fruits and nuts, and even nectar from Cotton Trees to their liking, along with holes in trees where they could breed and establish a population.

Today, there are around 150 to 200 cockatoos living wild on Hong Kong Island – almost one-tenth of the world population in the wild.

- Dr Caroline Dingle

“Although Hong Kong is not the native habitat for this species, the Hong Kong population is now likely one of the biggest populations of the cockatoo, and is relatively safe from trapping,” Dingle said. “One of our goals is to monitor their breeding success to determine whether this population is likely to persist.” There was no evidence that the introduced species was having any negative impact on the local ecology, she added.

The study could also help determine whether the Hong Kong population is healthy enough to allow some to be captured, and released in the species’ native Indonesia, where demand for the pet trade has devastated its population, particularly in the east of the country.

Meanwhile, Dingle’s focus is on ensuring they survive here. “Not many cities are a safe haven for a critically endangered species,” she said. “They are an incredible asset for Hong Kong. You look out of the window, and they are just outside.”

Many birds heading into Hong Kong on a stopover or winter basis have found a surprising haven in the heart of the city.

Ho Man Tin, a mainly residential area in Kowloon, has become a popular birdwatching destination to catch sight of these migrants, thanks to a combination of a favourable woodland habitat bordering its reservoir and pioneering observations by citizen scientist John Chow.

Chow works as a school science laboratory technician in the Ho Man Tin district. In 2012, a friend introduced him to birdwatching, a turning point in his life. He had taken students on outings to learn about astronomy, but found birds living so close to humans could be a greater inspiration for them.

He began learning more, including taking a course with the Hong Kong Bird Watching Society (HKBWS).

To Chow, even well-known birds can be intriguing, such as the mysterious meanings of the calls of the Cinereous Tit. He also began finding migrants that were uncommon or extremely rare in Hong Kong, including Narcissus Flycatchers with black upperparts and brilliant orange-yellow underparts.

News of his sightings spread among the birdwatching and bird photography community, and Ho Man Tin soon rose up the ranks of Hong Kong birdwatching sites.

Chow voluntarily contributes to knowledge of Hong Kong’s birdlife through fieldwork and submitting observations to the HKBWS, along with taking students on outings to inform and encourage them to learn about the natural world.

“There are many special records from Ho Man Tin,” he said. “The first spring Black-headed Bunting; the first Tiger Shrike with its breeding plumage; the latest spring Yellow-browed Warbler.”

Some birds, such as Tiger Shrikes, rest up in Ho Man Tin more than other areas of Hong Kong, Chow said. Others, such as the Brown-chested Jungle Flycatcher (another Hong Kong rarity, which Birdlife International ranks vulnerable to extinction), always visit the same tree in the area at the same time of year.

From 10 to 50 birdwatchers may visit Ho Man Tin each day during the peak autumn period. Even more might gather when there is a notable rarity, such as when a Fairy Pitta – a relative of thrushes with plumage that would make a kingfisher proud – stops over during a spring or autumn migration.

However, Chow added that his records show that fewer birds are now wintering in the area, which he believes may be due to climate disruption and loss of habitats beyond Hong Kong.

As such, while Hong Kong may stand out in having so many birds in and close to the city. these creatures are also a reminder that such biodiversity requires not only local care and conservation, but is interconnected to the regional and global challenges facing nature.

Bronze sweeper (Pempheris oualensis) fish at Wong Mau Chau, off Sai Kung. Photo: Apple Chui

The city’s 1,600 kilometres of open waters and over 1,100 kilometres of shorelines host a wide range of ecosystems where a mix of tropical and temperate organisms can survive. The challenges they face are also extensive

One of the prime benefits Hong Kong has enjoyed – indeed its raison d’etre as a city – is being almost completely surrounded by water.

It was, after all, originally a fishing community, while the natural harbour between Hong Kong Island and Kowloon brought ships and international traders to its shores in the 19th century.

The city is still one of the busiest ports in the world, with as many as 322,600 sea-going and river-trade vessels plying its waters in 2019, according to the Hong Kong government’s Marine Department.

But it also remains remarkable for its vast stretches of open waters, encompassing 1,651 square kilometres, and 1,189 kilometres of shorelines that seemingly have everything – over 250 islands, craggy rocks and the UNESCO Geopark, sandy beaches, and shallow waters giving way to mudflats reaching as far as the eye can see towards neighbouring Shenzhen.

A recent comprehensive review of Hong Kong’s marine biodiversity, published in 2016 and led by Professor Gray A Williams of The Swire Institute of Marine Science (SWIMS) and School of Biological Sciences, The University of Hong Kong (HKU) and funded by the Environment and Conservation Fund, put the number of species recorded in Hong Kong at approximately 6,000.

This diversity is of regional and indeed global significance. The study showed Hong Kong’s waters account for less than 0.05 per cent of the South China Sea (3.4 million square kilometres) yet over one quarter (26 per cent) of all the species that have been found in Chinese waters.

Chinese White Dolphins, seahorses, and the small yet highly venomous blue-ringed octopus are among the many creatures in the area, with some taxonomic groups particularly well represented. For instance, Hong Kong accounts for around 29 per cent of the hermit crab species in the World Register of Marine Species, a global database.

In addition, ecological engineering species that once covered large expanses of the local marinescape, such as corals, oysters, and seaweeds still create their own unique ecosystems.

BIODIVERSITY HOTSPOT

This biodiversity is recorded in the Hong Kong Register of Marine Species, under the umbrella of the World Register of Marine Species, led by SWIMS and set up by Williams’ research team after completing their review.

“This is a bright hotspot for marine biodiversity, being on the edge of the coral triangle centred around the Philippines,” said Williams, who came to Hong Kong when SWIMS (then the Swire Marine Laboratory) was opened on the rocky outcrop of Cape d’Aguilar in the southeast of Hong Kong Island in 1989.

Interacting factors lie behind this rich biodiversity, Williams explained. Hong Kong’s location on the edge of tropical and northern temperate waters, with a monsoon climate bringing hot summers and cool winters, means it can support a mix of species from both zones.

It is also influenced by the Pearl River to the west and oceanic waters to the east, resulting in a gradient of different salinities. Finally, its geology has provided habitats for a wide range of species. “We have mangroves, soft and muddy shores, as well as hard rocky substrates,” Williams said.

There are two cetaceans, the Chinese White Dolphin (Sousa chinensis) and Finless Porpoise (Neophocaena phocaenoides), that can be seen in Hong Kong all year round. But their differing habitat requirements mean they rarely meet. The dolphins prefer the estuarine waters in the west while the porpoises are more inclined to the oceanic waters in the east and the transitional zone between.

Meanwhile, the estuary has enabled large wetlands, such as Mai Po Nature Reserve which, together with Inner Deep Bay, supports up to 60,000 birds from over 400 species, including one quarter of the world’s Black-faced Spoonbill (Platalea minor) population during their annual winter migration.

MARINE PROTECTION

In recent decades, protecting this environment has moved up the policy agenda. Since the Marine Parks Ordinance was enacted in 1996, six parks have been designated for the purposes of conservation, education, scientific studies, and recreation. These parks comprise Hoi Ha Wan in Sai Kung; Sha Chau and Lung Kwu Chau; The Brothers; Southwest Lantau; and Tung Ping Chau and Yan Chau Tong in the northeast. Cape d’Aguilar on the southeastern coast of Hong Kong Island is the sole marine reserve. Together, they cover around 4,050 hectares.

