Geoscience Reference
In-Depth Information
productivity and some greenhouse own-
ers actually purchase CO
2
to increase plant
growth.
In an exchange before the House Sub-
committee on Energy and Environment
in March 2009, the British climate change
contrarian Christopher Walter Monckton,
3rd Viscount Monckton of Brenchley, ar-
gued that “carbon dioxide is a plant food,”
which prompted Representative John
Shimkus to ask: “So if we decrease the use
of carbon dioxide, are we not taking away
plant food from the atmosphere?”
As an elementary school student, you
most likely learned that plants use CO
2
during photosynthesis. Increased CO
2
has
been shown to accelerate the rate of photo-
synthesis. Simply put, the pro-CO
2
argu-
ment is that since plants need CO
2
, they
will benefit from increased levels of it in
the atmosphere. This is essentially the ar-
gument being put forward by CO
2
boost-
ers, but it is a gross oversimplification. For
one thing, anticipated climate change does
not involve only increased CO
2,
and studies
have shown that increased CO
2
may actu-
ally negate some of the agricultural bene-
fits of global warming.
M. Rebecca Shaw, a botanist at the Car-
negie Institution, and her colleagues found
that anticipated climate changes of warm-
ing, increased precipitation, and nitrogen
deposition, alone or in combination, in-
creased net primary production in the third
year of ecosystem-scale manipulations
in annual grasslands in California. While
increased CO
2
by itself also improved net
primary production, “across all multifactor
manipulations, elevated carbon dioxide
suppressed root allocation, decreasing the
positive effects of increased temperature,
precipitation, and nitrogen deposition on
net primary production.”
Further, an article by the freelance writer
Ned Stafford in the journal
Nature
in 2007
cited several studies suggesting that more
carbon dioxide will result in less nutrition
in plants, in part because of decreased in-
take of nitrogen, calcium, and zinc. Clenton
Owensby and other researchers at Kansas
State also found that elevated CO
2
levels re-
sulted in less nutritious and less digestible
grass for cattle, suggesting that future ru-
minants may gain less weight even if they
eat more grass in a CO
2
- enriched world.
They also noted that insects appear to in-
crease consumption as nutrition decreases
in an elevated CO
2
setting.
The Argentine scientist Jorge Zavala per-
formed an open field study involving the
levels of CO
2
expected to be in the atmo-
sphere by the year 2050 and found that soy-
beans produced less jasmonic acid, a natu-
ral defense to insect pests, allowing adult
insects to feast on the plants, live longer,
and produce more offspring.
Increased levels of carbon dioxide may
contribute to warming in another manner
apart from the greenhouse effect. Long Cao
and Ken Caldeira, researchers at the Carn-
egie Institution, have found that increased
CO
2
negates the cooling effect of trees and
contributes to warming. Plants give off wa-
ter through tiny pores in their leaves in a
