Livermore, California
March 23, 2007
Increasing temperatures in
California during the next 45 years could negatively affect the
amount of almonds, walnuts, oranges, avocados and table grapes
that Americans put on their tables.
According to new research in the journal Agricultural and Forest
Meteorology, production losses in some of California’s most
popular crops could be as high as 40 percent by mid-century.
In the study, researchers from
Lawrence
Livermore National Laboratory evaluated the impact of
climate change on six major perennial crops in California: wine
grapes, almonds, table grapes, oranges, walnuts and avocados.
Each of these crops is typically planted only once every 25-40
years, so that climate can change considerably in the lifetime
of individual vines or trees.
Using more than 20 climate models, the authors assessed the
response of these crops to projected changes in temperature (an
increase of 2 degrees to 4 degrees Celsius) and precipitation.
“Climate change should be an important factor in selecting
perennial varieties and deciding whether and where they should
be planted in California,” said David Lobell, the lead author of
the paper who collaborated with scientists at the Carnegie
Institution, Stanford University and the University of
California, Merced. “This study indicates that warmer
temperatures will tend to reduce yields of these crops in their
current locations,” he said.
While these particular crops could be grown in cooler regions,
it takes close to three years for orchards and vineyards to
mature to a point where they are producing harvestable fruit. In
addition, other regions are often unsuitable for reasons other
than climate, such as poor soils.
The modeling shows that wine grapes will undergo very small
changes in yield over the next century because of climate
change. But almonds, table grapes, oranges, walnuts and avocados
show moderate to substantial yield declines. For example,
avocado crops are expected to yield 40 percent less than current
harvests. The expected yield of almonds, table grapes, oranges
and walnuts decreases by as much as 20 percent.
“The impacts are based on the assumption that farmers do not
move to other locations with more favorable climates,” Lobell
said. “With long-lived perennial plants, moving to another
region within California is somewhat limited.”
The research did not include the effects of an increase in CO2
in the atmosphere or farming modifications due to increasing
temperatures and less rainfall.
The models did, however, take into account for a variety of
mechanisms that can influence yields in a changing climate, such
as plant physiological processes and climate-related influence
of pests, pathogens and air pollution.
The research was funded in part by the Department of Energy’s
Office of Science, Biological and Environmental Research
Program.
Founded in 1952, Lawrence Livermore National Laboratory has a
mission to ensure national security and apply science and
technology to the important issues of our time. Lawrence
Livermore National Laboratory is managed by the University of
California for the U.S. Department of Energy’s National Nuclear
Security Administration. |
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