New sites at the Soko Islands and the Three Runway System Marine Park are also scheduled. The latter will effectively connect up with Sha Chau and Lung Kwu Chau, and The Brothers, becoming Hong Kong’s largest marine park to date, with an area of around 4,500 hectares.

Even so, Hong Kong has not yet reached the international Convention on Biodiversity’s goal, set in 2010, to protect 10 per cent of the planet’s seas. The city’s total marine protected areas currently stands at 2.5 per cent, excluding proposed and to-be-launched protected areas, according to the Agriculture, Fisheries and Conservation Department (AFCD).

The city has already lost 16 per cent of its shorelines to reclamation and urban development, and the marine environment is set to be reshaped further with the Lantau Tomorrow Vision project and plans to reclaim 1,700 hectares of land from the sea, ready to house up to 1.1 million people.

While visitors to Hong Kong can marvel at the best of its marinescape – from Inner Deep Bay in the west to the UNESCO Geopark in the east, Williams points out that city-scale development in two harbour areas – Victoria Harbour and Tolo Harbour – have already resulted in the removal of “massive areas of natural habitat”.

DEVELOPMENT BALANCING ACT

Hong Kong has developed into a precursor of what other cities could become, making its experiences relevant elsewhere. “There is always a dilemma between development and conservation. In reality, people need houses and places to live, and yet we also need to conserve our marine ecosystems,” Williams said.

The baseline of perceptions regarding marine ecosystems have shifted over time, he noted, citing Starfish Bay (Hoi Sing Wan) as an example. Today, this bay, located in inner Tolo Harbour, is surrounded by the high-rise apartments of Ma On Shan, but it can still be enjoyed for its glorious views across the harbour towards Plover Cove Country Park, and its sandy beach, supporting an array of crabs, worms, and bivalves, such as mussels and clams.

However, previous generations of visitors were impressed by a bay far from urban development, with even more diverse species, including numerous starfish that covered the beach. That was before pollution had taken its toll, following the building of Sha Tin and growth of Tai Po.

LIVING ON THE EDGE

Other creatures that once thrived in Hong Kong, such as the Chinese Horseshoe Crab (Tachypleus tridentatus) and Mangrove Horseshoe Crab (Carcinoscorpius rotundicauda), have seen their populations plummet over the past 20 years. A published study, by City University of Hong Kong co-authors Paul KS Shin, Li Hiu-yan, and Cheung Siu-gin, recorded the wild population of Hong Kong’s juvenile horseshoe crabs at 17 shores in Hong Kong had decreased by over 90 per cent between 2002 and 2009.

These crabs are known as living fossils as they have existed since the early Ordovician Period (475 million years ago), about 230 million before dinosaurs appeared on Earth. They are now the subject of a collaboration between CityU and the Ocean Park Conservation Foundation, which has so far enlisted more than 2,700 school students to rear juveniles, as part of an effort to save the species in Hong Kong.

Meanwhile, AFCD last recorded nesting of the endangered Green Turtle (Chelonia mydas), the only sea turtle species known to do so in Hong Kong, on Sham Wan beach on southern Lamma Island in 2012.

Other threatened species include Hong Kong’s seahorses, the Japanese Seahorse (Hippocampus mohnikei) and Spotted Seahorse (Hippocampus kuda), which have been recorded at Pak Lap Tsai, Yan Chau Tong and Tung Ping Chau Marine Parks. Both are listed as vulnerable in the International Union for Conservation of Nature’s Red List of Threatened Species.

The 2016 marine biodiversity study, Williams pointed out, is based on historical records from 1912 to 2011. In many areas, the same range of species would not now be found. “We have lost a lot, but without baseline surveys, it is difficult to quantify,” he said.

HABITAT PRESSURES

However, as marine ecologists extend their research, they are also finding new species. From surveys carried out between October 2015 to September 2018 as part of the Ting Kok+ megaproject, 294 new records of marine taxa (recorded as species, genus, or family level) were added to the Hong Kong Register of Marine Species. Highlights included two species new to science: a tree-climbing micro-crab (Haberma tingkok); and a polychaete worm (Marphysa hongkongensa).

The Ting Kok+ project, commissioned by the Environment Bureau and supported by the Environment and Conservation Fund, involved a multidisciplinary team of researchers from six universities, led by Williams. The study was designed in tandem with the local Biodiversity Strategy and Action Plan under the Convention on Biological Diversity, to assess the status of marine coastal communities in Ting Kok Site of Special Scientific Interest, Tolo Harbour, and Tolo Channel.

The area supports highly diverse habitats and flora and fauna but has been heavily affected by human activity and water pollution.

Aims of the project included establishing a template of good practice, looking at scientifically sound methods for future biodiversity assessments, such as environmental impact assessments and ecological monitoring. Williams said: “We do need unbiased, hard quantitative science. That is the only way to make informed decisions.”

Community involvement and education are also important elements. The team trained 197 student and volunteer helpers from 24 local and overseas institutions, from NGOs to schools, who can now contribute to marine science studies of Hong Kong, and conservation. The final step has been to produce a GIS system, due for release in the coming months, available for the general public to explore this shoreline.

“It is an education tool, encouraging the general public to go to the shore and see for themselves what is there,” Williams said.

BUILDING KNOWLEDGE

He is now following up on the Ting Kok+ model with a three-year project to provide a baseline evaluation of Hong Kong’s rocky shore biodiversity, again supported by the government’s Environment and Conservation Fund. This will go further in mapping biodiversity hotspots and the distribution of ecologically important species.

Many local universities have taken advantage of Hong Kong’s maritime location to develop marine research expertise and facilities on the water’s edge. SWIMS is one example. The Hong Kong University of Science and Technology (HKUST) has its Department of Ocean Science and Coastal Marine Laboratory, the latter located on the shores of Port Shelter and focused on marine benthic, microbial and plankton ecology, and marine ecotoxicology and pollution, whereas Chinese University of Hong Kong (CUHK) has the Simon F S Li Marine Science Laboratory, where staff have been pursuing interests such as ecology and conservation of corals, mangroves, and crustaceans, as well as genomics and ecotoxicology.

CityU leads the State Key Laboratory of Marine Pollution Hong Kong, in partnership with teams at Hong Kong Baptist University, CUHK, Hong Kong Polytechnic University, HKUST, HKU, and Education University of Hong Kong, as well as partners in Xiamen and Shenzhen.

NEXT STEPS

While much has been achieved, more research needs to be done. “Research tends to focus on systems, such as mangroves, rocky shores and oyster reefs,” Williams said. “But as we know more about species and habitats we need to know how they function. What happens, for instance if we lose one species or habitat, what effect will that have in terms of how our natural systems function?”

He also remarked on the one facility that is missing – a natural history museum to record and display Hong Kong’s biodiversity, with the accompanying expertise in taxonomy that is concentrated in such institutions. The demands on taxonomists have increased globally, as ecologists extend their surveys and discover more species.

