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According to Fitzgerald, the research being
carried out by PICCC, referred to as Australian
Grains Free Air CO2 Enrichment (AGFACE), is
also being done in a drier environment than
anywhere previously studied.
“The experiments are what we refer to as
‘fully replicated’ – repeated four times and
statistically verified for accuracy and precision,”
says Fitzgerald. “This allows us to compare our
current growing conditions of 400 parts per
million (ppm) CO2 with eCO2 conditions of
550 ppm – the atmospheric CO2 concentration
level anticipated for 2050.”
The experiments involve injecting CO2 into
the atmosphere around plants via a series of
horizontal rings that are raised as the crops
grow, and the process is computer-controlled to
maintain a CO2 concentration level of 550 ppm.
“We’re observing around a 25–30% increase
in yields under eCO2 conditions for wheat,
field peas, canola and lentils in Australia,”
This increased yield is due to more efficient
photosynthesis and because eCO2 improves the
plant’s water-use efficiency.
With atmospheric CO2 levels rising, less water
will be required to produce the same amount
of grain. Fitzgerald estimates about a 30%
increase in water efficiency for crops grown
under eCO2 conditions.
But nutritional content suffers. “In terms of
grain quality, we see a decrease in protein
concentration in cereal grains,” says Fitzgerald.
The reduction is due to a decrease in the level
of nitrogen (N2) in the grain, which occurs
because the plant is less efficient at drawing
N2 from the soil.
The same reduction in protein concentration
is not observed in legumes, however, because of
the action of rhizobia – soil bacteria in the roots
of legumes that fix N2 and provide an alternative
mechanism for making N2 available.
“We are seeing a 1–14% decrease in
grain-protein concentration [for eCO2 levels]
and a decrease in bread quality,” says Fitzgerald.
“This is due to the reduction in protein and
because changes in the protein composition affect
qualities such as elasticity and loaf volume. There
is also a decrease of 5–10% in micronutrients such
as iron and zinc.”
This micronutrient deficiency, referred to as
“hidden hunger”, is a major health concern,
particularly in developing countries, according
to the International Food Research Policy
Institute’s 2014 Global Hunger Index: The
challenge of hidden hunger.
There could also be health implications for
Australians. As the protein content of grains
diminishes, carbohydrate levels increase, leading
to food with higher caloric content and less
nutritional value, potentially exacerbating the
current obesity epidemic.
The corollary from the work being undertaken
by Fitzgerald is that in a future CO2-enriched
world, there will be more food but it will be less
nutritious. “We see an increase in crop growth
on one hand, but a reduction in crop quality on
the other,” says Fitzgerald.
Fitzgerald says more research into nitrogen-
uptake mechanisms in plants is required in order
to develop crops that, when grown in eCO2
environments, can capitalise on increased plant
growth while maintaining N2, and protein, levels.
For now, though, while an eCO2 atmosphere
may be good for plants, it might not be so good
While higher CO2 levels boost
crop yields, there is also a link
between eCO2 and an increase
in viruses that affect crop growth.
Scientists at the Department
of Economic Development, Jobs,
Transport and Resources have been
researching the impact of elevated
CO2 levels on plant vector-borne
diseases, and they have observed
an increase of 30% in the severity
of the Barley Yellow Dwarf Virus
Spread by aphids, BYDV is a
common plant virus that affects
wheat, barley and oats, and
causes yield losses of up to 50%.
“It’s a really underexplored
area,” says Dr Jo Luck, director
of research, education and training
at the Plant Biosecurity Cooperative
Research Centre. “We know quite a
lot about the effects of drought and
increasing temperatures on crops,
but we don’t know much about how
the increase in temperature and
eCO2 will affect pests and diseases.
“There is a tension between
higher yields from eCO2 and the
impacts on growth from pests and
diseases. It’s important we consider
this in research when we’re looking
at food security.”
“We see an increase in crop growth on
one hand, but a reduction in crop quality
on the other.”
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