Farm Table says:
What is the problem?
The wheat-belt of Western Australia is the most important wheat-growing region in Australia. Winter rainfall in this region has declined by up to 20 % during recent decades (IOCI 2002; Ludwig et al. 2009; Smith et al. 2000) relative to the long-term average. Based on various global circulation models (GCMs), further reductions in winter rainfall in the region are predicted. In addition, there is predicted to be an increase in temperatures and atmospheric CO2 concentration.
What did the research involve?
Climate data were downloaded from the patch point dataset on the Bureau of Meteorology Silo website. Historic climate trend and future climate scenario 168 Climatic Change (2013) 118:167–181 maps were downloaded from the Bureau of Meteorology website. Fifty rainfall series covering the period 2001–2050 were generated stochastically using a downscaling technique that relates changes in atmospheric predictors from a global circulation model to multi-site daily rainfall supplied by Dr. S. Charles. The stochastic nature of the generated series accounts for the variability in the timing of daily rainfall sequences resulting from natural climate variability and long-term climate change. Rainfall data were generated for the Katanning location in the wheat-belt of Western Australia under an A2 climate-change scenario.
What were the key findings?
Rainfall changes since 1900 have been heterogeneous across Australia. The Western Australian wheat-belt has had a 20 % rainfall decline over the past 110 years, more than any other wheat-growing region in Australia. Losses in other parts of the wheat-belt have been approximately 10 % in parts of the South Australia and 8 % in parts of Queensland, while in other wheat-growing regions in eastern Australia there has been no change or even some increase in rainfall during this time Examining rainfall changes in more detail at a specific location, data shows growing season rainfall since 1889 for Morawa, a location in the northern wheat-belt of Western Australia. There has been a decline in the average from about 300 mm at the beginning of the last century to about 230 mm currently. Importantly, the decline in rainfall is mainly caused by a reduction in the frequency of very wet seasons, i.e. seasons with rainfall above 350 mm, but there has not been an increase in the frequency or severity of very dry seasons. This pattern is replicated across most parts of the Western Australian wheat-belt.
In the wheat-belt of Western Australia, there is little or no need or scope in the short term for farmers to adapt to long-term climate change. Measurable climate change has occurred during the 20th century, but when the within-season timing of change is considered and combined with the benefits of higher CO2 concentration, the overall impact on wheat yields has been minimal. Further, current practices that are being promoted to farmers as appropriate tools for adaptation to climate change are either already considered standard ‘best practices’ for reasons other than climate change, or else are not currently widely adoptable due to their adverse economic performance when implemented at large scale. In terms of public policy for adaptation to climate change in the region, the greatest benefits are likely to be generated by research and development. We highlight the need for research to develop improved agricultural technologies, such as new crop cultivars or new types of perennial plants that are tolerant of predicted climatic changes.