THE FATE OF FARMING - The Climate Casino - page 85

CO 2 fertilization will interact with other stresses. However, experts like
Paul Waggoner, former director of the Connecticut Agricultural Experi-
ment Station and one of the pioneers on the effects of climate change
on agriculture, concludes that CO 2 fertilization could offset many of the
adverse effects of warmer and drier conditions.
A second important mitigating factor is adaptation, which is an-
other term to describe what we call management. Adaptation refers to
the adjustments that human or natural systems make in response to
changes in environmental conditions. Many of the studies that project
large declines in yields make limited allowance for adaptation. So un-
derstanding adaptation is important in this context, as elsewhere.
Adaptations occur on multiple levels. Some occur without human
assistance, such as when a species migrates to a friendlier climatic zone
in response to a changing climate. In agriculture we usually consider
the most important adaptations to be those undertaken by farmers.
Short-run adaptations include adjusting sowing and harvesting dates,
changing seeds and crops, and modifying production techniques such
as fertilizer application, tillage methods, grain drying, and other fi eld
operations.
In the longer run, farmers can move into new areas and abandon
infertile ones, plant new varieties of seeds that are drought and heat
resistant, and shift land to other uses. One of the most important adap-
tations is the use of more water-effi cient irrigation systems. 9
Studies of agriculture have looked extensively at impacts with and
without adaptation, and it is useful to examine a specifi c example.
Figure 14 shows the synthesis of studies of the effect of climate change on
the yields of wheat in low-latitude regions (such as India and Brazil). 10
The horizontal axis shows the change in average temperature in low-
latitude regions, while the vertical axis shows the change in the yield
(production per acre) of wheat production. The dashed lower line shows
the summary impact of warming without CO 2 fertilization or adapta-
tion. The upper solid line shows the summary impact of warming with
CO 2 fertilization and some other adaptations.
In the case without adaptation or CO 2 fertilization, yields begin to
decline after local warming of around 1 1 ⁄ 2 °C. However, the story is quite