9 June 2011

Climate change will have major impacts on the availability of water for growing food and on crop productivity in the decades to come. This is the conclusion drawn by a new report from the UN Food and Agriculture Organisation (FAO), based in Rome.

The report, Climate Change, Water, and Food Security, is a comprehensive survey of existing scientific knowledge on the anticipated consequences of climate change for water use in agriculture.

The consequences outlined in the report include reductions in river runoff and aquifer recharges in the Mediterranean and semi-arid areas of the Americas, Australia and southern Africa - regions that are already water-stressed. In Asia, large areas of irrigated land that rely on snowmelt and mountain glaciers for water will also be affected, while heavily populated river deltas are at risk from a combination of reduced water flows, increased salinity, and rising sea levels.
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The FAO also points out the loss of glaciers, which support around 40 percent of the world's irrigation, will eventually impact the amount of surface water available for agriculture in key producing basins. The organisation says increased temperatures will lengthen the growing season in northern temperate zones, but will reduce the season almost everywhere else; this will cause the yield potential and water productivity of crops to decline.

Alexander Mueller, FAO Assistant Director General for Natural Resources, said, "Both the livelihoods of rural communities as well as the food security of city populations are at risk, but the rural poor, who are the most vulnerable, are likely to be disproportionately affected."

Responding to the challenge

The FAO report also looks at actions that can be taken by national policymakers, regional and local watershed authorities, and individual farmers to respond to these new challenges.

One key area requiring attention is improving the ability of countries to implement effective systems for ‘water accounting' - the thorough measurement of water supplies, transfers, and transactions in order to inform decisions about how water resources  can be managed and used under increasing variability.

"Water accounting in most developing countries is very limited, and allocation procedures are non existent, ad hoc, or poorly developed," the report reveals. It recommends, "Helping developing countries acquire good water accounting practices and developing robust and flexible water allocations systems.”

Furthermore, it suggests, at the farm level growers can change their cropping patterns to allow earlier or later planting, reducing their water use and optimizing irrigation. Yields and productivity can be improved by shifting to soil moisture conservation practices, including zero- and minimum tillage. Planting deep-rooted crops would allow farmers to better exploit available soil moisture. image expired