The verdant pastures and wetlands around Pui O make it an ideal home for Hong Kong's largest herds of water buffalo. However, development is likely to see them vanish as the green lung deflates.

"These buffalo will be gone in 10 years," says Leung, sadly, as she strokes Ngau Ngau's hide. "The government is not doing enough to protect them, nor are the villagers."

Ngau Ngau happily chomps his way through a bucket of banana leaves while two other buffalo mosey up to Leung, to grab a mouthful of fruit. They are all blissfully unaware that the ground on which they walk is at the centre of an escalating row, and that their future hangs in the balance.

Over the past eight months, construction waste has been dumped over four separate plots in the wetlands of Pui O, land designated as a "coastal protection area". Dumping of waste on such land is prohibited, as is nearly all construction. However, the government's interpretation of the law means it's nigh on impossible to stop the rubble rising.

"The villagers want to protect their development rights but this area here is meant to be protected," says Leung, indicating the fields that lie in the open valley behind Pui O beach. "However, villagers don't think that way. They shoo the cattle off the land and then concrete it. Then it's of no use to the buffalo and no longer worth protecting."

, is not indigenous to Hong Kong. Members of the species were brought here in the mid-1900s to work on paddy fields. Their power and waterproof skin make them perfect for ploughing alluvial coastal plains to cultivate rice. As Hong Kong developed rapidly in the 70s and 80s, and shifted towards manufacturing, farming declined. The buffalo were no longer needed and were gradually abandoned to fend for themselves.

The remaining buffalo are now feral and, as such, have no official owners, although the Agriculture, Fisheries and Conservation Department is responsible for managing them.

"According to a territory-wide population survey on stray bovines conducted by the department in 2013, there were around 120 feral buffalo in Hong Kong," says Esther To Man-wai, the department's senior veterinary officer. She is in charge of the department's Stray Cattle and Buffalo Management Plan and its Cattle Management Team. "Most of them favour wetlands and dwell mainly in lowland areas."

Eighty-three of these animals live on Lantau; the rest can be found around Yuen Long, in the New Territories.

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Water buffalo weigh between 400kg and a ton and stand up to 1.6 metres high. They live for about 25 years and are generally social animals, staying in family groups. One bull will form a herd, with between one and three cows and their calves. Bulls that are not successful in forming a family herd will congregate in a bachelor herd. Each year, other males compete with the alpha animal in a herd to become the dominant bull and take the group. On Lantau, there are three breeding herds and three bachelor herds.

"Even though they may not be indigenous, I am in favour of keeping the buffalo as part of the biodiversity of Hong Kong," says Howard Wong Kai-hay, one of To's predecessors and now the executive director of the School of Veterinary Medicine at City University. "They have been here for quite a while now and are part of the flora and fauna.

"Obviously, when you're in government, you've got people who want them there and people who don't want them there and you're in the middle. So, what we thought was, 'Let's develop a policy where we try and pay heed to the desires of both parties in a sense that we don't think we should remove them completely from Hong Kong but we don't think they should reproduce out of control either.'

"The idea was to manage the population at the level that existed in 2011 and not let it grow further while not culling them for no reason, either. So, we set up a cattle team to try to manage the behaviour, to decrease the amount of trouble the buffalo and cattle cause to people who don't want to see them. Sai Kung Buffalo Watch [the name is correct even though Sai Kung has no water buffalo, only feral cattle] and the Lantau Buffalo Association were also involved with volunteers and we all worked together."

Wong thinks the government's handling of the buffalo and other bovids in Hong Kong has been exemplary: "Government rarely comes up with policies that are reasonable and appeal to both sides. Too often we have a knee-jerk reaction - trying to eliminate the problem rather than manage it. People manage populations of wild animals all over the world, why should Hong Kong be any different? As [we had] a reasonable response, it got a lot of support."

Ho Loy, chairwoman of the Lantau Buffalo Association, which was set up in 2004, explains how the beasts, which need a wetland habitat in order to wallow to cool off and escape insects, provide a unique service.

"Water buffalo are unique in that they can restore the condition of abandoned farmland," says Ho. "If you just leave abandoned farmland it collects garbage and plants that don't provide biodiversity. Buffalo restore water to the environment and the way they churn up the land with their hooves and horns encourages plants and wildlife that provide a water purification and filtration aspect.

"If you look at all the rural environments in Hong Kong, abandoned farmland is always between the natural water source and the village area. The buffalo provide an eco buffer zone. This protects the source of water for humans and also cleans any polluted water released from the villages. The habitat also creates a breeding ground for thousands and thousands of other species. They extend an area of wetland by up to five times. No other animal on the planet can do that; this is why we call them wetland angels."

