this is what nitrogen does to nature

‘So this is what you don’t want,’ says Harrie van der Hagen in the middle of the Meijendel nature and water extraction area, between The Hague and Katwijk. The nature strategy policy officer at drinking water company Dunea points to tall grass on a dune slope. dune reed. A summer bloomer with soft plumes. What is wrong with that? The grass species dominates the vegetation and thus suppresses other, rarer plants, the result of too high concentrations of nitrogen in the area.

It seemed like such a carefree sunny morning at the Dragonfly Valley, as this part of Meijendel is called. The last nightingales are singing in the undergrowth, in the distance a cuckoo is also doing its best. The dunes look like a green oasis. Appearances are once again deceiving. Although much has improved in Meijendel since the dramatic 1990s, on this dune slope we are faced with the consequences of excessive nitrogen emissions. Grassing. The white top of the dunes from the old song of the same name is no longer so white, but green.

‘All this here is dune reed,’ says Van der Hagen, pointing to clumps of grass. And that is too much: ‘It may be here and there, but now 40 to 50 percent of the grassland here is dune reed. Actually, that’s still okay. It was even worse in the 1990s.’

According to Van der Hagen, here in Meijendel, with the sea a few hundred meters away, there should be short-grassed, flowery grasslands. ‘There should be about 50 to 60 types of plants growing here. Now I don’t count more than 20’, says the nature manager who has been dealing with the ‘nitrogen file’ every day for 35 years – don’t let angry farmers claim that the problem is new.

While elsewhere those angry farmers are driving their own nitrogen woes on tractors throughout the country, Van der Hagen points to a plant with small red flowers. sheep sorrel. Nice is not it? No, it actually does not belong in this dune landscape. ‘It is an indicator that the soil is too acidic and no longer calcareous enough.’ The direct result of nitrogen.

What should have been here then? The cross-leaf gentian, says Van der Hagen. The shore-seed rape! ‘It should have turned yellow from the blooming yellow bedstraw. Little Stone Thyme! Those are the cream of the crop. Now the latter is a very rare species here.’

the culprits

The names of the dune plants probably mean nothing to the layman. He only sees green, and on his day at the beach, he might just think that there is nothing wrong here. A misunderstanding, therefore, explains Van der Hagen.

Meijendel is a so-called Natura 2000 area, designated to remain protected up to European level. Nitrogen precipitation here once – in the 1990s – was worse, reaching around 40 kilos per hectare annually, which is a lot. According to Van der Hagen, that number has been halved through measures and management, but 20 kilos per hectare per year is still double the maximum desired 10 kilos per hectare per year.

And so the government must and wants to try to significantly reduce nitrogen precipitation here too, by tackling ammonia emissions from manure and nitrogen oxides from traffic and industry. Agriculture is not the main culprit here on the coast. Where nationally this is responsible for about 60 percent of nitrogen emissions, here on the outskirts of South Holland it is around 20 percent. Farmers in the area and in the surrounding estate zone could switch to other forms of agriculture.

Industry and traffic have a larger share in this part of the Randstad conurbation. And shipping: behind the dunes of Wassenaar and The Hague, international cargo ships have been permanently anchored in the busy North Sea for years, near the port of Rotterdam speculating on the prices of oil and other products – it is a kind of futures market at sea. Van der Hagen: ‘Those boats are constantly steaming here. The engines are never turned off, they have to run just to provide power on board.’ The southwest wind does not miss its effect: the nitrogen descends on the land, together with what is blown in from England.

dust pit

The dune reed that Van der Hagen pointed out mainly grows on the north side of dune slopes. He takes the reporter a few tens of meters away. There, on the sunny south side, the world looks different. More succulents on dry sand. The ecologist points to an inconspicuous dark moss-like carpet: the large dune star. It looks dead, but when he pours a few splashes of water on it from a bottle, the plant magically comes to life within seconds: a fresh cheerful green colors the spot. In addition, the sandhorn flower has already spread its seeds, the mother plant has turned into straw.

It can only grow on sandy soil where there is still sufficient lime. That is the case here: Van der Hagen points to the crushed remains of sea shells and snail shells, which feed the vegetation here – until too much nitrogen removes the lime from the bottom.

What Van der Hagen is all about here: that hole with sand next door. “A dust pit,” he says. The core of a dynamic dune landscape, which is constantly in motion due to the wind and which permanently rejuvenates the ecosystem. In the sand are fresh tracks of the sand lizard and beetles. ‘This is what you do want, as a dune manager: enough drift pits,’ says the ecologist. But yes: the more nitrogen, the more vegetation, the fewer dust pits.

That is how complex nature management is: a precarious balance between wish and reality. Van der Hagen: ‘What you actually hope is that all those systems of bare sand, mosses and grasslands will walk through the landscape in a mosaic shape. Then as a manager you have to do the least, it is also the cheapest’.

But yeah. Nitrogen throws a spanner in the works.

Off to Texel

Less than 140 kilometers north, on Texel, which is equally summery, the situation is different. Certainly, nitrogen also takes its toll there, but the Wadden Islands belong to a zone where the announced measures will be considerably less pronounced than elsewhere. Forester Thomas van der Es, who this year exchanged his work area in the Biesbosch for Texel, sees the differences between Meijendel and his own National Park Dunes of Texel.

In particular, on the northern tip of the island, above the Cocksdorp, there are still barren, lime-poor dunes. The wheatear, a rare bird that likes to breed in rabbit holes, is still there: Van der Es counted 41 territories. ‘That is the highest number in the Netherlands’, he says with some pride. A lot of hard work has gone into this, including grazing sheep to keep the area open. Nevertheless, bunt grass and sand sedge are advancing.

Further on, at post 15, the landscape looks more like that of Meijendel, says Van der Es. ‘More thickets and other woody undergrowth with shrubs.’ This is how an entire forest was created on Texel, which must be prevented for the rest of the island.

On Texel, the dune nature has more leeway than in The Hague, where the dune is essentially a fairly narrow strip of land. The island is also not surrounded by industry or heavy traffic, at most from shipping and tourism. That offers nature on Texel more opportunities, says the forester. Although there is more to it on Texel, the quality of nature there also requires a lot of maintenance, Van der Es acknowledges. There is also something to be desired: ‘The best thing would be if you could let nature run its course in your own way, so that populations would be less vulnerable. Take the large nacre and the critically endangered dune fritillary: they run backwards, here too, due to grassing. I hope to see a few more this year, otherwise I fear they are really extinct.’