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problematic with emerging evidence that the widely used herbicide glyphosate
could become less effective under elevated CO
2
(Ziska et
al., 1999) and the
possibility that the number of days suitable for spraying operations could reduce
significantly (
Figure 6.5
, Howden et
al
.
, 2007a).
Food consumption and its implications
In addition to the threats to food production arising from climate change, there
are likely to be significant upward pressures on food consumption arising from
population growth and, especially in Asia, the increased consumption of protein
derived from grain-fed livestock, linked to food preference changes and net
income. Australia's population is increasing rapidly, with recent years experi-
encing record population growth resulting from increased net immigration and
a policy-driven reversal of the decline in its birth rate (ABS, 2008; 2012). The
net effect of climate change on food supply, coupled with increased aggregate
demand, is that Australia's food surpluses will likely shrink and potentially
become negative in some years under certain climate change and population
scenarios: especially scenarios involving warming of 4°C or more.
These projections are not inconsistent with, and seem to exacerbate, existing
trends. For example, over 30 years, Australia's average annual wheat export has
dropped from 80 per cent to 65 per cent of production due largely to increased
domestic demand (ABARES, 2012). However, individual years can vary dramat-
ically from the long-term trends, particularly during years with above-average
production - for example, during 2011-12, wheat exports rose to 82 per cent
of gross production as a result of above-average production and stable domestic
consumption rates, leading to a significant increase in product available for
export in that year. The long-term trend, however, shows there are likely to
be significant periods with more restricted crop exports, and this may give rise
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Cropp ing period
Cropping period
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Figure 6.5
Frequency of days per month unsuitable for spraying for Emerald
(Queensland) and Kellerberrin (Western Australia) for the historical
baseline, 2030 and for 2070
Source: Howden et al., 2007
