New Agriculture Minister Femke Wiersma has at least one target in mind for the next six months: incorporating a minimum limit into the calculation of nitrogen deposits in nature reserves. The government uses the AERIUS Calculator, run by RIVM, to grant permits. The minimum limit is now 0.005 moles per hectare per year, an amount so small that it is impossible to measure.
Back support
The Minister of Agriculture recently received unexpected support from scientific authorities. The RIVM underwent an annual inspection. Scientific reviewby a panel full of professors and other academic researchers. This audit assesses the scientific quality of a part of the RIVM each year. This time, the audit concerned the RIVM’s Centre for Environmental Quality and was chaired by Arthur Petersen, a professor in London and former chief scientist at the Dutch Environmental Assessment Agency.
More independent
His committee decided that RIVM should act more independently of the government on the nitrogen file and should make it more clear that the uncertainties in AERIUS were too great to be used in the current license.
Arthur Petersen participated as an expert witness last spring. State Council lawsuit On the extension of the A15 motorway. The highest administrative court then decided to approve the spatial threshold value: from 25 kilometres onwards, nitrogen deposition can no longer be attributed with sufficient certainty to a single source.
In the same way, Femke Wiersma also wants a minimum in terms of precipitation amounts. The Interprovincial Consultation (IPO), of which she was a member until recently as a Frisian representative, will publish a report on the scientifically acceptable minimum for modelling nitrogen precipitation amounts. The same Arthur Petersen is also indirectly involved in this scientific advice.
RIVM responds
On behalf of RIVM, two researchers are now responding to the scientific scrutiny: Wouter Mara, who participated as a designer in AERIUS, and Joost Damen, head of the Centre for Environmental Quality.
B In the official response to the audit, you stated that RIVM had already expressed concerns about AERIUS’s role in the licensing process in September 2023. This would create a conflict with your independent scientific role. What’s the deal with that?
Last year, the central government’s AcICT audit committee found that: a report Where I suggested that AERIUS be removed from RIVM and put somewhere else. We supported that based on the idea that we are responsible for modelling, measuring and reporting to central government, but we are not primarily an ICT organisation that has to manage something like AERIUS that is used for licensing. That is a foreign activity for us.
This is one. The second reason is that our management of AERIUS is increasingly at odds with the fact that it is now a tool closely linked to the RIVM, but used for licensing; in which we have no role. This competes with our image as an independent institute that scientifically records, measures, monitors and reports on air quality, and nitrogen in particular.
It would be better to bring AERIUS closer to an organization more suitable for this purpose. That was the background to this. Our comment in SeptemberThis is also consistent with AcICT advice.
In fact, we must adhere more closely to our core mission.
B In the scientific review the committee says: As an institute, be clear and consistent about what is appropriate and why, such as AERIUS being a licensing issue. What is your response to that?
In fact, we should stick more closely to our core mission. That is, to represent how nitrogen is distributed correctly, at national and regional levels. So we should not be close to the licensing. Because that is where the choice is made by the competent authorities. And there should be no indication that this is our choice or our responsibility.
The report says: Communicate model uncertainties clearly, and be transparent about them. Well, we take that seriously. We do that too. This year we conducted research into how uncertainties occur in the national distribution model and how we can tighten them. We added additional measurement points. And later this year, we will publish a report on site-specific uncertainties.
TNO wrote in a report that AERIUS is the best available. In this sense there is no alternative.
B But what the committee meant was: You should have made it clearer to the government that AERIUS could not be used on such a small scale. The modelling uncertainty is too great for that. Do you agree?
What we agree on is that you always have to deal with uncertainty when working with models. And we have to make that known in a good way. And that’s the lesson I’m learning from him mainly. And we’re also trying to put that into practice now by communicating more actively about the uncertainties we have in our models.
B Can you as RIVM please state that AERIUS cannot be used for modelling on an area of one hectare within the granting of the permit?
We disagree with that. You can use AERIUS for that. However, there is some uncertainty associated with it. Policy-wise, you have to decide how acceptable you find that.
B Why have you never investigated what a scientifically defensible arithmetical minimum might be?
This has been investigated. But the conclusion is that no mathematical minimum can be set on the basis of objective scientific arguments. Much earlier, we cooperated with the Ministry of Agriculture, Nature and Food Quality. Already exploring options extensively.All sorts of things were added to this, including measurements. This is in line with what the provincial consultation now asked for. And ultimately, that led to the policy choice to use 25 kilometres as a maximum.
B I understand the criticism is that the uncertainty becomes so large when modeling such small quantities that you can’t be sure if it is still an actual nitrogen deposition.
No, but you can’t rule that out either. That’s why it can have an effect.
This comes with a greater degree of uncertainty. This makes sense and we have to imagine that.
B RIVM acquired AERIUS from the Ministry of Agriculture in 2015. Is it true that AERIUS was not originally intended for modelling on such a small scale?
This is a misunderstanding. The AERIUS calculator as a licensing tool is by definition intended to calculate small contributions. We also calculate the total deposits in the Netherlands. The same calculation models are behind this. And in those national calculations we cannot say: this comes from this or that farm. But if you are going to do a calculation for granting permits – if you widen a road or expand a farm – you have to enter everything in great detail. So you are doing a different kind of calculation. So I think that these two uses of calculation models lead to a misunderstanding that AERIUS is not suitable for detail.
B I ask this because the scientific audit report states that the accounting methods that have become relevant to policy were previously used on a national scale, and when they were used on a small scale, problems arose. Is this true?
It’s true that the models we use at the national level have been developed more to do these great models. And with that comes more uncertainty. That makes sense, and we need to be able to think about that. The discussion about good modeling comes from the uncertainty and the choices you make in the licensing context. But these are not technical problems that the model can’t handle; the scientific phenomena that the model calculates still apply.
The simplest summary is the law of conservation of mass. If you put something out, it ends up somewhere.
B How difficult is it to prove the arithmetic minimum scientifically?
The simplest summary is the law of conservation of mass. If you release something, it ends up somewhere. This nitrogen didn’t disappear at some point. That makes it difficult to say on the basis of scientific arguments: it’s gone. You can calculate a small contribution, with a large amount of uncertainty. But that uncertainty doesn’t mean it’s zero. Then the question might be: how do you deal with this uncertainty? That depends on the request from the licensing authority.
B The nitrogen that is actually emitted has to stay somewhere, but the important thing is whether you can prove that it will end up in a specific place, in this hectare of nature reserve that is at risk.
The further away we get from the source, the less certainty we can have about it. But it can’t be ruled out. It hasn’t disappeared.
What have we written before?
Also read these documents from the Ministry of Interior about the minimum calculation:
This piece explains what the inter-county consultation is trying to do.
In this interview, Professor Chris Backes explains why the nitrogen crisis in the Netherlands is a unique phenomenon.
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