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Better than bottled: How a Dutch company uses bison to maintain pure drinking water

  • Water companies in the Netherlands have introduced bison and other large grazers to the dunelands from which they draw water to serve more than 4 million customers.
  • The grazers keep tree and shrub growth in check and allow the dune ecosystem, home to 50 percent of the country’s biodiversity, to reach optimal ecological health.
  • The reintroduction of the bison, which has been extinct in the Netherlands for thousands of years, also gives conservationists new insights into the management of the iconic species outside of forests.

A photographer and I have been walking for an hour through Zuid-Kennemerland National Park, which is sandwiched between the North Sea and the city of Haarlem in the Netherlands. You’re either crazy or a cyclist to be out in the windswept coastal dunelands during the winter months. But we’re here for a different activity in the most densely populated country in the European Union: bison watching.

Most of the Bison Trail is spent sloshing through sand that lies just below the surface all along the heavily developed western part of the Netherlands, also known as the Randstad megalopolis. Yellow-painted poles demarcate this sanctioned trail, which travels up and over the shoulders of shifting dunes as they struggle to hang on to their toupees of marram grass in the frigid wind.

Panting, bent double, I spot two official-looking chaps kitted out with waterproofs and binoculars the size of elephant tusks.

“Have you seen the bison?” I venture.

“They’re sheltering in the woods over there,” one of them replies through thick gray stubble, pointing over undulating dunes to the far side of the 330-hectare (740-acre) bison enclosure called the Kraansvlak. “But you’re missing out — look,” he continues, gesturing with his tusks toward a nearby stag that lifts up its trophy of antlers. It was lazily grazing just across the dune slack from us, almost annoyed we hadn’t noticed it.

The thing that intrigues me, though, is not that my narrow-minded focus has blotted out a resplendent stag. No, it is that these volunteers have the letters PWN emblazoned on their dark-blue waterproofs: PWN is the partly state-owned water company supplying 1.7 million North Hollanders with piped water. It is the first time, but not the last, that I will ask representatives from a water company about wild animals.

PWN, it turns out, employs bison, semi-feral horses and hardy cattle as “large grazers”: ungulates whose daily munch is vital to the conservation of nature and the production of clean water.

Dune slacks in the Kraansvlak bison enclosure, a 330-hectare portion of the 3,800-hectare (9,400-acre) Zuid-Kennemerland National Park. Image by Mandie van der Meer.


“Dunewater” quenched 15 to 20 percent of the Netherlands’ piped water demand in 2015. Only three of 10 Dutch water companies make this dunewater — PWN, Dunea and Waternet — but they fully supply The Hague, Haarlem, Amsterdam and most of the Randstad megalopolis with piped water. Between them, the three companies have 4.4 million customers.

Rebecca Wielink is an employee of Dunea, which supplies most the province of South Holland, and is dressed in khakis in the middle of the 2,000-hectare (4,940-acre) Meijendel dune reserve, just 5 kilometers (3 miles) from The Hague city center. She is the children’s education specialist tasked to receive regular school trips — perfect for my level of understanding.

“It began with a cholera problem,” says Wielink. In the mid-19th century, a population boom in The Hague led to issues of sanitation. Drinking water was traditionally collected from the canals, but when waterborne diseases began to spread, the city was forced to find a solution. Some brewed beer to ensure sterilization of the water, but others had a less-intoxicating idea.

“The city began tapping the groundwater in the dunes,” Wielink says. “But if you take too much fresh water out, brackish water starts to rise.”

By the 1940s, clean and accessible groundwater reserves had been plundered. Dunea had to find a new solution, and so began piping river water to the dried-out dune slacks, effectively using them as a massive natural filter. The process of infiltration takes two months, after which the artificial groundwater is collected, further filtered, and then fit for use.

Still employing this method, Dunea annually processes 75 million cubic meters (19.8 billion gallons) of water for 1.4 million customers in and around The Hague, home to the Dutch parliament and the royal family, among others.

