The difficult comeback of the seagrass, a plant that once played a leading role along the Dutch coast

It protects the coast, promotes biodiversity and takes CO₂ On, but is not often in the spotlight: seagrass. A century ago the water plant was rampant in the Wadden Sea and even turned a complete industry on it, but now it has almost completely disappeared. And with the plant all the positive effects. “It is an essential ecosystem; it is not just a few plants,” said seagrass researcher Laura Govers. Biologists therefore work with might on the return of Zeegras in the Wadden Sea and the Zeeland Delta. But that still has a lot of feet in the earth. The history and future of Dutch seagrass in six parts.

1A kind of land grass – but different

“Zeegras is a bit like landgras,” says Laura Govers, deputy professor Marine Ecology and Nature Management at the University of Groningen and scientist at the Royal Netherlands Institute of Research of the Sea. She has been studying the plant since 2009 and is closely involved in recovery projects in the Wadden Sea and Zeeland Delta – it monitors the plant while diving or wading itself. Seagrass is not a grass species but a flowering plant, with flowers, seeds and pollen. “Unlike algae (or algae), it roots in the soil and also absorbs nutrients with the roots.”

Zeegras evolved back into the ocean between 70 and 100 million years ago as a land plant. Back, because land plants came from algae about 450 million years ago. Zeegras is the only group of higher plants or vascular plants – plants that have a vascular system to transport water – that occurs in the sea.

There are two types of seagrass in the Netherlands: large seagrass, Zostera Marinaand small seagrass, Zostera Noltii. Large seagrass can be a meter long and has two so -called morphotypes. Large seagrass lives permanently under water, plans through the rhizomes and can live to be 50 years old. One -year -old seagrass grows on drying soil, rises again every spring and is therefore more vulnerable. Small seagrass is about twenty centimeters long, is a long age and lives in dry areas.

2At least as important as coral

The green blades don’t look very impressive, but appearances are deceiving. “Seagrass fields are just as important as coral reefs,” says Govers. “It is an essential ecosystem; it is not just a few plants.” Zeegras protects the coast by dampening waves and current. And the root mats retain sediment, which also prevents Kusterosia. Seagrass fields are also an important delivery room for fish and other marine animals. It also ensures clearer water, because it slows down the flow, causing sediment to settle.

All seagrass had disappeared in one fell swoop in 1932. Elsewhere it recovered, but not in the Netherlands

Moreover, Zeegras is very efficient in storing co₂ In the soil: 30 percent of all stored carbon in the ocean is in seagrass bottoms. “You can compare it with forests on land, in terms of oxygen production and habitat,” said Govers. Surprisingly much effect, for a relatively small plant. But Zeegras is rapidly disappearing worldwide: two football fields per hour, says Fee Smulders, seagrassecologist at Wageningen Marine Research. She investigates seagrass in the Dutch Caribbean, where 2,000 hectares are still growing. Together with coral reefs and tropical rain forests, seagrass fields are the most endangered ecosystems. Man is the greatest threat; In particular through water pollution and the actively removing along the coast. Smulders: “For example, with Resorts, people don’t want it there.”

3From flowering industry to almost extinct

A century ago the seagrass flourished exuberantly along the Dutch coast. Until 1930 there grew more than 15,000 hectares, multi-year seagrass in the Wadden and Zuiderzee. Hundreds of families lived from the ‘Wiervisserij’, especially on Texel and the then island of Wieringen. Govers: “It was a very professional fleet. They also knew that it was not whose, but that’s what they called it.” Seagrass was used in mattresses, pillows, as wall insulation and in dikes.

In one fell swoop that all disappeared in 1932. Govers: “It is hard to find out what exactly the cause was.” On the one hand, a seagrass disease (the fungus Labyrinthula Zosterae) The entire northern hemisphere, on the other hand it was also the year in which the Afsluitdijk closed the Zuiderzee and strongly clouded the water.

Where in other European countries the seagrass recovered from the disease, that never happened in the Wadden Sea. This is probably because with the disappearance of the seagrass the Wadden Sea became more clumsy, says Govers. Zeegras itself provides the required clear water for the photosynthesis for flourishing. Once the seagrass is gone and the water cloudy, it is difficult to return on its own. Certainly if there is no nearby population from which it can recover.

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In the Wadden Sea, hundreds of hectares grew, large and small seagrass in addition to the in hiding type. That seemed to survive the clearing in the first instance. Zeeuwse Delta also flourished: in the Oosterschelde, Grevelingenmeer and the Veerse Meer. But all those populations have been declining since the 1970s, in particular due to water pollution, algae growth and closures of the sea arms through the Delta Works. The few thousand hectares there died almost completely over the years.

After the turn of the century, there was all about 200 hectares of seagrass throughout the Netherlands – a mere 1 percent of what was there a hundred years earlier.