“If species are not named they do not formally exist, and therefore cannot be protected,” Williams said. “The science of naming and describing species is a continuous process as we learn more about how species are related and have evolved. I have worked on a tiny snail (Echinolittorian malaccana) found high on Hong Kong’s rocky shores that has had its name changed three times in the past 30 years.”

Reflecting the growing recognition in the university and wider community of the importance of marine biodiversity, SWIMS is undergoing an expansion, which will include new facilities for molecular biology, as well as a state of the art aquarium system. It will also have a biodiversity centre – a small museum dedicated to housing and documenting local species and also outreach to the Hong Kong public.

Combining forces – working with other universities, government and NGOs, and reaching out through education to engage the community – is the way forward, Williams said.

While significant challenges remain, he points to the growing awareness and enjoyment of the marine environment in the community – an essential step towards its better protection. “That is one major tick in the box for education, schools, universities, NGOs, and the government,” he said.

Among the most noteworthy avifauna in the area are the colonies of terns that find safe havens on rocky outcrops of Port Island, Kung Chau, and Shek Ngau Chau for their breeding grounds.

Hundreds of these aerobatic seabirds, mainly Bridled Terns (Onychoprion anaethetus), Black-naped Terns (Sterna sumatrana), and Roseate Terns (Sterna dougall), arrive in early summer from the tropics to raise their young. Their breeding sites are monitored by the Hong Kong government’s Agriculture, Fisheries and Conservation Department and the Hong Kong Bird Watching Society (HKBWS), while the birds have been given a helping hand with the installation of artificial nests that have boosted their breeding success on the “tern islands” within the Geopark area.

Little has been known about the migration routes and wintering grounds of these birds. But in 2019, the birdwatching society captured and tagged 110 adult and juvenile Bridled Terns, two fitted with satellite tracking transmitters. One captured for ringing had been first ringed on the Great Barrier Reef off the coast of Australia.

From this research, the society’s researchers have observed that a single bird ventured for food from the breeding site in Mirs Bay to south of Lamma and Lantau islands.

John Holmes, who has been photographing terns in Hong Kong for more than 30 years and is a member of HKBWS, said that their numbers were stable.

Bridled and Black-naped Terns are present from late April through to August, he explained. “Both are tropical species, which range from the Indian Ocean through to the Western Pacific, and from south China to tropical northern Australia.”

“They are challenging to photograph from a boat, as both boat and bird are moving.” Photographing on the islands is strongly discouraged, to avoid disturbing the birds.

Islands with their dramatic rocks and cliffs that render them uninhabitable for humans, and protected through the Geopark status, mean that in this area of Hong Kong many marine creatures, from corals to terns, can thrive.

View across the Mai Po Nature Reserve and Inner Deep Bay in the northwest New Territories. Photo: Andrew Sun

Marshes, mangrove stands, and mudflats are among the most biodiverse terrains of the local landscape. However, such bountiful lowland ecosystems are facing more pressures than higher land in maintaining their presence

Wetlands are like sponges, lying between land and water. According to the inter-governmental Ramsar Convention on Wetlands of International Importance, they store twice as much carbon as forests and through their ecosystem services are among the most productive environments for flora and fauna.

However, their flat terrains mean that they face the greatest competition with human needs for space, for housing, industry, agriculture and port infrastructure, particularly where they fringe large and expanding coastal cities, such as Hong Kong and its neighbours in the Greater Bay Area.

Hong Kong’s best-known wetlands are located in the northwest New Territories. Here lies an international marvel – Mai Po Marshes and Inner Deep Bay, which together host up to 80,000 birds, along with mammals such as the endangered Eurasian Otter (Lutra lutra), and numerous reptiles, amphibians, insects, and aquatic species, as well as the largest stand of mangroves remaining in Hong Kong.

Wetlands also encompass other areas under the definition of the Hong Kong government’s Agriculture, Fisheries and Conservation Department (AFCD). These include reservoirs (around 2,480 hectares), such as Plover Cove Reservoir, followed by aquaculture ponds (1,590 hectares), marsh (1,100 hectares), artificial drainage channels (720 hectares), rivers and streams (460 hectares), and wet agricultural land, the latter now covering only around 290 hectares.

There are, for example, extensive fish ponds in Lok Ma Chau; Lantau Island has the ecologically important Pui O River and mangroves – among others; and Long Valley near Sheung Shui has its fresh water wetlands now being converted to a nature park.

Unlike the mountainous terrain of Hong Kong’s country parks, wetlands can be drained and easily built upon, and are also subject to pollution purveyed through the waters that sustain them.

In the New Territories they have been used by humans for centuries, for living space, agriculture, aquaculture, and salt production, with land use rights and ownerships that complicate their management and control. More recently they have had to give way to new towns such as Tin Shui Wai, and transport infrastructure, such as the Sheung Shui to Lok Ma Chau Spur Line.

In its Biodiversity Strategy and Action Plan 2016-2021, the Hong Kong government acknowledges the importance of the wetlands that remain, as buffers for coastal protection, for the human communities that depend on them, and their ecological value. While they cover only five per cent of the city’s land area, they support more than 70 per cent of the bird species recorded in Hong Kong, it states.

But there are tensions as to how much should be saved from urban development, and whether the protection of sites important to wildlife goes far enough.

Professor Wong Ming-hung (Croucher Senior Research Fellowship 1997), Adviser to the Department of Science and Environmental Studies, Education University of Hong Kong (EdUHK), specialises in ecological restoration and ecotoxicology. Despite wetlands occupying only six per cent of the earth’s surface, he said, they support approximately 20 per cent of all living organisms. “Wetlands produce the richest communities of living organisms.”

Despite their importance, between 64 per cent and 71 per cent of these wetland areas were lost globally during the last century, according to the Ramsar Convention which provides a framework for action and international co-operation for wetland conservation. Further destruction of ecosystems is evident from the extensive coastal development since then.

Mai Po and Inner Deep Bay, encompassing a total area of 1,500 hectares, were designated a Ramsar site in 1995. The area is overseen by AFCD, with the Mai Po Nature Reserve managed by wildlife conservation organisation WWF-Hong Kong.

Wong, a former chairman of the Mai Po Management Committee, said: “Mai Po is one of the largest wetlands in southern China. The Hong Kong side is doing better than the Shenzhen side of Deep Bay. It is very important as a shelter and feeding area for migratory birds, including several endangered species, such as the Black-faced Spoonbill [Platalea minor].”

The Hong Kong government protects Mai Po, with access restricted to the nature reserve and seaward “core” of the Ramsar site, and development limited in the wider area. In addition, the Ramsar site includes five Sites of Special Scientific Interest.

The Town Planning Board has also designated a Wetland Conservation Area – covering the landward area of the Ramsar site – and Wetland Buffer Area for the Deep Bay area, with special guidelines to control development in the area, and a “no-net-loss” policy for wetlands.

New development in the buffer area is only allowed if it has an insignificant impact on the conservation area, in terms of ecology, drainage, sewage, and traffic.

To the south of Mai Po, the 60-hectare Hong Kong Wetland Park opened in 2006 as a consolation for the extensive wetlands lost to Tin Shui Wai. The park gives the public easier access to some of the wonders of Inner Deep Bay.

