【持続可能性】食品貿易によって地下水源が枯渇する過程

A vast majority of the world’s population live in countries that source most of their imported food crops from regions that overexploit groundwater sources to produce these crops, reports a study in Nature this week. The identification of countries, crops and food trade relationships that are depleting groundwater supplies may help to drive efforts to improve the sustainability of global food production and groundwater resource management.

Aquifers - large underground reservoirs of water - are rapidly depleting in key food-producing regions, primarily owing to water withdrawals for irrigation. This effect threatens the sustainability of food production both locally and globally via international food trade. The detailed impact on groundwater depletion caused by global food trade is not well understood, but Carole Dalin and colleagues take steps towards quantifying this relationship. They find that approximately 11 per cent of non-sustainable groundwater extraction is linked to food trade, with Pakistan, the USA and India accounting for two-thirds of the global export totals, mostly through rice and wheat crops. Mexico, Iran, China and the USA are highlighted as being at high risk for food and water insecurity because they both produce and import food irrigated from rapidly depleting aquifers.

The authors propose that groundwater depletion for irrigation could be minimized in a number of ways, such as growing more drought-resistant crops or regulating groundwater pumping. In addition, they suggest that sustainable irrigation practices need to be supported by countries that import food crops from stressed aquifer systems.