Virtual water trade flows and savings under climate change

摘要

The international trade of food commodities links water and food systems,with important implications for both water and food security. The embodiedwater resources associated with food trade are referred to as "virtual watertrade". We present the first study of the impact of climate change on globalvirtual water trade flows and associated savings for the year 2030. In orderto project virtual water trade and savings under climate change, it isessential to obtain projections of both bilateral crop trade and the virtualwater content of crops in each country of production. We use the Global TradeAnalysis Project model to estimate bilateral crop trade under changes inagricultural productivity for rice, soy, and wheat. We use the H08 globalhydrologic model to determine the impact of climatic changes to cropevapotranspiration for rice, soy, and wheat in each country of production.Then, we combine projections of bilateral crop trade with estimates ofvirtual water content to obtain virtual water trade flows under climatechange. We find that the total volume of virtual water trade is likely to godown under climate change, due to decreased crop trade from higher cropprices under scenarios of declining crop yields and due to decreased virtualwater content under high agricultural productivity scenarios. However, thestaple food trade is projected to save more water across most climate changescenarios, largely because the wheat trade re-organizes into a structurewhere large volumes of wheat are traded from relatively water-efficientexporters to less efficient importers.