Migratory birds find their way to other coastal wetlands, such as Shui Hau, which has the largest mudflat on Lantau Island, as well as marshes, mangroves, intertidal sand, and rocky shores.

However, the 180-plus species that the area supports – including the endangered Horseshoe Crab (Limulidae) and birds such as the Rufous-necked Stint, (Calidris ruficollis) – have had to compete with the popularity of Shui Hau for clam digging, the focus of a WWF-Hong Kong conservation education campaign.

Emeritus Professor David Dudgeon, Chair Professor of Ecology and Biodiversity, University of Hong Kong, and current Chairman of the Mai Po Management Committee, said: “The latest data indicate that we lost one-third of all wetland areas between 1996 and 2020.” With the reservoir areas remaining unchanged, the proportion of marshes beyond Mai Po that have been lost “is very high indeed”. “There is no evidence that the rates of loss are declining,” he said.

Except for Mai Po, wetlands were poorly represented in protected areas, compared with the higher land in the country parks, he added.

For example, wetlands at Pui O had been degraded step by step, by illegal dumping and other human activities, he said. “This was a particularly interesting site because it was large and the buffaloes maintained wallows which seemed to enhance diversity of beetles, amphibians, and [others].

“But this type of progressive degradation has occurred across Hong Kong. For smaller sites, it leads to the loss of the entire site.”

Dudgeon and his former student Dr Ken So Ying-kin published research in 2020 in the journal Aquatic Conservation showing that Hong Kong’s abandoned paddy fields, now semi-natural marshes, had a greater biodiversity when grazed at low intensity by bovines, such as feral cattle and water buffaloes, than ungrazed sites. By keeping plants checked, bovines could play a greater role in conservation management, they advised.

So, now a post-doctoral fellow at HKU’s School of Biological Sciences, has conducted further research on the changing wetland areas. “The key issue is that most of the wetlands in Hong Kong are located on private land and do not receive any form of protection,” he said. “This is also the major cause of the rapid decline.

“For example, a marsh located in Lung Tsai [in the northwest New Territories] was filled and converted into a parking space in 2016 because it was not covered by any zoning plan.”

Lung Tsai marsh was only the tip of the iceberg. “Cases of wetland loss and destruction have been reported recurrently over the past few decades.”

WWF-Hong Kong has launched a project to map all of Hong Kong’s wetlands to inform their future protection. Andrew Chan Chung-ming, its Senior Conservation Officer, Policy, and Tobi Lau Siu-keung, Manager, Conservation Policy, will analyse satellite images of surviving coastal, inland, and man-made wetlands, and review how they have changed over a 30-year period.

Chan said: “The no-net-loss planning policy is only applied to Mai Po.” This had resulted in the massive loss to date.

Dr Sung Yik-hei, Assistant Professor of the Science Unit, Lingnan University, has undertaken such a comparison for wetlands in the Ramsar area. This showed intertidal mudflats had been encroached on by mangroves, and a recent decline in aquaculture. “In general, the habitat change is not that great compared with other areas,” he said. “But the coverage of fish ponds outside the area has declined a lot.”

EdUHK adviser Wong said: “We have wetlands in different parts of Hong Kong that are not so well preserved. But they are also very important.”

He is among those who have focused their research not only on strategies to preserve existing wetlands and safeguard them from pollution, but to add to them by pioneering the use of constructed wetlands. He has used this approach for the Hong Kong government’s Drainage Services Department in Ta Kwu Ling, near the Ping Yuen River in the New Territories, to purify wastewater for villages not connected to main sewage treatment plants, and create habitats for different flora and fauna.

One area that has been saved is Long Valley, near Sheung Shui, the largest contiguous freshwater wetland of high ecological value in Hong Kong, according to Michael Wong Wai-lun, Secretary for Development, who wrote on the area in his April 2021 blog.

Long Valley farmland. Photo: Thomas Gomersall

Two decades ago, the valley faced destruction to make way for the MTR’s Lok Ma Chau spur railway line. However, conservationists successfully blocked the plan. A tunnel now runs under the wetland instead.

Since 2005, the Conservancy Association and Hong Kong Bird Watching Society (HKBWS) have been contracted to manage the site as an agricultural conservation area, helping farmers switch to organic farming, and safeguarding habitats for birds. Its rice paddies are a popular feeding ground for the Black-winged Stilt (Himantopus Himantopus) and Yellow-breasted Bunting (Emberiza aureola), while elusive Painted Snipe (Rostratulidae) are occasionally seen, emerging from its reed beds.

Now this wetland, which was resumed by the government in 2019, is in the process of being remodelled as a 37-hectare nature park and green space for the Kwu Tung North and Fanling North New Development Area. The park, due to be completed in 2023, will include a biodiversity zone of about 21 hectares, agriculture zone of 11 hectares, and visitor zone of five hectares.

Development Secretary Wong wrote of the plan: “The Government has been committed to striking the right balance between development and conservation with a view to providing a large green space in a new town to create a quality living environment.”

He stressed that the construction team was taking care to protect the ecology during the works, for example, by avoiding the use of heavy machinery that would disturb roosting birds, based on advice from the Conservancy Association.

Yu Yat-tung, Senior Research Manager of HKBWS, welcomed the decision to conserve Long Valley as a wetland. “It is definitely a good thing. It is better than doing nothing,” he said. But he is worried that too much emphasis would be placed on creating a “very clean environment”, as many city-dwellers have come to expect.

WWF-Hong Kong’s Chan, who also vets planning applications and Environmental Impact Assessments and handles reports from the public of illegal land uses, said that despite the management agreement that had protected Long Valley, too many wetlands outside the area had been destroyed, commonly being turned into open storage areas, container parks, or building plots for small houses.

Freshwater marshes on Lantau Island, which are a habitat for Romer’s Tree Frogs (Liuixalus romeri) and wetland birds, had also fared badly. “This is another spot we are concerned about. Wetlands have been destroyed by land filling and dumping of construction waste that cannot be controlled,” he said.

Yu and other conservationists see the need for more awareness of the importance of these sites. “People think wetlands are just pieces of mud, and dirty,” Yu said. “They don’t like [them]. But these habitats are always important.”

“We need to promote the outdoor life,” he said, adding that more discipline was also needed in the way people observed nature and enjoyed these wetlands, with the interests of birds and other wildlife put first.

Conservation Management

Dunlins (Calidris alpina) in flight with Eurasian Wigeons (Mareca penelope) below, taken from a Mai Po boardwalk hide overlooking Deep Bay. Photo: John Holmes

The 380-hectare nature reserve and larger Inner Deep Bay Ramsar site it sits within have proved a biodiversity beacon for wildlife and the human managers who seek to sustain wetland areas in Hong Kong and the wider region

Even along the short walk from a car park to the gate at the entrance to the Mai Po Nature Reserve, wildlife is more readily seen than elsewhere in Hong Kong.

Perhaps a Little Grebe (Tachybaptus ruficollis) – like a tiny duck – swims and dives on a roadside fish pond, Grey Herons (Ardea cinereal) fly overhead, Great Egrets (Ardea alba) give raucous calls and fly off as humans approach, and Great Cormorants (Phalacrocorax carbo) – large, black birds that also feed on fish – are perched on wires and trees.

