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UvA researchers on nitrogen report: “Our study is anything but at odds with current policy”

Sija van den Beukel,
15 september 2023 - 09:58

On Tuesday, the report on the “actual” nitrogen spread from dairy farms was released. What are the implications of that long-awaited study? Folia asked UvA scientists Emiel van Loon and Albert Tietema, who led the study. “Our study is by no means a catastrophe for nitrogen policy; it is at most a ripple in the water.”

For three years, the statistician Emiel van Loon and the ecologist Albert Tietema investigated the distribution of nitrogen at two comparable dairy farms in the Netherlands: one at the edge of the A6 motorway near Almere, the other in North-West Friesland. A labor-intensive job in which they used no fewer than five measurement methods, some existing and some new and still experimental.

“Emissions rather than distance should guide buyouts”

In a nutshell, the report concludes that 91% of the nitrogen emissions from a barn do not end up in the farmyard but in higher air layers. That nitrogen settles somewhere, but whether that is within a short distance or thousands of miles from the barn is impossible to say. The remaining nitrogen, about 9%, falls within 500 meters of the barn. There is a nitrogen peak within 100 meters of the barn.


Those conclusions largely match what the National Institute for Public Health and the Environment (RIVM) stated years ago. The RIVM has long been researching nitrogen emissions in the Netherlands through a mathematical model that came under fire in 2020. Could it be said that the nitrogen that settled in the nature reserve came from surrounding farms? UvA scientists Van Loon and Tietema had to answer that question on behalf of the Mesdag Dairy Fund. 


What do these results mean now?

Tietema: “The most important conclusion is that it is not worthwhile for a specific nature reserve to buy up a farm farther than 200 or 300 meters from that area. After all, you can't trace that nitrogen back to that specific farm. Nitrogen is still emitted into the environment, but it comes from the nitrogen blanket: the collection of nitrogen from agriculture, traffic, and industry from the Netherlands and abroad together in the upper atmosphere. These can no longer be traced back to a single source.”


The government now maintains a list of highest emitting sites within 25 kilometers of Natura2000 areas. Should that list be scrapped?

Tietema: “The list itself shouldn’t be, but the radius of 25 kilometers should be changed. It needs to be adjusted to 200 or 300 meters. In addition, you have to buy out the farms and businesses with the highest nitrogen emissions. Emissions rather than distance should guide buyouts.”


Van Loon: “At the same time, there is a case for working within a radius of 25 kilometers. We can observe that beginning 500 meters from the barn, the nitrogen values become so low that they can no longer be distinguished from the background noise. But that does not mean that emissions are zero. The area of a 25-kilometer radius is so large that nitrogen concentrations become very low, but not zero. And if you use the calculation model of the RIVM, then of course you can take the principled position: There are emissions – however low – and they always have an effect.”

Foto: IBED
Emiel van Loon

Tempers have run high in the nitrogen debate. Was that also the reason for the radio silence to the media during the investigation?

Van Loon: “That does make it incredibly difficult. On the one hand, you want to share your measurements publicly as transparently and directly as possible. On the other hand, you know that it generates a lot of hullabaloo. Then you find yourself torn over what to do.”


Tietema: "If you mention even one number in an internal meeting, you spend so much time refuting that number if it changes due to advancing insight. We tried to avoid this as much as possible by maintaining a kind of radio silence within the sounding board group, including the Mesdag Dairy Fund, until the final report was available. Before that, you do get approached by farmers and people from the province on whether you have any results yet.”


News media give their own interpretations of the results. For example, Trouw headlined: “The RIVM model is pretty accurate” and De Telegraaf said: “New study blows peak load policy out of the water.” How do you react to that?

Van Loon: “It can’t be said that the report blows anything out of the water. In fact, I think the opposite is true. The study is a ripple at best. On the contrary, it supports the RIVM model and is anything but at odds with current policy. At most, the distance from the nature reserve becomes less important in policy than before.”


As a researcher, how do you deal with the different interpretations in the media?

Van Loon: “I look at it cluelessly and shrug. That may be the wrong attitude. I have made one attempt at media communication by asking a colleague to send a response to a very interesting tweet. Other than that, I just don't have time for that. I am not qualified to bother with that.”


Tietema: “I don't think you can convince a large portion of people on Twitter, either. Everyone gets out of it what they want to get out of it.”

Foto: Jan van Arkel
Albert Tietema

So has this report finally dispelled the doubts about mathematical models of the RIVM?         

Van Loon: “As a researcher, you have surprisingly little influence on that. The results are also very deliberately distorted. It seems fashionable to oppose models; it is mistaken for being critical. People call for ‘real’ measurements without realizing what they are bringing down on themselves. Asking for more research is also an attempt to drag things out further. By now the situation is clear: Too much nitrogen is being emitted and agriculture is a big part of it.”


What is wrong with more measurements?

“Yet more measurements would not only cost more money but would also produce even more random and strange measurements. Nitrogen is very difficult to measure; there is a lot of noise in those measurements. People expect you to have results after three months of measurements. But if you look at the graph, you see how massive the variation is in them due to weather conditions, the use of plants, and the famous bird pooping in one of the measuring tubes. If you start averaging that over months you do see a trend. So measurement is not as simple as it seems.”


Tietema: “Incidentally, this whole discussion made the RIVM realize that they were monitoring on too limited a scale. They were working with three measuring points in nature reserves in the Netherlands, which will now be 10. So it has been expanded considerably. This research has contributed to that.”


What impact will the report have on the upcoming elections?

Van Loon: “I think with all the commotion it will have no effect. People have long since decided on their views. A survey of this magnitude can not make a difference.”


Given the grand expectations for the report, that is a sad conclusion.

Van Loon: “I don't think so. My personal goal has never been to influence policy. That may be different for the Mesdag Dairy Fund. We did the research because we are interested in how nitrogen distribution works. We contributed to scientific insights. On policy, I don't need to have that much influence.”

Tietema: “Indeed, we as a university keep far away from policy implications.”

Van Loon: “Again, I think this study is being made out to be much bigger than it is. It's still three years of research on two dairy farms involving a lot of manual labor. You base a policy implication on years of research; that is a small contribution. An unimaginable amount of research has already been done on nitrogen. The only thing we hadn’t seen in the last decades was empirical research in the Netherlands on this detailed scale. If you look at China, as many as 10 studies on nitrogen diffusion have been published in the past two weeks alone. That is sometimes neglected.”