[SustainableTompkins] World's Most Important Crops Hit by Global Warming Effects

[GayNicholson at aol.com]

cereal grains which evolved in Europe's cool climates don't yield as well  in 
hot areas....
 
World's Most Important Crops Hit by Global Warming  Effects 
By Steve Connor  
The Independent UK  
Monday 19 March 2007  
Global warming over the past quarter century has led  to a fall in the yield 
of some of the most important food crops in the world,  according to one of 
the first scientific studies of how climate change has  affected cereal crops.  
Rising temperatures between 1981 and 2002 caused a  loss in production of 
wheat, corn and barley that amounted in effect to some 40  million tons a year - 
equivalent to annual losses of some £2.6bn.  
Although these numbers are not large compared to the  world-wide production 
of cereal crops, scientists warned that the findings  demonstrated how climate 
change was already having an impact on the global  production of staple foods. 
"Most people tend to think of climate change as  something that will impact 
the future, but this study shows that warming over  the past two decades has 
already had real effects on global food supply," said  Christopher Field of the 
Carnegie Institution in Stanford, California.  
The study, published in the journal Environmental  Research Letters, analysed 
yields of cereals from around the world during a  period when average 
temperatures rose by about 0.7C between 1980 and 2002 -  although the rise was even 
higher in certain crop-growing regions of the world.  
There was a clear trend, showing the cereal crops  were suffering from lower 
yields during a time when agricultural technology,  including the use of 
chemical fertilisers and pesticides, became more intensive.  The study's co-author, 
David Lobell of America's Lawrence Livermore National  Laboratory in 
California, said that the observed fall in cereal yields could be  clearly linked with 
increased temperatures during the period covered by the  study.  
"Though the impacts are relatively small compared to  the technological yield 
gains over the same period, the results demonstrate that  negative impacts of 
climate trends on crop yields at the global scale are  already occurring," Dr 
Lobell said.  
The two scientists analysed six of the most widely  grown crops in the world 
- wheat, rice, maize, soybeans, barley and sorghum.  Production of these crops 
accounts for more than 40 per cent of the land in the  world used for crops, 
55 per cent of the non-meat calories in food and more than  70 per cent of 
animal feed.  
They also analysed rainfall and average temperatures  for the major growing 
regions and compared them against the crop yield figures  of the Food and 
Agriculture Organisation for the period 1961 to 2002.  
"To do this, we assumed that farmers have not yet  adapted to climate change, 
for example by selecting new crop varieties to deal  with climate change," Dr 
Lobell said.  
"If they have been adapting, something that is very  difficult to measure, 
then the effects of warming may have been lower," he said.   
The study revealed a simple relationship between  temperature and crop 
yields, with a fall of between 3 and 5 per cent for every  0.5C increase in average 
temperatures, the scientists said.  
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Gay  Nicholson, Ph.D. 

607-533-7312 (home office)
607-279-6618  (cell)

1 Maple Avenue
Lansing, NY  14882
gaynicholson at aol.com

Sustainable Tompkins 
Program  Coordinator 
w_ww.sustainabletompkins.org_ (http://www.sustainabletompkins.org/) 

Southern Tier Energy$mart Communities
Regional  Coordinator
Cornell Cooperative Extension of Tompkins County
615 Willow  Ave., Ithaca, NY 14850
agn1 at cornell.edu




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