The nitrogen crisis has a legal cause. In 2019, the Council of State canceled the policy for the protected Natura 2000 areas, of which the Netherlands has 162. The policy, the Council of State found, offered too little protection. Since then, the country has been ‘locked’.

According to European rules, Natura 2000 areas must be brought and kept in ‘a good state of conservation’. Their condition should not worsen. The aim is to preserve and restore biodiversity, which has been declining in Europe since the middle of the last century. EU countries must report every six years. The Netherlands distinguishes 52 habitat types – such as blue grasslands, oak-hornbeam forests, muddy riverbanks and dune heaths with heather. According to the latest report, from 2019, more than half are in a “very unfavorable state”. Only 6 get the verdict ‘favourable’. Since 2006, many habitat types have deteriorated. “At least thirteen are now in danger,” says ecologist Anne Schmidt of Wageningen University, who has been involved in the reports since 2006. This includes the estuaries, the moist heaths and the old oak forests.

Traditionally, urbanization, intensification of agriculture and environmental pollution mainly caused a decline in nature, according to the latest report. The current ‘pressure factors’ are ‘nitrogen deposition and groundwater abstraction’. The precipitation of nitrogen compounds is still too high in many Natura 2000 areas. In recent decades, the Netherlands Environmental Assessment Agency has also repeatedly mapped out that the condition of many Natura 2000 areas is deteriorating.

But first a step back. What is Nitrogen?

Emissions of ammonia and nitrogen oxides were limited until the middle of the last century. But after 1950 it increased sharply, due to the rise of intensive livestock farming and the use of fossil fuels. Emissions were at their highest in the late 1980s. Since then, due to government policy, it has fallen again. But the emissions are still so high that they are harmful to much nature.

Where do nitrogen emissions come from?

All kinds of figures are collected to determine the emissions of ammonia and nitrogen oxides. The 3,000 largest companies in the Netherlands must report the emissions of all kinds of substances every year. It is also known how many cars and trucks are registered in the Netherlands, and what their fuel consumption is. Farmers have to report their head of livestock, the stables and their type, applied manure, fertilizer use and much more. At various places in the Netherlands, the concentration of ammonia and nitrogen oxides in the air is measured as a check. If in practice it turns out that cars drive less economically than expected, or that sheds emit more than tested in the lab, for example, the figures are corrected.

How do the compounds spread in the air?

Once in the air, ammonia and nitrogen oxides disperse. In the Netherlands there is often a westerly wind. A considerable part of the ammonia and nitrogen oxides produced in the Netherlands is blown abroad. The Netherlands ‘exports’ four times as much of the nitrogen compounds compared to what is blown into the Netherlands from abroad.

The concentration of nitrogen oxides and ammonia in the air is being measured in more and more places in the Netherlands. For nitrogen oxides, this happens at 73 locations, every hour. Ammonia is measured every other month at more than 300 locations, within more than 80 Natura 2000 areas. And in six other places, the concentration of ammonia is determined every hour.

Ammonia and nitrogen oxides precipitate from the air to the ground. That is called deposition. In this way, the connections also end up in the protected Natura 2000 areas. RIVM has developed a computer model (OPS) with which it calculates how much ammonia and nitrogen oxides precipitate in the Natura 2000 area. For this purpose, it uses, among other things, the figures on emissions and data on the distribution and behavior of these compounds. A committee of experts assessed the RIVM model two years ago and concluded that it is good enough to base policy on. But the advice was to further expand the monitoring network. That is going on now.

How does nitrogen precipitate?

At a distance of 20 km, roughly 30 percent of the ammonia emitted is deposited, and 10 percent of the nitrogen oxides. At a distance of 250 km, that is 80 and 40 percent respectively.
RIVM has developed a computer model (OPS) to calculate the deposition. This includes data on emissions and the behavior of ammonia and nitrogen oxides in the air. Just like data about weather and wind. As a check, the deposition is being measured in more and more places in the Netherlands.

What effect does it have?

Not only do plants disappear with eutrophication, animals that depend on these plants also have a hard time. An example is the fritillary butterfly that deposits its eggs on the dune pansy. In many places, that plant loses out to faster-growing grasses. Biodiversity is impoverished due to eutrophication.

Acidification also affects the entire food chain. The combination of effects also means that plant leaves contain a lot of nitrogen, but little calcium and potassium. Insects have a harder time surviving, so there is less food for insectivorous birds. Birds of prey such as sparrowhawk, goshawk and kestrel have also been shown to suffer from acidification.

Nitrogen deposition in the Netherlands fell from 2,700 mol per hectare (converted to 38.5 kilos) in 1990 to 1,730 mol/ha in 2018. But that is an average. Regional differences are large. In places such as the Gelderse Vallei and De Peel, a deposition of approximately 4,000 mol/ha has been measured.

Uptake of nitrogen in nature areas often exceeds the standard

In recent decades, much research has been done into the effects of ammonia and nitrogen oxides on nature. The damage differs per habitat type (of which 52 are distinguished within the Natura 2000 sites). One type is more sensitive than the other. Based on all that research, a so-called critical deposition value (KDV) has been determined for each habitat type. If the deposition exceeds that value, there is a risk of significant damage. In many Natura 2000 areas, the CDW is exceeded, sometimes many times over. The cabinet wants this precipitation to be below the KDW in most Natura 2000 areas by 2030. For the Natura 2000 areas where the CDW is still exceeded, since the ruling of the Council of State, no new economic activity may be licensed that causes additional nitrogen deposition in that area. To obtain a nature permit, it must be demonstrated – substantiated by research – that the activity within a radius of 25 kilometers does not bring any additional ammonia or nitrogen oxides into a Natura 2000 area with excessive deposition.

An excess of precipitating nitrogen compounds also harms nature outside the Natura 2000 areas, but it is not legally protected.

Another problem is nitrate in leaching water. Fertilizer contains ammonium (NH4+) that can be absorbed by plants. But plants do not absorb all the ammonium present (because too much is administered). Bacteria in the soil can convert ammonium into nitrate, which leaches into the groundwater or ends up directly in the surface water. An excess of nitrate can make groundwater unusable as a source of drinking water and algae growth is stimulated in the surface water, which means that bathing waters sometimes have to be closed. The biodiversity in those waters usually declines (limited light, plants die, fish disappear).

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