Within the reserve, hundreds more egrets and herons, including an occasional Purple Heron (Ardea purpurea), hunt in shallow ponds, which in winter also attract flocks of ducks, and in spring host thousands of shorebirds in transit to breeding grounds as far north as the Arctic Circle.

The 380-hectare area is a key component of the larger Mai Po Inner Deep Bay Ramsar Site that extends to 1,500 hectares comprising a shallow bay, mudflats, intertidal mangroves, and gei wais (traditionally managed shrimp ponds).

Approaching the bay, the visitor leaves the nature reserve and crosses to the rest of the Ramsar site in the border control zone between Hong Kong and Shenzhen, forested by semi-submerged mangroves.

Towards the end of the 540-metre floating boardwalk, a cacophony of bird calls – Whimbrels (Numenius phaeopus) and Eurasian Curlews (Numenius arquata) among the most distinctive – signal arrival at the mudflats. At low tide, thousands of waterbirds will be foraging on mudskippers, crustaceans, bivalves, and worms, taking wing en masse when startled by a predator, or to move with the changing tide.

Aerial illustration indicating the location and reach of the Mai Po Inner Deep Bay Ramsar Site. Source: WWF-Hong Kong

The Ramsar site is a place of incredible biodiversity. The Mai Po Nature Reserve alone is home to 25 different types of mammals, including Eurasian Otters (Lutra lutra), Small Asian Mongooses (Herpestes javanicus), and Leopard Cats (Prionailurus bengalensis), 21 species of reptiles, and over 1,000 kinds of invertebrates.

But by far the most numerous and easily seen taxa are the birds, representing over 415 species and supported by a diverse mix of habitats: mudflats, reedbeds, brackish-water gei wais, and mangroves.

It is Inner Deep Bay and Mai Po’s importance for these birds that has helped spur measures to protect the wetlands. The Ramsar site supports up to 80,000 wintering waterbirds and another 20,000-30,000 that pass through during their annual migration along what is known as the East Asian-Australasian Flyway in spring and autumn, to feed and rest within the area, according to WWF-Hong Kong.

Some, such as the Black-faced Spoonbill (Platalea minor), spend all winter there. Others, for example, the critically endangered Spoon-billed Sandpiper (Calidris pygmaea), only rest en route to other destinations.

Protecting Hong Kong’s Ramsar site habitats for maximum ecological value are its two main managers: the Hong Kong government’s Agriculture, Fisheries and Conservation Department (AFCD), which has overall responsibility, and WWF-Hong Kong, which manages the Mai Po Nature Reserve and an area of the Inner Deep Bay mudflats.

“Wetlands are very dynamic ecosystems. If you leave them on their own, they will eventually succeed into marshland and then dry land. So they have to be managed,” Dr Eric Wikramanayake, Director of Wildlife and Wetlands at WWF-Hong Kong, said of the natural process of succession of wet to dry land.

The history of the area is rooted in how the wetlands have been managed over the centuries, with agriculture, aquaculture, algae collection, and salt production among their major uses.

The gei wais – the signature habitat of the wetlands – were in fact not built until after the Second World War, when mainland immigrants brought with them their traditional techniques for rearing shrimps. Sluice gates were installed to allow seawater from the bay to flow into the ponds with the tide, bringing in shrimp and fish fry, which were raised to maturity in the enclosed areas.

As the mangrove-fringed gei wais attracted more birds, this remote area became a location for birdwatchers seeking species that were hard to find elsewhere.

In the 1970s, fears that the planned construction of the Fairview Park housing estate could threaten the marshes prompted birdwatchers Mike Webster and Fred Hechtel to petition the government to protect the area, which was declared a Site of Special Scientific Interest.

Soon afterwards, conservationists joined together to establish a local office of what was then named the World Wildlife Fund. That office, now WWF-Hong Kong, decided that rather than raise funds for the headquarters in Switzerland, they should assist projects in Hong Kong, the first of which was managing Mai Po Wildlife Education Centre and Nature Reserve, with the support of AFCD.

In autumn 1983, with initial funding from the Hong Kong Jockey Club, WWF-Hong Kong started to develop and manage the Mai Po reserve, including the building of a visitor information centre and concrete footpath. The first guided visits for schools and the public were organised in 1985. Other early developments encompassed the innovative floating boardwalk, leading along a creek through a belt of mangroves to a viewing hide overlooking mudflats along the southern shore of Deep Bay, outside the reserve but also now looked after by WWF-Hong Kong.

In addition to the Hong Kong government’s listing of Inner Deep Bay under the Ramsar Convention in 1995, it was designated internationally as an Important Bird Area in 2004.

Under the Convention, Hong Kong must strive for wise use of the wetlands, defined as “the maintenance of their ecological character, achieved through the implementation of ecosystem approaches, within the context of sustainable development”.

As such, fish ponds around Mai Po could continue operating, while making it harder for developers to obtain permission to transform areas into housing developments. But in itself, the Ramsar listing does not secure the future of the wetlands, which are always changing, and require small-scale and large-scale management.

On a day-to-day level, management involves a raft of maintenance measures to retain favourable habitats for birds and other wildlife, as Fion Cheung, Flyway Planning and Training Manager of WWF-Hong Kong’s Mai Po team, noted.

Such activities can range from controlling vegetation by enlisting the help of buffalos to keep reeds and grass under control to the provision of feed to attract more wild ducks, when the numbers flying in for the winter inexplicably declined in recent years, as well as monitoring the numbers of birds.

The reserve also has some of the last of Hong Kong’s functioning gei wais. These ponds are drained and cleaned, and water levels managed, for the benefit of the birds that enjoy rich pickings as water is lowered and sediment revealed.

Meanwhile, the nature reserve overall is guided by the Mai Po Management Committee. This includes government officials, wetland management experts, environmental scientists across Hong Kong’s universities, and members of other conservation NGOs, and is chaired by Emeritus Professor David Dudgeon, of the University of Hong Kong’s School of Biological Sciences.

“The foresight of the founders was very considerable, especially given the extent of coastal development elsewhere in southern and eastern China,” Dudgeon said.

Today, as well as its role as a wildlife haven, the Mai Po Nature Reserve and Ramsar site play a significant role in conservation education for visiting students and the public.

Further afield, the areas serve as beacons for wetland management practice and training for the wider region, enabling Hong Kong to soar in promoting better conservation practices beyond its shores.

The Mai Po team faces a continuous challenge to protect the wetlands, from short-term risks such as feral dogs and even drones that disturb and endanger birds, to the longer term impact of climate change, expected to prompt radical shifts in the ecosystems as sea levels and storm surges rise.

“We need to think about how to build an adaptation strategy to ensure that the wetlands in Mai Po and [Deep Bay] are conserved for the future. We need to be much more proactive and forward looking in our approach,” Wikramanayake said.

“If you look at the climate change trajectories and what’s happening in the push for land conversion, it does paint a pessimistic picture. But we have to be optimistic.”

