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Climate change warning over food production 18:17 26 April 2005 NewScientist.com news service Fred Pearce Related Articles Rice yields plunging due to balmy nights 29 June 2004 Heatwave's warning for future of farming 23 August 2003 Intensive agriculture has reduced global warming 12 July 2001 Search New Scientist Contact us Web Links FACE Steve Long’s lab Chinese Academy of Agricultural Science The Royal Society Climate change is set to do far worse damage to global food production than even the gloomiest of previous forecasts, according to studies presented at the Royal Society in London, UK, on Tuesday.
“We need to seriously re-examine our predictions of future global food production,” said Steve Long, a crop scientist at the University of Illinois at Urbana-Champaign, US. Output is “likely to be far lower than previously estimated”.
Most researchers believe that higher temperatures and droughts caused by climate change will depress crop yields in many places in the coming decades. But a recent consensus has emerged that rising atmospheric concentrations of carbon dioxide could come to the rescue. The gas thought to be behind global warming could also speed up photosynthesis, counteracting the negative effects of warming and even ushering in an era of bumper crops.
But Long told the two-day meeting on crops and future climate that this conclusion was a dangerous illusion. It was, he said, based on results from tests in gas chambers and small greenhouses known to be unreliable.
Long reported instead on the findings of four studies in the US, China and Japan that all test crops in open fields. In these Free-Air Concentration Enrichment experiments, gases such as CO2 were piped into the air around plants - a world first.
Ozone-unfriendly The FACE experiments showed that for all four of the world’s main food crops - maize, rice, soybean and wheat - the real-world fertilization effect was only half as great as predicted by the contained experiments.
Meanwhile, in some FACE experiments, Long added a new variable not factored into previous studies. He puffed doses of ozone into the fields to simulate the expected rise in ozone smogs due to higher temperatures - and yields crashed. A 20% increase in ozone levels cut yields by 20%, he said.
Increases in ozone levels of this level are predicted for Europe, the US, China, India and much of the middle east by 2050. If Long’s findings prove correct, even CO2 fertilisation will not prevent the world’s crop yields from declining by 10% to 15%.
Profound implications The implications for some of the world’s most populous countries could be profound. Xiong Wei of the Chinese Academy of Agricultural Science in Beijing presented data at the meeting suggesting that the country of 1.3 billion people could expect “more positive than negative impacts on China’s food production”.
He said CO2 fertilisation would more than counteract crop losses from rising temperatures. But Long said his new findings suggest China’s food production might fall rather than rise.
Long’s research is partly sponsored by the US government’s department of agriculture, which has previously been confident in its predictions of farmers’ ability to withstand climate change.
The Royal Society conference also heard about dangerous temperature thresholds that could destroy crops overnight and give rise to famine.
According to Andrew Challinor of the University of Reading, UK, climate change will mean tropical countries like India will face short periods of super-high temperatures - into the high 40s Celsius. These temperatures could completely destroy crops if they coincide with the flowering period.
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