“Do you use chlorine to sterilize the dunewater?” I ask Wielink. Thrown off guard by the question, she relays it to her colleague. “What’s chlorine?” her colleague replies, confused. Indeed, none of the dunewater companies uses chlorine to purify their drinking water, a fact I learned through an interactive child’s game at the Dunea visitors’ center in Meijendel.

Scientists have long known that rainforest ecosystems are vital to the water cycle, and hydrological services are often put forth as key reasons for protecting nature. But few companies in post-industrialized nations seem to embody this concept as fully as the Dutch dunewater companies: Dunea’s logo is a frog made of half dunes, half water.

A Konik horse in the Meijendel dunes. Image by Joshua James Parfitt.
Dune slacks in Meijendel filtering water for The Hague and Scheveningen, whose skylines are visible in the distance. The sign reads “Nature. No entry,” demarcating restricted areas where infiltration occurs. Image by Joshua James Parfitt.

Conservation and clean water

“We are a water company, and we are stewards of nature,” Wielink says, confirming the interdependence of the robust dunes to Dunea’s sand-filtered water.

The two other dunewater companies apply a similar filtration method as Dunea, and between the three of them they manage 14,000 hectares (34,600 acres) of dunelands along the western coast of the Netherlands. This number is almost equivalent to the 15,000 hectares (37,100 acres) of dunelands in the hands of the State Forestry Service; but walking between their often adjoining parcels of land, and providing you don’t trespass into the restricted infiltration areas, you would be stumped to tell the difference.

PWN, furthermore, has done something unprecedented. In 2002, it stopped collecting water from the Kennemer dunes, a subsection of the Zuid-Kennemerland National Park in its care, but did not deliver the land over to the State Forestry Service.

“In large areas water abstraction has been stopped altogether, for instance in the Kennemer dunes,” Sjakel van Wesemael, PWN’s manager of nature and recreation, wrote in a 2014 report. “This has led to a widespread restoration of wet dune slacks. Water management hereby preserves a subterranean fresh water body that, besides its own ecological value, functions as a drinking water reservoir in case of a disaster.”

The Kraansvlak bison enclosure is situated within the Kennemer dunes. Five years after curtailing water abstraction, in 2007, PWN released three European bison (Bison bonasus) into the enclosure. They were the first European bison seen in the Netherlands after suffering local extinction thousands of years ago.

As of 2018, the herd has grown to 22 individuals.

PWN’s hope was that bison would engineer the duneland to optimal ecological health by grazing them. In a practical marriage of conservation and water security, the bison are literally helping to safeguard North Holland from drought.

European bison help cultivate the natural groundwater in the Kraansvlak. Image by Ruud Maaskant.

Large grazers

Unfortunately, I missed out on bison watching. My first encounter with large grazers eventually came in the Meijendel dunes when 11 Konik horses, a purposefully introduced semi-feral breed, bullied my bicycle over while I was on top of a dune photographing the landscape.

According to Yvonne Kemp, an ecologist with the ARK Nature Development organization, who supervises the bison for PWN, the story of large grazers begins with the viral hemorrhagic syndrome (VHS) pandemic that decimated rabbit populations in the 1990sThis, coupled with an increase in nitrogen deposition due to acid rain, caused the dunes to become undergrazed and overgrown.

“The Kraansvlak, for a really, really long time, had never been a forest,” Kemp says. “But I know from the aerial pictures from before [I came] that it was covered with grass all over the place, and with shrubs and trees.”

Perhaps it was a good thing that nature was reclaiming a landscape. Not according to Kemp, though, who says the changing ecology meant that native species dependent on dunelands were dying out. PWN’s coastal dunes account for less than 0.5 percent of the land in the Netherlands, but are home to 50 percent of the country’s biodiversity.