Local Decline

Fewer Black-faced Spoonbills (Platalea minor) are now seen in Hong Kong even though numbers are increasing in other locations. Photo: John Holmes

It is a species that is an icon of Mai Po Nature Reserve and a testament to the conservation value of the Mai Po Inner Deep Bay Ramsar Site in the northwestern New Territories. Yet annual surveys show that many Black-faced Spoonbills (Platalea minor) are now shunning Hong Kong, despite significant increases in the numbers of this endangered wading bird elsewhere around the region.

Less than 30 years ago, nobody knew the Black-faced Spoonbill, which spends its winters around intertidal mudflats on the eastern fringes of Asia, was endangered. In the 1990s, it was assumed to be a common species, similar to other spoonbills.

But Hong Kong-based birdwatcher, Peter Kennerley, wasn’t so sure. On compiling records from across the bird’s range, he found there were only 288 left in the world, and Deep Bay was a vital wintering site for them.

This prompted the listing of the Black-faced Spoonbill as a globally endangered species by the International Union for Conservation of Nature (IUCN), and influenced the designation of Mai Po Inner Deep Bay as a protected Ramsar site in 1995, making it one of the only government-protected wetlands within the bird’s range at the time.

The listing also prompted greater research on spoonbills, which in turn helped to inform WWF-Hong Kong, the conservation group that manages Mai Po Nature Reserve, on how best to manage the habitat to encourage these birds.

In addition, international conservation efforts within the East Asian-Australasian Flyway Partnership, including key roles by WWF-Hong Kong and the Hong Kong Bird Watching Society (HKBWS), have paid off. The global population of the Black-faced Spoonbill has risen an average nine per cent annually since 1994 to a record 5,222 individuals, as revealed in the partnership’s 2021 survey across more than 100 sites in East Asia.

“The number of Black-faced Spoonbills worldwide has reached a new high,” said Yu Yat-tung, Senior Research Manager of HKBWS, which took the lead in organising the survey. “The numbers in Japan, Vietnam, and Taiwan have even broken records, indicating the success in regional conservation.

“However, we are concerned about the continuous decline in Hong Kong. The story behind this must be related to the health of the ecosystem,” he said, referring to the damaging impact of urban development and loss of mudflats and fish ponds in the wider Deep Bay area.

Coming home to roost in Mai Po. Photo: Wei Shyy

Taiwan is now the most popular wintering destination, with a total of 3,132 identified in the 2021 survey, 60 per cent of the global total. This involved an additional 347 individuals, a 12.5 per cent increase over 2020.

Yet the numbers in Deep Bay, including Hong Kong and the Shenzhen side, declined by almost seven per cent, to 336 individuals, and have dropped by 15 per cent in the last seven years. “Hong Kong set up an example for other wetland areas in the region,” Yu said. “Some followed and learned from our experience. Now they have better results than us.”

Yu, who also coordinates the Black-faced Spoonbill Working Group for the East Asian-Australasian Flyway Partnership, is proud of the success beyond Hong Kong, with Mai Po Nature Reserve doing much to support the spoonbills. “It is an important roosting site,” he said.

However, the birds also need to feed outside the reserve, including the mudflats – their natural feeding site that is replenished with shrimp and fish with each tide – and human-related wetlands, including fish ponds.

Dr Sung Yik-hei, Assistant Professor of the Science Unit, Lingnan University, has collaborated with Yu in analysing the population trends, in a paper published in Bird Conservation International in 2018.

Sung’s team found population increases were more pronounced in protected sites and areas with low levels of human disturbance, indicating that control of such disturbance is crucial for conservation of this species.

While the behaviour of the bird, which breeds on the west coast of North Korea, is well documented, Yu said, more research is needed to understand its interaction with the environment.

Dr Simon Sin Yung-wah (Oxford Croucher Scholarship 2008), Assistant Professor at the University of Hong Kong’s School of Biological Sciences, has provided some of this further understanding through an investigation of the diet of Black-faced Spoonbills.

The study was done through DNA analysis of about 100 spoonbill faecal samples gathered from different roosting groups, in Mai Po Nature Reserve and Lok Ma Chau.

The birds, which use their long spoon-shaped bills to scoop for prey, were found to enjoy a diverse diet of fish and crustaceans common in the different habitats they use – both mudflats and fish ponds.

Diet was found to vary between the groups, indicating that individuals within a roosting group tended to forage together. “We can provide baseline information on their foraging ecology, so we know the fish they feed on,” Sin said.

The forthcoming publication could inform future monitoring of the abundance and availability of their major prey, and comparison between habitats within and beyond Hong Kong.

Regional Reach

On the move: shorebirds take off from Inner Deep Bay mudflats. Photo: Katherine Forestier

As coastal wetlands come under threat from human activities, Hong Kong’s role as a wintering ground or stopover for over 80,000 migratory birds each year is increasingly important.

Stretching 13,000 kilometres from the Arctic Circle to Australia and New Zealand, the East Asian-Australasian Flyway (EAAF) is a superhighway for migratory birds.

Each year, over 50 million avian travellers, mainly waterbirds, fly between a network of coastal wetlands where they rest, feed, and sometimes breed, with Hong Kong an important stopover or wintering ground mid-way.

This migration is one of nature’s great evolutionary wonders, with the EAAF one of nine major north-south flyways around the world.

Some birds, such as the Bar-tailed Godwit (Limosa lapponica), a wader that feeds in shallow waters, can fly all the way from their summer breeding grounds in Alaska to New Zealand with barely a rest, though some may be seen feeding in the Deep Bay mudflats on their way, particularly in spring.

But without an interconnected chain of wetlands, which includes the Mai Po Inner Deep Bay Ramsar Site and other destinations in Hong Kong, many would not be able to complete their journeys, or be seen in vast flocks filling the skies and mudflats between northwestern Hong Kong and Shenzhen.

While the Hong Kong stopover site is protected through WWF-Hong Kong and Agriculture, Fisheries and Conservation Department (AFCD) management of the Mai Po Nature Reserve and Ramsar site stretching into Inner Deep Bay, the interconnections are under threat as other coastal wetlands along the flyway are lost to urban development.

Hunting, pollution, and climate change are also taking their toll on bird species.

According to an International Union for Conservation of Nature (IUCN) report, published in 2012, more than 80 per cent of East and Southeast Asia’s wetlands were already classified as threatened from being converted, fragmented, and degraded by anthropogenic drivers. And this had resulted in population declines in 88 per cent of waterbird species using the flyway.

Governments along with intergovernmental agencies and NGOs and other organisations came together in 2006 to try to protect important habitats, through the voluntary East Asian-Australasian Flyway Partnership.

WWF-Hong Kong was among them, and in 2020 it launched the Asian Flyways Initiative to coordinate wetland conservation projects with its partners.

Research by ecologists and networks of ornithologists plays an important role in broadening understanding of the EAAF, the behaviour of birds, and the threats they and their habitats face.

Hong Kong has contributed extensively to this knowledge. Systematic surveys by trained Hong Kong Bird Watching Society (HKBWS) members, along with WWF staff, have been conducted in Mai Po since 1998, with funding from the Hong Kong government. Monthly winter counts take place during high tide, when birds have retreated to their roosting sites in and around Mai Po’s network of fish ponds, or gei wais.

This is supplemented by bird-ringing programmes, and some satellite tracking, to learn more about their migrations and the habitats they rely on.

