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Coping with water scarcity in a globalized world

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Plumbing the global trade in virtual water

When food commodities are exported, so too is the water used to produce them. A new database maps the complexity and resilience of this invisible network.


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.

Water footprint

One criticism of Allan’s virtual water concept was that it could not be used as an indicator of environmental harm, as it treated all water extraction methods as equal and did not assess whether this water use was sustainable. “It’s one thing to take away 1 000 m3 of water from Canada, where water is abundant, another to take it from Spain, where it is not,” explains Laio. To remedy this, Laio and his colleagues introduced an environmental cost of extraction, identifying the likely water source – rainfall or surface/groundwater – used to grow and process each food, and the impact on other users. The data can also be used to model future scenarios. “Among the main goals of CWASI is the prediction of how much water will move in the future,” adds Laio. “This is akin to trying to understand how many pounds of apples Italy will export in 2050, not an easy task.” His team identified statistically significant cofactors of these fluxes, such as the populations of the importing and exporting countries, the distance between the two countries, the wealth of each country, and many more. “We are trying to understand how the system is evolving in terms of connectivity, resilience,” he says.

Future shock

The second part of the CWASI project focused on the impact of crises in such an interconnected water trade. Laio cites the example of the 1998 economic crisis in Argentina. “Italy was importing a lot of commodities from Argentina, and with the economic crisis, the Argentinian production capacity dropped 50 % in 1 year in some products,” he notes. “Italy could not import any more, and that meant importing from elsewhere.” Other countries reliant on Argentinian exports, however, were left wanting. “On one hand, globalised systems are more resilient to crisis,” says Laio. “But connected systems have the problem that crises can be propagated in highly unequal ways, hitting more profoundly in less wealthy economies of the world.” The CWASI database is now available on the Zenodo repository for other researchers to use, and Laio and his team welcome contributions and improvements from the scientific community. The database is also available for the general public on the project website, where people can play with virtual water data through a user-friendly interface.


CWASI, water, food, commodities, fluxes, trade, embedded, virtual water, scarcity, network, export

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