Global food producers and traders should better consider the amount of water it takes to produce crops in different regions, and consider how this affects local water scarcity, say researchers writing in Ecological Economics.
The team, led by Anne Biewald from the Potsdam Institute for Climate Impact Research, Germany, used data of the year 2005, to assess the impact of agriculture and food commodity trading on water scarcity. They noted that such trading always also involves the trade of 'virtually embedded' water that is used throughout production, and the amount of that water depends heavily on the climatic conditions in the production region.
For instance, the team noted that it take 2,700 litres of water to produce 1 kilo of cereals in Morocco, while the same kilo produced in Germany uses only 520 litres of water.
"Agriculture accounts for 70 percent of our global freshwater consumption and therefore has a huge potential to affect local water scarcity," explained Anne Biewald.
By analysing the impact of trade on local water scarcity, Biewald and her colleagues found that it is not the amount of water used that counts most, but the origin of the water.
"Our analysis shows that it is not the amount of water that matters, but whether global food trade leads to conserving or depleting water reserves in water-scarce regions," said Biewald - who noted that the concept of 'virtual water' could not identify the regional water source as it uses national or even global averages.
"With our study we could show that local water scarcity is alleviated through imports of agricultural goods in parts of India, Morocco, Egypt and Pakistan, as well as intensified through exports in parts of Turkey, Spain, Portugal, Afghanistan and the US," wrote the team.
'Virtual water' trade
By combining biophysical simulations of the virtual water content of crop production with agro-economic land-use and water-use simulations, the German research team were able for the first time to determine the positive and negative impacts on water scarcity through international trade of crops, livestock and feed.
These effects were analyzed with high resolution on a sub-national level to account for large countries like India or the US with different climatic zones and relating varying local conditions regarding water availability and water productivity.
Previously, these countries could only be evaluated through national average water productivity, they noted.
Despite the fact that Europe alone exports virtual water in food crops worth $3.1 billion USD, the scientists found that international trade of food crops today globally accounts for water savings worth approximately $2.4 billion USD.
The authors also noted that trade can also improve the efficiency of crop and livestock production on a global scale when regionally different efficiencies are taken in to account: one kilo of beef for instance can be produced with much less input feed in the US than in Africa, they noted.
Therefore it may be more economical for the world to have regions specialising in certain products and exporting them to others, suggested the team.
"In contrast to popular perception, global food trade and the related virtual water flows indeed offer the possibility of relieving water stress and making global water use more efficient," revealed Hermann Lotze-Campen - co-author of the study,
"When it comes to the implementation of policy instruments which affect global trade – such as trade liberalization, import taxes or agricultural subsidies –, decision makers have to take into account the indirect effects on water as well."
"To connect international food trade to regional water scarcity can contribute to advance this debate."