It is not only European protected natural areas that suffer from air pollution. The recreational Diemerbos near Amsterdam is also covered with a blanket of invisible nitrogen. It is not entirely clear where the nitrogen comes from.
The emission of ammonia from farms will have contributed, but also the traffic in the capital, the highways around it, the industry in the port area. Because the Diemerbos is a ‘green lung’ in the middle of urban industry, there are not many agricultural companies in the area.
The effects are far-reaching, says ecologist Arnout-Jan Rossenaar of Staatsbosbeheer during a walk. Nitrogen may be invisible, but the consequences are not. Man-sized stinging nettles line the footpaths, as do three meters high and elongated thorny brambles. “There are also nettles in a normal forest, but they do not reach two meters. It has to do with nutrition. Popeye got strong from eating so much spinach. These nettles have been given spinach: nitrogen.”
Strolling through the forest that was created in the 1990s is no longer an option, unless you have to wear clothes that cover the entire body. Without these measures, you will only get across a piece of forest with countless pricks, cuts and scrapes.
The Diemerbos is not a Natura 2000 area, but belongs to the so-called Netherlands Nature Network, which is intended to connect Dutch nature reserves. However, the deciduous forest with black alder, willow, elm, ash, oak, beech and birch is gradually becoming a nightmare for ecologists. Of the fifty species of plants and shrubs that could grow in a forest like this, only five to ten have survived the last fifteen years, says Rossenaar. These are species that can handle the surplus of the nutrient nitrogen, continue to grow and capture the light for other, more vulnerable forest species: blueberry, yellow avens, large beetle orchid, day cuckoo flower. “Those are species that are missing here now.”
Rossenaar points out two other species that thrive in excess: cleavers, which stick to your clothes, and bindweed, a plant that wraps itself around other plants. “The list of species is short. Biodiversity is limited.” Rossenaar points to a plant that has also been able to nest between nettles and brambles: the balsam of the giants, an exotic species. “He also likes nitrogen.”
And another thing: the forest can no longer rejuvenate naturally due to usury plants. “It has become complicated for a small sapling to become a large tree. Just go and grow, with all those nettles and blackberries around you.”
Also read this article: Ministry of Finance: nitrogen crisis can be solved for half cheaper
Only burgers
In the discussion about the government’s nitrogen measures, you regularly hear the argument that we should not worry so much about the damage to nature, since nature is much stronger than people think, and we can simply get used to the fact that some species are now win once at the expense of other species. Wrong, says Rossenaar. “You may find that you have to be satisfied with a limited number of species. But that’s like saying it’s okay to eat nothing but hamburgers every day. It means a huge impoverishment.”
Also read this article: How is nature doing? Questions and answers about the Dutch nitrogen problem
There is also something else: the poorer the flora, the fewer insects can live there. Rossenaar: “What I found very scary is that there are already some places in the world where there are no longer any insects. In China there is a place where the pollination of the pears is no longer carried out by insects, but by people with a tassel. If we continue like this, the plants will no longer bear fruit. The tomato is gone. The cucumber. The eggplant. Then we shot ourselves in the foot. Then vegetables become unaffordable.”
In short, anyone who reasons as if there really is no nitrogen problem and who says that it is only a paper problem invented by ‘Brussels’ is arguing, according to the ecologist, as someone who denies gravity. “If there is a red alarm light somewhere, you can close your eyes, but that doesn’t change the color of that light.”
Sod in moors
Rossenaar steps into a butterfly corridor, a grassy, meandering light path designed to attract butterflies. “It sometimes buzzes with butterflies.” This afternoon the turnout was a bit disappointing, although Rossenaar fortunately still managed to spot a chopped aurelia.
It is tempting to propose measures that could end the suffocation of the forest. Rossenaar does have a few suggestions, such as a global switch to circular agriculture. But what can you, as a manager of nature, do to limit the effects of excess nitrogen?
“Not much in forests,” says Rossenaar. But in other places it does. For example, Staatsbosbeheer and other nature organizations start sod cutting in heathland about every ten years, in order to make the soil less ‘rich’ and thus give vulnerable plants that do well on poor soils a chance. “If you see how much nitrogen is falling now, you would actually want to cut sod every three years,” says Rossenaar. But that doesn’t work. “Three years is too short for the heath to develop again. Then you won’t have any heather left.” In short: “We are at the limit of what you can still do against nitrogen.”
Also read this article: The forest area in the Netherlands is decreasing again, but there is also good news
A version of this article also appeared in the newspaper of 13 July 2022
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