jueves, 30 de marzo de 2017

Crop-specific contribution to groundwater depletion worldwide in 2010. The pie charts show fractions of groundwater depletion for irrigation (GWD) of major crops by country, and their sizes indicate total GWD volume. The background map shows groundwater stress index (corresponding to overexploitation when larger than one) of major aquifers. Some countries have overexploited aquifers but no pie chart is shown because groundwater use is not primarily related to irrigation.

Recent hydrological modelling and Earth observations have located and quantified alarming rates of groundwater depletion worldwide. This depletion is primarily due to water withdrawals for irrigation, but its connection with the main driver of irrigation, global food consumption, has not yet been explored. Here we show that approximately eleven per cent of non-renewable groundwater use for irrigation is embedded in international food trade, of which two-thirds are exported by Pakistan, the USA and India alone. Our quantification of groundwater depletion embedded in the world’s food trade is based on a combination of global, crop-specific estimates of non-renewable groundwater abstraction and international food trade data. A vast majority of the world’s population lives in countries sourcing nearly all their staple crop imports from partners who deplete groundwater to produce these crops, highlighting risks for global food and water security. Some countries, such as the USA, Mexico, Iran and China, are particularly exposed to these risks because they both produce and import food irrigated from rapidly depleting aquifers. Our results could help to improve the sustainability of global food production and groundwater resource management by identifying priority regions and agricultural products at risk as well as the end consumers of these products.

Embedded groundwater depletion in international trade of crop commodities in 2010.Volumes are in units of cubic kilometres per year. The top ten importers are shown in bold font and the top ten exporters are underlined. Ribbon colours indicate the country of export. Note that, for clarity, we display only the links with a weight of at least 1% that of the largest link (that is, the top 1.8% links which account for 81% of total flow and involve 71 countries.

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