Dutch health institute: Agriculture Min.'s nitrogen claims are not scientifically proven
The Netherlands’ National Institute for Public Health and the Environment (RIVM) has rejected Agriculture Minister Wiersma’s claim that her proposal to relax nitrogen regulations is scientifically supported. Other scientists consulted by her ministry have also disputed her assertion.
The controversy centers on Wiersma’s plan to raise the "mathematical threshold" for nitrogen emissions, which would make it easier for businesses to expand and for housing and infrastructure projects to proceed. The proposal is a key demand of a majority in the Tweede Kamer. It also aims to provide relief for PAS-melders—farmers and entrepreneurs who became non-compliant following the Council of State’s 2019 nitrogen ruling.
The minister has kept the final version of the scientific report informing her policy secret, and experts involved in advising the ministry have not been given access to the document.
Wiersma announced her plan in De Telegraaf on Friday, stating that she wants to increase the nitrogen threshold by a factor of 200—from 0.005 to 1 mol per hectare per year. She told the newspaper that "science" had confirmed that such an increase is possible.
"The answer is yes," Wiersma said. "We arrived at 1 mol and want to implement it. We also had this checked by a second group of scientists."
The minister’s claim is reportedly based on research by Professor Arthur Petersen (University College London), who developed the proposal at her request. The second group of experts was asked by the agriculture ministry to review Petersen’s findings.
However, multiple scientists who participated in the review process told NOS that they do not agree on setting the threshold at 1 mol. RIVM, which has advised the government on nitrogen policy for years, reiterated that "there is no conclusive scientific justification for a mathematical threshold," a position it had previously presented to the Tweede Kamer in October.
Other scientists consulted by NOS confirmed that there is no strong scientific basis for Wiersma’s proposal.
Several experts reportedly also declined to participate in the ministry’s consultations. Jan Willem Erisman, a nitrogen specialist at Leiden University, said that "you cannot ask scientists to set such a threshold."
"Where you place the threshold for permits is not purely a scientific question," Erisman said. "Other factors, such as economic interests and environmental concerns, also play a role. It is up to policymakers to weigh those interests."
The lack of transparency surrounding the scientific report has further fueled criticism. Even researchers who contributed to the analysis have not seen the final version. Wiersma’s ministry has refused to release the document, arguing that businesses might use it to apply for permits or challenge the government in court.
"The fact that it is being presented as scientifically peer-reviewed means it should follow scientific norms for publication," said Emiel van Loon, a researcher at the University of Amsterdam. "Transparency and open discussion are essential."
Despite the scientific uncertainty, the minister maintains that her plan is not a political decision but one based on research. However, RIVM stated that while Wiersma has the authority to set a higher nitrogen threshold, she does not need scientific validation to do so.
If implemented, the relaxed rules would likely lead to higher nitrogen emissions, which could negatively impact overburdened Natura 2000 conservation areas. "This increases the challenge of reducing nitrogen deposition in vulnerable ecosystems," RIVM warned.
Wiersma acknowledged in a letter to the Tweede Kamer on Monday night that her plan carries legal risks. If the higher threshold is overturned in court, businesses that rely on the change could face legal uncertainty. "This could create a new group of PAS-like cases," she wrote.
