Global Food Supplies at risk from Global Warming*

The tests provided projections for maize, rice (pictured), sorghum,
soybean and wheat - the world's most important crops in terms of global
grain production.

by Staff Writers
Champaign IL (SPX) Aug 08, 2006

Open-air field trials involving five major food crops grown under
carbon-dioxide levels projected for the future are harvesting
dramatically less bounty than those raised in earlier greenhouse and
other enclosed test conditions - and scientists warn that global food
supplies could be at risk without changes in production strategies.

The new findings are based on on-going open-air research at the
University of Illinois at Urbana-Champaign and results gleaned from five
other temperate-climate locations around the world. According to the
analysis, published in the June 30 issue of the journal Science, crop
yields are running at about 50 percent below conclusions drawn
previously from enclosed test conditions.

Results from the open-field experiments, using Free-Air Concentration
Enrichment (FACE) technology, "indicate a much smaller CO2 fertilization
effect on yield than currently assumed for C3 crops, such as rice, wheat
and soybeans, and possibly little or no stimulation for C4 crops that
include maize and sorghum," said Stephen P. Long, a U. of I. plant
biologist and crop scientist.

FACE technology, such as the SoyFACE project at Illinois, allows
researchers to grow crops in open-air fields, with elevated levels of
carbon dioxide simulating the composition of the atmosphere projected
for the year 2050. SoyFACE has added a unique element by introducing
surface-level ozone, which also is rising. Ozone is toxic to plants.
SoyFACE is the first facility in the world to test both the effects of
future ozone and CO2 levels on crops in the open air.

Older, closed-condition studies occurred in greenhouses, controlled
environmental chambers and transparent field chambers, in which carbon
dioxide or ozone were easily retained and controlled.

Such tests provided projections for maize, rice, sorghum, soybean and
wheat - the world's most important crops in terms of global grain
production. By 2050 carbon dioxide levels may be about 1.5 times greater
than the current 380 parts per million, while daytime ozone levels
during the growing season could peak on average at 80 parts per billion
(now 60 parts per billion).

Older studies, as reviewed by the Intergovernmental Panel on Climate
Change, suggest that increased soil temperature and decreased soil
moisture, which would reduce crop yields, likely will be offset in C3
crops by the fertilization effect of rising CO2, primarily because CO2
increases photosynthesis and decreases crop water use.

Although more than 340 independent chamber studies have been analyzed to
project yields under rising CO2 levels, most plants grown in enclosures
can differ greatly from those grown in farm fields, Long said. FACE has
been the only technology that has tested effects in real-world
situations, and, to date, for each crop tested yields have been "well
below (about half) the value predicted from chambers," the authors
reported. The results encompassed grain yield, total biomass and effects
on photosynthesis.

The FACE data came from experimental wheat and sorghum fields at
Maricopa, Ariz.; grasslands at Eschikon, Switzerland; managed pasture at
Bulls, New Zealand; rice at Shizukuishi, Japan; and soybean and corn
crops at Illinois. In three key production measures, involving four
crops, the authors wrote, just one of 12 factors scrutinized is not
lower than chamber equivalents, Long said.

"The FACE experiments clearly show that much lower CO2 fertilization
factors should be used in model projections of future yields," the
researchers said. They also called for research to examine simultaneous
changes in CO2, O3, temperature and soil moisture."