The Marker Wadden: The Netherlands Built Five Artificial Islands in a Dead Lake to Rewild It

How a 90-million-euro archipelago of no-development nature islands is making the Markermeer ecologically viable again and unlocking the Amsterdam waterfront's long-term value.

Landlord Ledger Publications • Strategy • 2026-06-14

The Markermeer was an accidental lake. When dredging company Boskalis finished pumping silt into an archipelago of five new islands in the middle of it, they had created something that also defied category: land built not to house anyone, not to generate income, but to reverse the ecological damage caused by building other land.

The Unintended Lake

The Markermeer, a 700-square-kilometer freshwater lake in the central Netherlands, was never meant to exist in its current form. It is a byproduct of ambition interrupted. The Zuiderzee Works, the massive 20th-century engineering project that enclosed the Zuiderzee inlet from the North Sea with the Afsluitdijk in 1932, created the IJsselmeer lake to the north. Then, in 1976, a second dyke, the Houtribdijk, sliced the IJsselmeer in half, isolating its southern portion as the Markermeer. The original plan called for draining the new lake entirely, turning the 700 square kilometers into a polder called the Markerwaard. Dikes were built. Pumping was anticipated. Then the project was cancelled in 1986, following decades of environmental opposition and mounting cost concerns.

What remained was a lake without a purpose and without a functioning ecology. The Houtribdijk severed the natural sediment transport that had kept the old Zuiderzee alive. With no river inflow of consequence, no natural shores, and no tidal movement, sediment that had once been carried away by currents settled to the bottom. A 30-centimeter layer of silt accumulated across the lake floor. During windy conditions, the silt was resuspended, turning the water permanently murky and blocking light from reaching aquatic plants. An irony compounded the problem: by the 1980s, improved sewage treatment in Amsterdam had reduced the nutrient load flowing into the lake, which had previously supported algae, which had previously fed fish, which had previously fed birds. Cleaner water, paradoxically, made the lake less alive. Fish populations crashed. The birds followed. Natura 2000 designation notwithstanding, the Markermeer became what one ecologist called "a tub of water."

Engineering the Opposite of a Polder

The idea that would become Marker Wadden emerged around 2010, when Roel Posthoorn, a project director at Natuurmonumenten, the Netherlands' largest private nature conservation organization, began thinking about what it would take to break the Markermeer's downward spiral. The problem was the silt. The solution, Posthoorn concluded, was also the silt.

The concept was to dredge the fine sediment from the lake bottom and use it to construct artificial islands, creating in the process both new habitat and a mechanism to trap suspended particles. The islands would act as sediment sinks, creating sheltered, shallow-water zones where murky water could clear, where aquatic plants could root, and where fish and birds could return. The building material was the problem itself.

Posthoorn brought the proposal to Rijkswaterstaat, the Dutch national water management authority, and to the Province of Flevoland. The initial funding came from an unexpected source: 15 million euros from the National Postcode Lottery's Dream Fund, which supports what it describes as "brave and groundbreaking" charitable initiatives. That seed grant unlocked co-funding from Rijkswaterstaat and other government partners, bringing the total committed budget to approximately 50 million euros at project launch, eventually rising to 90 million euros across all phases as additional partners joined. Boskalis, the maritime dredging company that would build the islands, saw in the project an opportunity to demonstrate a technique that had never been attempted at scale: construction with fine-grained silt rather than sand.

"Building an island with sand is not that difficult, we do it all over the world," said Jeroen van der Klooster, project head at Boskalis. "What is unique here is that we use silt."

In March 2016, construction began. Boskalis used ring dykes of sand to contain basins into which silt was pumped from the lake floor, allowing it to consolidate over time into stable landmass. The process was slow and required constant monitoring. Silt behaves differently from sand: it compresses under its own weight, it is vulnerable to wave erosion, and its long-term stability under storm conditions remained an open engineering question. The first island was inaugurated on September 24, 2016, with Dutch King Willem-Alexander attending the ceremony. By 2021, five islands totaling 1,300 hectares had been constructed in the northeastern portion of the Markermeer, four kilometers south of the Houtribdijk.

What Came Back

The ecological response was faster than most researchers had anticipated. The sheltered shallow water between and around the islands began to clear. Aquatic vegetation established itself. The food chain that had been broken for decades started reassembling.

Birds were the most visible evidence. By the time the second island opened to visitors in September 2018, roughly 3,000 people arrived by ferry on its first public weekend to find around 1,200 avocets, along with spoonbills, terns, and waders. Within two years of construction, 127 distinct plant species had established themselves on the main island, most arriving by windborne seed. The red-crested pochard, a diving duck that had virtually disappeared from the Netherlands, returned to breed at Marker Wadden. The research program KIMA, coordinated by the Deltares institute and running in parallel with construction from 2017 to 2022, documented new fish spawning habitat forming in the shallow zones. A second phase, KIMA 2.0, launched after 2022 to focus on making the islands climate-adaptive and robust over the long term.

The archipelago operates as a nature reserve with no permanent residents and no commercial development of any kind. Visitors arrive by ferry from the harbor at Lelystad, approximately an hour from Amsterdam, and can walk a 12-kilometer network of paths and footbridges across the main island. One of the hides along the path allows visitors to observe life below the waterline. The other four islands remain entirely closed to humans and exist solely for wildlife.

