Four countries cause almost half the world’s nitrogen emissions according a study of global nitrogen footprints.
The research, an international collaboration led by the University of Sydney in Australia, traced the flow of emissions from 188 countries, in what it claims is the first ever such study.
The study, which also involved researchers from Yokohama National University and Kyushu University in Japan, concluded that the United States, China, India and Brazil are responsible for 46 percent of the world's nitrogen emissions.
Reactive nitrogen emissions can damage health and the environment, and the modelling noted a trend for increased nitrogen production and that found developing countries suffered local pollution caused by foreign demand.
The nitrogen footprint of a country is the amount of nitrogen emitted during the manufacture, transportation and consumption of products used in that country, including those imported.
The majority of emissions came from industries such as agriculture, transport and energy generation. Developing countries account for large amounts of nitrogen emissions from their exports of food, textiles and clothing, according to the study.
Arunima Malik, who co-authored the paper, said that significant net importers of nitrogen were almost exclusively developed economies: “High-income nations are responsible for more than 10 times the emissions of the poorest nations. This reflects greater consumption of animal products, highly processed foods and energy-intensive goods and services.”
A paper on the research has been published by the international journal Nature Geoscience.
Findings include that per-capita nitrogen emission ranged from more than 100kg annually for wealthy nations like Hong Kong and Luxembourg, to less than 7kg for developing nations such as Papua New Guinea, Côte d’Ivoire, and Liberia.
The research also found that said that Japan and other developed nations import reactive nitrogen embodied in Chinese-made clothing as well as US and Australian meat.
The UK, Germany, Italy and France exchange significant amounts of nitrogen emissions embodied in food products, according to the findings.
Hong Kong’s nitrogen imports are primary agricultural and raw food products because it lacks land to produce its own livestock and crops.
Developing countries such as China, India, Pakistan, and Thailand embody large amounts of nitrogen emissions into their exports of textiles and clothing.
High-income exceptions are Australia, New Zealand, and Argentina, which export significant nitrogen embodied in livestock products, the research said.