UvA scientist on nitrogen research: ‘I will not easily lend myself to policy advice again’
The announcement by agriculture minister Femke Wiersma to raise the nitrogen limit based on ‘scientific evidence’ caused further commotion in the infamous nitrogen issue. Because how scientific was that substantiation really? For UvA statistician Emiel van Loon it was the last time he lent himself to policy advice.
Let’s go back to the beginning. Why does Minister Femke Wiersma want to increase the lower limit from 0.005 mole to 1 mole of nitrogen per hectare per year?
“The Netherlands has been ‘stuck’ for years because successive cabinets have been unsuccessful in their attempts to implement nitrogen-reducing measures. The amount of nitrogen emissions and deposition in the Netherlands has not decreased since 2010. The court ruled that this was not what we agreed on, which has resulted in all kinds of unreasonable measures. Such as new construction projects with relatively low nitrogen emissions that can no longer go ahead because they do not have a permit.”
“Raising the lower limit is a shortcut that politicians have found to get economic development going again. If the lower limit is raised, the Programma Aanpak Stikstof (PAS, Programme for the Approach to Nitrogen ed.) notifiers will also get a permit again. These are the entrepreneurs with limited nitrogen emissions whose permits were revoked in 2019 because the Council of State ruled that the PAS did not comply with the European Habitats Directive.”
“In order to raise the lower limit, a scientific basis was needed that would allow politicians to go to court. Ernst Meijer of TNO and I were then asked to determine, in discussion with a group of about fifteen scientists, whether we could establish a lower limit for the model (the Aerius Calculator, ed.) used for nitrogen licensing based on scientific considerations.”
“Models always have limitations that determine for which purposes and in which situations they can be used. Aerius is intended for calculating total deposition on a large scale, for example, the whole of the Netherlands, with a resolution of roughly 1 square kilometre. Its current use for licensing purposes, where you calculate deposition from individual sources to individual hexagons of 1 hectare, is therefore really outside that scope of application. The criticism of this specific application of Aerius is not new. The Hordijk Committee previously concluded that it leads to false security, and there is consensus on that point in the scientific community. Using the lower limit makes the use of the model somewhat more reasonable, but does not solve the false sense of security at its core.”
Together with Ernst Meijer of TNO, you calculated whether a scientifically substantiated lower limit for Aerius exists on behalf of the Interprovincial Consultative Body (IPO). That report was published this summer. What was the main conclusion?
“That there is a lower limit below which you can no longer attribute the nitrogen emissions from a source to the deposition in a nature reserve, but that we have not been able to find scientific evidence for a specific lower limit based on our data. Based on the detection limits of the measuring equipment alone, you are dealing with a range of 10 to 100 mol of deposition per hectare per year that you can measure.”
So how do we arrive at the lower limit of 1 mol that agriculture minister Wiersma wants to introduce?
“One person from that expert group, Professor Arthur Petersen, had already written an expert opinion in which he argued that a lower limit of 1 mol should be chosen. In addition, one of the recommendations in our report was to take a broader look at the scope of application of Aerius Calculator.”
“Based on this, the Ministry of Agriculture, Fisheries, Food Security and Nature (LVVN) asked Arthur Petersen to elaborate on his expert opinion. He did so, and in doing so, stuck his neck out. Petersen’s expert opinion was sent to a group of experts for review and revision. Agriculture Minister Wiersma sent the result to the House of Representatives.”
And why 1 mole?
“It didn’t come out of the blue, it was also used in the (PAS) programme. But it could also have been 2 moles or 10 moles.”
And is it a good idea to raise the lower limit to 1 mole?
“I don’t disagree with 1 mole, I think it is a sufficiently low value and much more reasonable than 0.005 moles. But if you look purely at the detection limit, the model is not accurate to within 10 moles either. And it doesn’t solve the false sense of security of Aerius Calculator either.”
“In addition, a team from the IPO has also carried out a risk analysis of the consequences of a higher lower limit. How many livestock farms are there that could buy more nitrogen rights for extra livestock if the lower limit were raised? The conclusion was that it would probably work out. After all, you also have to deal with phosphate and animal rights, so you can’t just take on an extra hundred cows.”
“PAS notifiers would become legal with the raising of the lower limit, but those emissions have already taken place, so that is not the problem. There will be a few cases where a higher lower limit will result in permit holders and a small increase in nitrogen, but not many.”
“If you add up all the little bits and pieces, you do have an increase in nitrogen deposition. I also work on biodiversity and I find the decline in biodiversity terrible. And therefore it is not consistent with advocating a higher lower limit for the use of Aerius.”
“But the assignment was to look at the uncertainty in the model. And I don’t find the argument valid that you don’t want to consider uncertainty because it could lead to an unwelcome measure. You can, however, say, first ensure nitrogen reduction before we start a discussion about a lower limit. And it is possible that the court will follow that line and say: we can discuss a higher lower limit if there is a decrease in nitrogen in the Netherlands.”
Does this scientific substantiation hold up legally?
“Opinions differ on that. A number of lawyers and civil servants at the Ministry of Economic Affairs had their doubts as to whether the Supreme Court would accept it.”
After the nitrogen study you conducted with Albert Tietema, you said in an interview with Folia that further nitrogen research would only serve to delay nitrogen measures further. How long are you willing to continue conducting research?
Van Loon sighs deeply.
“I will not be lending myself to policy advice on nitrogen regulations any time soon. I have now seen where that leads: it is used to postpone nitrogen reduction measures.”
“There are also so many other things that are worth investigating. We still hardly know where and how nature recovers best from nitrogen. If only to demonstrate: if you stop nitrogen emissions now, it will take a hundred years for a nature reserve to recover on its own. People often think that nature will be back in ten years. But that is absolutely not the case – in most cases, restoration measures are absolutely necessary. The motto is therefore to quickly reduce nitrogen emissions and other forms of pollution – that is by far the best and cheapest measure to save what can still be saved.”
