Monitoring Agricultural Drought in Australia - Monitoring and Predicting Agricultural Drought: A Global Study - page 370

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the El Niño/Southern Oscillation (ENSO) phenomenon (http://www.bom
.gov.au/climate/ahead/soirain.shtml). The Interdecadal Pacific Oscillation
(IPO) also contributes to the rainfall variability at annual and decadal
scales and modulates ENSO impacts on rainfall (Power et al., 1999).
The current geographic boundaries of agricultural production (figure
29.1) were reached in the late 19th century, and the entire agricultural
region has experienced drought, in some form, over the past 100 years.
Protracted dry periods occurred during the period from late 1890s to 1902
in eastern Australia, during the mid to late 1920s and 1930s over most
of the continent, during the 1940s in eastern Australia, during the 1960s
over central and eastern Australia, and during 1991-95 in parts of central
and northeastern Australia. During these low rainfall periods, not every
year was extremely dry, but rainfall in most years was below the long-term
median, and there were often runs of severe drought years. Many, but not
all, droughts were associated with El Niño events (http://www.bom.gov.au/
climate/ahead/soirain.shtml; chapter 3). Droughts have been more preva-
lent when the IPO was positive, that is, from 1896 to 1909, from 1922
to 1945, and from 1979 to 1998. During the periods when the IPO was
negative, La Niña events have tended to be associated with wet conditions.
During these times, Australia has largely been drought free.
Despite Australia's arid or semiarid climate, agriculture (including crop-
ping and grazing) is practiced on 60% of Australia's land area of approx-
imately 463 million ha (figure 29.1). Extensive grazing by beef cattle and
sheep occupies approximately 90% of the agricultural land. The remaining
agricultural land is equally distributed between intensively grazed, sown
pastures and crops. Wheat is Australia's major crop, having the broadest
geographic range (figure 29.1), and it contributes an average of 25% of to-
tal agricultural production. Only a small proportion (0.5%) of Australia's
sown pastures and crops are irrigated, but these regions are nonetheless
important in terms of their contribution to the value of agricultural pro-
duction.
Despite the high variation in annual rainfall, cropping and grazing are
geared toward years with normal rainfall, with some contingency for
drought years as discussed later in this chapter. For this reason, the entire
agricultural region (figure 29.1) is drought prone. In some cases, expec-
tations of climate are biased by years with above-average rainfall, leaving
a particular enterprise even more drought prone. Sensitivity to drought is
therefore dependent more on an individual's experience, expectations, and
management than on geographic location.

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Im pacts of Drought
Drought has severe impacts on agricultural production in Australia, par-
ticularly at local levels, affecting the financial and social well-being of farm
families and local communities. Declining terms of trade and rising debt
levels have eroded the capacity of rural families and communities to cope