Plumbing the global trade in virtual water

Every year, trillions of dollars of agricultural products are traded around the world. Embedded in this food is the water required to grow it. This is known as virtual water, a concept coined by geographer Tony Allan in 1993. The EU-funded CWASI project sought to better understand this global trade in virtual water. “When you eat some bread in Italy, there is a good chance that the wheat has been grown in Moldova, or another country,” notes researcher Francesco Laio. Although trade between two countries may be balanced in economic terms, one country may be effectively exporting its water if it sells crops that need intensive irrigation and imports foods that do not. To map the global trade in virtual water, Laio and his colleagues at the Polytechnic University of Turin in Italy collected data on the international trade in food commodities from 1961 to 2016, identifying the origin of 370 different foods. In total, the network covers more than 15 000 international fluxes in commodities.