Scientists scrutinize elements flowing through food trade

A flood of nitrogen and phosphorus increase as global food trading steps up, with unknown environmental consequences. Explored in Nature Communications

American soybean farm
An American soybean farm

Nitrogen and phosphorus are two elements essential for all life on earth yet how much and where are crucial to global sustainability. An international group of scientists show how the two elements flow through the booming global food trade and how to protect both the environment and markets.

The two elements are abundant in fertilizer, soil and manure. In Nature Communications, scientists from Michigan State University Center for Systems Integration and Sustainability (MSU-CSIS) with colleagues across the world explore what impacts as global diets change and crops and animal products are traded increasingly. Flows of nitrogen within the global food and animal feed trade increased by eightfold during 1961–2010, accounting for one-third of the total nitrogen produced in the world then. Phosphorus flows in global agricultural trade increased by 750% in that time period.

But, researchers note, the flows of nitrogen and phosphorus haven’t been studied together at a global scale.

“Examining the global flows of nitrogen and phosphorous simultaneously can help compare their effects across the world,” said co-author Jianguo “Jack” Liu, Rachel Carson Chair of Sustainability and CSIS director. “The findings can be useful to enhance the benefits and reduce the risks brought by agricultural trade flows.”

The group turned to the conceptual framework of telecoupling, which allows scientists an integrated way to look at how people and nature interact across the world and provides a new language to look at the big picture and at details simultaneously.

The group found that overall, the growth of global trade saved on nitrogen and phosphorus, the finer points demanded attention. They also noted that countries who lacked efficiency in production would do well to improve technology that would trim both the waste and pollution of the elements.

The work also explored virtual nutrients – a way to represent how the elements can move across trade because they were used in growing or producing the products. This perspective shows an oft-hidden environmental burden can be shifted to exporters. For example, the U.S. suffered pollution when the pork and chicken it produced to send to Japan resulted in 0.11 million tons of nitrogen leaking into the to the local environment.

“Physical and virtual nutrient flows in global telecoupled agricultural trade networks” was written by Xiuzhi Chen, Yue Hou, Thomas Kastner, Liu Liu, Yuqian Zhang, Tuo Yin, Mo Li, Arunima Malik, Mengyu Li, Kelly R. Thorp, Siqi Han, Yaoze Liu, Tahir Muhammad and Yunkai Li.

The work was supported by National Natural Science Foundation of China, The National Science Foundation, the National International Postdoctoral Exchange Fellowship Program, World Sustainability Award, Gunnerus Award in Sustainability Science, Deutsche Forschungs Gemeinschaft (German Research Foundation), German Federal Ministry for Economic Cooperation and Development, Natural Science Foundation of Guangdong Province and Australian Research Council Grants.

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