This is the structural inversion that makes Marker Wadden significant as a property story. The Dutch have spent a century building islands in order to put people and agriculture on them. The polder economy, one of the foundations of Dutch prosperity, rests on the premise that land reclaimed from water has economic value as human-controlled space. Marker Wadden inverts this logic entirely: islands built at significant public cost, with no intention of generating direct revenue, whose value is defined precisely by the absence of human occupation.

The Property Argument Behind the Ecology

The ecological rationale for Marker Wadden is straightforward. The strategic rationale is more interesting.

The Markermeer sits at the center of the most economically pressured region in the Netherlands. The lake's shores are bounded by Amsterdam to the southwest and the planned expansion city of Almere to the east. During the timeframe of the Marker Wadden construction, approximately 60,000 new homes were planned for Almere as part of a long-running national strategy to relieve Amsterdam's housing pressure. That development depends on the Markermeer functioning as a Natura 2000 site. European nature legislation imposes constraints on development in areas adjacent to protected habitat: if the lake's ecological status continued to decline, those restrictions would tighten, not loosen. The EcoShape research consortium stated the position explicitly: "Improvement of the Lake Marker ecosystem is required to allow further socio-economic development in the region."

In other words, the Dutch government's ability to build 60,000 homes on the Amsterdam-Almere corridor was partially conditioned on the Markermeer not continuing to die. Marker Wadden was not separate from the regional development strategy. It was a precondition for it.

The broader waterfront dynamic is less explicit but operates on the same logic. Amsterdam's real estate market is among the most constrained in northern Europe, and lakefront and waterfront positions consistently command premiums. A functioning, biodiverse Markermeer, accessible by boat and occupied by returning bird species, is a meaningfully different amenity than a turbid, biologically depleted holding pond. The restoration does not directly monetize, but it creates conditions under which the surrounding built environment becomes more valuable. The lake is infrastructure.

The Deltares research institute, analyzing the financial arrangements behind Marker Wadden, described the project as rooted in a "win-win philosophy": using the sediments that caused ecological deterioration to build new nature and recreational assets, thereby contributing to the lake's restoration while also satisfying European regulatory requirements that would otherwise constrain development. The construction sector, including Boskalis and the broader Dutch hydraulic engineering industry, had an additional reason to support the project: Marker Wadden functioned as a demonstration of a technique with significant commercial potential.

A Dead-Lake Model for Export

The Posthoorn assessment that "every coastal area is heavily developed" has proven accurate as a market observation. Artificial lake degradation caused by dike construction or water impoundment is not a Dutch problem. It is a global condition. The Marker Wadden model, building with locally sourced fine sediment to create habitat islands that serve as sediment traps, addresses a problem that recurs wherever engineers have enclosed water bodies and severed their natural dynamics.

The knowledge program KIMA generated research explicitly designed to be universal, applicable in other regions with similar excess fine-sediment problems. The project has been described by those in the Dutch hydraulic engineering sector as having grown into "a new Dutch export product," positioning the country's dredging and water management expertise as applicable to ecological restoration rather than only land reclamation. Boskalis, Deltares, Royal HaskoningDHV, Arcadis, and Witteveen+Bos have all been involved in some capacity, and the project has generated scientific papers, international conference presentations, and a 2024 scientific conference at the Netherlands Centre for Coastal Research that drew 50 researchers to examine its water ecology outcomes.

The critique of this model is real and documented. Ben Abbott, an ecologist at Utah State University, called Marker Wadden "valuable and interesting" while noting that most ecological mitigation projects have been largely experimental and many unsuccessful. Lorie Staver, a plant ecologist at the University of Maryland, pointed to the Poplar Island project in the Chesapeake Bay, which has required $1.4 billion in funding over 45 years for maintenance and restoration work. Marker Wadden's maintenance responsibilities after 2030 remain unfunded. Wil Lases, a hydraulic engineer not connected to the project, argued that the islands disturbed the natural bacterial activity that was generating a different form of biodiversity in the undisturbed lake.

Whether the islands prove self-sustaining or require perpetual intervention is a question the KIMA 2.0 research program is now designed to answer. The water quality improvement that the islands were meant to deliver has not yet been definitively demonstrated by Deltares researchers, though they note its absence from the data does not mean the goal is unmet.

The Inversion at the Center of the Project

The conceptual challenge Marker Wadden poses to real estate logic is not simply that it is uninhabited. Parks and nature reserves are uninhabited. What is different here is the mechanism and the material: the islands were built using the tools and expertise of land reclamation, at costs associated with development, for the explicit purpose of preventing development. The dredging company that applied the same basic hydraulic technique across projects worldwide used it at Marker Wadden to produce the opposite outcome.

Eric Higgs, a rewilding specialist at the University of Victoria, captured the project's categorical strangeness precisely: "Marker Wadden is fascinating because it presently doesn't fit easy categories." He described it as "a copy of something that has no true original, because there was never ever a freshwater archipelago in that area." The ecosystem being restored never existed in the form being created. The baseline is imaginary. The engineered landscape is presented as nature.

That paradox is also what makes Marker Wadden legible as a real estate move. The islands are not trying to be what was there before. They are trying to create something that generates ambient value for the surrounding region, increases the Markermeer's compliance with European ecological standards, and makes the Amsterdam waterfront more desirable while producing no leaseable square meters. The value created is entirely external to the asset.

Whether the long-term maintenance funding materializes, and whether the water quality data eventually confirms the original sediment-trapping hypothesis, will determine how many dead lakes get their own archipelago. The Dutch have already built one and are selling the knowledge. The question is whether the world has enough tolerance for islands that exist to stay empty.