Co2 Crops Not Tops

  • Theories that crops, such as the corn in Illinois, will benefit from increases in CO2 might not be as good as predicted. (Photo by Scott Bauer, courtesy of the USDA Agricultural Research Service)

Carbon dioxide emissions from our cars and factories are the number one
cause of global warming. Scientists have long theorized that more of
the gas in the atmosphere could actually help farmers grow bigger
plants. But new research from America’s Breadbasket is challenging
that assumption. David Sommerstein reports:

Transcript

Carbon dioxide emissions from our cars and factories are the number one
cause of global warming. Scientists have long theorized that more of
the gas in the atmosphere could actually help farmers grow bigger
plants. But new research from America’s Breadbasket is challenging
that assumption. David Sommerstein reports:


Lin Warfel’s a fourth generation farmer in east-central Illinois. His
fields are flat and endless, the soil chunky and black and just about
the best in the world. An Interstate highway groans on one side of his
cornfield:


“In my career, early on, there was no Interstate past my farm.”


As traffic increased over the years, Warfel noticed a strange
phenomenon. The crops closer to the Interstate grew bigger than those
further away:


“They respond to the carbon dioxide. They can stay greener longer than
plants out into the field.”


OK… so, here’s a high school biology reminder: carbon dioxide, along
with water and sun, is an ingredient in photosynthesis, which makes
plants grow.


Increasing carbon dioxide in the atmosphere is also the biggest cause
of global warming. So scientists thought, huh, more carbon dioxide in
the atmosphere, bigger crops. They even coined a term: the “carbon
dioxide fertilization effect:”


“The effects of CO2 on crop yields are fairly well-understood.”


The Department of Energy’s Jeff Amthor has studied this stuff since the
1980s:


“We would expect that by the year 2050, that the increase in CO2 alone
would probably increase yields by about 10 to 15% in soybean, wheat and
rice relative to today’s yield, with nothing else changing.”


Other things are changing, like hotter temperatures and more drought.
But the predominant thinking has been that the increased carbon dioxide
will moderate those negative factors, maybe even outweigh them. A
recent study by the American Economic Review concluded U.S. agriculture
profits will grow by more than a billion dollars over the next century,
due to global warming. Most of this is based on experiments done in
controlled, greenhouse conditions, but new research done in real fields
is challenging the assumptions:


“Where you’re standing is what we refer to as our global change
research facility on the south farms of the University of Illinois.”


That’s biologist Steve Long. He runs what’s called the SoyFACE project
at the University of Illinois in Champaign-Urbana. Here, Long can
actually pipe carbon dioxide gas out to the fields, and grow real crops
in an atmosphere of the future.


Long strolls out to one of 16 test plots and stop at a white pipe
sticking out of the ground:


“This is one of the pipes where the carbon dioxide actually comes up
and then it will go out into the field here.”


The carbon dioxide pipes circle a plot about the size of a tennis
court. They release the gas over the crops. Computers monitor the air
to keep the concentrations steady:


“And the current atmospheric concentration of carbon dioxide is about
380 parts per million. We’re raising that to the level which is
expected for the year 2050, which is about 550 parts per million.”


Long has grown the crops of 2050 for 5 years now. His results
shocked him. The plants did grow bigger. They survived longer
into the fall, but the yields were 50% lower than expected. And
pests thrived. The Western corn rootworm, for example, laid
twice as many eggs:


“Japanese beetle, which eats quite a lot of the leaves of soybeans, do
twice as well under these elevated CO2 conditions. They live longer. They
produce many more young. The yield increases we’ve seen could start to be
counteracted by those increased pest problems.”


Long’s results found supporters and critics when published in
Science magazine last summer. Some researchers say extra CO2
could hurt agriculture more than it helps because weeds become more
aggressive.


The Department of Energy’s Jeff Amthor co-wrote a paper challenging the
interpretation of Long’s data. But he agrees more work needs to be
done in real-life conditions:


“The bigger questions that are now before us are the interactions of CO2 with
warming and change in precip, changes in weed communities, changes in
insect communities, changes in disease outbreak. There are a lot more
questions there than there are answers.”


Amthor says what’s at stake is our future food supply.


For The Environment Report, I’m David Sommerstein.

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