Overuse of nitrogen fertilizer costs the European Union €70 billion – €320 billion per year, according to a landmark assessment of nitrogen flows across Europe, released today (11 April) at a workshop on nitrogen and global change in Edinburgh, UK.
For years, researchers have warned that the damage caused by compounds of nitrogen released into air, soil and water likely outweighs the benefits of greater crop production. In water, for example, the runoff encourages algal blooms that kill fish, while nitrates increase our risk of bowel cancer. In air, nitrogen oxides help create ground-level ozone and smog.
As Mark Sutton, a lead author of the assessment, explains in a comment piece for Nature this week (‘Too much of a good thing’; subscription required), it is hard to tally up all the costs and benefits of our production of ammonia and other ‘reactive’ nitrogen compounds (so named to distinguish them from the unreactive nitrogen gas, N2, which makes up 78% of Earth’s atmosphere). For today’s assessment, more than 200 scientists spent over five years assessing how reactive nitrogen affects water, soil, biodiversity and human health.
The economic answer – for Europe, at least – is that the costs massively outweigh the benefits. This is not true in every case: when it comes to the effects of various nitrogen compounds on warming or cooling climate over Europe, the scores on either side come out even. It is for human health and biodiversity that reactive nitrogen causes its worst effects.
To combat these problems, the researchers say, farmers should have to use efficient agricultural techniques that cut down on fertilizers – something that the Netherlands and Denmark have required for more than a decade, Sutton says. (Indeed, policies like the Gothenburg Protocol have helped to cut European nitrogen pollution since the 1980s).
In a suggestion that dominated some media headlines, the researchers also think Europeans should try to eat less meat, cutting down on crops required for livestock. “If Europeans obtained all their protein from plants, only 30% of the crops grown currently would be needed, reducing nitrogen fertilizer inputs and the associated pollution by 70%,” says Sutton.
The problem in other parts of the world may be much worse than in Europe. A recent assessment of nitrogen fertilizer use in China, for example, was particularly worrying. The scientists behind the European assessment want a worldwide assessment to follow, and hope for global agreements on nitrogen use that cross between existing UN conventions on biological diversity and air and water.