A new study by researchers at the University College London and NASA’s Goddard Institute of Space Studies in New York City shows that 11 percent of the global non-renewable groundwater drawn up for irrigation goes to produce crops that are then traded on the international market.
According to the report, two-thirds of the exported crops that depend on non-renewable groundwater are produced in Pakistan (29 percent), the United States (27 percent), and India (12 percent).
Wheat, rice, sugar, cotton and maize are among the essential internationally traded crops in the global economy.
To produce these crops many countries rely on irrigated agriculture that accounts for about 70 percent of global freshwater withdrawals, according to the United Nations Water program.
One freshwater source is underground aquifers, some of which replenish so slowly that they are essentially a non-renewable resource.
“It’s not just individual countries that experience groundwater depletion, but also their trade partners,” said lead author Carole Dalin of the University College London. “When people consume certain imported foods, they should be aware that they can have an impact on the environment elsewhere.” The results were published March 30 in Nature.
Dalin and her colleagues used trade data on countries’ agricultural commodities from the United Nations Food and Agriculture Organization. They then combined it with a global hydrologic model — validated with ground information and NASA satellite data — to trace the sources of water used to produce 26 specific crop classes from their country of origin to their final destination. Their analysis is the first to determine which specific crops come from groundwater reservoirs that won’t renew on human time-scales and where they are consumed.
“Say I’m in Japan, and I’m importing corn from the United States,” said co-author Michael Puma of NASA’s Goddard Institute for Space Studies and Columbia University in New York City. “It’s important from Japan’s perspective to know whether that corn is being produced with a sustainable source of water, because you can imagine in the long term if groundwater declines too much, the United States will have difficulty producing that crop.”
Globally, 18 percent of all crops grown are traded internationally. The remaining 82 percent stays in country for the domestic market. However, the amounts of various exported crops produced using unsustainable groundwater rose significantly between 2000 and 2010. India, for example, saw its exports of groundwater-depleting crops double in that period, while Pakistan’s rose by 70 percent and the United States’ rose by 57 percent.