Scientists have called into question agriculture minister Femke Wiersma’s plans to break the deadlock over nitrogen compound emissions by raising the pollution limit by a factor of 200.

Wiersma’s plan to increase the so-called critical load or KDW – the amount that construction projects have to keep below when calculating their impact on the environment – was hailed as a breakthrough last Friday.

If implemented it would give the government far more room to issue nature permits for projects such as roads and housing estates, many of which have been shelved since the Council of State ruled more than five years ago that the Netherlands had to enforce European nature conservation rules much more strictly.

It would also ease pressure on livestock farmers to reduce the size of their herds or give up altogether in order to bring down nitrogen compound levels. European rules agreed in 1992 to protect birds and habitats impose strict limits on how much nitrogen can fall in designated conservation areas known as Natura-200 zones.

Green light

The minister from the farmers’ party BBB said she had commissioned a study by University College London professor Arthur Petersen that showed the limit could be safely raised from 0.005 mol per hectare to 1 mol, the limit used in Germany.

“We have agreed on 1 mol and that’s what I want to introduce,” she said. “The research has been peer reviewed and given the green light.

“It’s good news not just for farmers, but also for housing projects, because most of them are below 1 mol so this could be the solution for them.”

But scientists who reviewed the study said the decision on where to draw the line was a political choice, not a question of hard science.

“No scientific basis”

Jan Willem Erisman, of Leiden University, said: “Other factors have to be taken into account when making such a decision, such as the interests of the economy or nature. It is up to policymakers to weigh up these interest against each other.”

The government’s public health agency RIVM did not contradict Peterson’s findings, but said there was “no conclusive scientific foundation for a numerical limit”. Scientists also said they were unable to assess how their criticisms had been received because the minister has not published the final version.

In a parliamentary debate on Thursday, opposition parties in parliament accused Wiersma of offering “false hope” to farmers, because tough measures to reduce nitrogen compound emissions would still be needed.

The deposition limit is a figure used to calculate potential emissions from planned construction projects, but several court rulings have required the government to reduce actual pollution levels or face further sanctions. Total emissions need to fall by between 30% and 40% in order to meet European standards.

Last month Greenpeace won a case in which judges ordered the state to cut nitrogen levels in at least 50% of the 162 Natura-2000 zones by 2030 or face a €10 million fine.

Dead duck

Marieke Koekoek, of pro-European liberal party Volt, said: “Scientists often don’t agree 100%, but there is consensus among all experts that as well as an arithmetical limit, the other half of the equation is nitrogen reduction. One half has been jubilantly made public, but not the other half.”

Harm Holman, agriculture spokesman for coalition party NSC, said: “We were surprised with a kind of hallelujah story, but it turned out to be a half-dead duck.”

Even the PVV, which has stood side by side with the BBB on the nitrogen issue, said Wiersma’s comments had failed to explain how the cabinet planned to resolve it.

Agriculture spokeswoman Jeanet Nijhof said: “We have no idea where we’re going. The route the minister is going down is untenable.”