4The world’s largest recovered drying seagrass field

Since 2022, Rijkswaterstaat has been working with various universities and companies on large -scale seagrass repair and recovery research in the Wadden Sea and the southwestern Delta. It builds on the work of Natuurmonumenten, which has been working on seagrass recovery in the Wadden Sea since 2014. Sea grass is sown every year or planted and monitored with cuttings. The project is part of the European Water Framework Directive and Natura 2000 and must improve the ecological water quality. The current goal is to restore the hiding seagrass in the Wadden Sea to 10,000 hectares. In the Zeeland Delta, Rijkswaterstaat is now aiming for five hectares in the Grevelingenmeer and Vijf in the Veerse Meer. The feasibility of these numbers is still being investigated. And in the Oosterschelde, The SeaGrass Consortium works on seagrass repair, together with the University of Groningen.

Since the nineties – and a single study in 1950 – biologists have been investigating the recovery possibilities of Groot Zeegras. After years of research, trying out, sperm loss due to a seagrass infection and fine -grinding the sowing technique (with a kit syringe from the hardware store instead of a floating bag), the seagrass repairers still unexpectedly achieved a success in 2018.

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Sowing is done with a kit syringe from the hardware store

With the uninhabited Wadden Island Griend, the largest recovered drying seagrass field in the world was created. “We actually discovered the location by accident, because we walked around for another project,” Govers laughs. Models did not show the album as a suitable place for seagrass recovery, but the researchers saw small seagrass grow and decided to make an attempt with large seagrass. Large -scale recovery was not yet the goal. But the seeds caught on and the seagrass field expanded to almost 1,700 hectares in 2024. Positive effects of the seagrass are also measurable, says Govers. Biodiversity is 30 percent higher in the seagrass field than on surrounding bare mudflats: just like in naturally occurring seagrass fields.

It is still too early to say that the seagrass has returned to Griend permanently, says Govers. “It has already survived a heat wave and ice, so we have good hope. But we want to keep a finger on the pulse.”

The success of Griend now wants to copy Rijkswaterstaat to a new location, near Ameland. Small seagrass is also added to the research at the locations. Experiments with large and small seagrass also run in the Zeeland Delta. Since 2022, the tests in the Grevelingen have been successful, says Marloes van der Kamp, Marien Ecologist at Witteveen+Bos consultancy, main contractor of seagrass repair project Wadden Sea & Zeeland Delta. “It survived the winter and we got a grip on a successful recovery method.”

5From 1 million to 100,000 donor seam grass seeds

According to Govers, the Netherlands is at the forefront worldwide with seagrass recovery, “because we have lost a lot of seagrass so early.” Van der Kamp also sees that other countries ‘full of admiration’ look at the large -scale, nationally organized recovery project. Van der Kamp: “The scale and cooperation with science, business and government help us enormously to make meters. In other countries, projects are often much smaller and private funds must be written or lacks the applied look of business. What we do in the Netherlands is really unique.”

Yet the recovery is not yet completely from a slate roof. Govers: “We want to move forward very quickly, but the knowledge is not yet entirely. Processes at ecosystem level go much slower than we would actually like if people.” In addition to the knowledge delay, a new problem arose last year: a shortage of seagrass seed. The seeds for the successful field at Griend came in large numbers from Germany. But “seagrass is booming”, Says Govers, and the demand for seeds is increasing. In previous years there were always a million seeds available for the Dutch recovery project, since last year only one hundred thousand.” That is because the Germans have tightened the protection of seagrass, “Van der Kamp explains. “They now only make seed available for research, not for recovery.”

Rijkswaterstaat explores the possibility of growing seeds itself, says Van der Kamp. There is also carefully harvested in the fields at Griend. Until then, the available seed is an important limiting factor of the recovery of large seagrass in the Wadden Sea.

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6Gardening does not belong in the Wadden Sea ‘

Govers notices that her enthusiasm for the seagrass repair work is not shared by everyone. “Some people think that the Wadden Sea is the last piece of wilderness and believe that” gardening does not belong there “. They say it is a dynamic natural system that you have to leave alone.” But the Wadden Sea is not that untouched at all, she continues: just think of fishing, gas extraction, dredging, salt extraction and recreation. And then the Wadden Sea itself is also not able to recover, because of the dams and dikes that change the flow and a “lack of effective area protection”.

Govers wonders aloud whether recovery to a Wadden Sea full of seagrass, such as a century ago, is still possible: “The Wadden Sea has changed too much by humans.” In the Grevelingenmeer and the Veerse Meer, the seagrass seems to be better than expected, so perhaps more recovery is possible. “The great thing about this recovery project is that we learn what is realistic while doing,” says Van der Kamp. In addition to recovery, the protection of the last existing fields is just as important, Govers emphasizes. “Because that is much more effective. Existing fields already have all the important ecosystem functions.”

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Photo Laura Govers



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