Global warming has cut about US$5 billion worth of the world's most
commonly grown grains over 20 years, according to a new study. Warming
temperatures from 1981 to 2002 cut the combined production of wheat,
corn, barley and other crops by 40 million tonnes per year, according to
the peer-reviewed study published in Environmental Research Letters on
Friday.
"Most people tend to think of climate change as something that will
impact the future," Christopher Field, a co-author on the study and
ecology expert at the Carnegie Institution in Stanford, California, said
in an e-mail response to questions.
"This study shows that warming over the past two decades has already had
effects on global food supply," he added.
Not every scientist agrees that agriculture is suffering from warmer
temperatures.
A draft UN report obtained by Reuters on Thursday said warming is
expected to turn the planet a bit greener by spurring plant growth, but
crops and forests may wilt beyond mid-century if temperatures keep
rising. That report, by the Intergovernmental Panel on Climate Change,
will be released on April 6.
Field said the Carnegie study was the first to estimate how much global
food production has already been affected by climate change. It was
funded by the Carnegie Institution and the Lawrence Livermore National
Laboratory, which is managed by the University of California for the US
government.
Average global yields for several of the crops suffered from warmer
temperatures, with yields dropping by about 3 to 5 percent for every 1
degree Fahrenheit increase, the study said.
Average global temperatures increased by about 0.7 degree F during the
study period, with even larger changes in several regions.
If the past is an indication, agriculture will also suffer going
forward, Field said. "We expect future warming to continue to be a drag
on yields, essentially like driving with the parking brake engaged."
The cereal crops hit by global warming account for at least 55 percent
of non-meat categories consumed by humans, according to the study. They
also contribute more than 70 percent of the world's animal feed.
Farmers can adapt to warmer temperatures through changing crop planting
times, the varieties they grow, or the locations used for each crop,
Field said. He said in the past farmers have been very adaptable to
environmental challenges, but adaptation to warming can take years.
(Por Timothy Gardner,
Planet Ark, 19/03/2007)