A study by the global conservatin group WWF has shown that when you put water buffalo into wetlands, the biodiversity of the creatures found there increases exponentially. It has been estimated that freshwater wetlands hold more than 40 per cent of all the world's species and 12 per cent of all animal species.

Ho points to the canals formed by the buffalo's tramping and churning. A fish leaps from one furrow, flips in the air and plunges back between plump-leaved wetland plants.

"Without the buffalo's presence, wetland areas start to dry out and the special ecology with various amphibian species and beautiful birds goes into decline," she says. "Pui O is the most important water buffalo habitat in all of Hong Kong."

Less than 50 metres from where Ho stands, construction waste is piling up on that "most important habitat".

In 2001, prior to a project to upgrade electrical cables from Pui O to Cheung Chau, power company CLP Power conducted an environmental-impact study of the habitat "between the Pui O villages and the Pui O beach, including the Pui O Marsh and Taro Bed" - basically, where the water buffalo live. It concluded that the land was of "high ecological value" and found a total of 52 species living in the wetland, "which is high compared with other wetlands in Hong Kong".

"[The CLP Power study] is the only comprehensive environmental-impact study of the area that can be found on record," says Martin Lerigo, an executive committee member of the Living Islands Movement, a group dedicated to the sustainable environment of Hong Kong's outlying islands, with a focus on Lantau. "It documents in detail all of the wildlife and plant life here. It found species of plants, amphibians and birds that are rare to Hong Kong and semi-rare internationally. It provides substantive documentation that the wetlands are of high biodiversity and ecological value and that land adjacent to them would be the same if left undisturbed for 15 years.

"As the study was done in 2001, 14 years ago, it is likely that these adjacent areas are now, in fact, of high biodiversity and ecological value. Another study must be done to establish whether this is the case or not."

The Living Islands Movement has been working alongside others to prevent further dumping on Pui O's wetlands, a project that has required both tenacity and patience.

The Environmental Protection Department says the CLP study is out of date and that the department does not need to consider it when "acknowledging" and giving the go-ahead for the dumping of rubble on the wetlands. The Living Islands Movement has asked for a new study to be conducted. With bureaucratic alacrity, the department says that, in accordance with the Environmental Impact Assessment Ordinance, an assessment can only be carried out for "a defined project" and, as the dumping is piecemeal, it does not qualify.

People who want the wetlands, with their near-unique flora and fauna, to be conserved feel trapped in a catch-22 situation. The environmental protection and conservation departments will neither give consideration to the out-of-date assessment nor sanction a new one. It raises the question of how the departments responsible for environmental protection and conservation can fulfil their responsibilities when they refuse to assess whether a piece of land needs protecting.

The wetlands in Pui O lie within land designated as a coastal protection area in an outline zoning plan drawn up by the Town Planning Board for south Lantau. According to the board, "This zone is intended to conserve, protect and retain the natural coastlines and the sensitive coastal natural environment, including attractive geological features, physical landform or area of high landscape, scenic or ecological value, with a minimum of built development. It is also intended to safeguard the beaches and their immediate hinterland and to prevent haphazard ribbon development along the south Lantau coast. In general, only developments that are needed to support the conservation of the existing natural landscape or scenic quality of the area or are essential infrastructure projects with overriding public interest may be permitted."

The plan expressly forbids filling and dumping within the coastal protection area. However, the government's interpretation of the law means the South Lantau outline zoning plan is unenforceable because no enforcement controls, in the form of a document called a "development permission area", were added to the original plan.

When this anomaly, which affected a number of outline zoning plans across Hong Kong that lacked DPAs, was addressed in 1991, the rectification wasn't made retrospective. Also, for reasons best known to the board, when it amended the Town Planning Ordinance and the outline zone planning process in 1991, it was decreed that a new plan would not be allowed where one already existed.

In other words, south Lantau's outline zoning plan, which is unenforceable, cannot be replaced with a plan that is enforceable. In effect, the outline zoning plan might as well not exist.

Consequently, the director of the Environmental Protection Department, Anissa Wong Sean-yee, who has discretion within the Waste Disposal Ordinance to either "acknowledge" or decline applications to dump rubble, has been able to approve four applications so far. There are more than 20 further such applications in the pipeline. If they are all allowed, the Pui O wetlands will disappear forever.

The Living Islands Movement and others have spent six months corresponding with the department while the rubble has grown into large, unsightly heaps. The department and other relevant government departments have given one reason after another as to why they can't stop the dumping. Eventually, local objectors felt they had no other option but to take the matter to judicial review.

