Sir

Understanding our auditory pathways may inform us about why only some musical experiments are successful, page 598 Laurel Trainor

Your News Feature 'More crop per drop' (Nature 452, 273–277; 2008) mentions that China has “unconsciously” turned to 'virtual-water' imports by importing food that requires large amounts of water to produce. Officially, however, the Chinese government continues to advocate self-sufficiency in food because it regards reliance on international food import as a threat to domestic security.

In spite of this strict policy, the annual virtual-water import through food trade increased sharply from 30 billion cubic metres in the 1990s to an average of 71 billion cubic metres a year between 2000 and 2004 (J. Liu et al. Water Int. 32, 78–90; 2007). The increase is mainly due to the import of water-intensive crops, particularly soya beans. Virtual water is politically silent and economically invisible, and importing it is current practice in China.

China is confronted with water scarcity in several parts of the country, particularly in the North China Plain and the northwestern regions. Several studies have been published on the benefits of incorporating a virtual-water strategy in regional-water management and in food-trade policies for arid regions. These all indicate that importing virtual water into the North China Plain may well be more efficient than transferring 'real' water through the South-to-North Water Transfer Project — a controversial initiative now under construction to divert water from the Yangtze River to northern China (H. Yang and A. Zehnder Water Resour. Res. 43, W12301; 2007).

If a virtual-water strategy had been taken into account in a feasibility study, the decision to invest half-a-billion euros in the transfer scheme might have been different. It would benefit China's development if the political silence around virtual-water transfer were broken and if the issue received more attention in planning water resources.