Farms must feed a growing population with a minimal impact on the environment.
International experts have called for urgent changes to the way water is used in farming throughout Asia.
The report — jointly produced by the International Water Management Institute (IWMI) based in Battaramulla, Sri Lanka, the Food and Agriculture Organization of the United Nations and the Asia-Pacific Water Forum — warns that Asian countries must modernize their ageing irrigation systems if they are to produce enough food to feed their growing populations in the future.
Asia contains 70% of the world's 277 million hectares of irrigated land. Most of the irrigation infrastructure was built in the 1960s and 1970s during the Green Revolution that allowed Asian agriculture to flourish. For example, from 1970 to 2007, cereal production in South Asia increased by 137% but used only 3% more land. Today, 73% of the water consumed globally for agriculture is used in Asia.
The report notes that the large-scale, state-funded irrigation systems that powered the Green Revolution helped Asian countries to become self-sufficient in food production, and reduced poverty by creating jobs in rural areas. But these systems had many negative consequences for the environment, such as water pollution and reduction of biodiversity. By lowering food prices, they also discouraged further investment in irrigation systems.
The report was motivated by the spike in food prices in 2007–08, says Aditi Mukherji, one of the lead authors. That food crisis reminded people of the "imminent threat in the 1960s and 1970s that Asia wouldn't be able to feed its population", says Mukherji. "But the face of Asia has changed a lot since then." More people now live in cities and expect a more diverse diet, so demand for meat and fruit has risen, yet the irrigation systems were designed principally for cereal production.
“The region is clearly on a dangerous path. James Famiglietti , UC Irvine”
"A lot of 1970s irrigation had to do with canals — surface irrigation," says Colin Chartres, director-general of the IWMI. These surface-irrigation systems have fallen into disrepair since the 1990s for a variety of reasons, including poor maintenance by governments. Many were not set up to properly cater to farmer's needs and are failing to provide sufficient water for crops. The main alternative to these old irrigation systems is allowing farmers to tap directly into groundwater themselves — known as atomistic irrigation. The report backs this form of irrigation, as long as it is tightly regulated.
The unregulated use of groundwater means that although surface irrigation has been shrinking in Asia, the total area of irrigated land has been expanding. As demands for water in agriculture have increased, the limited supplies are becoming scarcer, says the report.
"This report aims to increase the productivity of irrigation, not by using more water but by making irrigation systems more efficient," says Chartres.
Two recent papers show that groundwater supplies in Asia have been decreasing much faster than was previously thought1,2. James Famiglietti of the University of California, Irvine, a co-author of one of these studies1, says: "The region is clearly on a dangerous path. The severity of the problem is equal to that of climate change, maybe more so, and may well be exacerbated by it. Inaction is not an option."
But, he adds, "Groundwater resources are under stress on most of the continents." In the United States for example, irrigation demand is putting tremendous pressure on groundwater both in California's Central Valley and in the Ogallala aquifer in the High Plains in the centre of the country.
The report calls for more education for farmers and others working in the irrigation sector, and for investment in programmes to cut the overall need for water — such as building better roads so that more crops get to market. The authors also suggest involving the private sector in managing the irrigation systems to take some of the burden off governments.
"We're optimistic," adds Chartres. "The 2007–08 food crisis caught us by surprise and it was a wake-up call. If the countries implement policies to help farmers along the lines suggested in the report, it should be possible to provide more food [for Asia] in the next 30–40 years."
Rodell, M., Velicogna, I. & Famiglietti, J. S. Nature advance online publication doi:10.1038/nature08238 (2009).
Tiwari, V. M., Wahr, J. & Swenson, S. Geophys. Res. Lett. advance online publication doi:10.1029/2009GL039401 (2009).
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