Half world's nitrogen pollution from 4 countries
A study examining nitrogen emissions from 188 countries has uncovered that four countries are responsible for nearly half of the world's total.
China, Brazil, India and the US are responsible for 47 percent of global nitrogen emissions, the study reports.
The research, published in international journal Nature Geoscience, is the first to track the global nitrogen footprint.
It suggests around a quarter of global nitrogen emissions come from the production of goods and commodities that are then exported and consumed outside their country of origin.
Countries which are importing more than they export of these commodities, resulting in less nitrogen pollution, are almost exclusively in the developed world.
Developing nations, due to the production of goods and therefore the pollution in the creation, tend to be nitrogen net-exporters – exporting more than they import.
New Zealand and Australia, because of their large agriculture industries, are some of the few wealthy nations that are net exporters of nitrogen.
"High-income nations are responsible for more than 10 times the emissions of the poorest nations," co-author and PhD candidate Arunima Malik says. "This reflects greater consumption of animal products, highly processed foods and energy-intensive goods and services."
As nations both consume naturally-occurring nitrogen and produce greater quantities of synthetic nitrogen, nitrogen pollution is becoming an increasingly significant problem, study co-author Professor Manfred Lenzen from the University of Sydney says.
"Polices are needed to integrate nitrogen supply-chains globally in order to reduce pollution," Professor Lenzen says. "We know nitrogen emissions are increasing – just as carbon emissions are increasing as populations expand.
He says they're now analysing trends, such as increased affluence and consumption, and looking at the various industries responsible for nitrogen pollution.
Nitrogen produced from combustion and agriculture, called "reactive" nitrogen, poses a serious environmental risk.
Unlike "inert" nitrogen, which makes up around 78 percent of air and is unable to react, reactive nitrogen gases can contribute to acid rain, climate change and air pollution, while nitrate from fertilisers can shift the balance of ecosystems and create dead zones in lakes and coastal regions.
The findings from the study include: