Geoscience Reference
In-Depth Information
locations of those regions and the magnitudes of their food
deficits and to study the effectiveness of adaptive responses,
including the use of genetic resources to global climate change.
As a part of the US Environmental Protection Agency proj-
ect, crop scientists estimated that the yield changes at over
100 sites in over 20 countries under common climate change
scenarios using compatible crop growth models. The crop
models were those developed by the International Benchmark
Sites Network for Agrotechnology Transfer (IBSNAT, 1990).
Preliminary national production changes for wheat based on
the IBSNAT crop model have been chronicled (Rosenzweig
et al., 1991). These results show that the climate change sce-
narios without the physiological effects of CO
2
cause a decrease
in the estimated national production, while the physiological
effects of CO
2
mitigate the negative effects. The UKMO cli-
mate change scenario (mean global warming of 5.2°C) gener-
ally causes the largest production declines, while the GFDL
and GISS (4.0°C and 4.2°C mean global warming, respectively)
production changes are more moderate. When embedded in a
global agricultural food trade model, the basic linked system,
(Fischer et al., 1994), the production change estimates based
on the IBSNAT crop model results will allow for projection of
potential impacts on food prices, shifts in comparative advan-
tage and altered patterns of global trade flows for a suite of
global climate change, population growth and policy scenarios.
15.5
Direct effect
There have been a number of studies in India to understand the
nature and magnitude of crop yield at selected sites under ele-
vated atmospheric CO
2
and associated climatic change (Abrol
et al., 1991; Sinha and Swaminathan, 1991; Aggarwal and
Sinha, 1993; Aggarwal and Kalra, 1994; Gangadhar Rao and
Sinha, 1994; Mathauda and Mavi, 1994; Gangadhar Rao et al.,
1995; Mohandass et al., 1995; Lal et al., 1998, 1999; Francis
1999; Saseendran et al., 2000, Rathore et al., 2001; Aggarwal
and Mall, 2002; Mall and Aggarwal, 2002; Aggarwal, 2003;
Attri and Rathore, 2003, Mall et al., 2004, 2006).
An increase in the CO
2
level may result in an increase in
food production. It is predicted that a twofold increase in CO
2
will lead to a 10-15% increase in dry matter production pro-
vided all other factors remain constant. As C
3
plants respond
much more to an increase in the CO
2
level than do C
4
plants,
crops in Central and Northern Europe and similar latitudes
