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World Crops Could Decline 16 Pct Due to Warming

Date: 13-Sep-07
Country: US
Author: Deborah Zabarenko, Environment Correspondent

India, Pakistan, most of Africa and most of Latin America
would be hit hardest, said economist William Cline, the study's
author. The United States, most of Europe, Russia and Canada
would probably see agricultural gains if climate change
continues on its current course, the study found.

Overall, the world's agricultural productivity was forecast
to decline by between 3 percent and 16 percent by 2080,
according to the study published by the Washington-based Center
for Global Development and the Peterson Institute for
International Economics.

Among developed countries, Australia's outlook was bleakest
with predicted declines in crop yields ranging between 16
percent and 27 percent. In the developing world, fast-growing
India's declines were forecast between 29 percent and 38
percent while Sudan and Senegal both had predicted crop
declines of more than 50 percent, essentially a collapse of
agricultural productivity.

The wide range between the low and high end of the forecast
depends on how much carbon dioxide emissions actually spur some
crops, Cline said. Plants absorb carbon dioxide, a
climate-warming greenhouse gas emitted by coal-fired power
plants, petroleum-fueled vehicles and some natural processes.

Some analysts maintain that global warming could actually
be a boon to crops, making the impact of human-caused climate
change negligible. They cite laboratory studies that have shown
potential gains in crop yields of up to 30 percent when carbon
dioxide emissions were increased.

CARBON FERTILIZATION

Cline disputed these contentions, saying that similar tests
performed in farm fields have shown gains to be around 15
percent. He said the boost from so-called carbon fertilization
tends to flatten out.

For corn, there is already so much carbon dioxide in the
atmosphere that putting more of this gas in the air would not
help increase yields, Cline said. Wheat, rice and soybeans are
continuing to benefit from increased carbon dioxide emissions
but that improvement is likely to taper off, he said.

"It turns out that global yields for the major cereal
(crops) have in fact slowed down, that the Green Revolution has
slowed down," Cline said, referring to the global technological
transformation of agriculture between the 1940s and 1960s.

"There's already a sign that there is fatigue in the Green
Revolution," he said, noting that the average annual growth in
yields in the 1960s and 1970s was 2.6 percent per year, but by
the 1980s and 1990s it had slowed to 1.8 percent.

"The problem is that you need the technical change to keep
up with demand for food," Cline said. "I estimate that the
global demand for food after you take into account higher
population, as well as higher incomes, would about triple from
now to late in the century."

Northern countries such as parts of the United States,
Russia and Canada would have longer growing seasons due to
global warming. But Cline said the world probably could not
rely on increased crop yields in those areas.

"By the end of the century, they're probably going to be
earning so much money from their energy exports that their
exchange rates are going to be very strong," he said.

These strong currencies would make it prohibitively
expensive for most other countries to buy Russian or Canadian
agricultural goods.

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