Nitrogen, the most important fertiliser for producing food, also poses one of the most severe risks to human health.
 

Chemical compounds containing reactive nitrogen are major drivers of air and water pollution worldwide. As well as its part in chemical reactions that release greenhouse gasses into the atmosphere with almost 300 times the global warming potential of carbon dioxide, pollution associated with nitrogen use has also been linked to diseases like asthma and cancer in humans.

According to researchers at the Potsdam Institute for climate Impact Research, unless immediate action is taken, nitrogen pollution could rise by 20 percent by 2050 (in a middle-of-the-road scenario). The researchers also found that ambitious mitigation efforts made now could decrease pollution by 50 percent.

Potsdam researcher Benjamin Bodirsky said, "Nitrogen is an irreplaceable nutrient and a true life-saver as it helps agriculture to feed a growing world population – but it is unfortunately also a dangerous pollutant"

In the different forms it can take through chemical reactions, it massively contributes to 'respirable dust', leads to the formation of aggressive ground-level ozone, and destabilises water ecosystems. Put in financial terms, damage from the effects of nitrogen use has been estimated in the billions of Euros – or between 1-4 percent of total economic output. Furthermore, around half of this damage is the result of agricultural use.

In order to look at the impact of nitrogen, Potsdam researchers ran extensive computer simulations to explore the effects different mitigation measures would have on reducing nitrogen pollution and on farming.

Both farmers and consumers would have to participate in mitigation

"It became clear that without mitigation the global situation may markedly deteriorate as the global food demand grows," according to Bodirsky. "A package of mitigation actions can reverse this trend, yet the risk remains that nitrogen pollution still exceeds safe environmental thresholds."

One of the major criticisms of the current food system is that negative impacts of dominant farming methods (including environmental degradation and public health issues) are not factored into costs, and are instead paid for by wider society. Sustainable farming, and particularly agroecology, advocates argue that if the costs of these damaging aspects were factored into farming, a greening of agriculture would be the only economically viable option.  

However, Bodirsky said that combined changes both in the way food is produced and consumed could substantially reduce the risks from pollution.

Under current conditions, every second ton of nitrogen put onto fields is not taken up by the crops but blown away by the wind, washed out by rain or decomposed by microorganisms. To reduce losses and prevent pollution, Potsdam researchers recommend farmers target fertiliser application to plants' needs, using soil measurements and aim to efficiently recycle animal manure for use as fertiliser.

"Mitigation costs are currently many times lower than damage costs," said co-author Alexander Popp.

"For consumers in developed countries, halving food waste, meat consumption and related feed use would not only benefit their health and their wallet," Popp added. "Both changes would also increase the overall resource efficiency of food production and reduce pollution."

Nitrogen picture not clear cut: "Health effects of nitrogen pollution more important than climate effects"

"The nitrogen cycle is interwoven with the climate system in various ways," said anoter research, Hermann Lotze-Campen. Nitrous oxide is amongst the most damaging of greenhouse gases. However, nitrogen containing aerosols scatter light and can thereby cool the climate. As fertilizing nutrient, nitrogen also enhances the growth of forests which binds CO2, Lotze-Campen said.

The professor added, "Currently the health effects of nitrogen pollution are clearly more important, because the different climate effects largely cancel out. But this may change – hence limiting nitrogen would have the double benefit of helping our health today and avoiding climate risks in the future."