Physical and virtual nutrient flows in global telecoupled agricultural trade networks

Agricultural trade significantly contributes to sustainable development by bolstering global food security and economic growth. Globalization has tripled the economic value of global agricultural trade between 2000 and 2016, impacting the environment and natural resources. Cross-border trade interlinks socioeconomic and environmental sustainability, creating telecoupled flows of nitrogen (N) and phosphorus (P) within agricultural trade networks. The telecoupling framework highlights the socioeconomic and environmental interactions across distances, facilitating the evaluation of material flows and their effects. Understanding the environmental impacts of nutrient flows in these networks is critical for sustainable agricultural trade and nutrient management. Previous research has examined N or P flows individually or focused on specific aspects like virtual nutrient flows. However, a comprehensive analysis of both physical and virtual N and P flows simultaneously is lacking, hindering the comparative analysis of their effects and evaluation of their telecoupling impacts on a global scale. This study addresses this gap by using the global agricultural trade matrix and the telecoupling framework to quantify physical and virtual N and P flows in global agricultural trade between 1997 and 2016.

Existing literature highlights the increasing flows of water, energy, carbon, and other materials in agricultural trade networks, raising environmental concerns. Nitrogen (N) and phosphorus (P) are essential for agricultural productivity, and their transfer through trade has significantly altered the global nutrient cycle. Studies have estimated increases in N and P flows through global food and feed trade, accounting for significant portions of total global production. Research has also focused on virtual nutrient flows, which represent nutrients required for product production. However, no studies have comprehensively measured both physical and virtual N and P flows simultaneously, making a complete assessment of their diverse effects and telecoupling effects on a global scale challenging.

This study utilized the global agricultural trade matrix statistics and the telecoupling framework to calculate the physical and virtual flows of N and P for 320 agricultural products traded among 221 countries/regions from 1997-2016. The methodology involved calculating physical nutrient flows by multiplying the weight of traded agricultural products by their N or P content. Virtual nutrient flows considered various production inputs (fertilizers, seeds, irrigation water, atmospheric deposition, biological N fixation). The study used source-sink analysis to calculate virtual nutrients, incorporating both fertilizer and natural inputs for greater accuracy. Sending-receiving effects were calculated to assess nutrient redistribution. Spillover effects, considering re-export trade and differences in production efficiency, were also quantified. Finally, telecoupling effects, encompassing sending-receiving and spillover effects, were determined. Data was sourced from the FAOSTAT trade matrix, encompassing approximately 95% of global caloric consumption.

Total physical and virtual nutrient flows increased significantly from 1997 to 2016. Physical flows primarily involved crop products, while virtual flows were significantly larger and involved both crop and animal products. Asia was the largest net receiver of nutrients, while North and South America were major net senders. China was the largest net importer, with a substantial increase in imports. The US and Brazil were the largest net exporters. The US-China soybean trade was a major driver of physical N flows. Virtual N and P flows were often much larger than physical flows. The largest nutrient-sending systems were in North and South America, exporting to East Asia and Southeast Asia. Europe primarily traded nutrients within its own region. From a global perspective, physical N and P flows reached nearly 27% of total global N and P consumption in agricultural products in 2016, while virtual flows accounted for about 33.7% of total global soil nutrient inputs. The study revealed significant positive sending-receiving effects, indicating nutrient savings. Spillover effects also increased over time, with wheat, corn, rapeseed, and soybean exhibiting the largest effects. Overall, telecoupling effects increased over time, with sending-receiving effects dominating.

The uneven structure of nutrient flows highlights the concentration of nutrient exports in a small number of countries. Trade liberalization and increasing demand drive production expansion in sending systems, often leading to environmental damage (e.g., deforestation in Brazil). Large nutrient exports expose net-sending systems to risks of soil nutrient depletion. Virtual nutrient flows transfer the environmental burden from receiving to sending systems. Importing countries benefit from improved food security and supplement domestic nutrient reserves. However, importing virtual nutrients shifts environmental burdens and potentially increases environmental risks in receiving countries due to increased consumption and land-use changes. While global agricultural trade has a positive effect on N and P resource saving, inefficient flows lead to unnecessary losses. Addressing these issues requires adjustments to production and trade structures, promoting efficient nutrient utilization, and reducing meat consumption. The telecoupling framework is crucial for understanding the complex interactions and impacts of agricultural trade on global nutrient cycles.

This study demonstrates the significant and growing impact of physical and virtual nutrient flows in global agricultural trade networks. The findings highlight the need for strategies to reduce inefficient flows, promote sustainable nutrient management in both sending and receiving systems, and incorporate environmental considerations into trade policies. Future research should refine data collection to better capture the nuances of the supply chain and the roles of various actors in the telecoupling system.

This study did not account for differences in nutrient content between export and non-export products, potentially affecting precision. Further research is needed to explore the roles of different actors (producers, traders, consumers, governments) in influencing trade flows and spillover effects. Improved data with greater detail on upstream and downstream supply chains will enhance understanding of the impact of agents on trade flows and spillover effects.