Xianji Wen, Director of Mai Po Nature Reserve and Flyway Programme, said: “Every year in the winter, HKBWS records around 60,000 to 80,000 wintering birds here, and every spring and autumn another 20,000 to 30,000 passage migrants will pass through Mai Po and Deep Bay.”

However, the composition of the birds in terms of numbers and species was changing, he said. “Some are more common than before but most of them are declining.”

The Hong Kong surveys, along with those carried out elsewhere along the China coast since 2005, have enabled researchers to analyse changing trends among birds in the Deep Bay area, and identify threats there and elsewhere along the flyway where conservation efforts are needed.

Research, published in 2021 and led by Dr Sung Yik-hei, Assistant Professor of the Science Unit, Lingnan University, found that of the 42 waterbird species wintering in the Deep Bay area between 1998 and 2017 and included in their study, 12 declined, while nine had increased significantly.

Declining birds, such as the Dalmatian Pelican (Pelecanus crispus), Common Sandpiper (Actitis hypoleucos), Green Sandpiper (Tringa ochropus), and four species of duck, were found to co-relate with flyers reliant on the Yellow Sea, and of larger size. Meanwhile, those that breed in southern Siberia decreased more than those breeding in East Asia.

“There is a consensus that species dependent on the Yellow Sea area are in greater trouble,” Sung said. “There is probably not a single cause – pollution, habitat loss and degradation, and invasive species, among them.” Shooting wildfowl for food is a further issue.

“Ducks have experienced a drastic decline,” he said. Thousands of the Common Shelduck (Tadorna tadorna), for instance, used to be seen in Mai Po. “Now it is one or two.”

Yu Yat-tung, Senior Research Manager at the Hong Kong Bird Watching Society, said that the EAAF Partnership was making a difference, through the exchange of information and practices. “We have information that the situation in the Yellow Sea has improved a little in the past few years,” he said. “We must acknowledge the efforts of governments. Many are working to save coastal wetlands.”

Sung and his co-authors point out that increases in birds such as the Common Greenshank (Tringa nebularia), Great Knot (Calidris tenuirostris), and Black-winged Stilt (Himantopus himantopus) in Deep Bay are not necessarily due to an overall rise but changing habitat use: more may come to Deep Bay as other wetland habitats in the area are being lost.

Wen and other conservationists are concerned about the birds that are now less frequently seen in Deep Bay. “The last record of Dalmatian Pelicans [Pelecanus crispus] was about 10 years ago. Every year, we would get about 10 individuals wintering in Deep Bay. But right now, it is very rare,” he said.

Recent research, based on field observation records of 57 species, found that less than 10 per cent of the inland and coastal areas used by waterbirds on the flyway are protected, and only five per cent of the areas with the highest 10 per cent in species richness.

This paper, first authored by Dr Li Jia, then a PhD student at the University of Hong Kong (HKU), with Dr Alice Hughes, Associate Professor, Centre for Integrative Conservation, Chinese Academy of Sciences, and Li’s supervisor, Emeritus Professor David Dudgeon, Chair Professor of Ecology and Biodiversity at HKU, concludes that the richness of the EAAF may have been underestimated, and identified a need to increase the protected areas. It was published in 2019 in the PLOS ONE science journal.

Dudgeon said: “Maybe the loss of sites to coastal development along the flyway has meant that birds are now using suboptimal sites that they might not have used before.” A better system of protecting sites that birds use along the flyway was needed.

“We also need to know how many of the sites being used will be lost to rising sea levels or planned coastal reclamation,” he added.

Hong Kong expertise is playing an important role not just in protecting Mai Po, but other wetland sites along the flyway. For example, WWF-Hong Kong has run the Wetland Management Training Programme since 1990 for wetland managers from across the flyway, including Mainland China. This covers techniques such as invasive plant removal, water level management for wading birds, and how to make target-based conservation plans, Wen explained. The programme also offers courses in environmental education and eco-tours, which are seen as crucial for gaining the community support needed for successful conservation.

To date, WWF-Hong Kong has trained over 5,000 people, some of whom have gone on to senior management positions. This has had real, tangible results for conservation, as several of these people have been inspired to help create new wetland reserves, Wen said.

For example, a group of Thai wetland managers who attended the WWF programme set up Bang Pu Nature Education Centre, a wetland conservation area near Bangkok that draws heavily from Mai Po’s example.

Several Mai Po-inspired reserves have also been established in the Greater China area, namely Quanzhou Bay Estuary Wetland Nature Reserve and Minjiang Estuary National Nature Reserve in Fujian Province, Hebei Luannan Nanpu Zuidong Provincial Wetland Park, as well as Guandu Nature Park in Taiwan, according to Wen.

Others have modified their strategies based on Mai Po’s approach, benefiting species such as the Black-faced Spoonbill (Platalea minor).

Wen said: “Other wetlands in the Greater Bay area also seem to have taken a cue from Mai Po for their management strategies and contributed to the recovery of the Black-faced Spoonbill. So in that way, Mai Po has contributed to conservation in other parts.”

WWF is leading further action to conserve wetlands, through its Asian Flyways Initiative. This aims to empower greater cooperation between all EAAF regions, through training and advice for wetland managers, and identifying important sites where greater protection for birds is needed.

Travel and funding restrictions due to the COVID-19 pandemic have limited the AFI’s impact in its first year. But that is not clipping their wings.

“We are regrouping now and adapting,” Dr Eric Wikramanayake, Director of Wildlife and Wetlands at WWF-Hong Kong, said. “We have been able to mobilise network support across AFI countries and are forming teams – both regional and national – to identify priority spaces and develop project proposals with innovative strategies such as nature-based solutions.

“So we are moving the needle, given the constraints, albeit slowly,” he said.

Biodiversity hotspot

Kandelia obovata, one of the resilient species of mangrove remaining in Hong Kong. Photo: Stefano Cannicci

Research is highlighting the novel and numerous species that rely on Hong Kong’s last mangrove stands as the trees’ battle to survive the changes to their coastline habitats amid urban development and pollution

Not many decades ago the Pearl River Delta was fringed by mangroves, but today, most of these squat, salt-tolerant trees have been lost to human development.

Yet it is Hong Kong that is the refuge for the last major remaining functioning systems in the area, according to researchers.

Mangroves, found around sheltered tropical and subtropical coastlines, are sandwiched between land and sea, their roots bathed in tidal waters. And research on the many ecoservices they provide has highlighted the importance of stemming the tide of their destruction.

Dr Stefano Cannicci, Associate Director of the Swire Institute of Marine Science at the University of Hong Kong (HKU), has taken the measure of these ecological “sentinels”, having led the most comprehensive survey conducted in Hong Kong of their distribution and the fauna that lives among them.

This survey, completed in 2019, covered Hong Kong’s 59 surviving mangrove stands, distributed across 510 hectares in the coastal areas of Deep Bay, Sai Kung, Northeast New Territories, Tolo Harbour, Lantau Island, and Hong Kong Island. The Mai Po area hosts the largest of the forests.

While Hong Kong, like the rest of southern China, has lost most of its mangrove cover to reclamation and development, Cannicci describes what is left as “truly resilient”, despite the stresses and threats it faces from pollution and invasive species.

