Rice is one of the main globally traded food products and staple food of an increasing population in Asia and Africa.
Photo: ©IFAD/Mathilde Lefebvre

Excessive groundwater use threatens food supply

Cultivation of internationally traded foods is taking up growing volumes of non-renewable groundwater. This is leading to dwindling reserves of groundwater, posing a global threat to future availability of food and water.

An international research team from University College of London (UK), the Senckenberg Research Institute, Frankfurt/Main (Germany), the University of Klagenfurt (Austria), NASA and the International Institute for Applied Systems Analysis (Austria) is warning of dwindling groundwater reserves.

Rice from Pakistan, wheat from Egypt and cotton from the USA – where the origin of these and other agricultural commodities are concerned, German consumers are happy to be international. Where rain is in short supply in arid or semi-arid climates, the difference is made up from irrigation using groundwater, as the experts explain in the study, which was published in April in the journal “Nature”. And this is the problem. “The quantity of non-renewable groundwater used for this – water which is replaced barely or not at all by rain or seepage of surface water – has increased by 22% worldwide between 2000 and 2010. 11% of this excess use of groundwater goes to irrigated cultivation of internationally traded foods,” explains Dr Thomas Kastner, Senckenberg Biodiversity and Climate Research Centre and University of Klagenfurt, a co-author of the new Nature study.

The main exporter of agricultural products cultivated with non-renewable groundwater is Pakistan (29% of the non-renewable groundwater used worldwide to grow traded agricultural products), followed by the USA (27%) and India (12%). On the import side, China leads the table (9%) of non-renewable groundwater used worldwide to grow traded agricultural products, followed by the USA and Iran. For Germany, the figure is 2.5%, well ahead of Germany’s share in the world population.

Exporters of products which use excessive amounts of groundwater to grow may profit in the short run, but in the long term this form of agriculture will be unsustainable, the experts warn. Even for importers like Germany, the trend has its dangers. “Although there’s no shortage of groundwater in Germany, we’re importing food which was grown with excessive groundwater use. In the long term, the supply could dry up, or prices could rise sharply,” Dr Kastner warns.

The list of internationally-traded products which have the most non-renewable groundwater “in their tank” is headed by rice (29%), followed at a distance by wheat (12%) and cotton (11%), maize (4%) and soybeans (3%). Farming in drier regions frequently uses conventional sprinkler irrigation systems. These are an object of criticism because they use 20-50 times the volume of groundwater estimated to be renewable.

Dr Carole Dalin of University College London is the lead author of the study, and is worried: “Where and how products are grown is extremely important, because basic foods like bread and rice could have adverse effects on global water reserves. If consumers and producers can’t agree on strategies to maximise sustainability of groundwater use, stable food supplies and prices will be at risk for much of the world population. In the course of climate change, there will also be increasingly frequent droughts in many regions. We must not exhaust the groundwater supplies needed to compensate for this.”

Publication: Dalin, C., Wada, Y. Kastner, Th. And Puma, M.J. (2017): Groundwater depletion embedded in international food trade. Nature. Doi: 10.1038/nature21403

(Senckenberg Research Institute/wi)