In the 1990s, PWN noted a decline in native species of birds, such as red-backed shrikes, and a 2012 joint-research project from Radboud University in Nijmegen put the blame on the disappearance of large insects. The project in particular pointed to vital grasses, such as marram, upon whose roots specialist insect larvae exclusively fed. These grasses only occurred in duneland that showed blowout activity, i.e. displayed patches of loose sand, but this type of micro-ecosystem had largely disappeared.

Stands of marram grass in the Kraansvlak. Specialist native insects depend on blowouts such as this, and are one of the cornerstones of a biodiverse duneland. Image by Mandie van der Meer.

“Bison open up the area,” Kemp says. “They eat … shrubs and debark trees. In just a few years you can really see the changes — they do their job very well. They wallow a lot, and with this behavior all year long you can see local patches of sand and so pioneer vegetation has a chance again.”

Since the 1990s, the water companies and the State Forestry Service have been installing large grazers all along the Dutch dunes to maintain their ecological integrity. Domestic breeds of Highland or Galloway cattle are the grazer de rigueur, often coupled with Konik horses, but bison come with the advantage of being roaming tree surgeons, able to remove thick shrubs and trees.

Due to improved efficiency, PWN uses only 5 percent of its land for water infiltration. North Hollanders pay for the conservation of the remaining 95 percent through their utility bills, and make over 6 million visits a year to the restored land.

“It’s about enjoying … wildlife. Not to be against it, but to see it as an opportunity,” Kemp says. “We’ve [lost] a lot of nature around us because, of course, the human population is growing and [we’ve been] building a lot … But now we really see that we can live together with [nature], but we have to do it sustainably, in a wise way — like in a 21st-century way. We cannot go back.”

Herds of bison and Konik horses in the Kraansvlak. PWN hopes these large grazers, which also include wild fallow deer, will keep the duneland “open.” Image by Ruud Maaskant.

A micro-managed wilderness

The reintroduction of European bison is a dream come true for ecologists, conservationists and nature enthusiasts. In the early 20th century, retreating Nazi soldiers and rogue hunters finished off the last remaining bison populations in eastern Poland and the Caucasus; but the viable reintroduction of bison to the densely populated Netherlands is a triumphant story of humans and wildlife working together.

The bison project at Kraansvlak has also benefited ecology in general.

Before the herd arrived in the Netherlands, little was known about how they would fare in a semi-open grassland. Whereas bison in forested areas, such as at Białowieża in Poland, require feeding during winter months, the Kraansvlak bison have survived without any supplementation to their diet.

Kemp says they haven’t fed the bison in over 10 years. “Since we have GPS collars on the animals, we also see that they prefer much more half-open landscape. We show that you don’t necessarily need a forest to have bison. Our project is mentioned as an example of a non-traditional way of managing the animals,” she says.

The pioneering success of PWN’s unconventional approach to water security has since inspired two other Dutch nature reserves, the Maashorst and the Veluwe, to bring in bison. The national population stands at 42 individuals.

Wild about wilderness in general, Kemp expresses excitement at the story of a lone wolf that roamed the Netherlands for two weeks in January this year. The first confirmed sighting of a wolf in the Netherlands, albeit on the German border, occurred in 2015, the first live sighting since 1869.

Despite the enthusiasm at nature’s slow recovery, it is unlikely that water customers would be happy to pay for wolves howling on the outskirts of their cities. But for the time being, there are Dutch children marveling at a 2meter-tall (6-foot) stuffed bison at the PWN visitors’ center just a kilometer (0.6 miles) from Haarlem. And this animal is not extinct.

Visitors come in the millions every year to the nature reserves owned by the dunewater companies. And since the lands are protected in the name of water security, they’re unlikely to be developed any time soon. I’ve seen the Dutch turn their noses up at bottled mineral water, not just because of the price. Together with ecologists and endangered herbivores, they enjoy this micro-managed wilderness, a pragmatic fountain of life, smack in the middle of a bustling megalopolis.

A young girl stands before a PWN sign, which points to the wisentgebied, or bison enclosure. The enclosure is just a kilometer from the center of Haarlem, in the Netherlands. Image by Mandie van der Meer.
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