Groundwater depletion raises likelihood of global food crises
27 October 2010
Source: National Geographic
New data on the rate of groundwater depletion around the group show that the world is almost certainly facing a future of food shortages.
A young boy leads his cattle in search of water in Bangladesh.
© 2006 Rezaul Haque, Courtesy of Photoshare
Diminishing groundwater supplies
In an upcoming issue of Geophysical Research Letters, a journal of the American Geophysical Union, Professor Marc Bierkens of Utrecht University in the Netherlands and his colleagues estimate that the rate at which humanity is pumping dry the underground reservoirs that hundreds of millions of people depend upon for food and drinking water more than doubled between 1960 and 2000.
The rate of depletion increased particularly sharply in the early 1990's, which is likely due to escalating groundwater use in China and India.
Food insecurity threats
Although the research team doesn't delve into the implications of their findings, a lot is at stake-especially for the world's food supply. Irrigation, which accounts for 70 percent of world water use, is the principal cause of the groundwater depletion. About 40 percent of the world's food supply comes from the 18 percent of farmland that's irrigated, making irrigated farming a cornerstone of global food security. But in recent decades as more farmers have turned from rivers to groundwater for their water supply, groundwater pumping in many areas has become unsustainable.
High levels of 'water debt'
Just as a bank account shrinks when withdrawals exceed deposits, so does a groundwater account. Water budgets are badly out of balance, throwing many regions into water debt. In effect, farmers are using some of tomorrow's water to meet today's food demands.
The highest rates of water loss are occurring in critical regions of irrigated farming--including the north plain of China, northwestern India, and the central valley of California. In most areas groundwater is not monitored or regulated, so as increasing numbers of wells extract ever more water, the "tragedy of the commons" is playing out on a large scale.
Urgent action needed
With modern satellite capabilities and new modeling and monitoring techniques, it is now possible to know what is happening to our water supplies underground. The picture is not good. The challenge now is to encourage the adoption of more efficient irrigation systems, more appropriate cropping patterns, and other measures to bring the world's groundwater accounts into balance. The future food security of hundreds of millions of people depends on this.