Toll Of Climate Change On World Food Supply Could Be Worse Than Thought
Pastor Dale Morgan
Toll Of Climate Change On World Food Supply Could Be Worse Than Thought*
In order to keep pace with population growth, current production of
grain-from which humans derive two-thirds of their protein-will probably
have to double, to 4 billion tons a years before 2100. Studies in the
past 10 years suggest that mounting levels of carbon dioxide in the
air-believed to be the basis of human-caused climate change-may
initially bolster the photosynthetic rate of many plants, and, along
with new farming techniques, possibly add to some crop yields.
Between now and mid-century, higher temperatures in northerly latitudes
will probably also expand lands available for farming, and bring longer
growing seasons. However, these gains likely will be canceled by
agricultural declines in the tropics, where even modest 1- to 2-degree
rises are expected to evaporate rainfall and push staple crops over
their survival thresholds.
by Staff Writers
Washington DC (SPX) Dec 04, 2007
Global agriculture, already predicted to be stressed by climate change
in coming decades, could go into steep, unanticipated declines in some
regions due to complications that scientists have so far inadequately
considered, say three new scientific reports.
The authors say that progressive changes predicted to stem from 1- to
5-degree C temperature rises in coming decades fail to account for
seasonal extremes of heat, drought or rain, multiplier effects of
spreading diseases or weeds, and other ecological upsets. All are
believed more likely in the future. Coauthored by leading researchers
from Europe, North America and Australia, they appear in this week's
issue of the Proceedings of the National Academy of Sciences (PNAS).
"Many people assume that we will never have a problem with food
production on a global scale. But there is a strong potential for
negative surprises," said Francesco Tubiello, a physicist and
agricultural expert at the NASA/Goddard Institute of Space Studies who
coauthored all three papers. Goddard is a member of Columbia
University's Earth Institute.
In order to keep pace with population growth, current production of
grain-from which humans derive two-thirds of their protein-will probably
have to double, to 4 billion tons a years before 2100. Studies in the
past 10 years suggest that mounting levels of carbon dioxide in the
air-believed to be the basis of human-caused climate change-may
initially bolster the photosynthetic rate of many plants, and, along
with new farming techniques, possibly add to some crop yields.
Between now and mid-century, higher temperatures in northerly latitudes
will probably also expand lands available for farming, and bring longer
growing seasons.
However, these gains likely will be canceled by agricultural declines in
the tropics, where even modest 1- to 2-degree rises are expected to
evaporate rainfall and push staple crops over their survival thresholds.
Existing research estimates that developing countries may lose 135
million hectares (334 million acres) of prime farm land in the next 50
years. After mid-century, continuing temperature rises-5 degrees C or
more by then--are expected to start adversely affecting northern crops
as well, tipping the whole world into a danger zone.
The authors of the PNAS studies say that much of the previous work is
oversimplified, and as a consequence, the potential for bigger, more
rapid problems remains largely unexplored. "The projections show a
smooth curve, but a smooth curve has never happened in human history,"
said Tubiello.
"Things happen suddenly, and then you can't respond to them." For
instance, extreme-weather events of all kinds, including heat waves or
sudden big storms, could easily wipe out crops on vast scales if they
occur for even a few days during critical germination or flowering
times. Tubiello says this is already happening on smaller scales. During
a heat wave in the summer of 2003, temperatures in Italy soared 6
degrees C over their long-term mean, and the corn yield in the rich Po
valley dropped a record 36%.
Nearly all the world's pastures are rain-fed; in Africa, droughts in the
1980s and 1990s wiped out 20% to 60% of some nations' herds. Such events
on larger scales could arise with little or no warning in the near
future, the authors suggest.
Higher temperatures may also prompt outbreaks of weeds and pests, and
affect plant or animal physiology-factors also left out of most
projections. One of the new PNAS studies, "Crop and Pasture Response to
Climate Change," says that more recent modeling suggests cattle ticks
and bluetongue (a viral disease of sheep and cattle) will move outward
from the tropics to areas such as southern Australia.
Other new models suggest that higher temperatures will limit the ability
of modern dairy-cow breeds to convert feed into milk, and lead to
declines in livestock fertility and longevity. As temperatures rise in
northerly latitudes, the ability of crop pests to survive winters is
expected to improve, enabling them to attack spring crops in regions
where they were previously kept at bay during this vulnerable time.
The authors say that farmers may temporarily mitigate some effects of
changing climate by moving toward adaptations now. Adaptations already
being considered or set up include regional climate-forecasting systems
that enable farmers to switch to different crops or change the timing of
plantings; introduction of new varieties or species that can withstand
anticipated conditions; and improved flood-mitigation and water-storage
facilities.
One of the PNAS studies, "Adapting Agriculture to Climate Change," says
that such adaptations might help tropical farmers cut damages wrought by
rises of 1.5 to 3 degrees, and temperate-region farmers, damages from 1-
to 2-degree rises. This would buy a few decades of time for nations to
agree on ways to slow or reverse the warming itself. "After that, all
the bets are off," said Tubiello.