Climate Change Damaging
Nutritional Value of Crops

Reuters 10/9/02
Global warming boosts crops, cuts nutrients - study

WASHINGTON - Global warming could increase rice, soybean and wheat
production in some areas, but the greater plant growth could also hurt the
nutritional value of the crops, Ohio researchers said.

The nutritional quality declines because while the plants produce more seeds
with higher levels of carbon dioxide, the seeds themselves contain less
nitrogen, said Peter Curtis, a professor of evolution, ecology and
organismal biology at Ohio State University.

Carbon dioxide is a heat-trapping greenhouse gas linked to automobile
exhaust and other fossil fuels. Some scientists expect the level of carbon
dioxide in the atmosphere to significantly rise over the next few decades.

A gradual increase in the earth's temperature is feared to have many harmful
effects, including melting glaciers, raising sea levels and destroying some
wildlife habitats.

"If you're looking for a positive spin on rising carbon dioxide levels, it's
that agricultural production in some areas is bound to increase," Curtis
said. "Crops have higher yields when more carbon dioxide is available, even
if growing conditions aren't perfect."

But while there may be more food, it may not be as nutritious, Curtis said.

"The quality of the food produced by the plant decreases, so you've got to
eat more of it to get the same benefits," Curtis said. "Under the rising
carbon dioxide scenario, livestock - and humans - would have to increase
their intake of plants to compensate for the loss."

Curtis and other researchers pulled together data from 159 similar studies
from the past two decades to determine the effects of climate change on
plant reproduction. They analyzed the ways plants respond to carbon dioxide
through flowers, fruits, fruit weight, number of seeds, and the plant's
capacity to reproduce.

Individual crops varied in their response to higher carbon dioxide levels.

Rice was the most responsive with its seed production increasing an average
of 42 percent. Soybeans showed a 20 percent increase in seed, followed by
wheat with 15 percent, and corn with 5 percent, Curtis said.

Even though seed size increased, the amount of nitrogen in the seeds didn't.
Nitrogen levels fell by an average of 14 percent across all plants except
cultivated legumes, such as peas and soybeans, the research showed.

For example, the total number of seeds in wheat and barley plants increased
by 15 percent, but the amount of nitrogen in the seeds declined by 20

"That's bad news," Curtis said. "Nitrogen is important for building protein
in humans and animals. If anything, plant biologists want to boost the
levels of nitrogen in crops."

Story Date: 9/10/2002

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