Agriculture Reference
In-Depth Information
P r e D i C t i n g t h e e f f e C t s of f C L i m a t e C h a n g e o n a g r i C u L t u r a L P r of D u C t i v i t y
Simulation models driven by historical, current, and future climate scenarios have
been essential tools for testing hypotheses concerning the possible impacts of cli-
mate change on agricultural production and water resources (Rosenberg, 1992). As
an example, Izaurralde et al. (2003) applied results of the HadCM2 GCM (Hadley
Climate Model 2 General Circulation Model) and the EPIC (Environmental Policy
Integrated Climate) agroecosystem model to evaluate climate change impacts on
crop yields and ecosystem processes. EPIC was implemented to run the main crops
(with and without irrigation) grown in the United States under current (1961-1990)
and two future climates (2025-2034, 2090-2095). The simulation runs were imple-
mented at two CO 2 concentrations (365 and 560 ppmv). The simulation results
revealed a high spatial dependence driven mainly by regional changes in tempera-
ture and precipitation. For example, wheat yields in the Northern Plains region are
expected to remain unchanged in the two future periods but benefit by the presence
of the CO 2 fertilization effect (Figure 16.3). In the warmer Southern Plains, the pro-
jected increases in temperature would reduce yields, but losses would be partially
compensated by the CO 2 effect. This effect appears less expressed in maize than in
wheat crops. Water use efficiency is reduced with warming in both crops, but again,
the CO 2 fertilization effect, if present, would attenuate this decrease.
Despite many advances during the last four decades toward an improved under-
standing of the possible impacts of climate change on agricultural productivity and
ecosystem function, much remains to be done to reduce the uncertainties arising
from experimental and simulation results. For example, a recent meta-analysis of
FACE experiments (Ainsworth and Long, 2005; Long et al., 2006) suggested that
grain yield increases under elevated CO 2 were lower than those of previous enclo-
sure (non-FACE) studies. However, a reinterpretation of crop yields reported across
FACE and non-FACE data sets found the responses to be rather similar (Tubiello et
al., 2007). The relevant aspect of this discussion in relation to this chapter resides
in our ability to predict the influence of climate change on global food supply. As
this section has shown, future crop production will depend on the dynamics and
interaction of many climatic factors, such as precipitation, temperature, CO 2 , and
tropospheric O 3 , among others.
the Role of AgRIcultuRe In clImAte
chAnge mItIgAtIon And AdAPtAtIon
D e f i n i t i of n s of f m i t i g a t i of n a n D a D a P t a t i of n
What can be done to prepare agriculture for climate change? One action could be
that of mitigation , that is, use current or future agricultural technologies to counter-
act emissions of greenhouse gases and thus contribute to their stabilization in the
atmosphere. Another action is that of adaptation , which is designed to lessen adverse
impacts of climate change on human and natural systems. In this context, the main
objective is to reduce the vulnerability of agriculture to the harm that may be caused
by climate change.
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