How agricultural shock waves ripple across the globe

Global food trade creates a complex network of dependencies. One country’s access to a commodity often hinges on another’s successful harvest. Now, a team of researchers in Austria have built a model that predicts how much a shock to one nation’s agricultural system can impact food availability across the world. This tool, presented in Nature Food, could help predict disruptions to food supplies caused by crises such as the war in Ukraine.

The team first built a model that represents the typical network of food production and trade for 125 food types across nearly 200 countries. This baseline scenario—built largely with information provided by the United Nations’ Food and Agriculture Organization for the year 2013—includes data on how much of each particular food a country produces, as well as how much of that food is eaten within the country, stored for future years, or exported. It also incorporates data on how much of a given food is ultimately used to produce other foods.

The model represents how the trade network runs, explains study coauthor and theoretical physicist Stefan Thurner, the president of Complexity Science Hub Vienna in Austria. “Then, you can perturb that through localized shocks.”

The researchers can enter a hypothetical shock into the trade network by reducing or entirely eliminating the production of one or more foods in a particular region.

For example, Thurner and his team adjusted the production of all foods in Ukraine to zero to explore just how much of the global food supply depends on this nation at war. The model then projects the resulting loss of food in other countries that rely on Ukrainian exports, either directly or indirectly. Southern Asia, for example, would lose over two-thirds of its sunflower oil supply. Eastern Asia and northern Africa would lose nearly half. In Europe, access to maize would plummet to a loss of around 40% in the north and 30% in the south—a decline caused by both the lack of Ukrainian maize and the loss of seeds exported from Ukraine that are used to grow the grain on European farms.

Not all regions are tied so closely to Ukraine’s agriculture. North America’s and Australia’s food supply chains would go largely unchanged.

The model can also indicate how a nation’s loss of one single food—rather than their entire agricultural system—could affect other countries and other foods. It predicts, for example, that if Ukraine suddenly halted all maize production, poultry availability in southern Europe would drop by 15.4% because growers there rely on Ukrainian grain to feed their livestock.

The model is also available for public use as an interactive online data visualization tool. This version only allows users to completely eliminate the production of any one food in any single country. A world map then shows which countries could be affected and how.

But these food shortage projections represent a worst-case scenario. The Russian invasion of Ukraine has not completely halted the country’s agricultural production. And countries often adapt to disruptions in food supply chains by finding new trade partners or making substitutions—swapping, perhaps, one grain type for another.

Although the model reveals which countries will be impacted, it does have limits, notes international trade expert Sharat Ganapati, an economist at Georgetown University in Washington, DC, who was not involved in the study. “It is not going to tell you how much they are going to be impacted,” he says. For that information, he says, a future model should incorporate estimates of how easily a country could switch trade partners or substitute foods.

But understanding the worst-case scenario could be informative at the onset of a sudden threat to agriculture. “You see how hard it’s going to be to replace things, if it is necessary to replace something at all,” Thurner says. “Then, you could start thinking weeks ahead before the problem itself reaches your region.”

This approach can also identify especially vulnerable countries that stand to lose large portions of their food supply—countries that may not have the means to compete for imports from other trading partners that sell at a higher price. “You figure out what is really clearly going to be a problem,” Thurner says.

“If [this model] were available at the moment of a shock—be it a supply shock brought by a war or climate induced-shocks, that could be interesting,” says Caitlin Welsh, director of the Global Food Security Program at the Center for Strategic and International Studies in Washington, DC, who was not involved in the study. In the absence of a crisis, however, she doubts that countries would use this model to assess whether dependence on any single trade partner could leave them vulnerable. “That’s not the economics of trade,” she says. “Importing countries are always going to go to the lowest [cost] supplier.”

Thurner says their next step is to incorporate Ukraine’s actual drop in export numbers—rather than a complete loss—in hopes of devising something closer to real-world scenarios. They’ll then test how closely the model predicts the ripple effects of war on food supplies across the globe.