"For a judicial review, you can't simply say you don't like the government's decision," says Lerigo. "A judicial review deals with whether the decision breaches the constitution and whether it involves administrative flaws, namely illegality, irrationality or procedural impropriety. The applicant for the judicial review, a local resident, is challenging this decision on the grounds that it breaches the outline zoning plan and the intention of the law that the outline zoning plan should be enforced. In addition, the Waste Disposal Ordinance implies discretion on the part of the [environment] director and she should have applied her discretion to prevent dumping of rubble on an area of high ecological and biodiversity value, exactly the areas that Hong Kong has committed to protect under its obligations as signatories to the Convention on Biological Diversity.

"She should also have used her discretion on the issue of vehicular access, as the plots of land that have been dumped on were accessed by dump trucks crossing private and government land without permission. Plus, there is one plot that was fly-tipped on a year ago. The [environmental protection department] asked for the rubble that was fly-tipped to be removed by the landowner, who just left it there. The landowner later applied to fill the same plot and was given the go-ahead by the [department]. This is tantamount to the [department] condoning fly-tipping: a criminal act, which, ironically, is policed by the [department]."

In response to requests for comment for this article, a departmental press officer will say only, "In view of the pending [judicial review], we do not consider it appropriate to comment or provide an interview on this matter."

Those who condone the dumping say the landowners in question have gained the required permission from the department and that if people are so bothered about saving the buffalo, they should donate their gardens to the animals. It is understandable why landowners want to despoil agricultural land. If, at a later date, the land is rezoned for housing - a distinct possibility if the whole area becomes nothing more than a pile of rubble - then they can build. Village houses on Lantau sell for somewhere in the region of HK$15 million each.

"It's a difficult conundrum because most people find it understandable why indigenous villagers feel they have a right to develop their own land," says Lerigo. "It's worth noting, however, that the vast majority of the patchwork of privately owned lots which make up the wetlands do not belong to indigenous villagers but to property development companies, registered in interesting places like the British Virgin Islands and Liberia. "The majority of indigenous villages still have an affinity for the place in which they grew up; the wetlands and the buffalo are part of their heritage."

"Foreigners say we don't like the buffalo but they misunderstand us," says Ho Chun-fai, who is a representative of Sai Wan Village and has lived his whole life in Pui O. "Actually, many of us love the buffalo but we also have our own interests. We also want a balance between nature and people but the foreigners ignore our needs and concerns and they only think about the buffalo … and this creates a conflict."

That conflict is often stoked by misunderstanding, he says. "A woman was pushed off the path by fighting buffalo and injured. We are trying to widen the path to make it safer. As soon as we started, a complaint was raised about the dumping, so we were told to stop by the [environmental protection department]. But actually, it's not dumping of construction waste; it's a mixture of earth and a bit of rubble just to make the path a safe width.

"This is the kind of thing that really annoys villagers. The government is stopping us making it a safer place for us to live. We need the government to act as a middle man in this conflict and to explain our rights."

Ho Fong-tim is another indigenous villager who is fed up with the attitude of "complaining foreigners", and he, too, is looking to the authorities for a solution. "The government is not doing anything to help local people. The government needs to offer us some solutions. For example, it could offer to exchange the land. If that happened then the government could keep the fields and we could use the other land. The government actually knows about the problem but it isn't doing anything about it."

Lerigo agrees that the onus is on the authorities, "in particular those government departments responsible for the environment, conservation, land and planning, [which should] come up with a solution that recognises land rights of indigenous villagers … and the need to protect ever-dwindling areas of outstanding beauty, which we need to protect for the next generation of Hongkongers. There are options like land swaps, rezoning or extension of existing village zones, which, whilst difficult, can be achieved if the political will is there."

"The government has a Development Bureau and a Lantau Development Advisory Committee," says Ho Loy. "So, the government has the manpower and the resources to do it. We have educated the government about why we treasure this land and why we believe in sustainable development. We'd like our government to demonstrate that it cares about our environment and not just about money."

Says Ho Chun-fai: "We need to be able to find a solution that suits all parties - the local people, the government, the foreigners and the buffalo."

The focus is now on the Environmental Protection Department; will it live up to its name? If not, what will happen to Lantau's water buffalo?

"I would certainly hope that [the conservation department's] policy is one that would allow the continued presence of these buffalo elsewhere in Hong Kong, if that is the last resort," says Wong. "One option … is the wetlands near Mai Po. There are already a few buffalo there and they are of tremendous benefit to the biodiversity, with their stomping and eating. The [department's] wetland park [in northern Tin Shui Wai] could also take a few. There are some still in Kam Tin, of course, but development is rampant there, as well.

"Of course, it is best to leave them in Lantau."