His team surveyed the distribution of the eight “true” mangrove species, that is halophytes that grow in water or soil of high salinity as opposed to “mangrove associates” that have some salt tolerance. They included the three most abundant – Kandelia obovata, Avicennia marina, and Aegiceras corniculatum – along with Acrostichum aureum, Excoecaria agallocha, Heritiera litoralis, Bruguiera gymnorrhiza, and Lumnitzera racemosa.

The two-year project, funded by the Hong Kong government’s Environment and Conservation Fund, found an exceptional range of creatures, including several species new to science.

The team identified 52 species of brachyuran crabs, one of the highest diversities of mangrove crabs in the world, and including six new records for Hong Kong. As many as 42 species of gastropods were found, including one new local record, and 329 species of insects, of which eight were new to science and 42 new to Hong Kong.

Among the crabs, the poorly known Sesarma (Holometopus) tangi found in Hong Kong was revealed to have unique features distinguishing it from the Neosarmatium genus, with which it had previously been identified. The team concluded it was worthy of a new genus, which in a paper published in 2020 in the Journal of Crustacean Biology they named Sinosesarma.

“The differences are linked to the sculptures and ridges found on the claws, which are of importance for reproduction, since males attract females rubbing those ridges to produce sounds,” Cannicci said.

Dr Benoit Guenard, Associate Professor at HKU’s School of Biological Sciences, led the insect investigations. Among the insects new to science were two new species of long-legged flies, one now named Raphium canniccii, after Cannicci, in a paper published in 2019 in the European Journal of Taxonomy.

So far, the team has DNA barcoded 58 and 43 species of brachyuran crabs and gastropods, respectively. “This is the most complete and updated list of DNA sequences ever obtained for Hong Kong mangrove fauna,” they wrote in their report.

The DNA is preserved in the laboratories of the School of Biological Sciences at HKU and the sequences will be shared online.

A collection of keystone mangrove invertebrates, such as micro-mangrove climbing crab Haberma tingkok, a climbing crab endemic to Hong Kong, and marsh crab Orisarma neglectum, which was known only from wetlands of East China and is important in terms of the bioturbation of sediment, will be added to the new Biodiversity Centre due to be opened by SWIMS this year as part of its expanded facilities.

While the mudflats, rather than mangroves, are the major feeding grounds for the flocks of wading birds seen in Inner Deep Bay, the trees still form a vital part of the ecosystem supporting the East Asian-Australasian Flyway migratory route, by nourishing the birds’ food supplies. In addition, they shelter egrets and herons, among others.

“The worms and bivalves live on these depositions – the nutrients and decaying leaves washed on to the mudflats,” Cannicci said. They also filter the water of pollutants.

“The good thing in Hong Kong is no one is exploiting them,” said Cannicci, who moved to Hong Kong in 2015. In some African countries, such as Mozambique and Kenya, where he had previously conducted research, many have been stripped for housebuilding and boats.

“The real problems in Hong Kong are pollution and coastal development,” he said. For example, plans to develop the north coast of Tolo Harbour for recreation, including a constructed beach, would change the currents and waterfront adjacent to the mangroves of Ting Kok, the second largest stand after Mai Po.

Hong Kong’s mangroves are heavily polluted, due to materials and substances ranging from construction waste and plastic bottles to microplastics and heavy metal contaminants.

Despite the protection afforded by its status as a Ramsar site (a wetland area designated to be of international importance under the Ramsar Convention), Mai Po’s mangroves are subjected to more cadmium pollution than other stands, from factories on the fringes of Deep Bay.

“The mangroves keep the heavy metal in the root so are not so affected. But the pollution is exploding in the sediment and fauna, which are also food for the birds on the flyway,” Cannicci said.

Research published in 2020 has investigated the impact of microplastics on mangrove ecosystems. From 49 crab specimens gathered from three mangrove sites, in Pak Tam Chung and Yung Shue O in the east, and Ha Pak Nai in the west, Cannicci and his team retrieved almost 3,000 microparticle pieces in the stomachs and gills of the creatures. These ranged from paint and cobalt to rayon fibres and polyethylene.

As microplastics accumulated in the food chain, birds such as plovers feeding on these crustaceans would have their feeding impaired by the quantity of the anthropomorphic debris they may consume, he said.

Cannicci works closely with fellow mangrove specialist Professor Joe Lee Shing-yip, of the Chinese University of Hong Kong’s Simon F.S. Li Marine Science Laboratory.

Lee has been visiting Mai Po since 1985, especially to study the mangroves that are the dominant feature of Inner Deep Bay, and he has witnessed increasing sedimentation within the bay area.

“The mangroves are becoming drier and drier, with less inundation by the tide,” he said. “I didn’t see a lot of understorey growth 35 years ago, but now Acanthus [Mangrove Holly] is common in the understorey, except the very seaward part.”

While sedimentation is natural, Lee said it has been exceptionally fast at Mai Po, and perhaps linked to high sediment loads as a result of urbanisation. He predicts the currently open expanse of mudflats in front of the boardwalk bird hides will be colonised soon.

The seaward edge of the mudflats won’t move, as there are navigation channels in the middle of the bay. “This means the area of inundated mudflats is becoming smaller, and smaller, and so too is the capacity of Mai Po mudflats to support shorebirds,” said Lee, who along with Cannicci is a member of the Mai Po Nature Reserve Management Committee and the International Union for Conservation of Nature (IUCN) mangrove specialist group.

Meanwhile, decades of development have been followed by some new planting of mangroves along the China coast, including Hong Kong, though these are yet to become fully functioning systems. “The mangrove area may have increased slightly in the past 10 to 20 years,” Lee said. “But the ecosystem functions of plantations with young trees are less than for more diverse, well established mangroves.”

Lee noted that as well as hosting birdlife, mangroves support offshore fisheries, as they are refuges where juvenile fish can grow, relatively safe from predation.

In Hong Kong’s mangrove communities, these ecosystem services are being reduced by the arrival of exotic mangroves such as Sonneratia, from South Asia, which was introduced in Shenzhen and elsewhere as it grows rapidly.

“Our research suggests that Sonneratia is not as beneficial as was thought,” Lee said, a concern he shares with Cannicci. “While above ground, it may grow to twice the height of our native species, if you look deeper, the native species have a lot more roots, which make them a lot better at carbon storage and protecting coastlines.”

Cannicci added that “huge efforts” were under way by government agencies such as the Agriculture, Fisheries and Conservation Department (AFCD) to remove the invasive species – a challenging task given how easy it is for the seed-carrying mangrove apples of Sonneratia to float from one area to another.

Mangroves are not only important for fauna, but humans. They are now recognised as allies in defending coastal areas from the impact of climate change, by protecting them from storm surges.

By storing carbon in their roots and sediment, they can also help reduce carbon in the atmosphere.

“They accumulate a lot of carbon in the soil. But it is dynamic storage. If you cut the forest, you release methane, which is 20 times worse than carbon in terms of greenhouse gas potential,” Cannicci said.

Sea level rise alone should not be a problem, as in theory they can re-establish themselves within the new intertidal zone. But if that space is already occupied by development such movement will not be possible.

“Mangroves are so threatened by so many things that they could be destroyed long before climate change affects them,” Cannicci said.